An Optofluidic Monitor with On-Chip Calibration for Online Analyzing Surface Water Quality

It is of significance to develop the online automatic monitoring of water quality for water environment management. At present, many instruments and methods have been developed to online measure them, but there are some limitations exposed such as single-parameter monitoring, large volume, low efficiency, high power consumption, high reagent consumption, and excessive pollution discharge. In this work, an optofluidic monitor is designed and assembled with an automatic on-chip calibration function for onsite analyzing the surface water quality. Its working principle and hardware/software architecture are introduced in detail. In the experiment, the standard curves of the water samples (hexavalent chromium, orthophosphate, and ammonia nitrogen) were automatically obtained by a modified algorithm. Several actual water samples were collected and measured by this instrument. Compared with that recorded by the national standard method, the relative measurement error is calculated at about 6%. And its lower limit of detection is 0.05 mg/L, which satisfies the measurement requirement of most surface water. The instrument is adapted to online monitor most pollutants in surface water by changing the reagents.