ANALYSIS OF TRANSITION METAL AND RARE EARTH

CHLOROSULPHATES

DISSERTATION submitted In partial fulfilment of the requirementf

for the award of the degree of

MdL^itx of ^{jilosoptip IN

APPLIED CHEMISTRY •Sr

,«

BY ^"^

MOHAMED NAJAR P. A.

DEPARTMENT OF APPLrED CHEMISTRY Z. H. COLLEGE OF ENGINEERING Qc TECHNOLOGY

ALIGARH MUSLIM UNIVERSITY ALIGARH (INDIA)

1994

DS2541

*«;^,, : ,„. , :J..\l^y*r~''

TO My

4ENT OF APPLIED CHEMISTRY

Phone : Office : 6042

ZAKIR HUSAIN COLLEGE OF ENGG. & TECHNOLOGY

ALIGARH MUSLIM UNIVERSITY ALIQARH—202002 (INDIA)

Dated

CBRTIFICATE

Certified that the work embodied in this

dissertation entitled " Analysis of Transition Metal

and Rare Earth Chlorosulphates" is the original

work carried out by Mr. Mohamed Najar P. A., under

my supervision. This work is suitable for the

submission of the award of M.Phil. Degree of Aligarh

Muslim University/ Aligarh.

Dr. All Mohammad

(CO-SUPERVISOR)

Prof. K.T. Nasim

(SUPERVISOR)

ACKNOWLEDGEMENT

It is indeed a great pleasure to express

my gratitude towards Prof. K.T. Nasiiii/ for his keen

interest/ valuable suggestions, sympathetic

behaviour and continuous encouragement throughout

my work.

I am highly indebted to Dr. Ali Mohammad/

for his extending cooperation and inspirations to

me, stimulating discussion/ interpretation of the

results and help at various stages.

I am extremely beholden to my parents for

their affectionate encouragement/ assistance and

interest in my academic pursuits.

I am specially grateful to Dr. Jameel Ahmad/

for his cooperation for the completion of this work.

Sincere thanks are due to Prof. M. Ajmal Ex-

Chairman and Prof. K.M. Shamsuddin/ Chairman,

Department of Applied Chemistry/ for providing all

possible research facilities in the department for

the smooth progress of the work embodied in this

thesis.

MOHAMED NAJAR P.A.

LIST OF PUBLICATION

Thin Layer Separation of Transition Metal

Chlorosulphates and Quantitative Spectrophotometric

Determination of Cobalt Chlorosulphate.

ANALUSIS,, FRANCE., In Press.

CONTENTS

S.No. Page No.

(A) CHAPTER I

1. Introduction 2

2. Thin Layer chromatography 6

3. Thin Layer chromatograhic Analysis 19

of Transition Metal and Rare Earth

Chlorosulphates

4. References 25

(B) CHAPTER II

1. Thin Layer Separatiion of Transition Metal 31

Chlorosulphates and Quantitative Spectro-

photometric Determination of Cobalt

Chlorosulphate

2 . T a b l e s 41

3 . C a p t i o n f o r F i g u r e s 43

4 . F i g u r e s 44

5. References

(C) CHAPTER III

1. Some Observations on the Mobility of Rare

Earth Benzoates and Chlorosulphates on Silica

Alumina and Cellulose Layers

2. Tables

3. References

48

49

56

60

CHAPTER - I

INTRODUCTION

Natural science is the process and result of

systematically arranging and classifying man's knowledge of the

world about him. The first step in the formation of a science

is the collection of undoubted facts relating to its subject.

Natural science forms a coherent whole, but is artificially

divided in to departments for the purpose of study. Chemistry

as a science is but a modern growth. It is difficult to say

where and when the chemists craft began. It is fairly certain

that the Arabs who rose to power in the seventh century AD,

first gained their knowledge of chemistry directly or

indirectly from the Byzantine author's work. The knowledge

acquired by the Arabs was gradually handed on to European

people during the thirteenth and fourteenth centuries.

Analytical chemistry is a branch of chemistry basically

concerned with the determination of the chemical composition of

matter. The modern aspects of analytical chemistry are the

identification of a substance, the elucidation of its structure

and quantitative analysis of its composition. The ever

increasing impact of analytical methods reveals that no other

branch of science finds so extensive applications as analytical

chemistry for two reasons. It finds numerous applications in

various disciplines of chemistry such as inorganic, organic,

physical and biological chemistry. Secondly it finds extensive

applications in other fields of science such as environmental

science, agricultural science, biomedical and clinical

-2-

chemistry solid state research and space research. Owing to the

great importance of pollution the environmental chemistry is

becoming more relevant. Instrumental and non-instrumental

methods are being developed for the analysis of air, water and

soil pollution.

Analytical chemistry involves the development of new

methods suited for the requirements. The classical methods

have to be modified not only for the determination of elements

in the ores but also in the estimation of stoichiometry of

precious metal alloys like Pt-Rh with high degree of precission

and accuracy.

Two important steps in analysis are identification and

estimation of constituents of a compouds. The identification

step is called qualitative analysis while estimation step is

called quantitative analysis. The first step is quite simple,

but the second step of quantitative analysis can be classified

depending upon the method of analysis. The methods involved in

chemical analysis are instrumental or non-instrumental. The

instrumental methods are faster and applicable at very low

concentrations. However non-instrumental methods are needed to

be strengthened because they are simple, inexpensive and

versatile.

The identification and separation of various species can

be achieved by number of systematic procedures such as

precipitation, dialysis , ring oven technique, solvent

extraction, ion exchange, electrophoresis and chromatography .

-3-

However, the most modern and versatile analytical techniques

include ion exchange, electrophoresis and chromatography. Ion

exchange can be used to separate ionic and non-ionic impurities

or similar- pairs of cationic and anionic species. The

selectivity of exchanger depends upon the nature of the

exchanger and composition of the eluent. The separation

potential of the exchange process can be increased by the

suitable selection of the exchanger and mobile phase. The

exchanger phase may be organic or inorganic in nature. The

organic ion exchangers were discovered by Adam and Holmes in

1935. The major disadvantage of organic ion exchangers is the

lack of resistance to heat and radiation. As a result synthetic

inorganic ion exchangers being more resistant to heat and

radiations have received considerable attention during the last

ten years (1).

The use of electrophoresis was first reported in 1937 by

K6nig (2). In 1939 Konig and Van Klobusitzky (3) separated a

yellow pigment from a snake venom using paper electrophoresis.

Martin and Synge (4) used the terms e.g. inophoresis to define

processess concerned with the movement in an eletric field of

relatively small ions, electrophoresis for movement of large

molecules ore particles and electrodialysis for the removal of

smaller ions from large molecules and particles.

-4-

Table-1

Type of Analysis I

Instrumental

Precipitation

Non-instrumental

Dialysis

Ring oven Technique

Ion exchange

Electrophoresis

Chromatography

CHROMATOGRAPHY

Chromatography is a physical method of separation in which

the separating components are distributed in two phases, one of

which constituting a stationary bed of large surface area, the

other being a fluid that percolates through the stationary

phase. The origin of chromatography goes back to Runger's

experiment on capillary analysis. Davy observed changes in

composition of crude petroleum when it come into contact with

rocks displaying adsorptive activity. These reports may be

considered as the part of development of chromatography. The

-5-

paper presented by Michael Tswett in 1903 at the meeting of

Biological Section of the Warsa Society of Natural Science is

generally accepted as the beginning of chromatography. He

published two papers (5) on the separation of plant pigments.

The pioneering work of Martin and Synge (6,7) set a precedent

for the development of other forms of chromatography. The

technique of chromatography may be divided and subdivided as

shown in Table-2.

The classification of chromatographic method is relatively

simpler as the mobile phase used may be a gas or liquid and the

stationary phase may be a liquid or solid. Thus liquid -liquid,

liquid-solid, gas-liquid and gas-solid combination arised. When

the separation involves predominantly a simple partition

between two liquid phases (one stationary and other mobile

phase) the process is called partition chromatography. If

physical surface forces are mainly involved in the retentive

ability of the stationary phase, the process is called as the

adsorption chromatography. If the mobile phase employed is a

gas, the method is called gas-liquid or gas-solid

chromatography.

Adsorption, ion exchange or partition of solutes in

chromatogrphy can be performed either using a column or thin

layer as the stationary phase. In adsorption chromatography,

the stationary phase is a surface active granular solid. Silca

is now the most common stationary phase. Other commonly used

adsorbents are alumina, magnesia and organic polymers.

-6-

THIN LAYER CHROMATOGRAPHY

Among chromatographic techniques, thin - layer

chromatography(TLC) is simple, inexpensive, rapid and

versatile method, which is n[)|)Jicablc to the analysis of a

multicomponent mixtures except volatile or reactive

substances. TLC has always been recognized as a practical and

effective technique for purifying materials before their

analysis with sophisticated instruments .The mobile phase in TLC

is a liquid, containing a single solvent or a mixture of

solvents,the stationary phase ig an active solid termed as the

sorbent.Since numerous sorbents are available such as silica

gel, cellulose, alumina, polyamides, ion exchangers etc, allows

considerable versatality in the type of substances that can be

separated.

HISTORY OF THIN LAYER CHROMATOGRAPHY

The discovery of thin layer chromatography is usually

ascribed to Izmailov and Schraiber(8) who utilized thin

layers( 2 mm thick) of alumina on glass plates for

chromatographic separations,in what they called drop chromat­

ography.It did not receive much attention and only in the last

three decades it has grown prodigiously. TLC began to attract

attention through the works of Kirchner and his associates.

