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1.
G. Woelki S. Friedrich G. Hanschmann R. Salzer 《Fresenius' Journal of Analytical Chemistry》1997,357(5):548-552
Different soil extracted humic acids as well as a commercial humic acid sodium salt were fractionated by HPLC. An almost
complete recovery could be achieved for the dissolved material. All humic samples show a typical chromatogram of at least
five fractions. The separation of humic substances is influenced by an altered hydrophobicity due to changes in the tertiary
structure. Three fractions were further investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy
and by HPLC/HPLC separation. DRIFT spectroscopy provided data on the primary structure, whereas HPLC/HPLC results gave insight
into the secondary and tertiary structure and their changes.
Received: 18 June 1996 / Revised: 9 October 1996 / Accepted: 12 October 1996 相似文献
2.
Determination of heavy metal complexes with humic substances by HPLC/ICP-MS coupling using on-line isotope dilution technique 总被引:3,自引:0,他引:3
An isotope dilution mass spectrometric (IDMS) method has been developed for the simultaneous determination of the complexes
of 11 heavy metals (Ag, Cd, Cu, Mo, Ni, Pb, Tl, U, W, Zn and Zr) with humic substances (HS) by coupling HPLC with ICP-MS and
applying the on-line isotope dilution technique. The HPLC separation was carried out with size exclusion chromatography. This
HPLC/ICP-IDMS method was applied to samples from a brown water, ground water, sewage and seepage water as well as for a sample
containing isolated fulvic acids. The total contents of heavy metals and of their complexes were analyzed in these samples
with detection limits in the range of 5–110 ng/L. The analysis of heavy metal/HS complexes from the different waters resulted
in characteristic fingerprints of the distribution pattern of heavy metals in the separated HS fractions. A comparison between
the total heavy metal concentrations and their portions bound to humic substances showed distinct differences for the various
metals. Simultaneous 12C detection was used for the characterization of HS complexes not identified by UV detection and for the determination of
relative DOC concentrations of chromatographic peaks.
Received: 21 February 1997 / Revised: 27 May 1997 / Accepted: 28 May 1997 相似文献
3.
Mohammad A. Mottaleb B. G. Cooksey David Littlejohn 《Fresenius' Journal of Analytical Chemistry》1997,358(4):536-538
A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared
spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and
the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm
width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer,
enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of
the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal
degradation was observed.
Received: 20 May 1996 / Revised: 17 October 1996 / Accepted: 28 November 1996 相似文献
4.
《Journal of separation science》2003,26(5):429-432
This communication reports a study of the effect of ionic strength and electrolyte composition on fractions, separately collected by flow FFF, of a mixture of humic substances. Reverse phase HPLC analysis of three early eluting fractions suggests that the components released by the column behave as organic acids. The baseline‐resolved peaks of the first two fractions, subject to higher retention in solutions of lower pH and/or higher polarity, substantiate this suggestion. The fraction with larger components, as measured by flow FFF, also appears to contain acidic species. Their retention level, however, may not be accurately modulated by varying the mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH ≥ 4.2. Besides showing the effective separation achieved in the flow FFF channel, this study reveals the pronounced difference in the physicochemical properties of some components of a humic mixture even with very close particle size. 相似文献
5.
Recovery as well as appearance and abundance (in percent) of different fractions of humic substances are found to depend on injected sample amounts in reversed phase HPLC. Sample amounts have been varied both by varying sample concentration and sample volume. In case of lowest amounts injected only two fractions were obtained for a commercial humic acid sodium salt, i.e. one for excluded molecules and one for hydrophobic components. The abundance of excluded molecules decreases upon increasing amounts injected. Another three fractions are obtained upon increasing amount injected: a hydrophilic fraction and two hydrophobic ones. This behavior is explained by auxiliary equilibria between excluded components and humic molecules previously adsorbed on the stationary phase. 相似文献
6.
7.
B. W. Wenclawiak Torsten Hees Corinna E. Z?ller Hans-Peter Kabus 《Fresenius' Journal of Analytical Chemistry》1997,358(4):471-474
An on-line system of supercritical fluid extraction (SFE) and high performance liquid chromatography (HPLC) via solid phase
extraction (SPE) is described for the determination of palladium and rhodium 2,2,6,6-tetramethyl-3,5-heptanedione-(thd) as
well as rhodium-acetylacetonate-(acac) and benzylacetonate-(bzac) chelates. The chelates were extracted with supercritical
CO2 from sand and humic acid, concentrated on SPE cartridges and analysed with HPLC. Two cartridge materials were tested and
compared to off-line trapping. The percentage of the breakthrough and cartridge retained material were measured in liquid
dichloromethane. The SFE conditions could be optimized to separate metal chelates during the extraction. The supercritical
fluid (SF) behaviour of different ligands on rhodium were investigated.
