2.3 Conversion factors 1 mg chloroform/m3 air = 0.204 ppm at 25 °C and 101.3 kPa (760 mmHg) 1 ppm = 4.9 mg chloroform/m3 air 2.4 Analytical methods Many analytical methods for the determination of chloroform residues in air, water and biological samples have been reported. Table 2 summarizes some of the procedures used in the literature for sampling and determining chloroform in different media. The detection limits are included in Table 2. Although all of these methods were developed to detect chloroform at very low levels, some of them can be used only in cases where chloroform is present at relatively high levels. Since chloroform is very volatile, care must be taken while sampling and handling samples to prevent any chloroform from being lost during such procedures. In this case, accuracy depends very much on the repeatability of the method being used. All but one of the methods given in Table 2 use gas chromatographic techniques with electron capture detection (ECD), flame ionisation detection (FID), photo-ionisation detection (PID) or mass spectrometry (MS) for Table 2. Sampling and analysis of chloroform Medium Sample method Analytical method Detection limit Sample size Comments Reference Air aspiration velocity of MIRAN-infrared 300 µg/m3 can be used only when Lioy & Lioy 28 litres/min, trajectory spectrometer CHCl3 is presented at (1983) of 20 m high levels Air direct injection GC with a 0.5 µg/m3 5 ml injected method involves the use of Lasa et al. coulometric ECD a continuously operating (1979) automatic GC monitor Air direct injection, GC with two > 0.4 µg/m3 8 ml injected efficiency followed from Lillian & calibration gas used for ECDs installed (estimated) signal ratios of the Singh (1974) reliability serially two ECDs Air AIRSCAN/PHOTOVAC GC-PID 0.5 µg/m3 0.05-1 ml portable machine, suitable Leveson et direct injection for field monitoring al. (1981) Air adsorption on activated GC-ECD approximately 1 m3/24 h in 1984 the draft standard NNI (1984) charcoal, desorption 0.1 µg/m3 NVN 2794 needed to be with CS2 tested for usefulness Air adsorption on Porapak-N, GC-ECD 1 µg/m3 20 litres advantage of methanol is the Van Tassel et desorption with 1-2 ml absence of a background al. (1981) methanol signal in the ECD Air adsorption on Porapak-N, GC-ECD estimated to 0.3-3 litres confirmation of results by Russell & thermal desorption at be 0.05 µg/m3 use of GC-MS Shadoff (1977) 200 °C Air adsorption on GC-ECD-FID two approximately 1-3 litres Heil et al. Chromosorb-102, thermal detectors 0.06 µg/m3 (1979) desorption at 150 °C positioned in parallel Table 2 (contd) Medium Sample method Analytical method Detection limit Sample size Comments Reference Air adsorption on Tenax, GC-FID 0.08 µg/m3 2 ml injected Kebbekus & sample rate 10-15 ml/min, GC-MS Bozzelli (1982) thermal desorption and cryofocusing Air adsorption on Tenax-GC, GC-MS 0.2 µg/m3 20 litres Krost et al. cooled with liquid (1982) nitrogen, thermal desorption at 270 °C Air adsorption on activated GC-FID with 0.15 mg up to 30 these two types of detection Morele et coal, desorption with TCEP, detector litres can be appeared to complement al. (1989) CS2, using Chromosorbsen sitivity sampled each other methylcyclohexane as IS column adsorption on activated GC-ECD with 5% 2 µg is coal, desorption with CV17, Chromosorb minimum ethanol, using column quantifiable trichloroethylene as IS value Air collection on charcoal, GC-FID 0.01 mg per up to 15 suitable for simultaneous US NIOSH desorption with CS2 using sample litres can be analysis of two or more (1984) n-undecane as IS estimated sampled substances Air cold trap, heating the GC-ECD 0.01 µg/m3 30 ml in air samples were taken Harsch & cold trap cold trap in the stratosphere Cronn (1978) Air injection into cold trap, GC-MS (SIM) 0.03 µg/m3 100 ml in Cronn & heating the cold trap cold trap Harsch (1979) Table 2 (contd) Medium Sample method Analytical method Detection limit Sample size Comments Reference Air cold trap after desication GC-PID-ECD-FID, 0.005 µg/m3 1 litre during the process the Rudolph & with magnesium 3 detectors column is kept at -103 °C Jebsen (1983) perchlorate, heating the placed (cryofocusing) cold trap to 257 °C sequentially Breath collection on Tenax GC GC-MS 0.11 µg/m3 suitable for quantitative Pellizzari cartridge, thermal analysis, one sample in et al. desorption 1.5 h (1985b) Water headspace, CH2Br2 was headspace GC-ECD 0.02 µg/litre 500 µl suitable for routine Herzfeld et used as IS injected analysis over a wide range al. (1989) of differently composed river waters Water pentane extraction GC-ECD using 1 µg/litre 100 ml suitable for routine Oliver (1983) 2 mm x 4 mm i.d. extracted with measurements in column backed with 10 ml pentane, drinking-water Squalane on 24 litres of Chromosorb P extract used for injection Water liquid-liquid extraction GC with a Hall 0.10 µg/litre 3 µl injected suitable for routine Mehran et al. with pentane electrolyte analyses (1984) conductivity detector, Tenax-GC column Water direct aqueous injection GC-ECD with a 0.02 µg/litre 2 µl injected suitable for analyses of Grob (1984) of sample into GC fused silica halocarbons in the 0.01-10 capillary column ppb range Table 2 (contd) Medium Sample method Analytical method Detection limit Sample size Comments Reference Water direct aqueous injection GC-ECD with a 0.1 µl/litre 1 µl injected easy, fast and reliable Temmerman & of sample into GC methyl-silicone technique for everyday Quaghebeur fused silica quality control (1990) capillary column Aqueous diethyl