Comparison of a simplified liquid chromatographic assay of gentamicin in serum with enzyme immunoassay and bioassay.

A sensitive and reproducible high-performance liquid chromatographic (HPLC) method is described for assay of gentamicin in serum using ultrafiltration of serum samples and pre-column derivatization with o-phthalaldehyde. The procedure was compared with a bioassay and an enzyme immunoassay. Coefficients of correlation were 0.98 for HPLC vs. bioassay and 0.97 for HPLC vs. immunoassay. The between-day imprecision (n = 5) was estimated from the coefficients of variation at a concentration of 6 mg/l. Values were 9.4% for the bioassay, 6.5% for the immunoassay and 2.4% for the chromatographic method. The major advantage of the method described is simplified sample preparation and optimal serum extraction. The latter is important in routine use because it prolongs column life and thus reduces costs.