-7-

starting in 1951 (9-11). It was not until 1958, when

Stahl(12)described equipment and efficient sorbents for the

preparation of TLC plates, that the effectiveness of the

technique for separation was shown.

At early stage TLC was mainly used for the separation of

organic compounds. The developments in TLC of inorganic ions

appeared in the literature after the work of Seller ( 13-15 )

The first application of inorganic TLC was reported in

1949 by Meinhard and Hall(16). The work on TLC of organic and

inorganic substances up to 1972 has been admirably documented

by Brinkman et al.(17) where as the work done during 1972-1980

and 1981-1990 on inorganic substances has been summarized by

Kuroda and Volynets (18) and Mohammad and Varshny (19)

respectively.

The first report of densitometry in TLC reported by Dallas

et al.(20) in the mid 1960's. High performance TLC plates(2l)

were produced commercially in the mid 1970's. As a result of

improvements in practice and application in the late 1970's and

1980's high performance TLC (HPTLC) (22), instrumental

HPTLC(23), centrifugally accelerated preparative layer

chromatography (24) over pressured layer chromatography (OPLC)

(25) were introduc ed .As a result of this, the reasons for

performing TLC is continuously changing over the years and now

emphasis is shifting from analysing natural mixtures of organic

and inorganic substances to the analysis of biological

pharmaceuticals, alloys and environmental samples.

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-9-

Table-3

Chronological Developments of Chromatographic Techniques

SI.no. Technique Year of Discovery

Discovered by

1. Thin-Layer Chromatography 1938

(TLC) Adsorption

2. Partition Chromatography 1941

3. Paper Chromatography(PC) 1944

4. Counter Current 1944

Distribution(CCD)

5. Gel Permeation 1945

Chromatography(GPC)

6. Gas Chromatography(GC) 1945

7. Ion Exchange Chromatography 1947

(lEC) Adsorption

8.. Electrophoresis 1948

9. Thin-Layer Chromatography 1951

(TLC) Partition

10. Gas-Liquid Chromatography 1952

(GLC)

11. High-Performance Liquid 1952

Chromatography(HPLC)

12. Ion-Exchange Chromatography 1963

(lEC) Partition

13. High Performance Thin-Layer 1974

Chromatography(HPTLC)

14. Ion Chromatography 1975

1 5 . Overpressured Layer 1979

Chromatography(OPLC)

Izmailov and

Schraiber

Martin and Synge

ConsdenjGordan and

Martin

Craig

Barrer

Claesson

Mayer and Thompkins

Haugaard and Kroner

Kirchner,Miller and

Keller

James and Martin

James and Martin

Samuelson

James and Martin

Small,Stevens and

Bauman

Tyihak ,Mincsovics and Ka lasz

-10-

PROCEDURE

The basic TLC procedure is carried out as follows. About

0.5-10 pi of a sample mixture containing 0.5-5 mg of solute is

spotted on to a TLC plate at about 3 cm from the lower edge of

the plate. The spot is completely dried at room temperature or

at an elevated temperature and the plate is developed with a

suitable solvent inside a closed chamber. Capillary action

results the mobile phase to travel through the stationary phase

in a process called development and allowed to migrate up the

plate 10-18 cm from the origin on the TLC plate. The components

of the mixture migrate at different rates during the

development. After the development the chromatogram is

withdrawn from the chamber, dried at room temperature and the

separated zones are detected using suitable detection reagent.

The differential migration between the solutes results because

of varying degrees of affinity of the mixture components for

the stationary and mobile phases.

Compound identification on TLC plates is based on the R„

value which is a measure of the ratio of the distance travelled

by the solute from the point of origin to the distance

travelled by the solvent.

distance travelled by the solute

R (Retardation factor) = F

distance travelled by the solvent

Rp values varies between 0.0 and 0.999 and have no units.The

entire process of TLC can be summarized as in Table-4.

-11-

Table-4 The process of Thin-Layer Chromatography

TLC Procedure

Sample preparation

Relatively pure

components

L I

Crude/Impure extracts

1 Sample purification

Distillation/centrifugation/

Se

precipitation I

lection of stationary and mobile . I phase

1 Sample application

Spotting/.Streaking

Chromatogram development

1 Drying of chromatogram

I Detection

Visual/UV scaning/Reagent spray/Densitometry 1 Component removal evaluation of qualitative

and quantitative analysis(Optional)

1 Documentation

I Computation and reporting of results

-12-

PRINCIPLE AND TECHNIQUES

In all chromatographic procedures, the optimum conditions

for separation are yielded through mutual harmonization of the

stationary and mobile phases. The desired separation can be

achieved by proper selection of adsorbent and solvent. The

physical and chemical characterization of compounds determine

the degree to which a paircan interact with each other. This is

true for mobile phase-solute, solute-sorbent and mobile phase-

sorbent interactions.

Some important characteristics are:

a) Intramolecular forces, which hold neutral molecules together

in the liquid or solid state.These forces are physical and they

are characterized by low equilibrium and result in good

chromatographic separation.

b) Inductive forces, which exist when a chemical bond has a

permanent dipolemoment associated with it (eg. C-Cl or C-NOo

group) affect interactions. Under influence of this field, the

electrons of an adjacent atom, group or molecule are polarized

so as to give an induced dipole moment. This is a major

contributing factor in the total adsorptive energy on alumina.

c) Hydrogen bonding, makes a strong contribution in adsorptive

energies between solute or solvents having a proton donour

group and a nucleophilic polar surface such as that of alumina

or slica gel.

d) Charge transfer, between components of the mobile phase and

the sorbent can also take place to form a complex of the type

-13-

+ - (where S = solvent or solute and A = surface site of

sorbent).

e) Covalent bond, can be formed between solute and or the

mobile phase and the sorbent. These are strong forces and

result in poor chromatographic separation.

The solvent strength parameter o

The solvent strength parameter E is defined by Snyder

(26)as the adsorption energy per unit of standard sorbent. The

higher the mobile phase strength, the greater will be the R^ of

the solute in simple liquid-adsorption TLC. Decreasing the

solvent strength can be increase resolution. Difficult

separation can be achieved by varying the selectivity(changing

interaction) of the mobile phase. Since the solvent strength is

dependent on its reactivity with the sorbent, with a large

number of sorbents available, it is easy to find the best

mobile phase for separating the components.

Adsorbents

A large number of sorbents are available which can be used

in TLC. The most commonly used are silica gel, alumina,

cellulose and Kieselguhr (diatomaceous earth).

Silica gel (silicic acid) is the most popular layer

material. It is slightly acidic in nature. At the surface of

silica gel the free valencies of the oxygen are connected

either with hydrogen (Si-OH) or with another silicon atom (Si-

0-Si). The silanolgroup represent adsorption active surface

-14-

centre that are able to interact with solute molecule.

Alumina or aluminium oxide is also generally used as a

sorbent. It is basic in nature and rore reactive than silica

gel.

Kieselguhr is a chemically neutral- sorbent that does not

separate or resolve as well as either alumina or silica gel.

Cellulose can be used as a sorbent in TLC when it is

convenient to perform a given paper chromatographic separation

by TLC inorder to decrease the time required for the separation

and increase the sensivity of detection.

In addition the importance of using surface modified

sorbents in TLC has increased. Both hydrophilic and hydrophobic

modified sorbents has been used in recent years.

Layer coating procedures

The methods used to coat a plate with a thin layer of

sorbent include i) pouring ii) spreading iii) immersing and

iv) spraying. Among these the spreading procedure is the most

widely used because of good reproducibility, easy adjustment of

layer thickness and ease of operation.

Sample preparation

Various modes in sample preparation are employed to make a

ready for chromatographic analysis such as dissolving of

samples, extraction, column chromatography, centrifugation,

evaporation etc.

Cations are generally dissolved in distilled water

maintaining a constant concentration such as 1% or 0.1 M. Rare

-15-

earth solution are prepared by dissolving their nitrats in O.IM

HNCk or fusion followed by dissolution in dilute HCl or HNCL .

Anions are usually taken as their water soluble sodium,

potassium or ammonium salts. Methanol or ethanol are used as

solvent for preparing the sample solution of organometallics.

Sample application

Sample should be applied as a 0.01-1.00 % solution in the

least polar solvent in which they are soluble. 0.1-0.5 %

solution concentration is preferable. Sample can be applied as

spots or streaks on the TLC plate about 2-3 cm above from the

lower edge, so that only mobile phase makes contact with the

sorbent layer. The samples should be completely dried before

placing the plate in the developing chamber.

Micropipette, microsyringe, melting point capillaries etc.

are used to apply the sample on the plate.

Development

Development is the process in which the mobile phase move

across the sorbent layer to effect separation of the sample

substances. There are several modes of development such as

ascending, descending, two dimensional (27-29) horizontal,

radial (circular), multiple (manual) (30,31) over run

(continuous) (32) programmed multiple, gradient etc. Among

these, ascending is the most frequently used development mode

in TLC. The plate is placed in an appropriate tank or jar such

a manner that the solvent should remain below the point of

application of the sample. The solvent is then allowed to rise

-16-

by capillary action to a distance of 10 to 18 cm above the

origin on 20 x 20 cm TLC plate is marked on the plate in

advance at the time of sample application. It has been noted

that the angle at which the plate is supported effect the rate

of development as well as the shape of the spot (33). An angle

o

of 75 is optimum for development.

