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 CCl 4 and CHCl 3 in biological material and expired air and principally for use in the well-known CCl 4-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 CCl 4 and CHCl 3 was used for calibration in the range 5–500 μg per gram of biological material. The method is reasonably accurate, e.g. CCl 4 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 CCl 4 and CHCl 3 permits determination of microsamples (50–500 μl) 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 CCl 4 or CHCl 3 per millilitre of toluene. The accuracy of the method is high, e.g. in blood CHCl 3 101 ± 9.5 (S.D.)%, CCl 4 100 ± 15.2%, as is the precision: rel. S.D. ca. 5% for both CCl 4 and CHCl 3. For elimination studies, CCl 4 and CHCl 3 in air may be trapped in toluene and determined by ECD. Recovery of known amounts of CCl 4 and CHCl 3 from an air chamber was high: 100 ± 4.7 (S.D.)% and 111 ± 10.9%, respectively, and reduction of CCl 4 to CHCl 3 by the trapping system negligible (<0.01%). Cross-checking of the methods and application to the commonly used CCl 4 hepatotoxicity model is demonstrated.