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301.
Summary Plots of capacity factor and retention time vs. elution solvent composition were proved to be useful to interpret the retention
behavior of Kepone and its metabolites in a reversed-phase solid-phase extraction and to optimize the elution solvent. The
percent recovery of Kepone was largely improved when the solvent was optimized. The standard deviations of the results of
extractions were also improved upon the optimization of the solvent. 相似文献
302.
Presti ML Ragusa S Trozzi A Dugo P Visinoni F Fazio A Dugo G Mondello L 《Journal of separation science》2005,28(3):273-280
Traditional hydrodistillation (HD), supercritical fluid extraction (SFE), organic solvent extraction (SE), and water microwave assisted hydrodistillation (MAHD) techniques were compared and evaluated for their effectiveness in the isolation of rosemary essential oil. The microwave assisted hydrodistillation technique was optimized in terms of both delivered power and time duration. The extracts/distillates were analyzed by GC and GC-MS. Microwave distillation, which exploits the physical action of microwaves on plants, showed a series of advantages over the other approaches: low cost, use of water in sample pre-treatment step, greatly reduced isolation time, and attainment of high quality essential oil distillate. Moreover, the absence of environmental impact of this innovative technique was also emphasized. 相似文献
303.
Philippe Quevauviller Gemma Rauret Allan Ure Roser Rubio José-Fírmin López-Sánchez Haidé Fiedler Herbert Muntau 《Mikrochimica acta》1995,120(1-4):289-300
The determination of extractable trace metal contents in soil using single extraction procedures is currently performed in many laboratories to assess the bioavailable metal fraction (and related phytotoxic effects) and the accessability to the environment (e.g. contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determination of extractable trace metal contents in soil, the first step being an interlaboratory study to adopt common extraction procedures and the second being a certification campaign to certify two soils for their extractable trace element contents following these procedures. This paper gives a brief overview of the project organisation and describes the preparation, homogeneity and stability studies of two soil candidate reference materials (sewage sludge-amended and terra rossa soils). 相似文献
304.
Summary A rapid and efficient procedure is described for extraction and determination of aminocaproic acid in horse urine. Urine was
extracted by passing through a bonded silica column (Bond-Elut). The adsorbed drug was washed free of endogenous materials
before being eluted. The extract was then examined by thin-layer chromatography and HPLC. The purity of the extract was determined
by gas chromatography-mass spectrometry. 相似文献
305.
改进的微波辅助无溶剂法提取薄荷和陈皮中的挥发油组分 总被引:1,自引:0,他引:1
An improved solvent free microwave extraction, in which a kind of microwave absorption medium (carbonyl iron powder) was used, was applied to the extraction of essential oil from dried menthol mint and orange peel without addition of any solvent and pretreatment. It took much less time of extraction (30 min) than microwave-assisted hydrodistillation (90 min) and conventional hydrodistillation (180 min). The kinds of chemical compositions in essential oil extracted by different methods were almost the same and such improved solvent free microwave extraction can be a feasible way in extraction of essential oil from dried plant materials. 相似文献
306.
The carbamoyl methyl sulfoxide compounds of uranyl bis(β-diketonate) of the types [UO2(DBM)2CMSO] and [{UO2(DBM)2}2CMSO] (where HDBM = C6H5COCH2COC6H5; CMSO = C6H5CH2SOCH2CONHC6H5 or C6H5SOCH2CONiPr2) have been synthesized and characterized by IR and NMR spectroscopic techniques and elemental analysis. Spectral studies show that CMSO acts as a monodentate ligand in [UO2(DBM)2CMSO] compounds and bonds through the sulfoxo oxygen atom to the uranyl group. It acts as a bridging bidentate ligand in [{UO2(DBM)2}2CMSO] compounds and bonds through both the sulfoxo and carbamoyl oxygen atoms to two different uranyl groups. The structure of the compound [{UO2(DBM)2}2C6H5CH2SOCH2CONHC6H5] confirms the bridging bidentate mode of coordination for the CMSO ligand. Extraction studies show an enhancement in solvent extraction for the uranyl ion from nitric acid medium when a mixture of thenoyl trifluoroacetone (HTTA) and CMSO was employed. 相似文献
307.
Shoichi Katsuta Hirokazu Wakabayashi Mariko Tamaru Yoshihiro Kudo Yasuyuki Takeda 《Journal of solution chemistry》2007,36(4):531-547
Equilibria concerning picrates of tetraalkylammonium ions (Me4N+, Et4N+, Pr4N+, Bu4N+, Bu3MeN+) in a dichloromethane−water system have been investigated at 25 ∘C. The 1:1 ion-pair formation constants (K
IP,o
o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K
D
o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K
IP,o
o value varies in the cation sequence, Bu4N+ ≈ Pr4N+ ≈ Et4N+ < Bu3MeN+ < < Me4N+; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs
determined by density functional theory calculations. For the ion pairs of the symmetric R4N+ cations, there is a linear positive relationship between log10
K
D
o and the number of methylene groups in the cation (N
CH
2). The ion pair of asymmetric Bu3MeN+ has a higher distribution constant than that expected from the above log10
K
D
o
versus
N
CH
2 relationship. These cation dependencies of log10
K
D
o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log10
K
D
o value of the free cation increases linearly with N
CH
2; the variation of log10
K
D
o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one,
and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies
of the ion-pair extractability and ion pairing in water are also discussed.
An erratum to this article can be found at 相似文献
308.
Ali MOGHIMI Mohammad SABER‐TEHRANI Syed WAQIF‐HUSAIN Majid MOHAMMADHOSSEINI 《中国化学》2007,25(12):1859-1865
A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples. 相似文献
309.
Kanchi Suvardhan Kailasa Suresh Kumar Dasari Rekha Pantrangam Subrahmanyam Kapuvedi Kiran Bellum Jayaraj Surasura Ramanaiah Kandhukuri Janardhanam Pattium Chiranjeevi 《Mikrochimica acta》2007,157(3-4):237-244
Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate
(2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed
with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished
by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully
applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL
sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL−1. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL−1), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium
in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test. 相似文献
310.
Chromatographic behaviour of six selected herbicides (chlortoluron, metoxuron, chloridazon, simazine, propazine and atrazine) was studied by reversed-phase (RP) high-performance liquid chromatography (HPLC) containing Genapol X-080 non-ionic surfactant as methanol/water mobile phase constituent. The concentration of methanol was changed from 50 to 0% (v/v) for constant 2% (v/v) concentration of the surfactant. The surfactant concentration in purely aqueous micellar mobile phase varied from 1 to 5% (v/v) what is approximately 360-1800 times above the CMC. Within this concentration range Genapol X-080 proves concentration dependent selectivity changes for chlortoluron/atrazine critical pair not occurred in hydro-methanolic mobile phases. Further studies revealed that this chromatographic system offers high compatibility with cloud-point extraction environmental sample pretreatment approaches using Genapol X-080 for the purpose, too. 相似文献