Odorant Quantitation

Various amounts of the respective sample (0.05–500 mL) were used depending upon the amounts of the target compounds estimated in preliminary experiments. The samples were spiked with defined amounts of the stable isotopically substituted odorants (resulting in concentrations of 1–5 μg/mL of each compound in the extract). After equilibration for 30 min, the volatiles and internal standards were extracted with diethyl ether and isolated by SAFE,²⁸ as described above. Compounds were analyzed using either the one-dimensional GC–MS system (11, 16, 22–24, 31, and 42) or the heart-cut GC–GC–MS system (2, 4–5, 7–10, 13–15, 17, 20–21, 25, 28–30, 32–36, 38–40, and 43–44).

Peak areas of the analytes (8–10, 14–15, 20–21, 25, 33, and 39) and the respective internal standards were calculated from the extracted ion chromatograms using the quantifier ions detailed in Table 1. The concentration of each target compound was then calculated from the area counts of the analyte peak, the area counts of the standard peak, the amount of Dornfelder sample used, and the amount of standard added, by employing a calibration line equation (Table 1). To obtain the calibration line equation, solutions of the reference analyte and standard were mixed in different concentration ratios and analyzed under the same conditions followed by linear regression. Detailed information, e.g., on quantifier ions, for compounds 2, 4–5, 7, 11, 13, 16–17, 22–24, 28–32, 34–36, 38, 40, and 42–44 are given in the previous publication.¹⁷

Compound 1 was quantitated enzymatically using an ultraviolet (UV) test kit (R-Biopharm, Darmstadt, Germany).