在胆酸盐介质中用氨羧配位剂溶解胆红素钙的动力学研究

以胆红素及其钙盐为主要成分的色素型胆结石病在国内为常见病,多年来曾研究用钙配位剂溶石的可能性,但效果不明显,主要由于对配位剂溶石机理了解不够。为此本文在模拟胆汁背景条件下,用氨羧配位剂溶解模拟结石的胆红索钙压片进行了动力学研究,其结果有利于阐明胆色素结合配位溶解的机理和决定溶石效果的因素。     

Abnormal dissolutions of chlorpromazine hydrochloride tablets in water by paddle method under a high agitation condition

All sugar-coated tablets of chlorpromazine hydrochloride except for those produced by one manufacture showed concave dissolution profiles in water by paddle method at 100 rpm but not at 50 rpm. The study was undertaken to clarify the agitation-dependent abnormal dissolutions. The strange dissolutions were also observed in water at different ionic strengths but not in buffer solutions of pH 1.2, 4.0 and 6.8. When monitored, the pH's of water in dissolution vessels for the abnormal tablets increased with time at 100 rpm and some of them exceeded pH 8 but did not at 50 rpm. The solubility of chlorpromazine hydrochloride decreased with the increase of pH which was too low to dissolve the whole amount of drug contained in a tablet at pH 8. The elevation of pH seemed to be mainly brought about by dissolution of calcium carbonate popularly used for sugar-coated tablets, because larger amount of calcium ion was dissolved out from the abnormal tablets at 100 rpm than from a normal tablet and from them at 50 rpm. These findings indicate that the concave dissolution profiles should be caused by the decrease of drug solubility with increase in pH of water, probably because of dissolution of calcium carbonate. We should pay attention to the change in pH of water which may differ depending on the agitation speed of dissolution tests.     

Room temperature dissolution of cellulose in tetra-butylammonium hydroxide aqueous solvent through adjustment of solvent amphiphilicity

The amphiphilicity of solvent systems is realized for adjusting the dissolution of natural cellulose by making use of tetra-butylammonium hydroxide (TBAH) as an example. TBAH aqueous solution is found to have an obvious effect on adjusting its amphiphilicity, along with a flexible concentration ranging from 40 to 60 wt% for dissolving cellulose. With a suitable amphiphilic property, cellulose can be dissolved by a TBAH aqueous system . The experimental results demonstrate that with the introduction of urea (more than 0.2:1, w:v) into a TBAH aqueous system, the dissolution process of cellulose can be dramatically promoted, leading to a transparent solution of cellulose. Herein, a complex solvent of TBAH/urea has been proposed for mild and effective dissolution of cellulose under ambient conditions. In the TBAH/urea complex solvent, the structure of the hybrid hydrate of TBAH and urea formed. Urea served as a hydrophobic contributor adjusting the amphiphilicity of the solvent system, allowing interfacial resistance between the amphiphilic crystal surfaces of the natural cellulose and solvent to be reduced. After that, the crystal of natural cellulose could be fully infiltrated and subsequently dissolved by the TBAH/urea aqueous solvent. The performances of the aqueous solvent and ambient temperature dissolution make aqueous TBAH/urea a potential and green solvent of cellulose for broad applications, such as composites, films or wet spinning of cellulose, in laboratories or industries.     

螯合剂对Co-Mo/Al_2O_3成型加氢脱硫催化剂性能的影响

以拟薄水铝石为原料,添加有机溶剂,经挤条成型、干煅、焙烧制备了比表面积大、孔分布宽的柱状γ-Al2O3载体;采用共浸渍法制备了系列Co-Mo/Al2O3催化剂(CoO和MoO3质量分数分别为2%和8%)。利用低温氮吸附、XRD和H2-TPR技术对催化剂进行了表征,考察了螯合剂柠檬酸(CA)、草酸(OA)和乙二胺四乙酸(EDTA)对成型催化剂粗苯加氢脱硫活性的影响。结果表明,添加螯合剂后,催化剂的前驱体主要沉积在载体的3~10 nm中孔内,活性组分以无定形态高度分散在载体上。添加CA可提高催化剂的还原性,显著降低Mo6+的还原温度。在300℃、3.0 MPa、液体空速(LHSV)为2 h-1和氢油体积比为600的条件下,噻吩硫的脱除率可达到99.9%以上。     

