FLOW-INJECTION DETERMINATION OF SULFITE IN WINES AND FRUIT JUICES BY USING A BULK ACOUSTIC-WAVE IMPEDANCE SENSOR COUPLED TO A MEMBRANE SEPARATION TECHNIQUE

A flow injection analysis (FIA) method was developed for the rapid det ermination of sulfite in wines and fruit juices, The method is based o n an on-line membrane separation of the SO2 released from a stream of 0.5 M H2SO4 into a stream of 0.01 M H2O2-0.15 mM H2SO4, The conductanc e increase due to the oxidation of SO2 to H2SO4 is monitored by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration of sulfite present in the original sample, At a throughp ut of 78 samples h(-1), the method exhibited a linear frequency respon se up to 1.0 mM sulfite with a detection limit of 5.0 mu M, and the re lative standard deviation of the peak height (n = 6) ranged from 0.57 to 1.23%, Results obtained by the proposed method agreed well with tho se obtained by conventional iodimetry, The effects of several factors, including those affecting the detector performance and gas transfer p rocess, on the performance of the proposed FIA system were also examin ed.