This article provides a critical overview of current methods to quantify essential oil components. The fields of application and limits of the most popular approaches, in particular relative percentage abundance, normalized percentage abundance, concentration and true amount determination via calibration curves, are discussed in detail. A specific paragraph is dedicated to the correct use of the most widely used detectors and to analyte response factors. A set of applications for each approach is also included to illustrate the considerations.of linalool, linalyl acetate, β-pinene, sabinene, limonene and α-terpineol. 9 Figure 3 reports the enantioselective-gas chromatography-total ion mass spectrometry (ES-GC-SCAN-MS) profile of an adulterated bergamot EO together with those of linalool and linalyl acetate and α-terpineol in enantioselective-gas chromatographyselected ion monitoring mass spectrometry (ES-GC-SIM-MS) and their enantiomeric ratios.Normalized % abundance can be assumed to be a 'quantitative' comparison of GC profiles, but for some applications it is not sufficient to satisfy all quantitation Figure 3. ES-GC-TIC-MS profile of bergamot EO. (A) Peak identification: 1, α-pinene; 2, β-pinene; 3, sabinene; 4, limonene; 5, linalool; 6, linalyl acetate; 7, α-terpineol; a, (R) enantiomer; b, (S) enantiomer. ES-GC-SIM-MS profiles and enantiomeric ratios of (B) linalool and linalyl acetate (80, 93, 121 m/z) and (C) α-terpineol (59, 93, 136 m/z). Analysis conditions: column, heptakis-2,3-di-O-ethyl-6-O-t-butyldimethylsilyl-β-CD, 30% in PS086 (Megadex, Mega ® ), 25 m × 0.25 mm i.d., 0.25 μm film thickness; temperature programme, 50°C, rising at 2°C/min to 200°C, then held for 5 min; injection mode, split (ratio 1:50); injector temperature, 220°C; EI mode, 70 eV; ion source temperature, 230°C; carrier, helium; flow rate, 1.0 ml/min in constant flow mode. Full scan mode: scan range, 35-350 m/z; SIM mode: dwell time, 0.2 sFigure 4. GC profile of peppermint EO. Analysis conditions: Megawax (60 m × 0.25 mm i.d., 0.25 μm film thickness); temperature programme, 75°C for 8 min, rising at 4°C/min to 220°C, then held for 5 min; injection mode, split (ratio 1:100); injector temperature, 230°C; detector (FID) temperature, 250°C; carrier, H 2 ; flow rate, 1.5 ml/min in constant flow mode

Headspace sorptive extraction (HSSE) and stir bar sorptive extraction (SBSE), two recently introduced solventless enrichment techniques, have been applied to the analysis of the headspace of Arabica roasted coffee and of the headspace of the brew and of the brew itself. In both HSSE and SBSE enrichment is performed on a thick film of poly(dimethylsiloxane) (PDMS) coated onto a magnet incorporated in a glass jacket. Sampling is done by placing the PDMS stir bar in the headspace (gas phase extraction or HSSE) or by immersing it in the liquid (liquid phase extraction or SBSE). The stir bar is then thermally desorbed on-line with capillary GC-MS. The performance of HSSE and SBSE have been compared through the determination of the recoveries and relative abundances of 16 components of the coffee volatile fraction to classical static headspace (S-HS) and to headspace and in-sample solid phase microextraction (HS-SPME and IS-SPME, respectively) applying the fibers PDMS 100 microm, Carbowax/divinylbenzene 65 microm (CW/DVB), Carboxen/PDMS 75 microm(CAR/PDMS), polyacrylate 85 microm(PA), PDMS/divinylbenzene 65 microm(PDMS/DVB), and Carboxen/divinylbenzene/PDMS 50-30 microm(CAR/PDMS/DVB). In all cases, HSSE and SBSE gave higher recoveries, and this is entirely due to the high amount of PDMS applied.

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This article is a short overview of the state of the art in essential oil analysis. Several aspects of the analysis of essential oils and volatile fraction of vegetable matrices are here critically discussed. The following topics are dealt with: steam distillation, hydrodistillation and headspace sampling for sample preparation, and fast-GC, fast-GC-qMS analysis, enantioselective GC, multidimensional GC techniques and GC-isotopic ratio mass spectrometry (GC-IRMS) for analysis and quantitation.

ABSTRACT:The main purpose of any chromatographic analysis is to resolve mixtures of compounds into less complex mixtures or ultimately into pure components. In addition to this function, the chromatographic system can provide retention data which serve as complementary information for the positive identification of resolved components. The need to express gas chromatographic retention data in a standardized system has long been recognized and retention index values presented to be a valuable parameter. Those values are mainly calculated by applying the equations proposed by Kováts, for isothermal analysis, and van den Dool and Kratz, for programmed gas chromatographic runs. In general, these indices denote the retention behaviour of the compounds of interest according to a uniform scale determined by a series of closely related standard substances. The use of retention indices in the flavour and fragrance field is well-documented, and they are widely applied for the comparison of results between laboratories, as well as to characterize stationary phases.