Page 374 - Multidimensional Chromatography

Multidimensional Chromatography in Environmental Analysis 365

Figure 13.16 LC separation of urban air particulate extract (a), along with the GC/FID chro-
matogram (b) of an oxy-PAC fraction (transferred via a loop-type interface). Reprinted from
Environmental Science and Technology, 29, A. C. Lewis et al., ‘On-line coupled
LC–GC–ITD/MS for the identification of alkylated, oxygenated and nitrated polycyclic aro-
matic compounds in urban air particulate extracts’, pp. 1977–1981, copyright 1995, with per-
mission from the American Chemical Society.

in water by use of the vaporizer/precolumn solvent split gas discharge interface (96).
The fraction from the LC column, eluted by the mobile phase consisting of
water/methanol (15 : 85, v/v), is directly inserted into the PTV interface. The eluent
is vaporized in a chamber kept at a high temperature which depends on the transfer
flow. The transfer line contained packing material, i.e. Carbofrit, for smooth evapo-
ration to occur. This was situated at the top of the properly heated area in order to
prevent the transfer line from entering too far into the hot area. The solvent vapours
were largely discharged through an early vapour exit, driven by the flow of carrier
gas. Solvent/solute separation occurred in the precolumn. An uncoated retention gap
was not necessary since water or water/methanol mixtures do not wet precolumn