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41.
Studies carried out by X-ray and thermal analysis confirmed that acetaminophen (paracetamol), declared by the manufacturers as an Active Pharmaceutical Ingredient (API), was present in all studied medicinal drugs. Positions of diffraction lines (2θ angles) of the studied drugs were consistent with standards for acetaminophen, available in the ICDD PDF database Release 2008. |Δ2θ| values were lower than 0.2°, confirming the authenticity of the studied drugs. Also, the values of interplanar distances dhkl for the examined samples were consistent with those present in the ICDD. Presence of acetaminophen crystalising in the monoclinic system (form I) was confirmed. Various line intensities for API were observed in the obtained diffraction patterns, indicating presence of the preferred orientation of the crystallites in the examined samples. Thermal analysis of the studied substances confirmed the results obtained by X-ray analysis. Drugs containing only acetaminophen as an API have melting point close to that of pure acetaminophen. It was found that presence of other active and auxiliary substances affected the shapes and positions of endothermal peaks significantly. A broadening of endothermal peaks and their shift towards lower temperatures were observed accompanying an increase in the contents of additional substances being “impurities” in relation to the API. The results obtained by a combination of the two methods, X-ray powder diffraction (XRPD) and differential scanning calorimetry/thermogravimetry (DSC/TGA), may be useful in determination of abnormalities which can occur in pharmaceutical preparations, e.g., for distinguishing original drugs and forged products, detection of the presence of a proper polymorphic form or too low content of the active substance in the investigated drug.  相似文献   
42.
New chromium(III) complexes, [Cr(C2O4)2(2-hnic)]2− and [Cr(C2O4)2(3-hpic)]2− (where 2-hnic = O,O′-bonded 2-hydroxynicotinic acid and 3-hpic = N,O-bonded 3-hydroxypicolinic acid), were obtained and characterized in solution. The acid-catalyzed aquation of the both complexes leads to liberation of the appropriate pyridinecarboxylic acid and formation of cis-[Cr(C2O4)2(H2O)2]. Kinetics of these reactions were studied spectrophotometrically in the 0.1–1.0 M HClO4 range, at I = 1.0 M. In the case of [Cr(C2O4)2(2-hnic)]2−, a slow chelate-ring opening at the Cr–O (phenolate) bond is followed by a fast Cr–O (carboxylate) bond breaking. The rate law: kobs = kHQH[H+] was established, where kH is the acid-catalyzed rate constant and QH is the protonation constant of the coordinated phenolate oxygen atom. In the case of [Cr(C2O4)2(3-hpic)]2−, the reversible chelate-ring opening at Cr–N bond is followed by the rate determining step – the one-end bonded ligand liberation. The rate law for the first step was determined: kobs = k1+k−1/Q1[H+], where k1 and k−1 are the rate constants of the chelate-ring opening and closure and Q1 is the protonation constant of the pyridine nitrogen atom. The aquation mechanisms are proposed and the effect of ligand coordination mode on complex reactivity is discussed.  相似文献   
43.
A series of homoleptic complexes of hexacoordinate cobalt(II) and copper(II) complexes with 3,5-disubstituted homo- and heteroscorpionate tris(pyrazolyl)borate anionic ligands (Tp′) were synthesized, i.e. bis[hydrotris(3-phenyl,5-methylpyrazol-1-yl)borato]cobalt(II), bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) and bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]copper(II) and their structures were elucidated crystallographically. The complexes were also formed spontaneously during attempted metathesis of the corresponding Tp′M(NCS) complexes into Tp′M(OOCCH(OH)CH3) complexes. In the case of the analogous conversion applied for the thiocyanato [hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3,5-dimethylpyrazol-1-yl)boratocobalt(II) complex with sodium carboxylates (lactate, pyruvate and 2-hydroxybutyrate), the cross-transfer of pyrazolyl residues between starting anionic ligands was observed resulting in formation of bis-ligand homo- and heteroleptic Tp′CoTp″ complexes, where Tp′, Tp″ were tris(pyrazolyl)borates composed of n 3(5)-phenyl,5(3)-methylpyrazolyl and (3−n) 3,5-dimethylpyrazolyl residues (n=0–3) identified by mass spectrometry. Metathesis of thiocyanate in thiocyanato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) into pyruvate led to the isolation of stable the pyruvato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) complex, the structure of which was determined crystallographically. The Tp′ ligands are η3 coordinated to metal ions in every case, whereas the pyruvate anion is coordinated through carboxylate and carbonyl oxygen atoms to the cobalt center. Two rotational isomers distinguishable by 1H NMR spectroscopy for the hexacoordinate bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) complex were detected in solution.  相似文献   
44.
