Journal articles: 'Monier-Williams method'

1

Moylan, John G., F. William Bowes, and Walter J. Pappin. "Evaluation of Monier-Williams and Committee Methods for Bisulfite Determination as Used by the Potato Processing Industry." Journal of AOAC INTERNATIONAL 69, no. 1 (January 1, 1986): 11–14. http://dx.doi.org/10.1093/jaoac/69.1.11.

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Abstract The Monier-Williams and the iodometric Committee methods were evaluated for the determination of bisulfite in potato products. Both methods showed critical problems in accuracy and precision at concentrations below 60 ppm. Sensitivity levels of 25 ppm are possible with the Monier-Williams method. However, accuracy problems reflected by the coefficients of variation (Monier-Williams, 47.4%; Committee, 78.2%) as well as variability in recoveries and blank values for both methods produce qualitative rather than quantitative analytical data at low SO2 concentrations

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WILLIAMS, DAVID J., STEVEN L. SLATTERY, and STEPHEN M. NOTTINGHAM. "A Comparison of Selected Methods for Determining Sulfite in Prawns." Journal of Food Protection 53, no. 10 (October 1, 1990): 875–77. http://dx.doi.org/10.4315/0362-028x-53.10.875.

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As the standard technique for sulfite analysis, the Monier-Williams distillation, is time consuming and relatively insensitive, many alternative methods have been developed. Three of these methods were tested for their suitability for the routine determination of residual sulfite in prawns: i) a rapid steam distillation; ii) high performance liquid chromatography (HPLC), and iii) an enzyme-based procedure. Testing of the three selected methods involved analyses of standard sulfite solutions, prawns of known sulfite levels and prawns of unknown sulfite levels and comparison of results with those determined by the Monier-Williams procedure. Statistical analysis showed that the sulfite levels determined on standard solutions by rapid distillation were in close agreement with those obtained by the Monier-Williams distillation. However, a correction factor had to be introduced when analyzing prawns by the rapid distillation method to obtain comparable results with those produced by the Monier-Williams distillation. The same statistical analysis performed on levels determined by HPLC and the Monier-Williams distillation gave close agreement for both standard solutions and prawns. The enzyme test, after promising results for the standard solutions, proved to be unsatisfactory for analysis of sulfite in prawns.

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SIMPSON, MARIAN V., W. STEVEN OTWELL, MAURICE R. MARSHALL, and JOHN A. CORNELL. "Analysis of Sulfites in Shrimp Using Rapid Distillation Followed by Redox Titration1." Journal of Food Protection 51, no. 2 (February 1, 1988): 137–38. http://dx.doi.org/10.4315/0362-028x-51.2.137.

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The use of rapid steam distillation followed by redox iodine titration provides a rapid and accurate determination of total sufite residual in shrimp. Values obtained for sulfite-treated shrimp using the rapid distillation method gave comparable results to those of the officially recognized Monier-Williams method. Values for the rapid distillation method ranged from 6 to 212 ppm while those of the Monier-Williams procedure ranged from 6 to 241 ppm for untreated and treated shrimps, respectively. Statistical analysis using two-sample Student's t-test indicated that there were no significant differences (p>0.05) for residual levels below 100 ppm but the values obtained by the rapid distillation method and the Monier-Williams procedure were significantly different (p<0.05) at concentrations near and above 100 ppm.

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Devries, Jonathan W., Hoon Ge, Frank J. Ebert, Joel M. Magnuson, and Mark K. Ogawa. "Analysis for Total Sulfite in Foods By Using Rapid Distillation Followed By Redox Titration." Journal of AOAC INTERNATIONAL 69, no. 5 (September 1, 1986): 827–30. http://dx.doi.org/10.1093/jaoac/69.5.827.

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Abstract A rapid and accurate analysis for total sulfite as sulfur dioxide has been developed for foods and food products. The method, which combines a selective distillation cleanup procedure with the selective redox titration of sulfite ion by iodine, has been applied to a variety of foods and food products over a period of time with no significant interference encountered in any matrixes other than garlic and leeks. For the foods analyzed, the method typically shows a detection limit of 10 ppm, a relative standard deviation of 7.5% (compared with 10.4% for similar matrixes by the Monier-Williams method), and recoveries of 97.9 ± 6.4%. Comparison of results for this method with those obtained using the Monier-Williams method showed a mean value for the distillation/ titration method of 241 ppm compared with 242 ppm for the Monier- Williams method. A correlation of 0.991 and odds of a difference between methods of 10.7% (Student's paired t-test(1- α) × 100) were obtained for those matrixes where no interferences were encountered with either method.

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Kim,, Hie-Joon, Karen R. Conca, and Michelle J. Richardson. "Determination of Sulfur Dioxide in Grapes: Comparison of the Monier-Williams Method and Two Ion Exclusion Chromatographic Methods." Journal of AOAC INTERNATIONAL 73, no. 6 (November 1, 1990): 983–89. http://dx.doi.org/10.1093/jaoac/73.6.983.