Received: 19 July 1996/Revised: 11 December 1996/Accepted: 14 December 1996 相似文献
8.
A. Prei? U. Lewin L. Wennrich M. Findeisen J. Efer 《Fresenius' Journal of Analytical Chemistry》1997,357(6):676-683
It is shown that by using high-field proton nuclear magnetic resonance (1H-NMR) spectroscopy it is possible, without prior separation, to analyse nitrophenols and other acidic nitroaromatic compounds
in the “pH 2 extract” of ammunition wastewater. The 1H-NMR chemical shifts data of a variety of reference compounds are presented. Two groundwater samples from the former ammunition
plant in Elsnig (Saxony) were analysed by 1H-NMR and also by chromatographic methods (GC/MS, HPLC). The results are compared and discussed.
Received: 17 January 1996/Revised: 15 May 1996/Accepted: 17 May 1996 相似文献
9.
A. Preiß U. Lewin L. Wennrich M. Findeisen J. Efer 《Analytical and bioanalytical chemistry》1997,357(6):676-683
It is shown that by using high-field proton nuclear magnetic resonance (1H-NMR) spectroscopy it is possible, without prior separation, to analyse nitrophenols and other acidic nitroaromatic compounds
in the “pH 2 extract” of ammunition wastewater. The 1H-NMR chemical shifts data of a variety of reference compounds are presented. Two groundwater samples from the former ammunition
plant in Elsnig (Saxony) were analysed by 1H-NMR and also by chromatographic methods (GC/MS, HPLC). The results are compared and discussed.
Received: 17 January 1996/Revised: 15 May 1996/Accepted: 17 May 1996 相似文献
10.
The chromatographic fractionation of aquatic humic substances (HS) onto iron(III)-coated cellulose (Cell-Fe(III)) as a metal-loaded
adsorbent is described, analogously to the separation principle of the well-established metal affinity chromatography (MAC).
For that purpose the sorption of HS from different aquatic origin on that collector was characterized by their kinetics and
equilibrium distribution coefficients Kd. Based on Kd values of 103 to 104,mL/g, and fast sorption kinetics a preparative HPLC procedure, using stepwise increased pH-values (pH 8–12.5, borate buffer)
as an eluent, was developed for the fractionation of dissolved HS (up to 7 fractions of different amount). The fractions obtained
by this MAC procedure from selected aquatic HS samples were different in their Cu(II) complexation capacity, absorbance ratio
E265 nm/E365 nm and Fourier transform infrared spectra.
Received: 14 June 1999 / Revised: 6 August 1999 / Accepted: 10 August 1999 相似文献
11.
The chromatographic fractionation of aquatic humic substances (HS) onto iron(III)-coated cellulose (Cell-Fe(III)) as a metal-loaded
adsorbent is described, analogously to the separation principle of the well-established metal affinity chromatography (MAC).
For that purpose the sorption of HS from different aquatic origin on that collector was characterized by their kinetics and
equilibrium distribution coefficients Kd. Based on Kd values of 103 to 104,mL/g, and fast sorption kinetics a preparative HPLC procedure, using stepwise increased pH-values (pH 8–12.5, borate buffer)
as an eluent, was developed for the fractionation of dissolved HS (up to 7 fractions of different amount). The fractions obtained
by this MAC procedure from selected aquatic HS samples were different in their Cu(II) complexation capacity, absorbance ratio
E265 nm/E365 nm and Fourier transform infrared spectra.
Received: 14 June 1999 / Revised: 6 August 1999 / Accepted: 10 August 1999 相似文献
12.
Montserrat Baucells Núria Ferrer Pilar Gómez Gloria Lacort Montserrat Roura 《Mikrochimica acta》1993,112(1-4):87-98
Fourier transform infrared spectroscopy has been used for the quantitative determination of caffeine in several pharmaceutical products: acetyl salicylic acid, paracetamol and propyphenazone. The method is simple, rapid and selective, and allows the determination of caffeine without sample pretreatment and without separation from the matrix. Two techniques for measuring the infrared spectra of caffeine are described: transmission through pellets and diffuse reflectance from powder (DRIFT). In both methods, samples were diluted (1%) with KBr. Caffeine in pharmaceutical matrices was recovered within 5% error in pellets and 10% by DRIFT. Relative standard deviations were generally 1.5% for repeated measurements on a single pellet and 5% for measurements on different pellets. DRIFT in the vacuum mode gave rather large RSDs. The limit of detection of the pellet technique was about 0.5% caffeine in the original sample. 相似文献
13.