Detection

The method of detection used in TLC are of three major

types i) physical ii) chemical and iii) enzymatic or

biological.

The physical method of detection involves the use of

various instrumental techniques such as spectroscopy, auto

radiography^ X-ray fluorescence micro analysis etc. Compounds

that are naturally coloured are viewed directly on the layer in

day light, while compounds with native fluorescence are viewed

as bright zones on a dark background under UV light.

The chemical method of vizualization involves spraying of

chromatoplate with a suitable reagent, which form coloured

compouds with separated species. Reagents giving clear and

suffiently sensitive colour reactions with several species are

preferred.

The first report on enzymatic method for the detection of

heavy metals in fresh water was made by Nanda and Devi (34),

Nicolaus and Coronelli (35,36) have reported a microbiological

method called bioautography for the detection of antibiotics on

TLC plates.

-17-

Documentation of chromatogram

The documentation of chromatogram involves the recording

of all details about the development chamber, mode of

development, thin layers, mobile phase, sample application,

location, reagents and methods employed in the process. Some of

the important ways of documentation are i) photography ii)

densitometry and iii) print out from video monitor.

Quantitation

Three main approaches associated with quantitative

analysis in TLC are i) visual estimation ii) zone-elution and

iii) in situ densitometry.

Quantitation by visual comparison of spot sizes and colour

intensities between samples and standard plate (37). The

accuracy and reproducibility in this method falls in the range

10-30 %. A linear relationship between the spot size and amount

of analyte was reported in the recent past (38-41).

The zone elution involves drying the layer, locating the

separated analyte zones, scrapping the portion of layer

containg the analyte and measurement against standard by an

independent microanalytical technique. This method is accurate

and precize.

In situ measurements of zones with a scanning densitometer

is the preferred technique for quantitative TLC.

Reproducibility

The R-c values in TLC are dependent up on many variables

(42) which must be regulated during the preparation and

-18-

evaluation of the chromatogram to get reproducible results. The

important factors which influnce the R values are : F

i) Nature of sorbent

ii) Layer thickness

iii) Activation temperature

iv) Nature of mobile phase

v) Chamber saturation

vi) P of medium

vii) Room temperature

viii) Sample size and

ix) Relative humidity

Latest developments in TLC

After the introduction of HPLC, the rapid growth of TLC

was slowed down during 1970's. However recent improvements in

TLC have overcome many of its limitations. Several new

techniques such as high performance thin layer chromatography

(HPTLC) over pressurized thin layer chromatography (OPTLC),

centrifugal layer chromatography (CLC), reversed phase thin

layer chromatography, radial chromatography, hot plate

chromatography, bioautography,immunostaining and enzyme

inhibition techniques came in to light. Careful combination

with other analytical techniques such as column

chromatography, spectrophotometry(43), HPLC(44), gas

chromatography(45-50), mass spectrometry(51,52), infrared

spectroscopy(53,54) has further improved the efficiency of thin

layer chromatography of organic and inorganic compounds in a

-19-

great variety of pharmaceutical, agricultural, food,

environmental and industrial samples(55,56).

THIN LAYER CHROMATOGRAPHIC ANALYSIS OF TRANSITION METAL AND

RARE EARTH CHLOROSULPHATES

Metals contribute about one-third of the known elements in

the periodic table of elements and occur in nature some times

free but mostly in combined states. With regarding the chemical

nature metals can be classified in to alkali, alkaline earth,

transition and rare earth. Alkali and alkaline earth metals are

highly reactive species, where as the trasition metals have

their properties intermediate between the metals and nonmetals

or their properties are transitional. Thus transition metals

are those which have partially filled shells of d or f

electrons. Within this group, elements having partially filled

shells of f-electrons are more usually described as rare earth

metals (Ce—*Lu) and actinides (Th-* ). In this account the term

transiton elements include those elements which have partially

filled shells of d-electrons in atleast some of their

compounds. Several types of trasition metal compounds are

known, which appears to be stoichiometric mixture of simple

compounds. Though many of the transition elements are essential

trace elements in both human and plant physiology the higher

levels of intake causes adverse effects. Owing to the

significance of these elements in the medicinal,biological and

industrial applications their mutual separation and

quantitative studies are important.

-20-

The history and discovery of rare earths are very

confusing because of the complexity of the ores and the mixture

with which the early investigators worked, and the numerous

claims of separation and identification which were later shown

to be erraneous. The claim by the Finnish chemist, Gadolin in

1794 of the separation of the oxide of a new element from a

Swedish mineral was the actual beginning of rare earths history

eventhough it was later accepted that the supposed compound was

a mixture of all the rare earth oxides.

The use of the word 'rare' in naming the rare earths (REs)

was probably justified in the days of the early investigations

of the group because of the scarcity of the known sources of

the elements. At present about one hundred and fifty different

rare earth minerals are known to chemists which are, infact,

more abundant as a group than many of the more familiar

elements such as lead, tin, zinc, arsenic, mercury, gold and

platinum. It is estimated that REs stand twenty-fifth in the

order of abundance of the elements in the earth's crust. The

most productive deposit of the REs are found in Brazil,

India, Scandinavia and United States.

The names of discoverer, date of discovery and the

derivation of the names for the rare earths are listed in

Table-5.

-21-

Table-5 Chronological Developments of Discovery and Derivation of the Names

for the Rare Earths.

Name Symbol Atomic Discoverer Year of Derivation of Name Number Discovery

Cerium

Lanthanum

Yttrium

Erbium

Holmium

Scandium

Thulium

Samarium

Neodymium

Praseodymium

Gadolinium

Dysprosium

Terbium

Europium

Ytterbium

Promethium

Ce

La

Y

Er

Ho

Sc

Tm

Sm

Nd

Pr

Gd

Dy

Tb

Eu

Yb

Pm

58 Berzelius 1814

57 Mosander 1837

39 Mosander

68 Berlin

67 Cleve

1842

1860

1879

21 Nilson 1879

69 Cleve 1879

62 Boisbaudran 1879

60 Wilsbach 1885

59 Wilsbach 1885

64 Marignac 1886

66 Boisbaudran 1886

65 Boisbaudran 1895

63 Demarcay 1896

70 Urbain and 1907

Welsback

61 Marinsky, 1947

Gledenin and

Gornycell

Planet Ceres

Greek lanthano

meaning'to conceal'

Ytterby,a town in

Sweden

Ytterby,a town in Sweden

Latin,Holmia' for

Stochholm

Scandinavia

Thule,'north land'

Samaraski,a Russian

army officer

Greek,neos 'new'and

didymos'twin'

Grow precise,green

and didymos'twin'

Finnish chemist

Gadolin

Greek,many 'hard to

get at'

Ytterby'a town in

Sweden

Europe

•8 Y t t e rby , a town in

Sweden

Greek,'Prometheus'

Comprehensive Inorganic Chemistry, M.C.Sneed and R.C.Brasted Vol. TV

-22-

A constant demand for the macroquantities of exceptionally

pure sample of the REs has been made since the very beginning

of the Manhattan Porject. Several methods are generally adapted

for the separation of REs are fractional crystallization,

precipitation, extraction, complex formation and chromatography

A method adaptable to large scale separation dependent on

complex stability, is chromatography(57-59).

The application of lanthanide are generally restricted to

the higher metals. These elements are effective for the

deoxidation, desulfurization and general improvement of the

physical properties of low carbon and low-alloy steel. The

mixed REs were being used, to some extent, to make mischmetal

for the lighter flints. Because of their close similarities ^^

chemical properties the mixed REs collectively behaved as a

single element. The lanthanide metals act as scavengers,

improve ductility and enhance oxidation resistance at high

temperature. The very complex subject of application is best

illustrated in a review by K.M.Handle and H.H.Mandle(60) .

Details of the analytical chemistry of lanthanides are

summarized excellently by Woyski and Harris(61).

Metal complexes represent an important analytical form of

metals and their selective separation is of considerable

interest. Analysis of closely related metals has been a long

persisting problem as routine chemical methods generally failed

in such cases. Thin layer chromatography of metal chelates has

been a valuable technique to the solution of such problems(62-

65). According to literature no attempt has been initiated for

-23-

the chromatographic analysis of transition metal and rare

earth chlorosulphates. The separation of transition metal and

rare earth chlorosulphates is important because of their

scientific, industrial and technological importance. Therefore,

it is of interest to develop a simple and inexpensive

analytical method for separation and quantification of metal

chlorosulphates. The magnetic moment, geometry,colour and molar

conductivity value of metal chlorosulphates of some transition

metals and rare earth elements are given in Table-6.

The purpose of the present study is to develop some

suitable chromatographic systems for rapid TLC separation,

detection and quantitative estimation of transition metal and

rare earth chlorosulphates. The results obtained and the

methods developed are discussed in the following chapters.

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-25-

REFERENCES

1. M. Qureshi and K.G. Varshney/ CRC Handbook of

Inorganic Ion Exchangers in Chemical Analysis. C.R.C.

Press Baca Raton Ann Arbor Boston 1991.

2. P. Konig, Actas e trabalhos do Terceiro congress© Sud

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2, 334 (1937).

3. D. Von Klobusitzky and Konig, Arch. ecpt./ Pathol

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Chem., 2, 31 (1945).

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6. A.J.P..Martin and R.L.M. Synge., Biochem. J./ 35 (91)

1358 (1941).

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(1938).

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Chem./ 23/ 420 (1951).

