Rapid gas chromatographic method for the determination of nalidixic acid in plasma

Nalidixic acid is mostly used for the treatment of urinary tract infections, but in some cases it is administered intravenously for the-treatment of general infections [I] . In those cases it is necessary to determine the plasma concentration of nalidixic acid, preferably by means of a rapid, simple method. In the literature, fluorimetric [2, 31 and liquid chromatographic [4, 5] methods have been described_ The fluorimetric methods have the disadvantage of not being specific and the recently described high-performance liquid chromatographic (HPLC) method involves a time consuming derivatization step. In this paper we shall describe a gas chromatographic (GC) method that is specific and sensitive enough to determine therapeutic levels in a 1 ml plasma sample within 30 min of receipt of the sample.