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Abstract Results for determination of sulfur dioxide In grapes were compared by 3 methods: the modified Monier-Wllllams method, acid dlstlllatlon/lon exclusion chromatography with electrochemical detection (AD/IEC-EC), and alkali extraction/ ion exclusion chromatography with electrochemical detection (AE/IEC-EC). An unusual positive response was observed during the later stage of the Monier-Wllllams distillation of both control grapes and sulfited grapes. Development of volatile acidic compounds in parallel with this Monier- Wllllams response and darkening of sample was also observed by collection In an alkali trap and analysis using anion exclusion chromatography and photodlode array detection. No parallel Increase In sulfite was observed by the more selective AD/IEC-EC method, which clearly demonstrated that the response observed during the later stage of the Monier-Wllllams method Is a false positive, probably due to caramellzatlon reaction products. Monier-Williams results for grapes containing ca 10 ppm sulfite were In reasonably good agreement with those by either the AD/IEC-EC or AE/ IEC-EC methods, presumably because the false positive response In the Monier-Wllllams analysis compensated for the somewhat Incomplete recovery of sulfite. The AE/IECEC method Is recommended because it is rapid, sensitive, straightforward, and free from interference. Accurate results by Monier-Wllllams analysis could be obtained by limiting distillation to 60 min and correcting for recovery.

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Hillery, Barbara R., Edgar R. Elkins, Charles R. Warner, Dan Daniels, and Thomas Fazio. "Optimized Monier-Williams Method for Determination of Sulfites in Foods: Collaborative Study." Journal of AOAC INTERNATIONAL 72, no. 3 (May 1, 1989): 470–75. http://dx.doi.org/10.1093/jaoac/72.3.470.

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Abstract A collaborative study was conducted of the Food and Drug Administration (FDA)-optimized Monier-Williams method for determining sulfites in foods. Twenty-one industry and government laboratories participated in the study, which was jointly sponsored by the National Food Processors Association and FDA. Familiarization samples were shipped to each collaborator. Collaborators were permitted to proceed to the main study only after they demonstrated ability to perform the method to ensure that the study tested the performance of the method itself and not that of the individual laboratories. The study design involved 3 food matrixes (hominy, fruit juice, and protein [seafood]). Each matrix was prepared at 3 sulfite levels—the regulatory level, half the regulatory level, twice the regulatory level— and as a blank. All test samples were analyzed as blind duplicates, which gave each collaborator a total of 24 test portions. Collaborative recoveries gave a reproducibility (among-laboratories) coefficient of variation that ranged from 15.5 to 26.6% for sulfite determined as S02 by weight in the 3 foods at the 10 ppm level. The optimized Monier-Williams method has been approved interim official first action to replace the AOAC modified Monier-Williams method, 20.123-20.125.

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Montes, C., J. H. Vélez, G. Ramírez, M. Isaacs, R. Arce, and M. J. Aguirre. "Critical Comparison between Modified Monier-Williams and Electrochemical Methods to Determine Sulfite in Aqueous Solutions." Scientific World Journal 2012 (2012): 1–6. http://dx.doi.org/10.1100/2012/168148.

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In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.

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Kim, Hie-Joon. "Comparison of the Ion Exclusion Chromatographic Method with the Monier-Williams Method for Determination of Total Sulfite in Foods." Journal of AOAC INTERNATIONAL 72, no. 2 (March 1, 1989): 266–72. http://dx.doi.org/10.1093/jaoac/72.2.266.

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Abstract Experimental data comparing the alkali extraction/ion exclusion chromatographic method with the Monier-Williams method for determination of total sulfite are presented in (a) enzymatic and nonenzymatic browning systems, (b) vegetables containing naturally occurring sulfite, and (c) a carbohydrate-type food additive, erythorbic acid. Excellent agreement, with a linear correlation coefficient of 0.99, was observed in fresh potato samples homogenized with sulfite and allowed to react for different time intervals (enzymatic browning system). A good overall correlation was observed in dehydrated, sulfited apple samples heated for different times (nonenzymatic browning system); however, as heating time increased, higher results were obtained by the Monier-Williams method than by the alkali extraction/ion exclusion chromatographic method. The results of determining sulfite in the alkali trapping solution following acid distillation or acid treatment without heat suggested that this deviation was due to a fraction of sulfite bound to the browning reaction products in such a way that it was released by acid distillation but not by alkali extraction or acid treatment without heat. Similar behavior was demonstrated in cabbage with naturally occurring sulfite, which was released by acid distillation but not by alkali extraction or acid treatment without heat. The ion exclusion chromatographic method could overcome interference by the volatile caramelization reaction products in the Monier-Williams determination of erythorbic acid.

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Warner, Charles R., Daniel H. Daniels, Frank L. Joe, and Thomas Fazio. "Reevaluation of Monier-Williams Method for Determining Sulfite in Food." Journal of AOAC INTERNATIONAL 69, no. 1 (January 1, 1986): 3–5. http://dx.doi.org/10.1093/jaoac/69.1.3.

