Practical investigations
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I'm using AO method for determining free and bound SO2 in wine with high concentration of volatile acids in it - vinegar. In the article about SO2 on www.brsquared.org/wine in section 14.2, it is written that this method gives false-high measurement in wines with high volatile acidity. So, my question is: does AO method gives false-high measurement for both free and bound SO2, and how can I overcome these inaccuracies in the AO method. I can't understand this article.
Igloo writes ...
As I said in my last answer, you are unlikely to find a better web article than this to give you a comprehensive description of the various means of analysing for the SO2 in wines – both bound and unbound.
If you read section 14.2 carefully you will see that it states at the end: “despite these potential inaccuracies, the AO method gives reproducible results and has been noted as having an accuracy with just a 2.5-5% error”. In other words, even professional scientists are unlikely to do better than this, so the simple answer to your question is that you cannot improve the technique any further.
Why don’t you have a go at using the Ripper method instead? Although it too has its own shortcomings (see section 14.2 again), I know from experience that it gives excellent results, and is far easier to set up and carry out.
If this is part of an assessed investigation, it will look very impressive if you have used two quite different methods of SO2 analysis, and can assess the shortcomings of each technique in your report.
Always carry out a risk assessment and check with your teacher before starting any practical work.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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updated: 22 July 2007
