US Patent 7347936 Liquid chromatograph

A liquid chromatograph has switching valves as a flow passage switching mechanism and an automatic sampler as an injection section. The liquid chromatograph can switch, by switching the switching valves between a concentration flow passage for concentrating the sample injected by the automatic sample via a flow passage which connects the automatic sampler to the trapping column; a concentration analysis flow passage for separating and analyzing the concentrated sample on a per-composition basis which connects the trapping column to the analysis column; and a direct analysis flow passage by separating the sample on a per-composition basis which connects the automatic sampler to the analysis column.