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In recent years, the latest approaches in the pharmaceutical field and personalized medicine have begun to use new technologies and nanodevices for diagnosis and treatment monitoring. Nanodevices s...

Silver antimicrobial dressings have been extensively used as therapeutic strategies in wound management. The present study sought to asses and to compare the antimicrobial efficacy of commercially ...

Advances in nanotechnologies have led to the development of nanoscale biosensors with exquisite sensitivity and versatility as their ultimate goal is to detect any biochemical and biophysical signa...

In this work we present the preparation of graphene material by exfoliation of graphite rods via pulses of current in electrolyte, containing a mixture of boric acid (0.05 M) and sodium chloride (0.05 M). The material was morphologically and structurally characterized by SEM/TEM/HR-TEM, XRD and FTIR techniques. TEM investigation of graphene flakes deposited onto carbon-coated grids allowed the visualization of thin and transparent regions, attributed to few-layer graphene (FLG), as well as thick and dark regions attributed to multi-layer graphene (MLG). The mixed composition of the material was additionally confirmed by XRD, which further indicated that the amount of FLG within the sample was around 83%, while MLG was around 17%. The performance of a screen-printed electrode (SPE) modified with graphene (SPE-Gr) was tested for 8-hydroxy-2&prime, deoxyguanosine detection. The graphene-modified electrode had a higher sensitivity in comparison with that of SPE, both in standard laboratory solutions (phosphate buffered saline&mdash, PBS) and in human saliva.

In order to obtain modified electrodes with phenothiazines and to develop electrochemical methods for their determination in pharmaceutical formulations, promazine maleate, promethazine maleate and levomepromazine, were studied by linear sweep voltammetry using different types of working electrodes: carbon paste, solid carbon paste and glass-like carbon electrodes. A comparative electrochemical study of the above mentioned pheno- thiazines was performed in aqueous-alcoholic solutions, investigating the influence of pH, ionic strength and concentration on the current-potential curves. Linear sweep voltammetry in potential range from -0.1 to +1.3 V revealed that the oxidation potential and the current, strongly depend on the type of electrode and pH, the best results being obtained in acid buffer (pH 1.0). The current intensity depending linearly on the concentration in the range of 2.5·10-5-5·10-4 M promazine maleate, 2.5·10-5-2.5·10-4 M promethazine maleate and 6.2·10-5-1.2·10-3 M levomepromazine permits the development of electroanalytical methods to determine these phenothiazines in pharmaceuticals. The electrochemical determination yielded results comparable with spectrophotometric methods. Linear sweep voltammetry of carbon paste electrodes modified by incorporation of phenothiazines opens the possibility to use them as mediators in the design of some enzyme selective electrodes.

The electroanalytical study of ascorbic acid, acetaminophen and of several mixtures of these compounds in different ratios has been made by using a carbon paste electrode (CPE-graphite:solid paraffin 2:1) as working electrode and an Ag/AgCl reference electrode. The potential curves were recorded using different concentrations of ascorbic acid and acetaminophen by measuring samples between 10 and 50 microl. The oxidation reactions were studied in a potential range from -0.1 to +1.3 V with different sweep rates, at different current sensitivities, in stationary working conditions and stirring before each replicate. The oxidation of ascorbic acid occurs at +0.31 +/- 0.02 V and the oxidation of acetaminophen at +0.60 +/- 0.05 V; meanwhile, the current has a linear variation for the following concentration ranges: 10(-3)-10(-2) M for the ascorbic acid and 3 x 10(-6)-7.5 x 10(-3) M for acetaminophen (r2 = 0.999 for both ascorbic acid and acetaminophen). The mixtures of ascorbic acid and acetaminophen were made as follows: 1:1, 1:2, 1:3, 2:1, and 3:1. The studies revealed the alteration of the voltammograms processed according to the validation methodology. The best potential variation range for different current sensitivities, the influence of the sweep rate, of the solvent volume and of the pH were studied. The mutual interferences of the compounds in the mixtures and the electroactive compounds in the pharmaceutical dosage forms, especially effervescent ones, also made the object of the research. The same mixtures were studied using the direct spectrophotometric method that revealed a lot of spectral interferences. In order to solve this problem, an appropriate separation or an indirect spectrophotometric method (the apparent content curves method) were used. The spectrophotometric and voltammetric methods developed were used to determine ascorbic acid and acetaminophen in different dosage forms (vials, tablets, suppositories and effervescent dosage forms). The results were compared with those obtained by other techniques.

