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PubMed2000

Colour pigments of Trichoderma harzianum. Preliminary investigations with thin-layer chromatography-Fourier transform infrared spectroscopy and high-performance liquid chromatography with diode array and mass spectrometric detection.

The colour pigments of Trichoderma harzianum fermentation broth were separated and the main fractions were tentatively identified by reversed-phase thin-layer chromatography-Fourier transform infrared spectroscopy (RP-TLC-FT-IR), RP-HPLC-diode array detection and RP-HPLC-MS. It was established that the multistep gradient elution developed for RP-TLC separation of pigments can be successfully used as a pilot method for the rational design of gradient elution in RP-HPLC for the separation of the same pigments. FT-IR and MS measurements were unable to identify the exact chemical structures of the main pigment fractions, the presence of OH, =CH and C=O (RP-TLC-FT-IR) and OH and NH, substructures (RP-HPLC-MS) was confirmed. It was assumed that the main pigment fractions are oxidation polymers originating from monomer molecules containing polar substructures and double bonds in the alkyl chain which are liable for oxidation during the aerobic fermentation process.

Chromatography, High Pressure Liquid↗
PubMed2000

Comparison of comprehensive two-dimensional gas chromatography and gas chromatography--mass spectrometry for the characterization of complex hydrocarbon mixtures.

In this paper, we compare the current separation power of comprehensive two-dimensional gas chromatography (GCxGC) with the potential separation power of GC-mass spectrometry (GC-MS) systems. Using simulated data, we may envisage a GC-MS contour plot, that can be compared with a GCxGC chromatogram. Real examples are used to demonstrate the current potential of the two techniques in the field of hydrocarbon analysis. As a separation technique for complex hydrocarbon mixtures, GCxGC is currently about as powerful as GC-MS is potentially powerful. GC-MS has not reached its potential separation power in this area, because a universal, soft ionization method does not exist. The greatest advantage of GCxGC is, however, its potential for quantitative analysis. Because flame-ionisation detection can be used, quantitative analysis by GCxGC is much more robust, reliable and reproducible.

Chromatography, Gas↗
PubMed2001

Automated normal-phase preparative high-performance liquid chromatography as a substitute for flash chromatography in the synthetic research laboratory.

An automated normal-phase preparative HPLC system was developed in order to omit time-consuming flash column chromatography in the synthetic research laboratory. The system is equipped with steel columns packed with spherical 12 microm silica and is able to separate samples in a range of 0.1-10 g depending on the column diameter and chromatographic problem. It was designed to be used as an open access instrument in the research department. The general users select from binary gradient programs after running an analytical TLC with the raw product. The HPLC instrument was fully controlled by the Chromeleon software from Dionex. A Gilson 215 robot served as injector/collector.

Automation↗
PubMed1976

Gas-liquid chromatography of nucleosides. Derivatization and chromatography.

The aims of this investigation were to establish the optimum reaction conditions for silylation of nucleotides with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and to investigate the chromatographic properties of the following nucleosides: adenosine, guanosine, cytidine, thymine, inosine, xanthosine, and uridine. Closed tube silylations were performed with a 1000 molar excess of BSTFA at 25, 75, 120, 150, and 175 degrees for 15, 30, 60, 120 and 240 min. The optimal time and temperature for derivatization were found to be 150 degrees and 15 min. Using these reaction conditions, samples were then silylated with 50, 100, 200, 500, and 1000 molar excess of BSTFA; a molar excess of 225 was best. The stability of the nucleoside derivatives on standing at room temperature for 1-7 days was investigated. Quantitative gas-liquid chromatography of trimethylsilyl (TMS) nucleosides can be performed if samples are analyzed within 48 h, after which time the relative weight response for the nucleosides decreased somewhat. Chromatographic column studies were made using various liquid phases and supports. With methylsiloxanes as the liquid phase, Supelcoport as support was found to be superior. Resolution of TMS guanosine from TMS cytidine was attempted at different column lengths using 3% (w/w) SE-30 on Supelcoport, different loadings (%, w/w) of SE-30 on Supelcoport, and different polarity liquid phases, 4% (w/w) OV-11 or 3% (w/w) OV-17 or 4% (w/w) Dexsil-300 on Supelcoport. A complete separation of the six ribonucleosides including guanosine and cytidine was obtained with 1 m x 4 mm I.D. glass columns of 4% (w/w) OV-11 and 3% (w/w) OV-17 on 100-120 mesh Supelcoport. It was observed that with 2'-deoxycytidine, one obtains the TMS cytosine peak (retention temperature 150 degrees) plus another peak with a retention temperature of 120 degrees, under all derivatization conditions with BSTFA and bis(trimethylsilyl)-acetamide. Similar formation of bases from other 2'-deoxyribonucleosides occurred when the molar excess of BSTFA was greater than 500. The minimal detectable amounts obtained for all the nucleosides ranged from 5 to 10 ng injected with a signal-to-noise ratio of 3. The relative standard deviations for all nucleosides and deoxynucleosides ranged from 1.2 to 4.8% on different methylsiloxanes on Supelcoport columns.

