Development and validation of a capillary electrophoresis method for determination of enantiomeric purity and related substances of esomeprazole in raw material and pellets

A capillary electrophoresis method using CDs for quality control of esomeprazole (ESO) in terms of enantiomeric purity and related substances in raw material and pellets was developed. ESO is the S‐enantiomer of omeprazole (OMZ). Several parameters were evaluated, including type and concentration of buffer and CD, concentration of additives and electrolyte pH. Resolution between the enantiomers of OMZ obtained for each parameter tested was calculated and the presence of the main related substance such as OMZ sulfone was carefully monitored. The optimized system consisted of 100 mM Tris‐phosphate buffer pH 2.5 with 20 mM 2‐hydroxypropyl‐β‐CD, 1 mM sodium dithionite, temperature at 15°C, voltage at 28 kV, and UV detection at 301 nm. Once optimized, the electrophoretic system was validated according to ICH guidelines. The limits of detection and quantification for R‐OMZ were 0.6 μg/mL (0.06% w/w of ESO) and 2.0 μg/mL (0.2% w/w of ESO), respectively. A mean concentration of R‐OMZ <0.2% limit established by the United States Pharmacopeia (USP) was found in the raw material and six‐pellet samples of ESO. No other impurities were found in the samples under these conditions. Therefore, the developed method was found to be appropriate not only for enantiomeric quality control of ESO but also for the analysis of ESO and the main related substance in raw material and pharmaceutical formulations as well as for stability indicating studies.     

Effect of pentaerythritol and organic tin with calcium/zinc stearates on the stabilization of poly(vinyl chloride)

The stabilization effect of calcium and zinc stearates (CaSt₂/ZnSt₂) combined with pentaerythritol (PeE) and organic tin on poly(vinyl chloride) was investigated. The results show that the addition of calcium/zinc stearates combined with PeE and organic tin can improve thermal and colour stability of poly(vinyl chloride) in both static and dynamic tests. Mechanisms for improving stability of PVC are also discussed. The increase of stabilizing effectiveness of calcium/zinc stearates is ascribed to the synergistic effect between CaSt₂/ZnSt₂ and PeE and the interaction between organic tin and double bonds formed during the degradation of PVC. There is no synergistic action between organic tin and PeE or organic tin and calcium/zinc stearates.     

Thermal oxidation of oxynitride perovskites in different atmospheres

Oxynitride perovskites with bright and variable colour have the potential to be employed as non-toxic pigments, and to substitute colourants that contain harmful heavy metals. For this application it is extremely important to have a precise knowledge about the materials stability. The thermal stability of oxynitride perovskites in different atmospheres was measured by thermogravimetry in combination with mass spectroscopy (MS). The studied compounds, namely LaTiO₂N, SrNbO₂N and SrTaO₂N, were heated up to 1200 °C in argon–oxygen mixtures with varying oxygen contents. It was found that the thermal behaviour of the studied oxynitrides changes drastically with the oxygen concentration. When heated up in pure argon the oxynitrides transform to oxides containing transition metals of lower oxidation state and/or binary nitrides. For oxygen contents between 0.5% and 20% the samples were completely oxidised. The oxidation rate increases with oxygen content. MS analysis of the gaseous products (including N₂, NO and NO₂) reveals a complex reaction mechanism, which is strongly modified by the composition of the atmosphere.     

Effect of stabilizers in the thermal treatment of PVC—XII.: An I.R. spectroscopic study of the complexation of Na and Zn stearates in PVC

Effect of the 2:1 combination of Na and Zn stearates on the stabilization of PVC exposed to thermal stress at 180° in air has been studied by i.r. spectrometry (1900?1350 cm^?1) and by determination of Zn, Na and Cl^? in the decomposition products of the stearates (NaCl, ZnCl₂). Complexation of both components in PVC mixtures proceeds very easily; a 2:1 complex is the only one formed in the mixture. One stearate (Na) of the binary mixture is consumed selectively over a substantial part of the thermal stability period. The stearate mixture studied has no significant synergistic effect.     

