Dr. Werner Engewald discusses the phenomenon of cross-over, or changes in elution order following modification of the GC temperature program. This effect has been observed for decades but the physio-chemical background still is not well understood. In this article Dr. Engewald explores the theory and potential explanations for the cross-over phenomenon.
Hydrogen offers a number of benefits over helium as a carrier gas for gas chromatography. With basic safety measures in place, labs can safely use hydrogen for faster chromatography. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
Numerous articles have been published on faster methods for gas chromatography (GC), yet uncertainty remains on how best to speed up separations. Here, Dr. Hans-Gerd Janssen clarifies the confusion surrounding fast GC and recommends a strategic approach based on 3 steps: 1) minimizing resolution to a value just sufficient, 2) maximizing the selectivity of the chromatographic system, and 3) implementing a method that reduces analysis time while holding resolution constant.
The rule of using empty liners with splitless injection was developed in the days of manual injections. Does it still hold true? Sample evaporation is explored. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
Proper sample evaporation in the injection port cannot be assumed. Principles governing evaporation are discussed. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
A detailed discussion of how syringe needle length impacts quantitative analysis. Includes optimal needle lengths for different scenarios. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
Discussion of the origins of the retention gap, a length of uncoated tubing used to focus large volume injections and prevent band broadening. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
Even validated methods run on certified equipment are unlikely to be foolproof. Real quality assurance needs to be based on direct verification using internal standards and control samples. By Dr. Konrad Grob, Kantonales Laboratory, Zurich
Micropacked columns are 1-2 meter, 0.75-1.0mm ID packed stainless steel columns with performance characteristics intermediate between conventional packed columns and capillary columns. They are inexpensive, very durable, and easy to install and operate. They have a wide range of applications, but are especially useful for analyses of gas mixes, including sulfur compounds or light hydrocarbons, for which a packed column is needed to obtain baseline separations of sample components.
Scaling down column size is simple to do and can help reduce solvent use. Here is an easy-to-follow example that teaches you how to reduce column internal diameter.
