Dear Hamid,

Refer to the following interesting link that answers your question. You will find a paragraph dedicated to arsenic in groundwater.

Regards

https://www.ncbi.nlm.nih.gov/books/NBK230885/

Depending on the physical, chemical and biogeochemical processes and condition of the environment, various arsenic species can be present in water. Water soluble arsenic species existing in natural water are inorganic arsenic (iAs) and organic arsenic (oAs) species. All acidic species, according to the chemical equilibrium, have well-recognized molecular and ionic forms in water. The distribution of iAs and oAs species is a function of pH value of water traces of arsenic that are found in groundwater, lakes, rivers and ocean. The WHO provisional guideline value for arsenic in drinking water is 10 μg L−1. The most selective and sensitive methods for determination of total arsenic and its species in water are coupled techniques including chromatography, optical methods and mass spectrometry.

Dear Hamid,

Thank you for the question.

In the natural groundwater condition, arsenic exists in two oxidation states, i.e., As(III) and As(V). The analysis of arsenic especially in ppb level is a little bit difficult task. For ppb level measurement, ICP is fine. But, speciation analysis can not be done by ICP.

So, there are two other instruments named: ASV (Anodic Stripping Voltammetry) and IC (Ion Chromatography) using which you can easily measure arsenic in ppb level. (up to 0.1 ppb).

Note: These instruments are user-friendly, easy to operate and give a very accurate and precise result. As(III), As(V), and As(Total) can be easily measured using these instruments. But the only problem is that the analysis using these instruments is slightly time-consuming than that of ICP. In ASV, the average time required for analysis of one sample is 10-12 minutes and in IC, it is around 10-25 minutes (depending upon the speciation analysis).

So my suggestion is: (From my personal experience)

Use ASV for measurement of As(V), As(total) (10 min per sample) and Ion-chromatography for measurement of As(III) only (8 min per sample).

If you have any further queries regarding the analysis of arsenic, feel free to ask.

Regards,

Amulya Prasad Panda

you may try the instruments suggested by Amulya Prasad Panda

However, if you can afford, it will be good to send your samples to external NABL accredited lab and get it tested through ICP-MS which will give you result in ppb.

Dear Madam Anju Baroth,

Thank you very much. I recommend your suggestion.

Yes, ICP-MS is the best technique for the measurement of arsenic in ppb/ppt level. But the only problem is that speciation analysis can not be possible by ICP-MS. As arsenic commonly exists in two different forms, i.e., As(III) and As(V), it is very important to do the speciation analysis. So, for the speciation study, LC-ICP-MS or HPLC-ICP-MS is required, which ultimately increases the cost of analysis.

So, Hamid Sohail, If you can afford it, then it is fine. Otherwise, for long-term purposes, you have to think about alternatives.

I am also agree that ICP-MS is the best option in current phase of research.

Dear Hamid,

You do not say with what accuracy and precision you require, so a full answer is not possible.

There are several good field-test kits, such as the Palintest's 'Arsenator', that give good semi-quantitative results and can be used in the lab perfectly well. Google 'Arsenator' or 'As field-test' for details.

There are colorimetric methods, such as the silver diethylthiocarbamate (AgDDTC) method. Although such methods have highish detection limits (typically a few tens of ppb) by using larger samples that can be lowered. Search for 'colourimetric (or colorimetric) As analysis'

Graphite-furnace AAS is a good direct method with detection limits (if my recall is correct - it's years since I used it) of a few ppb.

Most of us use ICP-MS, so it would be worthwhile your seeking a collaboration with someone near you that has one and (important) really knows how to use it. Getting numbers out of an ICP-MS is very easy; getting numbers for As that mean something is not.

ICP-MS is also OK if you want to speciate - you simply use an ion-exchange column to remove As(V) and measure the remaining As(III), whilst also measuring total As on a separte subsample. It doubles the cost and more than doubles the time needed, but it works.

John McArthur

Arsenic can be easily analysed by ICP-MS in ppb level. Literature available in all Labs.