Monitoring of thiocyanate as a biomarker in saliva and serum samples by a combination of solid-phase extraction based on a layered double hydroxide nano-sorbent and gas chromatography

Abstract

The thiocyanate ion is a biomarker for exposure to environmental tobacco smoke. We used a simple solid-phase extraction method based on a nickel–aluminum layered double hydroxide (Ni–Al LDH) nano-sorbent for the extraction of trace amounts of thiocyanate from biological samples, followed by gas chromatography with flame ionization detection. The extraction is based on the adsorption of thiocyanate anions on the Ni–Al nitrate LDH and/or their exchange with the nitrate anions in the LDH interlayer. Several parameters affecting the extraction performance (pH, the amount of nano-sorbent, the eluent type and volume, the sample loading flow-rate and the sample volume) were investigated and optimized. Under the optimized experimental conditions, good linearity was achieved from 0.6 to 80 ng mL⁻¹ thiocyanate. The limit of detection and relative standard deviation for the thiocyanate ion were 0.2 ng mL⁻¹ and 4.6%, respectively. The method was successfully applied to monitoring thiocyanate in human saliva and serum samples. It was confirmed that the thiocyanate concentration in saliva noticeably increased after smoking.