Perfluoroalkyl Substances (PS) are persistent and globally distributed environmental contaminants. Analytical methods used for PS detection are currently dominated by chromatography in combination with mass spectrometry. These methods are highly sensitive and selective but expensive (typically &gt; $100/sample) and unsuitable for low-cost, on-site screening. Our detection method takes advantage of the high surface activity of PS, which affects the electrochemical bubble nucleation, and then transduces the change of nucleation condition to electrochemical signal for PS quantitation. The nanoscale dimension of the electrodes provides exquisite sensitivity for detecting slight changes near or at the electrode surface, while fast electrochemical measurements allow studying the dynamics of bubble nucleation. When PS concentration increases, the solution surface tension decreases resulting in a lower nucleation energy barrier. Consequently, a lower supersaturation concentration is required for H2 nanobubble nucleation resulting in a reduction of bubble nucleation current. Using this method, we demonstrate the quantitation of perfluorinated surfactants in water, with a remarkable limit of detection (LOD) down to 80 μg/L and a linear dynamic range of over three orders of magnitude. With the addition of a preconcentration step, we have achieved the LOD range covering 70 ng/L, the health advisory for perfluorooctane sulfonate and perfluorooctanoic acid in drinking water established by the US EPA. The experimental results are in quantitative agreement with the model we derived from classical nucleation theory. Our method also exhibits exceptional specificity for the surfactant analytes even with 1000-fold excess of non-surfactant interference. This research provides the proof of principle study of a bubble nucleation-based sensing platform, which will be further developed toward a low-cost and portable tool for on-site detection of PS compounds in water. In addition, our method has the potential of further developing into a universal electrochemical detector for surfactant analysis due to its surface activity-based detection mechanism.

Bubble nucleation-based electrochemical detection method for perfluorinated surfactants

2019 Fall National Meeting

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