Chloroform Detection and Quantification

http://www.inchem.org/documents/ehc/ehc/ehc163.htm

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.

    2.4.1.1  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).

    2.4.1.2  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.

    2.4.1.3  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.

    2.4.1.4  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

    2.4.3.1  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.

    2.4.3.2  Urine

         Youssefi et al. (1978) measured chloroform concentration in
    urine using pentane extraction and GC-ECD analysis.

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