ELSD detector

[AA]

your sales rep doesnt sound like he/she knows much about ELSD. All ELSD (from all vendors) have the same limitations.

1: You can not use non-volitile buffers (ie no phosphate)
2: Non liniear stanadr curves (standard curves fit to a quadratic equation), not really a limitation, just the way it is
3: Limited sensitivity for volitile and semi-volitile compounds
4: Sensitivity negativly impacted be particulate in mobile phases and column bleed
5: Detector must be vented
6: Need a gas supply (most use nitrogen, some can run qiute nicely off of clean dry house air)
7: Destructive technique

Of course on the other hand, these detectors can detect compounds that can not otherwise be detected easily. Many, many people use these detecor every day without issue. You seem to be having trouble deciding what brand to buy, arrange to send these companies some sample or arrange for an on site demo, most vendors will be happy (mostly happy) to comply.

And finally to answer you question "Can this Sedex ELSD detector work for mobile phase with some aq. buffer or water, e.g. 55% buffer? "

If the buffer is volitile and the flow rate is within the range of the detector (most operate quite nicely at usual HPLC flow rates), then the answer is yes.

[Kostas Petritis]

Agree with AA,

Actually you can even do analysis with 100% water at 30 C or so...

[juddc]

Second Kostas and AA's comments.

Whatever you do, buy a known high quality machine and make sure you know that it'll do what you need it to do before you open the wallet. Post purchase support is critical as well. Ask around about how well any instrument you're considering is supported in the field as that can make all the difference. The purchase price is only part of the equation.

Data point: My Waters 2420 has required no non-scheduled service and it's been in regular use since May of 2006. I believe I've had to clean the nebulizer twice in that time and that took all of 15 minutes. It wasn't cheap and it may not be the most sensitive out there, but it's reliable, yields very consistent data from injection to injection (often peak area system suitability %RSD's are <2%), and does what I need it to do without difficulty, so I'm happy with it and would recommend one to anyone doing anything close to what I do.

[Sallybeetle]

I developed and validated a method for the Sedex 85LT ELSD using a 100% aqueous mobile phase (170mM TFA buffer in water) and ELSD at 60°C temp, 3.2 bar nitrogen, and normal (HPLC) nebulizer.

I also developed and validated a method for this ELSD using 97:3 97mM TFA buffer in water : methanol and ELSD at 60°C temp, 3.5 bar nitrogen, and normal (HPLC) nebulizer.

With the adjustable gain, noise, and temperature range capabilities of this ELSD, I do not see 'solvent' limitations. Other ELSD models do not necessarily have these adjustment capabilities.

BTW. What solvent wouldn't be vaporized at 85°C that can be run on HPLC? Also, I'm sure the sales person meant to say "ELSD temperature," not "column oven temperature."

Hope this helps.

[Kostas Petritis]

Actually I have also developed validated methods with the Sedex ELSD (see: Validation of an ion-interaction chromatographic analysis of underivatized amino acids in commercial preparation using evaporative light scattering detection K. Petritis, M. de Person, C. Elfakir, M. Dreux Chromatographia 60 (2004) 293-298.)

Back then, this was the first published validated method by using ELSD. I do not know what is the status now... Being able to validate with a particular detector is important and speaks of it's reproducibility over time. In my case, I did the same experiement at 2 years interval, and got similar results. Finally, I used a Sedex 55 for this, the newer models are better...

I also used the ELSD to make an evaluation of different volatile acids, bases and their combination at different concentrations. The study was done in order to identify volatile enough buffers that can be used for mass spectrometry but it works of course for the ELSD as well.

If interested here you are:

Volatility evaluation of mobile phase/electrolyte additives for mass spectrometry K. Petritis, C. Elfakir, M. Dreux LC-GC Europe 15 (2002) 98-102

[Kostas Petritis]

Actually I just learned that in addition to Shimatzu, Agilent also choose to OEM the Sedex 85 from Sedere which they now sell under G4218A model... They have also integrated it to Chemstation and EZChrom...