Chromatography Forum

I am in the food industry developing a new application with Pulsed Amperometric Detection on a gold electrode at high pH for detecting ‘sulphite’; or sulphur dioxide as we prefer to call it.

They use it as an anti microbial thing especially in wine and grape juice and some people are allergic to it etc etc

Looks better than an AOAC method and this;

http://www.dionex-france.com/library/li ... 004-01.pdf

I think.

Need help optimising the PAD settings or waveform etc as there doesn’t appear to be any literature on it.

And don't have one of those cyclic voltametry things.


I am new on this forum

We did sulfite so far with DC only, at 150 mV at Gold electrode (Pd reference).

If you need to do PAD run a cyclovoltammogram (scan) to find best working potential and use standard oxidizing and reducing potentials. These depend on the brand of your PAD.

thanks.

I have got two 25 year old dionex "PED"s that I don't think do voltramertry scan's.

I have got Edet at 0.19 and and 'cleaning' potentials or whatever at 1.00 and
-0.9 against a Ag referance.

That might be the best for all I know, I just increased it and decreased it etc during different runs.

I have been doing sugar analysis by PAD for about 20 years but not too sure I fully understand the theory.

I am trying to optimise the chromatography separation as well and I am sometimes getting a bit of an annoying kick in the baseline after the sulphite peak.

I suspect I need a more strongly buffered eluent.

I am trying to keep it below pH 11 to stop sugars, which are likely to be a
major part of the sample matrix, responding to the PAD.

How dependent is the PAD response to pH or does that vary according to the analyte?

It does look good at the moment though, 10mg/L on a 25ul loop gives you a whacking big peak.

Well I have made the cleaning potentials less vicious and gone to 0.19; 0.6; -0.1; and it is much better re baseline etc.

It is better than the dionex/AOAC method.

It can easily quantify less than 10ppm in wine and it is on a 25ul loop and 1/10 dilution so plenty to play with.

It has good linearity over 5/10 to 50/10.