Nonionic surfactant enhanced semipermanent coatings for capillary electrophoresis of inorganic anions without use of organic additives

Abstract

Separation of inorganic anions by capillary electrophoresis (CE) is usually conducted in co-electroosmotic mode due to the large electrophoretic mobilities of inorganic anions. Semipermanent surfactant coatings have been shown to be effective for CE of inorganic anions due to their strong capability of electroosmotic flow (EOF) manipulation. However, semipermanent coatings often suffer from their unsatisfactory stability. In addition, organic solvent additives are usually required to adjust the selectivity, which also aggravate the degradation of coating. In this work, a novel semipermanent coating consisting of cationic Gemini surfactant 18-10-18 and nonionic surfactant Tween 20 was developed to separate inorganic anions in CE. This coating is easy to prepare and more stable than pure Gemini coating. The introduction of nonionic surfactant in the coating not only suppresses the reversed EOF but can also adjust the selectivity of separation. Good separations of six model anions were achieved, the separation efficiency was as high as 65040-169700 plates/m and the RSDs of the migration times were less than 0.5 and 2.5% for run-to-run and day-to-day assays, respectively. Calibration curves were linear in the range of 0.05-5.0 mM; the detection limits ranged from 20 to 50 μM. More importantly, no organic solvents are required in the background buffer to achieve the satisfactory separations. This guarantees the coating stability and makes the method greener than most of other methods for CE of inorganic anions.

New peak broadening parameter for the characterization of separation capability in capillary electrophoresis

“…In CE, the dispersion of the electrophoretic zone and the influence of different separation conditions on the zone broadening are usually estimated by the separation efficiency expressed in the theoretical plate number or the height equivalent to the theoretical plate . Among these conditions, the influence of Joule heating in CE and in nonaqueous capillary electrophoresis (NACE) , capillary diameter , electroosmotic , hydrodynamic and hydrostatic flow velocities, chiral selectors , and capillary coatings were studied. The relation of the plate number to the diffusion coefficient and the ionic mobility with the EOF and without it , as well as the main reason for lower plate numbers in NACE , the influence of solvent properties in NACE–MS of basic analytes , and the influence of the construction of microfluidic separation devices on the peak broadening were also discussed.…”

Element Speciation Analysis Using Capillary Electrophoresis: Twenty Years of Development and Applications

“…An alternative possibility is to use the EOF modifiers not by adding them to the electrolyte but rather by conditioning the capillary with a surfactant/polymer solution in a number of ways. This methodology can be used prior to each run, ,,, after a number of runs, , such as every 10–100 analyses or even longer, , or by combining an overnight flushing with the addition of a polymer to the electrolyte . In each of these cases, the modifier dynamically or semipermanently covers the inner surface of the capillary and changes its charge from negative to positive.…”