Improved synthesis of deuterium-labeled alkyl pyrazines for use in stable isotope dilution analysis

Quantitative analysis by GC-MS coupled with the use of stable isotopes as internal standards, so called stable isotope dilution analysis (SIDA), is an extremely accurate and precise way to quantify potent odorants in foods. Despite its many advantages, SIDA is not widely used due to the high cost associated with the purchase and/or synthesis of the isotopically labeled standards. This chapter describes an improved approach for the synthesis of stable deuterium labeled alkylpyrazines. Three deuterium labeled alkylpyrazines, namely [2H5]-2-ethyl-3,5-dimethylpyrazine, [2H5]-2-ethyl- 3,6-dimethylpyrazine and 2,3-diethyl-5-[2H3]-methylpyrazine, whose unlabeled counterparts are previously reported to be important character-impact odorants in roasted peanut products, were synthesized by nucleophilic addition of a deuterated alkyl Grignard reagent to a chloroalkylpyrazine. The application of SIDA to quantify the above mentioned alkylpyrazines in four commercial peanut butters demonstrated the ease of use and the excellent precision and accuracy of the method.