Sulfites Monier-Williams method

In one study, a modified Monier-Williams method has been utilized as a preparative procedure to obtain both the free and bound sulfite fractions. The two fractions were analyzed by HPLC with indirect photometric detection using a 250 X 4.6-mm LC-SAX column eluted with potassium hydrogen phtalate (0.15 g/L, pH 5.7) and detected at 280 nm. Levels of 5-10 ppm of S02 in foods, corresponding to 30 - 60 ng injected, were reliably detected by this method. The results confirmed that the chromatographic method, unlike the Monier-Williams method, is able to avoid the potential interference of volatile substances derived from matrices or utilized chemicals (36). The HPLC conditions are summarized in Table 3. 

Sulfites Foods Cptimized Monier-Williams method... 

Roughly 10 years ago, an ion-pair HPLC was introduced for the determination of sulfites in foods (32). The method combined the chemical approach of the Monier-Williams technique for liberating the sulfite from the matrix with ion chromatography. The ion chromatographic procedure... 

Acid-induced decomposition is the basis of many methods of determining the presence of sulfite in foodstuffs. One of the best known methods is the Monier-Williams procedure, in which the sample is refluxed with HC1, and the S02 driven off is estimated iodometrically. 

In addition to the iodometiic determination, direct precipitation as barium sulfate before and after treatment with bromine was suggested for both quantitative and qualitative test for sulfur dioxide in wine (see Monier-Williams, 1927). Precipitation of SO2 after oxidation with H2O1 as the benzidine sulfate was proposed by Rothen-fusser (1929) reduction of the molybdenum in phosphomolybdic acid by the sulfite ion present in an aqueous solution of the food was proposed by Sasaki (1928) as a colorimetric method formation of a blue color from a solution of 1% methylene blue and 5% iodine in potassium iodide was proposed by Svershkov (1939). Mathers (1949) proposed a turbidimetric method based on the distillation of wine into a dilute solution of lead acetate to form a colloidal suspension of lead sulfite whose spectral transmittance in the range of 400 to 700 mn could be used as a measure of sulfur dioxide. This is similar to turbidimetric methods based on turbidity produced by adding BaCfii to a... 

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