Fast analysis of thiocyanate by ion-pair chromatography with direct conductivity detection on a monolithic column

Fast analysis of thiocyanate by ion-pair chromatography using a silica-based monolithic column and direct conductivity detection was carried out. Chromatographic separation was performed on a Chromolith Speed ROD RP-18e using tetrabutylammonium hydroxide (TBA)–phthalic acid–acetonitrile as eluent. The effects of eluent concentration, eluent pH value, column temperature and flow rate on retention time of thiocyanate were investigated. The optimized chromatographic conditions for the determination of thiocyanate were as follows: 0.25 mmol/L TBA–0.18 mmol/L phthalate–7% acetonitrile (pH 5.5) as eluent, column temperature of 30 °C, and flow rate of 6.0 mL/min. Retention time of thiocyanate was less than 1 min under the conditions. Common anions (Cl^?, NO₃^?, SO₄^2? and I^?) did not interfere with the determination of thiocyanate. Detection limit (S/N = 3) of thiocyanate was 0.96 mg/L. Calibration graph between peak area and the concentration of thiocyanate was linear in the range of 2.0–100.0 mg/L. Relative standard deviation (RSD) of chromatographic peak area was 1.4% (n = 5). This method has been applied to the determination of thiocyanate in ionic liquids. Recoveries of thiocyanate after spiking were 100.5%.