Historically, water testing regulations were stringent but not precise enough to yield accurate results. This was until the platinum cobalt method was developed in 1892 by a chemist named Allen Hazen, which helped to enhance the precision and standards of water testing. This blog post will look at the step-by-step process of the platinum cobalt method used for water testing.
A Brief History of Water Testing
When carrying out water testing, the color of the water is often analyzed to deduce the level of contamination and determine the overall quality of the water.
Previously, water and wastewater were evaluated against a grading called water-white, in which scientists analyzed the turbidity of water that appeared to be clear. This technique was inaccurate and built upon over time, which led to a number of new definitions and terminologies that were not correct. As a result, there was no universal standard for how water-white testing was carried out.
What is the Platinum Cobalt Method?
The platinum cobalt method is also referred to as the Pt-Co scale or the Apha-Hazen scale and has successfully resolved the problems that were related to water-white. The platinum cobalt method is a precise method which utilizes spectroscopy to test impurities in water.
Using a spectrometer with an ultraviolet-visible (UV/Vis) light source enables analysts to accurately and precisely identify contaminants by measuring the yellow hue's strength in water sources against the platinum cobalt scale. The Pt-Co scale uses Color Units (CU) from 0 to 500 parts per million (ppm), and analysts will use a certified reference material as a color unit standard to ensure their results are accurate.
Why Are Certified Reference Materials Required?
In any scientific testing, accurate test results are vital for safety, decision making and meeting regulatory standards. In terms of water testing via the platinum cobalt method, certified reference materials (CRMs) are used to calibrate the UV/Vis spectrometer to ensure accurate output signals.
Although suppliers can produce their own reference materials, CRMs should be purchased from a reputable supplier to ensure that your instruments are calibrated with the correct materials and follow the required method. Once your device is calibrated, it will guarantee that your results are reliable, repeatable and credible.
Certified Reference Materials from Inorganic Ventures
When carrying out the platinum cobalt test, analysts must use precise starting materials and accurately calibrated instruments to ensure credible results are achieved. In this case, the starting materials will be potassium chloroplatinate and cobalt chloride hexahydrate.
Inorganic Ventures specializes in producing CRMs and standards for instrument calibration and validation protocols. We are re-launching our Platinum Cobalt Color Standard (PT-CO-500ML), a CRM developed through extensive chemical expertise, as a stock product.
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Platinum Cobalt Color Standard -- Part Number: PT-CO-500ML |
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ANALYTE |
µg/ML |
METHOD |
NIST SRM# |
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Platinum Cobalt Color Units |
500 CU |
Nominal (from ASTM D1209 – 05 Method) |
N/A* |
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Cobalt, Co |
250 |
ICP Assay |
3113 |
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Platinum, Pt |
500 |
ICP Assay |
3140 |
*Measured absorbance data determined using a spectrophotometer verified with NIST SRM 2034 & NIST SRM 931h are provided on the Certificate or Analysis. Absorbance data obtained using an optical glass cell with a 50mm path length per Standard Methods 2120C.
Some of the benefits of our Platinum Cobalt Color Standard include:
- Available in 500mL size
- Five-year shelf life
- Reliable and consistent quality
If you would like more information on our Platinum Cobalt Color Standard or any of our other products, please do not hesitate to get in touch, and a team member will contact you as soon as possible.