Determination of ticarcillin levels in serum by high-pressure liquid chromatography.

A high-pressure liquid chromatographic method for determining the concentrations of ticarcillin in serum was developed and compared, with 93 patient sera, to a standard agar well diffusion bioassay. For analysis, serum plus temocillin, the internal standard, were extracted with chloroform-n-amyl alcohol and back extracted into phosphate buffer. A reverse-phase C18 column and an ammonium acetate-methanol mobile phase were used with detection at 242 nm. Reproducibility studies yielded coefficients of variation ranging from 2.4 to 4.7% for low, mid, and high controls. Although cefoxitin, cephalothin, and cefuroxime exhibited retention similar to that of ticarcillin, a wide range of commonly administered antibiotics and other drugs did not interfere. The high-pressure liquid chromatographic assay is an accurate, reproducible method for determining the concentration of ticarcillin in serum during multiple antibiotic therapy or when rapid results are required.