Ask Dr. Bruce

The ESA resident expert on the optimal use of electrochemical detectors in bioanalytical separations, Dr. Bruce Bailey (Dr. Bruce to our customers) is widely published with many years of experience in the field. As Manager of ESA Applications, he has supported hundreds of ESA customers. You'll meet him in more detail in the next issue of Femtogram. "Ask Dr. Bruce" offers practical troubleshooting and advice to help keep your electrochemical system operating at peak efficiency. Today's column focuses on "Decreased Sensitivity in Electrochemical Detection and what to do about it.

One of the key issues that everyone performing electrochemical detection faces is problems with decreased sensitivity as their ECD system is operating routinely. Some of this may be due to the electrochemical cells themselves and their detection surface, while other issues can arise from the nature of the mobile phase and/or samples being studied. Here is a tip to help manage common issues associated with decreased sensitivity from an electrochemical system:

Improve your mobile phase quality
The water used to make up the mobile phase is often the culprit for many poor sensitivity problems caused by increased noise and background signal. While everyone uses "HPLC grade" water for their analysis, this type of cleanliness is appropriate to UV detection, and may not necessarily be ECD compatible. ECD often operates at ppm levels of sensitivity, and electroactive impurities of as little as .001% can cause a significant problem in your analysis. To ensure that the water you are using for your EC analysis is of sufficient quality, we highly recommend that you follow the water "polishing" procedure outlined in ESA Technical Note 70-1668 to generate water of sufficient quality for ECD. It only takes a few minutes, but a little effort up front can save you a lot of headaches later.

We'll cover more issues related to electrochemical system sensitivity in our next issue. Until then, see ESA Technical Notes 70-4821 and 70-6346 for more helpful suggestions on managing your mobile phase quality.