Low-cost handheld filter spectrometer for water quality measurements

Many common chemical sensors for environmental contaminants are based on a change in optical absorbance. The gold standard for measuring optical absorbance is UV/VIS spectrometry, but this typically requires an expensive bench-top instrument. Here we present a hand-held low resolution filter-based spectrometer that measures optical absorbance in six wavelength bands of the visible spectrum, built for less than \$100. This is sufficient to quantify the absorbance of several common color-based chemical sensors used for the detection of contaminants in water. We demonstrate our device by measuring fluoride concentrations in drinking water samples using an EPA-approved protocol (EPA-NERL 340.1) and show that our 6-channel device outperforms single-wavelength photometric measurements taken with an industry-standard commercial photometer in both detection threshold and sensitivity.