bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative yields of underivatized peptides by HPLC
Authors: Hollaway W. L. , Bhown A. S. , Mole J. E. , Bennett J. C. 
Published: May 2005

AbstractNew methods for peptide separation are being developed. Resolution of peptide mixtures on HPLC with good reproducibility indicates the progress that has already been made in development of supports with useful separation capabilities. At present adsorptive characteristics of the stationary phases may place limitations on the applicability of the technique to underivatized peptides. Hopefully, the application of ionpairing techniques and the development of new support materials will expand the range of application for protein and peptide purification.
On‐line hydrogenation of fatty acid methyl esters in capillary gas chromatography
Authors: Kuzmenko T. E. , Samusenko A. L. , Uralets V. P. , Golovnya R. V. 
Published: May 2005

AbstractAn injection splitter in front of a glass capillary column was used for the hydrogenation of fatty acid methyl esters (FAME) mixtures. Hydrogenation followed by gas chromatographic analysis on capillary columns permitted detection and identification in complicated natural mixtures of branched fatty acids, showing minor structural differences, in quantities down to 10−8g.The technique described, apart from its suitability for FAME analysis, shows promise for structure determination studies of other classes of compounds.
Thin‐layer gel chromatography of 8‐hydroxyquinoline metal complexes
Authors: Shibukawa M. , Oguma K. , Kuroda R. 
Published: May 2005

AbstractGel chromatographic behavior of 8‐hydroxyquinoline (oxine, abbreviated HOx) complexes of zinc, copper, aluminum, gallium and indium has been investigated on thin layers of Styragel 60A and Merckogel OR‐PVA 2000 mostly in chloroform and p‐dioxan media. Except for the stable Cu(Ox)2, the other oxinates exhibit either hydration or decomposition in gel‐solvent‐solute systems, which leads to strong retention or tailing on gel layers. An excess of 8‐hydroxyquinoline present in solvents allows the oxinates to be stabilized, so that well‐defined compact spots come out and migrate. For the Zn(Ox)2 the formation of a self‐adduct is strongly suggested on the basis of gel chromatographic behavior. Elution with the solvent containing pyridine also yields evidence of the adduct formation of zinc oxinate‐nitrogen base.
Thin‐layer adsorption chromatography with mixed mobile phases. 1. Characterization of chromatographic systems showing energetic heterogeneity of adsorbent surfaces with regard to admolecules of solvents and solutes
Authors: Różyło J. K. , Jaroniec J. A. , Kołodziejczyk H. , Jaroniec M. 
Published: May 2005

AbstractThin‐layer adsorption chromatography with a multicomponent mobile phase is discussed. A new equation for predicting RM‐values in TLC with mixed mobile phases using the RM‐ValUeS obtained for pure solvents is proposed. This equation takes into account effects of energetic heterogeneity of the adsorbent surface with regard to adsorbed molecules of solvents and solutes. Experimental verification of this equation is presented for RM‐data obtained by TLC using a binary mobile phase.
Preconcentration of samples in sandwich tanks for continuous thin‐layer chromatography
Authors: Soczewiński E. , Matysik G. 
Published: May 2005

AbstractIt is demonstrated that horizontai sandwich tank with two cover plates can be used to preconcentrate sample solutions. Narrow sharply‐defined starting zones are obtained just outside the smaller cover plate when the series of spots of the sample solution are applied on the thin layer and predeveloped with a volatile solvent. After evaporation of the solvent, the whole area of the TLC‐plate is covered with two plates and developed with a suitable solvent.
Optimum gas chromatographic conditions in wall‐coated capillary columns. Extended and simplified forms of the Golay‐equation
Authors: Cramers C. A. , Wijnheymer F. A. , Rijks J. A. 
Published: May 2005

AbstractBand broadening in capillary columns is satisfactorily described by the Golay‐equation extended to situations of appreciable pressure drop by Giddings. In practice, however, several simplifications are often made. The effect of these simplifications on the calculated values of the minimum plate height and optimum carrier gas velocity are treated systematically.
Advances in two‐dimensional GC with glass capillary columns
Authors: Anderson E. L. , Thomason M. M. , Mayfield H. T. , Bertsch W. 
Published: May 2005