Color Stabilization of Polyvinyl Chloride) with Heat Treatment

Stabilization of polyvinyl chloride) (PVC) containing metal soaps was investigated by psychophysical colorimetry. A color difference observed among heated PVC films containing various metal salts depends on coloration of the π-complex of polyene with metal chloride converted from the metal salt added and that the stabilization effect of synergistic soaps should be based on an effect of complementary colors set up among a polyene color and metal chloride-polyene complex colors. These conclusions are well supported by colorimetry of heated PVC films containing various dyes. The color of heated PVC films containing Zn/Ca and Cd/Ba synergetic soaps markedly deviated from a polyene color with increased heat treatments, owing to greater degree of coloration of Zn complex and Cd complex, respectively. These color deviations usually decrease the thermal stability of PVC. The thermal stability of PVC was markedly improved by the use of synergetic soaps together with masking agent such as triethanolamine, urea, N,N′-dimethylol-urea, and vinylpyridine-methylmethacrylate copolymer, owing to the masking effect of these nitrogen-containing compounds. These masking agents did not slow down the dehydrochlorination of PVC.     

二苯胺-4-偶氮磺酸盐及其树脂的制备和光、热分解性质

从二苯胺 4 重氮盐(DS)和3 甲氧基二苯胺 4 重氮盐(MDS)以及重氮树脂(DR)和硝基重氮树脂(NDR)与亚硫酸钠反应,在水溶液中制备了相应的二苯胺 4 偶氮磺酸盐DSS和MDSS(简称偶氮磺酸盐)及相应的重氮树脂的偶氮磺酸盐DRS和NDRS(简称偶氮磺酸盐树脂).对它们在水溶液和固相膜中的光、热反应进行了研究.结果表明偶氮磺酸盐与偶氮磺酸盐树脂有很好的感光性能,而热稳定性比相应的重氮盐和重氮树脂好很多,其中二苯胺上有硝基取代的偶氮磺酸盐树脂具有突出的热稳定性,其水溶液在70℃加热6h,其固相膜在100℃加热11天几乎观察不到分解.对偶氮磺酸盐及偶氮磺酸盐树脂的光、热分解机理作了初步分析.     

Metal dicarboxylates as thermal stabilizers for PVC

Different metal dicarboxylates such as calcium glutarate, zinc glutarate, calcium sebacate and zinc sebacate were investigated in this paper as thermal stabilizers (without and with calcium stearate and pentaerythritol as costabilizers) of poly(vinyl chloride) (PVC). The thermal stability of the PVC films was determined by two different methods which are visual color comparison and measurement of HCl release from heated pellets. Both zinc dicarboxylates and calcium dicarboxylates exhibited good thermal stability. With respect to stabilizing performance, zinc glutarate (ZnGa) was more effective than zinc sebacate (ZnSe), particularly in the presence of a large amount of pentaerythritol. Similarly, calcium glutarate (CaGa) was more effective than calcium sebacate (CaSe). And the relative order of stabilizing effectiveness of metal dicarboxylates was as follows: CaGa > CaSe > ZnGa > ZnSe. Moreover, the Ca-Zn complex thermal stabilizer and the Pe-Zn complex thermal stabilizer were also studied. It was found that no more than 20% of the zinc compound exhibited better stabilizing performance.     

Synthesis and Thermal Properties of Epoxidized Vegetable Oil

Summary: The novel potential epoxy resins, epoxidized soybean oil (ESO) and epoxidized castor oil (ECO), were synthesized and characterized. The cationic polymerization of ESO and ECO with a latent thermal catalyst, N‐benzylpyrazinium hexafluoroantimonate (BPH), was initiated at 80 and 50 °C, respectively. The cured ECO samples showed a higher T_g and lower coefficient of thermal expansion than those of ESO, due to the higher intermolecular interaction in the ECO/BPH system.