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Abstract The Monier-Williams distillation procedure has a long history of successful use for determining sulfite in fruit products and wine; however, a systematic evaluation of its accuracy and precision with other food matrices has not been undertaken. We found that the Monier-Williams distillation yielded >90% recovery of sulfite added to foods such as table grapes, hominy, dried mangoes, and lemon juice. Less than 85% recovery was obtained with broccoli, soda crackers, cheese-peanut butter crackers, mushrooms, and potato chips. These results may, in fact, accurately reflect the residual levels of sulfite if a portion of the sulfite undergoes irreversible reaction with some food components. Analysis of commercial food products gave sulfite levels ranging from 1400 ppm in dried apple slices to 25 ppm in cream sherry

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Lafeuille, Jean-Louis, Stephane Lefevre, and Djamila Achouri. "Determination of Added Sulfites in Dried Garlic with a Modified Version of the Optimized Monier-Williams Method." Journal of AOAC INTERNATIONAL 90, no. 4 (July 1, 2007): 1090–97. http://dx.doi.org/10.1093/jaoac/90.4.1090.

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Abstract The optimized Monier-Williams method is slightly modified so that it could be applied for determining sulfite content in dried garlic. Dried garlic sample is directly acidified in a reactor at a pH below 3. At this pH level, the alliinase enzyme activity is irreversibly blocked, and the sulfur-containing amino acids such as alliin (the most abundant) present in dried garlic cannot be transformed into corresponding thiosulfinates such as allicin, which is absent in dried garlic. This prevents allicin from reacting with added sulfites and being probably converted to S-allyl thiosulfate, which is not volatile and has no taste. It is found that at a pH below 2.4 and at boiling water temperature, alliin produces sulfur dioxide in adequate quantity to explain the false-positive results when utilizing the optimized Monier-Williams method with allicin suppression for unsulfited dried garlic samples. Finally, when garlic samples are stabilized in a phosphoric acid buffer at a final pH around 2.4, no sulfite is produced during the Monier-Williams distillation, which is further proof there are no naturally occurring sulfites in unsulfited dried garlic under these mild conditions.

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11

Anderson, Courtney, Charles R. Warner, Daniel H. Daniels, and Kathlene L. Padgett. "Ion Chromatographic Determination of Sulfites in Foods." Journal of AOAC INTERNATIONAL 69, no. 1 (January 1, 1986): 14–19. http://dx.doi.org/10.1093/jaoac/69.1.14.

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Abstract Ion chromatography (IC) is shown to be a promising technique for the determination of sulfites (SO2, SO⅔) in foods. Results of a 10 min flash distillation and 10 min IC determination compare favorably with the results from the conventional Monier-Williams method for total sulfite in a variety of food matrices. The IC technique also provides a wealth of additional information, such as (1) sulfite and sulfate (oxidized sulfite) content of the spiking or treatment solution, (2) residual sulfite applied to the food after oxidation losses in the treatment process, (3) free sulfite in foods, and (4) total sulfite in foods. As a further check on the Monier-Williams method, the sulfate content of the trapping solution can be determined by IC. Because the IC technique traps the liberated SO2 in a non-oxidizing rather than an oxidizing medium, it is considered free from interfering sulfides and organic sulfur-containing groups which can give false positives in the Monier-Williams method. IC thus offers a high speed, more sensitive, and cost-effective alternative to conventional techniques for the determination of sulfite in foods.

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12

Coker, Lowell E. "Uses and Analysis of Sulfites in the Corn Wet Milling Industry." Journal of AOAC INTERNATIONAL 69, no. 1 (January 1, 1986): 8–10. http://dx.doi.org/10.1093/jaoac/69.1.8.

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Abstract This paper reviews the purpose and principal uses of sulfiting agents in corn wet milling, together with the residual levels of sulfiting agents in finished products. Comparative results of the Monier-Williams method, an iodometric method, and a pararosaniline method for sulfur dioxide are discussed.

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Addala, Ramya, Leonard Fong, Mihir Vasavada, and Siva Subramanian. "Influence of Distillation Temperature in the Determination of Added Sulfites in Dehydrated Garlic Powders Using the Modified Optimized Monier-Williams Method." Journal of AOAC INTERNATIONAL 99, no. 3 (May 1, 2016): 721–24. http://dx.doi.org/10.5740/jaoacint.15-0313.

