A Miniaturized Liquid Core Waveguide-Capillary Electrophoresis System with Flow Injection Sample Introduction and Fluorometric Detection Using Light-Emitting Diodes

Abstract

A novel miniaturized capillary electrophoresis (CE) system is described where a Teflon AF-coated silica capillary serves both as the separation channel and as a transversely illuminated liquid core waveguide. This device uniquely uses flow injection (FI)-based split-flow sample introduction through a falling-drop interface. An H-channel structure fixed on a microscope glass slide utilizes a horizontal separation capillary with tubular sidearms on each end that serve as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functions as a falling-drop interface for coupling to the FI system. A blue LED is used as excitation source. A large-core optical fiber takes the emitted fluorescence to an inexpensive PMT with two layers of green plastic used for optical filtering. No focusing arrangement is needed. Continuous FI introduction of a series of 30-microL samples containing a mixture of of fluorescein isothiocyanate (FITC)-labeled amino acids allowed a throughput rate up to 144 samples/ h, with approximately 2% carryover and good precision (3.2% RSD). Baseline separation was achieved for FITC-labeled arginine, phenylalanine, glycine, and FITC in sodium tetraborate buffer (pH 9.5) with plate heights of 5.4-5.5 microm and plate numbers of 2.34 x 10(4)-2.37 x 10(4) under electrical field strengths of 214 V/cm for injection and 500 V/cm for separation (14-cm capillary, 48-microm i.d.). Detection limits (S/N = 3) were 1.3 microM for arginine and 1.9 microM for phenylalanine and glycine.

On‐column conductivity detection in capillary‐chip electrophoresis

“…Equations (5) and (6) are in correct agreement with the simulated responses illustrated in Fig. 6b, when including the simulated baseline of 3.97 V instead of 4 V due to the enlargement of the current lines at the side channels levels (0.4% difference on the voltage "peak" between Eq.…”

“…The use of small light source such as semiconductor diode laser and light-emitting diode (LED) made the detection system more compact [5]. Introduction of liquid core waveguides simplified the optics even further [6]. Electrochemical detection, on the other hand, is also a sensitive detection method that requires a less sophisticated instrumentation and that is very amenable to miniaturization and high throughput measurements.…”

Noise analysis and measurement of integrator-based sensor interface circuits for fluorescence detection in lab-on-a-chip applications

“…Others illuminate the microfluidics orthogonal to the detector, reducing the LCE E to 0.3-5% [13,16,18,48,49,50] with either the use of waveguides or using focused excitation. Chediak et al…”

Portable capillary-based (non-chip) capillary electrophoresis

“…The wavelength range available covers almost the whole spectrum from near IR [125] down to 405 nrn [126] and 375 nm [127]. As smaller dimensions of the device can be reached when employing LEDs and LDs as excitation light sources, the possibility of incorporation into the P-CE designs increases [128][129][130]. Other types of OD have been described.…”