Microplasma glow discharge chip for open-air atomic emission spectroscopy

This work presents a miniaturised glow discharge spectral emission chip, a compact wetchemical multi-ion sensor featuring integrated on-chip thick-planar metallic-film electrodes with a perpendicular porous layer, fabricated on a glass substrate. The device can operate at atmospheric pressure in ambient air and utilises a 500 ms DC to create the plasma. It employs a synthesised sol-gel-derived porous silica channel to wick the micropipetted liquid samples into the plasma region and controlled introduction of liquid samples in air plasma. The fabricated chip has a 5 mm × 5 mm footprint and an interelectrode gap of 55 µm. It demonstrates the detection of sodium in NaCl solution, with an estimated instrumental LOD of 0.2116 ppm, using a volume of less than 0.7 µL, showcasing a portable, simplified fabrication approach as an alternative to a conventional large-scale ICP-AES system for on-site monitoring of liquid samples.