Analytical & Bioanalytical Electrochemistry
Volume:7 Issue: 1, Feb 2015

Using a lab-on-a-chip device, an analytical method was developed and validated for the quantitative determination of serotonin. Serotonin is a neurotransmitter that has a number of roles in biological processes. It is essential to be able to detect and quantify serotonin in different biological fluids because it can be used to evaluate and diagnose several disorders and diseases including depression, anxiety, Parkinson’s disease and Alzheimer’s. It is also beneficial to study and research the physiological roles that this neurotransmitter is involved in. Many of the conventional analytical methods require expensive instrumentation and reagents, time consuming pretreatment and derivation processes, and long analysis time. The developed method utilized microfluidic electrophoresis separation coupled with electrochemical detection. The limit of detection and limit of quantitation of serotonin were found to be 1.57 μM and 5.22 μM, respectively. The calibration curve showed a linear range between 25 μM and 500μM with a correlation coefficient of 0.9851. Accuracy was evaluated at low (50 μM), middle (200 μM), and high (500 μM) concentrations; achieving over 93% recovery with good reproducibility (%RSD>6.6%). Lastly, robustness was determined for each of the experimental conditions such as separation voltage, injection voltage, detection potential, and pH of the buffer. This novel analytical technique for serotonin detection offers many advantages including high speed analysis, great versatility, low cost, portability for on-site detection, negligible consumption of reagents/samples, and negligible waste generation. Furthermore, with modifications this method could be applied to detect serotonin in different biological fluids.

The poly (glycine) film was deposited on the surface of graphite pencil electrode (GPE) by cyclic voltammetric technique. The modified film coated graphite pencil electrode exhibits excellent electrocatalytic activity towards the detection of paracetamol at pH 7.0. The scan rate effect was found to be diffusion controlled electrode process. The concentration effect of paracetamol was linear with current. This developed method can also be applied for some neurotransmitters.

An important electro-chemical sensor was developed for the simultaneous determination of biologically electro-active compounds like ascorbic acid (AA) and dopamine (DA) which coexist in the body as an extra-cellular fluid with high oxidation potentials. Zerovalent nano iron (ZVNI) particles were synthesized by chemical method and the same particles were incorporated into a carbon paste electrode. ZVNI/ZVNISDS modified electrode was characterized by using electro-analytical techniques like SEM, cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques in 1 mM AA with 0.1 M PBS (pH 7.0) at a scan rate of 50 mVs-1. This chemically modified electrode showed a fivefold enhancement in the oxidation peak current when compared to the bare carbon paste electrode (BCPE). Scan rate was linearly proportional to the anodic peak current with a correlation coefficient of 0.9932 indicating that it is a diffusion controlled reaction. The oxidation peak current obtained for AA and DA with a linear range of 0.01 mM to 0.06 mM and 0.01 μM to 0.08 mM with a correlation coefficient of 0.9955 and 0.99562 respectively. The interference of AA and DA was successfully separated into two well resolved peaks with a potential difference of 0.0863 by using the ZVNI modified electrode. So, the proposed electro-chemical method was used to analyze the AA in clinical and pharmaceutical samples. The developed method was successfully evaluated with analytical merits like detection level, fast response, sensitivity, selectivity, stability, reproducibility and reliability.

In this paper, we fabricated a renewable and mechanical rigid electrode that we named it carbon nanotubes ceramic electrode (CNTsCE). The physicochemical properties of the obtained electrode were characterized by scanning electron microscopy and electrochemical methods. Comparing with carbon powder ceramic electrode (CPCE), the CNTsCE exhibited excellent electrochemical catalytic activities for the oxidation of ascorbic acid (AA), paracetamol (PA) and phenylephrine (PP) and three well shaped and separated anodic peaks were observed. Differential pulse voltammetry (DPV) technique was employed for the simultaneous determination of AA, PA and PP and the obtained results confirmed that the oxidation peak currents increased linearly with AA, PA and PP concentrations in the ranges of 5.0-350.0, 0.1-3.5 and 1.0-70.0 μM with detection limit of 2.0, 0.04 and 0.3 μM for AA, PA and PP, respectively. Finally, the CNTsCE was successfully used for the determination of AA, PA and PP in biological and pharmaceutical samples.

