taurine in energy drinks

[marinad]

hello, is there anyone who can tell me something about determination of taurine in energy drinks? i have a method using hplc uv-detection (after derivatisation with dansylchloride), which works perfectly for analysing sugar free drinks and components, but when it comes to a sample with a 'normal' sugar concentration, it is not possible to detect the right amount of taurine in this sample. i have no clue why this is so. can you help me, please

[SIELC_Tech]

Dansyl chloride will react with amines and alcohols. Reaction with amine is much faster but considering that you have sugars in higher concentration with multiple hydroxyl groups and that you amine is zwitterionic you are equalizing these two reactions (between sugar and dansyl chloride and between sugar and taurine). If you are not using enough dansyl chloride some of your taurine is not derivatizing and you have lower reading. Also derivatized sugars probably causing interference. You need to use excess darivatizing agent in order to address these two issues. Also you might need method to remove derivatized sugars from derivatized taurine.

Another approach would be to use different mechanism to separate sugars from taurine and different detection technique (ELSD, LC/MS)

[Mark Tracy]

Or use an amine-selective derivitization reagent. The much-maligned OPA/thiol chemistry does not react with alcohols. Fluorescamine is also amine selective.

[marinad]

wow, didn't expect such a reply so fast... thank you for your tips, i used an other dilution (100 instead of 10)of my sample and now it works...


marinad

[ym3142]

marinad,
would you mind kindly explaining to us what's going on? why 10 dilution not work and 100 works?

[Mark Tracy]

By diluting the sample 100x versus 10x, but keeping the Dansyl chloride the same, the amount of species competing for the reagent goes down 10x. Since there is sensitivity to burn with fluorescence detection, and lots of taurine in the sample, this works. The original problem was that the sample had too many substances competing for the reagent, and the taurine was not being completely converted before the reagent was exhausted. This is a general problem for pre-column derivitization methods, and must be addressed as part of the development process.

[ym3142]

Mark,thank you.
Jim