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Trennung von Benzoesäurederivaten aus Pflanzenextrakten über Sephadex G-10-Säulen
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
U. Enkhardt , H. Gräser
Yıl :
1980
Journal of Chromatography A
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DOI : 10.1016/s0021-9673(00)84779-2
ISSN: 0021-9673
Sayı: 3
Cilt: 198
Sayfa: 373-376
Sınıflandırma :
2
Editorial Board
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yıl :
2010
Journal of Chromatography A
Tam Metin
Kaydet Alıntıla
DOI : 10.1016/s0021-9673(10)00349-3
ISSN: 0021-9673
Sayı: 15
Cilt: 1217
Sayfa: CO2
Sınıflandırma :
Çevre %20
Çevre %35
3
Separation of simple ions by gel chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Takeshi Fukuda , Noriyuki Kohara , Yoshihiko Onogi , Hiroshi Inagaki
Yıl :
1990
Journal of Chromatography A
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Kaydet Alıntıla
The chromatographic separation of simple ions by a polymer gel in water was modelled as a liquid—liquid partition process. The model consists of two “homogeneous” phases, a mobile phase of pure eluent and a stationary (gel) phase of a structureless concentrated polymer solution with a few electric charges fixed within it. Thermodynamic considerations and a simplifying approximation yielded a simple description of single-salt systems, which accounted for the chromatographic behaviour of simple ions at low and high concentrations in a systematic fashion. The intoduced notion of “intrinsic distribution coefficients” of ions proved to be useful. The main mechanism of the separation ions is suggested to be the difference in the thermodynamic stabilities of individual ions in the two phases, rather than involving size-exclusion and adsorption effects.
DOI : 10.1016/s0021-9673(01)93270-4
ISSN: 0021-9673
Cilt: 511
Sayfa: 59-68
Sınıflandırma :
4
Determination of ortho- and pryophosphates in liquid artificial fertilizers by high-speed isotachophoresis
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
P. Boček , B. Kaplanová , M. Deml , J. Janák
Yıl :
1978
Journal of Chromatography A
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DOI : 10.1016/s0021-9673(00)89888-x
ISSN: 0021-9673
Sayı: 1
Cilt: 153
Sayfa: 287-288
Sınıflandırma :
5
Continuous chromatography on a packing of plastic fibres
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Elemer Erodös , George Székely
Yıl :
1982
Journal of Chromatography A
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Kaydet Alıntıla
Continuous chromatography has been studied on a bunch of plastic fibres used as mobile stationary phased. The effect of fibre velocity on peak velocity was determined by elution chromatograms. The relation obtained can be used for continuous separations. It was demostrated that the decreasing theoretical plate numbers of peaks coming from moving fibre are due to the decreasing peak velocities. In spite of this the resolution increases.
DOI : 10.1016/s0021-9673(00)82394-8
ISSN: 0021-9673
Sayı: 1
Cilt: 241
Sayfa: 103-112
Sınıflandırma :
Kimya %100
Kromatografi %85
6
Light-emitting diode-based indirect fluorescence detection for simultaneous determination of anions and cations in capillary electrophoresis
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Shih-Ju Chen , Min-Jane Chen , Huan-Tsung Chang
Yıl :
2003
Journal of Chromatography A
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This report presents simultaneous analysis of cations and anions by capillary electrophoresis (CE) in conjunction with indirect fluorescence detection using a blue light-emitting diode (LED), based on the displacement of fluorescein with anionic EDTA–metal complexes and anions. A new focusing system combined with a plastic lens and a 40× objective was developed and used effectively to focus the diverging beam of the LED on the capillary. The optimum compositions for simultaneous analysis of metal ions and anions are the samples prepared in 5 mM borate, pH 9.2, containing 2 mM EDTA and the background electrolytes (BGEs) consisting of 5 mM borate buffer, 5 μM fluorescein, and 1 μM NaCl at pH 9.2. Using this pre-capillary complexation method, the analysis of a sample containing five metal ions and eight anions was accomplished in 8 min, with the relative standard deviation values for the migration times less than 2.0%. The peak heights against the concentrations of the metal ions and anions are linear in 10–1000 and 50–2000 μM, with correlation coefficients better than 0.998, and 0.982, respectively. The limits of detection at a signal-to-noise ratio 3 of up to 14.6 μM for formate and as low as 3.7 μM for Ni2+. The results of the analyses of pond water and a Chinese herbal soup present the advantages of this method, including simplicity, rapidity, reproducibility, and low costs.
