镨,钕量法测定有机磷化合物中的磷含量

有机磷化合物中的磷含量可以先将样品放入氧瓶燃烧分解,再以Pr(NO_3)_3或Nd(NO_3)_3作为PO_4~(3-)的沉淀剂,并用EDTA回滴过量的Pr~(3+)或Nd~(3+)来测定。文中还介绍了消除氟,硫,硼干扰的简单方法。测定误差为±0.20%。     

用镧系元素(Ⅲ)测定有机化合物中的磷和氟

本文应用14个镧系元素(Ⅲ)对有机化合物中的磷和氟进行了测定,阐明了影响测定的因素。测定的误差:磷为±0.20%,氟为±0.30%。     

用镧系元素(III)测定有机化合物中的磷和氟

应用14个镧系元素(III)对有机化合物中的磷和氟进行了测定, 阐明了影响测定的因素. 测定的误差:磷为±0.20%,氟为±0.30%.     

C_(60)及C_(70)燃烧焓和生成焓的测定

用微型氧弹热量计测定了C60 和C70 的标准燃烧热 ,分别为 - ( 2 5 947.1±8.5 )和 - ( 2 995 6 .1± 8.9)kJ/mol.样品用色谱法分析表明有机溶剂含量很少 ,不影响测定结果 .用微型氧弹热量计及常量热量计测定C60 的结果在误差范围以内相一致 ,表明测定的可靠性 .推得了C60 和C70 的生成焓 .用键能模型估计了C60 和C70分子内的张力能 ,与由模型化合物corannulene估计的结果很接近     

汞离子选择性电极的试制及其在有机汞化物微量分析中的应用

提出氧瓶分解-汞离子选择性电极法于有机化合物中汞的微量分析。所拟定方法简便、快速,终点突跃,绝对误差±0.3%,化合物中存在氮、氟、硫、磷、硼、硅、钾、钠等元素不干扰测定。     

氟离子选择电极微量测定有机磷化合物中氟

本文报道了用氟离子选择电极法测定有机磷化合物中的氟,对试样称量、Ec_L—Ec_H以及氟离子标准溶液的配制等进行了探讨和研究,方法简便、快速、准确,与其他方法相比结果满意,误差一般小于±0.5％。     

离子色谱在有机物和高分子材料分析中的应用

介绍了用氧瓶燃烧，高温炉分解有机化合物、高分子材料等样品，用去离子水或Na2CO3／NaHCO3溶液吸收分解产物，用离子色谱测定吸收液中F^-、C1^-、Br^-、SO4^2-、PO4^3-，计算出样品中氟、氯、溴、硫、磷等元素含量的方法。     

键能的研究——马尿酸、哌嗪、氮七环燃烧热的测定

使用精密氧弹量热计测定了下列物质的燃烧热△H^-_o和生成热△H⁰_f(1)马尿酸(c)-1008.30±0.22;(2)哌嗪(c)-707.79±0.27和-9.99±0.27及(3)氮七环(1)-987.03±0.39和-21.35±0.39kcal/mol.利用文献的或我们估计的相变潜热值,得到两个环状化合物的气态生成热.按照键能模式估计了这两个化合物的环张力能,分别为(2)-0.2±1.5和(3)5.6±0.4kcal/mol,并与其它环状化合物的环张力能进行了比较.     

导数光谱法测定原子簇化合物中硫

本文用导数光谱法通过测定CrO_4~(2-)的含量,间接测定钼铁硫原子簇化合物中硫含量。用紫外一阶导数光谱来消除测定中干扰,免除了化学法消除干扰的麻烦。该方法测硫回收率为100±4％,精密度为4.0％。     

火焰光度法的简单介绍

近年来,以火焰作为光源的光谱分析的光电法,日益广泛地应用于碱金属、碱土金属和某些重金属元素的测定。其主要的优点有: 1.分析手续快速简单,测定溶液中的某一元素只需1～2分钟。 2.分析误差一般为±2～5％(相对百分数),元素含量少时,比重量法或容量法准确。在某些情形下误差还可以降低到±0.2％。 3.测定的溶液只要几毫升,可用于微量分析。     

Determination of calcium,phosphorus and fluorine in bone by instrumental fast neutron activation analysis

The determination of fluorine, calcium and phosphorus in bone by instrumental fast neutron activation analysis is described. Results for the IAEA standard material “Animal Bone” A3-74 re: Ca=313±10 mg/g, P=155±5 mg/g and F-613±20μg/g. The accuracy for all three elements is≤4%, precision being about 3%. The limit of determination for F is 120 μg, for Ca 30 mg and for P 1 mg in a sample of 500 mg.     

热分解法制备纳米氧化钕

采用热分解法以2-硝基苯甲酸和硝酸钕为原料制备了纳米氧化钕微粉,利用正交设计对合成条件进行了优化,得出了最佳的合成条件,即原料2-硝基苯甲酸与硝酸钕物质的量比2.5∶1,溶液pH值5.5,反应时间3h、干燥时间8 h,在此条件下制得了平均粒径为15 nm的氧化钕微粉,并利用XRD和TEM对制得的纳米微粉进行了结构表征.     

