A rapid and sensitive high-pressure liquid chromatographic method for monitoring josamycin levels in plasma.

In this study a new high-pressure liquid chromatographic method for monitoring plasma levels of josamycin is described. Josamycin propionate was used as the internal standard. After being extracted from plasma by chloroform at an alkaline pH, the compounds were easily separated on a reversed-phase column C8. The mobile phase was methanol: citrate-phosphate buffer 0.01 M pH 2.8 (85:15 v/v); and the wavelength 232 nm. The retention time was 2.2 min for josamycin and 2.7 min for josamycin propionate; the chromatogram lasted about 3.5 min. Using this method, concentrations of josamycin up to 0.3 microgram/ml were determined.