Page 37 - Multidimensional Chromatography

Coupled HPLC with HRGC 27

PTV chamber is more easily heated than a capillary column. The introduction of
large volumes with the use of such an injector in solvent-split mode was first investi-
gated in the 1970s. Staniewski, Cramers and co-workers (12–17) demonstrated that
by reducing the injector temperature and by increasing the purge gas during the sol-
vent elimination it was easier to remove solvent, and showed that by using chambers
packed with porous glass beads instead of Tenax TA or Thermotrap recovery of
solutes may be improved.
A different approach was recently introduced by Sandra and co-workers.
(18, 19) for the transfer of large volumes from a liquid chromatograph, to a gas chro-
matograph. This interface consist of a flow cell that was made by modifying an
autosampler vial. The solvent coming from the HPLC unit which contains the
solutes is continuously sampled by the flow cell. When the fraction of interest is
inside the vial, a large-volume injection is made using the PTV device in the solvent-
vent mode. This technique was successfully applied to the analysis of pesticides, as
shown in Figure 2.8 (19).

Figure 2.8 (a) HPLC fractionation of orange oil on Lichrosorb 100 diol. (b) LC–GC-NPD
analysis of peel orange oil (from Florida), contaminated with ethion. Reprinted from
Proceedings of the 20th International Symposium on Capillary Chromatography, F. David
et al., ‘On-line LC–PTV–CGC: determination of pesticides in essential oils’, 1998, with
permission from Sandra P.