Use of a Sonogel-Carbon electrode modified with bentonite for the determination of diazepam and chlordiazepoxide hydrochloride in tablets and their metabolite oxazepam in urine

► Diazepam and chlordiazepoxide hydrochloride are determined using Sonogel-Carbon electrode modified by 5% bentonite. ► We use a low cost, sensitive, selective and time saving method for the quantification. ► The electrode has been successfully used for the determination of diazepam and chlordiazepoxide hydrochloride in Valium® and Omnalio tablets, respectively. ► The developed electrode has been applied successfully to the determination of oxazepam (the major metabolite in human body both of diazepam and chlordiazepoxide hydrochloride) in human urine real samples. Sonogel-Carbon electrode (SngCE) modified with bentonite (BENT) shows an interesting alternative electrode to be used in the determination of 1,4-benzodiazepines by square wave adsorptive cathodic stripping voltammetry (SWAdCSV). Diazepam (DZ) and chlordiazepoxide hydrochloride (CPZ), were determined using SngCE modified by 5% BENT. An electrochemical study of different parameters (such as pH, buffer type, ionic strength, accumulation potential, scan rate, and accumulation time) which affect the determination of DZ and CPZ is reported. Linear concentration ranges of 0.028–0.256μgmL−1 DZ (r=0.9997) and 0.034–0.302μgmL−1 CPZ (r=0.9997) are successfully obtained after an accumulation time of 60s. The quantification and detection limits were calculated to be 14.0 and 4.0ngmL−1 for DZ, and 16.0 and 5.0ngmL−1 for CPZ, respectively. The surface of the proposed electrode was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The developed method was applied to the analysis of commercially available tablets and human urine real samples. Analysis was performed with better precision, very low detection limits, and faster than previously reported voltammetric techniques.