Chapter 1111 Final Final

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CHAPTER 1

INTRODUCTION AND LITERATURE SURVEY

1.1 Scope and Purpose of Work :

The metals Mn, Fe, Cu, and Zn, and the non-metal Se are considered traceelements(TE) because of their essentiality and very limited quantity in humans.

The biological activitiesof Cu, Fe, Mn, and Se are strongly associated with the

presence of unpaired electrons thatallow their participation in redox reactions. Inbiological systems these metals are mostlybound to proteins, forming

metalloproteins. Many of the metals in metalloproteins are partof enzymaticsystems, have structural and storage functions, or use the protein to be transported

to their target site in the organism. In humans Mn, Fe, Cu, Zn, and Se accomplishdecisivefunctions to maintain human health. Deficiency in any of these TE leads

to undesirablepathological conditions that can be prevented or reversed by

adequate supplementation. Insufficiently nourished persons, supplementation

should be carefully controlled, given the toxiceffects ascribed to TE when presentin quantities exceeding those required for accomplishingtheir biological functions.

The dietary reference intakes provided by national regulatory agenciesare guides

to define intake, supplementation and toxicity of Mn, Fe, Cu, Zn, and Se, aswellother elements considered micronutrients for humans.

1.1.1 Relevance, essentiality and toxicity of trace elements in human life

1.1.1a. Elements, trace elements and micronutrients

Four elements (oxygen, carbon, hydrogen, and nitrogen) account for 96% of

living matter. About 50 of the known elements occur in measurable

concentrations inthe living systems. In humans and other mammals, 23 elementshave known physiologicalactivities. From these elements, 11 can be classified as

trace elements (TE)because of their essentiality and very limited quantity in

humans. Out of these 11 TE,eight are in the period 4 of the Periodic Table(Fig.1.1), suggesting an optimal relationshipof nuclei size/electron availability ofthe elements in this period to interactwith organic molecules present in biological

systems.


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Fig. 1.1 Periodic table

TE include, at least, the transitionmetals vanadium, chromium, manganese (Mn),

iron (Fe), cobalt, copper (Cu),zinc (Zn), and molybdenum; and the non-metalsselenium (Se), fluorine, and iodine.All of these belong to the category of

micronutrients, which are needed by the humanbody in very small quantities

(generally less than 100 mg/day), as opposed to elementsconsidered

macronutrients, such as sodium, calcium, magnesium, potassium,chlorine, etc.,which are required in larger quantities.TE are essential components of biological

structures, but at the same time theycan be toxic at concentrations beyond those

necessary for their biological functions.

In addition, the toxicity can be extended to other non-essential elements of very

similaratomic characteristics that can mimic the reactivity of a TE. To deal withthisessentiality/toxicity duality, biological systems have developed the ability to

recognizea metal, and deliver it to the target without allowing the metal to

participatein toxic reactions [1]. Proteins are primarily responsible for suchrecognitionand transport, and most of the associations of TE with other

biomoleculeslead to undesirable chemical modifications of these molecules.


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1.1.1b. Metals as trace elements

Metals are generally solids at room temperature, they have high electricalconductivity,luster, and malleability, and they can lose electrons and form

positive ions.According to their position in the Periodic Table, metals includealkali metals, alkalineearth metals, transition metals, and rare earth metals. Non-

metals, exist primarilyin the gaseous state at room temperature (selenium and

sulfur are solids), theyhave poor electrical conductivity, and they tend to win

electrons and form negativeions. In this review the focus will be on four transitionmetals (Mn, Fe, Cu, Zn) andone non-metal (Se).

Cations of Cu, Fe, Mn, and anions of Se have unpaired electrons that allowtheirparticipation in redox reactions involving mostly one electron loss

(oxidation) orgain (reduction). The unpaired electrons also allow the chemical

classification ofmost metals as free radicals [2]. Several of the biologicaleffects,mostly toxic, of these elements can be explained by their capacity tocatalyze the

initiation of free radical reactions or the decomposition of peroxidesand other

unstable molecules, allowing the propagation of deleterious free radicalreactions.

Following the recognition of the participation of free radicals (reactiveoxygenspecies, oxygen radicals, oxidants) in a number of biological processes

andpatholo-gical states, metals (free or bound to chelators or proteins) were

identifiedas participants in most of the free radical reactions, acting as pro-oxidantor antioxidantentities [3]. The role the metal plays depends on itschemical

structure (iron can act as pro-oxidant and antioxidant; selenium is usuallyan

antioxidant), as well as on the molecule that is chelating the metal [2]. Zn, as with

other group 12 elements, has no unpaired electronswhen in the state Zn2+,preventing its participation in redox reactions. Nevertheless,Zn has been

recognized to act as an antioxidant by replacing metals that are active incatalyzing

free radical reactions, such as Fe [4].

Other transition metals that are TE of significance for human physiology are:

(1) cobalt, a component of cobalamine, or vitamin B12 [5](2) molybdenum, an electron transfer agent in enzymes such as xanthineoxidase

and sulphite reductase [6] and

(3) chromium andvanadium, which are biochemically related to glucose and lipidmetabolism, butspecific functions for which are uncertain [7, 8, 9 ].

In biological systems, metal TE are mostly conjugated or bound toproteinsforming metalloproteins, or to smaller molecules, such as phosphates,


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phytates,polyphenols and other chelating compounds. Most of the metals inmetalloproteinsare part of enzymatic systems, have structural functions, or use the

protein to be transported to their target site in the organism. In enzymes, the

metals participatein catalytic processes as: (1) constituents of enzyme active sites;(2) stabilizersof enzyme tertiary or quaternary structure; or (3) associates in

forming weakbondingcomplexes with the substrate that can contribute to

orienting the substratefor reactions, or stabilizing charged transition states. Asconstituents of activesites, metal cations with unpaired electrons mediate

oxidationreduction (redox)processes by reversible changes in their oxidation

state, transferring or receivingelectrons to or from the substrate and co-factor. For

example, human superoxidedismutases reduce one superoxide anion to hydrogenperoxide, and oxidize asecond superoxide anion to generate molecular oxygen by

means of either Cu orMn present in the active site of the cytosolic or

mitochondrial enzyme,respectively. The presence of metals bound to lipids,

nucleic acids, and carbohydratesis well documented, but the biochemicalfunctions of the metals presentin these molecules is unclear, beyond their

deleterious actions through oxidantreactions.

1.1.1c. Manganese, iron, copper, zinc, selenium , calcium, chromium, cobalt,

magnesium, molebdenum, potassium, phosphorus, and sodium in humans

The main functions, dietary sources, presence, and potential for toxicity are

summarized for Cu, Zn, Fe, Se, and Mn, Ca, Cr, Co, Mg, Mo, P, K, S . Based on

the functions for these TE, on their dietary origin, and on the diseases and

pathological situations developed because of TE deficiency or toxicity, anappropriate intake of TE is a relevant aspect of a healthy diet. The presence of TE

in foods is often determined by the availability of metals in the soil. Thus, withina geographical region with soils deprived of a TE, its population is at risk and TE

supplementation becomes necessary. Such supplementation has been

implemented or is being evaluated in several places around the world by adding

the appropriate TE to basic foods (milk, flour, etc.) [10, 11] .Also,supplementation becomes necessary in several disease treatments, e.g. anemic

conditions in kidney dialysis [12], and physiological conditions, e.g. extensive

blood loss during menstruation [13].

