Optimization of dispersive liquid-liquid microextraction with central composite design for preconcentration of chlordiazepoxide drug and its determination by HPLC-UV

A simple, rapid, and sensitive method based on dispersive liquid-liquid microextraction combined with HPLC-UV detection applied for the quantification of chlordiazepoxide in some real samples. The effect of different extraction conditions on the extraction efficiency of the chlordiazepoxide drug was investigated and optimized using central composite design as a conventional efficient tool. Optimum extraction condition values of variables were set as 210 L chloroform, 1.8 mL methanol, 1.0 min extraction time, 5.0 min centrifugation at 5000 rpm min-1, neutral pH, 7.0% w/v NaCl. The separation was reached in less than 8.0 min using a C18 column using isocratic binary mobile phase (acetonitrile/water (60:40, v/v)) with flow rate of 1.0 mL min-1. The linear response (r2 > 0.998) was achieved in the range of 0.005-10 g mL-1 with detection limit 0.0005 g mL-1. The applicability of this method for simultaneous extraction and determination of chlordiazepoxide in four different matrices (water, urine, plasma, and chlordiazepoxide tablet) were investigated using standard addition method. Average recoveries at two spiking levels were over the range of 91.3-102.5% with RSD < 5.0% (n = 3). The obtained results show that dispersive liquid-liquid microextraction combined with HPLC-UV is a fast and simple method for the determination of chlordiazepoxide in real samples.