Adenosine↗
PubMed1976

A comparison of the determination of partition coeficients of 1,4-benzodiazephines by high-performance liquid chromatography and thin-layer chromatography.

Relative partition coefficients (P) of 1,4-benzodiazepines were determined by a reversed-phase thin-layer chromatographic (RP-TLC) technique in the systemoleyl alcohol-water, and by high-performance liquid chromatography (HPLC) using several column packing materials. RMw values, obtained by RP-TLC, correlated well with log P values determined directly in the system oleyl alcohol-water and with the literature values for the system 1-octanol-water. Th log k' w values from the HPLC experiments could be determined with greater precision, but the correlations of log k'w with log Poleyl alcohol and log Poctanol were not as good as those found for the Rmw values.

Benzodiazepines↗
PubMed1989

Determination of gallamine and its impurities by reversed-phase ion-pair high-performance liquid chromatography and comparison with thin-layer chromatography.

A reversed-phase, ion-pair high-performance liquid chromatographic (HPLC) method for the determination of gallamine and its impurities is described. The separation is achieved on a Nucleosil C18 column with acetonitrile-aqueous phosphate buffer (pH 3.0) (31:69, v/v) containing 0.1 M sodium perchlorate as eluent and on-line UV detection at 200 nm. The method is sensitive (the detection limit is 0.7 ng injected) and reproducible, with a peak area coefficient of variation of 0.19% (n = 15; 3 micrograms injected) and 1.65% (n = 15; 10 ng injected) for a gallamine assay; the detector response is linear over the concentration range 0.5-250 micrograms/ml of gallamine triethiodide with a correlation coefficient of 0.9997. The method has been used to isolate the two main impurities contained in gallamine triethiodide batches; their structures have been determined by NMR and fast atom bombardment mass spectrometry. Various gallamine triethiodide batches have been analysed and the HPLC results compared with those obtained by thin-layer chromatography.

Chromatography, High Pressure Liquid↗
PubMed1978

Extraction and liquid-solid chromatography cleanup procedures for the direct analysis of four pyrethroid insecticides in crops by gas--liquid chromatography.

The extraction of four pyrethroid insecticides, fenpropanate (WL 41706, S-3206), permethrin (WL 43479, FMC-33297, PP 557, NRDC-143), cypermethrin (WL 43467, NRDC 149), and fenvalerate (WL 43775, S-5602) from carrots, tomatoes celery, and onions with acetone followed by extraction of the resulting acetone--water mixture with hexane, was investigated and found suitable for residue analysis. The elution of the four materials from two types of silica and alumina absorbents with mixtures of organic solvents of varying polarity was examined. The elution patterns and recoveries from silica gel, aluminum oxide, and water deactivated Florisil indicated potential utility in cleanup. Florisil was found to provide cleanup for asparagus, carrots, tomatoes, tobacco, and onions permitting analyses to less than 0.01 ppm for most of the insecticides by electron capture gas--liquid chromatography, at extract concentrations of 1 g/ml. The other adsorbents, singly or in combination, were found to provide the cleanup required for radishes and those cases involving other crops where Florisil cleanup was insufficient.

Chromatography, Gas↗
PubMed2002

Determination of linear alkylbenzenes in fish tissue by gel permeation chromatography and gas chromatography-mass spectrometry.

A gel permeation chromatographic (GPC) procedure is described for separation of the long-chain linear alkylbenzenes (LABs) from fish muscle tissues. This technique was found to remove the matrix interference significantly and thereby improve the sensitivity of detection of LABs in the extracts. Gas chromatography-mass spectrometry (GC-MS) was then used to quantitate LABs in different species of fish and also fish from different locations on a transect from the outfalls from the Orange County Sanitation Districts, in the coastal waters of Southern California. The results are consistent with the proximity of the (sewage) source. The data, thus, show that LAB contents in fish tissues, especially that from white croaker (Genyonemus lineatus) are useful in assessing exposure to sewage residues in the marine waters. This method of concentrating LABs by GPC could be applicable to all other similar biological matrices.

Animals↗
PubMed1988

High-performance liquid chromatography of proteins on compressed, non-porous agarose beads. II. Anion-exchange chromatography.

Macroporous agarose beads were rendered impermeable to proteins by shrinkage and cross-linking in organic solvents. The chromatographic properties of compressed beds of these non-porous beads derivatized for high-performance ion-exchange chromatography were studied, e.g., the resolution as a function of gradient time, flow-rate (at constant gradient volume) and loading capacity. The columns permit high flow-rates and the resolution is about the same at low and high flow-rates. The beads are stable up to pH 14.

