Notes

Connection between long-term phosphorus program in plants deliver, phosphorus assimilation, and dirt phosphorus deposition in maize-wheat rotation system.
Developing a green, non-toxic and easy to synthesize of fluorescence probe for fast and visual detecting trace water in various organic solvents was an important task. Here, a novel dual-emission fluorescence probe (b/r-CDs) was designed based on the red CDs (r-CDs) and blue CDs (b-CDs) to detect the trace water and enhance the visualization for naked-eye observation in different organic solvents. Among, the red fluorescence carbon dots (CDs) was found to have the capability to monitor trace amounts of water, which synthesized with green tea by facile ultrasonic method. Further, Such a dual-emission probe could fast monitor trace water in various organic solvents with high stability and fast response. Importantly, a synergistic mechanism of the dynamic process (b-CDs) and static quenching (r-CDs) was proved for the study of water detection. Moreover, the test paper was made for detecting trace water in different organic solvents, achieving convenient and effective detection.A simple, cheap and portable spectrophotometric system is described. It is based on the use of a cheap digital microscope housed from a 3D printed device which simultaneously supports a LED as a light source and a flow cell. A simple electronic device to power the LED is also described using electronic smd components. Both the digital microscope and the power source required to light the LED are connected to the USB ports of a notebook in order to avoid the need of any power source to complete the portable system. This method was applied to make the determination of Fe2+ with o-phenanthroline as chromogenic reagent. The reaction provided the red complex which is used to monitor the analytical response with the digital microscope.Absolute quantitation is always a challenge for in situ analysis of solid samples with ambient liquid extraction mass spectrometry due to unknown sampling efficiencies of analytes from complex solid matrices such as commercial packaging materials. Standards were usually dropped onto the sample surface for signal calibration, but the mass transfer of standards would not be the same as analytes distributed in samples. In this work, an in situ quantitation method via liquid microjunction sampling (LMJSS) coupled with mass spectrometry (MS) for photoinitiators (PIs) in packaging was developed without standard spiking. For direct in situ quantitation, mass transfer kinetic model for LMJSS of solid surface was proposed and validated. Mdivi-1 datasheet Results showed that the detection data well fitted the mass transfer model with adjusted R2 mostly in the range of 0.8-0.9 for 12 PIs in both lab-made mimetic positive samples and commercial packaging samples. According to the mass transfer kinetic model, two-point kinetic calibration method was proposed for calculation of the absolute concentration of PIs in solid samples by LMJSS of the same sample area for two times. The conditions of LMJSS including extraction solvent composition and solvent flowrate were optimized. With the optimized LMJSS-MS method and new calibration method, in situ analysis was done within only 2 min, and detection limits and quantitation limits of 15 PIs in mimetic samples were in the range of 0.06-1.5 mg/m2 and 0.34-6 mg/m2 respectively with relative standard deviation (RSDs) in the range of 2%-26%. The quantitation accuracy by the new calibration method for 13 PIs was in the range of 61%-162%. The method was applied to the quantitation of PIs in commercial packaging samples. 6 PIs were detected and identified in four commercial packaging materials, and the quantitation results were comparable with that by traditional solvent extraction-LC-MS method (relative recovery, 63%-127%).Absorption spectra of pH indicators in aqueous solutions were reproduced from RGB values of microscopic images utilizing principal component analysis (PCA) and linear algebraic treatments. The reproduction of absorption spectra comprises the following three steps (1) determining the loading spectra by PCA, (2) determining the conversion matrix from the RGB values to the score vectors, and (3) reproducing the absorption spectra by linear combination of the loading spectra and the score vectors. The reproducibility of the absorption spectra was demonstrated by employing bromothymol blue and methyl red solutions as pH indicators. The reproduced spectra of both indicators were in good agreement with the spectra measured with a conventional spectrophotometer. The pKa values of both indicators calculated from the reproduced spectra are in good agreement with those obtained from the spectrophotometric spectra and the literature values, confirming validity of the reproduction. This approach was applied to measure pH of freeze concentrated solutions in micro drains formed in ice. A change in pH was successfully observed on freezing and was compared with that reported in previous literature. Since this method does not necessitate the use of grating systems, spectral changes can be traced in milliseconds; this elucidates the phenomena occurring in fluctuating fields.The development of a humidity sensor utilizing vanadium pentoxide xerogel (V2O5·nH2O, VPX) is described. Thin films of VPX were drop-cast onto a low-cost, screen-printed graphite three-electrode electrochemical cell (SPC) and the resulting transducing surface was assessed as a relative humidity (RH%) sensor. The morphology of VPX, its interaction with water vapors as well as the electrochemical properties of VPX/SPC were characterized by scanning electron microscopy, ATR-infrared spectroscopy and electrochemical impedance spectroscopy (EIS), respectively. The sensor possesses high sensitivity (190-500 Ohm/RH%) over a wide range of RH (10-93%), sensor response of 93%, low hysteresis, sufficient storage stability, and a fast response and recovery time, of 52 and 21 s, respectively. EIS data obtained at different RH% values were sufficiently modeled to a single equivalent electric circuit, which describes the conduction mechanism within the VPX film and the electrochemical properties at the electrode/film interfaces. Results demonstrate that the designed sensor is suitable for on-site and real-time monitoring of relative humidity at ambient conditions.
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