bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarizable biphenyl polysiloxane stationary phase for capillary column gas chromatography
Authors: Kuei J. C. , Shelton J. I. , Castle L. W. , Kong R. C. , Richter B. E. , Bradshaw J. S. , Lee M. L. 
Published: May 2005

AbstractA crosslinkable biphenylmethylpolysiloxane stationary phase was synthesized for capillary column gas chromatography and compared with methyl, phenyl, and cyanopropyl polysiloxane stationary phases for the separation of isomeric polycyclic aromatic compounds. While the new phase gave similar separations of nonpolar isomers when compared to the nonpolar phases, separations of polar isomers were greatly improved because of the induced polarity of the biphenyl group of the stationary phase by the solute molecules. This polarizable stationary phase offers a unique selectivity which is not available in other stationary phases.
A unique reversal of elution order during direct enantiomeric resolution of amide derivatives of 1‐phenyl‐2‐aminopropane by high performance liquid chromatography on chiral stationary phases
Authors: Doyle T. D. , Wainer I. W. 
Published: May 2005

AbstractEnantiomeric amide derivatives of (S)‐ and (R)‐1‐phenyl‐2‐aminopropane (dextro‐ and levoamphetamine, respectively) were resolved by high performance liquid chromatography on commercially available ionically and covalently bonded chiral stationary phases ((R)‐N‐(3,5‐dinitrobenzoyl)phenylglycine). Ten enantiomeric amide pairs were synthesized and chromatographed on the columns by using a mobile phase of hexane‐isopropanol (97 : 3), a flow rate of 2 ml/min, and a column temperature of 20°C. The (R)‐isomer of all 10 amides eluted first on the covalent column as did the (R)‐isomer of nine derivatives on the ionic column. however, the 3,5‐dinitrobenzoyl amide of (S)‐ amphetamine eluted before the (R)‐isomer on the ionic column. This reversal in enantiomeric elution order reveals the complexity of the interactions occurring on these columns and emphasizes the hazards of relying on observed elution order as an a priori indication of absolute configuration.
The stationary phase capacity concept in elution liquid chromatography
Authors: Gareli P. , Semerdjian L. , Caude M. , Rosset R. 
Published: May 2005

AbstractThe stationary‐phase capacity concepts derived from linear capacity are discussed in connection with the needs of analytical, trace enrichment analysis and preparative chromatography and shown to be unsuited to them. A new concept based on stationary‐phase saturation and called “available capacity” is proposed. It generalizes the ion‐exchanger exchange capacity to adsorption and partition chromatography when the sampling solvent is the mobile phase.In linear elution chromatography the available capacity is proportional to the solute concentration Co and to the analytical capacity factor k′ for given Co and k′ values, it is independent of the nature of the solute. Furthermore, when both the concentrations and the analytical capacity factors (practically, for Co ≥ 1 M and k′ ≥ 10, respectively) are high, the available capacity reaches a value roughly independent of Co and k′, called “maximum available capacity” and related only to the number of sites available on the stationary phase. Numerous measurements were made in ion‐exchange, adsorption, and reversed‐phase chromatography. For solutes having a single polar functional group interacting with the stationary phase, the orders of magnitude of the maximum available capacity are 1.2 mmole g−1 for a classical silica gel (Partisil 5 μm, 400m−2 g−1 with a water content of 2.7%); 1.8 mmole g−1 for the Lichroprep RP 8 octyl bonded silica (11.6% carbon content); 3.8 mmole g−1 for an anion exchanger resin of Dowex type.
Migration of the mobile phase and zones of separated substances in flat‐bed chromatography
Authors: Gimpelson V. G. , Berezkin V. G. 
Published: May 2005

AbstractIt is proposed to extend the area of application of circular separation of substances in flat‐bed chromatography by a wider use of its intermedial modifications. Equations for calculating the basic parameters of migration of the mobile phase and zones of separated substances are given. The known equations are shown to be particular cases of the ones proposed.
Threshold temperatures for solute mobility. Their determination and effect on programmed temperature gas chromatographic separations
Authors: Saxton W. L. 
Published: May 2005

