Analysis of clonazepam in a tablet dosage form using smallbore HPLC

A stability indicating, reversed phase high-performance liquid chromatographic method utilizing a smallbore HPLC column has been developed for the determination of clonazepam in a commercial tablet dosage form. The use of a small bore column results in a substantial solvent savings, as well as a greater mass sensitivity, especially in the identification of degradation peaks in a chromatogram. The method involves ultraviolet detection at 254 nm and utilized a 150 x 3.0 mm i.d. column packed with 3 microm octyldecylsilane particles with a mobile phase of water methanol acetonitrile (40:30:30, v/v/v) at a flow rate of 400 microl min(-1) at ambient temperature, with and without the use of 1,2-dichlorobenzene as the internal standard. The current USP method for the analysis of clonazepam using a 300 x 3.9 mm i.d. conventional octyldecylsilane column was utilized as a comparison to the smallbore method. The retention times for clonazepam and the internal standard on the 3.0 mm i.d. column were 4.0 and 12.5 min, respectively. The intra- and interday RSDs on the 3.0 mm i.d. column were < 0.55% (n =4) using the internal standard, and < 0.19% (n = 4) without the internal standard at the lower limit of the standard curve, 50 microg ml(-1) and had a limit of detection of 24 ng ml(-1). The assay using the 3.0 mm i.d. column was shown to be suitable for measuring clonazepam in a tablet dosage form.