Moreover, most of the available methods are based on involvement of buffer which not favourable for column efficiency. Keeping, in view of this an attempt was made to develop a simple, precise and accurate RP-HPLC

method for the simultaneous estimation of piperacillin and tazobactam in pharmaceutical dosage forms. The reference sample of piperacillin and tazobactam is a kind gift from V.V. MED Laboratories, Hyderabad. The formulation ZOSYN (BDI Pharma) was procured from the local market, acetonitrile, methanol and orthophosphoric acid used were of HPLC grade and purchased from Merck Specialties Private Limited, Mumbai, India. Analysis of the drug samples were carried out using PEAK 7000 isocratic HPLC with rheodyne manual sample injector with

switch (77251) and the column used was GSK1210151A chemical structure Analytical column kromosil 100-5 BAY 73-4506 mw C18.250 × 4.6 mm. Electronic balance-ELB300 for weighing the samples and DIGISUN for pH measurements. The software used for HPLC data processing is LC 7000. Proper selection of the stationary phase depends upon the nature of the sample, molecular weight and solubility. Piperacillin and tazobactam were analysed by RP columns. Chromosil C18 column (250 mm × 4.6  mm, 5 μm) was selected. Various combinations of methanol, acetonitrile and 1% orthophosphoric acid were tested. Finally the mixture of MeOH: ACN: 1% OPA in the ratio 30:50:20 was selected as a mobile phase and the final pH was at 4.2. Composition of mobile phase on the retention time of piperacillin and tazobactam were thoroughly investigated. The concentration of the MeOH: ACN: 1% OPA (30:50:20) were optimized to give symmetric peak with short runtime. UV detection wavelength was 226 nm, flow rate was 1.0 mL/min, injection volume was 20 μL, retention time was 10 min, and the resulting chromatogram was

shown in Fig. 1. Pure standards of piperacillin and tazobactam were used as external standards in the analysis. Different concentrations of the standards were used based on the range required to plot a suitable calibration curve. About 100 mg of piperacillin and tazobactam drug because transferred into a 100 ml volumetric flask and made up to the mark by using methanol. The flask containing standard stock solution was sonicated for 10 min to degas it. The standard solution was then filtered with 0.45 μm membrane filter paper. A series of different dilutions (50–100 ppm) were prepared using above stock solution with selected mobile phase (Methanol, acetonitrile and 1% orthophosphoric acid in the ratio 30:50:20 (v/v/v)) and filtered through 0.45 μ nylon filter. 50 ppm of sample solution was prepared by accurately weighing the required amount of the drug and transferring it into a 100 ml volumetric flask and added mobile phase. The sample solution was then filtered with 0.45 μ nylon filter.