钨酸钙核/卤化银壳微晶乳剂的二次定影研究

近２０年来,随着卤化银微晶合成技术的进步,合成出了诸如Ｔ－颗粒、核壳乳剂和外延复合颗粒乳剂等性能优异的微晶体,极大地提高了乳剂的感光性能．但这些乳剂也有一个共同的缺点,即大量消耗贵金属银,且未成影像的银均随定影过程而浪费．为改善此类乳剂的不足,各国科...     

Evaluation of dithiocarbamates and beta-diketones as chelating agents in supercritical fluid extraction of Cd, Pb, and Hg from solid samples

The use of four dithiocarbamates and three fluorinated β-diketones as potential chelating agents for three transition metal ions (Cd²⁺, Pb²⁺, and Hg²⁺) extracted from spiked sand and filter paper samples by supercritical fluid extraction (SFE) was investigated. The extractions were performed at 45°C and 250 atm for spiked sand samples and at 60°C and 200 atm for filter paper samples using supercritical carbon dioxide modified with 5% methanol. At 250 atm and using carbon dioxide modified with 5% methanol, the recoveries of Cd²⁺, Pb²⁺, and Hg²⁺ ions from spiked sand samples were 95% with lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC) as the chelating agent; they ranged from 83–97% with diethylammonium diethyldithiocarbamate and from 87–97% with sodium di-ethyldithiocarbamate as chelating agents, and from 68–96% with trifluoracetylacetone, hexafluoroacetylacetone, and thenoylfluoroacetone as chelating agents. Ammonium pyrrolidinedithiocarbamate was not effective in the chelation SFE of Cd²⁺, Pb²⁺, and Hg²⁺ ions from either spiked sand or spiked filter paper samples under the extraction conditions used. Supercritical carbon dioxide alone gave consistently lower analyte recoveries than supercritical carbon dioxide modified with 5% methanol. The results suggest that the solubility of the metal chelate in the supercritical fluid plays a more important role than the solubility of the chelating agent in the supercritical fluid, as long as sufficient chelating agent is present in the fluid phase. Fluorination of the chelating agent, as in the case of LiFDDC, increases the solubility of the metal chelate, and subsequently enhances the extraction efficiency for the metal ions.     

The role of organic acids in mineral weathering

Organic acids and their anions (for brevity we shall use the term “acids” to include both) may affect mineral weathering rates by at least three mechanisms: by changing the dissolution rate far from equilibrium through decreasing solution pH or forming complexes with cations at the mineral surface; by affecting the saturation state of the solution with respect to the mineral; and by affecting the speciation in solution of ions such as Al³⁺ that themselves affect mineral dissolution rate. In this paper we review the effects of organic acids on the dissolution rates of silicate minerals, particularly feldspars, under conditions approximating the natural weathering environment −25°C, pH 4–7 and with concentrations of organic acids comparable to those measured in soil solutions.

Feldspar dissolution rates far from equilibrium increase with decreasing pH below pH 4–5. They appear to be independent of pH between pH 4–5 and about 8, and above pH 8 feldspar dissolution rates increase with increasing pH.

Small chelating ligands such as oxalate appear to accelerate feldspar dissolution through complexation of Al at the surface of the mineral. Feldspar dissolution rates in the presence of 1 mM oxalic acid show effects ranging from no enhancement to enhancements of a factor of 15, depending upon the data set, pH, and aluminum content of the mineral: there is a great deal of scatter in the available data. In general, concentrations of oxalate of the order of 1 mM are necessary to cause a significant effect. Humic acids do not appear to increase feldspar dissolution rates significantly.