DOI : 10.1016/j.chroma.2003.08.033
Anahtar Kelimeler : Light-emitting diode, Fluorescence detection, Detection electrophoresis, electrophoresis, Indirect detection, Fluorescein
ISSN: 0021-9673
Sayı: 1-2
Cilt: 1017
Sayfa: 215-224
Sınıflandırma :
7
Method for the preparation of continuous streams of gaseous calibration mixtures with defined contents of standard substances
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Jiří Vejrosta , Josef Novák
Yıl :
1979
Journal of Chromatography A
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Kaydet Alıntıla
A method for the preparation of gaseous calibration mixtures with defined contents of standard substances is described. An accurately controlled stream of gas (e.g., nitrogen) is drawn at a low flow-rate through a thermostated container filled with a chromatographic support impregnated with the standard substance, thus generating a continuous stream of saturated vapour of the substance. This stream is diluted in a mixing chamber with a large stream of pure gas, and a small fraction of the dilute mixture, separated by means of a splitter, is again diluted with a large stream of pure gas in another mixing chamber. In this two-stage dilution procedure it is possible to prepare mixture containing standard substances at parts per billion concentrations with an error of about 4%. Mixtures containing several standards are obtained through use of a separate saturator for each standard; the concentration ratio of two standard substances can be set to within the range 1:1 to 1:106.
DOI : 10.1016/s0021-9673(00)89432-7
ISSN: 0021-9673
Sayı: 2
Cilt: 175
Sayfa: 261-267
Sınıflandırma :
8
Chromatographic and computational assessment of lipophilicity using sum of ranking differences and generalized pair-correlation
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Filip Andrić , Károly Héberger
Yıl :
2015
Journal of Chromatography A
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Kaydet Alıntıla
Lipophilicity (logP) represents one of the most studied and most frequently used fundamental physicochemical properties. At present there are several possibilities for its quantitative expression and many of them stems from chromatographic experiments. Numerous attempts have been made to compare different computational methods, chromatographic methods vs. computational approaches, as well as chromatographic methods and direct shake-flask procedure without definite results or these findings are not accepted generally. In the present work numerous chromatographically derived lipophilicity measures in combination with diverse computational methods were ranked and clustered using the novel variable discrimination and ranking approaches based on the sum of ranking differences and the generalized pair correlation method. Available literature logP data measured on HILIC, and classical reversed-phase combining different classes of compounds have been compared with most frequently used multivariate data analysis techniques (principal component and hierarchical cluster analysis) as well as with the conclusions in the original sources. Chromatographic lipophilicity measures obtained under typical reversed-phase conditions outperform the majority of computationally estimated logPs. Oppositely, in the case of HILIC none of the many proposed chromatographic indices overcomes any of the computationally assessed logPs. Only two of them (logkmin and kmin) may be selected as recommended chromatographic lipophilicity measures. Both ranking approaches, sum of ranking differences and generalized pair correlation method, although based on different backgrounds, provides highly similar variable ordering and grouping leading to the same conclusions.
DOI : 10.1016/j.chroma.2014.12.073
Anahtar Kelimeler : Lipophilicity, Multivariate data analysis, Sum of ranking differences, Generalized pair correlation method, High-performance liquid chromatography, PC principal component, principal component, SRD sum of ranking (absolute) differences, sum of ranking (absolute) differences, CRRN validation of the SRD procedure: comparison of Ranks by Random Numbers, validation of the SRD procedure: comparison of Ranks by Random Numbers, GPCM generalized pair correlation method (for explanation of the abbreviations see in the text)., generalized pair correlation method (for explanation of the abbreviations see in the text).