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Abstract Influence of distillation temperature on the determination of added sulfites in dehydrated garlic originating from China and California using the modified optimized Monier-Williams method was evaluated. In the study, the temperature of the distillation was monitored and maintained from 90° to 95°C instead of boiling temperature (>95°C). Samples from 38 unsulfited dehydrated garlic powders were analyzed at the 90° to 95°C temperature and at boiling temperature (>95°C) at 94 m above sea level. At the boiling distillation temperature, 25 of the 38 unsulfited garlic samples had a positive result for sulfite content ranging from 10.2 to 14.1 ppm using the modified optimized Monier-Williams procedure. Maintaining distillation temperature between 90° and 95°C eliminated false-positive results for added sulfite and had an average spiked sulfite recovery of 95.6% with a coefficient of variation of 3.79%. Lowering of the distillation temperature decreases the possible acid hydrolysis of organosulfur compounds that can lead to positive added sulfite results in unsulfited dehydrated garlic samples.

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Sullivan, John J., Thomas A. Hollingworth, Marleen M. Wekell, Victor A. Meo, Haytham H. Saba, Ali Etemad-Moghadam, Cheryl Eklund, John G. Phillips, and Barry H. Gump. "Determination Of Total Sulfite In Shrimp, Potatoes, Dried Pineapple, And White Wine By Flow Injection Analysis: Collaborative Study." Journal of AOAC INTERNATIONAL 73, no. 1 (January 1, 1990): 35–42. http://dx.doi.org/10.1093/jaoac/73.1.35.

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Abstract A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution Is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce S02 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but Interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm S02 and 10% for samples at >50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of ≥5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.

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Daniels, Daniel H., Frank L. Joe, Charles R. Warner, Sean D. Longfellow, Thomas Fazio, and Gregory W. Diachenko. "Survey of sulphites determined in a variety of foods by the optimized Monier‐Williams method." Food Additives and Contaminants 9, no. 4 (July 1992): 283–89. http://dx.doi.org/10.1080/02652039209374074.

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Armentia-Alvarez, Arantza, M. Jesus Peña-Egedo, and Concepcion Garcia-Moreno. "Improved Method for Determination of Sulfites in Shrimp." Journal of AOAC INTERNATIONAL 76, no. 3 (May 1, 1993): 565–69. http://dx.doi.org/10.1093/jaoac/76.3.565.

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Abstract A method for the determination of sulfites in shrimp developed by Kim and Kim and modified by Paino-Campa et al. for sausages has been further modified. Total sulfites are extracted by initially adding aluminum oxide to the sample and using an extraction solution at pH 12. In the reproducibility assays, coefficients of variation (CVs) were 4.8% for free sulfite and 7.8% for total sulfite in the edible part of the shrimp. In the inedible part, CVs were 7.5% and 8.9% for free and total sulfite, respectively. Mean recovery was 87.8% for the edible part and 84.4% for the inedible part of the shrimp. The method was compared with the optimized Monier- Williams method. The results obtained with both methods for determination of total SO2 in the edible part of the shrimp did not show significant differences (P= 0.05).

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Stonys, Dalia B. "Determination of Sulfur Dioxide in Foods by Modified Monier-Williams Distillation and Polarographic Detection." Journal of AOAC INTERNATIONAL 70, no. 1 (January 1, 1987): 114–17. http://dx.doi.org/10.1093/jaoac/70.1.114.

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Abstract A rapid, sensitive polarographic method is presented for determining sulfiting agents in foods and beverages. The method is based on the modified Monier-Williams distillation followed by polarographic detection by differential pulse polarography or square wave voltammetry. A clearly defined wave is obtained by both techniques, with a current maximum at a potential (E) of about -600 mV vs an Ag/ AgCl reference electrode. The reaction is based on the reduction of sulfur dioxide at a dropping mercury electrode. Peak current was linear over the range 0-20 μg/mL. Quantitation is done by linear regression analysis of standard addition data or by using a standard calibration graph. Screening levels of less than 1 ppm total S02 were easily achieved in the foods analyzed, which had levels from less than 1 ppm (cereals) to thousands of parts per million (dried fruit). Recoveries from fortified samples ranged from 70 to 108% at fortification levels of 20, 100, and 1000 μg/g.

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Kawamura, Yoshiya, Nobuko Kubo, Haruhiko Arata, Yoshio Ito, Masao Tamura, and Katsuhiko Yamamoto. "A Microbial Sensor for Determination of Sulfite in Wines." Journal of AOAC INTERNATIONAL 77, no. 4 (July 1, 1994): 1052–56. http://dx.doi.org/10.1093/jaoac/77.4.1052.

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Abstract The method developed for determining sulfite in wines uses a microbial sensor that consists of sulfur-oxidizing autotrophic bacteria and an oxygen electrode (SO2 meter; SOM), which selectively determines free sulfite in an acidified wine sample. Total sulfite is determined after alkaline extraction; ferrous sulfate is added to the extractant to prevent oxidation. The SOM data showed a coefficient of a variation of 1 % or less (n = 5). The total sulfites in wine determined by SOM were compared with those determined by the Monier–Williams method. Excellent agreement was achieved, as indicated by the regression line for the data: Y = 1.01 X − 1.39 (r = 0.993). With SOM, sulfite can be determined rapidly and accurately with excellent repeatability.