A series of new hypervalent iodine reagents based on the 1,3‐dihydro‐3,3‐dimethyl‐1,2‐benziodoxole and 1,2‐benziodoxol‐3‐(1H)‐one scaffolds, which contain a functionalized tetrafluoroethyl group, have been prepared, characterized, and used in synthetic applications. Their corresponding electrophilic fluoroalkylation reactions with various sulfur, oxygen, phosphorus, and carbon‐centered nucleophiles afford products that feature a tetrafluoroethylene unit, which connects two functional moieties. A related λ3‐iodane that contains a fluorophore was shown to react with a cysteine derivative under mild conditions to give a thiol‐tagged product that is stable in the presence of excess thiol. Therefore, these new reagents show a significant potential for applications in chemical biology as tools for fast, irreversible, and selective thiol bioconjugation.  相似文献   
45.
46.
The aim of this paper was to assess the oxidative stability of structured lipids synthesized by enzymatic interesterification of a blend of lard and rapeseed oil with concentrates of n ? 3 fatty acids. Differential scanning calorimetry was used to evaluate the oxidation induction time of interesterified fats as a parameter assessing resistance of tested fats to their thermal-oxidative decomposition. Moreover, the IR spectra registered in the classic spectral range (4000–400 cm?1) were used to differentiate the samples of interesterified fats. The results show that the interesterification process decreased the induction time. Increased content polar fraction in the interesterified fatty product can reduce its resistance to oxidation. FT-IR data of selected spectral ranges correlate with the value of induction time at a statistically significant level. This is a proof that chemical changes occurring during different treatments of the starting mixture can be monitored by FT-IR spectroscopy. Moreover, obtained correlations can be used for the evaluation of an induction value of an unknown oil sample.  相似文献   
47.
48.
The aim of this research was to analyse composition, fatty acids distribution and oxidative stability of fats extracted from four samples of baby formulas. The fats were oxidized in a differential scanning calorimeter (DSC) under polythermal (dynamic) conditions and at normal pressure. The DSC experiments were carried out in an oxygen flow atmosphere using different, linearly programmed, heating rates in the range of 4?C12.5?°C/min. The extrapolated onset temperatures were determined using DSC exotherms and used for the assessment of the thermal oxidative stabilities of the samples. Activation energies (E a), pre-exponential factors (Z) and reaction rate constants (k) for oil oxidation under DSC conditions were calculated using the Ozawa?CFlynn?CWall method and the Arrhenius equation. The melting characteristics of the studied fats were obtained. The fats extracted from the agglomerated samples with higher onset temperatures were more stable than the fats extracted from the initial samples of baby formulas.  相似文献   
49.
A surgical site infection (SSI) is an infection that occurs after surgery in the part of the body where the surgery took place. An SSI may range from a spontaneously limited wound discharge within 7–10 days of an operation to a life‐threatening postoperative complication, such as a sternal infection after open heart surgery. Most SSIs are caused by contamination of an incision with microorganisms from the patient's own body during surgery. From the analytical point of view, the complex nature of these samples as well as the low concentrations of analytes require a system with high sensitivity and efficiency. Such situation requires a technique such as CE, which is a powerful and versatile separation technique that promises to rival HPLC when applied to the separation of both charged and neutral species. During the study, it has been demonstrated that CZE identifies characteristics of such groups of pathogens such as bacteria Gram (+) and different species of bacteria Gram (?), and also develops weekly individual profiles for patients after application of antibiotics. This was done in order to show the impact of antibiotic therapy in change “numbers” of bacteria present in the wound after surgery. The method proved to be the ideal straight specificity in the case of Escherichia coli (100%). Finally, analysis of the spectra and the second derivatives of the UV‐Vis spectra confirmed the similarity in the profiles and showed that the CZE is a great method for fast screening test in bacterial infection.  相似文献   
50.
Emissions from idle truck engines are a main source of pollution at container terminals. In this study, we focus on reducing such emission from waiting trucks as well as the related crane operations with a new truck arrival control method that gives individual truck limited time slots for entry. We develop a method to optimize the time slot assignment for individual trucks, aiming at minimizing total emissions from trucks and cranes at import yards. The method applies discrete event simulation to estimate total truck waiting times and crane moving distance, and then applies a genetic algorithm to minimize the generated emissions from these trucks and cranes. The experiment result shows that the truck arrivals should be controlled based on the stacking of import containers, and that such control is necessary for reducing truck idling emissions at a congested container terminal.  相似文献   
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