10. J.M. Miller and J.G. Kirchner/ Annal. Chem., 24/ 1480

(1952) .

-26-

11. J.M. Miller and J.G. Kirchner Anal. Chem., 26, 2002

(1954).

12. E. Stahl, Chemiker Ztg., 82, 323 (1958).

13. H. Seller, M. Seller, M. Helv. Chim. Acta., 43, 1939

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(1949) .

17. U.A. Th. Brinkman, G. De. Vries and R. Kuroda, J.

Chromatogr., 85, 187 (1937).

18. R. Kuroda, M.P. Volynets, C R C Handbook of

Chromatography, Inorg (Qureshi M. et al.) Vol. 1,

C.R.C. Press, boca Raton, Fla, p. 89,(1987).

19. A. Mohammad and K.G. Varshney, In Handbook of Thin

Layer Chromatography, J. Sherma and B. Fried (eds)

Marcel Dckker U.S.A. (1990).

20. M.S.J. Dallas, C.B. Barret and F.P. Podley, Joyce

Loebl. Publications, 3 (1964).

-27-

21. H. Halpaap and J. Ripphahn in HPTLC - High Performance

Thin Layer Chromatography. A. Zlalk's and R.E. Kaiser,

eds., Elsevier, New York, 1977, p. 95.

22. A. Zlalk's and R.E. Kaiser, Eds., HPTLC - High

Performance Thin Layer Chromatography, Elsevier, New

York, 1977.

23. W. Bertsh, S. Hara, R.E. Kaiser and A. Zlatkis, Eds.,

Instrumental HPTLC, Dr. Alfred Huething Verlag, New

York, 1980.

24. H. Harrison, U.S. Patent 4, 139, 458 (1979).

25. E. Tyihak, E. Mincsovics and H. Kalasz, J.

Chromatogr., 174, 75 (1979).

26. L.R. Snyder, Principles of Adsorption Chromatgraphy,

Marcel Dekker, New York, 1968.

27. R.L. Jolley and M.L. Freeman., Clin. Chem., 14, 538

(1961).

28. R.L. Jolley and C D . Scott, Clin. Chem., 16, 687

(1970).

29. A.S. Saini, J. Chromatogr., 61, 378 (1971).

30. E. Stahl, Arch. Pharm., 292 /62, 411 (1959).

31. E. Stahl and V. Kaltenbach, J. Chromatogr., 5, 458

(1961).

-28-

32. M. Mottier and M. Potterat, Anal. Chem. Acta., 31, 46

(1955).

33. D.C. Abbott, H. Egan, E.W. Hammound and J. Thomson,

Analyst., 89, 480 (1964).

34. Y.P. Devi and N.V.K. Nanda, J. Assoc. Office. Anal.

Chem., 64, 1301 (1981).

35. B.J.R. Nicolaus, C. Coronelli and A. Binaghi, II

Farmaca.,, 16, 349 (1961).

36. B.J.R. Nicolaus, C. Coronelli and A. Binaghi,

Experimenta., 17, 473 (1961).

37. B. Lidija, S. Petrovic and V. Paraztie, Microchem. J.,

29, 296 (1984).

38. N. Fatima and A. Mohammad, Sep. Sci. Technol., 19,.

429 (1984).

39. A. Mohammad and N. Fatima, Chromatographia., 22, 109

(1986).

40. A. Mohammad and S. Tiwari, Microchem. J., 44, 39

(1991).

41. J. Maslowska and Z. Mlodzikowski, Chem. Anal., 31, 193

(1986).

42. M. Ajmal, A. Mohammad, N. Fatima and A.H. Khan,

Microchem. J., 39, 361 (1989).

-29-

43. M. Brenner, A. Niederwieser, G. Pataki and A.R. Fahmy,

Experimenta., 18,, 10 (1962).

44. P.R. Boshoff, B.J. Hopkins and V. petrovius, J. C

hromatogr-,, 126, 35 (1976).

45. J.C. Touchstone and M.F. Dobbins, J. Steroid Biochem.,

6, 1339 (1975).

46. P.J. Bloom, J. Chromatogr., 75, 261 (1973).

47. S.J. Mule, J. Chromatogr., 55, 255 (1971).

48. R. Kaiser in Thin - Layer Chromatography, A Laboratory

Handbook, E. Stahl. Ed., Springer - Verlag, New York

1969.

49. J. Janak. J. Chromatogr., 48, 279 (1970).

50. J. Janak, in Pharmaceutical. Application of Thin -

Layer and Paper Chromatography, K. Mack, Ed; Elsevier

Amsterdam, 1972.

51. B.P. Lisoba, J. Chromatogr., 48, 364 (1970).

52. J.R. Majer, R. Perry and M.J. Reade, J. Chromatogr.,

48, 328 (1970).

53. C.J. pereival and P.R. Griffiths, Anal. Chem., 47, 154

(1975) .

54. N. Nash, P. Allen, A. Ben Venue and H. Beckman, J.

Chromatogr., 12, 421 (1963).

-30-

55. J. Sherma, B. Fried (Eds.) 1991/ Handbook of Thin Layer

Chromatography, Marcel Dekker, New York, NY.

56. B. Fried & J. Sherma (1994). This Layer Chromatography

Techniques and Applicatiions., 3rd Eds., Marcel Dekker

New York, NY.

57. W.C. Johnson et al. Chem. Eng. News., 25, 2494 (1947).

58. H. Weil, Can. Chem. Process. Incls. 33, 1036 (1949).

59. B. Ostrot and E.E. Thum., Metal. Progress., 62, No.

1, 67 (1952).

60. R.M. Mandle and H.H. Mandle; in Progress in the Science

and Technology of the Rare Earths. Pergaman Press. New

York, Vol. 1 (1964) pp. 416 - 500. Vol. 2 1966, pp.

190 - 297.

61. M.M. Woyski and R.E. Harris, in Treatise on Analytical

Chemistry ( I.M. Kolthoff and P.J. Elving eds.),

Interscience. Publishers, New York (1963). Part II,

Section A, Volume 8, pp. 1 - 146.

62. R.K. Upadhyay and V.P. Singh, J. Indian Chemical. Sci.,

52, 1164 (1975).

63. R.K. Upadhyay, Chromatographia., 25, 324 (1988).

64. A. Daneels, D.L. Massat and J. Hosle., J. Chromatogr.,

144 (1965).

65. N. Halzapfel, Le-Viet-Lan and A. Werner, J.

Chromatogr., 24, 153 (1966).

CHAPTER - I I

-31-

THIN LAYER SEPARATION OF TRANSITION METAL CHLOROSULPHATES AND

QUANTITATIVE SPECTROPHOTOMETRIC DETERMINATION OF COBALT

CHLOROSULPHATE

Thin layer chromatography (TLC) combined with modern

instrumentation has become a widely used analytical technique

for separatinig inorganic, organometallic and organic species

from solutions. The majority of TLC work has been performed on

layers of silica gel, cellulose,ion-exchangers, silica gel

impregnated with complexing agents and alumina using organic or

organic-aqueous mobile phases. The present study was undertaken

in order to develop a simple, rapid and reliable TLC method for

the separation of transition metal chlorosulphates. Some new

sorbent phases capable of causing differential migration of the

complexes to give binary and ternary separation have been

identified. In addition to the qualitative separations of metal

chlorosulphates, an attempt has also been made for the

quantitative spectrophotometric determination of cobalt

chlorosulphate. Several metal chlorosulphate have been

synthesized in recent past (1-8). The chromatographic and

spectrophotometric studies on these chlorosulphates have not

been so far performed. It is, therefore, of interest to develop

a simple method for separation and quantitative determination

of these transition metal chlorosulphates.

EXPERIMENTAL

Material used

Acetic acid, hydrochloric acid, ammonia, methanol, or

potassium thiocyanate (BDH,India), formic acid, acetone, ethyl

-32-

methyl ketone (EMK) or isobutyl methyl ketone (IBMK) of

E.Merck, India; dimethyl sulfoxide (DMSO), N,N'-dimethyl

formamide (DMF) or silica gel (Qualigens fine chemicals, Glaxo,

India); alumina, kieselguhr, cellulose, acetates of nickel

cobalt, zinc, manganese, iron and copper (Central Drug

House,India), n-butanol, acetic anhydride (Sarabhai

M.Chemicals, India) ethonol (Bengal Chemicals and

pharmaceuticals Ltd.); n-propanol, propanol-2 (Ranbaxy, India)

and amyl alcohol (Fluka AG) were used. All other reagents were

also of analar grade. The commercially available metal acetates

were dehydrated by refluxing with acetic anhydride for about

two hours. DMF and thionyl chloride were used after

distillation.

Test solutions

1% solutions of metal chlorosulphates in DMF were used for

spotting on the chromatoplates. For spectrophotometric

determination, 3.2% solutions of Co chlorosulphates in DMF were

used.

Detection reagents

Saturated potassium thiocyanate in a mixture of acetone

and water (6:1) was used as detector to locate the spots of Ni,

Co, Cu and Fe chlorosulphates and dithizone solution (0.5%) in

benzene was used to detect Zn and Mn chlorosulphates in

chromatoplates.

-33-

Solvent systems

The following solvent systems were used as eluents.

