Peroxide analysis in laundry detergents using liquid chromatography

Liquid chromatographic (LC) studies have been conducted to investigate the formation and decomposition of peroxyacetic acid (PAA) and hydrogen peroxide in laundry detergents: Both, methyl-p-tolylsulfide (MTS) and methyl-phenylsulfoxide (MPSO) are suitable reagents for the selective LC determination of peroxycarboxylic acids in the presence of a large excess of hydrogen peroxide. MTS is oxidized in acidic media to the corresponding sulfoxide (MTSO) and MPSO is oxidized in alkaline media to methyl-phenylsulfone (MPSO2). In both cases, triphenyl phosphine (TPP) can be used for the subsequent determination of hydrogen peroxide using LC. TPP is oxidized to the corresponding phosphine oxide (TPPO). The formation and the decomposition of PAA and hydrogen peroxide in laundry detergents with time have been observed using both methods. Acidification prior to analysis and subsequent application of MTS and TPP for the simultaneous determination of PAA and hydrogen peroxide in alkaline samples has been identified to be best suited as means for preservation of the original sample composition.