Interface for Coupling Capillary Electrophoresis to Inductively Coupled Plasma and On-Column Concentration Technique

Abstract

A new interface for coupling capillary electrophoresis (CE) to inductively coupled plasma (ICP) was developed. The interface was built outside and independent of the nebulizer and could be easily connected with a microconcentric nebulizer (MCN) as well as conventional pneumatic nebulizers. An on-column concentration technique was used to increase the sensitivity and to enhance the resolution of the system of capillary electrophoresis−inductively coupled plasma atomic emission spectrometry (CE−ICP-AES). By doing this, it was possible to analyze 1 μg/mL of total chromium (prepared with K₂Cr₂O₇ and CrCl₃) and 1 μg/mL of copper consisting of Cu²⁺ and Cu(EDTA)^2- with good spectroscopic intensity and efficient separation. Detection limits of 18 elements for MCN−ICP-AES coupled with CE were assessed by continuous sample introduction without applying high voltage and were found to be 1−4 times higher than those typically obtained by using MCN−ICP-AES for elemental analysis (without connection to the CE interface). When the on-column concentration technique was used, the sensitivities and separations were further improved by increasing the amount of sample. A simple electrolyte (0.05 M HNO₃) and a large inner diameter capillary (150 μm) could also be used to attain efficient separation.