(I) Two-component systems

(i/ Solvent systems cotaining no acids

(a) Ammonia-acetone or methanol (1:9,1:1 and 9:1)

(b) Ethyl acetate-benzene (5:2 and 2:5)

(c) DMSO - acetone (2:1 and 1:2)

(ii) Solvent systems containing acids

(a) Hydrochloric acid - acetone or methanol (1:9,1:1 and

9:1)

(b) Hydrochloric acid - DMSO (2:1 and 1:2)

(II) Three component systems

(a) Acetic acid - alcohol(s) (methanol, ethanol,n-propanol

n-butanol, n-pentanol or n-hexanol) - acetone (3:1:6)

(b) Hydrochloric acid - alcohol (one from the above

alcohols in each case) - acetone (3:1:6)

(c) Acetic acid or hydrochloric acid or hydrobromic acid -

n-butanol - EMK (3:1:6)

(d) Formic acid-acetone-ether (1:1:1)

(e) Hydrochloric acid - DMSO - acetone (1:1:1, 1:7:12,

1:10:9, 1:12:7, 1:15:5, 1:20:19, 1:10:20, 2:1:1, and

2:19:19)

(f) Hydrochloric acid - DMSO - n-butanol or propanol

(1:1:1, 1:1:2, 1:2:1 and 2:1:1)

(g) Acetic acid - n-butanol - EMK (7:1:12, 9:1:10, 10:1:9,

and 12:1:7)

-34-

(h) Acetic acid - methanol - EMK (9:1:10 and 10:1:9)

(i) Acetic acid - propanol-(2) - acetone (4:4:12, 5:3:12,

3:7:10 and 10:1:9)

(j) Acetic acid - n-propanol - EMK (4:4:12, 5:3:12,

3:7:10, 4:7:9 and 5:7:8)

(k) Acetic acid - DMSO (10:1:9, 12:1:7, 12:1:6, 12:3:5

and 12:4:4)

(III) Five component systems

Water - n-butanol - acetone - acetic acid - 5%

ammonium hydroxide (2:7:5:3:3, 2:5:5:7:3, 2:3:5:7:3)

Stationary phases

Following adsorbents were used as layer materials

Silica gel, alumina, kieselguhr, cellulose, silica gel +

cellulose (1:1, 1:2, 2:1), alumina + silica gel (1:4, 1:9,

3:7).

Apparatus

A TLC apparatus (Toshniwal , India) was used for coating

the layer materials on glass plates (20x3.0 cm) and glass jars

( 24x4.0 cm) were used to develop the plates. The home made

vacuum filtration assembly, common refluxing apparatus and hot

plate magnetic stirrer etc. were also used. Bosch and Lomb

Spectronic 20 spectrophotometer was used for the determination

of cobalt chlorosulphate.

Synthesis of metal chlorosulphates

Anhydrous metal acetate (5 gm) of Ni, Co, Zn, Mn, Fe or Cu

was taken in a reaction vessel and an excess of chlorosulphuric

-35-

acid was slowly added in to the vessel. When the reaction

subside, the contents were magnetically stirred for 12 h. The

precipitate so obtained was vacuum filtered, washed several

times with chlorosulphuric acid, dried to a constant weight and

the resulting solid was kept under dry conditions.

Thin layer chromatographic separation

Silica gel, alumina, cellulose, kieselguhr, alumina +

silica gel (1:4, 1:9, 3:7 w/w) or silica gel + cellulose (1:1,

1:2, 2:1 w/w) was mixed with double distilled water in 1:3

ratio and shaken for 5 min. The resulting slurry was coated

immediately on to 20x3.0 cm glass plate with the help of TLC

applicator to produce a layer of 0.25 mm thickness. The plates

were dried at room temperature and activated in an electrically 0

controlled oven at 110±2 C for one hour. After activation the

plates were cooled to room temperature and kept in a closed

chamber until use.

To prepare the impregnated TLC plates a suitable solvent

was substituted for water in the slurry. The plates were

prepared by using the resultant slurry under the same

experimental condition as described for unimpregnated plates,

followed by activation at 80 C for one hour.

Procedure

20 pi of metal chlorosulphate solution was spotted on the

chromatoplate with the help of micropipette the spot was

developed in desired solvent system by ascending technique.

-36-

The solvent ascent was fixed to 10 cm in each case. After the

development is over, the plate was withdrawn from the glass jar

and dried. The metal chlorosulphate was detected using

appropriate detection reagent.

Spectrophtometric determination

To the cobalt chlorosulphate in DMF solution containing

0.065 to 0.65 mgs of cobalt is added to 0.1 ml of a mixture of

saturated potassium thiocyanate in acetone and water (6:1)

and the volume is made up 10 ml with DMF. After thorough mixing

the solution was left for complete colour development for about

5-10 minutes. The absorbance spectra of this solution was

measusred against reagent blank over AOO-700 nm. It gives

maximum absorbance peak at 620 nm ( Xmax). The colour produced

with cobalt chlorosulphate was stable and proportional to

cobalt chlorosulphate concentration .

The developed spectrophotometric method was applied to

determine the cobalt chlorosulphate after the chromatographic

separation from other metal chlorosulphates. For this purpose

different volumes (0.01-0.1 ml) of chlorosulphate solution

containig 0.065 to 0.65 mgs cobalt were spotted on the

chromatoplates. After the spots were completely dried 0.064 mg

of nickel were spotted on the same spot on the chromatoplates

and the plates were redried at room temperature. The dried

plates were developed in acetic acid - ethyl alcohol - acetone

(3:1:6) solvent system. A pilot plate was also run

simultaneouly to locate the position of cobalt chlorosulphate.

After the development, the area covering the spot was scrapped

-37-

from the plate and the cobalt chlorosulphate was extracts with

DMF. The adsorbent was separated from the solute and washed

with DMF to ensure complete extraction of cobalt

chlorosulphate. To the filtrate, 0.1 ml of reagent (mixture of

saturated KSCN in acetone and water in 6:1 ratio) was added and

the total volume in each case was maintained to 10 ml using

DMF. The solution was left for complete colour development for

about 5-10 minutes. The absorbance of developed colour was

measured against the reagent blank at 620 nm using 1 cm cells

and a calibration curve was constructed. The cobalt

chlorosulphate was spectrophotometrically determined after its

separation from other metal chlorosulphates using the following

relationships.

Percentage recovery == 100 - K

Relative error (K) = ^IZ^^ x 100 At

where Xi - amount of Co obtained after extraction from the

chromatoplate

Xt - amount of Co spotted on the chromatoplate

RESULTS AND DISCUSSION

The result of this study have summarised in Figures 1-4

and Table 1-2. The possible separations are given in Table 1

and the separation achieved experimentally are given in

Table 2.

-38-

Solvent system with no acids

In the solvent systems containing no acid, all the

complexes are either strongly adsorbed on all the

adsorbents(alumina, cellulose or kieselguhr) or produce tailed

spots. The extent of tailing increases with the increase in

concentration of ammonia in the mobile phase. The non acidic

eluents bear no practical utility in the separation of metal

chlorosulphates except ammonia- acetone (1:9) system which

produce ternary separation of Ni, Co, Mn (Fig. 1) on alumina

layers .

Acid containinig solvent systems

Contrast to non acidic solvent systems, acid containing

solvent systems, provide better separation possibilities

causing differential migration of complexes. Carboxylic acid

containing solvent systems are better than hydrochloric acid

containing solvent systems. Among the ketone containing solvent

systems, acetone systems produce more compact spots compared to

ethyl methyl ketone or isobutyl methyl ketone systems. The

development time for acetone systems is less (30 minutes

compared to the other ketone systems (1 hr). Eluents containing

methanol, ethanol or propanol produce rapid separation compared

to butanol, pentanol or hexanol containing solvent systems.

Conversely, the higher alcohol containing eluents produce more

compact and clearer spots. The nature and the concentration of

alcohol and acid in the solvent system strongly regulate the

mobility of metal chlorosulphates.

-39-

Sllica gel is found to be a better adsorbent than alumina,

cellulose or kieselguhr. Further, mixed adsorbents are better

than single adsorbents for the differential migration of

chlorosulphate complexes. Among the mixed adsorbents, alumina +

silica gel (1:4) mixed bed and cellulose + silica gel (1:1,

1:2) mixed beds are suitable for the separation of metal

chlorosulphates. The 12 - 20 % content of alumina was found

optimum in the mixture of alumina and silica gel. Hydrobromic

or hydrochloric acid containing systems deform the plates

prepaered from kieselguhr during development.

The separation possibilities of chlorosulphates of

transition metals are shown in (Figs. 1-3). Mn can be easily

separated from Ni or Co, on cellulose layers. Ni produce double

spots in acetic acid - propanol (2) - acetone (4:4:12, 5:3:12,

6:2:12) systems showing the presence of two defferent species

(Fig. 1). Mixed adsorbents are also useful for mutual

separation of Ni, Co and Mn in different solvent systems(Figl)

Co produced tailed spots in these systems on silica gel +

cellulose (1:2 or 1:1) mixed bed (Fig. 2), but Ni-Mn binary

separation is always possible in these cases. Ni can be

separated from Mn or Co very well on silica gel + cellulose

(1:1) mixed by with hydrochloric acid - alcohol (s) - acetone

(3:1:6) or acetic acid - n-butanol - ethyl methyl ketone or

isobutyl methyl ketone (3:1:6) systems (Fig. 2). However, the

ternary separation of Fe, Cu and Zn mixture is possible in

acetic acid - n-butanol - isobutyl methyl ketone (3:1:6)

systems(Fig. 3). Some other interesting separations (Ni-Co-Mn,

-40-

Zn-Cu-Fe) can be visualized from Figs. 1-3.