Unfortunately, in recent years the avalanche of uncontrolled supplementation with

TE has put some TE on the border of toxicity in several populations. Thus, it is a

crucial priority to define the requirements for TE, based on essentiality and healthpromotion, and the limits for toxicity. Many countries and regions have defined

the requirements and limits of supplementation for TE, e.g. Japan [14], UK [15],

Although these requirements and toxicity reference values can slightly differ for

some micronutrients, in general the values are rather homogeneous.


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Manganese

Mn is associated with bone development, and with amino acid, lipid, and

carbohydrate metabolism. Mn is found in different enzymes, e.g. mitocondrial Mnsuperoxide dismutase, glutamine synthetase, arginase, and activates several

hydrolases, transferases and carboxylases. Mn is transported in the body by

transferrin and by macroglobulins and albumin [16, 17] Sources of dietary Mninclude grain, rice, tea, and nuts. Mn is toxic in excess; in brain it can cause a

Parkinson-type syndrome [18]

IronFound in four classes of proteins: Fe-heme proteins (e.g. hemoglobin (2/3 body

iron), myoglobin, catalase, cytochromes); Fesulfur enzymes (e.g. aconitase,

fumarate reductase); proteins for Fe storage and transport (transferrin, lactoferrin,ferritin, hemosiderin), and other Fe-containing or Fe-activated enzymes (e.g.

NADH dehydrogenase, succinate dehydrogenase, alcohol dehydrogenase,

cyclooxygenases). Total iron intake ranges from 14.4 to 20.2 mg/day [19]. SerumFe is about 1.3 mg/L, mostly bound to transferrin. Iron content in an adult man is

about 4 g, decreasing to about 3 g in menstruating women. Fe deficiency causes

anemia. /Molecular Sources of heme Fe (15% of consumption) are hemoglobin

and myoglobin from animals. Sources of nonheme Fe are cereals, seeds ofleguminous plants, fruits, vegetables, and dairy products.

One of the most serious forms of Fe overload is acute Fe poisoning. Chronic Feintoxication occurs frequently associated to genetic and metabolic diseases,

repeated blood transfusions, or excessive intake [3].

Copper

In humans Cu is necessary for the development of connective tissue, nerve

coverings, and bone. Cu also participates in both Fe and energy metabolism. Cu

acts as a reductant in the enzymes superoxide dismutase, cytochrome oxidase,

lysil oxidase, dopamine hydroxylase, of and several other oxidases that reducemolecular oxygen. It is transported in the organism by the protein ceruloplasmin.

There is about Medicine 80 mg of Cu in the adult body (highest concentrations in

liver and brain) and median intake of Cu ranges between 1.0 and 1.6 mg/day inadults (US data).


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Good sources of dietary Cu are liver and other organ meats, oysters, nuts, seeds,dark chocolate, and whole grains. Cu deficiency in humans is rare, but when it

occurs leads to normocytic, hypochromic anemia, leucopenia and neuropenia, and

osteoporosis in children [20]. Chronic Cu toxicity is rare in humans, and mostlyassociated with liver damage. Acute Cu intoxication leads to gastrointestinal

effects characterized by abdominal pain, cramps, nausea, diarrhea, and vomiting.

Zinc

Zn is involved in the activity of about 100 enzymes, e.g. RNA polymerase,carbonic anhydrase, CuZn superoxide dismutase, angiotensin I converting

enzyme. Also it is present in Zn-fingers associated with DNA. Zn is mainly

transported by ceruloplasmin. There are 23 g of Zn present in the human body

(second to Fe in body content) and about 1 mg/L in Zn deficiency is common inunderdeveloped countries and is mainly associated with malnutrition, affecting

the immune system, wound healing, the senses of taste and smell, and impairing

DNA synthesis. Zn seems to support normal growth and development inpregnancy, childhood, and adolescence.

Zn is found in red meat and poultry, beans, nuts, seafood (oysters are extremelyrich in Zn), whole grains, fortified breakfast cereals, and dairy products. Zn

toxicity has been seen in both acute and chronic forms. Intakes of 150450 mg of

Zn per day have been associated with low Cu status, altered Fe function, reduced

immune function, and reduced levels of HDL [21].

Selinium

Se is incorporated into proteins to make selenoproteins, which are important

antioxidant enzymes. Se is found in glutathione peroxidase, thioredoxins, andselenoprotein P.

Se is obtained from grains, cereals, red meats and seafood. Some nuts are alsosources of selenium (Brazil nuts may contain as much as 20 mg of Se per g).

Human Se deficiency is rare in the US but is seen in other countries, most notably

China, where soil concentration of selenium is low. There is evidence that Sedeficiency may contribute to a form of heart disease, of hypothyroidism, and a

weakened immune system [22] There is also evidence that Se deficiency

Medicine does not usually cause illness by itself. Rather, it can make the body

more susceptible to illnesses caused by other nutritional, biochemical or


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infectious stresses [23]. High blood levels of Se (>1 mg/L) can result in selenosis.Symptoms of selenosis include gastrointestinal upsets, hair loss, white blotchy

nails, garlic breath odor, fatigue, irritability, and mild nerve damage.

Se toxicity is rare in the US, being the few reported cases being associated with

accidental exposure

Calcium

Essential for developing and maintaining healthy bones and teeth Assists in blood

clotting. muscle contraction, nerve transmission, oxygen transport. cellular

secretion of fluids and enzyme activity Optimal intake helps reduce risk of

osteoporosis.

Chromium

Aids in glucose metabolism and helps regulate blood sugar by potentiating insulin

and serving as a component of glucose tolerance factor.

Colbalt

Promotes the formulation of red blood cells and and serves as a component of thevitamin B-12

Lodine

Needed by the thyroid hormone to support metabolism

Magnesium

Activates over 100 enzymes and helps nerves and muscles function. Helpsmaintain the integrity of cell membranes and stabilizes the cell electrically

Critical for proper heart function

Molybdenum


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Contributes to normal growth and development Key component in many enzymesystems including enzymes involved in detoxification.

Phosphorous

Works with calcium to develop and maintain strong bones and teeth. Enhancesuse of other nutrients Key role in cell membrane integrity and intercellular

communication Critical for proper energy processing in the body

Potassium

Regulates heartbeat, maintains fluid balance and helps muscles contract.

Sulfur

Needed for structure of most protein, including muscles and hair. Critical role in

liver detoxification. Important functions in antioxidant nutrients and oxygen

handling Role in growth.

There are even more benefits than these, so it is certainly easy to see that minerals

play an important role in health.

1.1.1.d. Beyond metal deficiency but before toxicity: limits for

supplementation

For many years foods were accepted as the source of all the nutrientsrequired to accomplish the physiological functions needed for development,

growth, health, and reproduction. During that time, little or no attention was

directed on the effects of nutrients on the development of diseases different than

those caused by the nutrient deficiency. Based on the increased knowledge of thebiological mechanisms ruling life, as well as the increase in life expectancy and

the resultant increased incidence of chronic and degenerative diseases, the

concept that increasing the intake of certain nutrients may influence the onset anddevelopment of the disease becomes a public concern. It has been claimed that

poor diet and physical inactivity were responsible for about 1/6 of the deaths in

the USA in 2000 [25].Associations for cancer, diabetes and cardiovascular disease


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with diet have prompted the consumption of fiber, fatty acids, phytochemicals,and trace elements [26].

