(157f) Point-of-Use Fiber-Based Haloacetic Acid Sensor for Water at Sub-USEPA Regulation Limits

With the development of industries across the world, the amount of pollution released into the ecosystem has increased significantly, creating serious issues related to water pollution. The entry of halogenated compounds—including haloacetic acids (HAAs),a family of chemicals formed during the water treatment process—into treated water has been so severe that the US Environmental Protection Agency (USEPA) has limited the maximum contaminant level (MCL) in drinking water to less than 60 ppb. HAAs including five related chemicals: trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, dibromoacetic acid, and monobromoacetic acid. These can enter the human body through ingestion, inhalation, and epidermal routes causing serious health problems such as colon and bladder cancer.

In this study, syndiotactic polyethylene (sPP) fiber mats electrospun by a DC electrospinning device are used to preconcentrate and detect different compositions of HAA in water samples. A well-known reaction chemistry – the Fujiwara reaction- has been used to give a red/pink chromophore under visible light absorption, which can detect combined HAA concentrations in the water samples.

The present highly sensitive and selective sensor works well when the reaction chemistry has no contact with water - a barrier to the Fujiwara reaction. Because of the detrimental effects of water on the Fujiwara reaction, the hydrophobicity of the electrospun fiber mats has been increased by increasing the roughness of the surface and spinning sPP fiber mat with a beaded fiber morphology. These fibers result in a superhydrophobic mat with a water contact angle over 150°. When water samples are exposed to temperature around 80°C, preconcentrated HAA in the vapor phase -between water sample surface and electrospun mat – becomes trapped in the liquid phase of Fujiwara reactants present on the surface of the sPP fiber mat. A yellow color indicates the ppb level of HAAs and can be analyzed with an image analysis software to measure the corresponding color intensity of the specific HAA concentration. Calibration curves obtained by these analyses can help us to accurately predict the level of HAA contaminant in complex environmental samples.

In this work, we were able to predict the concentration of HAAs in water samples down to a level of 6 ppb, which is one order of magnitude below the USEPA limit for drinking water. The advantages of this method over conventional HAA detection methods are the inexpensiveness, portability, and sensitivity of the sensor, which enables point-of-use detection of water contaminants in the simplest and quickest manner.