ISSN: 0021-9673
Cilt: 1380
Sayfa: 130-138
Sınıflandırma :
9
Effect of channel width on the retention of colloidal particles in polarization, steric, and focusing micro-thermal field-flow fractionation
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
J JANCA , I ANANIEVA , A MENSHIKOVA , T EVSEEVA , J DUPAK
Yıl :
2004
Journal of Chromatography A
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The effect of the channel width on the performance of separation by micro-thermal field-flow fractionation (micro-TFFF) of the carboxylated polystyrene latex particles was studied by using the particles in diameter range from 100 nm to 3800 nm. It has been shown that the retention order follows the anticipated polarization, steric, and focusing mechanism in the corresponding size range and under the specific conditions, appropriate to each channel thickness. However, the attractive interactions of the particles with the accumulation wall can complicate the separation as has been proven by the experiments carried out by using the carrier liquids of different ionic strengths. Three channel thicknesses (0.025, 0.100, and 0.250 mm) were tested thus imposing the volumes of micro-channels of roughly 9, 37, and 92 μl. Such an experimental investigation has never been performed with respect to the applicability of the TFFF within an extended range of molar masses or particle sizes. The advantages and drawbacks of different channel widths are discussed with respect to the performance of separation of micro-TFFF but also by taking into account the practical requirements of the construction of the micro-TFFF channel. The principal finding is that very thin channel ( w = 0.025 mm) substantially reduces the range of particle sizes or polymer molar masses that can effectively be separated due to the mixed separation mechanism, steric exclusion being effective from smaller particle size. The found dependence of the resolution on the imposed experimental conditions including the channel width has allowed the elucidation of some peculiar results published in the literature, which were contradictory with regard to the known theoretical and experimental findings.
DOI : 10.1016/s0021-9673(04)01028-3
Anahtar Kelimeler : Channel width, Retention mechanisms, Micro-thermal field-flow fractionation, Colloidal particles
ISSN: 0021-9673
Sayı: 1-2
Cilt: 1046
Sayfa: 167-173
Sınıflandırma :
Çevre %28
10
Manganese speciation using capillary electrophoresis–ICP-mass spectrometry
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Bernhard Michalke
Yıl :
2004
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
Manganese is a trace element known to activate many enzymes involved in metabolic processes and it shows protective function against oxidative stress. On the other hand, increased Mn levels are known for damaging the central nervous system, resulting in motoric abnormalities and psychic disorder. Such additional Mn exposure can cause an “Mn overflow” in the liver, accompanied by production of specific (labile) Mn transporters (Mn-species). The speciation of these Mn-compounds is still unknown but they are believed targeting the brain. The aim of this paper was to develop a speciation method for manganese species in liver extracts, which allows to speciate the compounds quickly and with minimal risk of species alteration. Capillary electrophoresis (CE)–inductively coupled plasma mass spectrometry (ICP-MS) offers a valuable tool as analytes are not in contact to a stationary phase which probably affects species stability. Separation usually is fast and ICP-MS detection is element specific and sensitive. The paper describes the set-up and optimization of the hyphenated technique, optimization of separation according to pH and finally the Mn speciation of a liver extract. Several Mn species were found, such as arginase, Mn-transferrine, Mn-albumine and some more. The detection limit of the method was determined at 1.1 μg Mn/L independent on the species.
