Exact mass measurements on-line with high-performance liquid chromatography on a quadrupole pass spectrometer

Exact mass measurements were performed on-line with high-performance liquid chromatography on a quadrupole mass spectrometer. Compounds with molecular weights from 98 to 797, mainly aromatic sulfonates and sulfonamides, were analyzed with electrospray ionization in positive or negative mode. Interna l mass calibration compounds were continuously added after separation. A Ga ussian fit of the mass errors of 808 individual measurements (concentration s of 1-10 mg/L, 20-200 ng absolute on column) resulted in a mean error of 0 .1 mmu (0.45 ppm) and a standard deviation sigma of 1.5 mmu (5.4 ppm). The 99.7% confidence intervals (3 sigma) were +/-4.5 mmu (+/-16.2 ppm) for sing le mass measurements. Averaging 10 measurements further reduced the errors to less than +/-1.5 mmu (+/-5 ppm). Isobaric interferences with ions result ing from the mass calibrants were avoided by the use of complementary mass calibrants. The results were verified (differences below +/-4.5 mmu) with a LC/oa-TOFMS. Limited mass range chromatograms were used to enhance selecti vity in the analysis of mixtures. The method was applied to determine the e lemental composition of a potential dye metabolite detected in anaerobicall y treated textile wastewater.