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- Author or Editor: D. Zhou x
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Abstract
A new compound cyclohexyl-t-butyldimethylammonium tetraphenylborate, [C6H11N(CH3)2(C(CH3)3)]BPh4 has been prepared, and its decomposition mechanism was studied by TG. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis for the first stage of thermal decomposition process was obtained by TG and DTG curves, and kinetic parameters were obtained from the analysis of the TG-DTG curves with integral and differential equations. The most probable kinetic function was suggested by comparison of kinetic parameters.
Abstract
A new method for the analysis of thermal desorption spectra is presented, based on the experimental peak maximum functions for temperatureT m(β) and pressureP m(β) and a rigorous mathematical treatment. The resonant heating rate βr is determined, satisfyingT m(βr)=T r, whereT r is the resonant temperature defined byA exp(−E d/(RT r))=1. Desorption energyE d and frequency factorA can be determined simultaneously with relatively high robustness towards statistical experimental errors as demonstrated by computer-simulated thermal desorption spectra.
Photoinitiating behavior of macrophotoinitiator containing aminoalkylphenone group
Free-radical polymerization
Abstract
Photoinitiating behaviors of oligo(α-aminoketones) (OAK) macrophotoinitiator containing aminoalkylphenone group on free-radical photopolymerization had been investigated by differential photo-calorimetry (DPC). The macrophotoinitiator showed comparative performance with those commercial photoinitiators with lower molecular mass. The effect of photoinitiator concentrations and UV intensity on the polymerization rate was investigated, and the value of exponential factor was found to be 0.5 at the beginning of polymerization, suggesting that the photopolymerization initiated by OAK followed biradical termination mechanism. Photosensitizer isopropyl thioxanthone (ITX) and oxygen severely restricted the polymerization in these systems. Photoinitiators with lower molecular mass showed higher reactivity than those with higher molecular mass.
Abstract
Although Ir anomaly has been discovered in a number of C/T boundaries in the world, no positive results of this anomaly in Permian/Triassic (P/Tr) boundary were given. There are many well-developed P/T sections in South China. One of representative sections is located at the Baoqing quarry, Meishan Town, Changxin County, Zhejiang Province. Ir, Os, Re, Au, Pt, Cu and Mo were determined by the radiochemical procedure developed in our laboratory. (1) Besides those accessible by INAA. The results reveal that the refractory siderophile and other chalcophile elements have certain enrichment near and at the boundary layer. However, the Ir/Au and other element abundance ratios fail to accord with the extraterrestrial values. The nature of the boundary event was discussed in terms of elemental geochemistry.
Abstract
The paper presents the results of determination of extractable organohalogens (EOX) by instrumental neutron activation analysis (INAA), and polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) by gas chromatography (GC), in atmospheric precipitation in Shanghai, China, from January to August 2005. The results showed that EOCI was the major component of organohalogens in precipitation. A significant correlation between the concentrations of EOBr and EOI was observed (r 2 = 0.75), which suggested that EOBr and EOI in precipitation might mainly come from the same sources. There were no clear seasonal trends for the concentrations of EOX. The concentrations of ΣPCBs ranged from 0.2–2.8 ng/l, with the dominant PCBs containing 3 to 5 chlorine atoms. HCH was the predominant pesticide in precipitation, accounting for over 80% of total OCPs, in which β-HCH took 28%–72% of total HCH. Also, there may be an evidence for significantly historical usage of DDT.
Summary
Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and l-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.
Summary
A new HPLC method has been established for determination of 3-monoiodotyrosine (MIT), 3,5-diiodotyrosine (DIT), 3,5-diiodothyronine (T2), 3,3′,5-triiodothyronine (T3), 3,3′,5′-triiodothyronine (rT3), and thyroxine (T4) produced by hydrolysis of iodinated casein with barium hydroxide. The hydrolytic stability of each analyte was evaluated. Iodinated casein was hydrolyzed with saturated barium hydroxide solution for 16 h at 110°C and the barium ions were then removed as barium sulfate. Reversed-phase HPLC was performed on a 2.1 mm × 150 mm, 5 μm particle, C18 column with a mixture of acetonitrile and 0.1% (v/v) formic acid as mobile phase at a flow rate of 0.2 mL min–1. Acetonitrile was maintained at 5% (v/v) for 5 min and then increased linearly to 50% (v/v) within 35 min. All analytes were quantified by measuring the absorbance at 280 nm. Validation data indicated the method was linear, with regression coefficients (R 2) > 0.998, in the concentration ranges investigated. Sensitivity was adequate—limits of detection (LOD) were 0.04–0.38 μg mL–1 and limits of quantification (LOQ) were 0.05–0.38 μg mL–1. Accuracy and precision were acceptable — for all the analytes recovery was 82.0–93.0% and repeatability, as relative standard deviation, was 1.0–3.0%. Hydrolytic stability tests indicated MIT and DIT are much more stable than the other analytes. rT3 was not released directly from iodinated casein but was formed by deiodination of T4 during hydrolysis. The method could be used to identify iodinated casein, to evaluate its activity and quality, and for supervision and regulation of feed additives.
