Make‐up gas influence on the signal behavior of the Vacuum ultraviolet detector for gas chromatography

Abstract

A vacuum ultraviolet absorbance detector features the addition of the make‐up gas whose purpose is to decrease the diffusion of analytes in the flow cell. It has been previously demonstrated that the vacuum ultraviolet detector VGA 100 is a concentration‐sensitive detector for which the signal area is inversely proportional to the total flow in the flow cell. In this work, the signal behavior in the new generation vacuum ultraviolet detector, which features changed configuration for the introduction of make‐up gas, was explored. Contrary to previous instruments, a non‐linear relationship between the detector signal area and the inverse of the total flow in the flow cell (carrier gas flow + make‐up gas flow) was observed. To explain these observations, we have investigated the behavior of the detector in combination with one‐dimensional and two‐dimensional gas chromatography. Based on the results obtained, it was concluded that in these next‐generation instruments, flow in the flow cell cannot be regarded as a simple sum of the gas chromatography column flow and the total make‐up flow. After making modifications to the estimation of the total effective flow in the flow cell, a linear relationship between the signal area and the inverse of the flow in the flow cell was recovered.