Evaluation of Commercial Solid-Phase Extraction (SPE) Carrier Materials for the Selective Automated Enrichment of Monoterpenoides and their Analysis in Cough Drops, Mouthwashes and Bath Additives by Gas- Chromatography Mass Spectrometry (GC-MS)

For sample preparation solid-phase extraction (SPE) became very popular during the 1980s and 1990s. Because method development and its optimization is very time consuming, in most cases C18 is used as standard carrier material without knowing if it possesses the highest efficiency. Therefore detailed studies with different stationary phases are necessary for optimal recovery rates. Due to the resulting high number of samples, automation is of crucial importance. In the study described, the extraction of five monoterpenoids (myrcene, citronellal, p-cymene, menthol and thymol) out of an ethanolic solution was optimized using automated SPE. An automated robotic system, the MEA Personal Purification System from PhyNexusTM Inc. (http://www.phynexus.com/), was adopted for high-throughput SPE. It allows the simultaneous automatic extraction of 12 samples in parallel employing different carrier materials. Additionally, critical parameters of automation (speed, volume uptake, skipping of drying step) were variegated to obtain optimal recovery rates. Furthermore, extraction efficiency was compared with manual handling to evaluate its performance. The application of 18 different SPE carrier materials, C18 Hydra, C18 ec, C8, C4, C2, C6H5, C6H11 ec, NO2, CN, NH2/C18, Diol, HR-P, EASY, PA, Florisil, Davisil, Strata-X and cellulose pointed out huge differences in extraction efficiency. Finally, the optimized automated procedure was applied for the enrichment of monoterpenoides and their analysis in selected real samples including cough drops, mouthwash and bath additives by gas-chromatography mass spectrometry (GC-MS).