How to measure concentration of arsenite and arsenate in a water sample
Speciation analysis is very challenging because you would like to separate the species first before detection. In order times electrochemical detection was done by now ion chromatography is the way to go for arsenic speciation. You will need ion chromatography system with inductively coupled plasma with mass spectrometry. Have a look at this paper: Determination of Anionic, Neutral, and Cationic Species of Arsenic by Ion Chromatography with ICPMS Detection in Environmental Samples, Anal. Chem., 1998, 70 (17), pp 3649–3655 The good thing about Analytical Chemistry papers is that most of the methods are reliable.