Amperometry or coulometric EC continue

[Xinji Li]

My HPLC-ECD is Amperometric cell and I used it for analysis catecholamines in Microdialysis sample or Plasma
sample. Calibration method I used is based on ESA company methodology book. That book say that his single point calibration for catecholamine in plasma is from the coulometry detector. I think there is no big difference between Amperometric cell and couplometric cell . Am I right? who can tell me that using ESA methodology book and its single point calibration method for catecholamine in plasma is OK or has some problem? Thanks to answer, Sincerely

[Markus Laeubli, Metrohm]

The amperometric cell (Thin-Layer or Wall-Jet type) usually have approximately 5 - 10% of turnover. This conversion factor is constant under specific conditions but may differ with different conditions.
The coulometric cell is said be have 100% conversion (I do not have experience on that). If the conversion is really 100% over the full concentration range then theoretically a single point calibration might be enough. But proving this might be time consuming anyway.

By the way usually the coulometric cells do not show lower decection limits as the noise in creases with conversion factor.