The preparation and storage of ultra high purity hexane for solvent effect gas chromatographic analysis

Abstract

The newly developed dynamic solvent effect (DSE) sampling technique for capillary gas chromatography requires ultra-pure solvents for optimum performance. Hexane, the most popular sol vent for this concentration technique, is not available commercially in a grade of the required purity. Trace impurities present in the freshly purified solvent and those originating from laboratory glassware, storage vials and decomposition of the hexane itself, can lead to grave errors in analytical results after concentration. A goal was set to remove flame ionization detectable impurities less volatile than heptane to levels of 1 ppl09 (m/v) per component and to maximize the shelf life of the purified hexane. Methods investigated for purification include fractional distillation (with simple packed columns and with spinning band columns) as well as frontal elution gas and liquid chromatography. The storage of purified hexane was studied in borosilicate glass flasks with ground glass stoppers and borosilicate glass vials with various cap liner materials, under different conditions of temperature and light. A cheap, simple, and reliable technique for preparing and storing ultra-high purity hexane was developed and tested. The results could help to introduce the DSE technique to other laboratories specializing in trace analysis. Other analytical techniques that rely on achieving high sensitivity by evaporative concentration of hexane solutions could also benefit from the findings.