electrochemical detection

[rolf]

Hi,

is anybody familiar with the Antec, Leyden glassycarbon WE, ISAAC cell?

I would appreciate any support. I have to assess VMA, HVA and 5-HIAA in urine with a commercialy available kit.

I register a relativly high cell current and low sensitivity. It is a brand new electrode, so altering after prolonged use cannot be the reason for this.

Thanks.
Rolf

[tom jupille]

It's been a long time since I worked with electrochemical detectors, but do they have a recommended "cleaning" protocol (voltage cycle to get rid of crud on the electrode)? Just because it's new doesn't mean it isn't contaminated.

[Rafael Chust]

Some years ago, when I installed a Waters 460 EC detector, I experienced the same problem... and follow what Tom said and, voilá, problem solved!

In fact, we never know the conditions the electrode has passed and it is possible to be contaminated - well, mine was!

[Mark Tracy]

Also, check the reference electrode and make sure it is on specification, otherwise your working potential will be wrong. Also check your literature method and see if the reference electrode is the same type as yours.

[Jeff Brewer]

In regards to Antec Leyden flow cell may I suggest visiting the Antec Leyden Website, under products select flow cell and at the bottom is the ISAAC. The website says 2mM/L chloride is required to be added to the mobile phase which may be a problem depending on your mobile phase.

Additionally, I suggest taking the cell apart. With a damp paper towel wipe the surface of the GC electrode to remove any film which may have appeared on the surface. Reassemble the cell, slowly pump mobile phase through the cell to remove any air bubbles. When you are convinced the air bubbles are removed add sufficient back pressure to maintain a positive pressure on the cell to keep air bubbles from forming in the cell. Also check your connections.

If this fails to resolve the problem I suggest contacting Antec Leyden Customer Support. I hope this info has been helpful.

Sincerely,
Jeff Brewer
Metrohm-Peak

[rolf]

Many thanks for your suggestions to solve my problem.
I do hope to be successful.

By the way, Jeff, I conducted the Antec, Leyden customer service, but for some reason - no support at all!!! I cannot understand this.

Once again, thank you all.

Rolf

[Jeff Brewer]

Dear Rolf:

I am sorry you have had no direct contact with Antec Leyden. This is a really good company to work with and their response to me in the past has been excellent. I have sent an email to my contact at Antec Leyden suggesting they contact you through this forum since I do not know how to suggest otherwise.

I truly wish this situation is resolved for you quickly.

Best regards,
Jeff

[rolf]

Dear Jeff,
Thank you very much for your efforts.

I did all the polishing of the WE and the ISAAC-Ref as well.
Now I have to wait for stabilizing the system - and for success! I do hope it will work.

Once again, I appreciate your support very much.

Happy easter,
Rolf

[balsanek]

Dear Rolf,

GBC Scientific Equipment is the exclusive distributer of Antec Leyden products in the US. I recieved word by Antec via Jeff Brewer that questions involving the Antec detectors were posted at this forum. I see Jeff gave you some good advice, but would like to hear if you are still having problems. Please feel free to contact me.

Regards,
Bill Balsanek

[rolf]

Dear Bill,

thanks for replying.

Yes , I still have problems with my ECD. The sensitivity is very low, the peaks are tiny. I have problems with the data processing.

I do over ten years HPLC-ECD (catecholamines in plasma and urine) with the standard salt-bridge Ag/AgCl - electrode and had few problems.
Now I received a new Waters HPLC with the ISAAC-reference electrode. The detector is a Waters 2465. The cell potential is 850 mV
The cell current is about 10 nA. I also gave 20 mmol KCl to the mobile phase as recommended.
I use a commercial kit to determine VMA, HIAA and HVA in human urine.

Do you see room for improvement. Any help will be appreciate.

Thank you.

Regards,
Rolf

[AA]

When moving from a traditional salt bridge electrode to the ISSAC electrode, the working potential will need to be adjusted. Check on page 50-51 of ypur 2465 users guide to determine how to calculate the new potential.