八面沸石用(NH4)2SiF6脱铝补硅的研究:Ⅳ.反应机理

在典型的(NH_4)_2SiF_6与(NH_4Na)Y反应条件下分别研究了(NH_4Na)Y与NH_4F、HCl和NH_4F+HCl以及HY与NH_4F的作用。发现F~-单独不能使(NH_4Na)Y脱骨架铝,HCl也不能使其脱铝(在NH_4Ac缓冲液中),而HCl+NH_4F可使其脱铝并保持较高的结晶度。据此认为(NH_4)_2SiF_6与沸石反应时,沸石的骨架铝是在H~+和F~-的共同作用下逐步脱出的,而不是被F~-抽取掉。根据反应机理提出脱铝沸石中有少量组分性氟存在,水洗不能将其除去。     

Side-chain conformation of the M2 transmembrane peptide proton channel of influenza a virus from 19F solid-state NMR

The M2 transmembrane peptide (M2TMP) of the influenza A virus forms a tetrameric helical bundle that acts as a proton-selective channel important in the viral life cycle. The side-chain conformation of the peptide is largely unknown and is important for elucidating the proton-conducting mechanism and the channel stability. Using a 19F spin diffusion NMR technique called CODEX, we have measured the oligomeric states and interhelical side chain-side chain 19F-19F distances at several residues using singly fluorinated M2TMP bound to DMPC bilayers. 19F CODEX data at a key residue of the proton channel, Trp41, confirm the tetrameric state of the peptide and yield a nearest-neighbor interhelical distance of approximately 11 A under both neutral and acidic pH. Since the helix orientation is precisely known from previous 15N NMR experiments and the backbone channel diameter has a narrow allowed range, this 19F distance constrains the Trp41 side-chain conformation to t90 (chi1 approximately 180 degrees , chi2 approximately 90 degrees ). This Trp41 rotamer, combined with a previously measured 15N-13C distance between His37 and Trp411, suggests that the His37 rotamer is t-160. The implication of the proposed (His37, Trp41) rotamers to the gating mechanism of the M2 proton channel is discussed. Binding of the antiviral drug amantadine to the peptide does not affect the F-F distance at Trp41. Interhelical 19F-19F distances are also measured at residues 27 and 38, each mutated to 4-19F-Phe. For V27F-M2TMP, the 19F-19F distances suggest a mixture of dimers and tetramers, whereas the L38F-M2TMP data indicate two tetramers of different sizes, suggesting side chain conformational heterogeneity at this lipid-facing residue. This work shows that 19F spin diffusion NMR is a valuable tool for determining long-range intermolecular distances that shed light on the mechanism of action and conformational heterogeneity of membrane protein oligomers.     

焙烧层状氢氧化镁铝对水中氟离子的吸附性能

研究了焙烧层状氢氧化镁铝(CLDH)对水中氟离子的吸附性能,考察了焙烧温度、吸附时间、吸附剂用量、溶液pH值等条件对吸附的影响.发现在较宽的pH(5.5～9.5)值范围内,CLDH对水中氟离子具有良好的吸附能力,室温下0.2gCLDH可将50mL浓度为15mg/L氟离子溶液处理为符合含氟标准的饮用水.吸附平衡符合Langmuir方程,在60min内达到饱和吸附,室温下饱和吸附量为22.64 mg/g.吸附饱和后的CLDH焙烧再生,循环使用5次后饱和吸附量为10.37 mg/g.     

INAA of fluorine in plastics using the medium-flux McMaster Nuclear Reactor

The fluorine contents of plastics, ranging from about 20 μg·g⁻¹ to 66%, may be measured instrumentally using a conventional research nuclear reactor, an automated sample irradiation and counting system, and a set of well-calibrated, in-house, fluorine standards. Plastics with low to medium fluorine contents may be analyzed using ²⁰F by placing the gamma-ray detector at appropriate distances from the irradiated sample. For high-F plastics, samples may be irradiated in a cadmium lined irradiation site, using ¹⁹O and ²⁰F. Counting statistics of <3% translate into reproducibility of measurements within ±3% and analytical accuracies of ±1% to ±10%.     

Treatment of rare-earth concentrate to remove phosphorus and fluorine compounds

It was suggested to purify poor lanthanide concentrate precipitated from the extraction orthophosphoric acid produced by the dihydrate process to remove phosphorus and fluorine compounds by heating a mixture of the concentrate with sulfuric acid in the presence of hydrated silica followed by water leaching of water-soluble sulfates and phosphates. The treatment conditions for the separation of the bulk of phosphorus(V) and the entire fluorine in the form of SiF₄ were determined, ensuring approximately 3.5-fold increase in lanthanide concentration.     

离子色谱法测定水中的F-、Cl-、NO2--N、NO3--N、SO42-

应用DX－102型离子色谱仪测定水中的F^-、Cl^-、NO2^-－N、NO3^-－N及SO4^2-，淋洗液为1.42mmol/L NaHCO3-1.50mmol/L Na2CO3溶液，淋洗液流速为1.8mL/min，进样量为25μL。5种离子在上述实验条件下分离良好，定量测定的线性相关系数均在0.9995以上。     

Fluorophilicity switch by solvation

A new type of fluorous distannoxanes, [XRf2SnOSnRf2Y]2 (Rf = C6F13C2H4; X, Y = C6F13SO3 (2) and (C6F13SO2)2N, Cl (3)) was prepared successfully as hydrates from the reaction of [ClRf2SnOSnRf2Cl]2 with C6F13SO3Ag and (C6F13SO2)2NAg, respectively. Despite their high fluorine content (59.85 and 59.27% F), these distannoxanes were completely insoluble in fluorocarbons as well as hydrocarbons and halo alkanes. In contrast to this, fluorous distannoxanes 2 and 3 were soluble in polar organic solvents, such as EtOAc, acetone, and THF. When 2 and 3 were added to a two-phase mixture of fluorocarbon and EtOAc, the mixture turned miscible in proportion to the amount of 2 and 3 added, and finally, the mixture turned to a homogeneous solution.