Chemically surface-modified (tosyl-functionalized) carbon nanoparticles (Emperor 2000 from Cabot Corp.) are employed for the extraction and electrochemical determination of phenolic impurities such as benzophenone-3 (2-hydroxy-4-methoxybenzophenone) or triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol). The hydrophilic carbon nanoparticles are readily suspended and separated by centrifugation prior to deposition onto suitable electrode surfaces and voltammetric analysis. Voltammetric peaks provide concentration information over a 10-100 mu M range and an estimated limit of detection of ca. 10 mu M (or 2.3 ppm) for benzophenone-3 and ca. 20 mu M (or 5.8 ppm) for triclosan. Alternatively, analyte-free carbon nanoparticles immobilized at a graphite or glassy carbon electrode surface and directly immersed in analyte solution bind benzophenone-3 and triclosan (both with an estimated Langmuirian binding constants of K approximate to 6000 mol(-1) dm(3) at pH 9.5) and they also give characteristic voltammetric responses (anodic for triclosan and cathodic for benzophenone-3) with a linear range of ca. 1-120 mu M. The estimated limit of detection is improved to ca.5 mu M (or 1.2 ppm) for benzophenone-3 and ca. 10 mu M (or 2.3 ppm) for triclosan. Surface functionalization is discussed as the key to further improvements in extraction and detection efficiency.
Vidal, L., Chisvert, A., Canals, A., Psillakis, E., Lapkin, A. A., Acosta, F., Edler, K. J., Holdaway, J. A., & Marken, F. (2008). Chemically surface-modified carbon nanoparticle carrier for phenolic pollutants: Extraction and electrochemical determination of benzophenone-3 and triclosan. Analytica Chimica Acta, 616(1), 28-35. https://doi.org/10.1016/j.aca.2008.04.011