Gas chromatography (GC) is an analytical technique that has undergone numerous improvements since its introduction in 1903 [1]. One approach to improving GC is through the use of cryo-focusing or cryo-enrichment [2], which involves cooling down a portion or all of the GC column to enhance various aspects of chromatographic analysis. A new and improved module was developed, featuring a two-stage cryo-cooler and improved temperature control capabilities. The performance of this improved module was evaluated by developing and validating a method for the measurement of α-pinene and β-caryophyllene in Cannabis Sativa plants [3]. The aim of this study was to improve upon previous GC cryo-enrichment techniques and apply this improved method to the analysis of these terpene compounds in Cannabis Sativa plants.
An in-house GC cryo-enrichment module was developed and constructed. It is an add-on device that can be attached to a standard GC system via a heated transfer line (as shown in Figure 1). The module includes a custom-made aluminum column holder that sits on top of a cryo-cooled aluminum block. The aluminum block is cooled to -60 °C using a SP Scientific FC100 Flexi-Cool immersion cooler. The column holder contains a nichrome wire heater and is controlled by a stepper motor that moves the holder between cooling and heating positions. During sample injection, the column holder is pressed down onto the cryo-cooled aluminum block and maintained at -60 °C. After multiple injections, the column holder is raised by the stepper motor and heated to 150 °C. The GC column is then passed from the GC system through the transfer line, wrapped around the column holder and returned to the GC system via the same transfer line.
To test the performance of the system, method for terpene analysis with GC was created and validated. The method was found to be precise, accurate, sensitive, linear, and have low limits of detection and quantification. The cryo-enrichment module allowed for multiple injections of the sample, resulting in a higher sensitivity and concentration of the analytes in the GC analysis. Overall, the improved cryo-enrichment module and method for measuring α-pinene and β-caryophyllene in Cannabis Sativa were proven to be an efficient enhancement over previous cryo-enrichment techniques.