Water analysis using smartphone cameras

Water quality is becoming a global concern of increasing significance. An estimated 57 million people worldwide are exposed to arsenic, As(III) concentrations in drinking water that exceed the recommended limit of 10µg/L, set by the World Health Organization (WHO). Arsenic is a poisonous substance, which interferes with cell function by binding to proteins. Chronic arsenic exposure affects human health adversely and is linked with an increased risk of several cardiovascular, and respiratory diseases. Hence, the ability to self-measure water pollutant levels effectively with a simple, portable method is desired.

Scientists in the UK have developed a mobile phone-based system that will allow people to measure the concentration of common pollutants, such as arsenic, in water. This method of detection is advantageous as it gives anyone with a smartphone the ability to analyse their drinking water to ensure it’s safe to drink.
The team, led by Elizabeth Hall from the University of Cambridge modified an algorithm, developed by scientists in Algeria for identifying cancer from skin images on a smartphone, to allow it to be used to detect Arsenic in water. The smartphone camera measures quantum dot (QDs) fluorescence in response to arsenic.

The main difficulty with past detection methods was distinguishing between the metal ions present in the water; copper (II) exhibits similar binding behaviour to arsenic (III), making them difficult to discriminate. The team developed a dual quantum dot system made up of both As(III)/Cu(II) selective QDs and also Cu(II) selective reference QDs that can be added to the water samples. This eliminates the previous problem. In order to subtract the Cu(II)baseline measurement from the overall measurement, the phone camera processes fluorescence data from the two QDs separately, this is made possible by using different red, green and blue (RGB) channels.

The use of smart phones for detecting Arsenic in drinking water has large potential for ‘in the field’ analysis. Seamus Higson, a biotechnology expert from Cranfield University, recognises this, stating “For the first time detection of As(III) beneath the WHO limit has been feasible with a mobile phone, and with more than 100 million people – equivalent to around 1.5 times the population of the UK – at risk, this has significance in its own right.”

Reference: http://www.rsc.org/chemistryworld/2015/03/phone-camera-arsenic-quantum-dot

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Naomi Mann

Chemistry Undergraduate student, Cardiff.

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