High-performance liquid chromatographic determination of trace amounts of transition metals in parenteral solutions

Abstract

A high-performance liquid chromatographic (HPLC) method for the determination of trace levels of transition metals (Cu, Pb, Zn, Ni, Co, Cd and Mn) in parenteral solutions (large volume parenterals) was developed. The method involves a preconcentration step on a cation-chelating column (a Nova-Pak C₁₈ guard column coated with Chrome Azurol S) and the separation of the different metals on a Nova-Pak C₁₈ column permanently coated with sodium hexadecanesulfonate. The eluent was a 100 mmol l^–1 tartrate solution of pH 3.1. Colorimetric detection (at 520 nm) after post-column reaction of the metals with 4-(2-pyridylazo)resorcinol was used. The conditions for the preconcentration and separation of the metals (composition, concentration and pH of the eluent) were studied. The repeatability of the results (n = 3) for a concentration level of about 50 µg l^–1 was between 3.5% (Cd) and 5.5% (Ni). The limits of quantification for a preconcentrated sample volume of 4 ml, expressed as µg l^–1, were 0.40 (Cu), 2.1 (Pb), 0.50 (Zn), 0.33 (Ni), 0.23 (Co), 2.5 (Cd) and 2.6 (Mn). The results obtained with the developed HPLC method for ten commercial samples and seven spiked pooled samples were evaluated by comparison with those provided by electrothermal atomic absorption spectrometry (ETAAS). The developed procedure might be a rapid and inexpensive alternative to ETAAS for quality control in the pharmaceutical industry.