离子色谱同时测定中草药中磷硫含量

应用离子色谱法同时测定了硫酸根和磷酸根的含量。用茶叶(GBW10016)、柑橘叶(GBW10020)和黄芪(GBW10028)标准物质来验证方法的准确性,测定值与标准值基本吻合。磷在0.01～100.0μg/mL,硫在0.01～60.00μg/mL范围内呈良好的线性关系(R2≥0.9993),磷和硫的检出限分别为0.0...     

The adsorption site and orientation of CH3S on Ni(111)

The angle-resolved X-ray photoelectron spectra for 0.15 monolayers (ML) of sulfur, and 0.25 ML methyl thiolate formed at 100 K and annealed to 150 and 250 K, on Ni(111) are analyzed to determine the structures of these species. It is found that sulfur adsorbs on the face-centered cubic hollow site on Ni(111) with a S---Ni bond length of 2.20±0.02 Å. The thiolate species formed at 150 K has the C---S bond tilted at 35° to the surface normal with a C---S bond length of 1.85±0.02 Å and a S---Ni bond length similar to that for adsorbed sulfur (2.2 Å). The methyl group is tilted toward the bridge site and the thiolate appears to be adsorbed on the face-centered cubic site although there may also be adsorption in the hexagonal close packed site. The species formed at 250 K adsorbs on a reconstructed surface where the chemical shift of the S 2p core level indicates that it adsorbs at a four-fold site and the angle-resolved XPS data indicate that the C---S bond is oriented normal to the surface. The calculated angular variations in intensity are consistent with this interpretation but cannot distinguish between the various models proposed for the reconstructed surface.     

Initial incorporation of sulfur into the Pd(1 1 1) surface: A theoretical study

Density functional theory is used to investigate the initial inclusion of sulfur into the subsurface interstitial sites of Pd(1 1 1) surface. Pure subsurface adsorption is found to be less energetically favorable than on-surface adsorption. The incorporation of sulfur into the metal becomes more favorable than continuous adsorption on the surface after a critical on-surface sulfur coverage. We find subsurface sulfur occupation to be energetically favorable after adsorption of more than half a monolayer on the surface. Occupation of subsurface sites induces a pronounced structural distortion of the Pd(1 1 1) surface. We find significant expansion of interplanar spacing between the uppermost surface metal layers and rearrangement of the S overlayer. The interplay between the energy cost due to structural distortion of Pd(1 1 1) and the energy gain due to bond formation for different structures is discussed.     

Hydrogen Bonds as Essential Elements in the Crystal Structures of Three Piperidinium Thiotungstates

The crystal structures of [pipH]₂[WS₄] ( 1 ) and the new compounds [pipH]₃[WS₄](HS) ( 2 ) and [pipH]₄[WS₄][WOS₃] ( 3 ) (pip = piperidine) were determined. Hydrogen bonds between the piperidinium cations and the thiotungstate anions play a dominant structural role. Their strength and number correlates with the degree of distortion found for the tetrahedral anions. Unshared hydrogen bonds have a considerably stronger effect than bifurcated ones; the effect of trifurcated hydrogen bonds is extremely weak. HS^? and [WOS₃]^2? are considerably stronger H bond acceptors than the [WS₄]^2? anion.     

离子色谱法测定芳香族聚酰胺纤维中硫、钠、钾、钙、镁

应用离子色谱法(IC)测定芳香族聚酰胺纤维中硫、钠、钾、镁及钙。测定阴离子时,试样置于铂坩埚中用艾斯卡试剂覆盖,置于马弗炉中,450℃灼烧1 h使有机物碳化,取出,稍冷,再加少许艾斯卡试剂,升温至850℃灼烧1．5 h,使有机物完全分解。坩埚中的熔块经冷却后用去离子水浸出,用18 mmol·L-1碳酸钠及17 mmol·L-1碳酸氢钠混合溶液定容后,用IC法的阴离子方式测定。用IC法测定阳离子时,试样置于铂坩埚中,不必加艾斯卡试剂,置于马弗炉直接灼烧至有机物完全分解。残渣用1 mol·L-1硝酸或1 mol·L-1盐酸超声波处理,用去离子水洗涤坩埚并定容至100 mL,按所测得峰面积值从标准曲线查得其含量。用此方法测定SO42-,Na+,K+,Mg2+及 Ca2+的检出限依次为0．02,0．25,0．25,0．70及0．80 mg·L-1。     

