Physicochemical Principles of Extraction with Supercritical Gases

The present review considers some physicochemical properties of fluid mixtures that are of importance for fluid extraction and supercitical fluid chromatography (SFC). Firstly, the important types of phase diagrams are treated, the occurrence of solid phases also being considered in some simple cases. Specific examples are given of mixtures of a highly volatile component I (e.g. CO₂, C₂H₆) with a relatively involatile component II (e.g. squalane) of very different molecular size, shape, structure, and/or polarity, and it is shown how the rather complicated types of phase diagrams can be calculated and correlated. The importance of fluid mixtures extends far beyond the fields of science and technology reviewed.     

两相滴定法研究2-乙基己基膦酸单2-乙基己基酯从盐酸介质中萃取钕(Ⅲ)的动力学

本文利用两相滴定法作为分析手段,用恒界面池搅拌法考察了多种因素对2-乙基己基膦酸单2-乙基己基酯(HEHEHP,HA)从盐酸介质中萃取Nd(Ⅲ)动力学的影响,从实验结果推论出萃取过程为界面化学反应控制型机理。     

Sample preparation for organic acids in biological fluids

A review of sample preparation methods for organic acids in biological fluids, in particular serum and urine, is presented. It covers techniques on organic acid determination without sample preparation, release of organic acids from binding locations, removal of proteins by protein precipitation and ultrafiltration, isolation of the organic acids by liquid-liquid and liquid-solid extraction, purification of the extract, derivatization and pre-fractionation. The various alternative sample preparation steps are compared and critically discussed. Examples of applications including profile analysis of organic acids by gas chromatography (GC), determination of particular organic acids by GC or liquid chromatography and determination of fatty acids as a distinct chemical class of acids demonstrate that the kind of sample preparation chosen depends strongly on the analytical aims.     

三正辛胺(TOA)分离贵金属的系统研究 Ⅰ.反相萃取色层法分离七个贵金属

本文系统详细地研究了七种贵金属彼此分离以及与贱金属分离的可能条件。此种工作尚未见报道。用三正辛胺作固定相。分别用1mol/L HCl、6mol/LHCl、2mol/L HNO_3—2mol/L HCl、3mol/L HNO_3-2mol/L HCl、4mol/L HNO_3-2mo1/L HCl和5％硫脲-1mol/L HCl为淋洗液,可以将Rh、Ru、Pd、Pt、Ir、Os、Au分步淋洗下来,达到彼此完全分离。为了使Rh(Ⅱ)与贱金属分离,必须将RhC1_6~(3-)转化为RhBrb_6~(3-),然后在另一色层柱上使它与贱金属分离。合成矿样的分析结果符合分析要求。     

Dynamic headspace liquid-phase microextraction of alcohols

A method was developed using dynamic headspace liquid-phase microextraction and gas chromatography-mass spectrometry for extraction and determination of 9 alcohols from water samples. Four different solvents, hexyl acetate, n-octanol, o-xylene and n-decane were studied as extractants. The analytes were extracted using 0.8 microl of n-octanol from the headspace of a 2 ml sample solution. The effect of sampling volume, solvent volume, sample temperature, syringe plunger withdrawal rate and ionic strength of the solution on the extraction performance were studied. A semiautomated system including a variable speed stirring motor was used to ensure a uniform movement of syringe plunger through the barrel. The method provided a fairly good precision for all compounds (5.5-9.3%), except methanol (16.4%). Detection limits were found to be between 1 and 97 microg/l within an extraction time of approximately 9.5 min under GC-MS in full scan mode.     

Rapid determination of panaxynol in a traditional Chinese medicine of Saposhnikovia divaricata by pressurized hot water extraction followed by liquid-phase microextraction and gas chromatography-mass spectrometry

Panaxynol is a bioactive component in traditional Chinese medicines (TCMs), such as Saposhnikovia divaricata and Panax ginseng. In the work, two solvent-free sample techniques of pressurized hot water extraction (PHWE) and headspace liquid-phase microextraction (HS-LPME) were combined and developed for the determination of panaxynol in a TCM of S. divaricata. Panaxynol in the TCM samples from different growing areas was extracted by PHWE in dynamic mode, followed by extraction and concentration with HS-LPME and analysis with gas chromatography-mass spectrometry (GC-MS). The PHWE and HS-LPME parameters were optimized and the method validations were studied. Panaxynol in S. divaricata from four different growing areas was quantitatively analyzed by internal standard method. These results have shown that PHWE-LPME-GC-MS is a simple, rapid, efficient and low-cost method for the determination of panaxynol in TCMs and is a potential tool for TCM quality assessment.     

