Dionex ED40 Electrochemical Detector

The ED40 Electrochemical Detector measures current resulting from the application of potential (voltage) across electrodes in flowthrough cells. Depending on the method by which the potential is applied and the current measured, several different properties of the flowing solution can be determined. These measurements help answer the major questions analytical chemists ask: What’s in it, and how much is there?
Of course, other detectors are used in high performance liquid chromatography (HPLC). The UV-visible absorbance detector dominates all other forms of detection. Sensitivity is excellent for many analytes, especially aromatic species, and transparent mobile phases are readily available. However, there are numerous analytes that have very poor absorbance and are not detected with sufficient sensitivity by UV absorbance. Most of these nonchromophoric molecules are aliphatic organic molecules and inorganic ions. Low wavelength UV detection can be used, but at a loss in selectivity.
Refractive index detection can also be used. However, maintaining a stable baseline can be difficult, and RI detection is less sensitive and substantially less selective than UV detection.
Fortunately, a wide variety of nonchromophoric molecules can be detected with good or excellent sensitivity by one of several forms of electrochemical detection. These molecules include carboxylic, sulfonic and phosphonic acids; alcohols, glycols, aldehydes, and carbohydrates; primary, secondary, tertiary, and quaternary amines; sulfates, sulfoxides, thiols, sulfides, and mercaptans; and inorganic anions and cations. In addition, when compared to UV absorbance detection, electrochemical detection provides substantial improvements in sensitivity and selectivity for amine and hydroxy-substituted aromatics such as catecholamines.