FemtoGram

Bruce Bailey – from Ontario, Canada, to ESA!

Dr. Bruce Bailey (Bruce to the hundreds of customers he's supported through the years) is ESA's resident expert on the optimal use of ESA electrochemical detectors in bioanalytical separations. It all started many years ago. Bruce, while at the University of Waterloo, began developing new methods for neurotransmitter analysis using the first ESA Coulochem instrument (model 5100A) sold into the Canadian market. After stops in a contract research organization and with a competitor (Princeton Applied Research), Bruce found his home at ESA as manager of the applications group. Bruce's most recent accomplishments include the impressive method-development work behind ESA's two new neuroscience applications. In addition, Bruce is the impetus behind the new ESA HPLC School - unique in its full-day focus on electrochemical detection. To date, more than 50 customers have participated.

At ESA, we are successful when we help our customers be successful. Bruce is just one of the many professionals available at ESA Biosciences to ensure that your systems are operating at peak performance and to provide you with expert technical and applications support.

In order to maximize response, it is important to minimize noise - or more accurately - minimize background currents. High background currents primarily result from contaminants in the mobile phase. Too often, the source is the major component of most EC-compatible reversed-phase mobile phases - water! Only use fresh 18.2 megohm-cm water. Never-ever used stored water, which can grow micro-organisms that may produce EC-active contaminants that not only adversely affect noise, but can also build up on your analytical column and cause base-line perturbations and ghost peaks in the chromatogram! Interestingly, micro-organisms can also grow in the sinker (filter) and plastic lines from mobile phase reservoir to pump. If either sinker or line appears to be tinged green -you have a problem! Replace immediately.

Another major source of background current comes from the chemicals used to prepare the mobile phase. When purchasing dry chemicals for mobile phase preparation, make the selection based on two important criteria: 1) chemical purity - use the highest grade possible; 2) level of heavy metal and transition metal contamination- always avoid those reagents that report % contamination.

Since ECDs typically measure analytes at the ppb-ppt levels, impurities such as heavy metals and especially redox-active transition metals (e.g., iron, copper and nickel) not only influence the background currents at the electrochemical sensor, but also may lead to auto-oxidation and loss of labile compounds (e.g., catecholamines, serotonin, CoQ10, and thiols). The latter is often manifested as a loss of response at low levels, non-linear behavior of the analyte, and the possible appearance of ghost peaks in the chromatogram.

The quality of organic modifiers (e.g., methanol, acetonitrile, isopropanol) is also important. Quality may vary significantly from vendor to vendor. Like when choosing salts (above), make sure you select the purest reagent possible. Do not assume that a solvent that works well for UV detectors will work equally well for ECD. Read the label!

You should always use buffered mobile phases with ECD. Make sure that the chemical used (acid or base) to adjust the final pH is also chemically pure and devoid of transition metal contamination. For example, when making this solution more basic we recommend the use of semiconductor grade (99.99%) sodium hydroxide.

Ask Dr. Bruce