Chromatography Forum

We are having problems with ELSD signal response reproducibility - possibly caused by baseline noise. On reading a guide to ELSDs, it is my understanding that all solvent should be evaporated, and therefore the amount of waste solvent fairly minimal. We have noticed that the amount of waste solvent is approx. the same as the amount used to run the samples. Does this suggest inefficient nebulisation, and therefore a fault with the nebuliser? Or is it usual for most/all of the nebulised solvent to be recondensed? Any help would be much appreciated.

On reading a guide to ELSDs, it is my understanding that all solvent should be evaporated, and therefore the amount of waste solvent fairly minimal. We have noticed that the amount of waste solvent is approx. the same as the amount used to run the samples. Does this suggest inefficient nebulisation, and therefore a fault with the nebuliser? Or is it usual for most/all of the nebulised solvent to be recondensed?

OK, I'm retired now, used 3 different ELSD units in my career. I can't claim to be an expert in ELSD, just an experienced user.

No, the amount of condensate for us was considerably less than the mobile phase volume, always. The more aqueous the mobile phase, typically the higher the ELSD nebulizer temperature. We used nitrogen at about 2 liters per minute.

Have you tried higher ELSD temperature like 50 C higher, to see if performance was better, worse, or the same?

User of a recent Agilent ELSD here. Modern ELSDs run on lower spray chamber temperatures and sample a small part of the nebulized eluent, so it MIGHT be OK if you see a lot of condense. It depends on the eluent composition and ELSD model.