SO2 Testing with Chemicals

[kuziwk]

I setup my lab which is basically the same as the morewine MT140. At any rate im having issues with accurate results, basically lower than expected sulphites. I think the main issue is that im using a wine theif to draw up the wine and transfer it to a glass, from the glass i measure out 20ML and put it in the test beaker. Thats basically handling the wine twice, am i aerating it? Also i sanatize the wine theif with star stan which contains watered down phosphoric acid, could these be eradicating the sulphite before it even hits the test beaker?

 

[stickman]

I also use a similar wet method for sulfite testing. I don't think either of those issues are very significant. The main issue with the test is NaOH normality, it degrades over time so usually you get false high results, therefore it's best to standardize with KHP which is available from PIWine. I used to purchase NaOH at .01N for the test, but now make up my own, that's because a major supplier once sent me .1N NaOH labeled as .01N, obviously my test results were low by a factor of 10. Other issues include weak hydrogen peroxide and incorrect air flow rate.

Why do you think the so2 results you're getting are low?

 

[kuziwk]

I also use a similar wet method for sulfite testing. I don't think either of those issues are very significant. The main issue with the test is NaOH normality, it degrades over time so usually you get false high results, therefore it's best to standardize with KHP which is available from PIWine. I used to purchase NaOH at .01N for the test, but now make up my own, that's because a major supplier once sent me .1N NaOH labeled as .01N, obviously my test results were low by a factor of 10. Other issues include weak hydrogen peroxide and incorrect air flow rate.

Why do you think the so2 results you're getting are low?

i used 4g sulphites at clearing as per the kit than accidentally added another 4g 3 months later. I should mention my NaOH froze a little bit in the fridge. Would this affect it? I shook it really well to remix the small ice chunk after waiting for it to melt. I think another issue is all the sulphite has not been fully removed the sample, tested again and its still turning the solution pink after 15 minutes. Is it bad to leave the sample longer than 10-15 minutes? I also am not using phosphoric acid but sulfamic acid crystals 2% weight per volume as suggested in another thread from some years ago.

Edit: perhaps i didnt have the bubbling high enough, im running the test again with the same sample once i brought the indicator solution back to neutral. Going to leave for a few hours and see if there is anything. So i guess my main question is...is it bad to leave the sample bubbling longer than 15 minutes.