DOI : 10.1016/j.chroma.2004.05.076
Anahtar Kelimeler : Speciation analysis, Element-selective detection, Detection, CE, Inductively coupled plasma mass spectrometry, Manganese
ISSN: 0021-9673
Sayı: 1
Cilt: 1050
Sayfa: 69-76
Sınıflandırma :
11
Characterization of technical waxes comparison of chromatographic techniques and matrix-assisted laser-desorption/ionization mass spectrometry
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
G. Kühn , St. Weidner , U. Just , G. Hohner
Yıl :
1996
Journal of Chromatography A
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Kaydet Alıntıla
Technical waxes and paraffins were investigated using supercritical fluid chromatography (SFC), matrix-assisted laser-desorption/ionization mass spectrometry (MALDI-MS) and size-exclusion chromatography (SEC). SEC enables the simultaneous determination of molecular masses up to high values and molecular mass distributions. The resolution of homologous species, however, is poor. In this respect the use of SFC is advantageous. Proper resolution of homologues may be provided up to Mr∼1200 without great difficulty. To compare these chromatographic results MALDI-MS was applied for the determination of molecular masses and mass distributions in technical waxes for the first time. Using reflectron mode excellent MALDI mass spectra could be achieved in the molecular mass range up to 1000 Da. The mean values of the molecular masses calculated by MALDI-MS were in sufficient agreement with those of SFC. In the linear mode of MALDI-MS molecular masses could be determined to nearly 3000 Da. Beyond this mass range SEC still remains the method of choice. Advantages and diffulties of the used methods are discussed in this paper.
DOI : 10.1016/0021-9673(95)01255-9
Anahtar Kelimeler : Molecular mass determinations, Molecular mass distributions, Waxes, Paraffins
ISSN: 0021-9673
Sayı: 1
Cilt: 732
Sayfa: 111-117
Sınıflandırma :
Kimya %98
Kromatografi %100
12
Erratum to “A new liquid chromatography–tandem mass spectrometry method using atmospheric pressure photo ionization for the simultaneous determination of azaarenes and azaarones in Dutch river sediments” J. Chromatogr. A 1294 (2012) 33–40
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Jan Brulik , Zdenek Simek , Pim de Voogt
Yıl :
2013
Journal of Chromatography A
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Kaydet Alıntıla
DOI : 10.1016/j.chroma.2013.06.018
ISSN: 0021-9673
Cilt: 1302
Sayfa: 213-214
Sınıflandırma :
13
Comparison of two gas-liquid chromatographic methods for the determination of nitrazepam in plasma
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Lauri Kangas
Yıl :
1977
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
Nitrazepam in plasma was determined by gas-liquid chromatography with a nickel-63 electron-capture detector, unchanged by a direct method and also by a hydrolysis method. The extraction in the direct method was carried out with benzene-dichloromethane (90:10) and in the hydrolysis method with diethyl ether. The hydrolysis was performed with 6 N sulphuric acid. The hydrolysis product was extracted with toluene-n-heptane-ethyl acetate (80:20:5) directly from acid. Thus the commonly used change in pH was omitted. Nitrazepam concentrations in plasma were determined in 10 healthy volunteers after two oral doses (5 and 10 mg); 0.5 ml of plasma was used for each determination and clonazepam, methylbromazepam and methylnitrazepam were used as internal standards. The recoveries of the methods are almost quantitative (>96%). The two methods are clinically comparable. The high sensitivity and specificity make these methods useful in clinical determinations of nitrazepam in plasma. Advantages and disadvantages of both methods are discussed.
DOI : 10.1016/s0021-9673(00)86278-0
ISSN: 0021-9673
Sayı: 2
Cilt: 136
Sayfa: 259-270
Sınıflandırma :
14
Separation of ivermectin components by high-speed counter-current chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Hisao Oka , Yoshimoto Ikai , Junko Hayakawa , Ken-ichi Harada , Mokoto Suzuki , Atsuko Shimizu , Tomoko Hayashi , Kazue Takeba , Hiroyuki Nakazawa , Yoichiro Ito
Yıl :
1996
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
High-speed counter-current chromatography (HSCCC) has been successfully applied to the separation of the ivermectin components. A 25-mg quantity of the sample was separated using a two-phase solvent system of n-hexane-ethyl acetate-methanol-water (19:1:10:10, v/v). The fractions were analyzed by high-performance liquid chromatography, nuclear magnetic resonance, and fast-atom bombardment mass spectrometry. The separation yielded 18.7 mg of 99.9% pure ivermectin B1a, 1.0 mg of 96.0% pure ivermectin B1b, and 0.3 mg of 98.0% pure avermectin Bla (precursor of ivermectin).
