This application brief introduces a method of using Agilent 8890/5977C GC/MSD and Agilent PAL3 (SPME) automatic sampler to detect four aldehydes (hexanal, furfural, phenethyl) that cause off flavors in beeriA quantitative analysis method for aldehydes and trans-2-nonenal. This method adopts fully automated, solvent-free extraction and fiber derivatization. Using the fiber derivatization method, aldehydes were derivatized using the derivatization reagent O - (2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA). Firstly, adsorb the derivatization reagent onto Agilent 65 µ m PDMS/DVB fibers. Next, insert the fibers into a 20 mL headspace sample bottle containing 2 mL of beer sample and stir at 60 ° C for 30 minutes. The extraction and derivatization processes are both automatically completed using a PAL3 automatic sampler. This method demonstrates excellent sensitivity, with a detection limit of 0.0009 µ g/L for hexanal and 0.52 µ g/L for furfuraliThe detection limit for aldehydes is 0.015 µ g/L, and the detection limit for trans-2-nonenal is 0.003 µ g/L. The quantification limits of these four compounds are 0.003, 1.72, 0.05, and 0.01 µ g/L, respectively. The content of these four aldehydes was successfully determined in four beer samples purchased from the supermarket. Three repeated injections were conducted on four types of beer samples, and the results showed that the four aldehydes had good reproducibility, RSD < 4.9%。