AbstractThe threshold temperature for solute mobility is defined as that temperature at which a solute band, which was initially cold trapped at the head of the column, begins moving through the column. It is shown that the separation of compounds by programmed temperature gas Chromatography (PTGC) occurs primarily at the head of the column as a result of differences in threshold temperatures. Additional column length beyoud that needed to trap the compounds improves resolution, primarily by delaying emergence (while maintaining the temperature and time spacing) thus allowing the column temperature to rise, the solute terminal velocities to increase, and narrower peak widths to be recorded. For maximum resolution in minimum analysis time, the initial temperature must be at or below the threshold temperature of the most volatile compound in the mixture to be separated.Three methods for determining threshold temperatures are presented.
Determination of flurazepam and its hydroxyethyl and dealkyl metabolites by some packed and capillary ECD‐GLC methods: Application to pharmacokinetic studies
Authors: Coassolo Ph. , Aubert C. , Cano J. P. 
Published: May 2005

AbstractA sensitive gas‐liquid chromatographic assay was developed for plasma determinations of flurazepam (F), N1‐desalkylflurazepam (DF), and N1‐hydroxyethylflurazepam (HF). The internal standards used were delorazepam for F and DF and 1 ã‐hydroxymidazolam for HF. Following extraction and derivatization for HF, these compounds were analyzed by ECD‐GLC, using either glass packed columns (poly A 103 for F and DF, OV 225 for HF) or CP‐Sil 5 capillary columns for DF and HF. The detection limit of the packed‐column assay was approximately 3ng/ml for HF and DF, and 5ng/ml for F; with capillary GLC analysis, the sensitivity limit for HF and DF was lower than 1 ng/ml. These methods were used for pharmacokinetic investigations after i. v. administration of these compunds.
Clean‐up of polynuclear aromatic hydrocarbons and 3‐ring azaarenes and their GC‐analysis on whisker‐walled open tubular columns
Authors: Spitzer T. , Dannecker W. 
Published: May 2005

AbstractA modified clean‐up of polynuclear aromatic (PNA) hydrocarbons on XAD‐2 is described. n‐Alkanes (C16C28) are separated quantitatively from the PNA hydrocarbons and are eluted in one fraction. The distribution of 17 PNA hydrocarbons and four of their alkyl derivatives, two S‐heterocyclic compounds and two azaarenes between the different fractions is reported. Azaarenes containing three rings are separated from PNA hydrocarbons and S‐heterocyclic compounds. Whisker‐walled open tubular columns coated with OV‐215 and OV‐25 were used in the separation of isomeric azaarenes and in PNA hydrocarbon profile analysis, respectively. The preparation of such columns is described in detail. Rinsing of capillary columns with cold, concentrated HCI after whisker growth removes much larger amounts of boron and sodium than subsequent leaching with HCI at 180°C. Whisker‐walled open tubular columns are successfully applied to the characterization of isomeric benzofluoranthenes and other PNA hydrocarbons isolated from air particulate matter.
Increased speed of steroid analysis by capillary GC and GC‐MS; effects of sample pretreatment and sample introdution
Authors: Curvers J. , Maris F. , Cramers C. , Schutjes C. , Rijks J. 
Published: May 2005

AbstractQuantitative analysis of steroids and their metabolites in urine samples calls for increased speed of sample clean‐up, of the derivatization procedure, and of separation. A fast procedure for sample pretreatment, which can be performed within 8 hours, is introduced and evaluated. It is shown that use of fast pretreatment in combination with narrow bore columns, which are compatible with existing instrumentation, can considerably increase, laboratory throughput. The effect of different sample introduction techniques (e.g. splitless, on‐column, and moving needle) on column efficiency and resolution is demonstrated and discussed.
HPLC of nucleotides. II. General methods and their development for analysis and preparative separation. An approach to selectivity control
Authors: Wulfson A. N. , Yakimov S. A. 
Published: May 2005

