Electron-capture gas chromatographic assays of 5-nitroimidazole class of antimicrobials in blood. 
Sensitive and selective electron-capture gas chromatographic methods for the determination of N-1-substituted 5-nitroimidazole class of antiprotozoals from blood are described.  Metronidazole, secnidazole and ornidazole having a hydroxyl function in the N-1 substitution, were converted to their respective trimethylsilyl derivatives before chromatography on an OV-11 column.  Tinidazole and satranidazole, devoid of the hydroxy group but containing a sulphur atom in the molecule, were chromatographed as such on the same stationary phase.  Blood levels as low as 50 ng/ml for all the 5-nitroimidazoles have been measured with good precision.  The methods can be readily utilized for pharmacokinetic studies.