AbstractA versatile two‐dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off‐line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra‐column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown.
A problem in etching Pyrex glass capillary columns
Authors: Clarke J. F. Gates 
Published: May 2005

AbstractRecent attempts to reproduce a literature method for etching of Pyrex glass capillary columns with „etching ether”︁ resulted in reduction of the columns to dust through a violent explosion. Although modifications of the method produced etched columns, we found that less than satisfactory results were achieved. Introduction of etching ether by simply coating the column with a thin film of the ether produced an evenly etched column with well defined whiskers. Several observations made during the etching process will also be discussed.
Polarity change in capillary GC by serial‐column temperature optimization (SECAT mode in capillary GC)
Authors: Kaiser R. E. , Rieder R. I. 
Published: May 2005

AbstractGC, including capillary GC, is rather inflexible, if a certain column length and stationary phase has been fixed for a given analytical problem. If the sample composition changes, one often has to change the column length and/or stationary phase, at least when something like optimum analytical conditions are needed. Temperature changes (or heating rates) can change the selectivity of a given column only within very limited ranges, due to the exponential effect of temperature on retention time. By serial coupling two chemically different capillaries, each run at another temperature, even the slightest changes of these two temperature values have a dramatic effect on the selectivity of the system for polar substances. We call this technique the SECAT mode of GC. Results are reported as retention index shifts, dependent on SECAT temperature data. This technique can in future easily be automated, thus enabling the analyst, for polar sample analysis, to adjust a given chroma‐tographic system to his specific sample composition without touching the instrument.
Multiple short pass glass capillary gas chromatography
Authors: Jennings W. , Settlage J. A. , Miller R. J. 
Published: May 2005

AbstractA multiple repass system, utilizing an in‐line switching valve and suitable for use with small‐bore glass open tubular columns, is described. The advantages of the system, which include higher OPGV, large plate numbers and optimization of column “length”, are discussed.
A new surface roughening method for glass capillary columns. Sodium chloride deposition from suspension
Authors: de Nijs René C. M. , Rutten Gerard A. F. M. , Franken Josef J. , Dooper René P. M. , Rijks Jacques A. 
Published: May 2005

AbstractA method is described for roughening the surface of glass capillary columns for subsequent coating with polar stationary phases. A suspension of sodium chloride, obtained by addition of a saturated solution of sodium chloride in methanol to 1,1,1‐trichloroethane, is passed through the column at velocities of 1–5 cm/s. During passage of the suspension, particles of sodium chloride deposit spontaneously on the column wall. The amount of sodium chloride deposited on the column wall is a function of the volume of the suspension passed through and of the contact time of the suspension and the column wall. Ultimately the amount of sodium chloride per unit surface area approaches a maximum. Columns covered with this maximum amount of sodium chloride were prepared with high reproducibility and coated with a number of polar stationary phases. Various factors that influence the stability of the suspension and the deposition of sodium chloride are discussed and minimum requirements are given. A theoretical model is proposed for the mechanism of deposition of sodium chloride particles on the glass wall.
Analysis of nitrosamines by GC2 with a photoionization detector
Authors: Meili J. , Brönnimann P. , Brechbühler B. , Heiz H. J. 
Published: May 2005

AbstractThe use of a photoionization detector (PID) coupled to a glass capillary gas chromatography (GC2) separation system for the detection of carcinogenic nitrosamines was investigated. The components analyzed gave a linear response with a lower detection limit of 50 to 100 pg with the 10.2 eV ionization source. No detector response was obtained with an ionization energy of 9.5 eV.Chromatography of meat extracts indicated their complex molecular composition. Simple liquid chromatographic cleaning procedures significantly decreased the complexity of these samples, but not sufficiently for the accurate quantition of nitrosamine components.
HPLC with chemically bonded stationary phases. 1. ω‐hydroxyalkyl silicas
Authors: Matlin S. A. , Tinker J. S. 
Published: May 2005

