An Electrochemical Sensor Based on Amino Magnetic Nanoparticle-Decorated Graphene for Detection of Cannabidiol

For detection of cannabidiol (CBD)—an important ingredient in Cannabis sativa L.—amino magnetic nanoparticle-decorated graphene (Fe3O4-NH2-GN) was prepared in the form of nanocomposites, and then modified on a glassy carbon electrode (GCE), resulting in a novel electrochemical sensor (Fe3O4-NH2-GN/GCE). The applied Fe3O4-NH2 nanoparticles and GN exhibited typical structures and intended surface groups through characterizations via transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), and Raman spectroscopy. The Fe3O4-NH2-GN/GCE showed the maximum electrochemical signal for CBD during the comparison of fabricated components via the cyclic voltammetry method, and was systematically investigated in the composition and treatment of components, pH, scan rate, and quantitative analysis ability. Under optimal conditions, the Fe3O4-NH2-GN/GCE exhibited a good detection limit (0.04 μmol L−1) with a linear range of 0.1 μmol L−1 to 100 μmol L−1 (r2 = 0.984). In the detection of CBD in the extract of C. sativa leaves, the results of the electrochemical method using the Fe3O4-NH2-GN/GCE were in good agreement with those of the HPLC method. Based on these findings, the proposed sensor could be further developed for the portable and rapid detection of natural active compounds in the food, agricultural, and pharmaceutical fields.

Colorimetric detection of Cu2+ based on the formation of peptide–copper complexes on silver nanoparticle surfaces

We developed a colorimetric method for the rapid detection of copper ions (Cu2+) in aqueous solution. The detection of Cu2+ is based on coordination reactions of Cu2+ with casein peptide-functionalized silver nanoparticles (AgNPs), leading to a distinct color change of the solution from yellow to red. The developed method has a good detection limit of about 0.16 µM Cu2+ using 0.05 mL of AgNPs stock solution and a linearity in the range of 0.08–1.44 µM Cu2+ with a correlation coefficient of R2 = 0.973. The developed method is a useful tool for the detection of Cu2+ ions. Furthermore, it can be used for monitoring Cu2+ in water at concentrations below the safe limit for drinking water set by the World Health Organization.

A fluorogenic and chromogenic dual sensor for the detection of cyanide and copper(ii) in water samples and living cells

Here we describe a simple fluorescent sensor based on intra molecular charge transfer to detect cyanide in aqueous media selectively with a very good detection limit and cascade recognition of aq. copper(ii) ions.

Tuning the direct growth of Agseeds into bimetallic Ag@Cu nanorods on surface functionalized electrochemically reduced graphene oxide: enhanced nitrite detection

The significant challenges in the growth of 1D nanostructure on reduced graphene oxide surface were addressed. It enabled the electrooxidation of the nitrite ion (NO2−) with high sensitivity and good detection limit of 1 nM.

Particle Induced X-ray Emission (PIXE): A Tool of Qualitative Elemental Analysis for Biological Sample

The facility of ion beam laboratory at Kochi University of Technology (KUT) has been extended by installing the Particle Induced X-ray Emission (PIXE) technique, in order to provide qualitative and quantitative elemental analysis and in-air micro-PIXE analysis. This paper is a description of PIXE setup and its application in biological sample for qualitative elemental analysis. The energy calibration of the system shows linearity. The minimum detection limit indicates that the system has good detection limit. The homogeneity shows uniformity of the sample itself and the internal standard within the sample. A 4 MeV He++ ion beam was used to analyze shellfish samples. Analyzing samples, it was found that the lower Z elements as well as some trace elements were detected. DOI: http://dx.doi.org/10.3329/rujs.v39i0.16538 Rajshahi University J. of Sci. 39, 01-10 (2011)

Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide

Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.

Preparation and electrochemical application of rutin biosensor for differential pulse voltammetric determination of NADH in the presence of acetaminophen

The electrocatalytic behavior of reduced nicotinamide adenine dinucleotide (NADH) was studied at the surface of a rutin biosensor, using various electrochemical methods. According to the results, the rutin biosensor had a strongly electrocatalytic effect on the oxidation of NADH with the overpotential being decreased by about 450 mV as compared to the process at a bare glassy carbon electrode, GCE. This value is significantly greater than the value of 220 mV that was reported for rutin embedded in a lipid-cast film. The kinetic parameters of the electron transfer coefficient, ?, and the heterogeneous charge transfer rate constant, kh, for the electrocatalytic oxidation of NADH at the rutin biosensor were estimated. Furthermore, the linear dynamic range; sensitivity and limit of detection for NADH were evaluated using the differential pulse voltammetry method. The advantages of this biosensor for the determination of NADH are excellent catalytic activity and reproducibility, good detection limit and high exchange current density. The rutin biosensor could separate the oxidation peak potentials of NADH and acetaminophen present in the same solution while at a bare GCE, the peak potentials were indistinguishable.

Gas/Diffusion Flow Injection Determination of Ammonium Ions in River and Waste Waters by Conductometry

An FIA conductometric method for monitoring of ammonium ions in river and waste waters is proposed. A very good detection limit (xD 5.6 μmol l-1) was obtained at 100/20 s preconcentration/rinsing times and 2 ml sample consumption per analysis at the flow rate 0.8 ml min-1. The detection limit xD can be further improved at longer preconcentration/ rinsing times. Precipitation of polyvalent metal ions (mainly Fe(III)) was eliminated by addition of 0.5 mmol l-1 EDTA prior to injection. The results are comparable with those obtained by spectrophotometry (Nessler's reagent).