What is electrochemical detection and what are its applications?
Electrochemical detection (ECD) for HPLC or UHPLC / UPLC is an extremely selective and sensitive detection technique that is applied in several analyses such as the neurotransmitters dopamine, serotonin and noradrenalin, or analytes such as 5HIAA, catecholamines and metanephrines. ECD has an enormous linear dynamic range of more than 6 orders of magnitude. This means that concentrations can be measured as low as 50 pmole/L and as high as 100 µmol/L or more.
What is the detection principle?
In Amperometric electrochemical detection the electrical current is measured resulting from oxidation or reduction reactions (Fig. 1). A sample is introduced in HPLC and separated on the chromatographic column. The column is connected to an ECD flow cell, an electrochemical sensor where a reaction takes place at an electrode. Electrochemically active substances elute as separate bands from the column and undergo an electrochemical reaction, either receiving electrons (reduction) or gaining electrons (oxidation). The electrodes are constantly supplied with a fixed voltage. When a redox reactions occurs on them, this pico or nano ampere change is converted by the instrument circuity into a readable signal.
Fig. 1. HPLC with Amperometric electrochemical detection.
How does the HPLC acquisition work, and how does the chromatography analysis work?
The detector is connected to a computer where the data is collected and stored in data acquisition software. The resulting chromatogram (fig. 2) shows the detector response and is used for identification and quantification of analytes. Using calibration standards, the signal height (current, in nA) is related to concentration and the retention time identifies a substance. For example, if a known 1 ug/mL internal standard has a peak height of 100,000, we know that a peak height of 50,000 is 0.5 ug/mL for the same chemical.
Verulam Scientific offer the data acquisition and hardware control software “Clarity” by DataApex. It can control up to four independent chromatography systems at a time and has available connection methods to the majority of HPLC systems.
Fig. 2. A chromatogram with calibration standards of several neurotransmitters
What can Verulam Scientific can offer?
We can offer everything from standalone electrochemical detectors, to entire HPLC systems with an electrochemical detector attached. We also offer installation and service contract cover for your instruments. We understand the growing use of electrochemical detection of 5HIAA, HVA, Dopamine, 5-HT and other clinical analytes and are here to offer you ready to go solutions with or without software which cater you any needs you may have.
Verulam Scientific is the exclusive UK Partner for Antec Scientific , a world leading supplier of Analysers based on (U)HPLC with Electrochemical Detection (ECD) and Potentiostats for electrochemical reactions upfront MS. The ALEXYS™ (U)HPLC / ECD Analyzers and the ROXY™ Electrochemistry (EC) Systems for EC / MS are known for their superior performance and unique features.