A technique for the analysis of trace amounts of volatile products from polymer degradations

A technique for the qualitative and quantitative analysis of trace amounts (0, 1 mg) of liquid nitrogen-condensable volatiles produced during polymer degradation is described. Products trapped at liquid nitrogen temperature at 10^?5 torr are slowly distilled into a second trap as a result of the gradual warm-up of the first trap. Pressure changes accompanying distillation are detected by a Pirani gauge and are used to characterize individual degradation products following calibration of the system using reference liquids. Quantitative analysis is achieved by fractionation of the products and measurement of the total pressure exerted by each component on complete vaporization in a closed system. Variables influencing the sensitivity of the technique are examined.     

气-质联用法测定食品用塑料包装材料中痕量邻苯二甲酸酯

为了使检测结果具有较高的精密度和准确度,采用气相色谱-质谱联用(GC-MS)法,研究了较低浓度下邻苯二甲酸酯的线性范围、回收率及精密度。结果表明:当用较低浓度的标准溶液作标准曲线时,16种邻苯二甲酸酯在低浓度范围内具有良好的线性关系,相关系数均≥0.999。除了BBP、DBEP和DNP的检测下限为0.025 mg/L外,其余13种化合物的检测下限均为0.01 mg/L。在较低浓度的平均回收率为83.43%～106.36%,相对标准偏差为1.14%～6.03%。     

Analysis for trace amounts of geosmin in water and fish

Trace amounts of geosmin (trans-1,10-dimethyl-trans-9-decalol) were concentrated from relatively large volumes of water by vegetable oil extraction. After stirring the two phases for 30 min, the dispersed oil was allowed to separate. The oily layer was removed and centrifuged to break the emulsion and separate the two layers. The direct gas chromatographic technique was used to resolve the geosmin from other volatile components on a capillary gas chromatographic column. Volatiles were separated from the oil by securing an aliquot of the oil layer on volatile-free glass wool in the glass liner of the special gas chromatography inlet system. Geosmin was detected at the parts ber billion level with this simple and rapid technique. A technique also was developed for detecting geosmin in fish tissue; it involves steaming the fish to break up the tissue, centrifuging the residual oil phase, and detecting geosmin by capillary gas chromatography. The geosmin remains in the residual oil. Presented in part at the AOCS Annual Meeting in Philadelphia, PA, May 5–9, 1985.     

Determination of dimethylpolysiloxanes in fats and oils1

A direct aspiration, flame atomic absorption method has been developed for the determination of dimethylpolysiloxanes (DMPS) in fats and oils. The detection limit of the method is approximately 1 ppm with a standard deviation for samples containing 1–10 ppm DMPS of 0.3. The technique is reasonably rapid, requires a minimum of sample preparation, and is applicable to the analysis of both hydrogenated and nonhydrogenated products. Presented at a symposium of the North Central Section, March 28, 1979.     

氯硅烷中痕量磷杂质的检测方法及应用

针对混合氯硅烷原料中沸点接近、分离困难的含磷杂质物系,对比金属氧化物吸附剂,以13X分子筛（13X）及负载CuCl₂的13X分子筛（Cu-13X）作为络合吸附剂进行气相吸附实验,并采用紫外分光光度计检测氯硅烷中磷杂质含量,结合水中和氯硅烷原料中磷含量分析实验考察了氯硅烷原料预处理过程中水解液组成、氯硅烷原料的相态对用紫外分光光度计检测磷杂质含量范围的影响规律及机理,探究了13X及Cu-13X在20℃时作为络合吸附剂的突破曲线。结果表明,氯硅烷原料的预处理相态为气相并以高纯氮气作载气通入高纯水中,氯硅烷中磷杂质质量含量的检测范围为0.0003～0.03,13X经过CuCl₂浸渍改性后性能得到大幅度提升,当穿透实验进行到混合液体积为120mL时,络合吸附剂对PCl₃的脱除效率仍大于80%,而在混合液体积20mL,左右13X-分子筛则被完全穿透失去吸附能力。     

Electrochemical analysis of trace amounts of water in propylene carbonate electrolytes

Cyclic voltammetry and limiting currents to an rde have been used for the determination of the water in the 0.3–20 ppm range, in PC electrolytes. Carefully dried solutions yielded voltammetric peaks proportional to the amount of water added. In KPF₆ electrolytes, the cathodic current corresponding to the reduction of water was at 0.48 V, while in KAlCl₄ solutions the reduction occurred already starting at 2.8 V, both relative to a K/K⁺ reference. At these potentials, the current to an rde showed Levich type dependence on rpm and was proportional to the concentration of water in the range 0.5–20 ppm. The calculated diffusion coefficients of water are higher than expected: 25°C, D_H2O = 8.5±2 × 10⁻⁶ cm² s⁻¹ in 0.5 M KPF₆, while in 0.25 M KAlCl₄D_H2O, 10±2 × 10⁻⁶ cm² s⁻¹.     

