bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the statistical independence of various column contributions to band broadening. Part 1: Second moment contributions from statistically independent, longitudinal diffusion in both phases
Authors: Nilsson Olle 
Published: May 2005

AbstractThe total length‐based second moment contribution from longitudinal sample diffusion in both phases on a column, σD, is derived by adding individual partial differential contributions to a partial differential equation accounting for the longitudinal diffusion processes only. Although each diffusion‐dispersed sample part is equilibrated between two phases, the resulting σ,D (= 2Dmtm + 2Dsts) can be interpreted as the sum of two independent contributions in accordance with the variance addition rule. (Dm and Ds are the mean diffusion coefficients and tmand ts the mean residence times of the sample in the mobile and stationary phases, respectively.) The same σD expression is derived from the random walk model of Giddings by treating the diffusional process in each phase as statistically independent of the other processes. Under these conditions the broadening contribution from longitudinal diffusion in the mobile phase is shown to be independent of the velocity profile.
The deferred standard method–a technique for quantitative analysis in laboratory and process HPLC
Authors: Guillemin C. L. , Gressin J. C. , Caude M. C. 
Published: May 2005

AbstractAmong the methods of quantitation commonly used in chromatography, the internal standard may be considered as the most useful and accurate; however, use of internal standards in liquid chromatography with UV and fluorometric detectors runs into considerable difficulties because the response factors may differ from each other by several orders of magnitude. Under these conditions, the search for an IS with a response factor similar to that of the analyte and adequately resolved from other peaks may prove very tedious.The deferred standard concept, already used in process and laboratory gas chromatography, is proposed as a solution; its definition, details of instrumentation, operation, and results are described in this paper. The material presented demonstrates its ability to solve this specific problem. In addition, use of the deferred standard approach is seen to save time and money.
Vapor‐controlled thin‐layer chromatography on reversed‐phase layers
Authors: Volkmann D. 
Published: May 2005

AbstractThe chromatographic behavior of some hydrocarbons and some of their nitro derivates after preconditioning with solvent vapors has been investigated. After preloading with cyclohexane or hexane an improved separation of some sample pairs is observed. Furthermore, inversion of Rf values takes place. The preloading of the reversed‐phase plates permits utilization of mobile phase with higher water content, thus leading to a significant shortening of developing time.
Simultaneous use of fluorescence, ultraviolet, and electrochemical detectors in high performance liquid chromatography‐separation and identification of phenolic antioxidants and related compounds
Authors: Masoud A. N. , Cha Young Nam 
Published: May 2005

AbstractIsocratic conditions are described for the separation, identification and quantitation of selected phenolic antioxidants and related compounds by high performance liquid chromatography on a reverse phase microparticulate ODS column. Mobile phases containing 0.05 M lithium perchlorate in aqueous methanol are used. Three detection systems: ultraviolet; fluorescence; and electrochemical detectors are connected in tandem. The use of these three detection systems in sequence as additional means for separation, identification, and quantitation is demonstrated. Other advantages of the system include speed of analyses and improved detection. The Ḱ values and detector responses at 2 settings per detector for 12 compounds are reported.
On the statistical independence of various column contributions to band broadening. Part 3: Independent treatment of longitudinal diffusion in the plate model
Authors: Nilsson Olle 
Published: May 2005

AbstractIt is shown theorectically that the classical formula for calculating the theoretical plate number from squared first central moment, t, and second central moment, σ2, according to ntheor = t/σ2 is valid only when the capacity ratio, k approaches infinity. The general relation between the classical experimental HETP value, H = L/nmtheor, and the underlying true theoretical plate height, ΔL, is found to be

when (σ′)2 is the total column contribution to band broadening, L is the column length, Dm is the average diffusion coefficient of the sample component in the mobile phase, Ds is its value in the stationary phase, and u is the average linear velocity of the mobile phase. The mobile phase displacement, as well as the mass exchange process, is assumed to be continuous, but the application of the plate concept conditions leads to a mass balance equation that can be interpreted as belonging to a modified discontinuous plate model. The contributions 2Dm/u and k 2 Ds/u from longitudinal sample diffusion in the mobile and stationary phases, respectively, are consistent with the assumption that the processes are statistically independent, although the common solution technique of the differential equations does not take full account of this independence.
Determination of nitrated polycyclic hydrocarbons in aerosols using capillary gas chromatography combined with different electron capture detection methods
Authors: Oehme M. , Manø S. , Stray H. 
Published: May 2005