DOI : 10.1016/0021-9673(95)00803-9
ISSN: 0021-9673
Sayı: 1
Cilt: 723
Sayfa: 61-68
Sınıflandırma :
15
Application of high-performance liquid chromatographic chiral stationary phases to pharmaceutical analysis
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Irving W. Wainer , Thomas D. Doyle
Yıl :
1983
Journal of Chromatography A
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Kaydet Alıntıla
A series of amide derivatives of the enantiomers of 1-phenyl-2-aminopropane (amphetamine) were resolved by high-performance liquid chromatography on a chiral stationary phase (CSP), (R)-N-(3,5-dinitrobenzoyl)phenylglycine, which is commercially available in ionically and covalently bonded columns. The separation factor ranged from 1.01 to 1.09 and was consistently larger when the compounds were chromatographed on the covalent column. Chromatographic parameters correlate in detail with a solute-CSP interaction model requiring up to four binding sites and a fifth repulsive interaction which is steric in origin and which provides the key chiral discriminant.
DOI : 10.1016/s0021-9673(01)88035-3
ISSN: 0021-9673
Cilt: 259
Sayfa: 465-472
Sınıflandırma :
Kimya %100
Kromatografi %100
16
Large-scale purification of the synthetic peptide fragment 163–171 of human interleukin-β by multi-dimensional displacement chromatogaphy
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
G.C. Viscomi , C. Cardinali , M.G. Longobardi , A.S. Verdini
Yıl :
1991
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
Multi-dimensional chromatography has been used successfully in the displacement mode for the purification of the synthetic peptide HValGlnGlyGluGluSerAsnAspLysOH, the fragment 163-171 of human interleukin-β. This peptide can mimic several of the in vivo and in vitro immunostimulatory activities of the entire protein, except for the inflammatory effect. A large-scale procedure has been developed to purify the synthetic peptide by reversed-phase (RP) and ion-exchange (IE) displacement chromatography (DC) in a single run without any pretreatment. Masses from 100 mg to about 35 g of the unpurified compounds synthesized by a solid-phase technique on a Merrifield-type resin and obtained by acidolytic cleavage from the solid support, can be purified in this way. In the RP-DC mode the carrier and the displacer were aqueous solutions of 0.1% trifluoroacetic acid and 50 mM benzyltributylammonium chloride, respectively, whereas in the IE-DC mode the carrier was water and the displacer 50 mM ammonium citrate solution. RP-DC and IE-DC were also performed in series by directing the effluent of the RP column onto the IE column. Peptide purities and recoveries greater than 96 and 90%, respectively, were obtained.
DOI : 10.1016/s0021-9673(00)91428-6
ISSN: 0021-9673
Cilt: 549
Sayfa: 175-184
Sınıflandırma :
17
Fast method development of rooibos tea phenolics using a variable column length strategy
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Deirdre Cabooter , Ken Broeckhoven , Kathithileni M. Kalili , André de Villiers , Gert Desmet
Yıl :
2011
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
The development of a method for the separation of standard compounds of the 15 main phenolics found in rooibos tea is presented. The separation of these compounds in a single HPLC analysis is particularly challenging due to the similarity of rooibos phenolics. As a result, multiple methods are often required to analyze all major phenolics in rooibos tea samples. The method development process is significantly enhanced in this study by using the recently introduced automated column coupler in combination with the variable column length strategy. This strategy consists of performing the initial scouting runs, wherein the best separation conditions are determined, on a short column and subsequently fine-tuning the separation on longer columns to benefit from their higher separation performance. It is demonstrated that the method development process can further be expedited by operating each column length at the maximum pressure, in this case 1000 bar. Although this holds in general, it is even more the case for the presently considered sample, since the selectivity of the sample is more pressure- than temperature-dependent. Applying the optimized method to unfermented and fermented aqueous rooibos tea extracts in combination with Q-TOF mass spectrometry, some 30 phenolic compounds are tentatively identified.
