Multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-graphene hybrid composite film for simultaneous determination of catechol and hydroquinone

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

“…The pKa values of HQ and CT are 9.85 and 9.4 respectively and the two isomers are protic aromatic molecules, they will be easily deprotonated and turn to anions at high pH [2,46].…”

“…The regression equations could be expressed as I pa (µA) = 3.58 ν 1/2 (mV·s -1 ) 1/2 + 1.18 (R 2 =0.9990) for HQ and I pa (µA) = 4.83 ν 1/2 (mV·s -1 ) 1/2 + 0.45 (R 2 =0.9994) for CT. Moreover, E pa shifted to more positive values with the increase of scan rates, suggesting that the electron transfer was quasi-reversible[2].According to the slopes of the regression equations, the electroactive surface of the electrode modified can be obtained by the formula of Randles-Sevcik[42]. The electroactive area of Cu-MOF-199/SWCNTs/GCE for HQ and CT is 0.3 and 0.4cm 2 respectively, which is much larger than the area of the bare GCE (about 0.07 cm 2 calculated from the electrode diameter 3mm).…”

“…Hence, the rapid and accurate detection of HQ and CT is a significant issue for the environmental analysis. However, these two isomers are often coexisting [2], and it is difficult to separate and determine them due to their similar structures and properties. Therefore, the development of a rapid, accurate, and simple analytical method for the simultaneous detection of the two dihydroxybenzene isomers is highly desirable.…”

“…Firstly, the three-dimensional network forming from SWCNTs could enlarge the electroactive surface area, which enhancing the electrochemical responses through adsorbing more HQ and CT on the Cu-MOF-199/SWCNTs/GCE surface. Secondly, the hydroxyl and carboxyl group in Cu-MOF-199 and SWCNTs could interact with the two isomers via H-bonding, which increases the separation of oxidation peaks of the two isomers[2]. Thirdly, the incorporation between Cu-MOF-199 and SWCNTs could not only prevent the collapse of Cu-MOF-199 in the process of measurement and make the structural morphology of Cu-MOF-199 more stable in aqueous media[37], but also increase the surface area and form a conductive interconnection network which may be favorable for the charge transfer.…”

Electrochemical and Chemometric Determination of Dorzolamide and Timolol in Eye Drops Using Modified Multiwall Carbon Nanotube Electrode

“…Electrochemical detection is a very elegant method in the pharmaceutical analysis due to its high sensitivity, rapid response. Recently, CNTs are widely used in many types of sensors for determination of many compounds [17,18]. CNTs are porous materials that offer high effective surface area, mass transfer, high electrical conductivity, and strong adsorption capacity resulting in increased sensitivity of sensors [19].…”