The cobalt and nickel down to 4.064 and 4.052 pg level can

be successfully detected on the chromatoplates using detection

reagent, saturated KSCN in acetone and water (6:1).

Spectroscopy

The result of spectroscopic determination of cobalt

chlorosulphate are given in (Fig. 4 A-B). With the optimum

conditions described in experimental part. The calibration

curve for cobalt chlorosulphate was constructed (Fig. 4A).

Reagent shows negligible absorbance at Araax (620 nm). The

absorbance gives a linear relationship in the concentration

range 0.13 to 0.650 mgs of cobalt in the chlorosulphate

solution. The maximum recovery of cobalt after the TLC

separation from nickel is 91%.

CO

C O

• H JJ

CO 1^ CC

a 0)

C/D

> i-i

CO

c i-l

(U H

01 1—1

^ • H

« CO

o

> r - l

r-<

^ c

• H

4 J

O IJ

o cu

x: H

T — 1

1

QJ r- l

X I CO

H

H x : OS

U 1

X O i

> OJ

E - ^ o X I M - H

14-1 ( 0

V)

to O

X 01 V)

1—1 - iH

a E C o o

U -H .i->

r - l CO

CO >-l 4 J CO

o; CL z : QJ

LO

U J X

0 OJ 1—1

c a O E

• H O

JJ O

CO -;;

>-i . - 1 H

CO (0 OS £!u-ui 1

a> 0) , -1

LO 2 : oc:

>> u to

c o

• H 0)

4-J CO

CD CO

^-> X. OO CU

o w CO

X CU

o <—< • H

X o s:

^ ^ s / * " ^

o^ i n

0 0 O^

O O 1 1

0^ a^ a> o o o S 'N ^

D C

1 1 • - v ^ ^

cy o vIJ .J3

o o 1 1

<!• O r^ CO

O O >*.-^^^-^

o o o o

o O f^

o o 1 1

CO

o ^

o o ^ - ^ N w ^

•r-l -i-l

z z r ^

T - t

+ •• 1—1

1—1 ^ w /

oj o; 0) 10 ClO W

o o 1—1 CO 1—1

3 O 3 f -^ - H 1—I

»-^ 1—1 t—1

01 - H CU

O en u

OJ c

-^ o C T ' •<-»

•r-H O

V — ' CO

0 ) p—1

c o o c i-> CO

ox. O JJ CO 0) ' ^

vn 1 1 • •

r - l

r—1 1—1 • •

O O f n X I ->^

y ^ ^

o a. o

1

a 0^

o s^^

c 1

/"—s

o ^ o )

o oo o N ^ ^

D o

o 1—1

o 1

i n

i n

O > w ^

• H

z

- ^ v

CNI

• • T H

v - - '

t

1—4

o c CD

4 - 1

3 X5

1

C

1

T5 • f - (

O CD

QJ

O C • r t O 4_l X J

ftJ Q;

U O < CO

^ »—( >X5

o (

o r«.

o v ^

QJ

1

, ^ o CSI

o 1

o <r o v^ .^

o u

i n

O

O 1

o T—1

o v*^^

•r-l

z

1—1

+ 01 &/)

CO C CO

• H O ^ E - ^ CTi

3 - - I •• f—1 - H » - l

CD c o ^

1

r—1

o c CO

X 4 J

CJ

E

T5 • r ^

(J CO

QJ

o c •^ o 4-1 4-) OJ C)

o u < CO

/ ^ x

o •X)

o (

o 0 0

o N — ^

QJ tx.

/"^s

i n

<N

o 1

o >a-o ^ - o u

oo

o o

1

-^ 1 - (

o \ - y

•r-l

z

1 1—1

o c CO

4->

3 X )

1

c

TJ • H

o CO

QJ O C

•r^ O 4-1 4 J

0 ) QJ

o o < CD

^^ O O

»x> o *

i n

(^ o N w ^

QJ

1 /—V

o rn

o 1

o m o

> w '

o o

C3 o

o 1

i n

1—1

o s - ^ •r-l

z

1 1—1

o c CO

a o u a

c 1

TJ •i-i

a CO

OJ o c

• H c 4.1 4.)

QJ (J

u o

^—N

o c o

1 i n

a^ o >—•

c 2 :

1 ^—N

0 0 CSI

o 1

o i n

O N«^^

o (J)

o

o 1

i n 1—1

o N ^

• H

Z

/ •~s

<r • •

i H

v . ^

1—1

o c CO

x: 4. )

QJ

E

t

•n • H

(J CO

OJ

o c •r-( O 4-> 4.)

Q) QJ

U O < (0 < CO

- ' • • ^

o a o

1 i n

(7^

o N w ^

3 CJ

1 /—V

i n

i n

O 1

O x> O

•— o

CJ

o CO

o 1

i n

v j

o •v . - '

• r ^

Z

X—^

r^ • •

f ^

-

::<:: T. CO 1—1

t

.—1

o c CO

4 - 1

3

x> 1

c 1

1—1

o X

"- ro O^

o » oo

o o S ^ '

c 2 :

1 / • • v

i n

v ^

o 1

o oo o N—^

CJ t .

o o

1

0^ CN

O N — ^

o u

^ - s

<»• • •

i H

v_^

, 1—1

o c CD

4 J

c OJ ex 1

c 1

X ) • r ^

u CO

0) o c

•r^ O 4 J 4 J

OJ QJ

U 0 < : CD

-^ m o O

1 0 0

a o — c 1

/•"s i n

vr> o

1

o CO

o N — ^

QJ

[ 1 4

/ ' V

O

o 1

c fNJ

o N ^ ^

o o

1

r—1

o c CD X OJ

X

c 1

T> • H

u CD

OJ

o c ..- o 4-) 4.)

QJ OJ

O U ( <C CD

• 4 - 1

o a to

OJ

X 4 ->

U . 4

o 4->

c o u

U-l

oo c r-l

CD OJ

- 4

4 - 1

o

u-x:

H

J X ( »*

• 4 ^

o a (0

OJ X 4-1

li.4

o 4 J

c o I-l

u-l

oo c

• H 1—1

• H

CO u

4->

V4-I

o tu

OS

II

H o: •Jc

0) c o 0)

o CO 1

r - (

4-1

a 0) o X (U Cfi OJ CO CO

o CO

J-) CO S-i

(^ c

• H

0) M (U U:

0) w CO

-C a fl)

1—1 • H

^ o F=

U~l

o

w 4->

c OJ

c o t i b o o

OJ 4 : H

CO M

CT.

• • T-i

c • H

OJ u Q)

> 4-1

c <u c 0 t x td (J 0

01 r T : 4-1

(1) ^4 aj

c ps

F= cu

4-1 m > m

OJ 4-1 CO

—i

a m o o - I

CO 4-J QJ O D

r-H q CO o > r-l •u -:« CO H M p i CO I a ( (u pd

C

o CO

<

CO

CO

P-i

QJ

o

CM CN O

o cu

^4

o

0 0 0 0 1 0 O l i i i i l l l I I I I I I

o o c N L O o o ~ i L n v ^ c T > CO a^ en L O ( T v c x D O L n L n ' j ^ L O L n o i ^ < i ' L n o r - ~ - L o c N • • r ^ C T i • • ^ a^ • cx) ' r ^ - v ^ ^ o c o c M o o c N J ^ - - o ^ ^ - ~ c o c J ^ ^ c x ) o ^ ^ ( v ^ c 3 ^

T H T - I ' ' T H O ' ' 0 - O ' -' - o o -' - o o —' ov-'O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 C C U l l C O I I C I C I l l l i l l l l l l l l l l l l l

S f a c M ^ s l O m c T ^ S r ^ S c x ) c N i ^ c N < n c N L n i n m c ^ u - i c » o c N i c o c n c x ) C ^ C ^ i O r^CT' CTv 00 CJ^^X)(3^lJ~lC^^<)•(J^~^CJ^00CT>^--CT>Lrl00^~-O^

( ^ • • ! - l l • • \^ ' U • O O T H O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

o c c u c o o o ^ o ( u o j o ) a j D C O c o c q a J O C D C O O J Q J C O S tL, S O 0^ O (J) CJ [ t , tL4 t u tL4 O S O S O S S pLj CJ S U S U Pu [14 2