Summary
Effects of ionic strength and of fulvic acid on the sorption of Eu(III) on alumina were investigated by using a batch technique. The experiments were carried out at T=25±1 °C, pH 4-6 and in the presence of 1M NaCl. The results indicate that sorption isotherms of Eu(III) are linear at low pH values. The sorption-desorption of Eu(III) on alumina at pH 4.4 is reversible, but a sorption-desorption hysteresis is found at pH 5.0. Fulvic acid has an obvious positive effect on the sorption of Eu(III) on alumina at low pH values. The migration of Eu(III) in alumina was studied by using column experiments and 152+154Eu(III) radiotracer at pH 3.8. For column experiments, Eu(III) sorbed on alumina can be desorbed completely from the solid surface at low pH values. The findings are relevant to the evaluation of lanthanide and actinide ions in the environment.
Summary
Radix Isatidis has widely useful activities including anti-virus, anti-bacterial. Tryptanthrin, indigo, and indirubin are active ingredients in R. Isatidis. Response surface methodology (RSM)-optimized infrared-assisted extraction (IRAE) was developed and combined with HPLC for simultaneous determination of tryptanthrin, indigo, and indirubin from R. Isatidis. IRAE were investigated through extraction yields of the three components and optimized by RSM. The optimum conditions were as follows: infrared power of 129 W, solid/liquid ratio of 1:40 g/mL, and irradiation time of 22.5 min. IRAE conditions obtained by RSM were not only accurate, but also had practical value reflecting the expected optimization. Subsequently, this novel IRAE method was evaluated by extraction yield of the components of R. Isatidis samples from different regions. Compared with common extraction methods including maceration extraction (ME), reflux extraction (RE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), IRAE showed higher yield with advantages of no limitation of solvent selection, low cost, convenience under optimum extraction conditions. These results suggested the potential of RSM-optimized IRAE for extraction and analysis of the water-/fat-soluble compositions of Chinese herbal medicine. A simple chromatographic separation for simultaneous determination of tryptanthrin, indigo, and indirubin from Chinese herbal medicine R. Isatidis was performed on a C18 column (Diamonsil 150 mm × 4.6 mm i.d., 5 μm) with a mobile phase isocratic consisting of methanol and water at a flow-rate of 0.8 mL min−1. The retention times of tryptanthrin, indigo, and indirubin were 15.4, 31.9, and 58.6 min, respectively. The linear equations were obtained as follows: y = −3094.5744 + 21208.792x for tryptanthrin (R = 0.9998, 0.9–18.0 μg mL−1), y = 4730.0448 + 30180.567x for indigo (R = 0.9997, 0.5–10.0 μg mL−1) and y = −6582.9045 + 67069.312x for indirubin (R = 0.9997, 0.4–8.0 μg mL−1). The result showed that RSM-optimized IRAE was a simple, efficient pretreatment method for the analysis of complex matrix.
A rapid and sensitive ultraperformance liquid chromatography-multiple reaction monitoring-multi-stage/mass spectrometry (UPLC-MRM-MS/MS) method has been developed for simultaneous quantification of salvianolic acid B and tanshinone IIA of salvia tropolone tablets in dog plasma. This was achieved by performing quantification using the MRM acquisition with two channels of MRM-MS/MS and MS full scan for more accuracy qualitative results, and the fragmentation transitions of m/z 295→249, 191 for tanshinone IIA and m/z 297→279, 251 for IS in positive mode, m/z 717→519, 321 for salvianolic acid B and m/z 295→267, 239 for IS in negative mode were selected. The UPLC separation was achieved within 3 min in a single UPLC run. Linear calibration curves were obtained over the concentration range of 10 pg/mL−1 ng/mL for tanshinone IIA and 100 pg/mL−1 for salvianolic acid B. Lower limit of quantitation (LLOQ) was 10 pg/mL and 100 pg/mL for tanshinone IIA and salvianolic acid B, respectively. The inter-day and intra-day precision (relative standard deviation, RSD) in all samples were less than 8.21%, and the recoveries were over 85.9% for both tanshinone IIA and salvianolic acid B. The two channels of MRM with MS full scan approach could provide both qualitative and quantitative results without the need for repetitive analyses and resulted in the reduction of further confirmation experiments and analytical time. The pharmacokinetic study of the two active components of salvia tropolone tablets following oral gavage administration of dogs was thus explored with this method.
