A Simplified Approach in Flow Controlled Multi-dimensional Gas Chromatography
We introduce a simple and reliable approach for practicing flow controlled multi-dimensional gas chromatography. The approach eliminates the need for flow resistance balancing. Flow resistance balancing between the flow restrictor and the analytical column employed in the second dimension has been viewed as a necessary requirement for proper Deans switch operation. It is a time consuming step and at times can be difficult to implement especially without a software calculator. The proposed approach is made possible by recent advances in fast pneumatic control systems that are capable of delivering rapid response to abrupt flow changes. It can be employed in a Deans switch configuration or have the Deans switch acts as a generic flow switch to satisfy dissimilar detector flow requirements. Over a carbon number range of nC8 to nC24, a relative standard deviation of less than 0.02% for retention time and less than 4% for area counts were obtained for both the compounds that were “cut” to the second dimension as well as for those remained in the first dimension. In the present article, the utility of the simplified approach was demonstrated with a capillary flow technology based Deans switch with two detectors; an atmospheric pressure flame ionization detector and a reduced pressure mass selective detector. In this configuration, the flow rate of the restrictor is approximately six times higher than that of the flow rate of the secondary column.