Unambiguous detection of astaxanthin and astaxanthin fatty acid esters in krill (Euphausia superba Dana) 总被引:1,自引:0,他引:1
Grynbaum MD Hentschel P Putzbach K Rehbein J Krucker M Nicholson G Albert K 《Journal of separation science》2005,28(14):1685-1693
HPLC atmospheric pressure chemical ionization (APCI)/MS, GC MS, HPLC diode array detection (DAD), and NMR were used for the identification of astaxanthin and astaxanthin fatty acid esters in krill (Euphausia superba Dana). Matrix solid phase dispersion was applied for the extraction of the carotenoids. This gentle and expeditious extraction technique for solid and viscous samples leads to distinct higher enrichment rates than the conventional liquid-liquid extraction. The chromatographic separation was achieved employing a C30 RP column that allows the separation of shape-constrained geometrical isomers. A methanol/tert-butylmethyl ether/water gradient was applied. (all-E) Astaxanthin and the geometrical isomers were identified by HPLC APCI/MS, by coelution with isomerized authentical standard, by UV spectroscopy (DAD), and three isomers were unambiguously assigned by microcoil NMR spectroscopy. In this method, microcoils are transversally aligned to the magnetic field and have an increased sensitivity compared to the conventional double-saddle Helmholtz coils, thus enabling the measurement on small samples. The carotenol fatty acid esters were saponified enzymatically with Lipase type VII from Candida rugosa. The fatty acids were detected by GC MS after transesterification, but also without previous derivatization by HPLC APCI/MS. C14:0, C16:0, C16:1, C18:1, C20:0, C20:5, and C22:6 were found in astaxanthin monoesters and in astaxanthin diesters. (all-E) Astaxanthin was identified as the main isomer in six fatty acid ester fractions by NMR. Quantitation was carried out by the method of internal standard. (13-cis) Astaxanthin (70 microg/g), 542 microg/g (all-E) astaxanthin, 36 microg/g unidentified astaxanthin isomer, 62 microg/g (9-cis) astaxanthin, and 7842 microg/g astaxanthin fatty acid esters were found. 相似文献
14.
D. Tonelli Renato Seeber Claudio Ciavatta Carlo Gessa 《Analytical and bioanalytical chemistry》1997,359(7-8):555-560
Fractions of humic acids, resolved by ultrafiltration of extracts from a sample of peat treated with alkaline pyrophosphate
solution, have been submitted to high-performance size-exclusion chromatography, with the aim of determining the molecular
weight distributions. Anomalous peaks, located at retention volumes higher than those corresponding to the main signal, are
present in the elution profiles relative to the lightest fractions. These peaks are more intense when using a refractive index
detector rather than a UV detector. Elemental analysis data for the lightest fractions suggested that the spurious peaks are
due to the presence of inorganic material. The hypothesis that pyrophosphate interacts with humic acids in the course of the
extraction has been confirmed by colorimetric determination of the phosphorus content in the different fractions. As a consequence,
the extraction procedure has been modified by using 0.1 mol/L NaOH as extractant.
The average molecular weights of the various fractions, following NaOH extraction, result in substantial agreement with those
obtained following pyrophosphate solution extraction (if the ‘pyrophosphate peaks’ present in the chromatographic profile
are discarded in the calculations).
Received: 18 November 1996 / Revised: 18 February 1997 / Accepted: 23 February 1997 相似文献
15.
HPLC approach for revealing age-related changes of aquatic dissolved organic matter in sediment core
Analytical method based on HPLC has been used to characterize aquatic dissolved organic matter (DOM) from sediment core of Lake Võrtsjärv, South- Estonia. High-performance size exclusion chromatography (HPSEC) as separation method was coupled with diode-array detection (DAD) and separated molecular fractions of DOM were subject to qualitative and semi-quantitative analysis. Qualitative analysis based on UV- spectra revealed the presence of proteins and humic constituents in separated high molecular weight fraction and aromatic constituents in low molecular weight fraction. Statistical data treatment methods enabled clustering sediment layers into 4 periods according to sediment depth and age. The upper 0-30 cm sediment DOM had statistically relevant differences in comparison to other periods as revealed by lower total peak and humic substances (HS) fraction areas, and molecular weights. Samples from 80-120 cm depth differed from others by decreased low molecular weight (LMW) fraction content. The observed down-core trends suggest polymerization of LMW organic constituents and increasing humification. The statistical analyses revealed that some chromatographic and spectrometric parameters can be used to differentiate between sediment layers and to evaluate environmental changes. 相似文献
16.