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Lawrence, James F., Rajinder K. Chadha, and Cathie Menard. "Comparison of Three Liquid Chromatographic Methods with FDA Optimized Monier- Williams Method for Determination of Total Sulfite in Foods." Journal of AOAC INTERNATIONAL 73, no. 1 (January 1, 1990): 77–79. http://dx.doi.org/10.1093/jaoac/73.1.77.

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Abstract Three liquid chromatographic (LC) methods employing amperometric detection were compared with the collaboratively studied FDA optimized Monier-Williams distillation method for the determination of total sulfite in 5 food types. The foods included lemon juice, white wine, instant mashed potatoes, golden raisins, and onion flakes. Two of the LC methods (one employing headspace sampling and the other direct injection) used ion-exchange chromatography with a basic mobile phase (pH about 10.8) and a glassy carbon electrode; the third (employing direct injection) used ion-exclusion chromatography with an acidic mobile phase (pH about 2) and a platinum electrode. All 4 methods produced similar results for the wine, lemon juice, and raisins. Results were different for instant mashed potatoes and onion flakes. The headspace- LC method and direct ion-exclusion LC method, both of which employed an alkaline sample extraction, yielded significantly higher values for sulfite in instant potatoes than did the other 2 methods. A large interfering peak with both direct LC methods prevented quantitation of sulfite in the onion flakes. All methods can detect sulfite as low as about 1 jtg/g in 4 of 5 food types examined.

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Su, Yi‐Cheng, and Steve L. Taylor. "Sulphite analysis of food ingredients: False positive responses with butter flavourings in the optimized Monier‐Williams method†." Food Additives and Contaminants 12, no. 2 (March 1995): 153–60. http://dx.doi.org/10.1080/02652039509374289.

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Holak, Walter, and Bhailal Patel. "Differential Pulse Polarographic Determination of Sulfites in Foods: Collaborative Study." Journal of AOAC INTERNATIONAL 70, no. 3 (May 1, 1987): 572–78. http://dx.doi.org/10.1093/jaoac/70.3.572.

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Abstract A differential pulse polarographic (DPP) method for the determination of "free" and "total" sulfite in foods was collaboratively studied by 8 laboratories. The collaborators analyzed blind duplicate samples of shrimp, orange juice, peas, dried apricots, and dehydrated potatoes. Collaborators also analyzed the same samples spiked with sulfites at 2 levels, which ranged from 10 to 1100 ng added S02/g. The variability of free S02 results was excessive for quantitative analysis, but the method can be used for qualitative detection of free S02. The method for total S02 determination was suitable for as low as approximately 10 μg/g. Recoveries are comparable to those for the official Monier-Williams method at high levels and are superior at low levels. The method has been adopted official first action for determination of total S02 in the foods studied.

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Holak, Walter, and John Specchio. "Determination of Sulfites in Foods by Simultaneous Nitrogen Purging and Differential Pulse Polarography." Journal of AOAC INTERNATIONAL 72, no. 3 (May 1, 1989): 476–80. http://dx.doi.org/10.1093/jaoac/72.3.476.

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Abstract An improved technique has been developed for determination of sulfites in food by differential pulse polarography. A Teflon™ sleeve is fitted to the dropping mercury electrode capillary so that SO2 is purged from the sample and simultaneously detected at peak potential. Bound sulfite in the sample is released at room temperature by addition of base in the absence of oxygen. For some foods, the prepared sample was passed through a Sep-Pak C-18 cartridge to remove naturally occurring sulfur compounds so that only added sulfite is measured. The level of detection was approximately 1 μg S02/g. Results agreed with those obtained by the optimized Monier- Williams method for a variety of foods.

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Sullivan, John J., Thomas A. Hollingworth, Marleen M. Wekell, Richard T. Newton, and Jack E. Larose. "Determination of Sulfite in Food by Flow Injection Analysis." Journal of AOAC INTERNATIONAL 69, no. 3 (May 1, 1986): 542–46. http://dx.doi.org/10.1093/jaoac/69.3.542.

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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.

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Takahashi, Anita Akiko, Maristela Satou Martins, Jussara Carvalho de Moura Della Torre, Camila Cardoso de Oliveira, and Daniel Granato. "Influence of distillation time and sample mass on sulfur dioxide analysis in passion fruit juice through Monier-Williams method." Food Science and Technology 35, no. 3 (August 25, 2015): 434–37. http://dx.doi.org/10.1590/1678-457x.6684.

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Kim, Young-Kyung, Eunmi Koh, Sang-Yong Park, Seung-Yeup Chang, Soo-Jin Park, Won-Il Na, and Hie-Joon Kim. "Determination of Sulfite in Oriental Herbal Medicines." Journal of AOAC INTERNATIONAL 83, no. 5 (September 1, 2000): 1149–54. http://dx.doi.org/10.1093/jaoac/83.5.1149.

