Determination of fluorine in solids down to 120 μg/g by wavelength dispersive X-ray fluorescence spectrometry

An X-ray fluorescence spectrometric method is described for the determination of fluorine from percent level down to 120 g/g in fluoropolymers and in fluoride samples. The method is based on the measurement of the intensity of first order line for 30 seconds using a flow proportional counter and a multilayer AXO6 crystal (2d=5.52 nm). The calibration curves of first degree base polynomials are linear over the concentration range of 8000–120 g/g and of 48.92–76% measured. The precision and accuracy obtained for polymer samples in percent level of fluorine are up to ±0.5 and within ±1%, respectively. However, the precision () for trace concentrations is in the range from 8 to 20%. In most cases the accuracy is up to ±7%, ±5% and ±4% in the concentration range of 120–8000 g/g, 801–8000 g/g and of 120–400 g/g, respectively. The time needed to analyze one sample including calibration and regression analysis is about 8 minutes.     

Bei der Bestimmung sehr kleiner Mengen Quecksilber (0–0,5 μg/g) in synthetischen Lebensmittelfarbstoffen

Analytical and Bioanalytical Chemistry -     

Evaluation of the uranium concentration in rocks at the μg/g level by a low-background Geiger-Müller counter

A low-background -counter and a simple direct method, based on total -counting, have been developed in order to estimate the concentration of uranium at the g/g level in ordinary rock samples. The method is a relative one; international standards have been used for calibration. Only 3 g of rock powder is needed. Combining this method with -spectrometry, direct determination of²³⁸U (independently of²²⁶Ra) becomes possible near the above concentration level.     

Untersuchung g?rtnerischer Erden

Ohne Zusammenfassung     

Determination of Cd and Pb at μg/L levels by HHPN-beam injection flame furnace-AAS

Flame-heated tubes are widespread in flame-AAS, mainly for the determination of hydride-forming elements. Instead of the introduction of gaseous compounds liquids can also be introduced continuously in such an absorption cell. With the aid of an HPLC pump the liquid is forced through a very fine nozzle, generating an aerosol beam less than 0.5?mm in diameter. This beam travels a distance of 10?cm as a “free-flying aerosol jet” into the sample introduction hole of a metal tube furnace placed in the flame. Both introduction of the entire sample and the long residence time lead to a considerable improvement in power of detection. The detection limit for 100 μL samples amounts to 7 μg/L (Pb) and to 0. 2 μg/L (Cd), which means an increase in power of detection of between one and two orders of magnitude compared to conventional flame-AAS. The relative standard deviation (100 μL sample volume, N = 10) was found to be 1.3% (signal area) for 600 μg/L Pb and to be 1.5% (signal-area) for 15 μg/L Cd. RSD values from measurements in peak-height amounted to 2.2% (Pb) and to 1.7% (Cd).     

MRCI及其近似方法下C2分子X1∑+g, B1△g和B'1∑+g态的势能曲线

运用MRCI及其近似方法计算得到C2分子X1∑+g,B1△+g,和B'1∑+g 3个电子态的势能曲线,并以FCI方法为基准,考察比较各种方法的优缺点.MRCI计算与FCI计算几乎不存在差别,在FCI计算不现实的情况下,MRCI计算足以作为基准考验其他计算方法.多种近似方法均能达到化学精度,并提出一个有效的选择参考组态的方法,提高MRCI计算效率的同时,保证计算的精确性.     

Potential energy curves for the X1∑ g, B1△g and B''''1∑ g states of C2 using MRCI and approximate CI methods

The potential energy curves for the X1∑ g, B1△g and B′1∑ g states of C2 have been studied by using MRCI and approximate CI methods, and are benchmarked against the calculations of full configuration interaction (FCI). The results obtained by MRCI method agree with the FCI very well, and even are accurate enough to compare other approximate methods as benchmark, when the calculations of FCI are not feasible. The approximate CI methods mentioned in this paper are reliable for treating chemical problems.     

