I am doing RP-HPLC –ELSD but it gives noise and wavy baseline (image attached). Can anybody suggest a solution for this? Mobile phase is aqueous volatile amine solution (mobile phase A) and ACN (B). Proper degassing and filter through 0.45um was done. Since one month I am working on this. So far I have prepared mobile phase for five times. I have not seen this problem earlier. But now I am facing this problem.
Bobbles? Electra-magnetic apparatus around HPLC?
Is your mobile phase degassed? Very often noise is created by a small air bubble in the detector cell, they can be very hard to eliminate.
What about detector lamp, its expiration date? Please. check other discussions like https://www.researchgate.net/post/How_can_I_eliminate_baseline_noise_in_HPLC
https://www.researchgate.net/post/Why_am_I_getting_Baseline_noise_in_HPLC
Not bubbles or a lamp issue.
Well there are too many possible reasons to list here. Operation of an ELSD module (or CAD module) requires far more experience and skill (to obtain reliable results) than most users have. They are not 'universal' detectors and prone to all kinds of issues, especially when not maintained and cleaned on a regular basis. They are very sensitive to mobile phase purity, gas purity, temperature stability and often require non-linear curve fitting tools for quantitative analysis. For certain sample classes (i.e. fats, oils, lipids, polymers...), they are useful, especially when you do not have an LC/MS system available. BTW: Most people have never used them so will not be able to provide reliable guidance. The vendors who sell them prefer to not mention these facts too... not good for sales.
- You did not provide us with DETAILED HPLC conditions. These details matter for all questions regarding HPLC, but even more so for LC/MS, SFC or when an uncommon detector such as an ELSD or CAD is used. While I can see some of the ELSD settings in the attached image file, I am not aware of the flow rate, %composition of mobile phase, column, back-pressure and conditions you are running.
Now, let me jump right in with a practical suggestion which may assist you (based on designing and using ELSD/CAD type detectors since the late 1980's). IF your ELSD heat and gas settings are optimized on the detector; IF your mobile phase is fully volatile under the conditions it is being used; IF the ELSD is internally CLEAN and the flow rate you are using is not too high, THEN you may have an obstructed exhaust line or filter. *We normally connect the gas vapor exhaust outlet of these detectors to a liquid trap (often a flask with dbl hole stopper). This trap is then vented to a fume hood for obvious safety reasons. If and when the trap overflows or the exhaust line(s) fills with too much liquid, the resulting exhaust back-pressure causes a cyclic baseline response (similar to what you have). Seen it hundreds of times with these detectors and is something that requires regular monitoring.
"Generic" ELSD Optimization Tips:
http://www.chiralizer.com/uploads/8/9/7/7/89770565/elsd_optimization_procedure_evaporative_light_scattering_detector_hplc.pdf
Great! Good suggestions from William Letter, I follow the question, please, inform us of the progress.
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