Reversed-phase liquid chromatograhy/electrospray ionization tandem mass spectrometry for analysis of perchlorate in water

A new reversed-phase liquid chromatograhy/electrospray ionization tandem mass spectrometry method was developed for the analysis of perchlorate in water. The improved separation of perchlorate from common anions along with sample dilution effectively reduced matrix effects, primarily ion suppression caused by common anions. The 18O-enriched perchlorate used as an internal standard provided further compensation for potential changes associated with instrument sensitivity, retention time shifting, peak broadening, ion suppression, and other matrix effects. The mean recoveries and relative standard deviations were 92–107% and 2.5–9.5% for simulated water matrix spikes at 0.05–1.0 μg/L, and 80–106% and 3.8–13% for real water sample matrix spikes at 2.0 μg/L, respectively. The method detection limits were 0.007 μg/L for reagent water and 0.014 μg/L for the simulated water matrix that contained 100 mg/L of SO42−, CO32−, and Cl− anions; 2 mg/L of PO43− as P and NO3− as N; and 0.1 mg/L of Br−, BrO3−, ClO2−, ClO3−, and F− anions in reagent water, respectively. When using cartridge pretreatment to remove problematic SO42−, CO32−, and Cl− anions, the minimum reporting level could be set to 0.05 μg/L or lower. With 10-fold dilution, the minimum reporting level was conservatively set to 0.5 μg/L.