Determination of quaternary ammonium preservatives

[mross]

I have a quaternary ammonium salt with a UV at 205nm. It is unretained on RP without ion-pairing. The problem is that with all the ion-pairs that I know they have strong UV adsoprtion.


ANy ideas,

[Uwe Neue]

Depends on the concentration that you need to detect. There is a technique around with UV-absorbing ion-pair reagents, where you look for the concentration of the ion-pair against the ion-pair background to detect the analyte. You could use that trick, but I doubt that the sensitivity is very high.

Alternatively, you could try HILIC with a silica column and an acetonitrile-phosphate buffer mobile phase.

[SIELC_Tech]

Hi Malcolm,

Here are few applications for retention/separation of quaternary compounds on Primesep columns. No IP reagent required. Compounds are retained based on reverse phase and cation exchange (anion exclusion) mechanisms:

http://www.sielc.com/compound_080.html

Contact me directly if you need more information or would like us to develop method for you (free of charge).

Regards,

Vlad

[Mark Tracy]

You can try 10mM HClO4 as an ion pairing agent; it ion-pairs about as well as TFA, and has much better UV properties. The alkane sulfonic acids have good UV properties and are stronger ion-pairing agents. You can also look into evaporative light scattering or suppressed conductivity detection. I have done quaternary surfactants like benzalkonium chloride on an Acclaim Surfactant column with conductivity detection, and it gets better detection limits than ELSD and sometimes better than UV.

[ym3142]

mross,
the common used IP are alkane sulfonic acid and tetraalkylammonium. I do not have an impression of either one having strong UV.
Could you let me know what kinds of IP you tried?Thanks

[dpr]

Hi,

I realise it's a while since this was posted, however.

We have some experience of quartenary ammonium salt determinations by IC.

Iodine salt of Bis-Dibutyl Ethyl Ammonium Hexane is analysed on Dionex NS1 columns.
MSA eluant with methanol solvent.

Drop me an email if you want any information

[Wen Jiang]

mross,
Another possibility is using HILIC. One typical example can be found in the following web address: http://www.sequant.com/sn/ufiles/SeQuan ... 00-14A.pdf