This paper proposes a new analytical procedure based on the headspace solid-phase microextraction (HS-SPME) technique and gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of 16 phenols extracted from leather samples. The optimized conditions for the HS-SPME were obtained through two experimental designs - a two-level fractional factorial design followed by a central composite design - using the commercial SPME fiber polyacrylate 85 μm (PA). The best extraction conditions were as follows: 200 μL of derivatizing agent (acetic anhydride), 20 mL of saturated aqueous NaCl solution and extraction time and temperature of 50 min and 75°C, respectively. All optimized conditions were obtained with fixed leather sample mass (250 mg), vial volume (40 mL) and phosphate buffer pH (12) and concentration (50 mmol/L). Detection limits ranging from 0.03 to 0.20 ng/g, and relative standard deviation (RSD) lower than 10.23% (n=6) for a concentration of 800 ng/g (chlorophenols) and 1325 ng/g (2-phenylphenol) in the splitless mode were obtained. The recovery was studied at three concentration levels by adding different amounts of phenols to the leather sample and excellent recoveries ranging from 90.0 to 107.2% were obtained. The validated method was shown to be suitable for the quantification of phenols in leather samples, as it is simple, relatively fast and sensitive.

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Neste estudo é proposto um novo procedimento analítico para a determinação de fenóis em amostras de couro utilizando a técnica de microextração em fase sólida refrigerada internamente (CF-SPME) com derivatização direta na fibra e cromatografia gasosa acoplada a espectrometria de massas com monitoramento de íons selecionados (GC-SIM-MS). As condições experimentais para a extração e derivatização foram otimizadas utilizando procedimentos quimiométricos, sendo tempo de extração e temperatura da amostra de 5 min e 170 ºC, temperatura do recobrimento da fibra de 20 ºC, e exposição da fibra ao headspace de 70 µL do agente derivatizante bis(trimetilsilil) trifluor-acetamida por 23 min. Limites de detecção variaram entre 1,03 e 2,68 µg g-1 e o desvio padrão relativo (RSD) foi menor que 15% (n = 5). Estudos de recuperações em três níveis de concentração variaram entre 64,5 e 92,3%. This study proposes a new analytical procedure based on an internally cooled solid phase microextraction technique (CF-SPME) combined with on-fiber derivatization and gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of phenols extracted directly from leather samples. The extraction and derivatization conditions were optimized using experimental designs, such as: extraction time and sample temperature of 5 min and 170 ºC, fiber recoat temperature of 20 ºC, and exposing the fiber to the headspace of 70 µL of bis(trimethylsylyl)trifluoro-acetamide derivatizing agent for 23 min. Detection limits ranging from 1.03 to 2.68 µg g-1 and relative standard deviation (RSD) lower than 15% (n = 5) were obtained. The recovery was studied at three concentration levels and excellent recoveries ranging from 64.5 to 92.3% were obtained.

Two different yogurts, control and probiotic with Bifidobacterium BB-12 were produced and analyzed for their contents of total solids, proteins, pH, counts of probiotic bacteria, and volatile composition during refrigerated storage for 28 days. The response surface methodology (RSM) was used to optimize the extraction of volatile compounds from the probiotic yogurt containing through HS-SPME combined with gas chromatography–mass spectrometry (GC–MS). Post-acidification and decrease in protein content were noted in both yogurts during storage. The results showed that the extraction temperature and the addition of salt were statistically the most influential factors for the extraction of higher amounts of volatile compounds. The volatile compounds detected in the probiotic yogurt were 2-butanone, 2,3-butanedione, 2,3-pentanodione, acetone and hexanoic acid. During the 28 days of storage, the only differences noted were between the amounts of 2,3-butanedione, 2,3-pentanodione and hexanoic acid.

An analytical procedure based on the solid-phase microextraction technique (SPME) combined with gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of organochlorine pesticides (OCPs) extracted directly from leather samples is proposed. The extraction conditions for the headspace SPME (HS-SPME) procedure were optimized using experimental designs. The fibers and the ionic strength were optimized by the univariate procedure, while a Doehlert matrix was used to optimize the extraction time and temperature. The best extraction conditions were obtained using a PDMS/DVB fiber with extraction time and temperature of 35 min and 80 ºC, respectively. No salt addition was necessary. Detection limits ranging from 3.3 to 11 ng g-1 and relative standard deviations (RSD, n = 5) lower than 14.2% were obtained. The recovery was studied at three concentration levels by adding different amounts of organochlorine pesticides to the leather samples (600, 900 and 1500 ng g-1) and excellent recoveries ranging from 93.7 to 107.3% were obtained.