Page 361 - Multidimensional Chromatography

352 Multidimensional Chromatography

Figure 13.9 Coupled-column RPLC-UV (215 nm) analysis of 100 l of an extract of a
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spiked soil sample (fenpropimorph, 0.052 mg Kg ). LC conditions: C-1, 5 m Hypersil SAS
(60 m 4.6 mm i.d.); C-2, 5 m Hypersil ODS (150 m 4.6 mm i.d.); M-1, acetonitrile-0.5
% ammonia in water (50 : 50, v/v); M-2, acetonitrile–0.5 % ammonia in water (90:10, v/v);
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flow-rate, 1 ml min ; clean-up volume, 5.9 ml; transfer volume, 0.45 ml. The dashed line rep-
resents the chromatogram obtained when using the two columns connected in series without
column switching. Reprinted from Journal of Chromatography A, 703, E. A. Hogendoorn and
P. van Zoonen, ‘Coupled-column reversed-phase liquid chromatography in environmental
analysis’, pp. 149–166, copyright 1995, with permission from Elsevier Science.

polar metabolite (DIA) and atrazine, a large transfer volume is required and this
leads to a decrease in the selectivity. However, since the more polar compounds are
the major source of interference, separation on C-1 allows the large excess of early
eluting polar interference to be removed and thus improves the selectivity. The ana-
lytes are separated in C-2 by gradient elution because of the difference in polarity.
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The limits of detection are between 0.2 (atrazine) and 0.5 (HA) g l , but it should
be pointed out that only 2 ml of sample are needed. When an off-line C 18 SPE stage
is applied, limits of detection down to 0.02–0.1 g l 1 were reached. Figure 13.10