AbstractA method is described which allows the determination of subnanogram concentrations of mono‐ and dinitrated polyaromatic hydrocarbons with two to four ring systems in aerosol samples. High performance liquid chromatography is used to separate the nitro compounds from other classes of substances. Carbozoles elute in the same fraction. Both electron capture detection and negative ion chemical ionization mass spectrometry combined with capillary gas chromatography are used for quantification. Use of these two methods leads to a considerable improvement of selectivity and sensitivity for nitrated compounds. In contrast to the situation with a nitrogen‐sensitive detector, carbazoles do not interfere and detection limits in the order of 10–200 pg/m3 are possible. The applicability of the method is critically discussed. Determination of nitrated polyaromatic hydrocarbons in aerosol samples from an aluminum smelter serves as an example.
Methodology for isolating drug metabolites from biological fluids by HPLC
Authors: Overzet F. 
Published: May 2005

AbstractThis article presents a detailed account of the isolation of drug metabolites from bile by reverse‐phase HPLC. The systematic approach is illustrated for the metabolism of butoprozine, a new antianginal drug, in the dog. Separation utilizes isocratic and gradient elution. Detection of the metabolites in. the presence of endogenous bile components is accomplished by very selective radioactivity measurements, by less selective UV (single wavelength) detection, and by much more universal detection modes such as on‐line UV spectroscopy and off‐line mass‐ and nuclear magnetic resonance spectroscopy. The importance of the latter three techniques in purity analysis of isolated metabolites is illustrated.
Investigation of the low temperature effect in reversed phase micro high performance liquid chromatography
Authors: Jinno K. , Ohshima T. , Hirata Y. 
Published: May 2005

AbstractThe low temperature effect has been investigated in reversed phase micro high performance liquid chromatography with various aqueous mobile phase systems by an approach based on enthalpy‐entropy compensation. The compensation temperatures, Tc, were determined for these systems, and the results show that the retention mechanism in a lower temperature column is similar to that in a normal temperature column in the reversed phase mode at mobile phase water contents above 9.8%. At lower water contents, the separation mechanism is different from that in the reversed phase mode, but otherwise very similar to that in the normal phase mode.
Halogenated compound response in an oxygen doped ion mobility detector for capillary gas chromatography
Authors: Baim M. A. , Hill H. H. 
Published: May 2005

AbstractAn ion mobility detector that has been specifically developed for interfacing with capillary gas chromatography is investigated in the negative ion mode. Like the electron capture detector, to which this instrument is closely related, the ion mobility detector shows an enhanced response to low molecular weight halogenated compounds when a small quantity of oxygen is doped into the make‐up gas flow. Under O2 doping conditions, the device can operate in a reactant ion monitoring mode responding universally to compounds capable of capturing thermal electrons and in a tunable selective product ion mode providing increased selectivity over that achieved by the ECD. At an oxygen concentration of 0.5%, minimum detectable amounts as low as 600 femtograms have been realized for carbon tetrachloride. Selectivity of chloro‐ versus bromo‐ compounds is demonstrated using a mixture of p‐dichlorobenzene and p‐dibromobenzene.
Prediction of retention time of phenols in liquid chromatography
Authors: Hanai T. , Hubert J. 
Published: May 2005

