Extractive spectrophotometric assay of cyclizine in a pharmaceutical formulation and biological fluids

Two highly sensitive and simple spectrophotometric methods were developed to quantitate the drug cyclizine (CYC) in its pure form and in a pharmaceutical formulation. The two methods involved ion-associate formation reactions (method A) with mono-acid azo dyes, i.e., sudan (I) and sudan (II), as well as ion-pair reactions (method B) with bi-azo dyes, i.e., sudan (III), sudan (IV) and sudan red 7B (V). The reactions were extracted with chloroform, and the extraction products were quantitatively measured at 480, 550, 500, 530 and 570 nm using reagents I–V, respectively. The reaction conditions were monitored and optimised. The Beer plots for reagents I–V showed linear relationships for the concentrations of 4.2–52.0, 5.4–96.0, 3.5–43.0, 4.4–80.0 and 0.6–18.0 μg mL−1, respectively, with molar absorptivities of 2.2 × 104, 4.1 × 104, 3.6 × 104, 2.5 × 104 and 1.3 × 104 L mol−1 cm−1, respectively. Sandell sensitivities and detection limits were calculated and analysed. The implementation of the two methods to the analysis of a commercial tablet (Valoid) succeeded, and the recovery study suggested that there was no interference from common excipients in the tablet. Regarding the accuracy and precision of the methods, a statistical comparison of the results was performed using Student’s t-test and the F-test at the 95% confidence level. The accuracy and precision of the proposed methods were not significantly different.