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Abstract Sulfite was detected in 7 varieties of Oriental herbal medicines (Pueraria radix, Zingiberis rhizoma, Platycodon radix, Adenophora radix, Pinellia tuber, Astragalus radix, and Paeonia radix) on the Korean market. Sulfiting of commercial Oriental herbal medicines by fumigation with burning bituminous coal was simulated, and the accumulation of sulfite was investigated by using fresh Platycodon radix roots obtained from a growing field. The sulfite level reached a plateau in 9 h, and the maximum sulfite level found by the Monier-Williams (MW) method (AOAC 990.28) was 1020 ppm. The sulfite content in the simulated Platycodon radix sample determined by alkali extraction followed by ion-exclusion chromatography with electrochemical detection (AOAC 990.31) was approximately 17% lower on average than the MW results. Free-sulfite levels determined by acid extraction and ion-exclusion chromatography with electrochemical detection were between 19 and 49% of the MW results. The advantages of different methods for sulfite determination and the significance of the results are discussed.

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Lawrence, James F., and Rajinder K. Chadha. "Determination of Sulfite in Foods by Headspace Liquid Chromatography." Journal of AOAC INTERNATIONAL 71, no. 5 (September 1, 1988): 930–33. http://dx.doi.org/10.1093/jaoac/71.5.930.

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Abstract Sulfite was determined in a variety of foods by liquid chromatography (LC) after the samples were mixed with a solution containing mannitol, FeS04, and Na2HP04, adjusted to pH 11, and left to stand for 15 min at room temperature. An aliquot of the mixture was placed in a headspace vial and mixed with 50% H3P04. After 15 min, a portion of the headspace was removed with a syringe containing LC mobile phase without acetonitrile. The syringe was shaken and an aliquot of the solution was analyzed on an anion exchange column with a mobile phase of 0.03M methane sulfonate (pH 10.8) containing 5% acetonitrile. Sulfite was detected amperometrically (glassy carbon electrode) at +0.7 V. The method was successfully compared to the FDA-modified Monier-Williams procedure for a variety of foods. Minimum detectable levels were about 1 ng/g, based on a 15 g sample

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Perfetti, Gracia A., Frank L. Joe, and Gregory W. Diachenko. "Liquid Chromatographic Determination of Sulfite in Grapes and Selected Grape Products." Journal of AOAC INTERNATIONAL 72, no. 6 (November 1, 1989): 903–6. http://dx.doi.org/10.1093/jaoac/72.6.903.

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Abstract A liquid chromatographic (LC) method is described for the determination of sulfite in grapes and certain grape products. Sulfite is extracted from grapes with aqueous formaldehyde solution buffered at pH 5; free sulfite is converted to hydroxymethylsulfonate (HMS), which is extremely stable at pH 3-7. Subsequent heating to 80°C for 30 min converts reversibly bound forms of sulfite to HMS. The extract is then analyzed by reverse-phase ion-pairing liquid chromatography, using a Cjg column and a mobile phase of aqueous 0.005M tetrabutylammonium ion in 0.05M acetate, pH 4.7, and a flow rate of 1 mL/min. Aqueous KOH is added to the eluate to convert HMS to free sulfite, which is then treated with 5,5'-dithiobis[2-nitrobenzoic acid]. This reaction produces the 3-carboxy-4-nitrothiophenolate anion, which is determined by measurement of electronic absorption at 450 nm. For grapes spiked with HMS at 5-20 ppm (as S02), recoveries ranged from 92 to 112%, with a coefficient of variation of 4.6%. The method was also used to determine sulfite in various grape products. Results were comparable to those obtained by the AOAC official Monier-Williams method.

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Wygant, Michele B., John A. Statler, and Alan Henshall. "Improvements in Amperometric Detection of Sulfite in Food Matrixes." Journal of AOAC INTERNATIONAL 80, no. 6 (November 1, 1997): 1374–80. http://dx.doi.org/10.1093/jaoac/80.6.1374.

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Abstract Sulfite is added to foods as an antimicrobial, antibrowning agent, or antioxidant. It also can occur naturally, and is often used in the production of beer and wine. For years the standard methodology for determination of sulfite in foods has been the Monier–Williams method, which is a combination of acid distillation and titration. Recently, AOAC adopted a chromatographic method based on a method developed by Kim and Kim for the determination of sulfite. The method combines ion exclusion chromatography with direct-current (DC) amperometric detection to provide more convenient and accurate quantitation of sulfite. However, fouling of the platinum working electrode results in a rapid decrease in method sensitivity. As a result, standards must be injected before and after every sample, and the electrode must be polished frequently to maintain adequate detection limits. Pulsed amperometric detection overcomes electrode fouling problems by repeatedly and continuously applying cleaning potentials to the working electrode. Using this technique, a reproducible electrode surface can be maintained, and injection-to-injection repeatability is greatly improved. A comparison of method performance for both DC and pulsed amperometric detection is presented. Also investigated was the stability of sulfite samples at varying pH, and in the presence or absence of a preservative.

