Quantitative Methoxypyrazine Analysis

Quantitative Analysis. To study those factors that influence the occurrence of methoxypyrazines, it was necessary to be able to quantify them. Furthermore, it was desirable that this be possible even at the lowest levels that might be relevant. This indicated a need for their quantitative analysis to extend to concentrations below their sensory detection threshold of 1-2 ng/L, preferably by an order of magnitude. Accurate quantitative analysis at such extremely low analyte concentrations is difficult to achieve. If a moderate sample size is to be used, and if the analysis is to cope with some losses in isolation, then the technique needs to have a detection limit of a few picograms. Furthermore, it must provide quantitative data with adequate accuracy and precision for meaningful interpretation. 

Kotseridis, Y.S., Spink, M., Brindle, I.D., Blake, A.J., Sears, M., Chen, X., Soleas, G., Inglis, D., and Pickering, G.J. (2008). Quantitative analysis of 3-alkyl-2-methoxypyrazines in juice and wine using stable isotope labelled internal standard assay, / Chromatogr. A, 1190,294-301. 

Minor Methoxypyrazines. Stable isotope-dilution mass spectrometry has also allowed quantitative analysis of 2-methoxy-3-(l-methylpropyl)pyrazine (2) sec-butylmethoxypyrazine) and 2-methoxy-3-(l-methylethyl)pyrazine (3) (isopropyl-methoxypyrazine) in grapes and wines. The corresponding trideuterated isopropyl-methoxypyrazine (6) is used in addition to the trideuterated isobutylmethoxypyrazine 5 to provide more accurate quantitative analysis of the isopropyl compound (7, 10,... 

Fig. 2. Trideuterated methoxypyrazines, used as internal standards in quantitative wine analysis by isotope-dilution mass spectrometry, and the corresponding chloropyrazines used in their synthesis...

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