Flow-injection analysis based on a membrane separation module and a bulk acoustic wave impedance sensor – determination of the volatile acidity of fermentation products |
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Authors: | Xiaoli Su Lihua Nie and S Yao |
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Institution: | (1) College of Chemistry & Chemical Engineering, Hunan University, Changsha, 410082, P.R. China, CN |
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Abstract: | A novel flow-injection analysis (FIA) system has been developed for the rapid determination of the volatile acidity of some
fermentation products like vinegars and juices. The proposed method is based on the diffusion of volatile acids, mainly acetic
acid, across a PTFE gas-permeable membrane from an acid stream into an alkaline stream, and the acids trapped in the acceptor
solution are determined online by a bulk acoustic wave impedance sensor based on changes in the conductivity of the solution.
It exhibited a linear frequency response up to 10 mmol · L–1 acetic acid with a detection limit of 50 μmol · L–1, and the precision was better than 1% (RSD) at a through-put of 72 h–1. The effects of operating voltage for the detector, cell constant of the electrode, composition of acceptor stream, flow
rates and temperature on the FIA performance were also investigated.
Received: 2 June 1997 / Revised: 7 July 1997 / Accepted: 12 July 1997 |
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