Resumo

Introdution: Ampicillin sodium is a β-lactam antibiotic for parenteral use, belonging to the penicillin group of drugs. Comparison of methods is often necessary to check for significant differences among the results generated by different methods. The turbidimetric assay is a microbiological method which provides information about the potency of the pharmaceutical product by measuring the turbidity (absorbance) caused by inhibition of microorganism by the antimicrobial. The HPLC, in turn, is a chromatographic method which occupies a prominent place because of its great ability to make the separation, identification and quantification of chemical species. Microbiological methods must be applied in parallel to the physico-chemical, in order to ensure the efficacy of antimicrobial agents. Material and Methods: For turbidimetric assay, in six test tubes containing 10 mL of TSB broth, was added 600 μL of a Staphylococcus aureus 25923 suspension, standardized to 25% transmittance in spectrophotometer (580 nm). In three of these tubes was added 200 μL of standard solution and in the other three, 200 μL of sample solution at the same concentrations of standard solutions (2.0; 4.0 and 8.0 μg mL^-1). The test-tubes were incubated in a shaker, in water bath, for 4 hours, and then the absorbances were checked in a spectrophotometer (530 nm). The HPLC method, in turn, employed water: ethanol (60:40, v/v) as mobile phase, pumped at a flow rate of 0.5 mL min^-1. A C18 column was used as stationary phase, and the UV detection was performed at 210 nm. The range of concentrations used was 70-120 μg mL^-1. The comparison of the methods was statistically evaluated by performing the F and T tests, at a significance level of 5%, between the content measurements of each method. Results and Discussion: Through statistical analysis, it might be noted that the value of calculated t (1.43) was lower than the tabulated t (2.78). Therefore, it can be stated that the validated methods are equivalent for the ampicillin sodium determination in the pharmaceutical dosage form. Conclusion: The methods are interchangeable, both suitable for the quantitative determination of ampicillin sodium in powder form for injectable preparation. Both methods present advantages and these aspects should be evaluated to choose the best method to quantify a drug specifically an antimicrobial medicine.