AbstractGrignard and trichlorosilane coupling methods have been applied to the synthesis of surface‐modified silicas carrying alkyl chains of varying length, terminally substituted by a hydroxyl group. The new phases have been characterized chromatographically using aromatic hydrocarbons, substituted anilines and metal acetylacetonates.
Design of a microprocessor‐controlled automated injection system for the analysis of gas phase cigarette smoke using glass capillary columns
Authors: Parrish Milton E. , Higgins Charles T. , Douglas D. R. , Watson Duane C. 
Published: May 2005

AbstractAn automatic injection system for the analysis of gas phase smoke has been designed and evaluated using the microprocessor‐controlled Hewlett‐Packard 5830 gas chromatograph. The cryogenic preconcentration trap was constructed from relatively inexpensive and readily available materials. It was determined that the use of the preconcentration trap, as opposed to condensing the smoke on the head of the cold (‐50°C) chromatographic column, significantly enhanced the resolution of the more volatile gas phase components. Data are presented which illustrate the injection system characteristics. In addition, chromatograms of gas phase smoke are presented which demonstrate the effectiveness of this technique.
A rapid, new and direct method for isolation and measurement of porphyrins in biological samples by high performance liquid chromatography
Authors: Englert Edwin , Wayne Anthony W. , Wales Eugene E. , Straight Richard C. 
Published: May 2005

AbstractReversed‐phase high performance liquid chromatography on microparticulate columns of octadecylsilane with elution by a gradient of acetonitrile in phosphate buffer, pH 7.5, separated porphyrin free acids directly in urine for the first time. Interfering fluorescence was removed with a precolumn of large particle size at acid pH. Peak area fluorescence by the method of standard addition was related linearly to amount of a porphyrin from 5 to 60 nanograms. The method was reproducible to ± 13%, able to detect 0.3 nanograms of a porphyrin in a 1 ml urine sample in 45 minutes, and capable of detecting the typical clinical patterns of normal and porphyrinuric urines. Modifications make the method applicable to measurements in other biological samples and to research separations. With the added rapidity of analysis, the method could expand porphyrin analysis in routine clinical medicine.
Analysis of polar compounds on PEG‐40M/KF glass capillary columns
Authors: Golovnya R. V. , Samusenko A. L. , Mistryukov E. A. 
Published: May 2005

AbstractThe chromatographic properties of potassium fluoride as an additive to the polyethylene glycol stationary phase were investigated. This unique base in organic chemistry was shown to succeed in yielding good results for the analysis of polar compounds, including the primary amines. Glass capillary columns of high selectivity for primary and secondary aliphatic amines were obtained by the “hexane plug” procedure by which a thin layer of KF is deposited on the inner surface of glass capillary columns. Some possible types of donor‐acceptor interactions occuring within the system PEG/KF/solute were considered.
The identification of tricyclic neuroleptics and sulphonamides by high‐performance thin‐layer chromatography
Authors: Po A. Li Wan , Irwin W. J. 
Published: May 2005

AbstractCircular high‐performance thin‐layer chromatography (HPTLC) has been used to differentiate a series of twelve tricyclic neuroleptics, using both normal phase and reverse phase procedures. The use of normal phase systems also allows the resolution of geometric isomers of chlorprothixene, clopenthixol and flupenthixol. Thirteen sulphonamides and Trirnethoprim may also be distinguished using HPTLC.
Densitometric determination of unsaturated fatty acids with p‐hydroxybenzaldehyde by HPTLC
Authors: Gübitz  
Published: May 2005

AbstractA rapid method for the detection and quantltatlve determlnation of unsaturated fatty acids by TLC is presented. After separation on HPTLC‐RP18‐plates, reaction wlth p‐hydroxybenzaldehyde is carried out by a dipping procedure. Nanogram amounts of unsaturated fatty acids can be determined with good reproducibility.
Separation and identification of lichen acids of the pulvinic acid series
Authors: Chawla H. M. , Gambhir I. , Kathuria L. 
Published: May 2005

AbstractLichen acids, pulvinic acid, vulpinic acid, pinastric acid, leprapinic acid, lsoplnastric acid and pulvinic acid dilactone, which occur in certain yellow varieties of lichens and are difficult to separate, have been successfully separated and identified by TLC on chlorobenzene‐impregnated silica gel plates.
Direct measurement of mass fragmentograms for eluents from a micro‐liquid chromatograph using an improved nebulizing interface
Authors: Yoshida Yu , Yoshida Hiromasa , Tsuge Shin , Takeuchi Tsugio , Mochizuki Koichi 
Published: May 2005

