A low-cost light-emitting diode induced fluorescence detector for capillary electrophoresis based on an orthogonal optical arrangement

In this work, a simple and low-cost miniaturized light-emitting diode induced fluorescence (LED-IF) detector based on an orthogonal optical arrangement for capillary electrophoresis (CE) was developed, using a blue concave light-emitting diode (LED) as excitation source and a photodiode as photodetector. A lens obtained from a waste DVD-ROM was used to focus the LED light beam into an ∼80 μm spot. Fluorescence was collected with an ocular obtained from a pen microscope at 45° angle, and passed through a band-pass filter to a photodiode detector. The performance of the LED-IF detector was demonstrated in CE separations using sodium fluorescein and fluorescein isothiocyanate (FITC)-labeled amino acids as model samples. The limit of detection for sodium fluorescein was 0.92 μM with a signal-to-noise ratio (S/N) of 3. The total cost of the LED-IF detector was less than $ 50.