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- Kinetic determination of L (-)malic acid in wines using sequential injection analysisPublication . Segundo, Marcela A.; Rangel, António O. S. S.In the present work a sequential injection system for the enzymatic determination of Image (−)malic acid in wines is described. The determination was based on the detection of NADH, formed by oxidation of Image -malate to oxaloacetate, catalysed by Image -malate dehydrogenase. A kinetic method was implemented by stopping the flow when a solution plug containing sample, NAD+ and enzyme reached the detector. The rate of reaction was measured by monitoring absorbance changes at 340 nm during a fixed period of time. A linear calibration curve (rate of reaction versus concentration) was obtained for concentrations of Image (−)malic acid between 0.01 and 0.15 g l−1. The determination rate was about 22 h−1 and samples were diluted 25 or 50 times before introduction to the system. Results obtained from 16 wine samples were comparable to those obtained by the reference method.
- Flow Analysis: A Critical View of Its Evolution and PerspectivesPublication . Segundo, Marcela A.; Rangel, António O. S. S.In the present article, flow techniques developed for automatic chemical analysis are reviewed. Different aspects of several flow methodologies are discussed, namely their configuration and operation mode. Special emphasis is given to flow injection analysis and sequential injection analysis. Recent developments in this area are also discussed, including bead injection, multicommutation and multisyringe flow analysis.
- Automatic flow systems based on sequential injection analysis for routine determinations in winesPublication . Segundo, Marcela A.; Lima, José L.F.C.; Rangel, António O.S.S.Sequential injection systems for wine analysis have been developed in recent years for determination of more than 20 species. Several aspects of these systems are reviewed in the present paper. Special focus is given to implementation of in-line sample treatment and adaptation of system operation through software control to enable determination in different types of wine. The strategies used to enhance selectivity and the capacity for multi-parameter determination are also addressed.