Page 434 - Multidimensional Chromatography

426 Multidimensional Chromatography

provides an excellent description of the principles of comprehensive two-dimen-
sional GC as applied to a forensic problem. The instrument consists of a typical gas
chromatograph, modified by the addition of a thermal modulator as a switching
valve after the first column. The effluent is switched into the second column at regu-
lar intervals. A flame-ionization detector (FID) was used for detection and the entire
system required microprocessor control. The second dimension allowed these work-
ers to separate compounds by both volatility and polarity in a single run, thus
enabling over 500 separate peaks to be resolved, and in this way they were able to
make a probable match as between various oil spill samples and a marine diesel fuel
standard.
Comprehensive two-dimensional GC has also been employed for the analysis of
pesticides from serum, which, although not strictly a forensic analytical ‘problem’,
provides an example of the promise of this technique to forensic applications, such
as the analysis of drugs of abuse (40). Two-dimensional gas chromatograms of a
17-pesticide standard and an extract from human serum are shown in Figure 15.13.
The total analysis time of about 5 min, high peak capacity and the separation of all

Figure 15.13 Comprehensive two-dimensional GC chromatogram of a supercritical fluid
extract of spiked human serum. Peak identification is as follows: 1, dicamba; 2, trifluralin; 3,
dichloran; 4, phorate; 5, pentachlorophenol; 6, atrazine; 7, fonofos; 8, diazinon; 9,
chlorothalonil; 10, terbufos; 11, alachlor; 12, matalaxyl; 13, malathion; 14, metalochlor; 15,
DCPA; 16, captan; 17, folpet; 18, heptadecanoic acid. Adapted from Analytical Chemistry, 66,
Z. Liu et al., ‘Comprehensive two-dimensional gas chromatography for the fast separation and
determination of pesticides extracted from human serum’, pp. 3086–3092, copyright 1994,
with permission from the American Chemical Society.