CAPILLARY ELECTROPHORESIS DETERMINATION OF BUTALBITAL FROM SERUM USING SOLID PHASE EXTRACTION (SPE) AND ULTRAVIOLET DETECTION

Abstract

Butalbital is a sedative hypnotic that is used mainly in combination with analgesics in the treatment of tension headaches. This paper develops and validates a rapid and sensitive method for the determination of butalbital in serum using capillary electrophoresis (CE) and ultraviolet detection. The internal standard chosen for this assay was aprobarbital because it showed similar chemical structure, identical chromatographic/SPE characteristics, and was commercially available. The CE run buffer contained 50 mM sodium dihydrogen phosphate buffer at pH 9.0 containing 20 mM hydroxypropyl-β-cyclodextrin as a capillary zone electrophoresis (CZE) buffer additive. An SPE method, using C[18] Bond-Elut cartridges, was developed to recover the drug and internal standard from serum. The CE system consists of a 75 micron I.D., 52 cm length fused silica capillary maintained at a run voltage of 15 kV with sample detection performed at 254 nm. The limit of detection for butalbital was <l μg/mL from serum. Linear calibration curves generated in the concentration ranges of 1 to 60 μg/mL showed a coefficient of determination greater than 0.99. The precision and accuracy of the method calculated as RSD and error were 0.65–3.16% and 2.20–8.90%, respectively. Butalbital is commonly coadminisetred with aspirin, acetaminophen, caffeine, and codeine for the treatment of tension headaches. The CE method baseline resolved these compounds from the butalbital and the internal standard. Therefore, there is a decreased chance for interference from commonly coadministered compounds in this assay.