Chromatography Forum

An engineer in my group would like me to monitor changes in artificial sweat (perservative, salts and amino acids). I don't have to know what they are, just be able to notice any changes. I have the common HPLC(UV, ELSD) or GC (FID) systems. Can anyone advise me?
Thanks

Hi LC101,

If you don’t know what the composition is, how are you supposed to develop a method for monitoring it?
Judging from the vague description of the potential samples, I’m not sure you can develop a single analytical method for all these, quite unrelated, substances. The detection is a tricky business as well; I don’t know what preservatives might be present in this liquid, but some of them can be UV active, some salts can also be detected by an UV detector and finally some amino acids too, absorb light in the UV region (e.g. aromatic AA).
What I’m quite sure of, is that there is not a chance that all of them will absorb light at the same wavelength. In addition to that it won’t surprise if a considerable share of the salts will be sodium chloride, which will be undetectable by the UV detector.
You might try to consider the ELSD option, but then you won’t be able to use any salts in your eluents which will limit your separation mode options. GC? I won’t even consider it in the context of salts.
To make a long story short: I think you should find out exactly what substances you are going to deal with and take your time for considerations and plans. At last but not least, prepare your self for a serious method development.
If you need some suggestions from this board - when you know the exact composition of this liquid - then let us know what you’re facing and I’m quite sure some of the guys here will be able to come up with more concrete advises.

Best Regards

Thanks for the reply. I'm not in the biology field so this is quite new to me. Our test internally would be to see how our product holds up to sweat.
Therefore they want to monitor the material internally with a quick HPLC method.
The exact material is "Artificial Eccrine Perspiration" from Pickering Labs in CA. Cat # 1700-0020. MSDS says:
19 amino acids, 10 minerals, 4 metabolites and a perservative. My research so far indicates I could do the analysis on a "Primesep" column and use ELSD. No derivatization.

Oh, I see – the test should monitor a substance/drug dissolved in this artificial sweat.
I got the impression that the aim of the test was to monitor the artificial sweat it self and that would’ve been a completely different story – according to my earlier reply.
Well, as I understand, you’re on track then.

Good luck

My message didn't read like I wanted it to. The material I want to check is the sweat. The sweat will be used in another test that involves our product. We want to make sure there are no changes in the sweat from one month to the next. We want to ensure this variable is constant in the "product" testing.

Why not speak to the manufactures they should have data on stability.

In terms of the minerals I would expect them to be stable. Some amino acids tend to degrade especially cysteine which I do not know if you have them in your mixture. Asparagine and glutamine are also slowly change to their respective acids (Asp and Glu). Probably your preservative will be one of the first to start degreade...

A quick and dirty way is to monitor the ELSD chromatogram over time and if changes overtime then your mixture is degrading if it stays identical then you "might" be OK... But of course the best way is to identify the compounds of your mixture, buy standards, separate them etc etc...