A Na2 X 1 Σ g + and (1)1Π g electronic states long range analysis

In this paper the Na₂ X ¹ Σ _g ⁺ and (1)¹Π _g electronic states long range tail functional behavior is analysed in the light of multipolar expansion theory combined with damping functions. The experimental data used here is the one reported by Barrow et al. [1]. In the present paper this experimental data is used in a nonlinear reduction to van der WaalsC _n constants using the multipolar expansion Σ _n C _n /r ⁿ . Since the internuclear distance reached by the biggest part of the data is still out of the Le Roy's region (where the internuclear distance must be greater thanr _lim: $$r_{\lim } = 2\left( {\left\langle {r_A^2 } \right\rangle ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} + \left\langle {r_B^2 } \right\rangle ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} } \right),$$ being the outermost electron orbital radii for the 〈r _A 〉 and 〈r _B 〉 two atoms), the exchange energy must be taken into account. Due to the fact that the 1/r ⁿ expansion diverges whenr→0, the damping functions has been included in order to prevent this. The obtained values for theC _n coefficients, as well as the exchange energy constants, show a good agreement with the theoretical available data, for both electronic states.     

锑试金富集痕量金的研究——地质样品中ng/g级金的测定

研究了用锑作捕集剂富集地质物料中ng/g级金的新火试金法。此法分为捕集和灰吹两部分。当样品同含有氧化锑、碳酸钠、碳酸钾、硼砂、氧化铋和面粉的熔剂在950℃熔融时,金被捕集在熔融的锑中。然后灰吹此锑合金而得到含金的试金合粒(Ag粒或Ag-Pd粒)。结果表明,对于金的富集,锑试金法优于或等于铅试金,而试剂空白则低得多。试金合粒中金的测定可用发射光谱法(ES)或石墨炉原子吸收光谱法(AAN)完成。此两法的检出限都是0.1ng/g,分析空白0.7±0.3ng。对于3.4ng/g的样品,全过程的相对标准偏差,用ES法为10％,用AAN法是3.7％。上述方法快速,用于6个标准物质的测定,结果满意。     

The Coincidence of Mass Integrals g(α)

The idea of the generation of thermokinetic models on the basis of the analysis of kinetic equations (isothermal conditions) and thermokinetic equations (dynamic conditions) is presented. The method resembles that used in polisothermal conditions, which consists in analysis of the relation of the equilibrium conversion degree vs. temperature. The interpretation of the coincidence of mass integrals g(α) in the relation α vs. temperature has been attempted. This revised version was published online in August 2006 with corrections to the Cover Date.     

LDPE－g－MALa离聚物的研究

详细地研究了ＬＤＰＥ熔融接枝马来酸镧（ＭＡＬａ）的反应。产物ＬＤＰＥ－ｇ－ＭＡＬａ的ＩＲ表明在波数１５４９ｃｍ－１和１６２８ｃｍ－１处出现了羧酸盐的Ｃ＝０伸缩振动峰，说明ＭＡＬａ已接枝在ＬＤＰＥ上；ＷＡＸＤ衍射结果则表明在２θ＝１７．２０°、１４．２０°处出现了新的衍射峰—离子峰。为了控制熔融接枝过程，考察了各种瓜条件对接枝率的影响。同时，ＤＳＣ的结果表明离聚物中离子微区的存在在结晶过程中可以起到较好的成核作用。     

用微扰增强双共振对Na2 2 3 Πg和 3 3 Πg能级进行新观测

The Ω = 0,1,2 levels of the Na2 2 3Πg and 3 3Πg states in the energy region between 34860 cm-1 above the Te of the ground state and the 3s+3d atomic limit have been probed by pulsed laser perturbation facilitated optical-optical double resonance（PFOODR）spectroscopy. Strong mixing of these two states has been observed. The Tv and Bv values are given for the Ω = 0 component without deperturbation.     

Moisture absorption and diffusion in an underfill encapsulant at T > T g and T < T g

Moisture absorption and diffusion behavior of an underfill material used for electronic packaging with a glass transition temperature (T _g) slightly above room temperature have been investigated by the sorption thermogravimetric analysis technique. It has been found that moisture diffusion in this material follows the Fick’s diffusion model, and moisture absorption–desorption is reversible and repeatable. Based on moisture-induced mass gain versus time curve, the diffusion constant can be determined. It was found that below T _g, moisture diffusivity exhibits an Arrhenius temperature dependence, which changes to a different Arrhenius temperature dependence as the temperature increases to T > T _g. The change in diffusivity from T < T _g to T > T _g is accompanied by a significant decrease in the energy barrier for moisture diffusion. Results shed light on the change in moisture diffusion in polymer-based materials in the glassy and the rubbery state.