Chromatograms of volatile arsenic species from standards and bacterial cultures showing that the volatile species can be separated in four minutes, and that AsH3 (peak 1), CH3AsH2 (peak 2), (CH3)2AsH (peak 3), and (CH3)3As (peak 4), are present in the samples. (a) standards of volatile arsenic species (AsH3, CH3AsH2, (CH3)2AsH, and (CH3)3As) generated from AsIII, MMAV, DMAV, and TMAO, respectively; (b) sample of E. coli expressing ArsM7 incubated with 10 μM arsenite for 12 h; (c) sample of E. coli expressing ArsM7 incubated for two hours; (d) sample (c) spiked with AsH3 and (CH3)2AsH standards. The amounts of arsenic in chromatogram (a) were 1 ng each for AsH3, CH3AsH2, and (CH3)2AsH, and 1.5 ng for (CH3)3As.