AbstractIn order to develop efficient separation methods for nucleotides according to their size and heterocyclic composition, the application of ion‐exchange, reverse‐phase, and normal‐phase adsorption HPLC has been studied. The comparative investigation of retention power and selectivity of various packings (non‐polar bonded‐phase and amino silicas) in relation to nucleotide length and composition yields data which enable suitable packings to be selected and a method of preparing the new packing for a particular separation problem to be formulated. Thus a new anion exchanger with high selectivity and dynamic mass transfer has been prepared for fractionation of large oligonucleotides. The effect of the eluent pH and composition (organic modifier, salt) on retention, selectivity, and resolution in ion‐exchange and reverse‐phase HPLC has been studied. The optimum separation conditions comprise elution with oppositely directed gradients of the salt and the modifier, use of a precolumn packing that provides the best protection for the main column without loss of its efficiency, and the optimum gradient program for the desired retention of the component of interest. The relation between loading and sample concentration has been studied and the system for gradient elution improved. Our work shows that two‐dimensional separation is the most reliable and informative method for preparation of homogeneous oligonucleotides. The hydrophobic‐pair ion‐exchange mechanism is proposed for ion‐pair chromatography. Protected and partially deblocked oligonucleotides, chemically synthesized for genetic engineering studies, have been separated with high selectivity by adsorption (normal‐phase) HPLC which is efficient for gradient elution with isohydric eluents. The analysis of a monomeric composition of nano‐(pico‐) molar amounts of oligonucleotides has been developed; the procedure involves microcolumn digestion of the oligonucleotides with immobilized enzymes followed by microcolumn separation of the nucleoside‐mononucleotide mixture. Also, a new slurry method for packing stable HPLC columns with a tightly consolidated, nonshrinkable bed of particles has been developed.
Preparative HPLC. Part 1: A comparison of three types of equipment for the purification of steroids
Authors: Matlin S. A. , Chan L. 
Published: May 2005

AbstractTwo commercial preparative liquid chromatographs have been evaluated for gram‐scale purification of steroid esters. The Jobin‐Yvon and Waters chromatographs both allow fast separations. Neither system has a high intrinsic column efficiency, but the resolving power of the Waters system can be increased by the use of recycle. A laboratory‐assembled preparative liquid chromatograph is described which is economical both in construction and operation, versatile, and considerably more efficient than the two commercial alternatives for single runs on up to a gram scale.
Immobilization of stationary phase films by gamma radiation. Part 1. Nonpolar phases, regular and thick‐film capillaries
Authors: Vigh Gy. , Etler O. 
Published: May 2005

AbstractBorosilicate glass capillaries, silylated and coated with OV‐1 or SE‐54, were irradiated by a 60Co gamma source. The effect of radiation on chromatographic performance was determined for a series of dosages and was evaluated before and after rinsing with solvent. Results for both regular and thick films were obtained.
Reaction gas chromatography/mass spectrometry. Part IX: Post‐column hydrodesulfurization in capillary GC/MS as an aid in structure elucidation of cyclic sulfides within mixtures
Authors: Mikaya A. I. , Trusova E. A. , Zaikin V. G. , Zegel'man L. A. , Urin A. B. , Volinsky N. P. 
Published: May 2005

AbstractThis article describes a method that assists in structure determination of cyclic sulfides mixtures by GC/MS. The method involves the use of a gas‐phase hydrodesulfurization microreactor (AP‐56 catalyst, reaction temperture 300‐315°C, hydrogen as a carrier and reagent gas) located between the capillary column (OV‐17) and the mass spectrometer. The presence of a microreactor in such a position does not essentially affect the chromatographic separation achieved by using the capillary column. Combined analysis of the mass spectra registered for the original sulfides and the hydrodesulfurization products permits the structure determination of each effluent to be made more reliably. This is illustrated by the investigation of a reaction mixture containing the structural and geometric isomers of methyl‐substituted thiabicyclononanes.
Identification and quantification of diesel fuel components derived from off‐shore drilling operation discharges
Authors: Hiatt M. H. , Jones T. L. 
Published: May 2005

AbstractA GC/MS technique that provides quantitative and qualitative information on diesel fuel components in drilling muds is described. Several low molecular mass aromatic components of diesel fuel are identified as indicators of diesel fuel. The presence and relative concentration of these indicators is used to identify diesel fuel contamination. This information can be used to approximate the amount of diesel fuel contamination in off‐shore drilling discharges.
In‐product jojoba determination using anticircular high performance thin layer chromatography
Authors: Studer A. , Traitler H. 
Published: May 2005