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Perfetti, Gracia A., and Gregory W. Diachenko. "Determination of Sulfite in Dried Garlic by Reversed-Phase Ion-Pairing Liquid Chromatography with Post-Column Detection." Journal of AOAC INTERNATIONAL 86, no. 3 (May 1, 2003): 544–50. http://dx.doi.org/10.1093/jaoac/86.3.544.

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Abstract A method is described for determining sulfite in dried garlic. Garlic is extracted with an HCl solution to inhibit the formation of allicin, which interferes with the determination of sulfite. After cleanup of the extract on a C18 solid-phase extraction column, sulfite is converted to hydroxymethylsulfonate (HMS) by adding formal-dehyde and heating to 50°C. HMS is determined by reversed-phase ion-pairing liquid chromatography with post-column detection. The post-column reaction system consists of the addition of KOH to convert HMS to sulfite ion, followed by the addition of 5,5'-dithiobis(2-nitrobenzoic acid) to produce 5-mercapto-2-nitrobenzoic acid which is detected spectrophotometrically at 450 nm. Background levels in unsulfited dried garlic equivalent to <20 ppm SO2 were found. Recoveries of HMS from spiked garlic averaged 94.8% with a coefficient of variation of 3.8%. Sulfite was found in 13 of 21 samples of dried garlic produced in China, with sulfite ranging from 114 to 445 ppm. Sulfite was found in 60% of commercial dried garlic products purchased locally. The suitability of the Monier-Williams method for determining sulfite in garlic is discussed.

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Carlos, Katherine S., and Lowri S. de Jager. "Determination of Sulfite in Food by Liquid Chromatography Tandem Mass Spectrometry: Collaborative Study." Journal of AOAC INTERNATIONAL 100, no. 6 (November 1, 2017): 1785–94. http://dx.doi.org/10.5740/jaoacint.17-0033.

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Abstract Sulfites are added to a wide range of food and beverage products to prevent browning or oxidation. Although most of the population do not experience side effects from consuming sulfites, a small subset has been shown to experience an “allergic-like” response. For this reason, the U.S. Food and Drug Administration requires that sulfites be labeled on all products that contain more than 10 mg/kg (parts per million) sulfur dioxide. The current regulatory method, optimized Monier–Williams (OMW) Official Method990.28, has been successful in quantifying sulfites in most matrixes, but is time-consuming and has a method detection limit at the regulatory-labeling threshold. Recently, an LC-tandem MS (MS/MS) method was published that was applicable to a wide range of sulfite-containing matrixes. This method converts free and reversibly bound sulfite to the formaldehyde adduct hydroxymethylsulfonate, which could then be separated from matrix constituents using a hydrophilic interaction LC analytical column and subsequently be detected with tandem MS (MS/MS). In this study, multilaboratory validation was conducted with 11 laboratories in the United States and Canada. Four matrixes were spiked at varying concentrations and three additional commercially sulfited matrixes were included. An abbreviated comparison study between the LC-MS/MS and OMW methods was conducted for select samples. Average recoveries for all matrixes ranged from 86 to 114% with RSDr and RSDR values of 4.5–17.5 and 8.6–22.5%, respectively. Further comparisons will be necessary to draw comparisons between the two methods. This method proved to be a faster and more sensitive way to determine sulfites in food and beverages, showing promise for the continuing improvement of enforcement of sulfite labeling requirements to protect individuals who have sulfite sensitivity.

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Iammarino, Marco, Aurelia Di Taranto, and Diego Centonze. "Determination of Sulphiting Agents in Raw and Processed Meat: Comparison Between a Modified Monier-Williams Method and the Direct Analysis by Ion Chromatography with Conductometric Detection." Food Analytical Methods 10, no. 12 (June 21, 2017): 3956–63. http://dx.doi.org/10.1007/s12161-017-0960-9.

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Rongtong, Bumrungrat, Thongchai Suwonsichon, Pitiporn Ritthiruangdej, and Sumaporn Kasemsumran. "Determination of sulfur dioxide content in osmotically dehydrated papaya and its classification by near infrared spectroscopy." Journal of Near Infrared Spectroscopy 26, no. 6 (October 25, 2018): 359–68. http://dx.doi.org/10.1177/0967033518808054.

