ESA Biosciences, Inc. is a global supplier of analytical instruments and kits for the biomedical research, drug discovery and clinical diagnostic markets. ESA is leading the way in life science and diagnostic research through the use of superior separations with high sensitivity detection that improve the quality of health care. The company provides specialized LC components, innovative software products, advanced detectors, accessories, pre-prepared reagents, expert technical assistance and analysis services.
ECD (Electrochemical Detection) is the acknowledged standard for highly sensitive and selective detection in high performance liquid chromatography (HPLC).
Coulochem® III Electrochemical Detection Platform
To readily quantify picogram to femtogram levels of oxidizable or reducible compounds in a sample, an ECD is the HPLC detector of choice. Of all the detectors used with HPLC, not one is as sensitive, selective and with as wide a dynamic range as an electrochemical detector.
Coulochem's integrated Organizer module is designed to save bench space and provide a protected environment for columns and cells.
The Coulochem III is compatible with all current ESA sensors and will be the platform for future sensor developments.
The Coulochem III detector relies upon the electroactive nature of molecules that can be either oxidized or reduced. Although fluorescence or UV detection may readily measure many of these compounds, liquid chromatography combined with electrochemical detection provides a more sensitive and selective alternative
Coulochem III Highlights
- Both Coulometric and Amperometric detection
- Available with DC and/or Pulse/Scan modes(or both)
- Compatible with all HPLC columns(Normal to Capillary)
- More than 2 times less electronic noise than an ESA 5200A
CoulArray® with Your HPLC system
Simplifying Complex Analytical Problems
You may already have part of a Coulometric array system. It's your HPLC. Add the CoulArray detector and you have a uniquely powerful, cost-effective system for even your most challenging analytical tasks.
With the CoulArray detector, you can generate comprehensive data from a single sample. Measurements of compounds can easily be performed over six orders of magnitude in concentration, even in the presence of co-eluting analytes or matrix effects.
Quality Control, Drug Discovery, Drug Stability, Determination of Physiological Activity
Pharmaceutical - From quality control to drug discovery, the inherent sensitivity and selectivity of the CoulArray enable measurement of vanishingly small quantities of pharmaceuticals and their metabolites, even in complex samples. Applications include novel drugs discovery in natural products, assessment of drug stability and determination of physiological activity.
Food and Natural Products - The CoulArray's ability to measure low levels of non-volatile flavonoids and phenolics can provide a competitive advantage by profiling the characteristic qualities of products, determining their integrity and evaluating competitors' products.
Neuroscience - The measurement of neurotransmitters, simultaneous monoamines, and amino acids are just some of the examples of the neuroscience applications of the CoulArray.
Environmental - Analysis in the environmental lab is enhanced by the ability to screen for a large number of compounds, such as pesticides and herbicides, where the allowable limits are below those readily measurable by other analytical techniques. In addition, the analysis of low levels of explosive compounds is becoming increasingly important in site characterization projects.
Areas of Research - Coulometric Array Technology
- Toxicology
- Cancer Research
- Forensics
- Oxidative Metabolism
The Coulometric Electrode
The cells for commercially available electrochemical detectors (ECDs) for HPLC usually consist of three electrodes, the working, counter and reference electrodes. These electrodes can be aligned in several different geometries. Most ECDs can be divided into one of three basic designs based upon how the eluent from the chromatographic column impinges upon the working electrode's surface.
Electrode Efficiency, Sensitivity and Stability
Amperometric "thin-layer" working electrodes typically oxidize (or reduce) <10% of an electrochemically reactive species passing over them. This level of efficiency is a direct consequence of two factors. First, there is limited diffusion to the working electrode's surface, where reactions occur. This means that a molecule has to be in "the right place at the right time" if it is going to react and be measured. Second, at the typical flow rates used in HPLC most molecules will be swept through the detector without the possibility of reacting at the working electrode's surface. Consequently, the signal obtained from amperometric sensors is notoriously dependent upon the flow rate. Coulometric electrodes typically oxidize (or reduce) up to 100% of an electrochemically reactive species passing through them. This extreme efficiency is a direct consequence of minimizing the diffusion distance so that regardless of the direction in which a molecule diffuses, once it is in the electrode matrix, it is bound to encounter the working electrode's surface and react. Consequently, the signal obtained from a coulometric sensor is independent of the flow rates typically used in HPLC.
Selectivity
Another advantage of the coulometric electrode is the enhanced selectivity observed when two or more of these electrodes are placed in series. Because the coulometric electrode measures signal from 100% of an analyte undergoing electrolysis none of the analyte is left to react at subsequent downstream electrodes. Consequently, if two compounds are unresolved chromatographically then, as long as their half-wave potentials differ by as little as 60mV, they can be resolved voltammetrically. Thin-layer amperometric electrodes cannot be used in this fashion as unreacted analyte would spill over onto subsequent electrodes thereby ruining any voltammetric resolution.
