Two rapid methods for the simultaneous gas-liquid chromatographic determination of carbon tetrachloride and chloroform in biological material and expired air

Abstract

Two simple gas-liquid chromatographic techniques were developed for the simultaneous determination of CCl4 and CHCl3 in biological material and expired air and principally for use in the well-known CCl4-induced hepatotoxicity model: a non-extractive head-space analysis by flame ionization detection (FID) and a single-step toluene extraction using electron-capture detection (ECD). For head-space analysis, blood or liver homogenate is incubated with buffer in sealed reaction vials and the head-space vapour sampled for FID determination. Absolute signal response to CCl4 and CHCl3 was used for calibration in the range 5-500 microgram per gram of biological material. The method is reasonably accurate, e.g. CCl4 in liver homogenate 98 +/- 21.8 (S.D.) %, in blood 94 +/- 13.3%, but the precision is poor (rel. S.D. 10-20%). Air samples in volumes of up to 2 ml may be determined by direct FID injection. The ECD sensitivity of to CCl4 and CHCl3 permits determination of microsamples (50-500 microliters) of blood and liver homogenate by extraction with buffer into toluene containing an internal standard (propyl iodide). The linear range of the detector allowed calibration by peak area ratio in the concentration range (10-1500 ng of CCl4 or CHCl3 per millilitre of toluene. The accuracy of the method is high, e.g. in blood CHCl3 101 +/- 9.5 (S.D.)%, CCl4 100 +/- 15.2%, as is the precision: rel. S.D. ca 5% for both CCl4 and CHCl3. For elimination studies, CCl4 and CHCl3 in air may be trapped in toluene and determined by ECD. Recovery of known amounts of CCl4 and CHCl3 from air chamber was high: 100 +/- 4.7 (S.D.)% and 111 +/- 10.9%, respectively, and reduction of CCl4 to CHCl3 by the trapping system negligible (less than 0.01%). Cross-checking of the methods and application to the commonly used CCl4 hepatotoxicity model is demonstrated.