Animals↗
PubMed1976

Analysis of benzoylecgonine in urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

Benzoylecgonine, a polar metabolite of cocaine, was extracted and purified from urine using a reversed-phase high-performance liquid chromatographic column. The portion of the eluent corresponding to elution of the drug was collected, derivatized, and quantified using gas chromatography-mass spectrometry with selected ion monitoring. Using this procedure, analysis of 1 ng/ml of benzoylecgonine in urine can be achieved.

Chromatography, Gas↗
PubMed1990

High-performance liquid chromatography of amino acids, peptides and proteins. XCVIII. The influence of different displacer salts on the bandwidth properties of proteins separated by gradient elution anion-exchange chromatography.

The influence of eight different displacer salts on the bandwidth properties of four globular proteins separated by a high-performance anion-exchange chromatography has been investigated. Proteins were eluted under gradient conditions with a range of alkali metal halide salts, in which the anion and cation were varied in the series F-, Cl- and Br- and Li+, Na+ and K+, respectively. The experimentally observed bandwidths (sigma v,exp) were found to deviate significantly from peak widths (sigma v,calc) predicted on the basis of plate theory for small molecules. For data accumulated under conditions of varied gradient time and constant flow-rate the solute bandwidth ratios (sigma v,exp/sigma v,calc) increased in the order Br- less than Cl- less than F- at low values of the gradient steepness parameter, b, or increasing column residence times. In addition, systematic changes in the cation influenced the bandwidth ratios (sigma v,exp/sigma v,calc) in the order K+ less than Na+ less than Li+. Significant deviations between predicted and observed bandwidth values were also observed under elution conditions of constant gradient time and varied flow-rate. The results of the present study further demonstrate the complex nature of the interaction between protein solutes and coulombic chromatographic surfaces.

Anions↗
PubMed1990

High-performance liquid chromatography of amino acids, peptides and proteins. XCIX. Comparative study of the equilibrium refolding of bovine, porcine and human growth hormone by size-exclusion chromatography.

The equilibrium refolding of bovine, porcine and human growth hormone and ovine prolactin in guanidine hydrochloride has been investigated using high-performance size-exclusion chromatography (HPSEC). It was found that bovine and porcine growth hormones exhibited very similar refolding behaviour. However, the renaturation of human growth hormone followed a different pathway. In particular, the folding transition of human growth hormone occurred at 4.7 M guanidine hydrochloride compared to 3.8 and 3.5 M for the bovine and porcine molecules, respectively, and 3.5 M for ovine prolactin. The refolding mechanism of an internally clipped fragment derived from partial tryptic digestion, exhibited similar folding properties to the corresponding intact molecule. The internally clipped analogue existed as a relatively larger molecule under fully denaturing conditions. Reduction followed by carboxymethylation resulted in growth hormone molecules with significantly reduced stability and altered folding properties. The results have been correlated with differences in structure to further demonstrate the utility of HPSEC in the study of protein folding and stability.

Alkylation↗
PubMed1984

Analysis of phospholipids in cow's milk by high-temperature injection gas chromatography and high-performance liquid chromatography.

An investigation of the high-temperature injection (350 degrees C) gas chromatographic behaviour of standards of various classes of phospholipids has elucidated certain characteristic fragments ("tracers") in the pyrogram of each class. Under these conditions of pyrolysis of the phospholipids, a natural mixture of such substances (extracted and purified from cows' milk) has provided evidence for the same "tracers" as for the standards. Analogous results were obtained with a more representative specimen of cows' milk of various breeds grown in areas of different altitudes. The content of fatty acids in phospholipids, tested on each class (separated by means of radial compression high-performance liquid chromatography from polar lipids of milk) appeared to be relatively similar for all the phospholipid classes, and over half the content consisted of unsaturated fatty acids. The major component was delta 9-octadecenoid (oleic) acid.

Animals↗
PubMed1984

Comparison of the analysis of delta 9-tetrahydrocannabinol capsules by high-performance liquid chromatography and capillary gas chromatography.

The modification of a high-performance liquid chromatography (HPLC) system and the development of a capillary gas-chromatographic (GC) system for the analysis of delta 9-tetrahydrocannabinol, encapsulated in soft gelatin capsules, are described. A photodiode array detector was used to evaluate peak homogeneity after each HPLC system modification. Sesame oil was separated from the extract by Sep-Pak filtration prior to GC analysis. Quantitation by both systems had r values greater than 0.999 and R.S.D. values less than 1.0%. Simultaneous capsule assays by both methods agreed within 1%.

