Detection of phenolic compounds using impedance spectroscopy measurements

Abstract

Langmuir-Blodgett (LB) and layer-by-layer films (LbL) of a PPV (p-phenylenevinylene) derivative, an azo compound and tetrasulfonated phthalocyanines were successfully employed as transducers in an "electronic tongue" system for detecting trace levels of phenolic compounds in water. The choice of the materials was based on their distinct electrical natures, which enabled the array to establish a fingerprint of very similar liquids. Impedance spectroscopy measurements were taken in the frequency range from 10 Hz to 1 MHz, with the data analysed with principal component analysis (PCA). The sensing units were obtained from five-layer LB films of (poly[(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene]), OC(1)OC(18)-PPV (poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene)), DR (HEMA-co-DR13MA (poly-(hydroxyethylmethacrylate-co-[4'-[[2-(methacryloyloxy)-ethyl]ethylamino]-2-chloro-4-nitroazobenzene]))) and five-bilayer LbL films of tetrasulfonated metallic phthalocyanines deposited onto gold interdigitated electrodes. The sensors were immersed into phenol, 2-chloro-4-methoxyphenol, 2-chlorophenol and 3-chlorophenol (isomers) solutions at 1 x 10(-9) mol L(-1), with control experiments carried out in ultra pure water. Samples could be distinguished if the principal component analysis (PCA) plots were made with capacitance values taken at 10(3) Hz, which is promising for detection of trace amounts of phenolic pollutants in natural water.

Microfluidic Electronic Tongue Applied to Soil Analysis

“…From the S values, one infers that an optimized performance was achieved with feature selection and IDMAP, which is consistent with the recent literature, according to which IDMAP has been proven superior for analyzing sensing and biosensing data [28]. Generally, impedance analysis as a function of frequency allows the identification of potential interactions at the electrode/electrolyte interface through equivalent electrical circuits [7,17,19,29]. However, it is known that interactions between the nanostructured thin films forming the sensing Generally, impedance analysis as a function of frequency allows the identification of potential interactions at the electrode/electrolyte interface through equivalent electrical circuits [7,17,19,29].…”

“…This allows for the construction of simple, inexpensive equipment for on-site measurements. To demonstrate this idea, we show the well-established PCA plot at a fixed frequency (1 kHz) in Figure 6, where the electrical response is dominated by film/liquid interactions [29]. Though the distinguishing ability is not as good as with IDMAP and feature selection in Figure 5, it is indeed possible to distinguish the samples with this much simpler procedure with a measurement at only one frequency.…”

“…Generally, impedance analysis as a function of frequency allows the identification of potential interactions at the electrode/electrolyte interface through equivalent electrical circuits [7,17,19,29]. However, it is known that interactions between the nanostructured thin films forming the sensing Generally, impedance analysis as a function of frequency allows the identification of potential interactions at the electrode/electrolyte interface through equivalent electrical circuits [7,17,19,29]. However, it is known that interactions between the nanostructured thin films forming the sensing units deposited onto the IDEs with the liquid systems are reflected in the electrical response at the kHz region [7,17,19].…”

Electronic Tongues Employing Electrochemical Sensors

“…Recently, Olivati and co-workers employed an array of impedimetric sensors formed by different LB films of conducting polymers and phtalocyanines to detect trace levels of phenolic compounds and chlorophenols in water [77]. Samples could be distinguished by PCA analysis of the capacitance signal at a discrete frequency of 1 kHz.…”

Comparative Studies of Photophysicochemical Properties of Non-Peripherally Anisole/Thioanisole-Tetrasubstituted Gallium (III) Phthalocyanines Containing Oxygen/ Sulfur Bridge

“…These kind of groups have extensively been used in both medical and industrial purposes like antiallergenic, antiartherogenic, antiinflammatory, antimicrobial, antioxidant, antithrombotic, cardioprotective, and vasodilatory effects. Non-peripheral substitution causes red-shift in the Q-band, suggesting optimal transparency into tissue in PDT (11)(12)(13)(14)(15)(16).…”