Development and validation of a method to determine amoxicillin in physiological fluids using micellar liquid chromatography

A simple and robust method was developed for the routine identification and quantification of amoxicillin by micellar LC. Amoxicillin, a beta-lactamase inhibitor, is one of the most commonly prescribed drugs in the treatment of urine and skin structure infections. In this work, amoxicillin was determined in urine samples without any pretreatment step in a phenyl column using a micellar mobile phase of 0.10 M SDS and 4% butanol at pH 3. A UV detection set at 210 nm was used. Amoxicillin was eluted at 5.1 min with no interference by the protein band or endogenous compounds. Linearities (r >0.9998), intra- and interday precisions were determined (RSD (%) 0.4-2.7% and 0.3-5%, respectively, in micellar media, and 0.14-2.6% and 0.13-6%, respectively, in urine), and robustness was studied in the method validation. LOD and LOQ were 0.04 and 0.1 microg/mL in micellar media and 0.14 and 0.34 microg/mL in urine, respectively. Recoveries in the urine matrix were in the range of 95-110%. The validated method proved to be reliable and sensitive for the determination of amoxicillin in urine samples.