Chiang Mai Journal of Science

 Green analytical chemistry methods have attracted increasing attention for sustainable development in analytical laboratories. Miniaturization of analytical devices and replacement of chemical regents with ecofriendly ones are key steps to realizing the objectives of green analytical chemistry. This work describes a microfluidic-based micro-flow injection analysis (μ-FIA) system for determination of silver ions (Ag⁺) in water samples using C-phycocyanin extracted from cyanobacteria as a natural and safe colorimetric reagent. The μ-FIA system is comprised of a 30 × 30 square polymethylmethacrylate platform on which the microchannel architecture has been engraved with a CO₂ laser. The microchip was sandwiched between two polydimethylsiloxane sheets for packaging and to facilitate its integration with fiber optic spectrometer for signal monitoring, and a multi-syringe pump for delivery/manipulation of solutions. At optimized operating conditions, the system response was linear over the range 0.080–2.40 mg L⁻¹ with a R² of 0.9996, and the detection limit was 25 μg L⁻¹. The developed method was applied to analysis of Ag⁺ in drinking water, river water and wastes, and the results were comparable with those from the standard inductively coupled plasma optical emission spectrometry method. The outstanding features of this system are the low consumption of reagents by the microfluidic device, and the replacement of toxic reagents with natural, ecofriendly alternatives.