Photometric Sensing of Active Chlorine, Total Chlorine, and pH on a Microfluidic Chip for Online Swimming Pool Monitoring.

Sait Elmas,Aneta Anna Sekulska,Craig Priest,Stephen Thornton,Aneta Pospisilova,Vasil Vasilev,Thomas Nann

doi:10.3390/s20113099

Abstract

A microfluidic sensor was studied for the photometric detection of active chlorine, total chlorine, and pH in swimming pool samples. The sensor consisted of a four-layer borosilicate glass chip, containing a microchannel network and a 2.2 mm path length, 1.7 μL optical cell. The chip was optimised to measure the bleaching of methyl orange and spectral changes in phenol red for quantitative chlorine (active and total) and pH measurements that were suited to swimming pool monitoring. Reagent consumption (60 μL per measurement) was minimised to allow for maintenance-free operation over a nominal summer season (3 months) with minimal waste. The chip was tested using samples from 12 domestic, public, and commercial swimming pools (indoor and outdoor), with results that compare favourably with commercial products (test strips and the N,N′-diethyl-p-phenylenediamine (DPD) method), precision pH electrodes, and iodometric titration.

Highlights

Chlorination is widely used to disinfect recreation and drinking water, is strictly regulated [1,2], and must be carefully monitored to avoid outbreaks of waterborne disease [3,4]
Chlorine gas that is generated at an anode surface immediately disproportionates in swimming pool water to form HOCl and HCl, acidifying the water
LEDs and photodiodes; the results presented here were obtained using a custom-built micro-spectrophotometer, based on an Olympus BH2-UMA frame [27]

Summary

Introduction

Chlorination is widely used to disinfect recreation and drinking water, is strictly regulated [1,2], and must be carefully monitored to avoid outbreaks of waterborne disease [3,4]. While commercial water treatment is professionally managed by water utilities and the government, most swimming pools are managed by non-technical pool owners (domestic) or operators (commercial/public), who rely on retail test products and “grab” (manual) sampling. We address the demand for a chip-based photometric chlorine (active and total) and pH sensor that is suitable for online monitoring on domestic and commercial/public swimming pools. Chlorine gas that is generated at an anode surface immediately disproportionates in swimming pool water to form HOCl and HCl, acidifying the water.

Methods

Results

Conclusion