Development of highly stable solid phase reagent strips for the detection of Magnesium
Hardness using eXact® Micro photometers
By By Balaji Tatineni, Ph.DBalaji Tatineni, Ph.D
PITTCON-2014,PITTCON-2014, Abstract # 760 - 5Abstract # 760 - 5March 03, 2014, 03:05 PMMarch 03, 2014, 03:05 PM
Room S502aRoom S502a
• Water hardness is caused by the presence of salts dissolved in water, primarily Calcium and Magnesium.
• It causes the formation of scale during water boiling and bad soap foaming.
• These species also account for inorganic scaling and fouling of water samples.
What causes water hardness?
• Carbonate hardness – called temporary hardness caused by the presence of carbonates, bicarbonates and hydroxides of Calcium and Magnesium.
• Non carbonate hardness – caused by the presence of Ca2+, Mg2+ and other cations like: Al3+, Fe2+, Fe2+, Cu2+ and anions such as Cl-, SO4
2-, NO3-. These ions do not
decompose and do not precipitate during water boiling.
• General hardness – is a combination of Calcium, Magnesium and other ions.
How can we divide water hardness?
Types of water hardnessTemporary hardness (Alkaline Hardness):• Caused by the presence of bicarbonates,
carbonates and hydroxides of Calcium and Magnesium.
Permanent hardness (Non Alkaline Hardness):• Caused by the presence of sulfates,
chlorides and nitrates of Calcium and Magnesium.
Benefits of hard water• Good for health.• Calcium good for
healthy bones and teeth.
• Magnesium good for effective metabolism.
• Reduces prevalence of heart diseases and hypertension.
What are the disadvantages of hard water?
Domestic:• Affects cleaning ability of soap.• Consumes large amount of soap and
detergent for washing.• Short life of cloths due to deposition of salts in
fabrics.• Decreased life of cisterns and pipes.Industrial:• Causes "Scaling" inside the transport water
pipes. • Hard water in turbines and heat exchanger
pipes will be corroded. • Disturbance of dying process.Health:• Lead to stomach disorders. Especially
Magnesium Sulphate can weaken the stomach permanently.
• Discoloration of foods.
Removal of HardnessTemporary Hardness:• Boiling• Addition of limePermanent Hardness:• Addition of lime• Addition of Sodium Carbonate• Base exchange method / Permutit process
The scale of water hardness
Classif ication mg / L Grains per Gallon
Soft <17.1 <1
Slightly Hard 17.1-60 1-3.5
Moderately Hard 60-120 3.5-7
Hard 120-180 7-10.5
Very Hard >180 >10.5
Testing for HardnessPublic water supplies• Operator needs to provide annual water
quality reports, called as consumer confidence reports.
Private water supplies• Suppliers has to test the water hardness
using government or private labs or test kits or strips or using portable photometers.
COLORIMETRIC TESTSFour basic photometric methods used:
1) Digital Photometer & Reagent: liquid, powder, tablet and reagent strip
2) Colorimetric titration: (counting drops and digital titration)
3) Comparator color test that uses a reagent: liquid, powder, tablet, or reagent strip (test tube and comparator color chart)
4) Test strips
About Photometry• Analytical Chemists use photometry because the tests are uncomplicated and give accurate results.
• Photometry has been used for analysis of various parameters such as hardness, Iron, and Chlorine. For field analysis, a visual photometer was developed commercially.
• Since the 1930’s, when Electronic Photometers or Photometers were introduced, a variety of improvements make them a convenient tool for today’s water analysis.
Typical Photometric Method
• Typical Supplies:• photometer and cover• Two glass photocells /
caps• Reagents (powder,
liquids or tablets)• Wipes• Sampling Beaker
Photometer Changes• Software allows the meter to read the optical density (OD) and to convert the OD as ppm or mg/L of reactant.•Long Life LED’s - replace filament lamps - increases reliability.•Solid state light sensors - replace light detectors - increases accuracy.•Battery operation allows portable field meters.•Waterproofing extends the life expectancy from months to years.•Digital display makes results easier to read.•Plastic cells replace glass cells to reduce breakage.•Matched cells are eliminated by modifying the test procedure.• Micro electronics reduce price (below $300), reduce size and increase sophistication. •Stable and convenient reagent delivery methods improve accuracy and reliability.
• A new development in colorimetric testing with the use of a waterproof Photometer with a 4 ml “cell” or cuvette permanently fixed or welded into the meter.
New Colorimetric Test
• In addition, the colorimetric reagents delivered by a reagent strip (eXact Strip) into the “cell”. This development is available for field testing for oxidizing agents like Free Chlorine (OCl) and for metals like Iron (Total) and Hardness (as CaCO3). •Today I’ll present the development for Magnesium Hardness testing with the Micro 20 meter.
New Colorimetric Test
Chemistry • Chemistry is reaction of Phthalein purple with
Magnesium in the presence of buffer and masking agents.
• Optimized the concentration of Phthalein purple, buffer reagents and masking agent.
• Optimized concentration of reagent were made in the form of reagent strip using our patented reagent strip technology.
New Colorimetric Test• The strip demonstrates high precision and
accuracy, and a long shelf life. • The developed strips are used for real
time analysis in our eXact® Micro photometers.
• No separate sample cell is required.
• The reaction time is immediate.
Once the parameter is selected, rinse the cell with the test sample for three
times and fill the cell with the test sample.
Insert reagent strip into cell and press READ. Meter begins 20-second countdown and during
countdown, move strip back & forth to release the reagent from the strip.
Remove and discard strip. Meter automatically reads result and stores in memory. Rinse the
meter thoroughly with the test sample.
Absorbance spectra of Phthalein Purple with various concentrations of Magnesium
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
400 420 440 460 480 500 520 540 560 580 600 620 640 660
0 ppm
50 ppm
100 ppm
200 ppm
300 ppm
400 ppm
500 ppm
600 ppm
700 ppm
Wavelength, nm
Absorbance
Calibration graph with varying concentrations of Magnesium
y = 0.0017x
R2 = 0.9866
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 100 200 300 400 500 600 700 800
Mg Concentration, ppm
Absorbance
Conclusions• Can measure the Magnesium hardness in
various samples from the range 1 to 700 ppm of Mg as CaCO3. Calculated detection limit is 3.58 ppm.
• Applicability of the strips for various kinds of water samples such as sea, aquarium, drinking, coolant, tap and waste water samples were studied.
• Most of the ions are not interfered in the detection.
• Demonstrates high precision, accuracy and selectivity, and a long shelf life.
• No separate sample cell required.
Questions?Dr. Balaji Tatineni – Principal Scientist
[email protected] www.sensafe.com
DOWNLOAD THIS PRESENTATION: http://www.slideshare.net/sensafe
The authors would like to express our thanks to Mr. Howard Ray, Mr. James Rapley, Mrs. Corlyss Lewis and Ms. Ashley Calhoun
for their help during the various stages of this work.
Top Related