Relationships between ESO or ECO conversion and temperature in the polymerization with 1 wt.‐% BPH for 2 h.     

The Influence of Temperature,Storage Conditions,pH, and Ionic Strength on the Antioxidant Activity and Color Parameters of Rowan Berry Extracts

Recent trends in the food industry combined with novel methods in agriculture could transform rowan into a valuable raw material with potential technological applications. Thus, the aim of this research was to investigate the content of bioactive compounds in its fruits and to assess the color and antioxidant stability of the extracts prepared from such fruits during various thermal treatments and at different pH and ionic strength values. Various spectrophotometric methods, HPLC, and capillary electrophoresis were used to quantify the concentrations of bioactive compounds—polyphenols, carotenoids, organic acids, and to assess antioxidant activity and color. The results show that rowan berries contain circa 1.34–1.47 g/100 g of polyphenols among which include catechin, epicatechin, ferulic acid methyl ester, procyanidin B1, etc.; ca 21.65 mg/100 g of carotenoids including zeaxanthin, β-cryptoxanthin, all-trans-β-carotene, and various organic acids such as malic, citric, and succinic, which result in a high antioxidant activity of 5.8 mmol TE/100 g. Results also showed that antioxidant activity exhibited high stability when the extract was subjected to various thermal treatments, pHs, and ionic strengths, while color was mainly impacted negatively when a temperature of 100 °C was employed. This data confirms the technological potential of this traditional, yet often overlooked species.     

Structure and properties of partially epoxidized soybean oil

In the present study, the characteric-structure relationship of epoxidized soybean oils (ESO) with various degrees of epoxidation has been investigated. FTIR analysis was used to identify the relative extent of epoxidation of the samples during the epoxidation reaction. The viscosities of ESO were much higher than that of the raw oil, viscosity increased with degree of epoxidation. The viscous-flow activation energy of ESO was determined to be higher than that of the raw oil (20.72 to 77.93% higher). Thermogravimetry analysis (TG) of ESO was used to investigate the thermodynamic behavior of the samples. With increasing degree of epoxidation, the thermal stability of the samples initially decreased, then increased at the final reacting stage. Differential scanning calorimeter (DSC) indicated that the melting point of ESO was higher than that of soybean oil. Gel permeation chromatography (GPC) indicated the molecular mass of the samples increased initially, then decreased, with an increase in the extent of epoxidation.     

Influence of different curing systems on the physico-mechanical properties and stability of SBR and NR rubbers

The physical properties of radiation, sulfur and peroxide-cured styrene–butadiene rubber (SBR) and natural rubber (NR) were compared. The dependence of the mechanical properties of the radiation-vulcanized SBR and NR on the coagent concentration and radiation dose was studied. The effect of thermal aging on the mechanical properties of the different rubber formulations was discussed. The radiation-cured formulations of SBR have superior mechanical properties and thermal stability compared with those of the chemically vulcanized compounds. Whereas, the radiation-cured formulations of NR have similar mechanical properties but superior thermal stability (based on the % change in E after thermal aging), when compared with those of the sulfur-vulcanized compounds and slightly better than those of the peroxide-vulcanized compounds.     

Bio‐based nanocomposites composed of photo‐cured epoxidized soybean oil and supramolecular hydroxystearic acid nanofibers

A mixture of epoxidized soybean oil (ESO), (R)‐12‐hydroxystrearic acid (HSA) and a photoinitiator for cationic polymerization in the ESO/HSA weight ratio 10/1 was heated to 100 °C and gradually cooled to room temperature to give bio‐based gelatinous material. The photo‐curing of the gel afforded a nanocomposite composed of crosslinked ESO and supramolecular HSA nanofibers. The transmission electron microscopy observation of the photo‐cured ESO/HSA revealed that dendritic clusters of HSA nanofibers are formed in the crosslinked ESO matrix. In the differential scanning calorimetry chart of the ESO/HSA, a thermal transition from the mesophase composed of supramolecular nanofibers to isotropic state was observed at 67 °C (ΔH = 22.6 J/g‐HSA), while the T_m of crystalline HSA is 77.7 °C (ΔH_m = 159 J/g‐HSA). Tensile strength at 20 °C of the ESO‐HSA was ～80% higher than that of photo‐cured ESO without HSA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 669–673, 2009     

