Analysis of cooking spices in natural waters

Richard G. Keil, Jacquelyn A. Neibauer

Limnol. Oceanogr. Methods 7:848-855 (2009) | DOI: 10.4319/lom.2009.7.848

ABSTRACT: An isolation and quantification technique is presented for the analysis of semi-volatile spices and scents in aquatic waters including thymol, eugenol, limonene, carvacrol, vanillin, and cinnamaldehyde. Compounds are isolated from natural waters by solid phase extraction onto Waters Oasis HLB columns and eluted into ethyl acetate. Recovery efficiencies are >70% for most target compounds. Comparison with liquid-liquid extraction and C-18 solid phase extraction indicates that HLB cartridges are more robust and provide equal or better recoveries for target compounds relative to other approaches. Because the compounds are semi-volatile and prone to losses during solvent evaporation, we do not dry the samples completely before quantification by gas chromatography mass spectrometry. Compounds are analyzed using selected ion monitoring with a sensitivity ~1 pg compound per injection. This equates to a sensitivity of about 2–200 ng L–1 in natural waters, or part-per-billion levels. Column loading and matrix effects are minimal and are accounted for by careful monitoring of volumes and by standard additions during GC analysis. Environmental samples (treated sewage, lake, stream, and fjord samples) show a wide range of compounds and quantities, most in the 10–10,000 ng L–1 range. The artificial spice ethylvanillin, which is commonly used as an internal standard in analysis of woody lignin samples, is found in some natural waters. This is likely a result of the industrial-scale production of this compound for culinary and pharmaceutical use.