Chromatography Forum

I am trying to develop a method for either the LC exclusively or the GC exclusively. I have an air sanitizer that has dipropylene glycol, triethylene glycol, and BTC 8358, which is a quat (Benzalkonium Chloride). Can anyone steer me in the right direction for LC columns that will detect a quat and an LC column for detecting glycols. They do not have to be the same column. I use an UV detector. If you know of a good GC column for both I would appreciate that info. I use an FID detector. Thank you.

One of the approaches which can work is mixed-mode HILIC (not regular HILIC). Glycols will retain by HILIC mechanism and benzalkonium will retain based on cation-exchange mechanism. UV is not going to work because glycols are not UV-active. You need RI, LC/MS or ELSD (very low temperature set up 30*C).
GC will not work because you will have hard time evaporatiing benzalkonium chloride

Yep, GC will only work for the glycols, not the benzalkonium chloride.

Personally, I'd homogenize or extract with DMF and use trimethylsilylation and GC for the glycols, and then do the quat by HPLC with UV detector. You'll likely get multiple peaks from that quat.

Likely your management wants one assay that does all that's idiotproof and can be done in three minutes by an untrained union worker.....

Hey do you work for my company!!! Haha! Do you also like the mix-mode HILIC column for the quat?

Vlad.....What type of solvents will I need (ratio) and at what wavelength will I need to be at for the quat?

You will need ELSD/RI/LC/MS for glycols, benzalkonium you will see at 200-270 nm. You will need 85-93% ACN to retain TEG, at these conditions you will need cation-exchange to retain quat (that is why HILIC/mixed-mode with cation-exchange might work), which will require some ions in the mobile phase to facilitate cation-exchange. We are running something in the lab for you. Send me your email to get results.

If you don't have ELSD, you might need to do derivatization of glycol with UV-active derivatizing agent, or use indirect detection (which I don't like)

Below are two applications for benzalconium chloride on Unison UK-C18 and Scherzo SM-C18:

http://www.imtaktusa.com/site_media/fil ... TI197E.pdf
http://www.imtaktusa.com/site_media/fil ... TI543E.pdf

We managed to develop isocratic method for simultaneous analysis of triethylene glycol and cetylpyridinium chloride on Obelisc N mixed-mode HILIC column (4.6x150 mm). Glycol is retained by HILIC mechanism, cetylpyridinium by cation-exchange mechanism. Mobile phase 90% ACN with 5 mmol ammonium acetate pH 5, detection ELSD/LC/MS (no UV for glycols). Retention time 3.2 min for glycol and 5.5 min for cetylpyridinium chloride. I don't have ability to post chromatigrams here, but can send it by email.

The task was to analyze both compounds on one column with one set of conditions, there is no problem to retain neither benzalkonium chloride (C8-C18 chains) nor cetylpiridinium chloride (C18 quat). There are tons of methods for this type of compounds. Main problem is peak tailing with symmetry around 0.5-0.6. If you do gradient you can improve peak shape, but it is still going to tail due to residual silanol interaction (reference above has tailing even with gradient). If you shield silanols with basic group (how it is done on Primesep D column) you will have a perfect peak shape even with isocratic conditions, but none of RP columns (including Primesep D), will provide SIGNIFICANT retention for glycols.

http://www.sielc.com/application_151.html (you can use other buffers with this column, but peak shape will be the same)

So you need either two methods with GC for glyclos and Primesep D for benzalkonium, or mixed-mode HILIC on Obelisc N column. ELSD might not be accurate for glycols due to volatility (we used 30*C and linearity is not that great)

Other choices include derivatization of glycols with UV-active derivatizing agent which will provide additional hydrophobicity and UV activity. In this case you can use Primesep D for perfect peak shape.

I just wanted to update everyone on the progress I have made developing an all inclusive method to detect glycols and Benzalkonium Chloride. I purchased an SIELC Primesep D column and used a derivatization with Phenyl Isocyanate to complete my method. The column works flawlessly; I have excellent peak shape, resolution and repeatability (± 0.88%) even with the derivatization of the glycols. The method is only 18 minutes long.

Thank you everyone for all your help!