sorbic acid

[mmegliol]

Hello,

I’m trying to finalize a method to measure the content of sorbic acid in juice or wine sample.

I found different method online and I actually pick one that on my system has a good performance:

Mobile phase 77% acetate buffer, 23% acetonitrile
Flow 1.5
det 254
Column synergy 4u MAX –RP 80A from phenomenex at 30C.

I usually take off the color with active carbon on all my sample and filtering at .45 before injecting, but if I take out the color on wine or juice sample I loose almost all the sorbic acid, anybody can explain me why?

Right know I’m diluting the sample 10 times and filtering at .22 but I’m afraid to damage the column!

Thanks.

Matteo.

[juddc]

I'd guess that the sorbic acid is adhering to the carbon just as it does your column.

I might try a few things:

1. Use some solvent to elute the sorbic acid from the carbon (I'm assuming that your carbon is in a cartridge).

2. Use a reversed phase SPE support and do the same.

3. Increase the pH of your sample to about 5.5 where your sorbic acid will become sorbate and should elute easily from any RP SPE support or carbon. Watch for oxidation at the higher pH, though...I might be tempted to dope with an antioxidant (dilute thiosulfate, dtt, BHT sulfite, something)

Be sure to use a guard column if you're going to continue the dilute and shoot method...

Check the literature, too. There's a huge body of knowledge surrounding the analysis of wine. Feel free to drop a note to christopher.judd at basf dot com if I can help there.

[Bryan Evans]

Below is an application for sorbic acid and benzoic
acid in soy sauce separated by Cadenza CD-C18:

http://www.silvertonesciences.com/files/TI034E.pdf