Microelectrode array sensor for water quality monitoring

Abstract

A versatile microelectrode array sensor for water quality monitoring has been developed. The array fabrication, based on batch microelectronic processes, results in a highly stable passivation of the silicon chip surface and provides the possibility to use a backside contact. Packaging was optimized for on-line water operation at high pressures. Examples of applications include chlorine monitoring in drinking water, ozone monitoring in deionized water, dissolved oxygen in activated sludge and preliminary measurements of trace arsenic.

μ-MIP: Molecularly Imprinted Polymer-Modified Microelectrodes for the Ultrasensitive Quantification of GenX (HFPO-DA) in River Water

“…This literature value coincides with the resistivity of the Haw River, which was measured to be 8.4 kΩ ̇ cm (Figure a). This resistance may manifest in an iR drop, which distorts voltammetric peak positioning and grows as the current passed increases, resulting in temporal error. , This principle is demonstrated in Figure b, where the peaks due to the oxidation of ferrocyanide on a macroelectrode ( r = 1 mm) are observed to shift significantly between voltammograms in 0.01 M ammonium buffer and Haw River surface water. This shift is due to a 125-fold difference in solution conductivity between the buffer and the environmental sample.…”

“…In contrast, MIP-modified microelectrodes pass current on the order of nanoamperes, minimizing voltammetric distortion and enhancing the reliability of the sensing platform (Figure b, inset). Thus, the ability to obtain measurements without significant distortions related to solution resistance makes microelectrodes amenable to environmentally relevant matrices. − Microelectrodes also present minimal background current resulting from the double-layer capacitance, enhancing sensitivity. − Multiplexing microelectrode arrays to detect multiple target species also holds promise for the detection and quantification of a wide range of PFAS chemical variants. Extending the MIP-modified microelectrode platform to achieve these goals will be the subject of future investigations by this group.…”

Arrays of microelectrodes: technologies for environmental investigations

“…An array of gold microdisc electrodes on a silicon substrate could be synthesised and used for a number of applications. 52 The array consisted of 137 gold microdiscs, 15 mm in diameter, spaced by 300 mm in a hexagonal pattern, supported on a 2.8 Â 7 Â 0.5 mm silicon chip. Several applications were proposed, one of which was the determination of free chlorine in drinking water, the sensor proved suitable for the amperometric detection of chlorine with a linear range of 0-1 mg l À1 and a detection limit of 0.02 mg l À1 of free chlorine.…”

“…53 The same sensor could also be applied for the amperometric determination of ozone in puried water, with the microelectrode array format allowing operation in such a high resistance (up to 18 MOhm cm) media with a linear response up to 200 ppb, a detection limit <5 ppb and stability for up to 2.5 months continuous use in deionised water. 52 The device could also be used for the monitoring of oxygen in activated sludge with a detection limit of 0.2% relative oxygen or, combined with a stripping voltammetry technique to give an arsenic sensor capable of detecting up to 100 ppb As 3+ with a detection limit <1 ppb. 52 Many of the microarrays described within this work still require fabrication via lengthy and relative expensive processes such as photolithography.…”

“…52 The device could also be used for the monitoring of oxygen in activated sludge with a detection limit of 0.2% relative oxygen or, combined with a stripping voltammetry technique to give an arsenic sensor capable of detecting up to 100 ppb As 3+ with a detection limit <1 ppb. 52 Many of the microarrays described within this work still require fabrication via lengthy and relative expensive processes such as photolithography. One elegant way it to utilise waste electronic chips, these can be sawed in half, normal to the longest axis.…”