DOI : 10.1016/j.chroma.2011.08.069
Anahtar Kelimeler : Method development, Automated column coupler, Phenolics, Rooibos tea, Ultra-high pressure
ISSN: 0021-9673
Sayı: 41
Cilt: 1218
Sayfa: 7347-7357
Sınıflandırma :
Kimya %100
Kromatografi %99
18
Liquid column chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yıl :
2001
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
DOI : 10.1016/s0021-9673(01)99522-6
ISSN: 0021-9673
Sayı: 2
Cilt: 941
Sayfa: B501-B508
Sınıflandırma :
Kimya %98
Kromatografi %100
19
Influence of experimental conditions upon polarity parameters as measured by gas chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Adam Voelkel
Yıl :
1988
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
The influence of different chromatographic experimental parameters upon empirical, thermodynamic and dispersive force polarity parameters is examined for unusual stationary phases. The parameters considered were found to be sensitive to the column temperature, solute sample size and stationary phase loading.
DOI : 10.1016/s0021-9673(01)82056-2
ISSN: 0021-9673
Cilt: 457
Sayfa: 73-84
Sınıflandırma :
20
Capillary electrochromatography: operating characteristics and enantiomeric separations
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Frédéric Lelièvre , Chao Yan , Richard N. Zare , P. Gareil
Yıl :
1996
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
Some fundamental aspects of capillary electrochromatography (CEC) (electroosmotic flow, capacity factor, plate height) were studied by carrying out the separation of some neutral compounds with capillaries packed with octadecylsilica particles (ODS). No loss of efficiency up to a linear electroosmotic velocity of 1.3 mm/s was observed for retained analytes (capacity factors varying from 0.7 to 2.5). The extra-column dispersions caused by the frit and the unpacked section separating the frit from the detection window were estimated. Chiral separations of the neutral enantiomers of chlorthalidone by packed capillary electrochromatography was successfully achieved using two approaches: (a) use of the chiral agent, hydroxypropyl-β-cyclodextrin (HPβCD) directly in the mobile phase with an achiral stationary phase (3 μm ODS); (b) use of a chiral stationary phase (5 μm HPβCD-bonded silica particles) with an achiral mobile phase. As with liquid chromatography, the second method achieves higher selectivity and resolution in a shorter analysis time.
DOI : 10.1016/0021-9673(95)00832-2
Anahtar Kelimeler : Capillary electrochromatography, Enantiomer separation
ISSN: 0021-9673
Sayı: 1
Cilt: 723
Sayfa: 145-156
Sınıflandırma :
Kimya %100
Kromatografi %99
21
Use of equivalent chain lengths for the characterization of fatty acid methyl esters separated by linear temperature-programmed gas chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
J. Krupčik , P. Bohov
Yıl :
1985
Journal of Chromatography A
Yayıncı Web Sitesi
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Kaydet Alıntıla
C12C26 fatty acid methyl esters (FAMEs) were separated by glass capillary gas chromatography on SP 2340 as stationary phase, both isothermally in the temperature range 150–220°C and using linear temperature-programmed capillary gas chromatography (LTPCGC) with gradients of 0.5–3.5°C/min. The dependences of the equivalent chain lengths on temperature are linear. An equation as well as a graphic procedure are derived for the prediction of the retention temperatures of FAMEs separated by LTPCGC on SP 2340. Good agreement between predicted and experimental retention temperatures was found.
