Preconcentration and determination of chlordiazepoxide and diazepam drugs using dispersive nanomaterial-ultrasound assisted microextraction method followed by high performance liquid chromatography.

Benzodiazepines (BDs) are used widely in clinical practice, due to their multiple pharmacological functions. In this study a dispersive nanomaterial-ultrasound assisted- microextraction (DNUM) method followed by high performance liquid chromatography (HPLC) was used for the preconcentration and determination of chlordiazepoxide and diazepam drugs from urine and plasma samples. Various parameters such as amount of adsorbent (mg: ZnS-AC), pH and ionic strength of sample solution, vortex and ultrasonic time (min), and desorption volume (mL) were investigated by fractional factorial design (FFD) and central composite design (CCD). Regression models and desirability functions (DF) were applied to find the best experimental conditions for providing the maximum extraction recovery (ER). Under the optimal conditions a linear calibration curve were obtained in the range of 0.005-10µgmL(-1) and 0.006-10µgmL(-1) for chlordiazepoxide and diazepam, respectively. To demonstrate the analytical performance, figures of merits of the proposed method in urine and plasma spiked with chlordiazepoxide and diazepam were investigated. The limits of detection of chlordiazepoxide and diazepam in urine and plasma were ranged from 0.0012 to 0.0015µgmL(-1), respectively.

Application of optimized dispersive liquid-liquid microextraction for determination of melatonin by HPLC-UV in plasma samples.

Melatonin (N-acetyl-3-(2-aminoethyl)-5-methoxyindole) is biologically active as a neurohormone and antioxidant agent. The optimized dispersive liquid-liquid microextraction (DLLME) followed by high-performance liquid chromatography-ultra violet detection (HPLC-UV) was used for the analysis of melatonin in human plasma. Influence variables such as volume of extracting (carbon tetrachloride: CCl4) and dispersing solvents (acetonitrile: ACN), pH and ionic strength, extraction time and centrifugation time were screened in a 2(6-2) fractional factorial design (FFD) and then the significant variables were optimized by using a central composite design (CCD). At optimum conditions values of variables set as pH 6.0, 1.5 mL ACN, 140 µL CCl4, 1.0 min extraction time and 3.0 min centrifugation at 4,500 rpm. At optimum conditions method has linear response over 2.0-500.0 ng mL(-1) with detection limit of 0.5 ng mL(-1) with relative standard deviations (RSDs) less than 5.0%. The values of intra-day and inter-day RSD were 4.3% and 8.5%, respectively. The method was applied successfully for the analysis of melatonin in plasma sample.