分光光度法测定水中十六烷基三甲基溴化铵的含量

通过可见光谱法研究了十六烷基三甲基溴化铵(CTAB)与甲基橙(MO)的显色反应,提出采用分光光度法测定水中十六烷基三甲基溴化铵的方法。结果表明,在体积分数为20%乙醇水溶液中,CTAB与MO形成1∶1的黄色离子缔合物,最大吸收波长位于470 nm处,摩尔吸光系数ε=1.404×103L.mol-1.cm-1,CTAB的浓度在0~6.0×10-4mol/L符合比耳定律。方法简便,快速,适于水样中CTAB的测定。     

Separation of trace amounts of palladium from water and wastewater samples using MPTMS-SBA-15 mesoporous silica sorbents

This study describes the application of functionalized Santa Barbara Amorphous mesoporous silica as an easily prepared and stable solid sorbent for the separation of trace amounts of palladium (Pd) ions in aqueous solutions. The mesoporous silica was functionalized by 3-mercaptopropyltrimetoxysilane, and its application as solid sorbents for the preconcentration of Pd ion was studied. Different experimental conditions such as pH, type and concentration of eluent solution were optimized. The in?uence of various interferences ions on the recovery of Pd(II) was investigated. In the optimized condition, the recovery was greater than 98.3%. The maximum adsorption capacity was obtained 146.2 mg g^?1 for the modified sorbent. The proposed procedure was applied for the separation and preconcentration of Pd in water and wastewater samples.     

Removal of trace amounts of strontium from aqueous solutions by ion flotation. I. Batch experiments

The most suitable conditions for the removal of strontium ions from aqueous solution by ion flotation have been investigated. The optimum conditions for pH, gas flow rate, concentration of strontium carrier and that of the collector as well as effect of interference by foreign ions were determined. The most suitable collector was found to be α-sulphopalmitic acid and removal of strontium above 99.9% was achieved. These data were required as a preliminary to an investigation into the conditions for a continuous process which was subsequently developed.     

Removal of trace amounts of strontium from aqueous solutions by ion flotation. II Continuous scale operation

A flotation circuit operating on a continuous basis has been designed and constructed for removal of Sr ions from simple aqueous solutions. Under steady-state conditions, a continuous extraction rate of 97.3% has so far been achieved. The effects of changing the gas rate and flow rates of both the Sr and collector solutions were also examined. Finally a discussion is included where the results of these experiments are compared with those from similar continuous-scale experiments where Sr ions are removed by the technique of foam separation.     

低温煤焦油中特定芳烃组分的选择性分离

以研究低温煤焦油中特定芳烃组分的选择性分离为目标, 通过预处理分离酚类化合物和富集特定芳烃组分, 采用多元溶剂萃取方法选择性分离芳烃和非芳烃组分, 采用Hansen溶度参数理论进行多元溶剂的设计和萃取条件的优化。结果表明, 溶剂对原料焦油的选择性随Hansen溶度参数“距离”(R_a)增加而增大, 萃取能力则相反。研究得到的多元萃取剂是含水量为体积分数6%的N,N-二甲基甲酰胺溶液, 优化萃取条件是温度25℃、剂/油比6:1。萃余物经多次萃取进一步分离芳烃组分, 萃出物经甲酰胺多次萃取以分离出杂环化合物和极性组分。芳烃组分在最终分离产物中的质量分数为94%, 其总萃取收率为95%。另外非芳烃化合物、杂环化合物和其他极性组分也在本过程中得到了有效富集。     

Electrochemical method for quantitative determination of trace amounts of disperse dye in wastewater

The electrochemical behaviour of Disperse Red 13 dye at a glassy carbon electrode was investigated in both organic and aqueous organic mixtures. Best results were obtained in N,N‐dimethylformamide/Britton–Robinson buffer (1:1, v/v), which displays a well‐defined peak at ‐0.40 V (vs Ag/AgCl) owing to reduction of the protonated nitro group. This method can be successfully applied to the electroanalytical determination of Disperse Red 13 in a very simple and inexpensive way. All the differential pulse voltammetry parameters were optimised by using a glassy carbon electrode modified with poly(glutamic acid) films. The targeted analytical method presented a linear response from Disperse Red 13 concentrations between 2.5 × 10^?7 and 3 × 10^?6 mol l^?1 (r = 0.997), with a detection limit of 1.5 × 10^?8 mol l^?1 and recoveries of 89.7–95.10% in water samples. Disperse Red 13 was successfully determined in textile industry wastewater by means of the proposed method after pre‐extraction in a solid‐phase extraction cartridge.     

