Chromatography Forum

Dear all,

I am trying to use Dionex IC-5000 capilary ion chromatogrphy to detect glutamic acid. Our system can only run anion exchange with KOH elution, and with conductivity detector.

Somehow, I can not even see the peak for glutamic acid, even using the maxium possible elution condition the system allows (such as 0.1 mM-100mM KOH gredient, hold at 100mM KOH for 5 mins). I can run organic acids using the system with no problem. Above pH9, glutamic acid bears two negative charges (one for regular organic acid), but should be able to be eluted by 100mM KOH. Is it possible that suppressed conductivity detector can not detect glutamate?

Thank you in advance for all the inputs.

Howard

Dear all,

I am trying to use Dionex IC-5000 capilary ion chromatogrphy to detect glutamic acid. Our system can only run anion exchange with KOH elution, and with conductivity detector.

Somehow, I can not even see the peak for glutamic acid, even using the maxium possible elution condition the system allows (such as 0.1 mM-100mM KOH gredient, hold at 100mM KOH for 5 mins). I can run organic acids using the system with no problem. Above pH9, glutamic acid bears two negative charges (one for regular organic acid), but should be able to be eluted by 100mM KOH. Is it possible that suppressed conductivity detector can not detect glutamate?

Thank you in advance for all the inputs.

Howard

I am suspecting that the conductivity of protonated glutamic acid is quite small. Keep in mind that after suppression you just have glutamic acid in pure water. I don't have the physical data for the acid. Also some organic acids can pass through suppressor membranes.