A sample stacking-capillary electrophoresis method for simultaneous determination of nitrate and thiocyanate ions of ultra-heat-treated milk samples

Ultra-heat-treated (UHT) cow milk is mostly consumed in Turkey. Heating milk can cause some chemical and biochemical changes that affect different components of milk. However, studies on the constituents of UHT milk are scare. In the present study, nitrate and thiocyanate contents of commercial UHT whole cow milk were determined simultaneously by sample stacking-capillary electrophoresis. The best separation of nitrate and thiocyanate ions was performed by reducing the electroosmotic flow at pH 4.0 using 30 mM formic acid and 30 mM sodium sulfate containing separation electrolyte. Analysis was completed in less than 3 min. The limits of detection obtained at a signal-to-noise ratio of 3 for nitrate and thiocyanate were 0. 03 mg/L (0.48 mu mol/L) and 0.06 mg/L (1.03 mu mol/L), respectively. The nitrate concentration in commercial UHT milk samples ranged between 0.20 and 1.50 mg/L (3.23-24.20 mu mol/L) and the thiocyanate ion concentration ranged between 0.41 and 0.67 mg/L (7.06-11.55 mu mol/L).