What are the differences between the different Sulfur Dioxide (SO2) applications for the AT1000?

Document ID

Document ID TE8533

Version

Version 2.0

Status

Status Published

Published Date

Published Date 04/10/2018
Question
What are the differences between the different Sulfur Dioxide (SO2) applications for the AT1000?
Summary
Differences between Free, Double, Total, and Total with sample preparation SO2 applications.
Answer
The Titration Application Pack Food & Beverage: SO2 in wine (Product # AP0012.AT1122) and Titration Application Pack, Food & Beverage: pH, Total Acidity & SO2 in wine (Product # AP0013.AT1222) both include the following applications on the application flash drive:
  • Free SO2
  • Double SO2
  • Total SO2
  • Total SO2 w/ Sample prep.
  • Sample Preparation
These are the different forms of SO2:
  • Free SO2 is a measurement of SO2 directly in an acidic media.
  • Combined SO2 is converted to free SO2 by hydrolysis in alkaline media. 
  • Total SO2 is the sum of the free SO2 with the combined SO2.
For the Free SO2 application, Sulfuric Acid is added to the sample and the titration is done immediately to measure only free SO2. This is the recommended application if only free SO2 is required.

The Double SO2 application starts with a free SO2 titration followed directly by the addition of excess Sodium Hydroxide and a 5 minute hydrolysis step. Then the sample is re-acidified with excess Sulfuric Acid and a second titration is performed to measure combined SO2. The two results are added together and at the end of the test free, combined, and total SO2 results are all displayed. This is the recommend application if any two or more forms are required.

For the Total SO2 application, Sodium Hydroxide is added followed by a 5 minute hydrolysis step followed by acidification with excess Sulfuric Acid and a titration performed to measure only total SO2. This is the recommended application if only total SO2 is required and samples are measured one at a time or as needed.

The Total SO2 w/ sample prep. application requires that the sample preparation application is performed in advance. The sample preparation application adds the Sodium Hydroxide and counts the hydrolysis time and can be repeated for several samples. Samples that have already gone through the hydrolysis step in the sample preparation application can then be ran on the Total SO2 w/ sample prep. application where the excess Sulfuric Acid is added and the titration performed to measure only total SO2. **Note: This is not the sample as just running the Free SO2 application after doing the Sample Preparation application because more Sulfuric acid is added in the Total SO2 w/ Sample prep. than in the Free SO2 application to account for the addition of the Sodium Hydroxide in the sample preparation. This is the recommended application if only total SO2 is required and multiple samples would need to be measured in a row.

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