Abstract
A simple, rapid, and stability-indicating HPLC method has been developed for the determination of isoxsuprine in the presence of its degradation products. Acetonitrile: potassium dihydrogen phosphate (0.01 M solution) adjusted to pH 2.2 ± 0.1 with phosphoric acid (18:82 v/v), was used as the mobile phase, at a flow rate of 2.5 mL/min.
A μ Bondapak
™
C
18
10μm column (3.9 mm i.d. × 150 mm) was utilized as a stationary phase. Detection was affected spectrophotometrically at 275 nm. Methyl p-hydroxybenzoate was used as an internal standard. The method was applied for the determination of isoxsuprine in the presence of its main degradation products, namely: 4-hydroxy-benzaldehyde, 4-hydroxybenzyl alcohol, 4-hydroxybenzoic acid, and 4-hydroxyacetophenone. Linearity range for isoxsuprine was 2-40 μg/mL with correlation coefficient (r) of 0.9998 and minimum detectability was 0.2 μg/mL (∼6 × 10
-7
M).
The proposed method was further applied to the analysis of commercial tablets containing the drug, the percentage recoveries ± SD were 99.60 ± 0.76 and 99.78 ± 0.88, and these values were in agreement with those given with the official methods. The method was also adopted to detect isoxsuprine in spiked human plasma at its therapeutic level of concentration (0.4 μg/mL). The proposed HPLC method was successfully applied to study the degradation kinetics of isoxsuprine. The photothermal degradation of isoxsuprine upon exposure to UV light was first-order with regard to its concentration.