Low-Cost Automatic Sensor for in Situ Colorimetric Detection of Phosphate and Nitrite in Agricultural Water

Abstract

This study proposed a low-cost sensor for in situ automatic monitoring of phosphate and nitrite in agricultural water environments, involving a series of “Fish-Bite” reservoirs, multiple reagent capsules, and a colorimetric sensor. The Fish-Bite reservoir is an alternative to the pumps, valves, and filters that are widely used for water sample collection and also offers a closed cell for chromogenic reactions afterward. Up to two capsules can be embedded in each reservoir to support chromogenic reactions that use two different reagents in sequence. From the results of calibration tests in the laboratory, the limit of detection was found to be approximately 0.01 mg/L for both phosphate and nitrite, with a linear range of 0.01–1.00 mg/L for phosphate and 0.01–0.20 mg/L for nitrite. Furthermore, an in situ experiment was successfully carried out in an irrigation canal beside farmland to demonstrate the practicability and robustness of the device. The averaged concentrations of phosphate and nitrite were 0.0113 mg/L and 0.0383 mg/L, respectively. The relative deviations were 20.2% and 11.7%, respectively, referred to results obtained by using the standard spectrophotometric methods. With the advantages of being robust, fast, and low cost, this in situ device is promising for the formation of agricultural sensor networks.

Nozzle-Jet-Printed Silver/Graphene Composite-Based Field-Effect Transistor Sensor for Phosphate Ion Detection

“…Significant efforts have been made to fabricate sensors for the development of phosphate-selective electrodes using several electroanalytical techniques. − Several optical methods including fluorescence and luminescence methods have been reported to detect orthophosphates with an accuracy of up to ∼0.01 mg/L only. − Although these methods express high limit of detection (LOD), they are still considered to be very tedious approaches. In the past, electrochemical amperometric sensors comprised of Ni, carbon black, and Co electrodes have been developed for phosphate detection. − Although the electrochemical method shows promising results, it suffers from some drawbacks such as low stability, electrode fabrication, and need of a reactive surface for phosphate ion detection.…”

Construction of polythiophene-derivative films as a novel electrochemical sensor for highly sensitive detection of nitrite

“…Currently, many analytical techniques have been proposed for nitrite detection, such as spectrophotometry [6][7][8][9], colorimetry [10], capillary electrophoresis [11][12][13], chromatography [14][15][16], chemiluminescence [17,18]. Nevertheless, most of the reported detection techniques involve some defects, such as expensive cost, limited selectivity, slow detection speed, and low sensitivity [2,19].…”

Integrated Digital Microfluidic Platform for Colorimetric Sensing of Nitrite

“…In the last decade, microfluidics has witnessed explosive growth since its introduction. , Nitrite analysis can benefit from the advantages of microfluidics, such as reduced reagent consumption, portability, fast operation, and high compatibility with multiplexing detection means, which facilitate the development of portable devices for an onsite analysis . A number of studies have focused on channel-based microfluidics with colorimetric assay of nitrite by implementing the Griess reaction. − However, cross-contamination in the enclosed microchannels induced by the gaseous intermediate species from nitrite raises the difficulty for accurate measurement . In addition, the usage of pumps and valves in the channel-based microfluidics increases the volume of the device and power consumption.…”