Application of direct analysis in real time to a multiphase chemical system: Identification of polymeric arsanes generated by reduction of monomethylarsenate with sodium tetrahydroborate

Direct analysis in real time (DART) has been applied in conjunction with high-resolution Orbitrap mass spectrometry to characterize the aqueous reduction of monomethylarsenate by tetrahydroborate (B/As molar ratio approximate to 4 mol/mol). Under these conditions, the reaction gives rise to a complex mixture of arsenic compounds which result in the formation of a reddish precipitate. The use of the DART revealed the presence of a number of polymeric arsanes - up to eight arsenic atoms - associated with the liquid/solid phase of this reaction system. From a reactivity point-of-view, these polymers exhibit an uncommon ionization pathway. In fact, similar to the alkanes, the action of the DART results in the generation of [M - H](+) ions. Furthermore, for each oligomer MeHAs-(AsMe)(n)-AsHMe (n=0-8), a series of oxidation products [(M+nO) - H](+) were also identified and their formation has been discussed. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.