Dissolution rates must decrease as the solution approaches saturation with respect to the primary phase (the chemical affinity effect). Organic acids will influence chemical affinity by complexing Al (and possibly other elements) in solution and hence decreasing the chemical activity of Al³⁺. There are essentially no data on the effect of chemical affinity on feldspar dissolution rate at 25°C and mildly acid pH, so it is hard to evaluate the importance of organic acids in accelerating silicate dissolution through the chemical affinity effect. The effect of complexation of dissolved Al does not appear to be an important determinant of silicate dissolution rates in nature.

Observed rates of silicate weathering in the field are typically much slower than predicted from laboratory experiments far from equilibrium, suggesting control by transport of solutes between “micropores” and “macropores” (“micropores” include fractures and crystal defects within grains). If such transport is rate-controlling, analysis of the effect of organic acids on weathering rates in nature in terms of dissolution rates far from equilibrium may be misleading.     

EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

霍州和兴和褐煤的热溶解聚及其有机氧的赋存形态

依次采用石油醚、二硫化碳、甲醇、丙酮和等体积的丙酮/二硫化碳混合溶剂对霍州（HZ）和兴和（XH）褐煤进行分级萃取得到萃取物（E₁-E₅）和萃取残渣（ER₁-ER₅）,利用甲醇、甲苯、等体积甲醇/甲苯混合溶剂和丙酮等溶剂分别对ER₅在320℃进行热溶得到热溶物（SPs）。HZ和XH的累积萃取物产率分别为7.03%和7.86%,其中,E₃的产率最高;萃取残渣在甲醇/甲苯混合溶剂中的热溶物产率最高,ER_5,HZ和ER_5,XH的热溶物产率分别为45.76%和40.14%。E₁-E₅的傅里叶变换红外光谱（FT-IR）谱图中均有较强的脂肪C-H的伸缩振动峰,而SPs的FT-IR谱图中具有较强的C=C、C=O和缔合羟基的吸收峰。气相色谱质谱联用（GC/MS）分析表明,E₁-E₅中含氧化合物（OCOCs）以醇、醚和酮类化合物为主,而SPs中OCOCs以醇、酚和酮类化合物为主,且极性较强的溶剂有利于褐煤中OCOCs的溶出。与原煤FT-IR谱图相比,萃取残渣和热溶残渣的FT-IR谱图中缔合羟基、C=O和C-O-C的伸缩振动峰强度明显减弱。X射线光电子能谱（XPS）分析表明,两种褐煤中不同形态氧的相对含量为C-O > C=O > COO-,并且HZ具有更高的C-O和COO-含量。     

Detection of equimolar EDTA and DTPA in spiked wastewater effluents

Ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine-pentaacetic acid (DTPA) are water ‘softening’ agents that are present in numerous household and industrial detergents. Since these particular chelating agents are not significantly degraded during conventional wastewater treatment processes, wastewater treatment plant (WTP) effluents can contain up to 19 µM of EDTA and 7 µM of DTPA. Little, however, is known about the release of EDTA and DTPA from WTPs to rivers. To gain insight, we here report on the development of a cost-effective analytical method. This method is based on the chromatography of a humic acid-cadmium (HA-Cd) complex on a size-exclusion chromatography column (SEC, Sephadex G-15) while using WTP effluents from Lethbridge, Banff and Canmore which contained 10 mM Tris-buffer as the mobile phase (pH 8.2). The intact HA-Cd complex is detected by means of a flame atomic absorption spectrometer (FAAS). The addition of equimolar EDTA and DTPA up to 10 µM allowed us to observe a concentration-dependent increase of the retention time of the main Cd-peak. This behaviour was qualitatively comparable between the WTP effluents and was rationalised by the EDTA/DTPA-mediated mobilisation of Cd from the HA-Cd complex. The signal intensity that corresponded to the mobilised Cd was used to establish calibration curves with corresponding correlation coefficients in the range of 0.950–0.978. Therefore, the developed method yields robust results for realistic concentrations of equimolar EDTA/DTPA in real WTP effluents. The developed method can now be applied to analyse real WTP effluent for the presence of chelating agents, whose concentrations may be expressed as being equivalent to a particular equimolar EDTA/DTPA concentration.     