As a result of this gain in knowledge, in the last 20 years there has

been a not always desirable explosion in the availability and consumption of

supplements aimed to prevent the onset of disease. Furthermore, the passiveacceptation of the concept that more is better . . . has led to unjustified high

supplementation with many TE [27]. For TE, given the absence of metabolization

of the metal or Nonmetal atoms, it is possible to establish clear separations among

essentially, healthbenefits and toxicity. Other important variables that should beconsidered when the levels of TE are increased in the body are the effects genetic

and individual differences in the targeted population, life-style, nutra-genetic

interactions, and other individual factors that can determine the effects of the

nutrient on the disease.

Thus, we have seen how the trace elements that accomplish functionsessential to maintaining human health, there deficiency leads to undesirable

pathological conditions that can be prevented or reversed by adequate

supplementation but, supplementation should be carefully controlled,since

toxicity can take place to that very TE when present at levels that exceed thoserequired for accomplishing their biological functions.

1.1.1e Mineral Absorption

Every person absorbs minerals in a slightly different way--- a processcalled biochemical individuality. According to Ruth L. Pike and Myrtle L. Brown

in their book Nutrition: Integrated Approach. Whatever the nutritional potential

of a food, its contribution is nonexistent if it does not pass the test of absorption.

Those nutrients that have not been transferred through the intestinal mucosal cellto enter the circulation have. for all nutritional intent and purpose, never been

eaten.

The variety of nutrients from the organism's environment that have

been made available by absorption must be transported through the circulatory

system to the aqueous microenvironment of the cells Then. they serve theirultimate purpose -- participation in the metabolic activities in the cells on which

the life of the total organism depends.


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The absorption of minerals is dependent on many different factors.not the least of which is age as well as adequacy of stomach acid output, balance

of bowel flora, presence or lack of intestinal illness- and parasites, and amount of

dietary fiber intake.

Aging increases the risk of gastric atrophy, a condition that commonlyis associated with a decreased secretion of hydrochloric acid in the stomach. The

problem becomes that as a level of hydrochloric acid output decreases the bodys

ability to absorb minerals from the food-bound form diminishes. This inability to

adequately absorb minerals contributes to age-associated degeneration. Hence, theform a mineral takes is crucial. since the less dependent It is on hydrochloric acid

to be absorbed, the more likely it will be able to be utilized by the body.

Gastric atrophy or conditions such as achlorhydria (lack of stomach

acid) or hypochlorhydria (inadequate stomach acid) can also impair the bodys

absorption of important minerals. Achlorhydria has been found in children asyoung as five or six years of age. Hypochlorhydria, however, is more com-manly

seen after age 35. It is estimated that between 15-35 percent of adults over age 60

have some degree of gastric atrophy, including hypochlorhydria.

Some acid-dependent minerals that require adequate stomach acid to

enhance intraluminal absorption (the transferof nutrients to the circulatory

system) in the small intestine include, Cr, Mn, Cu, Mo, Fe, Se, Mg, Zn.

1.1.1f Nonessential Minerals / Contaminants

Table 1.1 gives us a view of essential minerals, non essential minerals and

contaminants whose presence increases the toxic behaviour of TE.

Table 1.1

Minerals, Trace Minerals And Mineral Contaminants

Essential

Minerals:

Essential Trace and

Minerals:

Nonessential

Contaminant Minerals:Calcium Chromium+ Aluminum

Chloride* Copper+ Arsenic (in abundance)

Magnesium Cobalt Barium

Phosphorus Fluorine+ Beryllium

Potassium* Iodine Cadmium

Sodium* Iron Lead


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Sulfur* Manganese Lithium

Molybdenum Mercury

Selenium Rubidium

Vanadium+ StrontiumZinc

NSN REFERENCES

* No RDAs set for these minerals Only estimated requirements are

established for chloride, potassium and sodium No estimates as yet establishedfor sulfur.

+ No RDAs as yet established for these minerals Estimated safe and adequate

intakes are established for chromium, copper, chlorine, manganese and

molybdenum There is no estimate as yet established for vanadiumNOTE: Several trace minerals that may be essential but have not yet been proven

to be include minute amounts of arsenic, boron, nickel, silicon and tin.

The absorption and efficient use of mineral in the body can also be

affected by excessive levels of nonessential mineral contaminants such as

aluminum, arsenic, cadmium, lead and mercury. These toxic minerals can have anunbalancing effect on the bodys cells (see Table 1.2). Cadmium, for example,

an air pollutant from cigarette smoke and industrial emissions and a by-product of

population growth, is experimentally known to cause hypertension, cancer andimmune disorders. Cadmium acts like a classical stress agent. It has also been

implicated in learning disabilities. Unlike lead, which has a short half-life in

human tissue of from 30 to 100 days, cadmium has a half-life of between 10- 30years.

While it is known that free cadmium is very toxic, it has also beenfound to greatly increase the toxicity of other agents. Cadmium has a unique

capacity to form a close bond with chloride compounds such as the chlorinated

pesticide lindane. When the two are combined, they alter liver metabolism and

tissue levels of lindane double. Cadmium accumulates in cells that are the mostmalignant; in prostate cancer, for example. there is a linear correlation between

the grade of malignancy and cadmium content. On the positive side, little

cadmium is absorbed orally unless there are nutrient deficiencies.

Recent research indicates that adequate dietary intake of essential

minerals and trace minerals may prevent and reduce affects of poisoning byenvironmental pollutants and enhance the ability to work and learn. They can


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protect the body from the effects of toxic minerals. Minerals that protect againstcadmium and other nonessential mineral contaminants are listed in Table 1.2.

Table 1.2 Mineral Contaminants Guide

Mineral Contaminate Body Part Affected Protective Nutrient

Aluminum Stomach, bones, brain Possibly magnesium

None other known

Arsenic Cells (cellular metabolism) Selenium, lodine,

calcium, zinc,

vitamin C, sulfuramino acids

Cadmium Renal cortex of the kidney, heart, blood

vessels to the brain appetite and smell centerof the brain, every known process in the

development of cancer

Zinc, calcium,

vitamin C, sulfurammo acids

Lead Bones, liver, kidney, pancreas, heart, brain,nervous system

Zinc, iron, calcium,vitamin C, vitamin

E, sulfur amino

acids

Mercury Nervous system, appetite and pain centers

of the brain, immune system, cell

membranes

Selenium, vitamin C.

pectin, sulfur amino

acids

(NFM 38) NFMs Nutrition Science News l December 1995

Besides optimum levels and kinds of minerals to cope with toxicity,

mineral requirements are affected by two other factors-- disease and drug-nutrientinteraction Physical illness can raise demands for many trace elements. for

example, the need for magnesium increases in heart disease and eating disorders.

And the demand for some minerals, such as zinc, increases under

psychological, stress. Drug-nutrient interaction can also create deficiencies and

imbalances of minerals at the cellular level For example, the absorption of iron

from the gut can be reduced by antacids and tetracycline. Magnesium and zinc arehyper-excreted by those receiving oral diuretics, nephrotoxic drugs,

penicillamine, or antacids containing aluminum hydroxide.

1.1.1fOptimal Mineral Levels


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Considering the importance of minerals to good health, establishingoptimal mineral levels -- i.e. an update on the Recommended Dietary Allowances

(RDAs), released in their 10th edition in 1989 -- is an urgent need. Recent

analyses of data of nutrient and supplement intake in the United States conductedby the U.S. National Institutes of Health and other government agencies indicate

that the vast majority of people in both affluent and emerging industrialized

countries do not reach even 75 percent of the RDAs for numerous trace minerals.

It is valuable to remember, however. that the realization of

importance of trace minerals to human health is a recent discovery For example.only fifteen years ago, every textbook taught that the trace element boron was

nonessential to all mammals, including man However, today, it is believed to be

so important to human health that numerous scientists are preparing to petition the

government to recognize boron as a trace mineral essential to human health.

