Determination of urinary thiocyanate and nitrate using fast ion-interaction chromatography

A simple and rapid chromatographic method for determination of nitrite, nitrate and thiocyanate is reported, and applied to the analysis of non-, medium and heavy smokers' urine samples. Ion-interaction liquid chromatography was carried out on a short 30 mm×4.6 mm C₁₈ column (3 μm particle size) with a mobile phase of 10 mM tetrabutylammonium phosphate in 20% MeOH. The chromatography was performed at an elevated temperature of 45°C, at a flow-rate of 1 ml/min. Detection was by direct UV absorption at 230 nm. Sample preparation involved centrifugation and dilution, followed by sample clean-up on a C₁₈ solid-phase extraction cartridge. The developed method proved both precise (% RSD <2%) and sensitive (standard detection limits <0.1 mg/l), and yielded total run times of under 10 min when applied to urine analysis of smokers and non-smokers, with thiocyanate eluting in under 5 min.