ether extraction GC-MS with a < 1 µg/litre 200 ml suitable for water and Meier et al. with 25 µg fused silica and recovery extracted, homogenized environmental (1985) p-bromofluorobenzene capillary column efficiency of extract samples as IS 0.85 concentrated to 1 ml, 2 µl injected Blood headspace, magnesium headspace 0.0225 µg/litre 200 µl suitable for direct Aggazzotti sulfate heptahydrate and GC-ECD, with (2.5 times injected measurements of CHCl3 et al. n-octyl alcohol were Chromosorb standard (1987) added to the plasma W AW column deviation) Blood passing inert gas over GC-MS 3 µg/litre 1-10 ml suitable for quantitative Pellizzari warmed blood sample, analysis of CHCl3 in et al. collection on Tenax-GC, blood (1985a) thermal desorption Blood diethyl ether extraction GC-MS with a qualitative (no 1-5 ml, suitable for identification Mink et al. plasma (1:1) with 3 different fused silica detection limit extract of CHCl3 in biological (1983) and internal standards added capillary column was given) concentrated samples stomach to the concentrated to 1 ml of contents extract of which 2µl is injected Table 2 (contd) Medium Sample method Analytical method Detection limit Sample size Comments Reference Tissue maceration in water, GC-MS 6 µg/kg 5 g suitable for semi- Pellizzari collection on Tenax-GC, quantitative analysis of et al. thermal desorption chloroform in tissues (1985a) Urine pentane extraction GC-ECD < 1 µg/litre 2 µl of convenient and sensitive Youssefi extract means for determining et al. injected light halogenated (1978) hydrocarbons Fish extraction with pentane GC-ECD with a 1 µg/kg in 2 µl extraction efficiency of Baumann and isopropanol, fused silica fresh injected 67% Ofstad et bromotrichloromethane capillary column material al. (1981) used as IS Abbreviations: ECD = electron capture detector; FID = flame ionisation detector; GC = gas chromatography; IS = internal standard; MS = mass spectrometry; PID = photo-ionisation detector; SIM = selected ion monitoring measuring chloroform residues. Only the first method listed depends on the use of a MIRAN-infrared spectrometer. The sensitivity of this method is very poor. 2.4.1 Sampling and analysis in air The methods reported in Table 2 for sampling and analysis of chloroform levels in air can be grouped into four different categories. 18.104.22.168 Direct measurement In this type of procedure, air is aspirated or injected directly into the measuring instrument without pretreatment. Although these methods are simple, they can be used only when chloroform is present in the air at relatively high levels (e.g., urban source areas, see section 5.1.1). 22.214.171.124 Adsorption-liquid desorption Air samples analysed for their chloroform levels are conducted through an activated adsorbing agent (e.g., charcoal or Porapak-N). The adsorbed chloroform is then desorbed with an appropriate solvent (e.g., carbon disulfide or methanol) and subsequently passed through the gas chromatograph (GC) for measurement. 126.96.36.199 Adsorption-thermal desorption In this technique, air samples are also passed through an activated absorbing agent (e.g., Tenax-GC, Porapak-Q, Porapak-N or carbon molecular sieve). The adsorbed chloroform is then thermally desorbed and driven into the GC column for determination. 188.8.131.52 Cold trap-heating In this type of procedure, air samples are injected into a cold trap (liquid nitrogen or liquid oxygen are used for cooling). The trap is then heated while transferring its chloroform content into the packed column of a GC for measurement. 2.4.2 Sampling and analysis in water Several methods of sampling and analysing water for chloroform content are included in Table 2. In some of these methods, water samples are directly injected into a wide bore or fused silica capillary column to which an ECD is attached. In some other water analysis procedures mentioned in Table 2, the chloroform in the water samples is first extracted by means of a non-polar, non-halogenated solvent (e.g., n-pentane). Samples of the obtained extracts are then injected into the GC for determining chloroform. In another procedure, referred to as "close-loop-stripping analysis" (CLSA), chloroform is removed from the water sample by purging it with a large volume of a gas (e.g., nitrogen); the gas is then passed through an adsorption tube and subsequently analysed by GC-MS. Using this latter method, a million-fold concentration can be achieved, so that chloroform can be quantified even at very low levels. A headspace GC technique with ECD has also been used for measuring chloroform levels in water samples (see Table 2). 2.4.3 Sampling and analysis in biological samples 184.108.40.206 Blood and tissues Several procedures for determining chloroform in blood and tissue samples are presented in Table 2. A headspace GC technique has been used for direct measurement of chloroform in plasma obtained from subjects exposed to low levels in air (Aggazzotti et al., 1987). The second procedure (Kroneld, 1985) depends on liquid-liquid extraction of chloroform from blood samples and subsequent injection of the extract into a GC system for quantification. In the method of Pellizzari et al. (1985a), chloroform is evaporated by passing an inert gas over a warmed plasma or macerated tissue sample with adsorption of the vapour on a Tenax GC column, and is then recovered by thermal desorption and analysed by GC-MS. 220.127.116.11 Urine Youssefi et al. (1978) measured chloroform concentration in urine using pentane extraction and GC-ECD analysis.