A reciprocating magnetic field assisted on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry determination of trace tetracyclines in water

A reciprocating magnetic-field-assisted on-line solid-phase extraction (RMF-SPE) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for continuous enrichment of trace chemicals in water samples. Under the assist of the reciprocating magnetic field, carboxyl-modified magnetic nanoparticles (CMNPs) were applied to prepare microcolumn with even dispersion by periodical motion, instead of traditional compaction as extraction sorbents. When water sample passed through the extraction region, dynamic sorbents generates an advantage of countless contacts between sorbents and targets without blocking for high efficient extraction. In this study, the on-line RMF-SPE method was established and evaluated by determination of tetracyclines (TCs) from water samples as analysis models, including oxytetracycline, tetracycline, demeclocycline, metacycline, chlortetracycline, and doxycycline. Experimental conditions have been investigated such as flow rate, reciprocating speed, elution time, and so on. The method showed high relative recovery (95.4-111.1%) and good repeatability with RSD from 2.9 to 11.8% for the 200 mL water sample. The linearity range, limits of detection (LODs), and limits of quantification (LOQs) were 0.5-200 μg L^-1 (chlortetracycline) and 0.1-200 μg L^-1 (other TCs), 12.0-74.1 ng L^-1, and 40.1-247 ng L^-1, respectively. More importantly, the high enrichment factors in a range of 204 (chlortetracycline) to 276 (demeclocycline) indicate that a small amount of dynamic sorbents (only 10 mg) give full play to extraction attributing to the reciprocating movement, especially for trace analysis and continuous extraction, which is significant for water samples from sea, river and domestic waste.

Formation enthalpies and dilute heats of HCP-HCP disordered binary alloys: modified ones of embedded atom method potentials

The formation enthalpies and the dilute heats of HCP-HCP disordered binary alloys were evaluated by employing the improved ones of the modified analytic embedded atom method (EAM) potentials for HCP metals. We calculated the formation enthalpies according to the concentration of alloy elements for 36 kinds of HCP-HCP disordered binary alloys by using the modified ones of embedded atom method potentials for HCP metals proposed by Jin et al. (Appl. Phys. A120, 2015, 189), Johnson's alloy potential model, and Vegard's law. We derived the formulas to calculate the dilute heats of HCP-HCP binary alloys and evaluated the dilute heats for 56 kinds of HCP-HCP disordered binary alloys. The present results of the formation enthalpies and the dilute heats for HCP-HCP binary alloys are basically consistent with the experimental data, the first principle calculations, and the calculations by Miedema theory. Our results agree with the available experimental results better than the modified analytic EAM calculation results.

Simultaneous determination of multiple phytohormones in tomato by ionic liquid-functionalized carbon fibers-based solid-phase microextraction coupled with liquid chromatography-mass spectrometry

Phytohormones are interrelated by synergistic or antagonistic crosstalk and play important roles in the regulation of plant growth and development. In order to understand the interaction between phytohormones in the plant physiological network, it is necessary to determine trace levels of multiple phytohormones simultaneously in a complex matrix. Here, we synthesized ionic liquids containing different functional groups and modified the surface of carbon fibers with them. Based on these carbon fibers-ionic liquid (CFs-IL) materials, a solid phase microextraction method was developed to enable the simultaneous extraction of phytohormones. The adsorption specificity of multiple phytohormones was studied by identifying the hydrophobic, electrostatic, and π-π interactions, as well as hydrogen bonds, which favor simultaneous extraction of the relevant acidic, alkaline and neutral phytohormones by improving compatibility. The proposed method, coupled with liquid chromatography-tandem mass spectrometry, was applied to the simultaneous determination of 13 acidic, alkaline and neutral phytohormones in tomato. The limits of quantification were found to be in the range of 0.32-54.05 ng mL^-1 and 4.6-185.8 pg mL^-1, respectively, when measured by QQQ and Q-TOF. All of the relative recoveries were in the range of 94.40-113.37% with RSDs ≤15.36% (n = 3) for spiked tomato samples. This method is expected to be widely applied to multiple phytohormones analysis for in-depth researches concerning the physiological networks of plants.

Development of decay energy spectroscopy using low temperature detectors

We have developed a high-resolution detection technique for measuring the energy and activity of alpha decay events using low-temperature detectors. A small amount of source material containing alpha-emitting radionuclides was enclosed in a 4π metal absorber. The energy of the alpha particles as well as that of the recoiled nuclides, low-energy electrons, and low-energy x-rays and γ-rays was converted into thermal energy of the gold absorber. A metallic magnetic calorimeter serving as a fast and sensitive thermometer was thermally attached to the metal absorber. In the present report, experimental demonstrations of Q spectroscopy were made with a new meander-type magnetic calorimeter. The thermal connection between the temperature sensor and the absorber was established with annealed gold wires. Each alpha decay event in the absorber resulted in a temperature increase of the absorber and the temperature sensor. Using the spectrum measured for a drop of (226)Ra solution in a 4π gold absorber, all of the alpha emitters in the sample were identified with a demonstration of good detector linearity. The resolution of the (226)Ra spectrum showed a 3.3 keV FWHM at its Q value together with an expected gamma escape peak at the energy shifted by its γ-ray energy.