Separation of Benzodiazepines Using Capillary Electrochromatography

Abstract

Benzodiazepines are often used for the treatment of epilepsy, convulsions, and many psychiatric disorders. The widespread use of this class of drugs has occasionally raised concern about recreational benzodiazepine abuse and has led to the erroneous impression that benzodiazepines have a relatively high abuse liability among recreational drug users. Therefore, the separation and identification of these compounds is of great interest. In general, the separation of benzodiazepines is performed using high-performance liquid chromatography (HPLC). Recently, capillary electrochromatography, which combines the high efficiency of capillary zone electrophoresis and the high selectivity of HPLC, has gained much attention. The focus of the work reported here is the use of a 40-cm packed bed of Reliasil 3- microm C(18) stationary phase to separate seven benzodiazepines. Optimal conditions are established by varying the mobile phase, amount of organic modifier, buffer concentration, applied voltage, and column temperature. A mobile phase composition of Tris-HCl (pH 8)-acetonitrile (60:40), an electrolyte concentration of 30mM, and a temperature of 15 degrees C with an applied voltage of 20 kV proves to be optimum. In addition, the method developed here is applied to the characterization of oxazepam in a standard urine sample.

Recent applications in capillary electrochromatography

“…A mixture of seven benzodiazepines could be separated by CEC on a capillary column packed with 3 mm C 18 particles, as was shown by Kapnissi and Warner [64]. The best separations were obtained with ACN as the organic modifier.…”

An Overview on Total Analytical Methods for the Detection of 1,4-Benzodiazepines

“…CEC has been demonstrated for the separation of mixtures of benzodiazepines, corticosteroids and thiazide diuretic drugs using fused-silica capillary CEC Hypersil ODS and Apex ODS columns (33-50 cm ×50-75 µm, 3 µm) coupled wtih UV and ESI-MS detection [103]. The use of a 40cm packed bed of Reliasil 3-µm C 18 stationary phase was focused by Kapnissi and Warner [104] to separate seven benzodiazepines under the optimum conditions: a mobile phase composition of Tris-HCl (pH 8)-acetonitrile (60:40), an electrolyte concentration of 30 mM, and a temperature of 15°C with an applied voltage of 20 kV. The method was applied to the characterization of oxazepam in a standard urine sample.…”

A rapid CZE method for the analysis of benzodiazepines in spiked beverages

“…Considering this, and given the low pK a 's of benzodiazepines, which makes them difficult to ionise and therefore difficult to analyse by CZE, the majority of benzodiazepine analyses are performed with micellar EKC (MEKC) [13][14][15][16][17][18][19][20]. CEC on octadecyl stationary phases [21] and on novel stationary phases based on modified silyl silica gel [22] have also been developed. Only a handful of methods have employed CZE for the analysis of benzodiazepines [18,19,[22][23][24][25].…”