AbstractCosmetic creams were analyzed for their content of jojoba wax and shea fat using anticircular HPTLC, a fast, precise, and reliable method. After optimization of the solvent system (petrol ether/diethyl ether) for the separation of jojoba wax and shea fat, the spots were visualized with phosphomolybdic acid by the “dip‐in” technique, subsequently heated, and finally recorded by scanning with a densitometer at 546 nm. Results showed that one particular concentration range gives an optimum correlation between calibration curves and sample evaluations.
Analysis of gases containing inorganic and organic compounds using a combination of a thick‐film capillary column and a packed adsorption column
Authors: Coleman P. , Ettre L. S. 
Published: May 2005

AbstractA gas chromatographic system consisting of one multiport valve, two (hot‐wire and flame‐ionization) detectors and two analytical columns (one thick‐film capillary and one packed adsorption column) is used for the analysis of gas samples containing a number of inorganic compounds (hydrogen, argon, oxygen, nitrogen, carbon monoxide, and carbon dioxide) and organic compounds. Examples include samples containing hydrocarbons up to n‐nonane and benzene and toluene. The system also permits the analysis of more complicated samples containing, for example, alcohols, in addition to hydrocarbons.
Thermospray high performance liquid chromatographic/mass spectrometric analysis of some fusarium mycotoxins
Authors: Voyksner R. D. , Hagler W. M. , Tyczkowska K. , Haney C. A. 
Published: May 2005

AbstractThermospray high performance liquid chromatography/mass spectrometry (TSP HPLC/MS) was used to analyze five Fusarium mycotoxins in porcine plasma and urine. Four cytotoxic trichothecene mycotoxins, T‐2 toxin, HT‐2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), T2 tetraol, and the fungal estrogen zearalenone (F‐2 toxin) were analyzed. The thermospray mass spectrum contained molecular weight information with few, if any, fragment signals. Detection limits ranging from 1 to 10 ng of mycotoxin injected onto the HPLC column were obtained using selected ion monitoring (SIM) HPLC/MS. Neither the plasma nor the urine matrix interfered with TSP HPLC/MS analysis of these mycotoxins and no sample derivatization was necessary for the analysis. The TSP HPLC/MS technique appears to be ideal for very sensitive analysis of mycotoxins in biological samples.
Free release static coating of glass capillary columns; rapid coating at lower temperatures and elevated pressures
Authors: Xu B. , Vermeulen N. P. E. 
Published: May 2005

AbstractThe coating speed upon static coating of glass capillary columans was evaluated in terms of inner diameter and length of the column, viscosity and pressure of solvent vapor, etc. From the equation obtained it can be shown that a smaller diameter of a microbore column restricts solvent vapor transfer to the orifice of the column drastically. To compensate for this restriction, a higher pressure at the meniscus is needed. As an alternative to using a higher coating temperature, application of more volatile solvents such as n‐butane and isobutane is proposed. Several glass capillary columns (130 μm i.d.) were coated with SE‐54 dissolved inpentane‐acetone mixed with n‐butane or isobutane and the column performances were evaluated. Selection of these solvents permitted free release static coating of ca. 100 μm columns at lower or even ambient temperatures and they were equally suitable as commonly applied solvents (e.g. pentane) to coat highly efficient columns.
Disengaging solutes in shale‐ and petroleum‐derived jet fuels by altering GC programmed temperature rates
Authors: Hayes P. C. , Pitzer E. W. 
Published: May 2005

