Why don't you use ion selective eelctrodes? It is very specific and easier!
There are various heavy metals which may be present in drinking water. Presence of heavy metals is a very sensitive item in drinking water because these can be toxic also. However for qualitative and just approximate purpose colour comparators are already utilized.
Colorimetric methods are (generally) not specific and not sensitive. Thus generally not applicable for quality control of heavy metals in drinks and food.
To be very honest, colorimetric methods are not suitable for heavy metal measurement in water. It has low detection limit and diffrent combination of chemicals are required for measurement of different heavy metals. Some of the chemicals researchers have used are not gettable easily in every labs.
You should use AAS or ICPMS for measurement of heavy metals. They can detect or measure heavy metals in present in 0.5ppb or even in lesser quantity depending on the instrument.
Colorimetric methods are not specific and sensitive method for analyzing heavy metals and most of the time detection low contents would not be possible. Thus generally not applicable for quality control of heavy metals in drinks and most of food stuffs.
I agree entirely with the last 3 corespondents. Colorimetric methods for heavy metals are generally based on selective formation of a coloured complex (often with dithizone) in an organic solvent with the selectivity (what there is of it) being highly dependent on close pH control and often a complex series of back extractions.
The cost of chemicals will be high and the environmental cost of the solvent use will be significant.
For drinking water concentrations you would generally need ETA-AAS if you are using AAS so be aware of significant matrix interferences. ICP -OES is not sensitive enough for most elements so ICP-MS would be the best choice.
Please read these files, will explain every thing to you and what best for low concentration of pollutants.
and the uploaded files has the standard methods and the other has the standardization on the atomic machine.
i hope it can help.
https://www.perkinelmer.com/PDFs/Downloads/BRO_WorldLeaderAAICPMSICPMS.pdf
https://www.agilent.com/cs/library/primers/Public/Primer_Environmental_elemental_analysis.pdf
https://www.perkinelmer.com/lab-solutions//resources/docs/APP_NexION300D-US-EPA200-8-Drinking-Water.pdf
There are many methods of colour developments in colorimetric determinations for heavy metals; as many as the metals themselves. All these methods were no longer in vogue due to aforementioned problems both environmentally, method sensitivity and interferences that you may have to contend with. However, depending on type of metal in question, sensitivity desired and available cost, you can consider AAS with its variants, ICP-OES, ICP-MS just as suggested in previous contributions.
For Quality control - ICP-MS is the best method. color development for individual metals is available. but these methods are not viable.
color development for individual metal exist in standard methods for analysis of water and waste water APHA
You may see the USP ( or EP)method for heavy metals ( as Pb) in medical products.
Colorimetric methods are not suitable for heavy metal measurement in water. Therefore ICP-MS is the best method.
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