Urinary antimony speciation by HPLC-ICP-MS

Abstract

This is the first study to report on the determination of Sb species in urine. To this end, HPLC was coupled online to an ICP-MS instrument using ultrasonic nebulization (USN) or hydride generation (HG) for sample introduction into the ICP-MS. The high chloride concentration in urine seriously hampered the chromatographic separation of Sb(V) and Sb(III) on the Dionex AS14 anion exchange column. Distinct signal suppression, shifting of retention times and severe peak broadening did not allow the application to urine samples. Progress to avoid these problems in HPLC-USN-ICP-MS could be made by employing a Hamilton PRP-X100 anion-exchange column. However, Na eluting in the void volume of the column gave rise to a Na-induced peak overlapping with the Sb(V) signal when USN was used to aspirate the HPLC eluents into the plasma. Therefore, a HG system was placed between the HPLC and ICP-MS instrumentation to overcome this dilemma. Thus, Sb(V) and Sb(III) were separated in urine with the PRP-X100 column using 20 mM EDTA at pH 4.7 as the mobile phase. Similarly, an ION-120 anion-exchange column was employed to separate trimethylantimony dichloride (TMSbCl₂) and Sb(V) with a mobile phase containing 2 mM NH₄HCO₃ and 1 mM tartaric acid at pH 8.5. Detection limits of 20 ng l⁻¹, 12 ng l⁻¹ and 8 ng l⁻¹ for Sb(V), TMSbCl₂ and Sb(III), respectively, could be established in a 1 + 2 diluted urine matrix. The developed HPLC-HG-ICP-MS method was applied to the speciation of Sb in the urine of occupationally exposed and non-exposed subjects. Additionally, two lyophilised urine reference materials were investigated. Sb(V) was by far the predominant Sb species, followed by TMSbCl₂. Only ultratraces of Sb(III), if any detectable, could be found. The sum of the concentrations of Sb(V), Sb(III) and TMSbCl₂ in urine samples ranged between 51 and 78% of their total Sb concentrations.