AbstractOverlapping chromatographic peaks of components from different hydrocarbon classes can be disengaged by exploiting their shifts in relative retention behavior with changes in linear rates of programmed temperature. Many co‐eluting species in complex chromatograms of shale‐ and petroleum‐derived jet fuels can be resolved without varying stationary phase, column length, or initial column temperature.Retention indices were simultaneously determined on two bonded‐phase, fused silica capillary columns of slightly different polarities at three different linear programmed temperature rates. For certain hydrocarbon types, no change in index values was observed with an alteration in programming rate. However, the indices of other hydrocarbon classes shifted uniformly with programmed temperature rates on each of the two stationary phases. When applied, this phenomenon could help resolve coeluting members of different or even the same hydrocarbon type and elucidate their probable structure. The overall precision of the retention indices, i.e., the mean standard deviation at the 95% confidence levels, was less than ±0.13 for either column at any of the three programming rates. Since the above technique is automated, it could also be a useful screening tool to search for specific hydrocarbons in a myriad of unknown components of a complex hydrocarbon mixture.
Assessment of the results from data processing systems using a digital chromatogram simulator
Authors: Hunt R. J. 
Published: May 2005

AbstractA digital chromatogram simulator has been used to evaluate the performance of data handling systems. The simulator can synthesize chromatograms with any desired shape from a library of peaks based on real peak shapes. Once generated, the chromatograms can be reproduced exactly any number of times.The algorithms used in data handling systems have a significant effect on the results they produce. An object of this work was to examine how well the true size of a peak was reported when the peak was detected overlapping with other peaks. A series of experiments was therefore performed in which peaks were overlapped by different amounts and in different situations. The reported results from the data systems were compared with the results which would have been reported had the peaks been fully resolved. A significant difference was found between the overlap results and the fully resolved results, which did not have a linear relationship with the parameters tested.The chromatogram simulator was found to be a powerful tool in assessing the performance of the data systems. It offers a valuable means of evaluating the quality of the results produced by these systems.
Deactivation of fused silica capillary columns with phenylhydrosiloxanes
Authors: Markides K. E. , Tarbet B. J. , Woolley C. L. , Schregenberger C. M. , Bradshaw J. S. , Lee M. L. , Bartle K. D. 
Published: May 2005

AbstractIn this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation and surface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using the capillary rise method. The deactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.
Temperature dependence of the resolution of diastereomeric isoprenoids in capillary GC. Experiments with 50 μm, 100 μm, and 250 μm i.d. Columns
Authors: Proot M. , David F. , Sandra P. , Verzele M. 
Published: May 2005

AbstractThe resolution of the diastereoisomers of norpristane, pristane, and phytane was studied as a function of the column internal diameter and/or the residence time of the compounds in the column. Increasing the residence time in the column by operating the column at a lower temperature program rate enhances the resolution more than reducing the internal diameter of the column. Practical experience with ultra narrow bore columns is also presented.
High resolution gas chromatographic determination of permanent gases with a helium ionization detector
Authors: Verga G. R. 
Published: May 2005

AbstractThe capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS‐255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on‐column injections also have been investigated with promising results.
Topical administration of ibuprofen in man. Simultaneous determination of the drug and its metabolites in urine by high resolution gas chromatography
Authors: Giachetti C. , Zanolo G. , Canali S. 
Published: May 2005

AbstractA selective and sensitive high resolution gas chromatography assay for simultaneous determination of Ibuprofen and its major metabolites in urine is described. Biological samples were collected from healthy volunteers after a single topical administration of the drug in gel form. The chromatographic system, developed on a WCOT OV‐1 glass capillary column, ensured a clear separation of Ibuprofen and its metabolites and their quantitative evaluation.
Variation of tube diameter and film thickness of capillary columns
Authors: Ettre L. S. 
Published: May 2005

AbstractThis paper briefly surveys three important considerations related to the tube diameter and film thickness. These are the interrelationship of these two parameters through the phase ratio, the different meanings of the term “efficiency”, and the influence of film thickness and tube diameter on sample capacity. Comparative examples are given for columns having different diameters and film thicknesses.
Characterization of silicone phases by alkaline hydrolysis and CGC analysis
Authors: Temmerman I. , Sandra P. , Verzele M. 
Published: May 2005

AbstractA simple way to elucidate the functional group substitution on silicone chains is presented. The polymer is decomposed into its monomers by alkaline hydrolysis. These monomers are converted into trimethylsilyl derivatives, which are then analyzed and identified by capillary gas chromatography/mass spectrometry.