茜素红退色动力学光度法测定痕量钴

在pH 8.0的NH3.H2O-NH4Cl介质中,以聚氧乙烯醚-200(PEG-200)为活化剂,Co(Ⅱ)催化溴酸钾氧化茜素红退色,建立了动力学光度法测定痕量Co(Ⅱ)的新方法。方法检出限为2.0×10-7g/L,线性范围0.01~0.21μg/50mL,最大相对标准偏差为2.3%,用于湖水及生产排水的测定,结果满意,加标回收率在96.0%~105.0%之间。     

液膜分离富集、测定痕量汞

用Ｐ３５０、Ｌ１１３Ａ、二甲苯等乳状液膜体系,研究了Ｈｇ＾２＋的迁移富集行为。实验结果表明,在适宜条件下,Ｈｇ＾２＋的迁移率达９９．７％以上。在此条件下,许多共存离子如Ｃｕ＾２＋、Ｐｂ＾２＋、Ｚｎ＾２＋、Ｓｎ＾４＋、Ｃｏ＾２＋、Ｎｉ＾２＋、Ｃｄ＾２＋、Ｃａ＾２＋、Ｍｇ＾２＋、Ｆｅ＾３＋、Ａｌ＾３＋和许多阴离子等都不被迁移,只有Ｈｇ＾２＋能从这些离子中得到满意的分离。此法用于富集测定水和工业废水中痕     

Low temperature sintering of a pottery clay from Burkina Faso

The sintering at 1000°C of a clay raw material for pottery mixed with calcite was studied to increase the mechanical characteristics of the fired product. The kaolinitic clay used comes from a large pottery production area in Burkina Faso. The experiments of this study were conducted as similar as possible to the traditional practices of potters to ensure a future technological transfer of results. An increase of the flexural strength from 7 to 17 mPa was obtained by adding 15% of calcite. To explain the mechanisms involved, the sintering behaviour was initially observed by dilatometry. Results indicated that at 1000°C, the maximum material densification and properties were obtained after about 15 min of dwell time. Therefore, a quantitative study of crystalline phases nucleated during this period was realised by X-ray diffraction methods. It revealed that anorthite is the most important phase formed during the firing time. Therefore, the nucleation mechanism, mostly involving quartz, but also gehlenite consumption was discussed. At the low firing temperature, it appears that the firing process is characterised by the absence of a liquid phase, drastically limiting the diffusion effect. As a consequence, the sample microstructure, as observed by SEM, shows a network of small dense zones, including quartz grains, interconnected by recrystallized porous phases. The comparison of material containing the natural kaolinitic clay to material obtained from pure reference minerals underlined the important role of iron impurities in anorthite formation.     

Novel process for selective separation of trace artemisitene from artemisinin by ammonium functional ionic liquids

One of the challenges to obtain high-quality natural active substances is the selective separation of the target compound from its analogues. In this study, ionic liquids (ILs), with design flexibility, were proposed to separate artemisitene and artemisinin, typical examples of natural analogues. Based on COSMO-RS calculation, several ILs were selected to separate artemisitene/artemisinin by experiment. It was demonstrated that the aqueous solution of N-allyl-N,N,N-trimethylammonium chloride ([AA][Cl]) exhibited excellent capability for selective separation of the two compounds. Under the optimal conditions (40°C, 1 h), the separation selectivity of artemisitene/artemisinin could reach 12.23 when the initial impurity content was only 0.8 wt%. Spectroscopic analysis and molecular dynamics indicated that π–π complexation between artemisitene and [AA][Cl] plays a major role in this separation process. Moreover, the process of multistage cross-flow extraction was compared with counter-flow extraction, and the latter one exhibited advantages in energy consumption and product yield.     

色谱大剂量直接进样分析水中微量烃

在气相色谱上进行大剂量水样 (10～ 10 0 μL)的直接进样来分析水中的烷烃 ,发现选择合适的固定相和较低的柱温时 ,样品的色谱峰可以不受水峰干扰。己烷的最小检出量为 0 .15mg/L ,相对标准偏差为 6.4%。用外标法测定了室温下水中烷烃的溶解度数据 ,与文献值接近。其中正壬烷的数据未见文献报道     

Determination of trace amounts of fatty acids in edible oils by capillary gas-liquid chromatography

The effect of using different gas-liquid chromatography (GLC) hardware to quantify low concentrations of fatty acids was studies. A fused-silica capillary column was operated in two different chromatographs (A and B) that were interfaced to three different chromatographic data systems to process the flame-ionization detector signals (systems A, B1, and B2). A test routine was developed that allowed the proper selection of peak processing parameters for the automatic recognition and integration of fatty acids occurring at trace levels. However, agreement of analytical results between the three analytical systems was not satisfactory; components at concentrations <0.10 g/100 g could not be quantified with high reliability, although the same capillary column and identical sample solutions were used (quasi-repeatability conditions). Even for major fatty acids, deviations up to 1.0 g/100 g were noted, which could only be attributed to the use of different GLC hardware. Attention should be paid to these technical restrictions when formulating product specifications based on fatty acid profile parameters.     

Estimation of diffusion coefficients for trace amounts of solvents in glassy and molten polymers

Two methods based on the free-volume theory of transport are developed for the estimation of diffusion coefficients for trace amounts of solvents in amorphous polymers. The first method uses diffusivity data for a polymer–solvent system above the glass transition temperature to estimate the temperature dependence of the mutual diffusion coefficient below this temperature. In the second method, mutual diffusion coefficients are estimated for a particular polymer–solvent system both above and below the glass transition temperature using no diffusivity data for the system. The predictions of the proposed theory are compared with diffusivity data for the n-pentane–polystyrene and ethylbenzene–polystyrene systems.