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The Dependence of the Sensitivity and Reliability of Contactless Conductivity Detection on the Wall Thickness of Electrophoretic Fused‐Silica Capillaries
Author(s) -
Tůma Petr,
Samcová Eva,
Štulík Karel
Publication year - 2009
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.200804398
Subject(s) - capillary action , analytical chemistry (journal) , electrolyte , conductivity , potassium , capillary electrophoresis , calibration curve , chemistry , thermal conductivity detector , detection limit , thin film , sodium , materials science , electrophoresis , chromatography , electrode , composite material , nanotechnology , organic chemistry , gas chromatography
A contactless conductivity detector (C 4 D) performance has been tested on a simple capillary electrophoretic separation in a standard fused‐silica capillary with an external diameter of 360 μm and in a thin‐walled capillary (an external diameter of 150 μm); the internal diameters of the two capillaries were identical, equal to 75 μm. Potassium and sodium ions have been separated in a morpholinoethanesulfonic acid/histidine background electrolyte (MES/His), over a wide range of its concentrations (0–100 mM). At low MES/His concentrations, the C 4 D response, obtained from the height of the potassium peak, is by 100 to 200 per cent higher for the thin‐walled capillary and the calibration dependences are linear, in contrast to the thick‐walled capillary. These differences between the two capillaries decrease with increasing MES/His concentration, the C 4 D response in the thin‐walled capillary is then higher by mere 20 per cent and the calibration dependences are linear in both the capillaries. The highest sensitivities have been obtained at a MES/His concentration of 50 mM, with LOD values for potassium ion of 2.0 and 2.6 μM, in the thin‐ and thick‐walled capillaries, respectively. The signal‐to‐noise ratios and the plate counts are generally similar for the two capillaries. It follows from the results that special thin‐walled capillaries can be advantageous when background electrolytes with very low conductivities must be employed.