Determination of Sulfite in Food by Flow Injection Analysis

Abstract

A method is described for the determination of sulfite levels in food products by flow injection analysis (FIA). The method is based on the decolorization of malachite green by S02, which is isolated from the flowing sample stream by means of a gas diffusion cell. The FIA method has a detection limit in food sample extracts of 0.1 ppm S02 (3 times peak height of blank), which corresponds to 1-10 ppm S02 in a food product, depending on the extraction procedure used. At the 5 ppm SO2 level in a food extract, the precision of replicate injections is ± 1-2%. The method was tested on a variety of both sulfite-treaied and untreated food products and the results compared favorably with those obtained by the Monier-Williams, colorimetric (pararosaniline), and enzymatic (sulfite oxidase) methods. The average differences from the FIA results were 19, 11, and 12%, respectively, for those samples (n = 12) above SO ppm S02. At lower levels the results were somewhat more erratic due to inaccuracies of the various methods at low concentrations.

A gas-diffusion microfluidic paper-based analytical device (μPAD) coupled with portable surface-enhanced Raman scattering (SERS): facile determination of sulphite in wines

“…The potential interference of water-soluble molecules with the determination of sulphite in wines was eliminated to a great extent in flow analysis systems by introducing a gas-diffusion separation step. 11,32,33 According to previous studies, the coexisting volatile components including ethanol, isopropyl alcohol, ethyl acetate, nerolidol, and acetaldehyde would most likely interfere with the determination of SO 2 . [34][35][36] Coincidently, through the comparison of the reported Raman spectra of these compounds, no obvious SERS signal was observed at the 620 cm −1 shift.…”

Non-Saccharomyces Yeast Strains, Aromatic Compounds and Sensory Analysis of Italy and Negra Criolla Pisco from the Moquegua Region of Peru

“…A colorimetric assay based on malachite green with some modifications was used to measure sulphite production [21]. The isolated and identified NSYS cell loops were inoculated in the carbohydrate solution (5 mL) and I or NC grape must (5 mL) by filtration and incubated for 48 h under anaerobiosis.…”

Determination of sulfite using a sulfite oxidase enzyme electrode

“…Among the analytical methods used for sulfite analysis are titration by the Monier-Williams method (if), gas chromatography (8), liquid chromatography (9), mercuric sulfide/ mercurous chloride electrodes (10,11), ion chromatography (12)(13)(14), enzymatic UV (15,16) flow injection analysis (17), color test strip (18), and spectrophotometry (19). Sulfite analysis is complicated by the instability of the ion in the presence of oxygen (12), loss as sulfur dioxide (gas) which exists in equilibrium with sulfite and bisulfite anion (5), and variability in the amount of "bound" sulfite released upon extraction.…”

“…It is commonly accepted that the electrooxidation of formic acid on platinum can occur via "dual pathways" involving both weakly and strongly adsorbed intermediates (16). The identity of the latter species has been the subject of much debate; although the presence of adsorbed CO is indicated from surface infrared spectroscopy (3), electrochemical (16) and coupled mass spectrometric ("DEMS") measurements suggest that the strongly adsorbed intermediate is COH (17,18). While the present results certainly do not eliminate the latter possibility, they do nonetheless indicate that the initially adsorbed CO is sufficiently reactive to have potential as a possible catalytically active intermediate under voltammetric conditions (15).…”