Minerals and trace minerals do not exist by themselves but inrelationships to one another Too much of one element can lead to imbalances in

others, resulting in disease rather than the absence of disease. Factors such as diet,

absorption ability, toxicities and drug-nutrient interactions play a role in

maintaining a balance of trace elements in the body.

Table 1.2 Mineral Contaminants Guide

Mineral Contaminate Body Part Affected Protective Nutrient

Aluminum Stomach, bones, brain Possibly magnesium

None other known

Arsenic Cells (cellular metabolism) Selenium, lodine,

calcium, zinc,vitamin C, sulfur

amino acids

Cadmium Renal cortex of the kidney, heart, blood

vessels to the brain appetite and smell center

of the brain, every known process in the

development of cancer

Zinc, calcium,

vitamin C, sulfur

ammo acids

Lead Bones, liver, kidney, pancreas, heart, brain,nervous system

Zinc, iron, calcium,vitamin C, vitamin

E, sulfur amino

acids

Mercury Nervous system, appetite and pain centers

of the brain, immune system, cell

Selenium, vitamin C.

pectin, sulfur amino


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membranes acids

(NFM 38) NFMs Nutrition Science News l December 1995

1.1.2 Environmental PollutionA Concern

Thus, we see that on one side trace elements are very essential for our

life and on the other side heavy metals resulting from industrial pollution makeour life hazardous and toxicate these Trace elements.

Pollution is the introduction of contaminants into the naturalenvironment that cause adverse change[28]. Pollution can take the form of

chemical or energy , such as noise, heat or light. Pollutant, the components of

pollution, can be either foreign substances/energies or naturally occurringcontaminants. Pollution is often classed as point source or non point source

pollution.

Air pollution has always accompanied civilizations. Pollution startedfrom the prehistoric times when man created the first fires. According to a 1983

article in the journal Science, "soot found on ceilings of prehistoric caves provides

ample evidence of the high levels of pollution that was associated with inadequateventilation of open fires.[29]" The forging of metals appears to be a key turning

point in the creation of significant air pollution levels outside the home. Core

samples of glaciers in Greenland indicate increases in pollution associated with

Greek, Roman and Chinese metal production[30], but at that time the pollutionwas comparatively less and could be handled by nature. But , as civilization

proceeded

It was the industrial revolution that gave birth to environmental

pollution as we know it today. The emergence of great factories and consumption

of immense quantities ofcoal and otherfossil fuels gave rise to unprecedented airpollution and the large volume of industrial chemical discharges added to the

growing load of untreated human waste. Chicago and Cincinnati were the first

two American cities to enact laws ensuring cleaner air in 1881. Other cities

followed around the country until early in the 20th century, when the short livedOffice of Air Pollution was created under the Department of the Interior. Extreme

smog events were experienced by the cities ofLos Angeles and Donora,

Pennsylvania in the late 1940s, serving as another public reminder [31].
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Polluting industrial units: On May 26, 2011 the Haryana StatePollution Control Board has ordered closure of 639 polluting industrial units in

2010-11 and directed the highly polluting industries to set up continuous online

monitoring stations to ensure compliance of standards of air emissions. TheGovernment has launched prosecution against 151 polluting units in the Special

Environment Courts in Faridabad and Kurukshetra, and made 9,239 units install

pollution control devices.

Brick kilns are noxious sources of pollution: Indias 100,000 brick

kilns are noxious sources of pollution, particularly soot, and working them meansa life that is always nasty, frequently brutish and often short. But on top of this

social evil is an environmental one.

The exhaust from the kilns mixes with diesel emissions and other

fumes to form a vast brown smog, known as an atmospheric brown cloud, which

is up to 3km thick and thousands of kilometres long. Two of its main ingredients,the small carbon particles which the soot is composed of, and ozone, a triatomic

form of oxygen, are important contributors to the greenhouse effect, and thus to

climate change. Among other negative effects, the cloud is therefore thought to be

accelerating the retreat of Himalayan glaciers, which are found at a similaraltitiude [32].

1.1.2 a. Modern Awareness

Pollution became a popular issue after World War II, due to

radioactive fallout from atomic warfare and testing. Then a non-nuclear event,

The Great Smog of 1952 in London, killed at least 4000 people [33]. This

prompted some of the first major modern environmental legislation, The CleanAir Act of 1956.

Pollution began to draw major public attention in the United Statesbetween the mid-1950s and early 1970s, when Congress passed theNoise Control

Act, the Clean Air Act, the Clean Water Act and the National Environmental

Policy Act[34].

Severe incidents of pollution helped increase

consciousness. PCB dumping in the Hudson Riverresulted in a ban by
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the EPA on consumption of its fish in 1974. Long-term dioxincontaminationat Love Canal starting in 1947 became a national news story in 1978 and led to

the Superfund legislation of 1980. Legal proceedings in the 1990s helped bring to

lighthexavalent chromium releases in Californiathe champions of whosevictims became famous. The pollution of industrial land gave rise to the

name brownfield, a term now common in city planning.

The development of nuclear science introduced radioactive

contamination, which can remain lethally radioactive for hundreds of thousands

of years. Lake Karachay, named by theWorldwatch Institute as the "most pollutedspot" on earth, served as a disposal site for the Soviet Union throughout the 1950s

and 1960s. Second place may go to the area of Chelyabinsk U.S.S.R. (see

reference below) as the "Most polluted place on the planet".

Some of the more common soil contaminants are chlorinated

hydrocarbons (CFH), heavy metals (such as chromium, cadmiumfound inrechargeable batteries, and leadfound in lead paint, aviation fuel and still in some

countries, gasoline), MTBE, zinc, arsenic andbenzene. In 2001 a series of press

reports culminating in a book called Fateful Harvest unveiled a widespread

practice of recycling industrial byproducts into fertilizer, resulting in thecontamination of the soil with various metals.

Mercury has been linked to developmental deficits in childrenand neurologic symptoms. Older people are majorly exposed to diseases induced

by air pollution. Those with heart or lung disorders are under additional risk.Children and infants are also at serious risk. Lead and otherheavy metals have

been shown to cause neurological problems. Chemical and radioactive substances

can cause cancerand as well as birth defects.

Environment Pollution has been found to be present widely in the environment.

There are a number of effects of this:

Biomagnification describes situations where toxins (such as heavy metals)may pass through trophic levels, becoming exponentially more

concentrated in the process.

Carbon dioxide emissions cause ocean acidification, the ongoing decrease

in the pH of the Earth's oceans as CO2 becomes dissolved.
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The emission ofgreenhouse gases leads to global warming which affectsecosystems in many ways.

Invasive species can out compete native species and reduce biodiversity.Invasive plants can contribute debris and biomolecules (allelopathy) that

can alter soil and chemical compositions of an environment, oftenreducing native species competitiveness.

Nitrogen oxides are removed from the air by rain and fertilise land whichcan change the species composition of ecosystems.

Smog and haze can reduce the amount of sunlight received by plants tocarry out photosynthesis and leads to the production oftropospheric

ozone which damages plants.

Soil can become infertile and unsuitable for plants. This will affectotherorganisms in the food web.

Sulfur dioxide and nitrogen oxides can cause acid rain which lowersthe pH value of soil.

1.1.2 bEnvironmental health information

The Toxicology and Environmental Health Information Program(TEHIP)[35] at the United States National Library of Medicine (NLM) maintains

a comprehensive toxicology and environmental health web site that includes

access to resources produced by TEHIP and by other government agencies andorganizations. This web site includes links to databases, bibliographies, tutorials,

and other scientific and consumer-oriented resources. TEHIP also is responsible

for the Toxicology Data Network (TOXNET) [36]an integrated system of

toxicology and environmental health databases that are available free of charge onthe web.

