909 research outputs found
Interaction of Serum Albumin with a Sulphonated Azo Dye in Acidic Solution.
No full textThe uptake of the sulphonated azo dye [1-(tetrazolylazo)-2-hydroxynaphthalene 3,6-disulphonic acid, or T-azo-R] by bovine serum albumin (BSA) in the pH range 1–4 was investigated by a spectrophotometric method, based on the fact that the absorption spectra of the free and bound dye are different. The effect of increasing concentration of sodium chloride and sodium perchlorate was considered, as well as the influence of the BSA on the protonation equilibria of the dye. The Scatchard model, which has been widely used previously to describe the interaction between small substances and proteins, was not helpful in the treatment of data obtained in the acidity range considered here. Instead a phase distribution model allowed a good quantitative treatment of the experimental findings. The distribution constant of the monoprotonated T-azo-R between aqueous solution and the albumin microphase was found to be log Kd(HL)/γ′HL = 6.3, while the biprotonated form does not bind to BSA. As a consequence, the protonation constant of T-azo-R is decreased in the presence of BSA, particularly at low salt concentrations in aqueous solution. An equation relating the observed protonation constant to the protonation constant of the dye in solution and to the ionic strength is proposed. It has been found that the effect of salts on the uptake of T-azo-R by BSA can be explained simply by considering the variation of the activity coefficients of the ionic species involved in aqueous solution
The effects of acid and alkaline solutions on cut marks and on the structure of bone: An experimental study on porcine ribs
No full textAmong taphonomical modifications during decomposition processes, little is known about the action of
high or low pH to human tissues and bones. Moreover, acid or basic solutions are seldom used to ease
decomposition and wrecking of the body. In this study a total of 60 samples of porcine bones on which
two cut marks were produced before the beginning of the experiment, were put in six different solutions
with different pH (1, 3, 5, 9, 12, 14) and analyzed every five days over a period of 70 days. Surveys were
carried out macroscopically, with stereomicroscopy and with light microscopy on thin sections. Only the
specimens exposed to extremely acid (12) pH showed evident modifications of the bone’s
structure, as witnessed by the analyses with stereomicroscopy as well. Many samples showed a detachment
of the periosteum; cut marks became soon unrecognizable with pH 14 but still detectable in all the
other samples. The information gained from the present study can be of great help in detecting the exposure
of human tissues to high or low environmental pH and in understanding the effects that these solutions
can exert on human bones
General procedure for the determination of trace amounts of iodine in natural water samples of unknown composition by spectrophotometric titration
No full textIodine in -1 oxidation state is oxidized by iodate, and the titration is monitored spectrophotometrically. Total iodine concentration is obtained by previous reduction. Interferences from oxidizing and reducing substances are eliminated. The reaction is favoured in solution at high chloride concentration. Iodine at very low concentration level (2 10^(-7) M) can be titrated in complex matrices
Extraction and Gas-Chromatographic Determination of Residual Formaldehyde in Microsurgical Materials.
No full textA method for the extraction of residual formaldehyde from surgical materials after sterilisation and its gas
chromatographic determination as the 2,4-dinitrophenylhydrazone derivative is described. Quantitative
determinations are made using 9-cyanoanthracene as an internal standard, instead of anthracene, as
reported previously, because this compound is more stable in solution. The sensitivity is of the order of 10
ng ml-1 of extracted aldehyde. To measure the released formaldehyde under the conditions closest to those
of the human body, because of the purpose of these samples, the formaldehyde was also extracted with a
physiological solution (0.9% NaCI), at 37 "C, with and without stirring
Evaluation of the Activity Coefficients of Some Sulphonated Azo Dyes and of Their Complexes with Metal Ions.
No full textReactions between iodine, iodide and chloride, in aqueous solutions having high ionic strength
No full textThe complexation of iodine with iodide and chloride was investigated by determining the solubility of iodine in different ionic media. The activity coefficients were evaluated on the basis of the specific interaction theory, determining the interaction coefficients of the different charged specie
Determination of the metal complexing capacity of aqueous solutions containing ligands by titration in the presence of complexing resins
No full textThe feasibility of ligand titrations with metal ions using complexing resins as sorbing solids is evaluated. The resins
considered were the iminodiacetic resin Chelex 100, the carboxilic resin Amberlite CG50, and the anion exchange resin
AG1X8, whose sorbing properties for aluminium(III) and copper(II) were known from previous investigations. Synthetical
solutions containing known concentrations of ligands, EDTA and IDA were titrated separately with aluminium(III) and
copper(II), by adding known concentration of titrant metal, and measuring the concentration of metal ion sorbed on the
resin, c. The concentration of free metal ion was evaluated from c by the relationship: [M]DcV/K*w. K* is the ratio of the
concentration of metal ion sorbed on the resin to the free metal ion in solution, and strongly depends on the conditions. In the
case of the resins used in this investigation it can be calculated since the sorption equilibria of the metal ions are known. The
total concentration of the ligands and the conditional stability constants are evaluated by a linearization procedure, previously
proposed and widely used for ligand titrations, based on the hypothesis that only a 1 to 1 metal to ligand complex is formed.
Accurate results are always obtained if the titration is properly carried out, i.e. using the appropriate resin, and adding the
required excess of titrant. Some criteria are suggested to evaluate the results obtained, which can be useful when solutions of
unknown composition are titrated. For these evaluations the sorption equilibria of metal ions on the resin at the considered
conditions must be exactly known. In this paper they were evaluated from the sorbing properties of the resins, previously
investigated according to the Gibbs–Donnan model. This is very convenient, since it avoids the experimental determination at
each particular set of conditions, which is often even impossible, yet giving acceptable results
Chromatographic Behaviour of Trace Metal Ions on a Strong Base Anion Exchange Resin Functionalized by Azo Ligands.
No full textStructure and medium - dependent photodecomposition of fluoroquinolone antibiotics
No full textThe photochemical reactivity of four fluoroquinolone antibiotics is examined. For norfloxacin (NOR), enoxacin (ENX) and lomefloxacin (LOM), the only process occurring is defluorination (from position 6 for the first two drugs, from position 8 for the last one). The quantum efficiency is both structure and medium dependent (4 close to 0.5 both in water and in 0.1 M phosphate buffer for LOM,- 0.01 for ENX and 0.004 for NOR in buffer, but more than an order of magnitude higher in neat water). Ofloxacin (OFL) is less light sensitive φ 0.001) and undergoes, in part, reactions different from defluorination. The photoreaction involves heterolytic C-F bond fragmentation and its efficiency is determined by the internal charge-transfer character of the excited state (increasing in the series OFL < NOR < ENX < LOM according to the electronegativity of the substituent in position 8) and by the stabilization of the resulting aryl cation (larger for the 8-cation than for the 6-cation). The relevance of these data for the rationalization of the known phototoxicity of these drugs is discussed
Determination of dissolved inorganic species of iodine by spectrophotometric titration
No full textA method for determining iodate and iodine in aqueous solutions is proposed. The assay is similar to a
previously described method for the determination of iodide and iodine, which were titrated with standard
iodate in hydrochloric acid solution. A sample solution made 0.5-1.5 M in hydrochloric acid is titrated with a
standard iodide solution and monitored spectrophotometrically at 230 nm. The species involved have strong
absorbances that are well differentiated at this wavelength. By combining the two titrations it is possible to
resolve any mixture of species of iodine in different oxidation states. The precision of the method (standard
deviation) is the same both when determining a single species (lO3-,I+ ,l2 or I-)a nd a mixture, and is equal to
2 exp -7 M. Chloride and bromide, even at very high concentrations, do not interfere
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