Page 358 - Multidimensional Chromatography

Multidimensional Chromatography in Environmental Analysis 349

Figure 13.6 Direct RPLC analysis of a blank ground water sample spiked with 4.5 ( g l 1
ETU, (a) with and (b) without column-switching. A 60 4.6 mm i.d. column and a 150 4.6
mm i.d. column were used for C-1 and C-2, respectively, with pure water as M-1 and
methanol–0.025 M ammonium acetate (pH, 7.5) (5:95, v/v) as M-2; S-1 and S-2 are the
interfering peaks. Reprinted from Chromatographia, 31, E. A. Hogendoorn et al., ‘Column-
switching RPLC for the trace-level determination of ethylenethiourea in aqueous samples’,
pp. 285–292, 1991, with permission from Vieweg Publishing.

Since only a small fraction of the interfering material reaches the second column
and subsequently the detector, the next analysis can start after the analyte has been
transferred to column 2. This provides a high throughput (about 7 samples per hour).
This method can also be used to analyse soil samples. For instance, fenpropi-
morph, which is a non-polar pesticide with good UV sensitivity but poor selectivity,
has, after treatment, been determined in soil samples (31). In this example, an
amount of soil was extracted overnight with acetonitrile; this was then poured into a
Buchner filter and rinsed with the same solvent. The acetonitrile solution was con-
centrated and, prior to LC analysis, the extract was diluted with water and 100 l
were then injected into the LC system.