AbstractAn improved vacuum nebulizing interface with a very short counter nozzle was developed for direct coupling of a micro‐LC and a quadrupole MS with CI‐chamber. With the LC‐MS system using the nebulizing interface, it became possible to take mass fragmentograms for various less volatile compounds such as glutamic acid, steroids, aromatic amines and chlorine‐containing insecticides.
HPLC of fatty acid esters of mono‐ and polyhydric alcohols. Part 1: Analytical separation
Authors: Henke H. , Schubert J. 
Published: May 2005

AbstractThis paper shows how simply and yet very rapidly fatty acid esters of monohydric alcohols, but particularly partial and full fatty acid esters of fully hydric alcohols can be separated and determined by means of high‐pressure liquid chromatography on LiChrosorb RP‐8 with methanol/water. We have separated quantitatively the methylesters of the fatty acids C8:0 to C22:0 and C24:0, the i‐propyl‐, i‐butyl‐, n‐hexyl‐ and i‐octyl‐esters of the even‐numbered fatty acids C8:0 to C18:0, mono‐ and difatty acid esters of the 1,3‐bis‐(2‐hydroxyethyl)‐5,5‐dimethyl‐hydantoin, mono‐, di‐ and triesters of the trimethylolpropane as well as the tetraesters of the penta‐erythrite.
Separation of histamine and its metabolites using glass capillary gas chromatography and a nitrogen detector
Authors: Lieu Fong‐Yi , Jennings W. 
Published: May 2005

AbstractComplete separation of the TMS derivatives of histamine, 1‐methyl histamine and 3‐methyl histamine was achieved in two minutes in a 7 m × 0.25 mm column coated with SP 2250. Using NPD, histamine was detectable at levels as low as 20 pg. This offers a rapid, sensitive procedure with potential for clinical diagnosis and food analysis.
Comparison of dynamically coated SE‐54, SP‐2250 and carbowax 20M wall‐coated open tubular (WCOT) glass capillary columns, prepared after surface pretreatment with Superox™‐4 or with BaCO3
Authors: Arrendale R. F. , Smith L. B. , Rogers L. B. 
Published: May 2005

AbstractA new surface pretreatment for the preparation of wall‐coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non‐extractable layer of Superox™‐4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox‐4 is stable at high temperatures (> 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE‐54, Carbowax 20M, and SP‐2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO3 procedure. The Superox‐4 pretreated columns were equal or superior in quality to the BaCO3 pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (Neff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.
Retention time and effective separation factor in series‐coupled columns with different stationary phases
Authors: Smuts T. W. , De Clerk K. , Du Toit T. G. , Buys T. S. 
Published: May 2005

AbstractBasic expressions are derived for both the retention time and the effective separation factor in serially coupled GC columns. The retention time is determined by two main parameters. The first is the fractional time spent by an unretarded solute in each column which, in turn, is determined by the relative column lengths and flow velocities through each column. The second parameter is the relative mass distribution coefficient of a particular solute in each column; a variable that can be adjusted by changing the relative temperatures of the columns. The expression for the effective separation factor relates the measured separation factor for the series combination to the separation factors on the individual columns, the fractional time spent by an unretarded peak in each column, as well as the relative values of the mass distribution coefficients of a particular solute on the different columns.
Gas‐liquid chromatographic determination of moprolol (SD 1601) in human plasma and urine
Authors: Desager J. P. 
Published: May 2005

Abstract1‐(o‐methoxyphenoxy)‐3‐isopropylamino‐2‐propanol hydrochloride (moprolol, OmeralR), is a new β‐adrenergic blocking agent. A gas chromatographic method for determining unchanged moprolol in human biological fluids has been developed. After solvent extraction, a bis‐trifluoroacetyl derivative was formed and measured by an electron capture detector. The quantification was checked by using an internal standard (pronethalol), which was added to all samples. The electron capture response was linear between 10 and 500 ng/ml. To avoid contamination of the peaks, careful extraction was imperative. The main advantages offered by the described method are: specificity, high sensitivity (10 ng.ml−1) and the small amount of biological fluids (1 ml plasma a. e.) required.
Identification of hydroquinone and catechol as impurities in reagent‐grade phenol using high performance liquid chromatography with ultraviolet and electrochemical detectors
Authors: Masoud A. N. , Dubes G. R. 
Published: May 2005