Environmental contamination and exposure to heavy metals such as

mercury cadmium and lead and many others is serious growing problem throughout the world. Human exposure to heavy metals has risen dramatically in the last

50 years as result of an exponential increase in the use of heavy metals inindustrial processes and products.
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In today's industrial society, there is no escaping exposure to toxicchemicals and metals. In the United states tons of toxic industrial waste are mixed

with liquid agricultural fertilizers and dispersed across America's farmlands. This

controversial practice", which is presently legal in the US, has been reported innine states. While the spreading of arsenic, lead, cadmium, nickel, mercury and

uranium on soil that is utilised to produce food for human consumption is a

political and economic issue. The potential for adverse health effects is welldocumented. In general, heavy metals (HM) are systematic toxins with specific

neurotoxic, nephrotoxic, fetotoxic and teratogenic effects. Heavy metals can

directly influence behaviour by impairing mental and neurological function,

influencing neurotransmitter production and utilization and altering numerousmetabolic body processes. System in which toxic metal elements can induce

impairment and dysfunction include the blood and cardiovascular, eliminative

pathways (colon, liver, kidneys, skin), endocrine (hormonal), energy production

pathways, enzymatic, gastrointestinal, immune , nervous, (central and peripheral),reproductive and urinary.

Many occupation involve daily heavy metal exposure, over 50

professions entail exposure to mercury alone. The greatest source of mercury in

the biosphere is currently of human origin Mercury is considered to be global

pollutant capable of spreading far beyond its source area. Methyl mercury isextremely toxic form of mercury that biomagnifies in aquatic food chains. It is a

potent neurotoxin and the easiest form for animals to store in their tissues. It binds

to proteins and easily crosses cell membranes, including the blood-brain barrier

and the placenta. Solutions to the complex problem of mercury pollution havebeen impeded by conflicting informaiton on the sources, transport and

accumulation of mercury in the environment.

1.1.2 c Indias Position in pollution

India is among the world's worst performers when it comes to the

overall environment. We rank 125 of 132 countries. Even Pakistan and

Bangladesh are less polluted than we are. A study released earlier this year by the

environmental research centres of Columbia and Yale showed that India was atthe bottom of the heap when it came to air pollution.

1.1.2 c1 The most polluted places in India.

The most polluted cities in India ,As many as 51 Indian cities have

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topping the list. An environment and forest ministry report, released onSeptember 14, 2007 has identified 51 cities that do not meet the prescribed

Respirable Particulate Matter (RSPM) levels, specified under the National

Ambient Air Quality Standards (NAAQS). In 2005, an EnvironmentalSustainability Index (ESI) placed India at 101st position among 146 countries.

Taking a cue from the finding, the Central Pollution Control Board

(CPCB) formulated NAAQS and checked the air quality, which led to the

revelation about air quality in leading cities.

According to the report, Gobindgarh in Punjab is the most polluted

city, and Ludhiana, Raipur and Lucknow hold the next three positions. Faridabad

on the outskirt of Delhi is the 10th most polluted city, followed by Agra, the cityof Taj Mahal. Ahmedabad is placed 12th, Indore 16th, Delhi 22nd, Kolkata 25th,

Mumbai 40th, Hyderabad 44th and Bangalore stands at 46th in the list. The Orissa

town of Angul, home to National Aluminium Company (NALCO), is the 50thpolluted city of the country.

This information was given by Shri Jairam Ramesh in Lok Sabha onAugust 4, 2010.

Vapi in Gujarat and Sukinda in Orrisa is among the worlds top 10

most polluted places, according to the Blacksmith Institute, a New York-based

nonprofit group. Vapi returns to top, is again most polluted in country accordingto Central Pollution Control Boards interim report on May 21, 2012.

Vapi : Potentially affected people: 71,000 -Pollutants: Chemicals and heavymetals due to its Industrial estates.

Sukinda: Potentially affected people: 2,600,000. -Pollutants:Hexavalent chromium due to its Chromite mines.

Bangalore holds the title of being the asthma capital of the country.Air pollution in the city continues to rise due to vehicular emissions and dust from

construction activities, according to the "Environment Report Card of Bangalore

2012". It says the number of vehicles on the city roads have exceeded 3.7 millionand there has been a consistent increase in the number vehicles at an average of

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Chennai: Exhaust from vehicles, dust from construction debris,industrial waste, burning of municipal and garden waste are all on the rise in the

city. So are respiratory diseases, including asthma. At least six of the 10 top

causes of death are related to respiratory disease, says Dr D Ranganathan, director(in-charge), Institute of Thoracic Medicine.

Mumbai: Not only are levels of Suspended Particulate Matter above

permissible limits in Mumbai, but the worst pollutant after vehicular emissions

has grown at an alarming rate. The levels of Respirable Suspended Particulate

Matter (RSPM), or dust, in Mumbais air have continued to increase over the pastthree years.

The air pollution in Mumbai is so high that Mumbai authorities havepurchased 42,000 litres of perfume to spray on the citys enormous waste dumps

at Deonar and Mulund landfill sites after people living near the landfill sites

complained of the stench. The Deonar landfill site, one of Indias largest, was firstused by the British in 1927. Today, the festering pile covers more than 120

hectares and is eight storeys high.

Bhopal: Bhopal gas tragedy was the greatest industrial disaster in

the world that took place at a Union Carbide pesticide plant in the Indian city of

Bhopal, Madhya Pradesh. At midnight on 3 December 1984, the plant

accidentally released methyl isocyanate (MIC) gas, exposing more than 500,000people to MIC and other chemicals. The first official immediate death toll was

2,259. The government of Madhya Pradesh has confirmed a total of 3,787 deathsrelated to the gas release Others estimate 8,000-10,000 died within 72 hours and

25,000 have since died from gas-related diseases, making it the deadliest man-

made environmental disaster in history.

The effects of air pollution are obvious: rice crop yields in southern

India are falling as brown clouds block out more and more sunlight.The brilliant

white of the famous Taj Mahal is slowly fading to a sickly yellow. In theTajmahal Case a very strong step was taken by Supreme Court to save the

Tajmahal being polluted by fumes and more than 200 factories were closed

down.

Birds and species affected: Studies conducted by the high altitude

zoology field station of the Zoological Survey of India (ZSI) based in Solan town
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of Himachal Pradesh have recorded a drastic fall in butterfly numbers in thewestern Himalayas, famous for their biodiversity. The population of 50 percent of

the 288 species recorded in the western Himalayas, Himachal Pradesh and

Jammu and Kashmir, have declined more than half in just 10 years according toWorld Environment Day 2012.

1.1.2 d Mahatma Ghandhi on Environmental pollution

Mahatma Gandhi had said that nature has enough to satisfy

everyones need but has not enough to satisfy mans greed. Sadly our ever-expanding greed has put us in such precarious situation. Will we realise it? The

policy of industrialisation had helped rich to become richer and poor become

poorer. The disparity has widened. It is the democratic system followed in the

country which has forced our policy-makers to think of growth for all. That iswhy we are hearing plans for inclusive growth. Industrialisation is not without

price. All these have a direct bearing on environmental pollution leading to

climatic change. We are all witness to the deleterious effects of climate change.The whole world is now anxious to repair the damage.