DOI : 10.1016/s0021-9673(00)90491-6
ISSN: 0021-9673
Cilt: 346
Sayfa: 33-42
Sınıflandırma :
Kimya %100
Kromatografi %98
22
Liquid chromatographic separation of enantiomeric alkanolamines via diastereomeric tartaric acid monoesters
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
W. Lindner , Ch. Leitner , G. Uray
Yıl :
1984
Journal of Chromatography A
Yayıncı Web Sitesi
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A new resolution method for the analytical and preparative separation of enantiomeric alkanolamines into their antipodes is presented. It involves formation of the monoesters of the alkanolamines with optically pure and symmetrically O,O- disubstituted (R,R)- or (S,S)-tartaric acids. The derivatization reactions are carried out in aprotic media by reaction with the tartaric acid anhydrides. The amine functions are ionically blocked via ion-pair formation with strong acids, e.g. trichloro-acetic acid. The resulting diastereomeric monoesters are easily separable into their antipodes by reversed-phase liquid chromatographic technique. Relative retention factors,α, up to 4 can be obtained, depending on the structural parameters of the alkanolamines and reagents, as well as on the mobile phase conditions (pH). The monoesters are zwitterions, possibly capable of forming intramolecular ion pairs via a ring structure favoured for ethanolamines.
DOI : 10.1016/s0021-9673(00)96186-7
ISSN: 0021-9673
Cilt: 316
Sayfa: 605-616
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Kimya %100
Kromatografi %100
23
Quantitation of polyamines using thin-layer chromatography and image analysis
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Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Scott H. Wettlaufer , Leonard H. Weinstein
Yıl :
1988
Journal of Chromatography A
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Efficient separation of dansylated polyamines can be achieved by thin-layer chromatography (TLC). Quantitation, however, can be laborious because it requires removal of the silica gel and the fluorescing derivative from the glass plates, elution in a suitable solvent, and estimation with a fluorescence spectrophotometer. We report here a relatively simple and rapid method for the quantitation of dansylated polyamines that employs an image analyzer without removal from the glass TLC plates.
DOI : 10.1016/s0021-9673(01)83879-6
ISSN: 0021-9673
Sayı: 2
Cilt: 441
Sayfa: 361-366
Sınıflandırma :
Kimya %98
Kromatografi %100
24
Determination of piribedil in biological materials by gas—liquid chromatography—mass fragmentography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
R. Fanelli , A. Frigerio
Yıl :
1974
Journal of Chromatography A
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A sensitive and specific method for the quantitative determination of piribedil in brain tissue and plasma is described. After extraction, piribedil is detected by gas—liquid chromatography using a flame ionization detector or the mass fragmentographic technique, and these two procedures allow 250 and 10 ng/ml or ng/g, respectively, of piribedil present in biological samples to be determined.
DOI : 10.1016/s0021-9673(01)85409-1
ISSN: 0021-9673
Sayı: 2
Cilt: 93
Sayfa: 441-446
Sınıflandırma :
25
A gas chromatographic method for measuring 6-mercaptopurine in serum
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
D.G. Bailey , T.W. Wilson , G.E. Johnson
Yıl :
1975
Journal of Chromatography A
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A method is presented for the measurement of 6-mercaptopurine (6-MP) in serum. Serum samples containing the drug were treated with dithioerythritol and saturated with ammonium carbonate. 6-MP was then extracted from the serum with a mixture of isopropanol-ethyl acetate (1:1, v/v) containing 0.1% ethanethiol. The solvent was evaporated, the residue dissolved in dilute hydrochloric acid, washed with chloroform, and extracted with ethyl acetate. 6-MP was derivatized with trimethylanilinium hydroxide and measured gas chromatographically. The sulfhydryl-protecting reagents, dithioerythritol and ethanethiol, were added to prevent the decomposition of 6-MP. The extraction and clean-up method recovered 78 ± 2% (S.E.) of the 6-MP present. Tracer amounts of [8-14C]-6-MP served as the internal standard during the extraction part of the method. Theophylline was used as the internal standard during the gas chromatographic analysis. The standard curve obtained from the gas chromatograph was linear between 0.5 and 20 μg/ml of 6-MP. Serum samples were stored in the freezer for two weeks without significant loss of drug. No interference was encountered from normal serum constituents or xanthines, such as caffeine or theophylline added to serum.
