| Summary: | This work presents the determination of amoxicillin (H3Amox+) in capsules by potentiometric titration. An optimized method was done with a standard amoxicillin solution that was title with NaOH solution. The initial pH was 4.35. As expected, the first equivalence point was not observed, because the fraction of H3Amox+ was about 2.4%. Thus, HCl solution was added to the system to protonate the zwitterion H2Amox± (98%), and then visualize the first equivalence point. Two inflections were observed, the first one of the neutralization of H3Amox+ e HCl and the second one of the neutralization of the zwitterion. The equivalent volumes were estimated using the first derivative method, and the volume variation (DV) between the equivalent volumes was used to determine the amoxicillin. The results showed 99% of accuracy and coefficient of variation of 7.2%.
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