Xiaohua Huang

ANALYSIS OF FACTORS CAUSING PEAK BROADENING IN CAPILLARY ZONE ELECTROPHORESIS

Abstract An equation analogous to the Van Deemter equation in chromatography is developed to account for peak broadening in capillary zone electrophoresis (CZE). This equation applies to conditions wher the peaks are symmetrical (sample zone concentration much less than background electrolyte concentration). To identify and to quantitate the effects of different contributions to the peak width in CZE, it is first necessary to put all peak profiles on the same footing by correcting them for the velocities fo different zones and for the finite length of the detector zone compared to the sample zone. Three major contributors to the peak width are identified: (1) the injection length of the sample; (2) longtudinal diffusion that takes place during the migration time between injection and detection; and (3) analyte-wall interactions. Temperature is shown not to be a major factor in peak broadening under typical experimental conditions. The predictions of our model agree well with experimentally determined peak profiles for different analytes under a variety of conditions. New expressions for theoretical plate number and resolution in CZE are presented. It is concluded that in almost all previously reported CZE separations the peak profiles were dominated by the sample injection length. This explains why the observed peak widths in CZE have been broader than anticipated.

Determination of metal ion complexes in electroplating solutions using capillary zone electrophoresis with uv detection

Abstract Capillary zone electrophoresis with on-column UV detection at 214 nm was used to detect and determine iron cyanide complexes in liquid samples from zinc electroplating processes. Using a cathodic injection and anodic detection scheme, hexacyanoferrate(II) and -(III) ions were separated with separated with baseline resolution in under 5 min. A linear relationship between peak area and concentration was obtained for both ions, and the detection limit was lower than 10 μM. The experiments were extended to detect the presence of zinc hydroxo complexes in plating solutions. The electrophoretic mobility of this species was determined from the migration times, sampling simultaneously the zinc species at the cathode and adenosine, a neutral molecule that migrates with the electroosmotic flow, at the anode. The results seem to indicate the rpesence of the doubly charged species Zn(OH)2−4 in Zn11 solutions at pH > 10.5.

Effect of electrolyte and sample concentraton on the relatioship between sensitivity and resolution in capillary zone electrophoresis using conductivity detection

Abstract By maintaining the same ratio of ion analyte concentration to background electrolyte concentration while diluting the latter, it is shown to be possibble to increase substantially the detection sensitivity without altering the resolution in capillary zone eletrophorectic separations with on-line conductivity detection. Using a mixture of carboxylic acids, the limits of detection are extended to 10−6M.

Quantitation of Li+ in serum by capillary zone electrophoresis with an on-column conductivity detector

5-81. In general, flame emission photometry is more sensitive for lithium determinations than atomic absorption spectroscopy, but is also the less precise of the two methods. In addition, there is some spectral inter- ference from other ions, in particular Na+ and K+, in these procedures

Continuous sample collection in capillary zone electrophoresis by coupling the outlet of a capillary to a moving surface

Use of an on-column frit structure, constructed by sintering a mixture of glass powders, makes it possible to ground a fused-silica capillary on its side prior to its outlet. Electroosmotic pressure permits convenient sample collection. We illustrate the use of this device by depositing the eluent in a continuous manner on a moving surface. This provides a permanent record of the separated species in a mixture.