DOI : 10.1016/s0021-9673(00)99279-3
ISSN: 0021-9673
Sayı: 2
Cilt: 111
Sayfa: 305-311
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Kimya %97
Kromatografi %100
26
Influence of different types of cyclodextrins on the racemization of scopolamine-N-butylbromide
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Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Antje Bunke , Thomas Jira , Thorsten Beyrich
Yıl :
1996
Journal of Chromatography A
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Kaydet Alıntıla
The influence of cyclodextrins (CDs) on the racemization and hydrolysis of scopolamine-N-butylbromide was determined kinetically. α-CD and γ-CD enhance the racemization rate of the substance. β-CD shows no effect and DM-β-CD (dimethyl-β-CD) causes inhibition of racemization. The hydrolysis of the substance was retarded by β-, γ- and DM-β-CD. In the presence of α-CD no change in hydrolysis rate was observed.
DOI : 10.1016/0021-9673(95)01060-2
Anahtar Kelimeler : Racemization, Mobile-phase composition, Enantiomer separation, Cyclodextrins, Scopolamine-N-butylbromide, Tropic acid
ISSN: 0021-9673
Sayı: 1-2
Cilt: 728
Sayfa: 441-445
Sınıflandırma :
Kimya %100
Kromatografi %99
27
Micro-column high-performance liquid chromatography and flame-based detection principles
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
V.L. McGuffin , M. Novotný
Yıl :
1981
Journal of Chromatography A
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Kaydet Alıntıla
Novel detectors are described for micro-column high-performance liquid chromatography; they are based on the well-known principles of flame photometric and thermionic detection. These devices exhibit good selectivity and sensitivity for organophosphorus compounds in both aqueous and selected organic solvents. The extremely small volume of these flame-based detectors and their enhanced response at low flow-rates make them particularly attractive for capillary-column high-performance liquid chromatography.
DOI : 10.1016/s0021-9673(00)82054-3
ISSN: 0021-9673
Cilt: 218
Sayfa: 179-187
Sınıflandırma :
28
Preparative separation of enantiomers by flash chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
William H. Pirkle , Athanasios Tsipouras , Thomas J. Sowin
Yıl :
1985
Journal of Chromatography A
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Kaydet Alıntıla
DOI : 10.1016/s0021-9673(01)90577-1
ISSN: 0021-9673
Cilt: 319
Sayfa: 392-395
Sınıflandırma :
Kimya %100
Kromatografi %100
29
New derivatization reagents for the resolution of amino acid enantiomers by high-performance liquid chromatography
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Chromatography A
Yayıncı:
Elsevier
Yazar(lar) :
Junichi Goto , Masatoshi Hasegawa , Setsuko Nakamura , Kazutake Shimada , Toshio Nambara
Yıl :
1978
Journal of Chromatography A
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Kaydet Alıntıla
A new derivatization procedure has been developed for converting enantiomeric amines into diastereomers for resolution by high-performance liquid chromatography. Two chiral reagents, (−)-a-methoxy-a-methyl-1-naphthaleneacetic acid and (−)-a-methoxy-a-methyl-2-naphthaleneacetic acid, were prepared and optically resolved by fractional crystallization of their (+)-a-methylbenzylamine salts. The diastereomeric amides formed from amino acid methyl esters and (−)-a-methoxy-a-mthyl-1-naphthaleneacetic acid by the N,N′-dicyclohexylcarbodiimide method were efficiently resolved on a normal-phase column and responded with satisfactory sensitivity in the ultraviolet detector.
DOI : 10.1016/s0021-9673(00)85077-3
ISSN: 0021-9673
Sayı: 2
Cilt: 152
Sayfa: 413-419
Sınıflandırma :
Kimya %100
Kromatografi %100

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