Background: Data accuracy in analytical determination is of prime importance. Antibiotic levels are usually obtained in mixtures using chromatographic techniques. Thus, evaluation of data accuracy in mixtures seems necessary. Objectives: The aim of this study was to show how the figure of merits for high performance liquid chromatographic (HPLC) determination of sulfacetamide and sulfadiazine changes, while injecting their mixture compared to those injected individually. Methods: Standard solutions of the mixture of 2 selected sulfonamides as well as each individual solution were injected on ODS2