Capsules↗
PubMed1989

High-performance liquid chromatography of amino acids, peptides and proteins. LXXXIX. The influence of different displacer salts on the retention properties of proteins separated by gradient anion-exchange chromatography.

The influence of eight different displacer salts on the retention properties of four globular proteins, ranging in molecular weight from 14,000 to 43,000, was investigated by using the Mono-Q strong-anion-exchange resin as the stationary phase. Proteins were eluted under gradient conditions with a range of alkali metal halides to vary systematically the anion and cation species in the series F-, Cl-, and Br- and Li+, Na+ and K+. Protein Zc values (i.e. slopes of the ion-exchange retention plots, derived from the dependency of the logarithmic capacity factor log k' on the concentration of the ionic displacer) generally increased when both the anion and cation were either chaotropic, e.g. KBr, or kosmotropic, e.g. NaF, in nature. Conversely, Zc values decreased when the displacer salt contained an anion-cation combination of a chaotropic and a kosmotropic ion, e.g. KF. These results indicate that the lyotropic properties of salts are additive in their effect on the interactive properties of proteins in anion-exchange chromatography. The Zc values were also found to depend on the manner in which the ionic strength was manipulated to affect elution, i.e. isocratic or gradient change in concentration of the displacing salt. Thus, isocratic experiments and gradient experiments with varied gradient time or varied flow-rate were observed to result in log k' versus log l/c dependencies with non-coincident Zc values. The relationship between protein Zc values, the electrostatic contact area or ionotope, Ac, and the electrostatic potential of the protein surface psis, is discussed.

Amino Acids↗
PubMed1989

Separation of major phospholipid classes by high-performance liquid chromatography and subsequent analysis of phospholipid-bound fatty acids using gas chromatography.

A sensitive high-performance liquid chromatographic method for the separation of major phospholipid (PL) classes in biological materials is described. Using this method it was easy to separate P-cholin, P-ethanolamine, P-serine, P-inositol, cardiolipin, sphingomyelin, lyso-P-choline and lyso-P-ethanolamine from skeletal and cardiac muscle samples. The method is based on the simultaneous use of a pH gradient and a polarity gradient. This procedure can easily be modified to optimize the separation of PLs from very different tissues. Subsequent analysis of the PL-bound fatty acids (FAs) by gas chromatography resulted in a well separated FA pattern. Following this FA separation it was possible to recalculate the specific PL content in the original sample.

Animals↗
PubMed2002

Determination of pesticide residues in coconut water by liquid-liquid extraction and gas chromatography with electron-capture plus thermionic specific detection and solid-phase extraction and high-performance liquid chromatography with ultraviolet detection.

Two simple methods were developed to determine 11 pesticides in coconut water, a natural isotonic drink rich in salts, sugars and vitamins consumed by the people and athletes. The first procedure involves solid-phase extraction using Sep-Pak Vac C18 disposable cartridges with methanol for elution. Isocratic analysis was carried out by means of high-performance liquid chromatography with ultraviolet detection at 254 nm to analyse captan, chlorothalonil, carbendazim, lufenuron and diafenthiuron. The other procedure is based on liquid-liquid extraction with hexane-dichloromethane (1:1, v/v), followed by gas chromatographic analysis with effluent splitting to electron-capture detection for determination of endosulfan, captan, tetradifon and trichlorfon and thermionic specific detection for determination of malathion, parathion-methyl and monocrotophos. The methods were validated with fortified samples at different concentration levels (0.01-12.0 mg/kg). Average recoveries ranged from 75 to 104% with relative standard deviations between 1.4 and 11.5%. Each recovery analysis was repeated at least five times. Limits of detection ranged from 0.002 to 2.0 mg/kg. The analytical procedures were applied to 15 samples and no detectable amounts of the pesticides were found in any samples under the conditions described.

Chromatography, Gas↗
PubMed2002

Characterisation of lavender essential oils by using gas chromatography-mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography.

Nine samples of lavender essential oil were analysed by GC-MS using low-polarity and polar capillary columns. Linear retention indices (LRI) were calculated for each component detected. Characterisation of the individual components making up the oils was performed with the use of an mass spectrometry (MS) library developed in-house. The MS library was designed to incorporate the chromatographic data in the form of linear retention indices. The MS search routine used linear retention indices as a post-search filter and identification of the "unknowns" was made more reliable as this approach provided two independent parameters on which the identification was based. Around 70% of the total number of components in each sample were reliably characterised. A total of 85 components were identified. Semi-quantitative analysis of the same nine samples was performed by gas chromatography (GC) with flame ionisation detection (FID). The identified components accounted for more than 95% of each oil. By comparing the GC-MS results with the results from the GCxGC-FID analysis of a lavender essential oil, many more components could be found within the two-dimensional separation space.

Chromatography, Gas↗