A rapid, simple method for determining formaldehyde in drinking water using colorimetric-solid phase extraction

Formaldehyde has been detected in drinking water supplies across the globe and on board NASA spacecraft. A rapid, simple, microgravity-compatible technique for measuring this contaminant in water supplies using colorimetric-solid phase extraction (C-SPE) is described. This method involves collecting a water sample into a syringe by passage through a cartridge that contains sodium hydroxide, to adjust pH, and Purpald, which is a well-established colorimetric reagent for aldehydes. After completing the reaction in the syringe by agitating for 2 min on a shaker at 400 rpm, the 1.0-mL alkaline sample is passed through an extraction disk that retains the purple product. The amount of concentrated product is then measured on-disk using diffuse reflectance spectroscopy, and compared to a calibration plot generated from Kubelka–Munk transformations of the reflectance data at 700 nm to determine the formaldehyde concentration. This method is capable of determining formaldehyde concentrations from 0.08 to 20 ppm with a total work-up time of less than 3 min using only 1-mL samples.