Comparative Study of Univariate Spectrophotometry and Multivariate Calibration for the Determination of Levamisole Hydrochloride and Closantel Sodium in a Binary Mixture.

Six simple, accurate, reproducible, and selective derivative spectrophotometric and chemometric methods have been developed and validated for the determination of levamisole HCl (Lev) either alone or in combination with closantel sodium (Clo) in the pharmaceutical dosage form. Lev was determined by first-derivative, first-derivative ratio, and mean-centering methods by measuring the peak amplitude at 220.8, 243.8, and 210.4 nm, respectively. The methods were linear over the concentration range 2.0-10.0 μg/mL Lev. The methods exhibited a high accuracy, with recovery data within ±1.9% and RSD <1.3% (n = 9) for the determination of Lev in the presence of Clo. Fortunately, Lev showed no significant UV absorbance at 370.6 nm, which allowed the determination of Clo over the concentration range 16.0-80.0 μg/mL using zero-order spectra, with a high precision (RSD <1.5%, n = 9). Furthermore, principal component regression and partial least-squares with optimized parameters were used for the determination of Lev in the presence of Clo. The recovery was within ±1%, with RSD <1.0% (n = 9) and root mean square error of prediction ≤1.0. The proposed methods were validated according to the International Conference on Harmonization guidelines. The proposed methods were used in the determination of Lev and Clo in a binary mixture and a pharmaceutical formulation, with high accuracy and precision.