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A high-performance thin-layer chromatography (HPTLC) method for the quantification of propranolol in human serum is developed and validated. The method includes a liquid-liquid extraction of the analyte from the matrix using n-heptane-isoamyl alcohol (98.5:1.5, v/v) as the extraction solvent and verapamil as the internal standard.The HPTLC method employed precoated silica gel F254 HPTLC plates (10 cm × 10 cm and 10 cm × 20 cm; layer thickness 0.2 mm) prewashed with methanol, and a mobile phase comprising chloroform-methanol-ammonia (9:1:0.04, v/v/v). The developing solvent was run up to 80 mm in a vertical CAMAG chamber previously saturated with the solvent mixture for 20 min. Densitometric detection was done at λ = 290 nm. The method was linear between 5 and 100 ng/band, corresponding to 0.01 and 0.20 ng μL−1 of propranolol in human serum after the extraction process and applying 50 μL to the chromatographic plates (correlation coefficient = 0.998). The %RSD (absolute value of the coefficient of variation) of intra-assay and inter-assay precision was in the range 1.84–2.85% (n = 3) and 3.52–3.95% (n = 9), respectively. The limit of detection and limit of quantitation were found to be 3.15 and 4.02 ng/band, respectively. The method proved to be accurate, with a recovery between 96.35% and 98.82%, with an RSD not higher than 4.17%, and was selective for the active substance tested, its major metabolite, and the internal standard. This method was successfully applied to quantify propranolol in patient serum samples. Therefore, the method is useful for the quantitative determination of propranolol in human serum.

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Instrumental activation analysis was used to determine the contents of certain elements in human serum albumin (HSA). Sample irradiation was performed with a thermal neutron flux of 1.5·1013 n·cm−2·sec−1 in the RA nuclear reactor of the Boris Kidrič Institute, Vinča. Measurements were performed on a 4096-channel analyser with a high-resolution Ge(Li) detector. The Na, Cu, Br, Au, Hg, Cr, Fe, Ag, Sc, Ba and Co contents were determined in HSA produced by the Institute for Blood Transfusion, Belgrade.

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An investigation of the quantitative content of Cd and Ti in human serum samples by proton nuclear activation (PNA) has been performed and the results are presented. The activation has been induced by a 13.5 MeV proton beam of the AVF cyclotron of the University of Milan, via a (p, n) reaction on the nuclei of the target. For the quantitative determination a known amount of a reference element has been added to the samples and comparison has been made with a standard sample containing also known quantities of the elements studied. Response linearity, reproducibility and possible contaminations have been tested.

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Human serum albumin unfolding in ethanol/water mixtures was studied by use of differential scanning calorimetry. Ethanol-induced changes in DSC curves of defatted and non-defatted albumin were markedly different. In the presence of ethanol, bimodal denaturation transition for fatty acid free albumin was observed while that for albumin containing endogenous fatty acids was single and more sharpen than in aqueous solution. Ethanol was found to decrease the thermal stability of albumin due to the binding to the unfolded state to a higher degree than to the native state, thus favouring unfolding. The binding with different affinities has been suggested depending on ethanol concentration range.

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Human serum albumin (HSA) adsorbed onto silica nanoparticles modified by 3-aminopropyltriethoxysilane (APTES) and polyethyleneimine (PEI) was investigated by differential scanning calorimetry, IR spectroscopy, and photon correlation spectroscopy. The structural alterations of the protein molecules induced from adsorption process were estimated on the basis of temperatures of denaturation transition (T d) of the protein in free (native) and adsorbed form. It was found that adsorption of the protein onto the APTES-modified silica nanoparticles results in an increase in the temperature of denaturation transition from 42 to 47.4 °C. HSA adsorbed onto the PEI-modified silica nanoparticles unfolds extensively.

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The effect of ethanol on human serum albumin stability in aqueous solution was studied by use of differential scanning calorimetry. A deconvolution of DSC traces in 2-state model with ΔC p=0 and ΔC p≠0 was performed and analysed to obtain information on the interaction of ethanol with different parts of albumin molecule both fatty acid containing and fatty acid free. The differences in ethanol binding affinity for both kinds of albumin were found. At very low concentrations ethanol was observed to be a stabilizer of the folded state of albumin contrary to the higher concentration where its binding to the unfolded protein predominates.