Influence of water on the dissolution of cellulose in selected ionic liquids

Cellulose (7% water) was thoroughly dispersed in various ionic liquids (IL) and the turbidity of the mixture was investigated to distinguish real dissolution from fine dispersion. The dissolving ability of 1-butyl-3-methylimidazolium chloride (BMIMCl know cellulose solvent) and 11 other commercial IL (not reported as cellulose solvents) was studied. From the latter, only 1,3-dimethylimidazolium dimethylphosphate (DMIMDMP) could dissolve cellulose. The influence of water content on the real dissolution of cellulose in these two IL was investigated. The maximum theoretical amount of dissolved anhydrous cellulose in the IL was determined by extrapolation methodology at different temperatures. For cellulose in BMIMCl, it was 8.75 g/100 g of IL at 95 °C. DMIMDMP could achieve real cellulose dissolution only in a practically anhydrous system (2.3 g/100 g of IL at 30 °C) but dissolution was physically limited by high viscosity.     

Atomic Absorption Detector for Liquid-Liquid Chromatography

Abstract

A detector system specific for the measurement of chelating agents and applicable to liquid-liquid chromatography has been developed. A solution containing the chelating agent is passed over a short column of chelating ion exchange resin in the copper form, and directly into the aspirator of a recording atomic absorption spectrophotometer set to measure copper. A quantity of copper proportional to the quantity of the chelating agent is stripped from the column and recorded as a peak. Precision and accuracy compare with normal atomic absorption techniques, with an average mean standard deviation of 3%, and a corresponding accuracy. The detection limit for this method is 5x10-⁷ millimoles of EDTA or NTA. Determinations are rapid and reproducible in solutions having a pH in the range of 4 to 9. The role of interfering ions is considered. The applicability of the method as a specific detector system for liquid-liquid chromatographic separations of chelating agents is discussed. Recovery of chelating agents from solutions with an ionic strength approximating natural fresh waters is demonstrated.     

Determination and differentiation of nitrilotriacetic acid and ethylenediaminetetra-acetic acid

Ethylenediaminetetra-acetic acid (EDTA) and nitrilotri-acetic acid (NTA) can be differentiated and determined by titration with metal ions to visual metallochromic dye end-points. EDTA can be determined without interference from NTA, either by titrating with copper(II) at pH 5 using PAN indicator, or by titrating with iron(III) at pH 6 and 70 degrees using Tiron indicator. The total chelating power (EDTA + NTA) can be determined either by titrating with lead(II) at pH 4.4 using dithizone indicator, or by titrating with iron(III) at pH 3.5 using Tiron indicator ; NTA is determined by difference. The lowest concentration at which NTA can be determined in EDTA by titration to the iron(III)-Tiron end-point is about 1 wt.%. The apparent stability constants of the iron(III)-Tiron complexes under the conditions of the titration at pH 3.5 and pH 6 have been determined using the method of continuous variations.     

Carrier-mediated transport of rare earth elements through liquid membranes

Transport of tervalent REEs — Sc, Y, Ce, Eu, Gd, Tm, Yb — from nitrate medium through a liquid membrane containing TBP in n-dodecane, impregnated on a flat-sheet nucleoporous support, has been studied as a function of time and initial metal concentration, salting-out agent concentration and pH of the feed phase. Influences of various complexing agents dissolved in the strip phase was investigated, too. Adding a suitable amount of EDTA into the feed phase, separation of binary mixtures of REEs was experimentally achieved.     

A rapid solvent extraction method for the determination of caesium-137 in environmental materials

A solvent extraction method for the quantitative determination of caesium-137 in environmental samples is described. Caesium carrier is added to the ashed sample, which is dissolved with hydrochloric acid. The solution is filtered to remove any carbon and the pH is adjusted to 2.0. Sodium dodecylbenzene sulphonate is added and the extraction is done with phenol-nitrobenzene mixture. The organic phase is washed with EDTA solution and the caesium is stripped from the washed solvent with 6 M hydrochloric acid. The caesium is precipitated as caesium chlorostannate to ensure absolute decontamination from potassium-40. Recovery from standard solution is about 85% and from vegetation, rainwater and effluent samples about 80%. The method is applicable in the presence of large quantities of interfering ions, and decontamination factors for many nuclides are greater than 10³.     

