Automatic flow procedure for the determination of glycerol in wine using enzymatic reaction and spectrophotometry |
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Authors: | Elizabeth Nunes Fernandes Mariele Nair de Campos Moura Jos Luis F Costa Lima Boaventura F Reis |
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Institution: | a Departamento de Química, Universidade Federal de São Carlos, Brazil;b Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Av. Centenário, 303, PO Box 96, Piracicaba, SP 13400-970, Brazil;c Departamento de Química-Física, Faculdade de Farmácia, Universidade do Porto, Oporto, Portugal |
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Abstract: | An automatic flow procedure for the determination of glycerol in wines by employing a flow system based on multicommutation and enzymatic reaction is described. Glycerol dehydrogenase was immobilized on aminopropyl glass beads and packed into a column that was coupled to the flow system. The NADH produced by the enzymatic reaction was monitored by spectrophotometry at 340 nm and its radiation absorption presented a relationship with glycerol concentration. The system manifold comprised a set of three-way solenoid valves controlled by a microcomputer, which was furnished with electronic interfaces and runs a software that was designed to carry out on-line sample dilution, reagent addition, and data acquisition. The procedure allows the determination of glycerol in wine samples without any prior pretreatment. The procedure presented as profitable features a linear response range between 2.0 and 10.0 g l−1 glycerol (R=0.998), a detection limit of 0.006 g l−1 glycerol, a relative standard deviation of 1.8% (n=14) for a typical wine sample presenting 5.3 g l−1 glycerol, a sampling throughput of 33 determinations per hour, and a NAD+ consumption of 0.8 mg per determination. The results were compared with those obtained using a reference method and no significant difference at 90% confidence level was observed. |
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Keywords: | Glycerol Wine On-line dilution Multicommutation Flow analysis Glycerol dehydrogenase Spectrophotometry |
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