Determination of mercury in urine by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of mercury in urine samples. The isotope ratio of mercury in each analytical run was calculated from the peak area of each isotope. Various modifiers were tested in order to obtain the greatest sensitivity for mercury. After preliminary studies, a mixed modifier of palladium, Mg(NO3)(2) and 2% HCl was used. The ETV-ID-ICP-MS method was applied to the determination of mercury in NIST SRM 2670 Toxic Metals in Freeze-Dried Urine and several fresh urine samples collected from graduate students. The results obtained for NIST SRM 2670 agreed satisfactorily with the certified values. The results for other samples analysed by isotope dilution and by the method of standard additions agreed satisfactorily. The detection limit of mercury,calculated from the standard additions calibration plot, was about 0.02 ng ml(-1) with the ETV-ICP-MS method. The precision between sample replicates was better than 8% for all determinations.