Solid-Phase Microextraction Method Development for Headspace Analysis of Volatile Flavor Compounds

• Published in: Journal of agricultural and food chemistry Vol. 48; no. 6; pp. 2430 - 2437
• Main Authors: Roberts, D. D, Pollien, P, Milo, C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.2000
• Subjects: adsorption; Biological and medical sciences; chemistry; Chromatography, Gas; Chromatography, Gas - instrumentation; Chromatography, Gas - methods; Chromatography, High Pressure Liquid; Chromatography, High Pressure Liquid - instrumentation; Chromatography, High Pressure Liquid - methods; Coffee; coffee (beverage); Coffee - chemistry; Coffee, tea and other stimulative beverage industries; flavor compounds; Food industries; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; Gas Chromatography-Mass Spectrometry - methods; instrumentation; isotope dilution technique; methods; Microchemistry; Taste; volatile compounds; Volatile compound; Competition; Dimethylsiloxane polymer; Solid phase extraction; Organoleptic properties; Stimulative beverage; Chemical structure; HPLC chromatography; Isotope dilution; Benzene(divinyl) polymer; Lipophily; Coffee; Flavor; Organic acids; Analysis method; Storage; Linearity; Quality control; pH; Headspace; Acetic acid; Comparative study
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf991116l

Solid-phase microextraction (SPME) fibers were evaluated for their ability to adsorb volatile flavor compounds under various conditions with coffee and aqueous flavored solutions. Experiments comparing different fibers showed that poly(dimethylsiloxane)/divinylbenzene had the highest overall sensitivity. Carboxen/poly(dimethylsiloxane) was the most sensitive to small molecules and acids. As the concentrations of compounds increased, the quantitative linear range was exceeded as shown by competition effects with 2-isobutyl-3-methoxypyrazine at concentrations above 1 ppm. A method based on a short-time sampling of the headspace (1 min) was shown to better represent the equilibrium headspace concentration. Analysis of coffee brew with a 1-min headspace adsorption time was verified to be within the linear range for most compounds and thus appropriate for relative headspace quantification. Absolute quantification of volatiles, using isotope dilution assays (IDA), is not subject to biases caused by excess compound concentrations or complex matrices. The degradation of coffee aroma volatiles during storage was followed by relative headspace measurements and absolute quantifications. Both methods gave similar values for 3-methylbutanal, 4-ethylguaiacol, and 2,3-pentanedione. Acetic acid, however, gave higher values during storage upon relative headspace measurements due to concurrent pH decreases that were not seen with IDA. Keywords: Solid-phase microextraction; isotope dilution assay; linear range; coffee; competition; headspace