In situ arsenic speciation on solid surfaces by desorption electrospray ionization tandem mass spectrometry

A simple and fast (<5 s) method for in situ arsenic speciation on solid surfaces has been developed based on desorption electrospray ionization-tandem mass spectrometry (DESI-MS). Arsenic-polluted environmental samples such as animal feed and plant tissues could be directly monitored by DESI-MS. Each arsenic species in this study, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), arsenocholine (AsC), 4-arsanilic acid (p-ASA), 4-hydroxyphenylarsonic acid (4-OH), Nitarsone, Roxarsone and two inorganic arsenic species, arsenate As(V) and arsenite As(III), could be detected by their typical m/z and collision induced dissociation (CID) behavior respectively. By the characteristic information, mixtures of different arsenic species could be detected without any sample preparation and separation process. This method could give absolute detection limits of the arsenic species at ng/mm(2) to pg/mm(2) level with a best RSD of 5.3% (n = 5). The method could be potentially applied to in situ environmental monitoring of arsenic pollution, especially that caused by arsenic pesticides, animal feed additives, herbicides and wood treatment.