The determination of copper, zinc, cadmium and lead in urine by High Resolution Inductively Coupled Plasma Mass Spectrometry

Abstract

High resolution ICP-MS was used to determine Cu, Zn, Cd and Pb in urine. The effect of sample dilution, preparation method and choice of internal standard were assessed. Sample dilution (1+9) with In as the internal standard was found to offer an acceptable compromise between analytical accuracy and sample throughput. A spectral resolution of 3000 was used to separate Cu and Zn isotopes from interferences commonly found in biological matrices, while a resolution of 300, offering increased sensitivity and lower detection limits, was used for Cd and Pb. The accuracy and precision of the analytical method were evaluated using two Bio-Rad Lyphochek standard urines. The concentrations of Cu, Zn, Cd and Pb in Bio-Rad Level 1 reference urine were determined by external calibration and were found to agree to within 0-17% of recommended values (Cu 48, Zn 710, Cd 6.5 and Pb 14.3 ng g -1). Closer agreement of 0-7% was found for Bio-Rad Level 2 reference urine (Cu 63, Zn 1057, Cd 12.3 and Pb 69 ng g -1). Forty-two urine samples from seven workers occupationally exposed to Cd were analysed and the results were compared with those obtained from 11 samples collected from four non-exposed volunteers. Similar average concentrations of Cu and Zn were found in both groups when the results were normalised to creatinine levels. Workers exposed to Cd were found to have an average urine Cd concentration elevated approximately 7-8-fold over that measured for the control group (about 2.2 compared with about 0.3 ng g -1, or 1.7 and 0.2 mg per gram of creatinine when normalised). Urinary levels of Pb were slightly increased in the cadmium exposed workers (about 6 compared with about 4 ng g -1).