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Sulfur dioxide (SO2) is used as a preservative in osmotically dehydrated papaya to improve product quality and extend shelf-life. The potential of near infrared spectroscopy, as a rapid method, was investigated to determine sulfur dioxide in osmotically dehydrated papaya. Commercial and laboratory osmotically dehydrated papaya samples were selected to determine the sulfur dioxide content using the Monier–Williams method. From the total of 350 samples, subsets were selected randomly for the calibration set (n=250) and validation set (n = 100). Near infrared spectra in the region 800–2400 nm were measured on the samples of osmotically dehydrated papaya. Quantitative analyses of sulfur dioxide in the osmotically dehydrated papaya and their qualitative analyses were carried out using multivariate analysis. Before developing models, a second derivative spectral pretreatment was applied to the original spectral data. Subsequently, two wavelength interval selection methods, namely moving window partial least squares regression (MWPLSR) and searching combination moving window partial least squares (SCMWPLS), were applied to determine the suitable input wavelength variables. For quantitative analysis, three linear models (partial least squares regression, MWPLSR and SCMWPLS) and a non-linear artificial neural network model were applied to develop predictive models. The results showed that the artificial neural network model produced the best performance, with correlation coefficient (R) and root mean square error of prediction values of 0.937 and 114.53 mg SO2 kg−1, respectively. Qualitative models were developed using partial least squares-discriminant analysis and soft independent modeling of class analogy (SIMCA) for the optimized combination of informative regions of the near infrared spectra to classify osmotically dehydrated papaya into three groups based on sulfur dioxide. The SIMCA in combination with SCMWPLS model had the highest correct classification rate (96%). The study demonstrated that near infrared spectroscopy combined with SCMWPLS is a powerful procedure for both quantitative and qualitative analyses of osmotically dehydrated papaya. Therefore, it was demonstrated that near infrared spectroscopy could be effective tools for food quality and safety evaluation in food industry.

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Alonso, Sandra Salleres, Irune González, Naiara Linaza, Erlantz Ramos, Mónica Fernández, Roberto González, Sonia Maza, et al. "Validation of the Biofish-300 SUL Enzymatic Biosensor for the Detection of Sulfite in Crustacean." Journal of AOAC INTERNATIONAL 102, no. 2 (March 1, 2019): 539–56. http://dx.doi.org/10.5740/jaoacint.18-0124.

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Abstract Background: Sulfites are some of the oldest and most widespread preservatives in our food supply. They are food additives that have antioxidant properties, but they are also recorded as allergens by the main international regulatory bodies on food safety because of their adverse healtheffect. Hence, sulfites maximum concentration in foodstuff is regulated and they must be ensured by the agro-food processing industries. The most widely used technique for the quantification of sulfites is the Modified Monier-Williams (AOAC Official Method 990.28). Objective:In this method, SO2 is released from sulfites and some bound compounds when the sample is mixed with an acid (normally hydrochloric acid, but sometimes phosphoric acid) and heated. The SO2 is distilled using a stream of nitrogen gas,which carries the gaseous SO2 into an absorbing solution of hydrogen peroxide (H2O2) where it is oxidised to sulphuric acid. The amount of SO2 distilled into the H2O2 is determined by titration with 0.1M sodium hydroxide. Apart from being time consuming (at least 2 h) and the usage of toxicsolvents, the method presents some other disadvantages that make it inappropriate as a routine-controltechnique for the agro-food industry. Hence, the industry demands simple, fast and accurate methods for sulfite level monitoring. Methods: BIOLAN is a SME that develops and commercializesbiosensors for quantitative analysis of food quality and safety parameters, based on its proprietary enzyme-based electrochemical biosensor technology platform. This technology enables high accurate and robust analysis with a compact device that help the users to control the quality in an easy and safety manner. Biofish-300 SUL method is a highly specificenzimatic biosensor for the rapid quantification ofsulfite, measured as SO2 content, in crustaceans. It consists on the extraction of sulfitein an aqueous based solution, by the aid of an Ultra-turrax or similar, and its subsequent quantification by the biosensor after previous calibration (3 min). Results: Sulfite in raw shrimp head-on, raw shrimp head-off, and boiled shrimp was analyzed, and performance was examined using naturally contaminated and spiked samples by comparisons with AOAC Official Methods of AnalysisSM (OMA) 990.28. Linearity, selectivity, matrix, consistency, and robustness were evaluated. All results were within acceptable ranges except robustness, which reflected deviation in the sample volume and ultraturrax time compared with the standard assay procedures describedin the Biofish 300 SUL Instruction Manual. Accuracy, assessed as a comparison of the Biofish results with the OMA results, ranged from 82 to 115% in all samples except for fortified raw shrimp head-on, inwhich the low level yielded an accuracy of 138%. The method bias was in general negative in both incurred and fortified high levels, and slightly positive in incurred low levels. Repeatability was very good as shown by the low RSDr values, demonstrating acceptable repeatability precision with results <10% in most of the evaluated values. Regression analyses showed a good correlation between the Biofish and OMA methods with R2 = 0.99 in all cases. Conclusions: As awhole, accuracy, recovery and bias within range results indicate that the kit provides accurate and precise sulfite quantification for all the evaluated matrices, confirming that sample preparation and assay procedures produce acceptable results. Biofish 300 SUL has proved to be a suitable tool for monitoring sulfite levels in quality control routines dueto its high accuracy, precision, rapid response andease of use. Highlights: With a simple sample preparation, results are obtained in approximately 3 min, making a big difference with other technologies that require specific skills or tedious sample pretreatments and analysis procedures.

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Journal articles on the topic 'Monier-Williams method'

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