title: Analysis of free fatty acids in beer: comparison of solid-phase extraction, solid-phase microextraction, and stir bar sorptive extraction.
abstract: Solid-phase extraction (SPE), solid-phase microextraction (SPME) using carbowax/divinylbenzen fiber, and stir bar sorptive extraction (SBSE) followed by solvent back extraction have been used for the extraction of free fatty acids (caproic, caprylic, pelargonic, capric, lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acids) from beer. Subsequent gas chromatographic analyses with flame ionization detection were used for the determination of these compounds. Medium-chain fatty acids (caproic-lauric acid) were determined as free acids, and long-chain fatty acids (myristic-linolenic acids) were determined as methyl esters after methylation by BF(3)-methanol 14%. Linearity, recovery, and repeatability of all methods have been determined and compared with the SPE method used as a reference (SPME method was used only for medium-chain fatty acid determination). All three procedures provide similar working parameters characterized by high repeatability (2.3-16.3%) and good linearity (correlation coefficient ranging from 0.9919 to 0.9999). Results of beer analyses obtained by using these three methods were highly correlated. Although all methods provide compatible alternatives, for medium-chain fatty acid analysis SPME may be a more appropriate technique due to its operational simplicity, repeatability, and low cost.
authors.affiliation: Research Institute of Brewing and Malting, Brewing Institute-Prague, Prague, Czech Republic. horak@beerresearch.cz
authors.forename: Tomás
authors.initials: T
authors.lastname: Horák
authors.forename: Jirí
authors.initials: J
authors.lastname: Culík
authors.forename: Pavel
authors.initials: P
authors.lastname: Cejka
authors.forename: Marie
authors.initials: M
authors.lastname: Jurková
authors.forename: Vladimír
authors.initials: V
authors.lastname: Kellner
authors.forename: Josef
authors.initials: J
authors.lastname: Dvorák
authors.forename: Danusa
authors.initials: D
authors.lastname: Hasková
mesh_terms: D001515:Beer / Q000032:analysis*; D002849:Chromatography, Gas; D005227:Fatty Acids / Q000032:analysis*; D052616:Solid Phase Extraction / Q000295:instrumentation / Q000379:methods*; D052617:Solid Phase Microextraction / Q000295:instrumentation / Q000379:methods
chemical_list: D005227:Fatty Acids