Determination of aspoxicillin (TA-058) by high-performance liquid chromatography. Stability at different temperatures

A rapid and sensitive HPLC-method has been developed for the determination of serum concentrations of aspoxicillin (TA-058), a new semisynthetic beta-lactam antibiotic. Aspoxicillin was chromatographed with a phosphate buffer/methanol (92:8 v/v) mobile phase and a C-18 reversed phase column and was detected at a wavelength of 220 nm. The stability of aspoxicillin in serum and buffer at different temperatures was studied over a time period of 3 months. Furthermore, the degradation of aspoxicillin versus piperacillin was determined in serum and buffer at 37 degrees C. Aspoxicillin remains stable only at -70 degrees C whereas degradation has been observed at -20 degrees C and 4 degrees C. At 37 degrees C, 20% of aspoxicillin is degraded in serum within 24 h whereas piperacillin is completely degraded under the same conditions.