In this work, a new type of miniaturized fibre-coupled solid-state light source is demonstrated as an excitation source for fluorescence detection in capillary electrophoresis. It is based on a parabolically shaped micro-light emitting diode (μ-LED) array with a custom band-pass optical interference filter (IF) deposited at the back of the LED substrate. The GaN μ-LED array consisted of 270 individual μ-LED elements with a peak emission at 470 nm, each about 14 μm in diameter and operated as a single unit. Light was extracted through the transparent substrate material, and coupled to an optical fibre (OF, 400 μm in diameter, numerical aperture NA=0.37), to form an integrated μ-LED-IF-OF light source component. This packaged μ-LED-IF-OF light source emitted approximately 225 μW of optical power at a bias current of 20 mA. The bandpass IF filter was designed to reduce undesirable LED light emissions in the wavelength range above 490 nm. Devices with and without IF were compared in terms of the optical power output, spectral characteristics as well as LOD values. While the IF consisted of only 7.5 pairs (15 layers) of SiO2/HfO2 layers, it resulted in an improvement of the baseline noise as well as the detection limit measured using fluorescein as test analyte, both by approximately one order of magnitude, with a LOD of 1×10(-8) mol L(-1) obtained under optimised conditions. The μ-LED-IF-OF light source was then demonstrated for use in capillary electrophoresis with fluorimetric detection. The limits of detection obtained by this device were compared to those obtained with a commercial fibre coupled LED device.

• Klíčová slova
• Capillary electrophoresis, Fluorescence detection, Light source, Micro-light emitting diode array, Optical fibre, Separations,
• Publikační typ
• časopisecké články MeSH

A novel approach for multi-wavelength ultraviolet (UV) absorbance detection has been introduced employing a single board computer (SBC) with a field programmable gate array (FPGA), Red Pitaya SBC, to generate separated micro pulses for three deep-ultraviolet light-emitting diodes (DUV-LEDs), λmax = 235, 250, and 280 nm, along with data acquisition and processing via a custom-made program. The pulse set generation and data acquisition were synchronized using the SBC. The outputs of the three pulsing DUV-LEDs were combined and transmitted to the flow cell via a solarisation resistant trifurcated optical fiber (OF). An ultra-fast responding photodiode was connected to the optical-fiber-compatible flow cell to record the intensity of the DUV pulses. Upper limit of detector linearity (A95 %) was found to be 1917 mAU, 2189 mAU, and 1768 mAU at 235 nm, 250 nm, and 280 nm, respectively, with stray light ≤0.9 %. In addition, the effective path length (Leff) was estimated to be ≥98.0 % of the length of the used flow cell (50 mm). The new pulsed multi-LEDs absorbance detector (PMLAD) has been successfully coupled with a standard liquid chromatograph and utilized for the analysis of pharmaceuticals. Paracetamol, caffeine, and aspirin were simultaneously determined at 250, 280, and 235 nm, respectively, using the PMLAD. The absorbance ratios between the different wavelengths were applied to further confirm the identity of the studied compounds. Excellent linearity was achieved over a range of 0.1-3.2 µg/mL for paracetamol, 0.4-6.4 µg/mL for caffeine, and 0.8-12.8 µg/mL for aspirin with a regression correlation coefficient (r2) ≥ 0.99996. The quantitation limits (LOQs) were 0.10 µg/mL, 0.38 µg/mL, and 0.66 µg/mL for paracetamol, caffeine, and aspirin, respectively.

• Klíčová slova
• Deep-ultraviolet absorption, High performance liquid chromatography, Multi-wavelength detection, Pulsing light-emitting diodes, Red Pitaya,
• MeSH
• Aspirin MeSH
• chromatografie kapalinová MeSH
• kofein * MeSH
• paracetamol MeSH
• ultrafialové záření * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Aspirin MeSH
• kofein * MeSH
• paracetamol MeSH