Keeping Water Safe to Drink with UV-Vis Spectrometers

Half a century ago, the US government passed the Safe Drinking Water Act.¹ In brief, this act states that anything in drinking water that is not H₂O is a contaminant. Although the US Environmental Protection Agency (EPA) imposes limits on more than 90 potential drinking-water contaminants—from chemicals, including arsenic through xylene, to microorganisms, viruses, and more—the EPA points out that “only a small number of the universe of contaminants” is on the list.² Moreover, contaminated drinking water is a global problem. According to the World Health Organization: “In 2022, globally, at least 1.7 billion people use a drinking water source contaminated with faeces.”³ Microbial contamination alone can cause diseases such as polio and typhoid, and chemical contaminants can be carcinogenic. Using a spectrometer that measures the transmission of ultraviolet (UV) and visible (Vis) light, scientists can quickly assess water samples for contamination.

For one thing, a UV-Vis spectrometer can be used at a water treatment facility to analyze contaminants in real time. As a group of scientists in Australia noted: “Online UV-Vis spectrophotometers are becoming popular choices for online water quality monitoring and process control, as they are reagent free, do not require sample pre-treatments and can provide continuous measurements.”⁴

Combining technologies

A wide range of chemical contaminants in drinking water comes from pesticides, which can be analyzed in many ways. For example, Gavin Bell, PhD, a reader in physics at the University of Warwick in the UK, and his colleagues developed a technique for testing water for various chemicals, including clothianidin and thiamethoxam, which are insecticides that act on a pest’s central nervous system. This technique, which included different light sources and UV-Vis spectrometry, detected various water contaminants, and it even provided an estimate of their concentrations. As Bell and his colleagues wrote: “Because of the simplicity of the setup, measurements can be made in real time,” and this method “could find application in a range of water quality situations, from catchment water monitoring to real-time analysis of produced water.”⁵

Using a spectrometer that measures the transmission of ultraviolet (UV) and visible (Vis) light, scientists can quickly assess water samples for contamination.

In some cases, unexpected combinations of technology can be applied to water-contaminant analysis. For instance, scientists in China used a UV-Vis spectrometer and the red, green, and blue (RGB) information collected with a smartphone to test samples for arsenic. By combining the RGB data and the spectrometry data, the scientists detected concentrations of arsenic down to 0.01 micrograms per milliliter. This team of researchers described this method as “a potential analytical system for inorganic arsenic detection in field analysis.”⁶ For example, this method could be used to test drinking water from private wells.

More monitoring ahead

While contaminated drinking water already impacts millions of people around the world, this problem is likely to worsen. For instance, Mengru Wang, PhD, assistant professor in the earth systems and global change group at Wageningen University in Netherlands, and her colleagues reported recently that the number of water sources polluted with nitrogen—usually from agricultural fertilizers or animal and human waste—could more than triple from 2010 to 2050.⁷ With challenges like that ahead, UV-Vis spectrometers could grow even more important as tools for easily assessing the safety of drinking water.

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