O I I I I I I

O CN -cr v£i r~. CXD v£> • O Osi O O - O iH 0 0 0 0 0 O O O CN O O O

o • • • • o ^ - ' O O O o - ^ - ' O o 0 0 0 0 0 0 0 0 0 0 0 0 O I I I I C I I I I I I I I I I I I I I

c j c ^ v D ^ i S L n S CN < | - m c N o ^ CNI -^H CM m c» o O" 0 ^ 0 0 O on , r H < t T - l < fOs l ,H •M CN en en r~i T-\

u • ' ' • u • • • . . . . . • . • • • • 0 0 0 0 0 0 0 o 0 0 0 0 0 0 0 0 0 0 0 0

•H D -H q -H -H -H -H -H -H -H D -H -H -i-l -H -H -H -H -H Z O 2 ; Nl Z Z 2 2 2 Z Z U 2 : 2 Z Z Z Z Z 2

CO q

•1-1 E a

i-H CO

CU q

OJ 0 q 4-1 0 <u

4-1 0 cu CO 0 1 CO r-i 1 0

r H q 0 CO q a, CO 0

X M 4J (X <U i E q

TJ 13 •I-l -H 0 0 CO CO

0 0 •H -H 4-) 4-1

cu q

CU q 0

4-1 Q) 0 CO 1

r-l 0 q CO

4-1 q cu

I-H CU ftC

CO 0

• H , -1 • H CO

<U q 0

4-1

cu 0 CO 1

1—1 0 q CO Ch 0 u

CU q 0 4-1 (U 0 CO

1

ex Oit -H 1 q

1 q

cw 4-1

cu 0 CO

1

cu <u 1—1 0 0 u

• H 0 CO

0 • H 4-1 (U 0

• iH 0 CO

CJ • H 4-1

0 q CO

4-1 q

cu CO 0

1—1 3

1—1 I-H (U 0

CU q 0

4-1

e x cu

q

1

0 CO

1

CU 1—1 1—1 0 tJ» 0

<; <! ix; <c <; m; K

+ ,—1 0)

iH (N

i H

CU c>0 to

0 CO I—I 0

• H 1—1 • H CO

t ^

s oa 1—1

1

.—1 0 q CO

4-1 3 ^

1 q

1

1—1 CJ ffi

3 i-H 1—1 CU 0

T - l

<u q 0

4-1 CU 0 CO 1

I-H 0 q CO

4 J 3

r Q 1 q 1

T H

CM

<U q 0

4-1 CU 0 CO 1

r—1 0 q

CO 0

• H

• H CO

+ CO q

• H E 3

r—1 CO

(U q 0

4-1 CU 0 CO 1

CO •—1 4-1 q cu

0 q CO

ax: 1

q 4-1 cu 1

T) 13 TJ • H 0 CO

0 • H 4-1 CU 0

•I-l 0 CO

u • H 4-1

cu 0

• H U CO

0 • H 4-> <U 0

< < <

f~-

• • r o

^ CU M

CU q 0

4-1

cu 0 CO 1

r—1

+ r—1 CU

T H

•• T H

CU b O CO

0 CO r - l 0

• H 1—1 • H CO

CU q 0

4-1

cu 0 CO 1

0 r H q CO

4-1

0 q CO

3 X 1 / 3

1 q

4-)

cu E 1

U X I • H 0 CO

0 • iH 4-1

cu 0

• H 0 CO

CJ • iH 4 J CU 0

<; <:

3 r H 1—1 Q) 0

CU q 0

4 J CU 0 CO 1

1—1 0 q CO 4-1 3

r£3 1 q

X) • H 0 CO

0 • H 4-1 CU 0 <

cu q 0

4-1 CU 0 CO 1

1—1 0 q CO

4-1 q cu a, 1 q

1 3 • H 0 CO

CJ • H 4-)

cu 0 <

^ s w

1

1—1 0 q CO 4-1 3

,n 1

q

13 • H 0 CO

0 • H 4-1

cu 0 <

CN

• • T H

CU q 0

i j cu 0 CO

1

1—1 0 q CO

4-1 q cu

a q

1

1—1

a a:

T - i

•• O-l

i ^ S

w 1

r H 0 q CO

4-) 3

^ 1 q

' 13 • H 0 CO

0 • H 4-1

cu 0 <

CO 0

•H i H • H CO

+ CO q

• H E 3

^ CO

cu q 0

4-1

cu 0 CO 1

f H 0 q CO X CU

x 1

q

X) • H 0 CO

CJ • H 4-1 CU 0 <c

CTv -<f

.. .. T H T H

r H CU C»0

CU q 0

4-1

cu 0 CO 1

i H 0 q CO X cu

r C 1 q

X I • H 0 CO

0 • H 4 J

cu 0 <c

-43-

Caption for Figures

Fig. 1. R values of Mn, Co and Ni metal chlorosulphates on

different adsorbents.

Fig. 2. Rp values of Mn, Co and Ni metal chlorosulphates on

mixed adsorbents.

Fig. 3. Rp values of Fe, Cu and Zn metal chlorosulphates on

different adsorbents.

Solvent system showing separations of metal chlorosulphates in

Figures 1-3

S^ - Ammonia - methanol (1:9); S^ = (1:1), S^ = (9:1)

S, - Ammonia - acetone (1:9), Sr = (1:1), Sr = (9:1)

S-, - Acetic acid_propanol-(2) - acetone (4:4:12)

Sg - (5:3:12), Sg = (6:2:12), S^Q = (3:7:10)

S^^ - (5:6:9), S^2 = (5:7:8)

S o - Acetic acid - n-butanol - IBMK (3:1:6)

^14 - HCl - n-butanol - EMK (3:1:6)

S^5 - HCl - n-butanol - IBMK (3:1:6)

S^^ - Acetic acid - methonol - acetone (3:1:6)

S.- - Acetic acid - ethanol - acetone (3:1:6)

S r, - Acetic acid - n-propanol - acetone (3:1:6)

S.Q - Acetic acid - butanol - acetone (3:1:6)

Syr. - Acetic acid - n-pentanol - acetone (3:1:6)

S^^ - Acetic acid - n-hexanol - acetone (3:1:6)

S^^ - HCl - methanol - acetone (3:1:6)

S T - HCl - ethanol - acetone (3:1:6)

S^, - HCl - n-propanol - acetone (3:1:6)

S cr ~ HCl - n-butanol - acetone (3:1:6)

S^^ - HCl - n-pentanol - acetone (3:1:6)

S -, - HCl - n-hexanol - acetone (3:1:6)

S2g - HCl - DMSO - propanol-(2) (1:1:1)

S29 - (2:1:1), S3Q - (1:2:1), 83^ - (1:1:2)

Symbols used

Compact spot (R-, - Rrp < 0.3)

Tailed spot (R^ - R^ > 0.3)

Fig- 4 Spectrophotometric determination of Co chlorosulphate.

- 4 4 -

Si l ica ge l •+ C e l l u l o s e (1 : 2) Sil ica ge l + Ce l l u lose ( 2 •. 1 )

FIG. 1-SOLVENT SYSTEMS

- 4 5 -

Si6 S,7 Si8 5i9 S20 S21 Sil ica gel + Cellulose (1:2)

5i3 Si/j Si 5 Alumina + Silica gel (1 :A )

S16 5l7 5]8 Si9 S20 S21 Sis Si7 S18 Si9 S20 52i Alumina + Silica gel (1 :A ) Silica get + Cellulose (1 :1 )

522 ^23 ^2^ 525 ^26 S27 ' ' 5i3 5IA 5 ^ Si l ica gel + Cellulose (1:1) Silica gel + Cellulose (1:1)

FIG.2 -SOLVENT SYSTEMS

- 4 6 -

Alumina -t S i l ica gel ( 1 :A )

Fe

a.

Cellulose

Alumina 4- S i l i ca ge l ( 1 : 9 ) Ce l lu lose

FIG.3-S0LVENT SYSTEMS

- 4 7 -

0.5

0.5 0/

^ O.A o

o

5 0-2

n 1

- ( A ) Calibration Curve ^

X .y •/^

^ 1 1 1 1 1 1

0.1 0.2 0.3 O.A 0.5 0.6 0.7 mg of Co

0.6

0.5 u c O.A o XI

o 0.3

< 0.2

- (B) Recovery Curve

0.1 0.1 0.2 0.3 O.A 0.5 0.6 0.7

mg of Co

FIG.4

-48-

REFERENCES

1. S.A.A. Zaidi and Z.A. Siddiqui, Acta Chim Acad., Sci. Hung.,

92, 57 (1977).

2. S.A.A. Zaidi and Z.A. Siddiqui, J.Inorg. NucI. Chem.,

38, 1404 (1967).

3. R.C. Paul, D.S. Dhillon, D. Kanwar and S.K. Puri, J. Inorg.

Nucl. Chem., 39, 1011 (1977).

4. S.A.A Zaidi, Z.A. Siddiqui and N.A. Ansari, Acta Chim Acad.

Sci., (Hung), 93, 395 (1977).

5. S.A.A. Zaidi, Z.A. Siddiqui and N.A. Ansari, Acta Chim.,

Acad. Sci., (Hung), 97, 207 (1978).

6. S.A.A. Zaidi, Z.A. Siddiqui and N.A. Ansari, Bull. Soc,

Chim. (Fr.) 11-12, 82 (1979).

7. Z.A. Siddiqui, Lutfullah and S.A.A. Zaidi, Bull, Soc.

Chim., (Fr.) 5-6, 185 (1980).

8. Z.A. Siddiqui, Lutfullah, S.A.A. Zaidi and K.S. Siddiqui,

Bull. Soc. Chim., (Fr.), 5-6, 228 (1989).