AbstractSeveral impurities which were suspected to be present in commercial reagent‐grade phenol were separated using high performance liquid chromatography following sample concentration by steam distillation. A reverse‐phase, microparticulate column and 5 solvent systems containing 5% to 25% methanol in 0.05 M phosphoric acid were used. A variable wavelength ultraviolet detector and an electrochemical detector were connected in series, in that order, to the column. Capacity factors (ḱ) for pyrogallol, hydroquinone, resorcinol, catechol, orcinol and phenol were determined in the 5 solvent systems and compared to ḱ‐values of impurities present in the residue remaining from the steam distillation of phenol. Co‐chromatography of standards suspected as contaminants and possessing ḱ‐values similar to those of impurities were carried out in 3 solvent systems to confirm identical retention characteristics. Detector response ratios of contaminants and suspected standards, using various wavelengths and voltage potential settings, were utilized as major identification parameters. Two of the several contaminants separated were identified as hydroquinone and catechol.
Detection of an impurity (1%) at low resolution (0.25)
Authors: Rix H. , Malengé J. P. 
Published: May 2005

AbstractThe “Distribution Function Method”, which makes possible the measurement of systematic variations in the shape of signals, has been experimentally tested on the detection of two visually confounded gas chromatographic peaks, irrespective of the estimation of the resolution or the concentration ratio. Two detection procedures are suggested. The first compares directly, under the same experimental conditions, the shape of a pure peak and that of a peak suspected of contamination. The second makes use of variations of column temperature and gas flow rates to distinguish the behaviour of a pure substance from that of a contaminated substance. A marking procedure for the shape of a pure peak is then set up to dispense with the need of a reference standard. In practice, the two procedures make possible the detection of heptane as an impurity in n‐hexane at levels of one percent and under experimental conditions artificially chosen so as to make the resolution inferior to 0.25.
Steroid analysis by gas chromatography with SCOT and wide‐bore WCOT columns
Authors: Thomas B. S. 
Published: May 2005

AbstractGlass capillary columns are ideal for analysis of urinary steroid profiles (i.e. the total steroid neutral fraction without prior separation into sub‐groups).In this paper performance of both SCOT and wide‐bore WCOT columns has been compared, resulting in no significant quantitative difference on urine extracts run as trimethylsilyl ether derivatives. However, because of increased efficiency the WB‐WCOT column exhibited more sensitivity in measurement of small amounts of 11‐ox‐aetiocholanolone. Sensitivity of other steroids was greatly enhanced by use of either SCOT or WB‐WCOT, leading to an almost tenfold increase over conventional packed columns (e.g. androsterone and aetiocholanolone < 40 μg per 24 h urine sample). A simple splitless injection system (based on a design of Dr. W. Greenaway, Oxford University) is presented.Experiments were also carried out using a SCOT column in conjunction with an FM‐electron capture detector. Whilst efficiency was impaired due to the design of the detector, use of He (carrier) and N2 (make up gas) showed that several steroid derivatives could be easily measured at well below the 10−10 g level with much more rapid retention times than with a 1½m packed column. Highly successful separation of 19 amino acids (as fluoro‐acyl derivatives) was achieved in 35 minutes using a SCOT (30 m) SP2100 column.
Assay of trimethoprim, sulfamethoxazole and its N4‐acetyl metabolite in biological fluids by high‐pressure liquid chromatography
Authors: Ascalone V. 
Published: May 2005

AbstractA reversed‐phase HPLC assay method was developed to determine levels of the drugs trimethoprim, sulfamethoxazole and the N4‐acetyl metabolite of the latter in human blood plasma and urine. The organic substances are extracted with ethyl acetate by a single extraction at pH 6.8. The method is rapid, accurate, sensitive and precise and well suited to routine determination of these drugs on patients during clinical pharmacokinetic investigations.