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Optimization of Electrode Alignment for Electrochemical Detection in Capillary Electrophoresis Using a Scanning Electrochemical Microscope
Author(s) -
Roach David M.,
Hooper Stephanie E.,
Anderson Mark R.
Publication year - 2005
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200503368
Subject(s) - capillary action , capillary electrophoresis , electrode , microelectrode , analytical chemistry (journal) , capillary electrochromatography , working electrode , materials science , microscope , scanning electrochemical microscopy , capillary length , chemistry , electrochemistry , chromatography , optics , composite material , physics
Electrochemical detection in capillary electrophoresis requires decoupling the voltage applied to the working electrode from the separation voltage applied across the capillary. End‐capillary electrochemical detection achieves this by placing the electrode just outside the ground end of the separation capillary. Obtaining adequate signal‐to‐noise in this arrangement requires using small inner diameter capillaries. Decreasing the inner diameter of the separation capillary, however, increases the difficulty of aligning the microelectrode with the open end of the capillary. Using scanning electrochemical microscopy (SECM), the position of the capillary opening is determined while electroactive material is continuously emerging from the end of the capillary. The SECM instrument is then used to place the electrode at the position of maximum current for subsequent separations. Subsequent measurements found that the best signal‐to‐noise is obtained when the detection electrode is placed directly opposite the capillary opening and just outside of the capillary opening. When the electrode is further above the opening (but still opposite the capillary opening), the signal‐to‐noise does not dramatically decrease until the electrode is more than 30 μm above the 10 μm inner‐diameter capillary.