The thermal behaviour of BTAw, a high nitrogen fuel

BTAw (bis-(1(2)H-tetrazol-5yl)-amine monohydrate) has recently been considered for use as a low-smoke pyrotechnic fuel. There is relatively little information available in the literature concerning the thermal properties of BTAw or its precursors. In the present work, various thermoanalytical experiments were performed on BTAw and BTA (bis-(1(2)H-tetrazol-5yl)-amine) in an effort to better characterize the thermal stability and decomposition of these compounds. Variable heating rate studies were carried out on BTAw samples in a helium atmosphere using DSC and TG. Two steps were seen in the results: dehydration followed by decomposition. Kinetic parameters were determined for both of these steps using a number of methods. Experiments using simultaneous TG-DTA coupled with FTIR and MS were performed on BTAw in both helium and dry and CO₂ free air atmospheres, and evolved gas analysis was used to determine the gaseous decomposition products. The thermal stability of BTAw and BTA was examined using accelerating rate calorimetry (ARC).     

Degradation kinetics and solvent effects of various long-chain quaternary ammonium salts

Surfactants such as quaternary ammonium salts (QAS) have been in increasing demand, for emerging new applications. Recent attempts at process intensification of their production have disclosed the need for a better understanding of QAS thermal stability. This work aims to determine the degradation kinetics of various QASs and the associated solvent effects. The degradation kinetics of four methyl carbonate QASs were determined in various polar solvents in stainless steel batch autoclaves. H NMR spectrometry was employed for offline analysis of the reaction mixtures. The kinetic parameters were then used to compare the thermal stability of the four compounds in the polar solvents. Water showed no degradation, and methanol (MeOH) was the solvent that provided the second-best stability. Water–MeOH mixtures may provide an overall optimum. Moreover, and longer long-chain substituents increased the degradation rate. Thermogravimetric analysis was used to obtain the thermal stability in a solid state, that is, solventless environment. Isoconversional analysis showed that no reliable kinetic parameters could be determined. Nevertheless, the data did allow for a comparison of the thermal stability of 14 different QASs. Furthermore, the relative instability of the compounds in the solid state demonstrated the challenges of solventless QAS production.     

Investigations of imidization of polypyromellitamido acids and thermal degradation of polypyromellitimides by mass spectrometric thermal analysis

Processes occurring when samples of fibers of polypyromellitamido acids and polypyromellitimides based on them are heated in vacuum have been investigated by mass spectrometric thermal analysis (MTA) over a wide temperature range.A combination of MTA methods with a comparative thermal analysis of polyimides and model compounds permits conclusions to be made concerning the main reactions responsible for the thermal stability and the start of degradation of a number of polyimide structures.     

Thermal, oxidative and radiation stability of polyimides. Part IV: Polyimides based on N-[4-benzoyl-2-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-phenyl]-acetamide and different diamines

Polyimide resins were obtained from the reaction between N-[4-benzoyl-2-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-phenyl]-acetamide and the following compounds with terminal amino groups: urea, 4-[(4-aminophenyl)sulfonyl]aniline, thiourea, 2-aminoethylamine, and 4,4′-diaminodiphenylmethane. The thermal and thermooxidative behaviour of the polyimide resins was studied by thermogravimetric measurements (TG) in oxygen and nitrogen. Polyimide resins have been irradiated (500 kGy) and their radiation stability evaluated on the basis of thermal and thermooxidative behaviour of irradiated samples.The thermal and oxidative degradation of the examined polyimides is complex and occurs in two phases. The first step occurs in both nitrogen and oxygen but it is somewhat less pronounced in oxygen due to oxidation and formation of more stable products. All samples showed very good radiation stability and there is almost no change in the first degradation step while the span of the peaks in the second step is narrowed and temperatures are slightly lower.     

