Coulochem cells are unique in their design, employing the patented ESA flow-through porous graphite electrode. These low-volume analytical cells contain two working electrodes. The high surface area of each electrode results in 100% reaction of the electroactive compound. The first (screening) electrode can be used to eliminate potentially interfering compounds from subsequent detection at the second (analytical) electrode.
COULOMETRIC DUAL-ELECTRODE CELLS
Electrochemical selectivity is achieved by oxidizing or reducing many electroactive, undesirable or interfering compounds at the first electrode. Any compound with a reaction potential less than that of the compound of interest is then excluded from reacting at the analytical sensor. Additionally, many compounds can be readily oxidized and reduced in sequence. This reversal can be employed to affect even greater selectivity. For example, catecholamines are easily reversible. They may be oxidized at the first electrode and reduced at the second.
The Model 5010A Standard Analytical Cell provides excellent long-term stability and day-to-day reproducibility. The large surface area of the coulometric electrodes permits long periods of operation without a reduction in signal.
The Model 5011A High Sensitivity Analytical Cell is a unique combination of an enhanced response amperometric electrode (flow-through) with the screening capabilities of the coulometric electrode. This provides the highest sensitivity, selectivity and stability available in any EC detector.
Application Specific Coulometric Cells
In addition to the cells described above, the ESA Coulochem II Detector also has the following specialty cells available:
The Model 5014B Microdialysis Cell is specially designed coulometric cell optimized and tested to ensure performance in the analysis of in-vivo microdialysis perfusates.
COULOMETRIC SINGLE-ELECTRODE CELLS
The Model 5020 Guard Cell is designed to withstand high pressures. It has a single large porous graphite electrode which removes electroactive impurities from the mobile phase prior to the injector, column and analytical cell. This decreases background currents and reduces baseline noise. Only ESA can offer guard cell capability.
The Model 5021A Conditioning Cell provides a third electrode to add extra selectivity to the analysis and is optimized to minimize band spreading.
The Model 5030 Cell is a designed for low flow applications and is optimized to minimize band spreading at flow rates of 250 µL / min or less. This makes the cell ideal for incorporation into MS, MS-MS and LC-MS systems
AMPEROMETRIC ELECTROCHEMICAL CELLS
The Model 5040 Analytical Cell is an amperometric, thin film cell designed to be used with a variety of target electrode materials. This cell is especially useful for applications such as pulsed amperometric detection of carbohydrates and measurement of acetylcholine.
The Model 5041 Enhanced Microbore Analytical Cell is an extremely low volume, thin film amperometric cell which employs a choice of working electrode surfaces. This cell is designed to be used in microbore situations which require the ultimate in mass sensitivity. ESA's recent development of a glassy carbon in a ceramic target electrode has lead to the lowest detection limits of any commercially available electrochemical detector.
Amperometric Target Electrodes
Target electrodes for ESA Amperometric Electrochemical cells are available for use in different applications:
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Glassy Carbon
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Gold (Au)
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Platinum (Pt)
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Silver (Ag)
HPLC PUMPS AND AUTOSAMPLERS
ESA Model 582 Solvent Delivery Module pump
The HPLC Pump Optimized for Electrochemical Detection
- Dual Serial Pistons - provide low pulsation and greater seal life.
- Low Volume Piston Displacement - 10 µL per plunger stroke, gives a noise profile matched to electrochemical detector noise filtration.
- Flow Rate Range of 0.001 - 9.999 mL/minute - usable for microbore and analytical separations.
- Automatic Seal Wash - prolongs piston seal life for greater reliability.
- Enhancement Package - for reduced noise with electrochemical detection.
- Electronic Diagnostics - for easier maintenance.
- Improved Fluidics - made more reliable and easier to service
- High Gradient Accuracy and Precision - for greater reproducibility
Model 540 HPLC Autosampler
- Unique Injection System - a double needle system utilizing a stainless steel needle to penetrate the septum and then second needle for sample aspiration.
- Three Injection Modes - flushed loop, partial loop and microliter pick-up for excellent reproducibility and no sample loss when dealing with limited sample availability.
- Automated Derivatization and Diluting Capabilities - flexible formats for sample preparation.
- Peltier Sample Temperature Control - integral heating and cooling of the sample racks.
- Flexible Vial Format - supports a wide range of sample vial shapes and sizes.
- Automatic vial sensor system detects vial presence and size.
- Ideal for Microdialysis studies
Model 542 HPLC Autosampler
The Model 542 is a feature rich, cost effective autosampler for HPLC analysis
- Quick-release bio-compatible injection valve
- Integrated column oven
- Integrated sample tray cooling (optional)
- Injection system providing zero sample loss with limited sample volumes
- Multiple injection modes: flushed loop, partial loop and microliter pick-up
- Optional sample tray formats
- Sample dilution, mixing and derivatization capabilities
The Model 542 HPLC Autosampler is optimized for use with electrochemical detection and incorporates an integrated column oven. This compact sized unit offers many features found in other more expensive autosamplers. It incorporates three selectable injection modes: full loop, partial loopfill and microliter pick-up. Sample processing capabilities are provided for sample mixing, dilution and on-line derivatization.
The integrated column oven provides temperature control up to 60° C and keeps injector to column tubing connection length to a minimum. The fluidic pathway uses biocompatible (PEEK®) components. The quick-change injection valve simplifies change-over and minimizes down time. The standard sample tray capacity is 84 - 1.8 mL sample vials and 3 - 10 mL vial positions for wash and alternate reagents. The sample tray can be cooled (refrigerated) by the addition of optional factory installed temperature control capability.
