Our valve technology includes a port to which a gas, very often the carrier gas, is connected. There is consequently no need to use multiple valves to achieve this functionality. All of this is done with one valve.
In this position, this gas is used to vent away from the trap a large proportion of the sample matrix. Consequently, only a small residual proportion of the sample matrix is injected into the chromatographic column.
This embedded step provides many advantages. It allows to simplify chromatography by reducing the sample matrix loading on the chromatographic column. It also reduces the number of valves. This simplifies the chromatographic separation with impurities which have an elution time close to the sample matrix. Also, some sample matrix can pollute the column which impacts chromatography over time and causes noise. Such an example is ambient air which contains high levels of moisture.
In other cases, such as VOC or hydrocarbon analysis in air or oxygen, it allows to vent away the oxygen from the trap before heating. At high temperature, the oxygen can react with some molecules and impact the measurement.