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The evolution of reaction phases formed in diffusion-bonded SiC/Ta–5W/SiC joints was investigated at a joining temperature of 1500–1700 °C for 10–90 min. The effects of bonding temperature and holding time on the phase evolution were found to be directly correlated with the thickness of the interfacial reaction layer when a 100-μm-thick Ta–5W interlayer was used for joining. In the case of a ~7-μm-thick reaction layer, the interfacial phase constitution consisted of a layered SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)2Si/(Ta,W)xSiy/Ta–5W structure. In the reaction layer with a thickness of ~11–26 μm, the interfacial structure evolved into SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C/(Ta,W)xSiy/(Ta,W)2Si/(Ta,W)xSiy/Ta–5W, in which an additional (Ta,W)C/(Ta,W)xSiy layer was inserted between (Ta,W)5Si3 and (Ta,W)xSiy owing to the precipitation of carbon from the (Ta,W)5Si3 layer. When the Ta–5W interlayer was fully consumed to form a stable reaction product, namely the equilibrium state, (Ta,W)xSiy and (Ta,W)2Si were eventually transformed into (Ta,W)5Si3, and the final interface structure that was obtained was SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C. This achievement will benefit the design, control, and characterization of SiC/metal interfaces.

A simple and rapid gas chromatography-mass spectrometry (GC-MS) method was developed and validated for the simultaneous determination of α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols in vegetable oils. In this study, tedious sample pretreatments like saponification and derivatization, which are commonly used in previously published related methods, were not adopted. Tocopherols and tocotrienols were isolated from oil samples by ultrasonic extraction with methanol, then centrifuged and the supernatant was directly injected into the GC-MS system for analysis. The results showed that α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols were well separated within 14 minutes. The instrumental limits of detection and quantification ranged from 0.3 to 2.5 ng mL−1 and from 1.0 to 8.3 ng mL−1, respectively. Calibration curves were well correlated (r2 > 0.99) within the concentration range of 10 to 1000 ng mL−1 for all eight compounds. Recovery tests were carried out by spiking virgin olive oil with standards at three concentration levels (10, 50 and 250 mg kg−1), in which the average recoveries (n = 6) varied from 83.7% to 117.2%, with relative standard deviations ranging between 1.9% and 7.5%. The proposed method proved to be simple, sensitive and accurate, and was successfully applied to the determination of tocopherols and tocotrienols in vegetable oils.

A modified quick, easy, cheap, effective, rugged, and safe sample preparation method combined with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI/MS) has been developed for the determination of 7 dinitroaniline herbicide residues in complex matrices (garlic, olive oil, scallion, leek and chili). Dinitroaniline residues were extracted with hexane-saturated acetonitrile. After the cleanup with the dispersive solid-phase extraction, the extract was analyzed by GC–NCI/MS in selected ion monitoring mode. Two isotope internal standards (trifluralin-d 14 and pendimethalin-d 5) were employed for quantification. Compared with electron ionization (EI) mode, the superiorities of NCI in sensitivity and selectivity were investigated. Limits of the detection of 7 dinitroanilines were in the range of 0.014–0.096 μg kg−1, and there were no interfering peaks (unlike in EI) in the complex matrices. Recoveries of 7 dinitroanilines in five matrices at three spiked levels (10, 20 and 40 μg kg−1) ranged from 61 to 126 % and the relative standard deviations were all below 12 %.

An analytical method with the technique of QuEChERS (quick, easy, cheap, effective, rugged and safe) and gas chromatography (GC)/mass spectrometry (MS) in negative chemical ionization (NCI) has been developed for the determination of 17 pyrethroid pesticide residues in troublesome matrices, including garlic, onion, spring onion and chili. Pyrethroid residues were extracted with acidified acetonitrile saturated by hexane. After a modified QuEChERS clean-up step, the extract was analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode. An isotope internal standard of trans-cypermethrin-D(6) was employed for quantitation. Chromatograms of pyrethroids obtained in all these matrices were relatively clean and without obvious interference. The limits of detection (LODs) ranged from 0.02 to 6 μg kg(-1) and recovery yields were from 54.0% to 129.8% at three spiked levels (20, 40 and 60 μg kg(-1) for chili, and 10, 20 and 30 μg kg(-1) for others) in four different matrices depending on the compounds determined. The relative standard deviations (RSDs) were all below 14%. Isomerization enhancement of pyrethroids in chili extract was observed and preliminarily explained, especially for acrinathrin and deltamethrin.

A liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of chloramphenicol (CAP) in royal jelly. Royal jelly samples were first denatured with lead acetate solution, and the CAP was extracted with solid-phase extraction before separation by liquid chromatography. A triple-quadrupole mass spectrometer operated in the negative electrospray ionization and selected-reaction monitoring mode was used for the detection of CAP. For method validation, royal jelly samples were fortified at CAP levels between 0.1 and 10.0 μg/kg; at these levels, recovery values (internal standard-corrected) ranged from 93.3 to 105.0%, and the within-laboratory reproducibility (relative standard deviation) was ≤9.1%. The decision limit was 0.07 μg/kg, and the detection capability was 0.1 μg/kg.