Instrumentation and Automated Photometric Titration Procedure for Total Acidity Determination in Red Wine Employing a Multicommuted Flow System

An automated procedure for photometric titration of red wine and associated instrumentation is described. The procedure was based on the flow-batch approach implemented employing multicommutation. The photometric detection was carried out using a homemade LED-based photometer. The mixing device, LED, and photodetector were attached to the titration chamber in order to form a compact and small-sized unit. The flow system comprised an automatic injector and three-way solenoid valves, which were controlled by a microcomputer through an electronic interface card. The software, written in Quick BASIC 4.5, was designed with abilities to accomplish all steps of the titration procedure including data acquisition and real-time processing to decide about the course of titration in the following step and so forth, until the titration endpoint was reached. The usefulness of the proposed titration system was demonstrated by analyzing red wine samples. When results were compared with those obtained using the AOAC reference method, no significant difference was observed at the [Formula: see text] confidence level. A relative standard deviation of ca [Formula: see text] ([Formula: see text]) was obtained when processing a typical red wine sample containing 7.3 [Formula: see text] total acidity expressed as tartaric acid

HS-SPME-GC-MS detection of volatile compounds in Myrciaria jabuticaba Fruit

This study was performed to investigate the volatile compounds for the characteristic aroma in jabuticaba fruit distributed in southern and central regions of Brazil. The present work combines headspace solid phase microextraction (HS-SPME) and high resolution gas chromatography-mass spectrometry (GC-MS) techniques to identify and quantify the volatile compounds. The influence of different SPME fibers (CAR/PDMS and DVB/CAR/PDMS) in extraction of volatile compounds was evaluated. The effects of extraction temperature and salt concentration (NaCl) in the extraction medium were studied using the response surface methodology in order to achieve the highest extraction efficiency. The better extraction of volatile compounds was achieved by using a CAR/PDMS fiber and the optimum adsorption conditions were at 42 °C for 30 min and 5% NaCl concentration. A total of 71 compounds were identified, among these, 57% were terpenes which was the most representative class of compounds, followed by esters (19%), aldehydes (10%), alcohols (5.5%) and aromatics compounds (4.4%) and other organic compounds 2.8%. Limonene and ethyl acetate were the volatile compounds that showed highest relative concentration and these could contribute to the characteristic aroma of the jabuticaba fruit along with other compounds such as b-pinene, δ-cadinene, linalool, b-guaiene, and α-caryophyllene

Methodologies for the determination of triclosan and chlorophenols by high performance liquid chromatography (HPLC) and sequential injection chromatography (SIC) using packed and monolithic columns