Effect of stabilizers in the thermal treatment of PVC—IX. An investigation of the loss of Ba and Cd stearates from their equimolar mixture during static thermal stress of PVC—IX

Thermal degradation at 180° in air of PVC stabilized with an equimolar mixture of Ba and Cd stearates has been studied. The “unreacted” stearates were separated by filtering tetrahydrofuran solutions of samples. The filtration and thermal degradation were examined by means of infrared spectroscopy in the range 1400–1800 cm^?1. It has been demonstrated that, during the thermal stress, CdCl₂ is accumulated in the sample and that the presence of Ba stearate supports only the consumption of Cd stearate.     

Plasticizers,antioxidants, and other contaminants found in air delivered by PVC tubing used in respiratory therapy

Of the many compounds that leach from respiratory therapy tubing into air passing through it, we selected five compounds to analyze. The five compounds are known to be potentially carcinogenic, toxic or known to induce estrogenic activity. Parts-per-million and parts-per-billion concentrations of these species were found in the air passing through the tubing: the plasticizers di-(2-ethylhexyl) phthalate (DEHP) and di-ethyl phthalate (DEP), the antioxidants butylated hydroxy toluene (BHT) and p-nonylphenol (p-NP), and the contaminant (from commercial preparation of DEHP) 2-ethylhexanol (2-EH). These levels are high enough to cause some concern about exposure for patients who use oxygen on a long-term basis, those sensitive or allergic to these species, or those with asthma. A method was developed for analysis of solid tubing samples, showing great variability in concentrations of small, volatile molecules from sample to sample. A method was also developed for pre-concentration of small molecules onto Tenax adsorbants from air passing through the tubing. Both solid samples and adsorbant loaded with analyte were analyzed by direct dynamic thermal desorption gas chromatography mass spectrometry (GCMS). This study does not imply that adverse reactions by patients to chemical compounds leaching from respiratory medical tubing will occur but that further investigation is warranted.     

Effect of stabilizers in the thermal treatment of PVC—XI.: Effect of the reaction products on the stability of PVC mixtures stabilized by barium and cadmium stearates

The effects of cadmium and barium chlorides and stearic acid on the thermal stability of PVC mixtures stabilized by barium and cadmium stearates respectively and by their equimolar combination have been studied under static conditions of thermal treatment at 180° in air. The stabilizing effect of cadmium stearate drops in the presence of stearic acid owing to the formation of higher co-ordination cadmium compounds, only formed in the simultaneous presence of cadmium chloride, stearic acid and hydrogen chloride. The synergism is thought to be associated with the possibility of formation of a complex compound of barium stearate with cadmium chloride or stearic acid.     

In situ generation of nitroxide from alkoxyamines for controlled acrylate polymerization

A general strategy for the controlled nitroxide-mediated polymerization of acrylates from alkoxyamines without addition of excess free nitroxide is outlined. 2,2-Dimethyl-3-(1-phenylethoxy)-4-phenyl-3-azapentane ( 1 ), prepared in one pot by the addition of 1-phenylethyl radicals to 2-methyl-2-nitrosopropane, is heated prior to the addition of monomer to afford a mixture of alkoxyamine 1 , free nitroxide, and 2,3-diphenylbutane. With a 30 min preheating period at temperatures up to 125 °C, the kinetics of the subsequent polymerization of n-butyl acrylate at 125 °C appear largely unaffected, though the ultimate molecular weight of the polymers is dependent upon the preheating temperature. The poly(n-butyl acrylate) samples, that result from this process, have much narrower molecular weight distributions than those which result in the absence of the preheating process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5128–5136, 2006