Triton X-100 is applied to influenza vaccines at different stages of the manufacturing process to prevent aggregation and
precipitation of biomolecules. Furthermore it is used to disintegrate the virus particles in split vaccine and to guarantee
the homogeneity during production and utilisation. The final concentration of Triton X-100 has to be determined because the
concentration changes in manufacturing process. The determination of the total amount of Triton X-100 as well as the separation
of its ethylene oxide oligomers was possible with high-performance liquid chromatography (HPLC) and capillary electrophoresis
(CE). In HPLC a change of the column and eluent was necessary, in CE different electrolytes were used for the various separation
effects. The HPLC method for the analysis of total Triton was preferred for the quantification of Triton X-100 in influenza
vaccine because of better linearity, reproducibility and detection sensitivity compared to CE. In the end products an average
concentration of 0.117 mg/mL was found.
Received: 19 December 1996 / Revised: 27 February 1997 / Accepted: 6 March 1997 相似文献
17.
Sadiqali Cheruthazhekatt Thijs F. J. Pijpers Vincent B. F. Mathot Harald Pasch 《Analytical and bioanalytical chemistry》2013,405(28):8995-9007
A novel, powerful analytical technique, preparative temperature rising elution fractionation (prep TREF)/high-temperature (HT)-HPLC/Fourier transform infrared spectroscopy (FTIR)/high-performance differential scanning calorimetry (HPer DSC)), has been introduced to study the correlation between the polymer chain microstructure and the thermal behaviour of various components in a complex impact polypropylene copolymer (IPC). For the comprehensive analysis of this complex material, in a first step, prep TREF is used to produce less complex but still heterogeneous fractions. These chemically heterogeneous fractions are completely separated by using a highly selective chromatographic separation method—high-temperature solvent gradient HPLC. The detailed structural and thermal analysis of the HPLC fractions was conducted by offline coupling of HT-HPLC with FTIR spectroscopy and a novel DSC method—HPer DSC. Three chemically different components were identified in the mid-elution temperature TREF fractions. For the first component, identified as isotactic polypropylene homopolymer by FTIR, the macromolecular chain length is found to be an important factor affecting the melting and crystallisation behaviour. The second component relates to ethylene–propylene copolymer molecules with varying ethylene monomer distributions and propylene tacticity distributions. For the polyethylene component (last eluting component in all semi-crystalline TREF fractions), it was found that branching produced defects in the long crystallisable ethylene sequences that affected the thermal properties. The different species exhibit distinctively different melting and crystallisation behaviour, as documented by HPer DSC. Using this novel approach of hyphenated techniques, the chain structure and melting and crystallisation behaviour of different components in a complex copolymer were investigated systematically.
Fractionation and analysis of complex ethylene -propylene copolymers by using HT-HPLC-FTIR and HT-HPLC-HPer DSC 相似文献
18.
Juanéda P 《Journal of chromatography. A》2002,954(1-2):285-289
Silver ion-high-performance liquid chromatography (HPLC) has been commonly used for the separation and the analysis of trans-18:1 isomers in partially hydrogenated oils and milk fat. This paper describes an easy HPLC method using two reversed-phase columns. The cis- and trans-18:1 fatty acids isomers as methyl esters were eluted as two separate fractions. The collected fractions were analysed by gas chromatography (GC). The purity of the two fractions were tested by GC-MS and GC-Fourier transform IR. 相似文献
19.
泥炭土连续碱抽提腐殖酸的分子结构特征 总被引:9,自引:0,他引:9
从Pahokee泥炭土中连续碱抽提分离出8个不同的腐殖酸级分,并对每一级分进行了元素分析、傅里叶变换红外光谱(FTIR)、固态^13C核磁共振(^13CNMR)、高效排阻色谱(HPSEC)等一系列定性、定量研究。结果表明:所分离出的8个腐殖酸级分存在明显的结构性质差异,随提取和蔼的增加,O/C原子比由0.52减少到0.36,H/C原子比由1.05增加到1.52,相应于结构中含氧基团的减少和脂族基的增加,表观分子量也由7.7K增加到22.1K。同时,^13C NMR显示长链脂肪碳结构由无定型向晶型转变。此工作表明在所研究的腐殖酸中可能存在分别具有芳香或脂肪特性的两类腐殖酸结构,每种类型都有不同的分子量分布、元素组成、基团结构和母质来源。在特定的环境因素下,不同类型的腐殖酸会共存于同一体系中,增加了腐殖物质的非均匀性和复杂性。 相似文献
20.
A new p-tert-butyl-calix[8]arene-bonded silica gel stationary phase (CABS) was prepared via 3-glycidoxypropyltrimethoxysilane as a coupling reagent for HPLC. Its structure was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), elemental analysis and thermal analysis. The chromatographic performance of new packing was evaluated by using basic, acidic and neutral aromatic compounds as probes compared with conventional ODS. The results show that the new stationary phase has an excellent reversed-phase property and high selectivities for substituted aromatics compared with ODS, because CABS can provide various sites for the analytes, such as hydrogen-bonding interactions, pi-pi interactions, and inclusion complex, besides hydrophobic interactions. 相似文献