1.1.2 e Poverty is the biggest polluter

During his meet with editors on July 01, 2011 Prime Minister

Manmohan Singh remarked that "poverty is the biggest polluter" and India needs

to achieve a balance between environment and development - industrialization.Indira Gandhi, the former prime minister announced at the United Nations first

environmental conference, in 1972, that Poverty is the biggest polluter. Those

sentiments were echoed by the prime minister, but Manmohan Singh haveforgotten that Indira Gandhi created the country's environmental governance

structure during her tenure as prime minister. It was Indira Gandhi's intervention

that supported the call stop a hydro-electric project in Silent Valley, Kerala -

saving an ecosystem rich in biodiversity. It was Indira Gandhi's concern thatMussorie, the queen of the hills, was being stripped naked by limestone mining

that led the Environment Ministry to take action.

The poor live in the places polluted by the rich, they do not cause the

pollution. And they live in polluted places because they are displaced from theirhomes in rural areas where they had lived sustainable for millennia. India's

economy of sustenance is being uprooted by means of violence in order to enable

POSCO to export our iron-ore and steel. In June, 2011 it was the women and

children of Govindpur, Dinkia and Nuagaon in Orissa who laid down in front of
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the police in the scorching sun in an effort to stop the land grab. To farmers,tribles who form the bulk of protesters as POSCO agitation against land

acquisition land is far more economically essential than a job of a petty unskilled

worker in a factory.

1.1.2 fRegulation and monitoring

To protect the environment from the adverse effects of pollution,many nations worldwide have enacted legislation to regulate various types of

pollution as well as to mitigate the adverse effects of pollution.

1.1.2 f2 Pollution control

Pollution control is a term used in environmental management. It

means the control ofemissions and effluents into air, water or soil. Without

pollution control, the waste products from consumption, heating, agriculture,

mining, manufacturing, transportation and other human activities, whether theyaccumulate or disperse, will degrade theenvironment. In the hierarchy of

controls, pollution prevention and waste minimization are more desirable than

pollution control. In the field ofland development, low impact development is a

similar technique for the prevention ofurban runoff.

1.1.2 f3 Practices :recycling

reusing

reducing

mitigatingpreventing

compost

1.1.2 f4 Pollution control devices

Dust collection systems

BaghousesCyclones

Electrostatic precipitators

Scrubbers

Baffle spray scrubber

Cyclonic spray scrubber

Ejector venturi scrubber
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Mechanically aided scrubber

Spray tower

Wet scrubber

Sewage treatmentSedimentation (Primary treatment)

Activated sludge biotreaters (Secondary treatment; also used for industrialwastewater)

Aerated lagoons

Constructed wetlands (also used for urban runoff)

Industrial wastewater treatment

API oil-water separators

Biofilters

Dissolved air flotation (DAF)

Powdered activated carbon treatment

Ultrafiltration

Vapor recovery systems

Phytoremediation

1.1.2 g Perspectives

The earliest precursor of pollution generated by life forms would have

been a natural function of their existence. The attendant consequences on viabilityand population levels fell within the sphere ofnatural selection. These would have

included the demise of a population locally or ultimately, species extinction.

Processes that were untenable would have resulted in a new balance brought

about by changes and adaptations. At the extremes, for any form of life,consideration of pollution is superseded by that of survival.

For humankind, the factor of technology is a distinguishing and

critical consideration, both as an enabler and an additional source of byproducts.

Short of survival, human concerns include the range from quality of life to health

hazards. Since science holds experimental demonstration to be definitive, moderntreatment of toxicity or environmental harm involves defining a level at which an

effect is observable. Common examples of fields where practical measurement is

crucial include automobile emissions control, industrial exposure (e.g.

Occupational Safety and Health Administration (OSHA) PELs), toxicology (e.g.LD50), and medicine (e.g. medicationand radiation doses)

"The solution to pollution is dilution", is a dictum which summarizes

a traditional approach to pollution management whereby sufficiently diluted

pollution is not harmful.[37][38] It is well-suited to some other modern, locally
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scoped applications such as laboratory safety procedure and hazardousmaterial release emergency management. But it assumes that the dilutant is in

virtually unlimited supply for the application or that resulting dilutions are

acceptable in all cases.

Such simple treatment for environmental pollution on a wider scalemight have had greater merit in earlier centuries when physical survival was often

the highest imperative, human population and densities were lower, technologies

were simpler and their byproducts more benign. But these are often no longer the

case. Furthermore, advances have enabled measurement of concentrations notpossible before. The use of statistical methods in evaluating outcomes has given

currency to the principle of probable harm in cases where assessment is warranted

but resorting to deterministic models is impractical or infeasible. In addition,

consideration of the environment beyond direct impact on human beings hasgained prominence.

Yet in the absence of a superseding principle, this older approach

predominates practices throughout the world. It is the basis by which to gauge

concentrations of effluent for legal release, exceeding which penalties are

assessed or restrictions applied. One such superseding principle is contained inmodern hazardous waste laws in developed countries, as the process of diluting

hazardous waste to make it non-hazardous is usually a regulated treatment

process.[39] Migration from pollution dilution to elimination in many cases can

be confronted by challenging economical and technological barriers.

1.1.2 h Most polluted places in the developing world

The Blacksmith Institute, an international non-for-profit organizationdedicated to eliminating life-threatening pollution in the developing world, issues

an annual list of some of the world's worst polluted places. In the 2007 issues the

ten top nominees, already industrialized countries excluded, are locatedinAzerbaijan, China, India, Peru, Russia, Ukraine and Zambia.[40]

1.1.3 Trace analysisTrace analysis is also becoming an important tool of pollution control, moreover

it is also required in geology and archeology. Testing for contamination or high

purity requires a materials testing lab that can produce accurate, reliable, andreproducible test results. NSL provides trace analysis at detection ranges from 10

ppb to 1 ppm.
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1.1.3 a Typical trace analysis competencies include:

Identification of unknowns Analysis for impurities

Contamination detection

Trace metals analysis

Elemental analysis

Our highly skilled and experienced chemists have performed traceanalysis on diverse materials and industries including:

Polymers and plastics Consumer products

Adhesives and coatings

Metals Pharmaceuticals

Electronics

1.1.3 b Instrumentation:

DC ARC ICP/MS

AAGF

CVAA

1.1.3c Timothy M. Benjamin and Pamela Z. Rogers of Los Alamos

and Dorothy Woolum of the California Institute of Technology, performed some

trace elemental analysis work as stated under.These scientists have also stated thedifficulties associated with there analysis work.

Geologic materials are complex, heterogeneous mixtures of minerals,often small grained and each with a different composition. Study of these

materials demands an instru-ment capable of providing spatially resolved, in situ

elemental analyses. The electron microprobe is adequate to the task if a sensitivity

of 1000 parts per million is sufficient. The nuclear microprobe, which is capableof analysis at the level of 10 parts per million, can measure trace-element

distributions in individual mineral grains in addition to major and minor elements.

Experiments of this type were not before possible.