PSVA螯合树脂的合成及其对金属离子的螯合性能

合成了大孔螯合树脂聚-N-亚水杨基乙烯基苯胺,研究了它对6种金属离子的螯合性能。结果表明,在pH=5时树脂对Cu²⁺的吸附容量达1.3 mmol/g干树脂。据此提出了一个用此树脂回收废水中微量铜和除去光亮镀镍溶液中微量Cu²⁺的方法,效果良好。     

Molar mass distribution of a commercial aliphatic hyperbranched polyester based on 2,2-bis(methylol)propionic acid

The determination of absolute molar mass averages (MMA) and molar mass distribution (MMD) of the fourth generation hyperbranched polyester Boltorn H40 (Perstorp Specialty Chemicals AB), synthesized from 2,2-bis(methylol)propionic acid (bis-MPA) as the AB2 monomer and ethoxylated pentaerythritol as the B4 core molecule was studied in dependence on the type of solvent, preparation procedure and solution concentration. Due to a large number of polar hydroxyl groups, ester, and also some residual carboxyl groups, a very stable H-bond network is formed at room temperature, that can-not be completely disrupted by dissolving the sample in solvents such as tetrahydrofuran (THF), N,N-dimethylacetamide (DMAc), a mixture of THF and methanol (9:1, v/v), and a solution of 0.7% LiBr in DMAc. The H-bonds between the polar groups break down completely and the dissolution of Boltorn H40 on the molecular level is achieved only when the sample is thermally pretreated at a minimum 140 C for at least 20 min prior to dissolution in solvents THF/methanol or LiBr/DMAc. Thus, determined MMA and molar mass distribution (MMD) of Boltorn H40 are independent on the kind of the solvent and solution concentration.     

Analysis of polar organic micropollutants in water with ion chromatography-electrospray mass spectrometry

The coupling of ion chromatography (IC) with electrospray mass spectrometry (ES-MS) opens new ways for the determination of polar organic micropollutants in water samples. The technique of conductivity suppression has been found to reduce the background signal in the range of about two orders of magnitude leading to a significant increase in sensitivity. In addition, the formation of salt adducts has been avoided. The usefulness of this method was proven on several polar and environmentally relevant micropollutants such as the herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA), the chelating agent ethylenediamine tetraacetate (EDTA) and diacetonketogulonic acid (DAG). This present study has shown that IC-ES-MS is a simple, sensitive and quick method for the determination of these polar organic traces in water samples after separation on an anion-exchange column without any derivatization. In this work, several possibilities of applications of IC-ES-MS (with varying conditions) are presented. Analysis of glyphosate, AMPA, DAG and EDTA in ground and surface water has been achieved by IC-ES-MS without additional sample preparation at a concentration level of 1 microgram/l.     

Prediction and measurement of effect of chelating selectivity on precipitation reactions

A theoretical treatment of precipitation equilibrium in the presence of a chelating agent has been expanded to include the common ion effect on precipitation reactions. The extent of precipitation can be predicted over the full range of pH for any metal for which the solubility product of the precipitate and the stability constants for a complex are known. The expanded equation has been used in this investigation to predict the extent of precipitation for several metals in the presence of ethylenediaminetetra-acetic acid (EDTA) with common précipitants such as hydroxide, oxalate, sulphate, sulphide and 8-hydroxyquinoline, but may be applied to any system containing other chelating agents. The limits of precipitation in terms of pM', the negative logarithm of the concentration of unprecipitated metal ion, are presented graphically as a function of pH for a system containing axed amounts of precipitating and complexing agents. Measurements for observed reactions at two pH levels, 5 and 10, are compared with the calculated predictions of the equation. Thirty-five metals were investigated.