Our standard approach is to use anion exchange chromatography (50 mm Hamilton PRPX-100) with a 50 mM (NH4)2CO3 gradient. We re using a fast method which we developed in our lab and it allows us to separate AB, DMA, MMA, and total inorganic As in 1.7 minutes. It can also be used to separate As3 and As5 in water samples where the organo compounds are not expected. AC,AB, As3, DMA, MMA and As5 can be separated in 3.5 minutes with a gradient separation. We use the Agilent 1260 LC interfaced to the 8800 ICP-QQQ and use mass shifting of As to AsO. Detection limits for As species are about 10 ng/L except of AsV which is about 20 ng/L.
For more complex speciation such as arsenosugars and thiol analogs then we use anion and cation ion exchange and reversed phase methods.
More in depth descriptions of our As speciation methods are published in:
Jackson, BP. 2015. Fast Ion Chromatography-ICP-QQQ for arsenic speciation. Journal of Analytical Atomic Spectroscopy. DOI: 10.1039/C5JA00049A
Taylor, V.F., Jackson, B.P, Siegfried, M. Francesconi, K., Kirshtein, J. Voytek, M. 2012. Multiple Arsenic speciation and cycling in food chains from mid-Atlantic hydrothermal vents. Environmental Chemistry, 9(2):130-138.
Jackson, B.P, Taylor, V.F., Punshon, T. Cottingham, K.L. (2012) Arsenic concentration and speciation in infant formulas and first foods. Pure and Applied Chemistry 84: 215-224.