ABSTRACT A simple liquid-liquid extraction method and reversed phase ion-paired high-pressure liquid chromatography method have been developed for the determination of cotinine from the urine samples. Mobile phase was consisted of sterile water for irrigation, methanol, acetonitrile and acetic acid (78.5:19.5:1.9:0.2% (v,v,v,v)). pH of the mobile phase was adjusted to 4.3 with diethylamine for better resolution and to prevent peak tailing. The linearity was obtained in the range of 100–2000 µg/L concentrations of cotinine with a coefficient of correlation of 0.999. The recovery was obtained in the range of 75–99% with average value of 94%. The limit of quantification (LOQ) and the limit of detection (LOD) were 300 and 100 µg/L with 2 mL urine for extraction, respectively. The Intra- and inter-day coefficients of variation were <4% for cotinine concentrations of 300, 500 and 1000 µg/L. The amount of caffeine in the urine interfered with the peak of cotinine. The method was applied to the urine samples of smokers, who participated in the trial of the nicotine patch for smoking cessation.
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