[Study of the Impact of Sample Thickness on Thin Film Method X-Ray Fluorescence Spectrum Measurement].

The mixed samples of nylon film enrichment of Cr, Pb and Cd three elements and glass fiber membrane filter were as the research object. With the method of superposition of membrane filter, the XRF spectra were measured under different thin film samples thicknesses. According the changes of characteristic XRF of Cr, Pb and Cd elements in the mixed sample and Ca, As and Sr elements in glass fiber membranes, the effects of sample thickness on thin film method XRF spectrum measurement were studied. The study results showed that the effects of thin film sample thickness on the fluorescent properties of elements with characteristic spectral lines in different energy ranges were different. The energy of characteristic spectral lines was greater, the loss of element characteristic X-ray fluorescence when it passed through membrane and reached detector was less. But matrix effect caused by thin film sample thickness increase was stronger with the energy of characteristic spectral lines greater. The background fluorescent intensity in corresponding characteristic spectral line location was greater. So the impact of matrix effect caused by sample thickness increase on thin film method XRF spectrum measurement sensitivity was greater. For elements with low energy characteristic spectral lines (energy≤7 keV), the way of increasing thin film sample thickness in order to increase the mass-thickness concentration of component measured, can not effectively improve the sensitivity of thin film method XRF spectrum measurement. And thin film samples thickness within 0.96 mm is conductive to the measurement and analysis of XRF spectrum. For element with higher energy characteristic spectra lines(energy＞7 keV), the sensitivity of XRF spectrum measurement can be appropriately increased by the way of increase thin film sample thickness in order to increase the mass-thickness concentration of component measured. And thin film samples thickness within 0.96～2.24 mm is more conductive to the measurement and analysis of XRF spectrum. The study provides an important theoretical basis for thin sample preparation and enrichment technology of thin film method X-ray fluorescence spectrum analysis the atmosphere and water heavy metal.

[The study of selecting sample detecting position and lead plate inner material in thin film method X-ray fluorescence measurement].

(1) In this paper type 316 stainless steel metal plate as the research object, the selection of sample detecting position was studied when thin film method X-ray fluorescence measurement was conducted. The study showed that the optimal location for the sample detection was sample distance X-ray tube and detector baseline 1cm with the baseline into a 16°angle. (2) Heavy metal pollutants of Pb, Cd and Cr in industrial ambient air as the main analysis object, when thin film method X-ray fluorescence conducted with lead plate protection, X-rays will penetrate the membrane and continuely stimulate the protective lead plate. Therefore there is lead spectral line interference in the filter membrane background spectrum, which will affect the detection of lead element in real samples. Studies show that when a layer of isolating material was applied between the thin sample and the protective lead plate, the interference of lead line can effectively be avoided. (3) Several rigid insulating material of type 316 stainless steel, brass, aluminum, red copper and PTEE as lead inner material were selected and studied. The study results showed that compared with X-ray fluorescence spectra of other lead inner materials, the X-ray fluorescence spectrum of red copper contained the least element spectral lines. There were not Cr, Cd and Pb spectrum peaks in the X-ray fluorescence spectrum of red copper. And the target timber scattering spectrum intensity in the high energy part was weaker compared to other X-ray fluorescence spectrum. The above analysis shows that red copper has the minimal disturbance to the actual measurement of heavy metals Cr, Cd and Pb. At the same time, red copper as lead inner materials can effectively avoid the interference of lead spectrum line in lead plate. So red copper is the best lead plate inner materials in thin film method X-ray fluorescence spectroscopy measurement. This study provides an important theoretical basis for the assembling and setting'up air and water weight metal X-ray fluorescence spectrometer.

[Applications of real-time monitoring techniques in chemical synthetic ingredients].

Real-time monitoring technique for process parameters and/or insight variables of chemical synthetic ingredients is a novel chemical process analysis method, which can real time monitor the chemical synthetic ingredients, reveal the mechanism of chemical reaction occurring, reaction courses and kinetic characteristics, and monitor, control and adjust chemical reaction to determine the endpoint of reaction and enhance selectivity of reaction, quality and yields of product. Many real-time monitoring techniques were achieved to satisfy the demands in several chemical synthetic reactions. The structure and principles of current real-time monitoring techniques was stated, and a review was summarized on its applications in chemical synthetic ingredients. The research, development and applications of real-time monitoring techniques such as spectrometry (i. e. ultraviolet-visible spectrophotometry, infrared spectrometry, Raman spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry and fluorescence spectroscopy), chromatography (i. e. thin layer chromatography, gas chromatography, high performance liquid chromatography and capillary electrophoresis) and their coupled techniques (i. e. GC-MS, GC-IR and LC-MS) for chemical synthetic ingredients were evaluated. The coupled techniques were utilized to take the advantages of their high performance separation and quantitative power of chromatography, and sensitive and qualitative identification capacity of spectrometric techniques could realize the real-time monitoring for special chemical synthetic ingredients in complex systems. The future developmental trends and application prospects of real-time monitoring techniques are also discussed. With the research & development of microprocessor and embedded system, the real-time monitoring instrument for chemical synthetic ingredients will have a trend to miniaturization, intelligence, digitization, functionalization and multichannel with widely versatile and strongly compatible features.

Hydrothermal synthetic mercaptopropionic acid stabled CdTe quantum dots as fluorescent probes for detection of Ag⁺.

Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) with particle size 3 nm have been successfully synthesized in aqueous medium by hydrothermal synthesis method. And the effects of different metal ions on MPA capped CdTe QDs fluorescence were studied using fluorescence spectrometry. The results demonstrated that at the same concentration level, Ag(+) could strongly quench CdTe QDs fluorescence, and the other metal ions had little effect on CdTe QDs fluorescence except Cu(2+). On the basis of this fact, a rapid, simple, highly sensitive and selective method based on fluorescence quenching principle for Ag(+) detection in aqueous solution was proposed. Under optimal conditions, the quenched fluorescence intensity (F(0)-F) increased linearly with the concentration of Ag(+) ranging from 4 × 10(-7) to 32 × 10(-7)mol L(-1). The limit of detection for Ag(+) was 4.106 × 10(-8)mol L(-1). The obtained plot of F(0)/F versus [Ag(+)] was an upward curvature, concave towards the y-axis, rather than a straight line. The modified form of the Stern-Volmer equation was third order in Ag(+) concentration. According to the modified Stern-Volmer equation, it can be inferred that dynamic quenching and static quenching simultaneously occurred when Ag(+) interacted with MPA capped CdTe QDs. At the same time other factors might also influence the quenching process. Based on this study, hydrothermal synthesized MPA capped CdTe QDs with particle size 3 nm may be used as a novel fluorescence probe to quantificationally and selectively detect Ag(+).