A comparison of semi‑quantitative methods suitable for establishing volatile profles

Abstract

Background: Full scent profles emitted by living tissues can be screened by using total ion chromatograms gener ated in full scan mode and gas chromatography–mass spectrometry technique using Headspace Sorptive Extraction. This allows the identifcation of specifc compounds and their absolute quantifcation or relative abundance. Quanti fcations ideally should be based on calibration curves using standards for each compound. However, the unpredict able composition of Volatile Organic Compounds (VOCs) and lack of standards make this approach difcult. Research ers studying scent profles therefore concentrate on identifying specifc scent footprints i.e. relative abundance rather than absolute quantities. We compared several semi-quantitative methods: external calibration curves generated in the sampling system and by liquid addition of standards to stir bars, total integrated peak area per fresh weight (FW), normalized peak area per FW, semi-quantifcation based on internal standard abundance, semi-quantifcation based on the nearest n-alkane and percentage of emission. Furthermore, we explored the usage of nearest components and single calibrators for semi-quantifcations. Results: Any of the semi-quantifcation methods based on a standard produced similar or even identical results compared to quantifcation by a true-standard for a compound, except for the method based on standard addition. Each method beholds advantages and disadvantages regarding level of accuracy, experimental variability, acceptance and retrieved quantities. Conclusions: Our data shows that, except for the method of standard addition to the biological sample, the rest of the semi-quantifcation methods studied give highly similar statistical results. Any of the methodologies presented here can therefore be considered as valid for scent profling. Regarding relative proportions of VOCs, the generation of calibration curves for each compound analysed is not necessary.