This page summarises the procedures and equipment needed for two commonly used techniques for measuring sulfur dioxide in wines (aeration/oxidation and reaction/titration). Automated systems are available for SO2 analysis and offer considerable benefits to laboratories that routinely analyse relative large numbers of samples.
Aeration/oxidation (Rankine and Pocock)
Three demonstration videos are available on the AWRI YouTube channel for different aspects of this method:
Description: Sulfur dioxide is sparged from an acidified wine sample in an air stream and trapped in a solution of hydrogen peroxide which oxidises the sulfur dioxide to sulfuric acid. The sulfuric acid formed is then titrated with standardised sodium hydroxide, and the amount used is proportional to the amount of sulfur dioxide in the wine. Total SO2 is determined by heating an acidified sample during the aspiration step (Rankine and Pocock 1970).
Equipment: 100 mL round bottom flasks, 2-necked pear-shaped flasks, condensers, retort stands, bunsen burners, flasks, burette
Reagents: Phosphoric acid solution, standardised sodium hydroxide solution
Services: Water supply, sink, natural gas supply, compressed air
Space required: Bench space
Reaction/titration (Ripper)
Description: The acidified wine sample is titrated with iodine in the presence of starch indicator so that when excess iodine appears in solution it turns blue as the end point. Total SO2 is determined by adjusting the sample pH to alkaline conditions and then incubating in the dark to release the bound fraction as free, which can then be determined. It should be noted that this technique is not commonly used in Australia and, in particular, many consider it to be of limited use in red wines.
Equipment: Flasks, burette
Reagents: Sulfuric acid solution, Standardised iodine solution
Services: Wash-up area
Space required: Bench space
References and further reading
- Amerine, M.A., Ough, C.S. 1980. Methods for analysis of musts and wines. New York Wiley-Interscience.
- Iland, P., Ewart, A., Sitters, J., Markides, A., Bruer, N. 2000. Techniques for chemical analysis and quality monitoring during winemaking. Campbelltown, SA Patrick Iland Wine Promotions.
- Rankine, B.C. 1998. Making good wine: a manual of winemaking practice for Australia and New Zealand. South Melbourne, Sun Books (Macmillan Australia).
- Rankine, B.C., Pocock, K.F. 1970. Alkalimetric determination of sulphur dioxide in wine. Aust. Wine Brew. Spirit Rev. 88(8): 40, 42, 44.
- Wilkes, E. 2018. Practical measurement of total SO2. Wine & Viticulture Journal 33(4): 32-34. (PDF)
- Zoecklein, B.W.,Fugelsang, K.C., Gump, B.H., Nury, F.S. 1995. Wine analysis and production. New York Chapman & Hall.