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An instrumental planar chromatographic method (high-performance thin-layer chromatography, HPTLC) for the quantitative analysis of paroxetine in human serum was developed and validated. Paroxetine was extracted with n-hexane–isoamyl alcohol (99:1, v/v). Chromatographic separation was achieved on precoated silica gel F254 HPTLC plates using a mixture of toluene–acetone–ethanol–ammonium 25% in water (9:5:2:1, v/v) as the mobile phase. Quantitative analysis was carried out by densitometry at a wavelength of 294 nm. The method was linear between 1.00 and 14.00 ng band−1, corresponding to 0.01 and 0.14 ng μL−1 of paroxetine in human serum after extraction process and applying 10 μL to the chromatographic plates. The method correlation coefficient was 0.996. The intra-assay variation was between 0.95% and 2.21%, and the inter-assay was between 1.02% and 3.85%. The detection limit was 0.25 ng band−1, and the quantification limit was 0.55 ng spot−1. The method proved to be accurate, with a recovery between 92.00% and 101.43%, with a relative standard deviation (RSD) not higher than 7.86%, and it was selective for the active principle tested. This method was successfully applied to quantify paroxetine in patient serum samples. Therefore, it could be an important tool to evaluate patient adherence to paroxetine.

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Apparent molar volume and enthalpy changes for mixing NaCl (aq.) with albumin from human serum (aq.) are experimentally determined (25°C). Calorimetric experiments were carried out in an LKB 10700-2 calorimeter, whereas volumetric measurements were realized using an Anton Paar 60/602 densimeter. The density measurements were made after 1 and 24 h of the dissolution in the buffer (pH 4.2). The relation between the changes of the enthalpy and apparent molar volumes vs. molality of NaCl were determined. The obtained data are discussed together with data obtained previously for bovine albumin and hen egg lysozyme solutions with NaCl, Li2SO4 and (NH4)2SO4 salts of various concentration. As results correlations between the changes of enthalpy of salting and apparent molar volumes vs. molality of salts were made.

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A simple user-friendly, solid phase radioimmunoassay for testosterone in human serum based on magnetic particles is described. IgG fractions precipitated from polyclonal testosterone antiserum were coupled to magnetizable cellulose particles using carbonyl diimidazole. The prepared antibody solid phase was stable for one year when stored at 4 °C. The optimized assay involves the incubation of 50 ml of testosterone standards (0.3-10 ng/ml), 100 ml of magnetizable cellulose particle coupled antibody suspension and 100 ml of 125I-testosterone derivative for 4 hours at 37 °C. At the end of the incubation, the tubes were placed on a magnetic rack for 10 minutes after the addition of wash buffer and decanted. The sensitivity of the assay is 0.2 ng/ml. The intra-assay variation was <15% throughout the assay range. The recovery varied from 88 to 115%. On dilution of samples having high levels of testosterone, linearity ranged between 87 and 125%. Correlation coefficient of 0.978 was obtained when the developed solid phase assay was compared to the earlier established liquid phase assay.

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A simple and rapid high-performance liquid chromatographic method with fluorescence detection for analysis of loratadine (LOR) in small volumes of human serum has been developed and validated. After solid-phase extraction (SPE), with thioridazine hydrochloride as internal standard, chromatographic separation was performed on a C18 analytical column with 70:30 (v/v) acetonitrile-water, adjusted to pH 2.7 with orthophosphoric acid as mobile phase at a flow-rate of 1 min mL−1. The column was maintained at 28°C. Fluorescence detection was performed at excitation and emission wavelengths of 265 of 454 nm, respectively. The method was validated for accuracy, precision, selectivity, linearity, recovery, and stability. Absolute recovery of LOR was >93.0%. The limits of detection (LOD) and quantification (LOQ) were 0.07 and 0.2 ng mL−1, respectively. Linearity was confirmed in the range 0.2–30 ng mL−1 (correlation coefficient >0.9998). This HPLC method is selective, robust, and specific and would enable efficient analysis of large numbers of serum samples in support of pharmacokinetic, bioavailability, or bioequivalence studies after therapeutic doses of LOR.

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