CHAPTER - I I I

SOME OBSERVATIONS ON THE MOBILITY OF RARE EARTH BENZOATES AND

CHLOROSULPHATES ON SILICA, ALUMINA AND CELLULOSE LAYERS

Thin layer chromatography has been a popular separation

technique for a wide variety of organic and inorganic

substances because of its distinct advantages such as minimal

sample clean-up choice in solvent selection, flexibility in

sample detection high sample loading capacity and low cost. The

increasing utilization of rare earths (REs) and interest in

their geological and environmental roles (1,2) has renewed the

need of applying chromatographic methods for both qualitative

and quantitative determination of REs in actual samples. The

suitability of TLC procedures in the analysis of RE metals has

been demonstrated by several workers (3-15) using a variety of

stationary phase, eluents and detection methods. Excellent

separations of REs has been achieved on silanised kieselgel (7-

11, 16, 17). Ishida et al. (18) developed a simple TLC method

for separation of REs on silica gel layers using aqueous

ammonium nitrate solutions as eluents. An ion-exchange

mechanism was proposed to account for the decrease in Rp values

with increasing atomic number of REs. The results of these

workers were similar to those achieved by reversed phase TLC

using bis (2-ethyl hexyl) phosphate,( HDEHP) - HNO^ or HDEHP -

HCl on silica gel (19-22) but opposite to that obtained by

normal phase TLC on silica gel with HDEHP in CCl, (23) or

silanised kieselgel and organophosphorous compounds in HNOo (7,

16, 17). Separation of REs have also been achieved on adsorbent

-50-

layers impregnated with high molecular weight amines (24) or

organophosphorous compounds (25) which are capable to interact

reversibly with REs. Alternatively, separations have been

realized by incorporating these complexing agents in the mobile

phase. The mobile phases consisting of aqueous mineral acids,

mixtures of organic polar solvents and mineral acids or

mixtures of mineral acids and ammonium salts have been utilized

for the separation of REs on modified cellulose layers (26-28).

Several compounds of RE elements such as benzoates (29),

chlorosulphates (30,31) and fluorosulphates (32,33) have been

synthesized and characterized, but no work has been cited on

chromatographic studies of these inorganic complexes. More

recently centrifugal partition chramatography (34), circular

TLC (35), TLC - ICP - AAS for preconcentration and subsequent

determination of REs from geological samples (36), TLC of REs -

cc- hydroxy isobutyrato complexes on C.o bonded silica (37) and

HPTLC of rare earth tetraphenyl porphine complexes on C „ and

NH2 plates (38) procedures have been proposed for rapid

quantitative and qualitative analysis of REs. However, non of

these studies provide any information about the thin layer

chromatographic behaviour of RE benzoates.

The properties of metal ions are determine by their size

and charge and since the REs are typically almost identical in

size and charge, their chemical properties are almost similar

and thus their mutual separation is difficult. Therefore the

examination of chromatographic behaviour of RE benzoates

-51-

and chlorosuLphates are interesting inorder to understand the

effect of associated part with typical hard acid e.g. RE cation

M (ionic size 8.5 - 10.6 nm) tending to form ionic bonding.

The present studies reveals the mobility of some RE benzoates

and chlorosulphates on different adsorbent layers and selective

separation of La from other REs.

EXPERIMENTAL

Reagents

Ethanol (Bengal Chemicals and Pharmaceuticals); silica

gel, oxalic acid, acetone, thionyl chloride, sodium benzoate

(E. Merck, India); ammonium chloride, ammonium nitrate,

kieselgel, cellulose, ethyl methyl ketone (EMK), isobutyl

methyl ketone (IBMK), dimethyl sulphoxide (DMSO), propanol,

benzene, oxides of lanthanum,cerium,neodymiura, gadolinium,

samarium, europium, ytterbium and terbium (Central Drug House,

India); n hexane, cyclo hexane, acetic acid, formic acid and

ammonia (Qualigens fine Chemicals, India); butanol (Sarabhai

M. Chemicals) and chlorosulphuric acid (s.d. fine

Chemicals) were used as received. Other reagent used were also

of anlytical grade.

Test solutions

1% aqueous solution each of La, Ce, Nd, Sm, Eu, Gd, Yb or

Tb benzoate in dil. HNOo and chlorosulphate in DMF were used

for chromatography.

-52-

Detection reagents

1% alcoholic solution of 8-hydroxyquinoline (oxine) or

dilute aqueous solution of arsenazo (III) was used as the

detection reagent for all RE benzoates and chlorosulphates.

Chromatographic systems

some of the selected chromatographic systems used for this

study are listed in Table 1.

Synthesis of rare earth benzoates

About 2 gm of RE metal oxide (La, Ce, Nd, Sm, Eu, Gd, Dy

or Yb) was mixed with 5 ml of water to make a paste followed by

dissolution of the resultant paste in 6 ml of 6.0 M HCl. The

solution was neutralized to incipient precipitation with 1 N

NH.OH adjusted to p^ 2 with 1 M HCl. The solution was diluted

to 200 ml and warmed to near boiling and then treated with 40

ml 1 M sodium benzoate over a period of 1 h. The mixture was

digested for about 4 h and then cooled, filtered, washed to

make free from chloride ions and vacuum dried. The product was

dehydrated at 85°C.

Synthesis of rare earth tris (chlorosulphate), M(S0TC1)O

The dehydrated metal benzoate (5 gm) was added in portions

of excess chlorosulphuric acid (30 ml), kept in a closed

reaction vessel and the temperature of the reaction mixture was

kept below 40°C. The reaction was very vigorous which was

allowed to subside before the solution is magnetically stirred

for about 6 h. The resultant solid compounds was vacuum

filtered, washed several times with chlorosulphuric acid

-53-

followed by final washing with thionyl chloride and dried under

vacuum at 60-80°C to a constant weight.

Preparation of TLC plates

Thin layer chromatographic plates for this study were

prepared as described in Chapter-II

Chromatography

The chromatography was performed in 24x6 cm^ glass jars.

RE benzoate and chlorosulphate sample spots (10 JJI in volume

each) were applied to a TLC plate about 15 mm from one end on

a marked line with the help of a lambda pipette and then

allowed to dry in air. The air dried plates were developed to

100 mm from the point of application by ascending technique at

room temperature using appropriate mobile phases. After

development the plates were dried at room temperature (30^) and

subsequently the positions of the RE benzoates or

chlorosulphates on the plates were vizualized by spraying with

the detection reagent [arsenazo (III) or 8 hydroxyquinoline] .

For the separation of RE benzoates or chlorosulphates solution

mixtures containing 10 pi of each separating RE benzoate or

chlorosulphate were spotted on TLC plates. The spot was

completely dried in air and the plates were developed with the

desired mobile phase. After development the plates were

withdrawn and the resolved RE benzoates or chlorosulphates were

detected as clearly observable spots on air dried plates after

spraying with detection reagent.

-54-

RESULTS AND DISCUSSION

The results of this study are summarized in Tables 1-4.

The possible separation of RE benzoates in some selected

chromatographic systems are shown in Table 1. From which it is

evident that La can be selectively separated from other REs. Dy

and Nd were also clearly separated from Ce and Eu. 8-

hydroxyquinoline and arsenazo (III) were used to detect the

resolved spots of REs. Arsenazo (III) is applied as a dilute

aqueous solution to the plate followed by gentle heating. The

lanthanide benzoates and chlorosulphates appear as green spots

on a pink background. The spot detected by methanolic solution

of 8-hydroxyquinoline is slightly yellowish. Though arsenazo

(III) produces more intense spots, 8-hydroxyquinoline being

cheaper may preferred.

La benzoate show a variable mobility gives R^ from 0.1 to

0.90 in different chromatographic systems, whereas the mobility

of other RE benzoates show a little variation. Out of the many

combinations of stationary and mobile phase examined for the

effective separation of RE benzoates and chlorosulphates, a few

were found suitable (Table l) for the possible separations,

because of the pronounced chemical similarities of indivi­

dual members.

According to some preliminary experiments RE benzoates and

chlorosulphates showed some mobility from the point of

application on the TLC plate with organic and aqueous eluents

such as ethanol, methanol, propanol, benzene, cyclo hexane, n

hexane, IBMK, ammonium hydroxide, copper acetate etc. The Rp

-55-

vaLues of RE chlorosulphates in various chromatographic systems

are shown in Table-2 from where some important separations may

be visualized.

The sequence of separation in TLC influenced by a variety

of factors including the separation mode (normal or reverse

phase, cation of anion exchange) and the composition of the

stationary and mobile phases. The data summarized in Table-3

and 4 indicate that both trends i.e. increase in Rp with the

increase in atomic number (Table-3) and the decrease in R^

with the increase in atomic number (Table-4) occur within the

lanthanide series. Such behaviours about the retention of

lanthanide ions versus their atomic number for various modes in

TLC have been reported by several workers (39-42). The overall

trends of decrease or increase in mobiliy versus atomic number

have been explained in terms of lanthanide contraction on

metal- ligand stability constant and the Lewis acidity of the

metal ion. Both ion-exchange (18) and reversed -phase partition

mechanisms (25,43) have been proposed for explaining the

decrease in Rp values with increasing atomic number. In the

present case the observed decrease or increase in retention of

REs as a function of atomic number may be attributed to the

stability of lanthanide benzoates and chlorosulphates, the

descrete changes in coordination number and thermodynamic and

transport properties associated with the different f-electron

configurations.

The results of this study establish the utility of mixed

adsorbent layers for selective separation of La, Dy and Nd from

some of the associated REs.

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CO

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1

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CO

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^ IT'

T3

4 3

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T3

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>^ Q

D W

T) 0

a w

D W

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T3 0

D W

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CO 00 E

to

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O

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E CO

E CO

X )

QJ . . OOCJ^

CO

O

CO

1 ^

CvJ c ^ CO

QJ C 0 4-1 QJ 0 CO

i i i S pa

QJ C QJ N

c QJ

^

i^ S pa

QJ

c 0

j _ )

QJ CJ CO

M s pa

QJ

c QJ M

c QJ

^

i i i T. CQ

0 CN

ffi

• •

C CO X 0

•H Q

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QJ C QJ N

c QJ

rO

M T. pa

0

c CO

4:: 4-> QJ E

i^ S pa M

QJ C QJ Nl

C QJ

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M s pa '—1

.—1 0

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M 2 CQ h-1

-60-

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