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71.
The preliminary results described here show the complete transfer of Hg(II) ions, in the absence of a chelating agent in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids; the lag time required to gain the quantitative metal ion partition turned out to be strongly dependent both on alkyl chain length on the imidazolium ring and on the working temperature. 相似文献
72.
研究了由4,4'-癸二酰-双-(1-苯基-3-甲基-5-吡唑啉酮)(DBPMP,简作H2A),氧化三辛基膦(TOPO),吡啶(Py)组成的三元体系从硝酸溶液中对铀的协同萃取,斜率法确定萃合物组成为UO2A.TOPO.Py,制取了固体协萃配合物,并用元素分析、IR及HNMR等进行了表征。 相似文献
73.
Summary In this study, a rapid and efficient semi-micro extraction procedure is presented for the extraction of some higher n-alkanes
from water and soil samples. In the case of water samples n-hexane was used as the organic phase in a phase volume ratio (volume
of aqueous phase/volume of organic phase) higher than 285, while in the case of soil samples, extraction with n-hexane was
carried out in the presence of an excess of 2 M NaCl solution. The extraction rate from soil samples is very high and is better
than Soxhlet extraction, comparable with supercritical fluid extraction. High preconcentration factor in water samples allows
the limits of detection to be in the ng.mL−1 level with the use of gas chromatographic analysis. Flame ionization detector was used for monitoring the analytes. The obtained
recoveries of all studied compounds from both water and soil samples are higher than 90%. This method was successfully used
to determine some n-alkanes in municipal wastewater and contaminated soil. 相似文献
74.
A solution-phase synthesis of bicyclic prolines containing four points of diversity has been developed by a two-step synthesis involving 1,3-dipolar cycloaddition of perfluoroalkylsulfonyl-protected hydroxybenzaldehydes followed by Pd-catalyzed Suzuki coupling reaction of fluorous sulfonates with boronic acids. Both reactions are conducted under microwave irradiation and reaction mixtures are purified by solid-phase extractions without performing chromatography. 相似文献
75.
A new method for the determination of trace cadmium in water samples by flame atomic absorption spectrometry (FAAS) after
cloud point extraction (CPE) is proposed. The method is based on the complexation of Cd with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone
(PMBP) in the presence of non-ionic micelles of Triton X-100. The effect of experimental conditions such as pH, concentration
of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. Under the optimum
conditions, the detection limits are 0.64 ng mL±1 with relative standard deviations (RSDs) of 2.1% (n = 10). The proposed method was applied to the determination of trace
cadmium in water samples with satisfactory results. 相似文献
76.
Yasuyuki Takeda Chihiro Takagi 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(1):93-97
The theory is derived to determine the dimer-formation constant,K
2, of a crown ethermetal salt 111 complex in organic solvents of low dielectric constant by solvent extraction. The theoretical predictions are verified experimentally by extraction of sodium picrate (NaA) with 15-crown-5 (15C5) into carbon tetrachloride. All the experiments were conducted at 25°C. The logK
2 value of the Na(15C5)A complex in carbon tetrachloride has been determined to be 4.05±0.11. Moreover, the partition constant of the complex is calculated. 相似文献
77.
The acetone-butanol production by simultaneous saccharification and extractive fermentation (SSEF) was investigated. In the
SSEF employing cellulase enzymes andClostridium acetobutylicum, both glucan and xylan fractions of pretreated aspen are concurrently converted into acetone and butanol. Continuous removal
of the fermentation products from the bioreactor by extraction was an important factor that allowed long-term fed-batch operation.
The use of membrane extraction prevented the problems of phase separation and extractant loss. Increase in substrate feeding
as well as reduction of nutrient supply was found to be beneficial in suppressing the acid production, thereby improving the
solvent yield. Because of prolonged low growth conditions prevalent in the fed-batch operation, the butanol-to-acetone ratio
in the product was significantly higher at 2.6–2.8 compared to the typical value of two. 相似文献
78.
人参中总皂甙的超声波快速提取方法研究 总被引:7,自引:0,他引:7
建立了人参中总皂甙超声波半微量快速提取方法,与索氏提取法相比,此法提取时间由索氏法的1-2个工作日缩短到30min,节省大量试剂,综合提取效率提高数十倍,与索氏提取法对照分析表明,此法可完全满足人参中总皂甙的快速测定要求。 相似文献
79.
Sequential extraction of phosphorus in soil and sediment using a continuous-flow system 总被引:1,自引:0,他引:1
Distribution and mobility of phosphorus in soil and sediment are usually studied by sequential extraction. In the extraction procedure, a sample is treated with a series of reagents to distinguish the phases to which phosphorus is associated such as carbonate and iron or manganese oxides, etc. There have been a number of extraction schemes presented for phosphorus. At present, all of the existing schemes are carried out batchwise. Phosphorus contents derived from all sequences are operationally defined and depend on experimental conditions.An extraction procedure, which is a continuous-flow-based technique, was recently proposed by our group for metals in soils and sediments. The extraction is carried out in a closed chamber through which extractants are passed sequentially. In this paper, the system was investigated using the extraction scheme of Hieltjes and Lijklema to study distribution of phosphorus in three certified reference materials (CRMs). A number of fractions were collected for each reagent for subsequent colorimetric determination. The results are compared with those obtained from a batch extraction. The summation of phosphorus contents of all phases were compared with the certified values and with the values obtained from total digestion. These results have demonstrated that the continuous extraction system developed is also applicable for fractionation of phosphorus. Advantage and disadvantage are discussed. 相似文献
80.
Three acyclic polythioethers containing 2-thienyl units at both ends were synthesized and the effect of substituent on the extraction of copper(II) was studied. The methyl groups in the terminal thiophene ring have imparted an appreciable degree of increase in the percent extraction of copper(II), while the introduction of chlorine atoms into the 2-thienyl unit resulted in the reverse effect. Among the counter dye anions examined, tetrabromophenolphthalein ethylester was the best one for copper(II) extraction. The composition of extracted species was evaluated to be 122 (Cu(II)/polythioether/dye anion). Quantitative extraction of copper(I) was attained as complexes with various triphenylmethane dyes, i.e., bromocresol green, bromothymol blue, bromo-phenol blue and pyrogallol red. Copper(I) in organic phase was completely back-extracted with 2 mole/l sulfuric acid containing 10% hydrogen peroxide. 相似文献