Fennel seeds extract was investigated as a potential green corrosion inhibitor for pure Aluminum in 1M hydrochloric acid using gravimetric, galvanostatic polarization and electrochemical impedance techniques. The results from gravimetric measurements illustrate increase in inhibition efficiency with increment in extract concentration. Galvanostatic polarization curve revealed that the mode of inhibition was mixed type with predominance of cathodic inhibition. The results from impedance measurements revealed that with increase in concentration of inhibitor, charge transfer resistance increases while double layer capacitance value was deduced indicating adsorption of phytochemical constituents present in extract at metal/solution interface. The quantum chemical calculation facilitates the judgment that E-anethole pursues highest activity as a corrosion inhibitor in comparison with other molecules present in the extract.

Membrane selective electrodes were used to determine tetryzoline hydrochloride (TZH) in pure form, pharmaceutical preparations and in biological fluids. The membrane selective electrodes include construction of water insoluble ion-association complexes. The TZH ion exchangers were formed using tetraphenyl borate (TZH-TPB), phosphomolybdic acid (TZH-PMA) and phosphotungstic acid (TZH-PTA), in a plasticized PVC (polyvinyl chloride) matrix, using dibutyl phthalate (DBP) or dioctylphthalate (DOP) as a plasticizer. The performance characteristics of the developed sensors were evaluated according to IUPAC recommendations. The developed sensors showed good responses but the best electrochemical characteristics and selectivity coefficients were achieved with TZH-TPB sensor using DBP as a plasticizer, where the linear responses of TZH was found within the concentration ranges of 10−6 to 10−2 mol/L and Nernstian slope was calculated to be of 56.8 mV/ decade at 25 °C, over the pH range of 5–9. The suggested method was used to determine TZH in synthetic mixtures, pharmaceutical formulations and in presence of its alkali degradation product. The proposed sensors displayed useful analytical characteristics for the determination of TZH in biological fluids such as rabbit aqueous humor and human plasma. The later application can be used to detect oral TZH poisoning in children. The obtained results were statistically compared with the official method, showing no significant difference with respect to accuracy and precision.

In this study, a Cd2+ potentiometric ion selective membrane sensor was prepared based on the selective complexation between 4b,6,7,9b-Tetrahydroxy-4bH-indeno[1,2-b]benzofuran-10(9bH)-one(ninhydrin-pyrogallol monoadduct) as ionophore and Cd2+ ion. The electrode exhibits a Nernstian response for Cd2+ ion over a concentration range of 1.0×10-1 to 1.0×10-4 mol L-1 with a slope of 28 mV per decade. The limit of detection of the sensor is 7.0×10-5mol L-1. The sensor has a relatively fast response time (∼5 s) and a useful working pH range of 3.0–7.0. Interference of some cations was also evaluated. It was used as an indicator electrode in potentiometric titration of Cd2+ with EDTA and in direct determination of Cd2+ in water and wastewater samples. The results indicate that this electrode is sensitive for determination of Cd2+.

In this work, ternary Zn-W-B alloy coatings were successfully deposited on alloy steel st37 by electroless plating technique. Zn-W-B coating was deposited from the bath, containing a cationic surfactant CTAB, with different ratio of zinc and tungsten metals [Zn/Zn+W=(0.1-0.9)]. Scanning electron microscopy (SEM) and X-Ray diffraction were employed to study the morphology and chemical composition of the deposits. The corrosion resistance of the coatings was investigated by electrochemical polarization. The results of SEM observation showed that, increasing the amount of tungsten metal in developed alloy, would dominate the crystalline phase on amorphous phase. The structures formed by compounds were also derived from the XRD results. The results of corrosion tests indicated that, the best corrosion resistance presented, when the equal amount of metals used (i.e. 0.5 for each).