In this paper, a simple and rapid method was developed for the simultaneous determination of Piperacillin (PIP) and Tazobactam (TAZ) by second-order derivative spectrophotometry. Water was selected as a solvent for extraction and determination of both analytes. Further studies of photo-stability and forced degradation for both drugs were also performed.The spectral variables were optimized, a smoothing factor of 8•10 3 and a scaling factor of 1•10 4 were selected and the analytical signals were evaluated at 296.3 nm and 233.3 nm for PIP and TAZ, respectively.The detection and quantification limits for PIP and TAZ were: 3.2•10 -7 to 9.5•10 -7 and 2.7•10 -7 to 8.9•10 -7 mol/L, respectively. The levels of repeatability (RSD) were 1.5% and 2.4% for PIP and TAZ respectively.The method was applied to the pharmaceutical formulation TAZONAM NF® Wyeth. USA, with a nominal content of 4.0 g of PIP, 0.5 g of TAZ, 0.139 g of citric acid and 1 mg of EDTA. A study of excipients was carried out and it was found that they do not interfere with quantification. By applying this method, a content of 3.96 ± 0.04 g and 0.57 ± 0.01 g was found of PIP and TAZ, respectively.

This work presents a rapid and simple method for the parallel determination of Desogestrel (DSG) and 17α-Ethinylestradiol (EE2) by second order derivative spectrophotometry and its application in pharmaceutical formulations. Study of the effect of the solvents, excipients and spectral behavior is also included. Acetonitrile was selected as a solvent; subsequently the samples were evaluated by second order derivatives, using a smoothing factor of 8,000 and a scale factor of 10 4. The EE2 determination was carried out using the graphical method at 288 nm and DSG by the zero-crossing method at 220 nm. The determination ranges were found to be between 1.5•10-6 and 5•10-4 mol/L and 1.7•10-7 to 1.0•10-3 mol/L for DSG and EE2, respectively. The homogenized tablets are divided in two fractions, the first, called sample A, was dissolved in acetonitrile, which contains the absorbents species that is polyvidone, DGS and EE2, the latter is determined directly at 288 nm. Meanwhile, in the second fraction (sample B), after extract with water the polyvidone and partially EE2, it is possible determine DGS at 220 nm. When the pharmaceutical formulation contains Vitamin E (Vit. E) is necessary to use an equations system to be evaluated in sample B.