Simultaneous determination of albendazole and praziquantel by second derivative spectrophotometry and multivariated calibration methods in veterinary pharmaceutical formulation.

The simultaneous determination of albendazole (ABZ) and praziquantel (PZQ) was performed by different mathematical approaches: second derivative spectrophotometry (SDS), classical least squares, regression of partial least squares and principal components regression based on spectral data of drugs dissolved in methanol-hydrochloric acid solution. The detection limits for multivariate calibrations were determined by creating a surrogate variable signal. SDS presented the best analytical features. The recoveries of ABZ and PZQ from the synthetic samples were near to 100 +/- 5%. The methods were applied in veterinary pharmaceutical formulation whose mass ratio ABZ:PZQ is 10:1; the results obtained were according to nominal content.