Studies of degradation enhancement of polystyrene by flame retardant additives

Experimental methods as well as thermodynamic modeling techniques were utilized to explore potential gas and condensed-phase contributions of various flame retardant (FR) additives with polystyrene polymer. FR additives investigated include hexabromocyclododecane (HBCD), triphenyl phosphine oxide (TPPO), triphenyl phosphate (TPP), triphenyl phosphine sulfide (TPPS), and sulfur. Flame studies of fundamental FR activity were also employed using molecular beam mass spectrometry analysis of FR active species directly in a flame system. The flame studies show direct evidence for active bromine (HBr, Br) species for HBCD and active phosphorous species (HPO₂, PO, PO₂ HPO₃) species for TPPO and TPP which provide high potential for gas-phase activity for these FR additives. Various experimental measurements were also done to assess the degradation species and the degree of degradation of polystyrene by the FR additives. These studies support enhanced degradation of the base polystyrene polymer by the FR additive as a major pathway for condensed FR activity for HBCD and sulfur FR additives. Phosphorous based structures appear to show little enhancement of polystyrene degradation.     

热水解离子色谱法测定岩石样品中的氯和硫

研究开发了一种热水解离子色谱法测定岩石样品中的氯和硫的方法技术。所研究开发的方法具有灵敏、高效、无干扰和准确的特点。实验研究和选择了热水解离子色谱测定的最佳工作条件。用测定的方法对6个国家一级岩石地球化学标准物质GSR1－6进行了分析测定，并在研究我国东部上地壳区域元素丰度实践中测定了2000件岩石样品。测定结果表明，测定值与标准物质的标准值一致。该方法的检出限分别国；氯31×10^-6。方法的精密度（RSD，％）对氯含量水平为40×10^-6，硫酸根含量水平180×10^-6时分别为6.1%和3.0%。     

Racemization of sulfinic esters with trichloroacetic anhydride

Both alkane- and arene-sulfinates undergo racemization and oxygen exchange reaction with trich-loroacetic anhydride. The rate of racemization of (?)menthyl (?)p-toluenesulfinate was found to be twice that of oxygen exchange, suggesting the reaction involves a Walden inversion. When reaction was carried out in benzene, the rate of racemization was found to be first order with respect to both sulfinic ester and trichloroacetic anhydride. The substituent effect is large (p = ?1.53) suggesting that the initial acylation is the rate-determining step. The rate of racemization was found to be retarded by the addition of perhaloacetic acid while very small catalytic effect of mercuric chloride was observed.     

Effect of heterogeneity on the quantitative determination of trace elements in concrete

Laser-induced breakdown spectroscopy has been used for quantitative measurement of trace elements, e.g. sulfur and chlorine, in concrete. Chloride and sulfate ions have a large effect on the durability of concrete structures, and quantitative measurement is important for condition assessment and quality assurance. Concrete is a highly heterogeneous material in composition and grain-size distribution, i.e. the spatial distribution of elements. Calibration plots were determined by use of laboratory-made reference samples consisting of pressings of cement powder, hydrated cement, cement mortar, and concrete, in which the heterogeneity of the material is increasing because of the aggregates. Coarse aggregate and cement paste are distinguishable by the intensity of the Ca spectral lines. More advanced evaluation is necessary to account for the effect of the fine aggregate. The three series of reference samples enable systematic study of the effects of heterogeneity on spectral intensity, signal fluctuation, uncertainty, and limits of detection. Spatially resolved measurements and many spectra enable statistical evaluation of the data. The heterogeneity has an effect on measurement of the sulfur and chlorine content, because both occur mainly in the cement matrix. Critical chloride concentrations are approximately 0.04% (m/m). The chlorine spectral line at 837.6 nm is evaluated. The natural sulfur content of concrete is approximately 0.1% (m/m). The spectral line at 921.3 nm is evaluated. One future application may be simultaneous determination of the amount of damaging trace elements and the cement content of the concrete.