Zopiclone and Zolpidem Quantification in Human Plasma by High Performance Liquid Chromatography with Photo-Diode-Array Detection

Abstract A rapid and selective high performance liquid chromatography method for the simultaneous quantification of zopiclone and zolpidem has been developed. Signals are monitored by a photodiode-array detector with a main 305 nm wavelength and a bandwidth of 10 nm. After one step liquid phase extraction, samples of 100 μL are injected into a 5 μm ODS-2 column (30 cm × 4.6 mm I.D.). Drugs are eluted with a mobile phase containing potassium dihydrogen phosphate buffer, 0.01 M, methanol and tetrahydrofuran (30: 65: 5, V/V/V). Retention times of zopiclone and zolpidem are, respectively, 4.5 min and 5.5 min. The procedure has the necessary sensitivity and precision for pharmacokinetic studies (within day coefficients of variation < 7.1% and between-day coefficients of variation < 12.1%). The linearity and the rapidity of this method are especially attractive for toxicological quantification in emergency toxicology.