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Voltammetric Antioxidant Analysis in Mineral Oil Samples Immobilized into Boron‐Doped Diamond Micropore Array Electrodes
Author(s) -
Zhang Xiaohang,
Paddon Christopher A.,
Chan Yohan,
BulmanPage Philip C.,
Fordred Paul S.,
Bull Steven D.,
Chang HoChol,
Rizvi Nadeem,
Marken Frank
Publication year - 2009
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200904590
Subject(s) - diamond , mineral oil , electrode , aqueous solution , perchlorate , chemistry , aqueous two phase system , electrolyte , inorganic chemistry , electrochemistry , analytical chemistry (journal) , chemical engineering , materials science , chromatography , organic chemistry , ion , engineering
Mineral oil microdroplets containing the model antioxidant N , N ‐didodecyl‐ N′ , N′ ‐diethyl‐phenylene‐diamine (DDPD) are immobilized into a 100×100 pore‐array (ca. 10 μm individual pore diameter, 100 μm pitch) in a boron‐doped diamond electrode surface. The robust diamond surface allows pore filling, cleaning, and reuse without damage to the electrode surface. The electrode is immersed into aqueous electrolyte media, and voltammetric responses for the oxidation of DDPD are obtained. In order to further improve the current responses, 20 wt% of carbon nanofibers are co‐deposited with the oil into the pore array. Voltammetric signals are consistent with the oxidation of DDPD and the associated transfer of perchlorate anions (in aqueous 0.1 M NaClO 4 ) or the transfer of protons (in aqueous 0.1 M HClO 4 ). From the magnitude of the current response, the DDPD content in the mineral oil can be determined down to less than 1 wt% levels. Perhaps surprisingly, the reversible (or midpoint) potential for the DDPD oxidation in mineral oil (when immersed in 0.1 NaClO 4 ) is shown to be concentration‐dependent and to shift to more positive potential values for more dilute DDPD in mineral oil solutions. An extraction mechanism and the formation of a separate organic product phase are proposed to explain this behavior.