The electrochemical study of some 2-mercapto-5-R-ammino-1,3,4-thiadiazole derivatives was made by cyclic and linear sweep voltammetry using a carbon paste electrode (CPE, graphite/solid paraffin ratio 2:1) as working electrode and an Ag/AgCl reference electrode. The current-potential curves were recorded in anodic polarisation in -0.1 and +1.3 V range using aqueous solutions and different buffers (between pH 1.2 and 10.0), with 20 or 50 mV s(-1) sweep rate. The oxidation peak appears between +0.65 and +0.70 V due to disulphides formation. The 5-phenyl derivative has two oxidation peaks, the first at +0.45 +/- 0.03 V and the second at +0.65 +/- 0.03 V. The oxidation potentials are pH dependent, decreasing from 0.9 +/- 0.1 V at pH 1.2 to 0.6 +/- 0.1 V at a pH between 8.0 and 10.0. In some potential ranges depending on pKa of molecules the oxidation potential and oxidation current are pH independent. Simple, precise and accurate voltammetric methods for the determination of these compounds were developed and validated in 2.5 x 10(-6)-7.5 x 10(-4) mol l(-1) concentration ranges. The detection limits were 2.3 micromol l(-1) for 5-ammino-, 12.3 micromol l(-1) for 5-acetylammino-, 11.6 micromol l(-1) for 5-allylammino-, and 1.2 micromol l(-1) for 5-phenylammino-2-mercapto-1,3,4 thiadiazole derivatives.

In order to establish the dissociation constants of organic compounds, the spectrophotometric and potentiometric methods are the most precise and useful ones. Comparing the results, we used both methods for three derivatives of 2-mercapto-5-R-amino-1,3,4-thiadiazole. For the pKa determination by the spectrophotometric method we measured the ratio between the concentration of dissociated and undissociated forms. The ratio was calculated from spectral data. The potentiometric method for pKa consists of measuring the pH values within a potentiometric titration with 0.1 M NaOH. The results proved a very low acid character of the derivatives. The pKa values were influenced by the properties of the amino group substituents, and the results confirm the theoretical considerations. The study confirms the thion-thiolic tautometry of the 2-mercapto-5-R-amino-1,3,4-thiadiazole derivates and their property of being ligands for the coordination of the cations of some representative and transitional metals, with application in the preconcentration, in the detection and the quantitative determination of polluting and toxic cations in environmental analysis.

The reactions of the cations with 2-mercapto-5-R-amino-1,3,4-thiadiazole derivatives were studied conductometrically with the purpose of establishing a new conductometric method for the quantitative analysis of Pb(II) and Cd(II). Aqueous solutions of Pb(NO3)2 and Cd(CH3COO)2 were titrated with hidroalcoholic solutions of 2-mercapto-5-amino-1,3,4-thiadiazole (MATD), 2-mercapto-5-allylamino-1,3,4-thiadiazole (MA1ATD) and 2-mercapto-5-acetylamino-1,3,4-thiadiazole (MAcATD) and 2-mercapto-5-phenilamino-1,3,4-thiadiazole (MFATD) in different concentrations. The reactions takes place at pH 6.5 (realised with acetate buffer). A linear classical titration curves was obtained. In solutions more concentrated than 10(-2) M just one equivalence point can be noticed, corresponding to 1:2 Me:R stoechiometries. For concentration less than 10(-2) M two equivalence point were observed at 1:1 and 2:1 ratio of Me:R, indicating the step formation of the complex. Accurate conductometric determinations can be made using the second break points of the titration curves as equivalence points. The amounts of Cd(II) and Pb(II) taken and recovered are good, with an error less than 1%.

The method is based upon the reaction between fluoride ions and the coloured complex of Fe(III) with methyl salicylate to form the stable, colourless hexaflouride complex of iron. The conditions of the method (pH, time and combination ratio) were studied and a standard curve was obtained for 0.01-0.08 mg NaF ml-1, at 525 nm. A study was conducted on interference with complexing anions of Fe(III), cations that react with fluoride ions and with common ingredients of dosage forms and dental preparations. The method was validated and the results showed good precision (100.16 +/- = 2.33%) comparable with that of other analytical methods. Good results were obtained in the spectrophotometric determination of fluoride ions in a stomatological gel and in a toothpaste.