By Anonymous on Wednesday, April 28, 2004 - 12:42 am:
I have Problems with my ecd working elektrode
it is an amphotheric glassy carbon elektrode and when I tried to clean it I destroyed it a little bit now I have scratches on it
I would like to know how to remove them and what influence they have on detection
My second question is what influence it has making the cell smaler by using a thinner gasket
By Petr Jandik on Friday, April 30, 2004 - 06:48 pm:
First question: Please first determine whether the scratches are significant enough to affect detection response. If the scratches are big enough to cause leaking, then you can stop right there.
If the cell appears to be not leaking, inject a blank. Compare the quality of the baseline with chromatograms you may have obtained while the electrode was still unscratched. You may have already done all that and there are either leaks or a significant increase in noise.
Most instrument makers supply polishing powders with a detailed description how to apply them to working electrodes. Many times they supply two grades, usually described as “coarse (larger particles)” and “fine (smaller particles).” You will also need a suitable polishing pad.
Polish your electrode with coarse powder first and then with the fine one (always add water to the powder). Use a new pad for each type of polishing powder. After each polishing step, rub the working electrode on another fresh piece of wet polishing pad to remove particles of polishing powder embedded in the glassy carbon material. If the scratches are still there and causing leaks and/or noisy baselines, use a piece of sand paper (600-grit) and then repeat the coarse and fine polishing steps.
Second question: Thinner gaskets (with everything else unchanged) are increasing the sensitivity of detection. However, thinner gaskets also lower the upper limit of linearity. The sensitivity increase thus comes at a price of a narrower range of linearity. For the same reason, people sometime use thicker gaskets to expand the range of linearity to higher values. In doing so they are sacrificing the sensitivity in order to have a linear calibration curve at higher concentrations.