Derivatization of organometal(loid) species by sodium borohydride. Problems and solutions.
Like other derivatization techniques, hydride generation is a chem. reaction that produces side-reactions leading to anal. problems. Demethylation of dimethylarsinic acid is dependent upon the pH level of the hydride generation reaction mixt. If the reaction mixt. was acidic, then in addn. to Me2AsH, the monomethyl arsenic hydride [MeAsH2] could be detected. Demethylation and also the formation of an unidentified arsenic species were noted when tri-Me arsonic oxide was used as derivatization educt. All of these effects depend on the pH level of the hydride generation mixt. The authors obsd. significant levels of organometal(loid) species of elements such as Ge, As, Sn, Sb, Hg and Bi in blank hydride generation mixts. The organometal(loid) contamination was irreproducible even during 1 day using a single soln. of sodium borohydride in deionized water. The organometal(loid) contamination arises directly from the derivatization agent, sodium borohydride, itself. Use of helium purging and various adsorptive materials to decontaminate the sodium borohydride soln. prior to anal. did not result in a significant decrease in organometal(loid) contamination levels. Use of a palladium-cluster stabilized with 1,10-phenanthroline as alternative hydride generation derivatization agent was not found to be suitable, since reaction yields were poor and transmethylation reactions were noted.
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