In many applications of liquid chromatography (LC), excellent peak shapes are observed with simple, easy-to-use mobile phases and operating conditions. However, some specific combinations of analyte and LC column chemistry can lead to terrible peak shapes and even total adsorption of analytes to components of the LC system such that no peaks are observed at all. In this installment of “LC Troubleshooting”, I discuss two specific cases where an understanding of specific interactions between particular analyte functional groups and LC instruments or column materials is critical to achieving successful separations.
Despite best efforts in 2004 to ban their use, persistent organic pollutants (POPs) remain prevalent across the globe, including in soil. To protect human health, agricultural and environmental soil require careful investigation, but preparing samples for gas chromatography–mass spectrometry (GC–MS) analysis is time-consuming, and mostly done manually. Accelerated solvent extraction (ASE) has been the preferred preparation method for the past few decades, and while we have seen advancements, the method remains manual. Now, new technology offers parallel sample processing, combined extraction and evaporation, and automation—leading to faster analysis, reduced risk of error, and freed-up time for personnel.
Retention and selectivity in gas chromatography (GC) occur because of the thermodynamics of the phase transition from the vapor phase following sample injection to the solution phase of being dissolved in the stationary phase. Analytes then move along the column because the vapor phase is flowing. In this installment, we quickly review the basic thermodynamics underlying separation in GC, and we see how this impacts selectivity and retention. Last month, we saw how seemingly large differences in column polarity may still generate little, or even the opposite, effect on retention and generate confusion and difficulty in method development. This month, we explore this challenge more in-depth using thermodynamics and a freely available online GC simulator.
Peter Schoenmakers and Emanuela Gionfriddo are the winners of the 16th annual LCGC Lifetime Achievement and Emerging Leader in Chromatography Awards, respectively. The LCGC Awards honor the work of leading separation scientists for lifetime achievement and emerging potential. The award winners will be honored in an oral symposium at the Pittcon 2023 conference in March 2023 in Philadelphia, Pennsylvania, USA.
