Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA; also known as cacodylic acid) are metabolites of inorganic arsenic compounds and are used as herbicides. In this application, IC SI-35 2B, a column for anion analysis, was used with an LC/MS to analyze MMA and DMA. SI-35 2B was feasible separating and eluting MMA and DMA within 2 minutes. Meanwhile, arsenobetaine, an organic arsenic compound commonly found in marine products, is weakly retained under the condition used and elutes before MMA and DMA. Therefore, presence of arsenobetaine does not affect the analysis of MMA and DMA.

Sample: 50 ng/mL each, 1 µL

1. Arsenobetaine
2. MMA; Monomethylarsonic acid
3. DMA; Dimethyl arsinic acid