Hi.

The ELSD will, depending on the size of your target compounds, be ok. Personally, I prefer MS, so if you can, use this one.

RP columns should provide an efficient separation. Again depending on your specific compounds, you can try different phases or even setting different columns in line before detection. I leave you a paper that will provide good insight about this:

Article Simultaneous analysis of anionic, amphoteric, nonionic and c...

Cheers!

Thank you, Mario!

Hello,

In my opinion, in order to decide which detector is suitable for detection of your target surfactants/liquids, first you should check the structure of these surfactants/lipids. If the target compounds do not contain a conjugated system, it is technically difficult to be detected in UV wavelengths. You can deal with this issue by make a derivatization (I will prefer to search from references to obtain basic information.). If you have a MS system, it should be good, but you should be careful with light compounds because it will be significantly affected by ion suppression from the matrix. Good luck!

Thanks, Trac

The surfactants are typical ionic and non-ionic compounds and do not absorb up very low 200s nm. I'd like to avoid derivatization, so I'm in a search of alternative detector. So far the ELSD seems to be the best option available to us moneywise

For me, I would recommend you changing the HPLC technique with another one because it is not an effective technique with the surfactant.

The analysis of surfactants is always problematic.

I have made my experience with the analysis of Tween 20 and Tween 80 in pharmaceutical samples. Both are non-ionic detergents with EO chains and esterified with fatty acids and both are not UV active.

For me the question arises in which concentration range the analytes are present and what kind of analytes are involved.

The ELSD is probably not so optimal for low concentrations.

I used LC-MS for the Tween analysis, the concentration range was 20- 200 mg/l.

The selectivity could be selected by a MS^3 transition.

The column I am using is the Polaris Amid from Agilent, alternatively I am currently experimenting with a C4- phase from Phenomenex, because I want to convert our method from our ion trap to LC-Q-ToF and LC-Orbitrap.

The eluent was isocratically 90% methanol or acetonitrile, because larger amounts of water in the eluent caused considerable problems during the calibration.

I hope my answer is helpful for you.

Good luck and stay healthy

Joachim

Thanks for the info. Waters regional manager just visited us and we discussed few options. It seems that ELSD is a way to go. Our concentrations are relatively high (>0.1 wt)

Please look at the following below links which may help you in your analysis:

http://tools.thermofisher.com/content/sfs/posters/87422-PO-HPLC-Surfactant-Analysis-08July10-LPN2525-1.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147533/pdf/molecules-10-01179.pdf

https://www.tandfonline.com/doi/abs/10.1080/10826076.2012.683915

Thanks

Refractive Index Detector

Mario,

The problem with an RID detector is its lack of sensitivity. You would be 'lucky' to detect ~0.1%( wgt/wgt) or 1000 ppm. In addition it can not be used for gradient separations!

Kyril,

think about "reversed" detection by UV. i.e. you add a component to the eluent that have a high UV absorption. At the moement of peak elution the absorption will be lowered - reversing the signal you can get a chromatogram.

regards,

GB

Second option - think about ion-pairs formation.

If you will form an ion-pair with UV absorbing additive, you can easily detect your analytes. (Remember, that some ion-pair reagents can strongly modify the performance of your column).

regards,

GB

Thermo Scientific™ Acclaim™ Surfactant LC Columns equipped with ELSD or CAD detection can fix the problem. MS is also possible

Thanks, all. I read your suggestions carefully.

In general I support the suggestions of Grzegorz,. Moreover in Research Gate an excellent review of surfactant analysis with HPLC (and other techniques) is available. Look for a condensed overview to table 5 of this publication.

Chapter Analysis of Surfactants in Environmental Samples by Chromato...

If your concentrations are high enough and isocratic only methods will work, then RID may provide the least expensive and most reliable solution to detection. With derivatization, UV/VIS is another option and would allow use of your existing detector.

The compounds you reference, do indeed represent good applications for use with an ELSD (or CAD) detector. Tens of thousands of application notes can be found for similar compounds online, as examples (Google search). However, I would offer a word of caution when considering the use of these often problematic HPLC detectors. The sales teams that sell them may fail to provide a realistic overview of these niche instruments and their many problems.

ELSD and CAD are sometimes described incorrectly as "Universal" detectors. This is inaccurate and far from the truth (but products sell better when you exaggerate) ... Similar to a mass-spectrometer, proper operation of these specialized detectors requires a great deal of experience, time and skill as they are not for novice or intermediate level users. All mobile phases must be volatile. Samples should be non-volatile. Optimization of all detector heat, gas and flow settings on the ELSD/CAD must be carried out for each sample and each method, every time you use the system. This is not a UV/VIS 'turn-on and get a signal' type of detector. Reproducibility can be a problem, again, because the response will change over time from many things, including internal contamination, clogging, back-pressure ... They require a great deal of site-prep and equipment to use (i.e. they use very LARGE volumes of high-purity Nitrogen gas to run, need venting, and regular INTERNAL cleaning as the samples injected bake onto the inside of the detectors resulting in noise and contamination over time). Their output may be non-linear across ranges and can even require multiple types of curve fits for each sample type (so you will need a high quality CDS with many types of curve fit options including, n-polynomial, exponential, sigmoidal to name a few). As someone directly involved in their early design and commercial development, I would only recommend their use after other methods have been tried or ruled out, and again, only by experienced chromatographers who can accept their limitations.

For the right types of applications where an LC-MS system is unavailable, they have proven very useful. Example: "Advanced Evaporative Light-Scattering Detector (ELSD) For A Variety of HPLC Applications"; Conference Paper Advanced Evaporative Light-Scattering Detector (ELSD) For A ...

HPLC - ELSD is good for detection of surfactants.

CAD detectors may work well here. Although sometimes its not as straightforward as introducing the eluting compound into the detector. Sometimes it may be appropriate to use inverse gradients to avoid changes in detector response over a gradient method, which requires some adaptation of your equipment and methods.