For example, -consider the problem of determining the relative ages

of meteorites, information important to theories of the origin and evolution of the


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solar system. Relative ages of meteorites can be deduced from the inferredabundances of the isotope plutonium-244. (Plutonium-244 is now extinct; its

former abundance in a meteorite can be inferred, for example, from the abundance

of its xenon decay product.) Since plutonium has no stable or very long-livedisotopes, this dating technique requires normalizing the plutonium abundance to

that of another element in the meteorite. There is evidence suggesting that the

geochemical behavior of plutonium is similar to that of uranium and the light rareearths, and therefore one of these elements is usually chosen for the

normalization. But the validity of the normalization hinges on whether plutonium

and the normalized element undergo similar fractionation during mineral

formation. Experiments on synthetic geologic samples have shown that themagnitude of plutonium fractionation is between those of uranium and of the light

rare earths. This fact allows application of a proposed bracketing theorem

leading to the conclusion that if uranium and the light rare earths, when

normalized to cosmic abundances, are not fractionated relative to each other in aparticular meteoritic mineral, then the plutonium also was not fractionated relative

to uranium and the light rare earths. The nuclear microprobe can select those

meteorites suitable for plutonium-244 dating by determining that their contents ofuranium and light rare earths are unfractionated.

The nuclear microprobe can also be used to study partitioning of traceelements in metal-sulfide-silicate systems. By comparing trace- element

concentrations in the rocks of planetary objects with the results of synthetic

partitioning experiments, we can obtain information about the differentiation of

the planets into metallic cores and silicate mantles. Previously, such studies werehampered by the low concentrations of siderophile (metal-loving) and chalcophile

(sulfide- loving) elements in silicate phases, lithophile (silicate-loving) andchalcophile elements in metal phases, and siderophile and lithophile elements in

sulfide phases and by the necessity of physically separating the various phases

before measuring the trace-element concentrations. Although the nuclear

microprobe is able to detect the rare earths at a concentration of 10 parts permillion, the solid-state x-ray detector cannot resolve the peaks that overlap. A

focusing crystal spectrometer has the necessary energy resolution to resolve these

peaks but only about one-thousandth the efficiency of the Si(Li) detector. To

overcome this difficulty, the microprobe current could be increased by makinguse of the high phase-space acceptance of the solenoid. A crystal x-ray

spectrometer is being added to the Los Alamos nuclear microprobe to combine

high-resolution x-ray spec- troscopy with spatially resolved trace-elementsensitivity.


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Trace element analysis using neutron activation has been used tocharacterize archaeological bone. The alkaline earth elements strontium and

barium appear to be reliable indicators of bone origin. Studies of recently killed

specimens suggest that these elements are homogeneous throughout the skeletalmatrix so that small samples may be regarded as representative of the entire

organism. Alterations of elemental concentrations resulting from interactions of

the sample with the depositional environment have been examined empirically byanalyzing various samples in contact with contrasting depositional environments

for different time periods. The results of the analysis of over 350 morphologically

distinct specimens have provided identification criteria for archaeological artifacts

made from bone of unknown origin.[41].

Analysing the above facts , there is a need for the development of

methods for detection, estimation and removal of pollutants, which has recentlybecome an active field of analytical chemistry. This search has resulted in the

emergence of an entirely new area of research called the "Kinetic methods of

Analysis". Many possibilities of analytical interest are provided by the study ofligand substitution reactions. But before any indicator reaction can be chosen for

an analytical application a detailed kinetic picture is quite often a necessary pre-

requisite for the same.

Other important considerations such as scope, sampling and standard

requirements, cost of equipment and time of analysis, are also of great practicalsignificance. A number of methods such as AAS, ETAAS, ICPMS, NAA, FIA

Ion chromatography and anodic stripping analysis can be used for determinationof trace metal ions. The advantages of instrumental methods are low detection

limits, high sensitivity and selectivity, possibility for multi component analysis,

non destructive nature, distance analysis and analysis "invivo". Along with these

advantages there are certain limitations to the above stated methods. Many ofthese methods require complicated and expensive instruments and these

techniques are usually not available in most routine laboratories. A recent addition

to the above list is the "Kinetic Method analysis", which ranks high among the

analytical procedures Fig. 1.2 and offers some distinct advantages over theconventional methods such as simplicity, specificity, accuracy and economy. By

kinetic method which is sometimes also reaction rate method it is often possible

to measure immediately after mixing the reactants, the rate of change of someparameter 'P' of the particular reactant (s) whose concentration is to be determined

or product of the reaction and not wait for the reaction to go to compelition or

attain equilibrium. This saving in time may or may not be significant, depending

on the specific reaction, but there are good examples [42-48] of obtaining


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quantitative rate results in seconds for some selective reactions that would haverequired many minutes or hours to go to completion. Another important aspect of

these kinetic methods is that they can determine the concentration of two or three

chemically closely related constituents in a mixture, without separating themphysically by using differential rate methods.

(+ = flame, * = without flame)

Fig. 1.2 Limits of applicability of the most important trace analysis methods

Modern analytical Chemists make use of a number of methods for

analysis based on chemical, physical and physicochemical changes that are

exhibited by substances on chemical reactions. Kinetic method of analysis is one

such important method of analysis and it is most commonly used nowadays.Every chemical process whatever its nature takes place at a finite rate tending to

an equilibrium (Fig. 1.3). Some reactions are so fast and attain the equilibrium

practically instantaneously. Some of them are slow and take a very long time toattain equilibrium. There are certain reactions moderate in nature and amenable to

follow the course of reaction with a suitable analytical technique. Fast reactiontechniques are available for studying the very fast (nano and pico second)


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reactions. The most commonly used basic analytical techniques such asprecipitation, acid-base neutralization reactions, redox reactions, complexometry

reactions are equilibrium based kinetic methods with some distinguishable trends.

In this unit we will be studying the kinetics of moderate reactions in the dynamicregion before it tends to attain equilibrium.

1.1.3d Types Of Kinetic Methods

Kinetic methods are classified by a number of criteria. Broadly it can

be classified as catalytic and non-catalytic methods (disscussed later). Thecatalytic methods are further divided according to the type of reactions involved.

The non-catalytic reactions have been classified according to whether they are

applied to the determination of single species or of several components in a

mixture. Another method is based on the number of components determined, namely single component and multi-component methods.

Based on the experimental approaches, it can be broadly classified as

mixing methods, relaxation methods and equilibrium methods.

Mixing methods: (Methods based on mixing and following ofreaction course as the systems approach equilibrium state)

1. Batch mixing

2. Stopped flow mixing

3. Continuous flow mixing

Relaxation methods: (Systems at equilibrium is suddenly disturbed from theequilibrium position and observed as it relaxes to equilibrium condition)

1. Jump techniques (temperature, pressure, electric impulse, photon impulse)

2. Periodic relaxation techniques ( Ultrasound wave propagation, dielectric)

3. Spectral relaxation techniques (Fluorescence and phosphorescence)

Equilibrium methods (Techniques that permit extracting rate data

without disturbing the system at equilibrium) Resonance techniques (Nuclearmagnetic resonance (NMR) and Electron spin resonance (ESR) )

Kinetic methods are particularly advantageous when reactions are

slow that it is impractical to wait until the equilibrium is reached.


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1.1.3 e Measurement Of Reaction Rates

Let us consider a simple case that the analyte A decomposes to form the product,

P.

A P

The rate of disappearance of analyte and the rate of product formation

as a function of time, t, is pictorially represented in Fig. 1.3. Either the rate ofdisappearance of analyte A, or the rate of formation of product P can be used as a

measure to follow the course of reaction by means of a physical, chemical or

physicochemical method, say conductance by conductometry, potential bypotentiometry, pH by using a pH meter, colour by spectrophotometry and so on.

Fig. 1.3: Change in concentration of analyte [A] and product [P] as a

function of time. Until time te, the analyte and product concentrations are

continuously changing. Then is the equilibrium region


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In general in a kinetic reaction, the variation of concentration ofproduct formed is monitored as a function of time for a series of concentrations of

analyte and plotted. Following this the calibration curve is prepared by plotting

the concentration of product or reaction rate or any other suitable parameter as afunction of concentration to get a straight line with zero or non-zero intercept.

