High-voltage capacitively coupled contactless conductivity detection for microchip capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Separation Science

Background:

• Traditional conductivity detection in electrophoresis often requires direct contact with the separation medium, limiting versatility.
• Contactless detection methods offer advantages in sample handling and device longevity.
• Capacitive coupling presents a promising approach for non-invasive electrochemical sensing.

Purpose of the Study:

• To develop and validate a contactless conductivity detection system for planar electrophoresis.
• To assess the sensitivity and applicability of the method for diverse analytes.
• To demonstrate the universal nature of the developed detection technique.

Main Methods:

• Utilizing capacitive coupling with AC excitation voltage (500 Vp-p, 100 kHz) for contactless conductivity detection.
• Implementing the detection through a 1 mm cover plate and optimizing sensitivity via electrode trough placement.
• Applying the method to analyze inorganic ions (K+, Na+, Mg2+), heavy metals (Mn2+, Zn2+, Cr3+), organic acids, and pharmaceutical compounds.

Main Results:

• Achieved signal-to-noise ratio (S/N) detection limits as low as 0.35 µM for inorganic ions.
• Demonstrated detection of heavy metals with limits ranging from 2.1 to 6.8 µM.
• Successfully detected organic acids (citric, lactic) and anti-inflammatory drugs (4-acetamidophenol, ibuprofen, salicylic acid).

Conclusions:

• Contactless conductivity detection via capacitive coupling is a viable and sensitive method for planar electrophoresis.
• The technique exhibits broad applicability across inorganic, organic, and pharmaceutical analytes.
• This universal detection approach holds significant potential for various analytical applications, including food, beverage, and pharmaceutical analysis.