title: Optimal design of experiments applied to headspace solid phase microextraction for the quantification of vicinal diketones in beer through gas chromatography-mass spectrometric detection.
abstract: Vicinal diketones, namely diacetyl (DC) and pentanedione (PN), are compounds naturally found in beer that play a key role in the definition of its aroma. In lager beer, they are responsible for off-flavors (buttery flavor) and therefore their presence and quantification is of paramount importance to beer producers. Aiming at developing an accurate quantitative monitoring scheme to follow these off-flavor compounds during beer production and in the final product, the head space solid-phase microextraction (HS-SPME) analytical procedure was tuned through experiments planned in an optimal way and the final settings were fully validated. Optimal design of experiments (O-DOE) is a computational, statistically-oriented approach for designing experiences that are most informative according to a well-defined criterion. This methodology was applied for HS-SPME optimization, leading to the following optimal extraction conditions for the quantification of VDK: use a CAR/PDMS fiber, 5 ml of samples in 20 ml vial, 5 min of pre-incubation time followed by 25 min of extraction at 30 °C, with agitation. The validation of the final analytical methodology was performed using a matrix-matched calibration, in order to minimize matrix effects. The following key features were obtained: linearity (R(2) > 0.999, both for diacetyl and 2,3-pentanedione), high sensitivity (LOD of 0.92 μg L(-1) and 2.80 μg L(-1), and LOQ of 3.30 μg L(-1) and 10.01 μg L(-1), for diacetyl and 2,3-pentanedione, respectively), recoveries of approximately 100% and suitable precision (repeatability and reproducibility lower than 3% and 7.5%, respectively). The applicability of the methodology was fully confirmed through an independent analysis of several beer samples, with analyte concentrations ranging from 4 to 200 g L(-1).
authors: Centre of Exact Sciences and Engineering, University of Madeira, Campus da Penteada, 9000-390 Funchal, Portugal; Institute of Nanostructures, Nanomodelling and Nanofabrication (I3N), University of Aveiro, Aveiro, Portugal.
authors: João M
authors: JM
authors: Leça
authors: Centre of Exact Sciences and Engineering, University of Madeira, Campus da Penteada, 9000-390 Funchal, Portugal; CIEPQPF, Department of Chemical Engineering, University of Coimbra, Pólo II - Rua Sílvio Lima, 3030-790 Coimbra, Portugal. Electronic address: acpereira@uma.pt.
authors: Ana C
authors: AC
authors: Pereira
authors: Centre of Exact Sciences and Engineering, University of Madeira, Campus da Penteada, 9000-390 Funchal, Portugal.
authors: Ana C
authors: AC
authors: Vieira
authors: CIEPQPF, Department of Chemical Engineering, University of Coimbra, Pólo II - Rua Sílvio Lima, 3030-790 Coimbra, Portugal.
authors: Marco S
authors: MS
authors: Reis
authors: Centre of Exact Sciences and Engineering, University of Madeira, Campus da Penteada, 9000-390 Funchal, Portugal.
authors: José C
authors: JC
authors: Marques
mesh_terms: D001515:Beer / Q000032:analysis*; D003931:Diacetyl / Q000032:analysis*; D004867:Equipment Design; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D057230:Limit of Detection; D010422:Pentanones / Q000032:analysis*; D015203:Reproducibility of Results; D052617:Solid Phase Microextraction / Q000295:instrumentation / Q000379:methods*
chemical_list: D010422:Pentanones; D003931:Diacetyl; C013186:2,3-pentanedione
keywords: Headspace solid phase microextraction; Optimal design of experiments; Optimization; Vicinal diketones