Is there any difference between amperometric electrochemical detector and programmable electrochemical detector?
We have to perform the USP test for Azithromycin, there are two potentials to be applied, but..
In our programmable electrochemical detector when it is on Amperometry mode there is no such an option to set the second potential. If somebody has experience with ECD, please advise.
Thank you

Miro,

There are quite a variety of different modes of electrochemical detection. In simple DC Amperometry, a specific potential is set and output current is measured. In another common form, a series of potentials are programmed for specific time durations in a pre-programmed sequence (the potential sequence in this mode is often referred to as a waveform). In this mode of operation, only one of the operating potentials is used for measuring current with the remaining potentials being used for cleaning and conditioning of the electrode. In some detectors, a third mode is also possible where multiple potentials within the waveform can be separately tracked and processed together in a variety of ways. In addition, some detectors provide the option of applying independent potentials at multiple electrodes simultaneously, where each of the output currents from each of the electrodes can be acquired separately.

From the description you supply it would seem surprising if the detector you have is incapable of performing a programmed sequence of potentials(otherwise, what possible meaning could be attached to "programmable electrochemical detector"). Perhaps you have set the detector in the DC Amperometry mode (which is inherently a single potential measurement). Can you supply additional information about the detector in question?

It is HP 1049A. But Agilent don't provide dual glassy carbon electrode and there is nowhere to set two potentials.

Hello,
I work in an analytical laboratory. I have an Agilent 1100 HPLC system and I want to buy an electrochemical detector
Because I don’t have experience with ED and I don’t know very much about this method of detection, please help me by providing some information (1) about ED detection, in general and (2) about the producers of ED (ratio performance/price) [IF it is possible, I want my ED detector to be controlled /integrated in ChemStation]
I need this ED detector for analysis of pharmaceutical compounds from biological matrix.
(In a database with HPLC methods, I find that, for drugs/serum “coulometric” method is used more than “amperometric” ??; and the most ED used was from ESA ??)

Thank you very much
Tom W.

Pulse Amperiometric Detector (PAD) is the most popular mode. Used for sugars, sugar alcohols and alcohols etc.
Less expensive is the direct electrochemical detector (ECD. Though it can often do the job of simple applications like CN, Sulphide, Phenols and Catechols.
Both detectors can be purchased separately and can be fitted to most HPLC systems. Some applications may need PEEK throughout ... it will depend on what you are doing. Sugars + proteins in particular will need PEEK
Both detections mechanisms are simalar, except the PAD has a cleaning potential as discussed above. Direct ECD obviosly does not have a cleaning potential. But it is v cheap to buy.
Some appliations do not need the PAD cleaning potential.
Good manufacturers of electrochemical detectors to choose from are
ESA
Dionex
Metrohm
I found this reference. It may help you. good luck
Author[ Shepard,R.M. Duthu,G.S. Ferraina,R.A. Mullins,M.A.
Title[ High-performance liquid chromatographic assay with
electrochemical detection of azithromycin in serum and tissues.
Journal[ J.Chromatogr.
Year[ 1991 ] Volume[ 565 ]
Pages from[ 321 to [ 337
good luck

You are kindly requested to clarify the following point in Concorde ECD Operator's Guide:

In operator's manual page (11)"The In Situ Ag/AgCl reference electrode (ISAAC) requires 2 mmole/l chloride ions (KCl or NaCl) in the mobile phase .Add and equilibrate before installation of the ISAAC."
Is this mean that that I should add 2 mmole of KCl or NaCl for any mobile phase used in any analytical method such as Azithromycin monograph in USP?

Thanks.

Miro, you've received a lot of good information. I used an ECD for 7 years and I am very, very familiar with using them. Most newer ECDs perform pulsed amperometric detection (PAD) and amperometry (DC). Also, there are not a lot of manufacturers out there. ESA, BAS, Antec and Dionex are the ones to look for. Almost all others are OEMs of these. For instance, Antec allows many comapnies to put their name on their ECD.

You're going to be hard pressed to control a third party ECD with Chemstation. In addition, I would not buy an ECD from Agilent. It is not their strong suit. The smaller LC companies I've listed above focus and specialize in ECD. Go with one of them. The ECDs will simply output an analog signal that goes into your data station. They can be autozeroed with contact closures. Simple.

Amperometric and coulometric detection are both the same and different. In both, a fixed potential is applied and a current is read. This current is converted to the analog voltage that I mention above and you have a signal on your data station. The main difference between amperometric and coulometric is that the former is a "flow-by" cell design and the latter a "flow-through" cell design.

Contact ESA for more specifics.

When buying any piece of LC equipment:

Call the company and see how hard it is to get through to them on the phone

Meet your sales person

Meet your service person

Good luck