Electroanalytical detection of pindolol: comparison of unmodified and reduced graphene oxide modified screen-printed graphite electrodes

Recent work has reported the first electroanalytical detection of pindolol using reduced graphene oxide (RGO) modified glassy carbon electrodes [S. Smarzewska and W. Ciesielski, Anal. Methods, 2014, 6, 5038] where it was reported that the use of RGO provided significant improvements in the electroanalytical signal in comparison to a bare (unmodified) glassy carbon electrode. We demonstrate, for the first time, that the electroanalytical quantification of pindolol is actually possible using bare (unmodified) screenprinted graphite electrodes (SPEs). This paper addresses the electroanalytical determination of pindolol utilising RGO modified SPEs. Surprisingly, it is found that bare (unmodified) SPEs provide superior electrochemical signatures over that of RGO modified SPEs. Consequently the electroanalytical sensing of pindolol is explored at bare unmodified SPEs where a linear range between 0.1 μM–10.0 μM is found to be possible whilst offering a limit of detection (3σ) corresponding to 0.097 μM. This provides a convenient yet analytically sensitive method for sensing pindolol. The optimised electroanalytical protocol using the unmodified SPEs, which requires no pre-treatment (electrode polishing) or electrode modification step (such as with the use of RGO), was then further applied to the determination of pindolol in urine samples. This work demonstrates that the use of RGO modified SPEs have no significant benefits when compared to the bare (unmodified) alternative and that the RGO free electrode surface can provide electro-analytically useful performances

Martensitic Transformation Development in the Rolled Ti-Ni Alloy : Varying of Temperature Parameters Depending on Grain Orientation

Inhomogeneity of martensitic transformations in the rolled alloy Ti-50.3%Ni was investigated by use of X-ray texture diffractometry. For the first time temperature parameters of the reverse mortensitic transformation B19'→B2 were measured systematically for grains, corresponding by their orientation to 130 different points within a quadrant of the stereographic projection. Depending on grain orientations, the temperature interval of the reverse martensitic transformation has a width from 20° to 40°. Obtained data correlate with known regularities of strain hardening distribution in textured materials

Texture Changes in the Plastic Deformation Zone Near the Fracture Surface of the Zr-1% Nb Alloy Sheet

A wave of local plastic deformation moves in front of any crack and is responsible for strain hardening and rotation of crystalline lattice within the layer adjacent to the fracture surface. It was found by X-ray diffractometric study, that a directional reorientation of grains takes place near the fracture surface, leads to formation of the specific cristallographic textures and controls the further movement of the crack. The fracture anisotropy of the rolled zirconium alloy correlates with the character of observed texture changes in the plastic deformation zone and can be predicted using the texture formation models by taking into account a variety of α-Zr deformation micromechanisms. Alternative activation of prismatic slip or twinning depending on the tension direction determines both the thickness and the structure features of the plastic deformation zone near the fracture surface

Heredity of Structure Inhomogeneity under Phase Transformations in Textured Zr-20%Nb Alloy

Development of β → ω and β → α phase transformations in the rolled quenched alloy Zr-20%Nb was studied by methods of X-ray texture diffractometry. Usage of a position sensitive detector allowed to construct, besides usual texture pole figures, distributions of X-ray line broadening and lattice elastic deformation depending on the orientation of reflecting planes. Diagrams of correlation between pole figures of different types for β-, ω- and α-phases were analyzed to reveal factors controlling inhomogeneity of phase transformations and substructure features of derivative phases

Inhomogeneity of Phase Transformations β→ω and β→α in the Quenched Cold-Rolled Alloy Zr-20 %Nb

The inhomogeneous character of phase transformations in the quenched cold-rolled alloy Zr - 20%Nb was investigated using new X-ray diffractometric procedures based on a position sensitive detector. It was shown that the distribution of strain hardening in β-grains with different orientations controls the development of phase transformation β→α and β→ω in the rolled alloy. Derivative phases inherit the substructure inhomogenity of the β-phase, i.e. their grains are most dispersive and/or have the most distorted crystalline lattice in texture minima, where both phase transformations develop primarily. To explain the obtained X-ray texture data a mechanism was suggested involving local formation of quasi-amorphous boundary interlayers by cold rolling and their crystallization by annealing