Foram desenvolvidas metodologias de cromatografia a líquido de fase reversa baseadas em injeção sequencial (SIC) e em cromatografia a líquido de alta eficiência (HPLC) para determinação de triclosan em amostras de produtos de higiene pessoal e em estudos de adsorção em argilominerais naturais e modificados, visando determinar parâmetros de adsorção de triclosan frente a alguns de seus metabólitos. A determinação de triclosan em enxaguadores bucais foi realizada por SIC com eluição isocrática usando fase móvel constituída por acetonitrila: tampão fosfato de trietilamina 70 mM pH 3,5 na proporção 70:30 (v v-1), obtendo-se limites de detecção e de quantificação de 0,22 e 0,72 mg L-1, respectivamente. Taxas de recuperação entre 96 e 98% foram obtidas da aplicação a amostras reais, sendo que os resultados obtidos pelo método proposto não apresentaram evidências de diferenças estatisticamente significativas em comparação a uma metodologia de referência baseada em HPLC com coluna empacotada. A separação de triclosan (TCS), 2-clorofenol (2-CP), 2,4-diclorofenol (2,4-DCP), 2,4,6-triclorofenol (2,4,6-TCP), 2,3,4-triclorofenol (2,3,4-TCP) e metiltriclosan (MTCS) foi estudada por SIC, obtendo-se a separação de TCS, 2-CP, 2,4-DCP e 2,4,6-TCP com duas etapas de eluição isocrática, a primeira delas com fase móvel 60:40 (v v-1) metanol: tampão acetato de amônio 20 mM (pH 5,5) seguida de eluição com fase móvel 70:30 (v v-1) metanol : tampão acetato de amônio 20 mM (pH 5,5). Nesse caso, os isômeros 2,4,6-TCP e 2,3,4-TCP coeluem. Metiltriclosan, o menos polar desses compostos, pode ser separado de TCS com etapas subseqüentes de eluição. Os métodos foram aplicados para estudar a adsorção de triclosan e seus metabólitos 2,4-DCP, 2,4,6-TCP e metiltriclosan em montmorilonita homoiônica (K+) e modificada com sal de hexadeciltrimetilamônio (HDTMA), observando-se forte adsorção de triclosan e metiltriclosan em comparação a 2-CP, 2,4-DCP e 2,4,6-TCP. A incorporação de HDTMA no argilomineral causou significativo aumento da capacidade de adsorção desses metabólitos, determinada a partir do ajuste dos dados experimentais à equação linearizada de Langmuir, observando-se que a ordem de adsorção é 2,4,6-TCP > 2,4-DCP > 2-CPReversed-phase liquid chromatography methodologies based on sequential injection (SIC) and high performance liquid chromatography (HPLC) have been developed for determination of triclosan in samples of personal hygiene products and in studies of adsorption on natural and modified clay minerals aiming to determine kinetic and thermodynamic parameters of adsorption of triclosan in comparison with some of its metabolites. The determination of triclosan in oral rinses with SIC was performed by isocratic elution using a mobile phase of acetonitrile : 70 mM triethylamine phosphate buffer pH 3.5 at the ratio 70:30 (v v-1), obtaining limits of detection and quantification of 0.22 and 0.72 mg L-1, respectively. Recovery rates between 96 and 98 % were obtained from the application to commercial samples, and the results obtained by the proposed method showed no evidence of statistically significant differences compared to the reference methodology based on HPLC with packed column. The separation of triclosan (TCS), 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4 trichlorophenol (2,3,4-TCP) and methyltriclosan (MTCS) was studied by SIC, resulting in the separation of TCS, 2-CP, 2,4-DCP and 2,4,6-TCP with two isocratic elution steps, the first of them with a mobile phase 60:40 (v v-1) methanol: 20 mM ammonium acetate buffer (pH 5.5) followed by elution with 70:30 (v v-1) mobile phase of methanol : 20 mM ammonium acetate buffer (pH 5.5). In this case, the isomers 2,4,6-TCP and 2,3,4-TCP coeluted. Methyltriclosan, the less polar of these compounds, can be separated from TCS with subsequent elution steps. The methods were applied to study the adsorption of triclosan and its metabolites 2-CP, 2,4-DCP, 2,4,6-TCP and methyltriclosan on homoionic montmorillonite (K+) as well as in hexadecyltrimethylammonium salt (HDTMA) modified montmorillonite, noticing a stronger adsorption of triclosan and methyltriclosan compared with 2-CP, 2,4-DCP and 2,4,6-TCP. Incorporation of HDTMA in the clay mineral caused significant increase in adsorption capacity of these metabolites. This capacity was determined by fitting the experimental data to the linearized Langmuir equation. The adsorption order was 2,4,6-TCP > 2,4-DCP > 2-CP

HS-SPME-GC-MS detection of volatile compounds in Myrciaria jabuticaba Fruit

This study was performed to investigate the volatile compounds for the characteristic aroma in jabuticaba fruit distributed in southern and central regions of Brazil. The present work combines headspace solid phase microextraction (HS-SPME) and high resolution gas chromatography-mass spectrometry (GC-MS) techniques to identify and quantify the volatile compounds. The influence of different SPME fibers (CAR/PDMS and DVB/CAR/PDMS) in extraction of volatile compounds was evaluated. The effects of extraction temperature and salt concentration (NaCl) in the extraction medium were studied using the response surface methodology in order to achieve the highest extraction efficiency. The better extraction of volatile compounds was achieved by using a CAR/PDMS fiber and the optimum adsorption conditions were at 42 °C for 30 min and 5% NaCl concentration. A total of 71 compounds were identified, among these, 57% were terpenes which was the most representative class of compounds, followed by esters (19%), aldehydes (10%), alcohols (5.5%) and aromatics compounds (4.4%) and other organic compounds 2.8%. Limonene and ethyl acetate were the volatile compounds that showed highest relative concentration and these could contribute to the characteristic aroma of the jabuticaba fruit along with other compounds such as b-pinene, δ-cadinene, linalool, b-guaiene, and α-caryophyllene