Abstract

Miniaturisation of analytical devices through the advent of micro-fluidics is an important step forward in environmental monitoring, since sample accessing, reagents addition, measurements and calibration can be replicated on a micro-scaled equivalent to bench instrument. Micro-Total-Analysis-Systems (mTAS) provide a route to the generation of analytical instruments that can be operated in remote locations, enabling in-situ water analysis. In this paper we present the development and fabrication of a Lab-on-a-Disc multiparameter water quality monitoring system. The micro-fluidic centrifugal platform (CD) offers many advantages over standard Lab-on-a-chip such as the elimination of large power supplies and external pumps. Depending on the design, the CD is applied for the point-of-care detection of different parameters in real samples. A first CD design for pH and turbidity measurements is based on a pH dye/ionogel sensing area, which exhibits a characteristic color change depending on the pH of the solution, whereas another CD design is used for nitrite detection employing the Griess reaction method. The CDs are combined with a low-cost, wireless optical sensor, paired emitter detector device (PEDD), which enables accurate colorimetric measurements. Apart from the low-power detection, the integration of a wireless communication device allows the acquisition of parameters to be controlled remotely and to be adjusted according to individual needs, in addition to enabling data transfer. Real samples collected from different estuaries in Ireland and Tolka river were tested in terms of pH, turbidity and nitrite concentration. Strong correlations between the results obtained using the PEDD and a standard UV-Vis spectrophotometer were obtained.