From this the concentration of unknown is obtained.

In the past few years several excellent monographs on the kinetic

methods of analysis have appeared [48-57] and a significant drive has been made

towards the development of analytical methods for compounds, both inorganicand organic and compounds of biological interests, in a variety of complex

samples.

Before any reaction can be used for its analytical purpose, it becomes

absolutely necessary, to study in detail the kinetics and mechanism of that

reactions. Once this is done it is a relatively easy matter to choose experimentalconditions like concentration, pH, temperature and ionic strength etc. that would

provide maximum sensitivity, selectivity and precision for estimation of the

desired chemical species.

Catalytic determinations are the most widely used of the kinetic

methods. The field of catalytic methods includes the methods of determination of

trace concentration of metal ions, anions and many organic substances. Lowdetectable quantities and high sensitivities are recognized as major advantages of

catalytic determinations. Selectivity, on the other hand, can be considered to limitthe practical application of these determinations.

In recent years many catalytic methods have been studied. Theevolution and the innovations introduced, over the last two decades have been

reviewed comprehensively [58-81]. The importance of kinetic studies goes

beyond their direct application in determinations, since most physical or chemical

processes used in contemporary analytical chemistry have their kinetic aspects.Mottola [60] has for example, discussed systematically the aspects of kinetics that

have become part of modern analytical chemistry. Every process, whatever its

nature, takes place at a finite rate, tending to an equilibrium, state. The two states,the kinetic (dynamic) state, and the equilibrium (static) state are both of high

informing power [61]. Reaction-rate methods are becoming increasingly

important practically in analytical chemistry; progress however, relies heavily on

better elucidation of the mechanisms of chemical reactions. Recent developments


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in instrumental design and, especially, in the incorporation of microcomputers forthe control of experiments and data evaluation allow for improved precision,

limits of detection, rapidity and automation of such methods.

On the other hand majority of easy chemical methods suffer in

sufficient sensitivity. That is why sometimes it is considered that possibilities ofchemical reactions in trace analysis are exhausted. Exceptions to this are

enzymatic catalytic methods. The high turnover numbers of enzymes allow one

particle of catalyst to take part in a great number of elementary reactions.

Moreover, the high selectivity of enzyme action ensures good selectivity ofreaction.

In most cases the reaction rate is monitored photometrically. Theenzymatic catalytic methods combine low limits of detection, high selectivity,

simple and available technique. That is why these methods compete successfully

with the instrumental methods. Moreover, they are irreplaceable for determinationof enzyme activity in analytical practice [82].

Keeping this in view further discussion has been divided into twoparts. In the first part, a brief survey of chemical kinetics and significant

developments in the ligand substitution reactions is reported while the second half

deals with the principles and applications of ligand substitution reactions for trace

determination by kinetic catalytic methods (KCM) of analysis, characterization,classification and methodology.


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REVIEW PART- I

1.2 Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study ofrates of

chemical processes. Chemical kinetics includes investigations of how differentexperimental conditions can influence the speed of a chemical reaction and yield

information about the reaction's mechanism and transition states, as well as the

construction of mathematical models that can describe the characteristics of a

chemical reaction. In 1864, Peter Waage and Cato Guldbergpioneered thedevelopment of chemical kinetics by formulating thelaw of mass action, which

states that the speed of a chemical reaction is proportional to the quantity of the

reacting substances.

Chemical kinetics deals with the experimental determinationofreaction rates from whichrate laws and rate constants are derived. Relatively

simple rate laws exist forzero-order reactions (for which reaction rates are

independent of concentration), first-order reactions, and second-order reactions,

and can be derived for others. In consecutive reactions, therate-determiningstep often determines the kinetics. In consecutive first-order reactions, asteady

state approximation can simplify the rate law. The activation energy for a reaction

is experimentally determined through the Arrhenius equation and the Eyringequation. The main factors that influence the reaction rate include: the physical

state of the reactants, the concentrations of the reactants, the temperature at whichthe reaction occurs, and whether or not any catalysts are present in the reaction

1.2.1 Factors Affecting Reaction Rate

1.2.1 a Nature of the reactants

Depending upon what substances are reacting, the reaction rate varies.

Acid/base reactions, the formation ofsalts, and ion exchangeare fast reactions.

When covalent bond formation takes place between the molecules and when largemolecules are formed, the reactions tend to be very slow. Nature and strength of

bonds in reactant molecules greatly influence the rate of its transformation intoproducts.
http://en.wikipedia.org/wiki/Reaction_ratehttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Transition_statehttp://en.wikipedia.org/wiki/Peter_Waagehttp://en.wikipedia.org/wiki/Cato_Guldberghttp://en.wikipedia.org/wiki/Law_of_mass_actionhttp://en.wikipedia.org/wiki/Reaction_ratehttp://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Reaction_rate_constanthttp://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Rate_law#Zero-order_reactionshttp://en.wikipedia.org/wiki/First-order_reactionhttp://en.wikipedia.org/wiki/Second-order_reactionhttp://en.wikipedia.org/wiki/Rate-determining_stephttp://en.wikipedia.org/wiki/Rate-determining_stephttp://en.wikipedia.org/wiki/Steady_state_(chemistry)http://en.wikipedia.org/wiki/Steady_state_(chemistry)http://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Activation_energyhttp://en.wikipedia.org/wiki/Arrhenius_equationhttp://en.wikipedia.org/wiki/Eyring_equationhttp://en.wikipedia.org/wiki/Eyring_equationhttp://en.wikipedia.org/wiki/Reaction_ratehttp://en.wikipedia.org/wiki/Physical_statehttp://en.wikipedia.org/wiki/Physical_statehttp://en.wikipedia.org/wiki/Concentrationshttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Catalystshttp://en.wikipedia.org/wiki/Saltshttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Saltshttp://en.wikipedia.org/wiki/Catalystshttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Concentrationshttp://en.wikipedia.org/wiki/Physical_statehttp://en.wikipedia.org/wiki/Physical_statehttp://en.wikipedia.org/wiki/Physical_statehttp://en.wikipedia.org/wiki/Reaction_ratehttp://en.wikipedia.org/wiki/Eyring_equationhttp://en.wikipedia.org/wiki/Eyring_equationhttp://en.wikipedia.org/wiki/Arrhenius_equationhttp://en.wikipedia.org/wiki/Activation_energyhttp://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Steady_state_(chemistry)http://en.wikipedia.org/wiki/Steady_state_(chemistry)http://en.wikipedia.org/wiki/Steady_state_(chemistry)http://en.wikipedia.org/wiki/Rate-determining_stephttp://en.wikipedia.org/wiki/Rate-determining_stephttp://en.wikipedia.org/wiki/Second-order_reactionhttp://en.wikipedia.org/wiki/First-order_reactionhttp://en.wikipedia.org/wiki/Rate_law#Zero-order_reactionshttp://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Reaction_rate_constanthttp://en.wikipedia.org/wiki/Rate_lawhttp://en.wikipedia.org/wiki/Reaction_ratehttp://en.wikipedia.org/wiki/Law_of_mass_actionhttp://en.wikipedia.org/wiki/Cato_Guldberghttp://en.wikipedia.org/wiki/Peter_Waagehttp://en.wikipedia.org/wiki/Transition_statehttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Reaction_rate


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1.2.1b Physical state

The physical state (solid, liquid, orgas) of a reactant is also an

important factor of the rate of change. When reactants are in the samephase, asin aqueous solution, thermal motion brings them

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