A new multitracker device for rapid, in-field detection of multiple water contaminants

Accurate and selective detection of multiple water contaminants over a wide range, from parts per billion (ppb) to parts per million (ppm) is crucial, since contaminant levels vary over time. A new 'Multitracker' device was developed to this end. It is conceptually designed, 3D-printed and assembled in-house, featuring three vertically aligned LED-phototransistor pairs to minimize optical interference and enable detection of multiple species, quantified by optical measurements using contaminant-specific reagents. It also includes a microcontroller, enabling measurement of four contaminants, namely arsenic, chromium, iron and fluoride, across the visible and infrared spectrum. Multitracker can measure contaminants both below and above the permissible limits for drinking water, set by the World Health Organization. It's detection ranges are: As (2.5 ppb-1 ppm), Cr(VI) (3 ppb-2.5 ppm), Fe(II) (69 ppb-15 ppm) and F^- (160 ppb-8 ppm). Environmental testing with the device has revealed no interference from other species, except for arsenic, where Amberlite IRA-96 resin is used to mitigate phosphate interference. Validation against standard instruments, including ICP-MS, ICP-AES, UV-visible spectrophotometer and ion-selective electrode, confirms Multitracker's accuracy, even with water samples from diverse natural sources. The device maintains reliable performance across varying temperature and humidity too. It offers several advantages of cost-effectiveness ($22.5), compact size (19 × 11 × 8 cm), lightweight (920 g), rapid detection (1-15 min, depending on contaminant), with operation using just two rechargeable batteries. Thus, Multitracker offers a novel compact optical arrangement for multi-species detection, unlike existing devices, suitable for field deployment and rapid measurement.