Optimization of the HS-SPME-GC-IT/MS method using a central composite design for volatile carbonyl compounds determination in beers

Volatile carbonyl compounds associated with staling beer aroma includes alkanals, alkenals, alkadienals, dicarbonyl compounds, Strecker aldehydes, ketones and furans. The HS-SPME was performed using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The procedures were optimized for HS-SPME pre-incubation temperature and time, extraction temperature and time, and PFBHA addition. A central composite design was used in the optimization of extraction conditions and PFBHA addition. The volatile compounds showed optimal extraction incubating 5 ml of beer with 700 mg l−1 of PFBHA for 7 min and extracted for more 20 min at 45 °C. The method was validated with regard to the linearity, repeatability, inter and intra-day precision and accuracy. The method achieved detection limits ranging from 0.003 to 0.510 µg l−1, except for furans (1.54-3.44 µg l−1). The quantification limits varied from 0.010 to 1.55 µg l−1, except for 2-furfural (4.68 µg l−1), 5-methyl-2-furfural (5.82 µg l−1) and 5-hyfroxymethylfurfural (10.4 µg l−1). Repeatability values of all compounds were lower than 17%. The method accuracy was satisfactory with recoveries ranging from 88% to 114%. The validated method showed to be suitable for a fast and reliable determination of main carbonyl compounds in beers.