Polarographic behaviour of alizarincomplexan,anodic wave and its analytical applications

Summary Polarographic Behaviour of Alizarincomplexan, Anodic Wave and Its Analytical Applications The polarographic DPP and DC techniques have been utilized to carry out the study of the anodic wave of alizarincomplexan (AC) in aqueous medium. At pH>5.7 the anodic current is produced by the complex formed between the AC and Hg(II) proceeding from the dropping electrode. At pH=7.3 theE _1/2 of this anodic wave is 0.000 V vs. Ag/AgCl. The main characteristics of the wave have been studied, and the corresponding electrode mechanism process is proposed. Since Hg(II) forms a complex with AC, a method for the amperometric determination of Hg(II) is proposed. We have also studied the analytical possibilities for doubly charged ions which form complexes with the reagent, and an amperometric method for Co(II) determination is also proposed.     

The effect of arsenic exposure on the biochemical and mineral contents of Labeo rohita bones: An FT-IR study

Arsenic compounds are ubiquitous and widespread in the environment as a result of natural or anthropogenic occurrence. Fish are the major source of protein for human consumption. They are also a source of contamination, because of the amounts of heavy elements they can contain, some of which are highly toxic. Fish bones are high in calcium, which is an essential mineral for normal body function. It consists of water, organic material, and mineral matter. Chelating agents have been used clinically as antidotes for acute and chronic metal intoxications. In the present study, an attempt is made to investigate the bio-accumulation of arsenic and its effect on the biochemical and mineral contents of Labeo rohita bones using, Fourier transform infrared (FT-IR) spectroscopy. The results of the present study indicate that arsenic exposure induces significant reduction on the biochemical and mineral contents of the L. rohita bones. Further, the DMSA treatment significantly improves these levels. This shows that DMSA is an effective chelator for arsenic toxicity. Quantitative curve-fitting analyses of amide I band have proved useful in studying the nature and the extent of protein conformational changes. A decrease in α-helical and random coil structures and an increase in β-sheet structures have been observed due to arsenic exposure. In conclusion, the present study shows that the FT-IR spectroscopy coupled with second derivative and curve-fitting analysis gives useful information about the biochemical and mineral contents of the L. rohita bones.     

FTIR study of zinc-induced biochemical changes in the liver of Indian carp <Emphasis Type="Italic">Labeo rohita</Emphasis>

Zinc is an essential metal for different physiological functions and becomes toxic when elevated concentrations are introduced into the environment. In the present study, an attempt is made to analyze zinc-induced biochemical changes in the liver tissues of freshwater fingerlings of Labeo rohita using Fourier Transformation Infrared Spectroscopy. Several important features have been observed in the FTIR spectra of zinc-intoxicated liver tissues, namely, altered membrane lipid, altered protein profile, and increased glycogen content, indicating an alteration in the lipid and protein profiles leading to modification in membrane composition. Further, it is observed that acute exposure to zinc causes some alteration in protein profile with a decrease in α-helix and an increase in random coil structure. Treatment with the chelating agent D-penicillamine reduces the biochemical contents in the liver tissues. This shows that D-penicillamine is a good antidote for zinc toxicity. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 746–752, September–October, 2008.     

Determination of Cr (in small quantities) by adsorptive stripping voltammetry: a comparative study of square wave versus differential pulse

The usefulness of an analytical method must be measured according to its practical application possibilities. A comparative study has been carried out here between the SW (working in an open atmosphere) and DP (working with de-aerated solutions) variants of catalytic-stripping adsorptive voltammetry applied to the determination of chromium traces in triethylenetetraminehexaacetic acid (TTHA) medium. In order to optimise the analytical signal, accumulation potential, nitrate ion concentration, pH, and TTHA concentration parameters were evaluated. Four linearity ranges were established within the interval 0.5–2000 nmol L^–1 chromium concentration in the cell, each with the recommended accumulation time. Quality parameters such as repeatability, linear regression, validity limits, precision, and sensitivity were evaluated. The SW variant is significantly advantageous when the chromium concentration in cell is less than 10 nmol L^–1 and even more if analysis time, cost, and being able to work in an open atmosphere are considered. The results are comparable to those obtained using GTAAS. Employing a CRM (tomato leaves), the accuracy is 1–4%. The proposed procedure, using tree leaves as samples, has been successfully tested for the possible monitoring of chromium contamination of the atmosphere.     

Effect of hexafluorobenzene on the photophysics of pyrene

Absorption and fluorescence spectroscopy studies reveal the formation of a weak complex between pyrene and C(6)F(6) even in very dilute systems. The complex affects the photophysics of pyrene and reveals a combination of static and dynamic-quenching phenomena in both polar and nonpolar solvents. The results are supported by computational studies that shed light on the structure of the complex and the interactions involved and suggest that ground and excited-state interactions are of comparable magnitude; the association is believed to be driven by quadrupolar interactions. Understanding these interactions in solution is important for applications that aim at controlling the regio- or stereoselectivity of organic reactions.     

Estimation of tensile force in tie-rods using a frequency-based identification method

A technique is developed to identify in-situ the tensile force in tie-rods which are used in ancient monumental masonry buildings to eliminate the lateral load exercised by the vaults and arcs. The technique is based on a frequency-based identification method that allows to minimize the measurement error and that is of simple execution. In particular, the first natural frequencies of the tie-rods are experimentally identified by measuring the frequency response functions (FRFs) with instrumented hammer excitation; four to six natural frequencies can be easily identified with a simple test. Then, a numerical model, based on the Rayleigh-Ritz method, is developed for the axially loaded tie-rod by using the Timoshenko beam theory retaining shear deformation and rotary inertia. Non-uniform section of the rod is considered since this is often the case for hand-made tie-rods in old buildings. The part of the tie-rod inserted inside the masonry wall is also modeled and a simple support is assumed at the extremities inside the walls. The constraints given to the part of the tie-rod inserted inside the masonry structure are assumed to be elastic foundations. The tensile force and the stiffness of the foundation are the unknowns. In some cases, the length of the rod inside the masonry wall can be also assumed as unknown. The numerical model is used to calculate the natural frequencies for a given set of unknowns. Then, a weighted difference between the calculated and identified natural frequencies is calculated and this difference is minimized in order to identify the unknowns, and in particular the tensile force. An estimation of the error in the identification of the force is given. The technique has been tested on five tie-rods at the ground floor of the famous castle of Fontanellato, Italy.     

Vibrational spectroscopy of structural defects in oligothiophenes

Vibrational spectra of oligothiophenes with structural defects are calculated within the density-functional-theory methodology. The effects of the defective αβ linkages on the infrared (IR) and Raman spectra are characterized from calculations of all isomers up to the hexamer. The signatures of αβ linked monomers can be found in IR spectra from broken symmetry arguments which result in absorptions localized in the defective region. The positions of the absorption peaks in the Raman spectra seem to be unaffected by the presence of such defects; however, strong reductions in the intensities are observed because of the shortening of the conjugation length.