PhosphaSense: A fully integrated, portable lab-on-a-disc device for phosphate determination in water

A portable, compact, centrifugal microfluidic system for the in situ quantitation of phosphate in water is reported. The device uses the ascorbic acid method, a colourimetric absorbance based assay, for phosphate determination. The integrated system consists of two components; the disposable centrifugal microfluidic disc and the complementary system. The microfluidic disc is designed to have similar dimensions to that of a compact disc, with a slightly thicker composition. Capillary active micro-channels are integrated internally, through which small and precise volumes of fluids can flow. Upon loading of the disc with a water sample and chemical reagents, the fluids can be moved through the disc using centrifugal force. This is created by rotation of the disc by the motor in the complementary system. The loaded fluids are then mixed due to rapid expansion and contraction as they are forced through the microfluidic channels and significantly larger reservoirs. Once mixing has occurred, this force will then drive the fluid into the optical detection zone. The low-cost optical detection system incorporated into the complementary system consists of an LED-photodiode transducing pair that measures the absorbance of light by the molybdenum blue complex formed at 880 nm. The total mass of 2 kg and dimensions of 20 cm x 18 cm x 14 cm make this system portable and convenient for analysis at the sampling site. The limit of detection (LOD) and limit of quantitation (LOQ) of this device were 5 and 14 jig L-1 PO4-P, respectively. The linear range of 14-800 mu g L-1 and sensitivity of 0.003 AU L mu g(-1) make it suitable for analysing water bodies with low levels of phosphate. (C) 2016 Elsevier B.V. All rights reserved.