Three-phase extraction study of cyanex 923-n-heptane/H(2)SO(4) system

Phase behavior of the extraction system, Cyanex 923–heptane/H₂SO₄–H₂O has been studied. The third phase appeared at different aqueous H₂SO₄ concentration with varying initial Cyanex 923 concentration and temperature affects its appearance. Almost all of H₂SO₄ and H₂O are extracted into the middle phase. The H₂SO₄ concentration in the third phase increases with the increasing aqueous acid concentration (C_H2SO4,b) while the water content first increases and then reaches a constant value at C_H2SO4,b=11.3 mol l⁻¹. In the region of C_H2SO4,b higher than 5.2 mol l⁻¹, the composition of the middle phase is only related to the equilibrium concentration of H₂SO₄ in the bottom phase. H₂SO₄ and H₂O are transferred into the middle phase mainly by their coordination with Cyanex 923 when C_H2SO4,b is less than 11.3 mol l⁻¹. When C_H2SO4,b is higher than 11.3 mol l⁻¹, excess H₂SO₄ is solubilized into the polar layer of the aggregates. In the region considered, the extracted complex changes from C923 · H₂SO₄ to C923 · H₂SO₄ · H₂O and then to C923 · (H₂SO₄)₂ · H₂O.     

2-乙基己基磷酸单(2-乙基己基)酯萃淋树脂分离-火花源质谱法测定高纯氧化镱中痕量稀土杂质

本文采用萃取色谱法以2-乙基已基膦酸单(2-乙基已基)酯(P_507)萃淋树脂为固定相,以HCI-NH_4CI体系为淋洗液,研究了99.999%~99.9999%的高纯Yb_2O_3中稀土杂质和Yb基体的分离条件,将杂质淋洗液富集于复合螯合剂-活性碳上,经灼烧灰化后制成样品电极,进行质谱测定.测定下限达 0.01~0.05 μg/g,可用于高纯 Yb_2O_3中杂质的测定.回收率在80%以上.     

Sample preparation for metalloprotein analysis: A case study using horse chestnuts

In the present work, 11 different procedures for protein and metalloprotein extraction from horse chestnuts (Aescullus hippocastanum L.) in natura were tested. After each extraction, total protein was determined and, after protein separation through sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), those metals belonging to the protein structure were mapped by synchrotron radiation X-ray fluorescence (SRXRF). After mapping the elements (Cr, Fe and Mn) in the protein bands (ca. 33 and 23.7 kDa), their concentrations were determined using atomic absorption spectrometry (ET AAS).

Good results were obtained for protein extraction using a combination of grinding and sonication. However, this strategy was not suitable to preserve metal ions in the protein structure. In fact, there was 42% decrease on Mn concentration using this procedure, compared to that performed with sample agitation in water (taken as reference). On the other hand, when grinding and agitation with an extracting buffer was used, there was a 530% increase of Mn concentration, when compared to the reference procedure.

These results indicate agreement between metal identification and determination in proteins as well as the great influence of the extraction procedure (i.e., the sample preparation step) for preserving metals in the protein structures.     

Determination of nonylphenol and octylphenol in paper by microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-mass spectrometry

A novel and simple method for the determination of active endocrine disrupter compounds (octylphenol OP, and nonylphenol NP) in paper using microwave-assisted extraction (MAE) and headspace solid-phase microextraction, coupled with gas chromatography-mass spectrometry has been developed. Parameters affecting the efficiency in the MAE process such as exposure time and extraction solvent were studied in order to determine operating conditions. The optimised method was linear over the range studied (1.25-125 microg kg(-1) for OP and 9.50-950 microg kg(-1) for NP) and showed good level of precision, with a RSD lower than 10% and detection limits at 0.10 and 4.56 microg kg(-1) for OP and NP, respectively. The results obtained from six different types of paper revealed the presence of the target compounds in all samples analysed, at levels ranging between 3 and 211 microg kg(-1).