AbstractThe chromatographic behavior of phenols in reversed‐phase mode liquid chromatography differs from that of non‐ionic compounds such as alkyl alcohols, alkylbenzenes, halogenated benzenes, polyaromatic hydrocarbons, and aromatic acids. Therefore, the retention times of 61 phenols were measured in a system of an octadecyl bonded silica gel and acetonitrile/water mixtures. The logarithm of the capacity ratio (log k') was found to be a linear function of the hydrophobicity (log P) in acidic acetonitrile/water mixtures. This result was applied to a different octadecyl bonded silica gel. Eight phenols were selected as standard compounds, and their log k' values were measured in 0.05 M phosphoric acid in 10 to 90% acetonitrile/water mixtures. An empirical polynomial relation was obtained between the concentration of acetonitrile and the slope of the log k' vs log P curve. Finally the capacity ratio of all phenols were calculated in given eluents by the equations derived from the measurements of standard compounds and the calculated log P values. The difference between predicted capacity ratios and measured ones was within 10%.
Influence of development distance on resolution in thin‐layer chromatography
Authors: Franke J. P. , Kruyt W. , de Zeeuw R. A. 
Published: May 2005

AbstractTheoretical equations are given to relate resolution with development distance. Comparative experiments undertaken with quaternary ammonium compounds as test substances and using a selection of basic drugs are presented. As expected, resolution decreases with shorter development distance. However, this effect is less pronounced for compounds with small Rf values and when the spot size at the starting point is kept small. It was also shown that, for correctly assessing resolution in relation to development distance, the amounts of material spotted have to be decreased for shorter development distances.
HPTLC analysis of organotin compounds in preservative solutions and preservative‐treated wood
Authors: Ohlsson Stefan V. , Hintze Wollmal W. 
Published: May 2005

AbstractA high‐performance thin‐layer chromatographic (HPTLC) method is described for the determination of tributyltin compounds (bis(tri‐n‐butyltin) oxide, TBTO, and tri‐n‐butyltin naphthenate, TBTN) and their degradation products (dibutyltin and monobutyltin compounds). The organotin compounds are extracted from wood with ethanol containing 0.5% (v/v) of hydrochloric acid and the separation of the defferent kinds of organotin compounds is achieved by thin‐layer chromatography. The sample spots are measured using a scanning densitometer after decomposing the organotin compounds to inorganic tin by ultraviolet irradiation and visualization of the spots with pyrocatechol violet.Applications of the method to detection and quantification of organotin compounds in preservative solutions, in recently impregnated wood, and in wood samples from five‐year‐old window frames are described.
Cutting of glass and fused silica capillaries
Authors: Roeraade J. 
Published: May 2005

AbstractAn investigation of techniques suitable for precision cutting of glass and fused silica capillary tubing has been carried out. Accurate trimming of capillary tubing is important when precision splitters and manifolds have to be made. Techniques employed for cutting optical fibers proved to be useful, and factors affecting the suface quality of the fracture are discussed.It was found to be difficult to obtain a square cut with a flat surface in the case of fused silica tubing. The best results were obtained when the tubing was scored with the edge of a broken silicon wafer before the fracture was accomplished. This technique allows precision cutting of glass tubing with an outer diameter of 100 μm or less.
Application of capillary gas chromatography to automated on‐line quantitative analysis of solvent vapors
Authors: Radell E. A. , Rea D. F. 
Published: May 2005

AbstractSolvent vapors in air may be measured with capillary gas chromatographic columns. By using large diameter columns and sample loops of approximately the same internal diameter, the column may be connected directly to the gas sampling valve. This approach eliminates the use of a splitter or cryogenic trapping and allows low levels to be measured. By operating the column at high velocity, column efficiency is sacrificed for increase in speed.
Gas‐liquid chromatographic determination of fenvalerate on woolen cloth
Authors: Simonaitis R. A. , Bry R. E. , Cail R. Spencer 
Published: May 2005

AbstractA method is described for the determination of fenvalerate (cyano(3‐phenoxyphenyl)methyl 4‐chloro‐α‐(1‐methylethyl)‐benzeneacetate) residues on woolen cloth. The fenvalerate was Soxhlet‐extracted from the treated fabric with acetone for four hours at a reflux rate of six solvent exchanges per hour. The fenvalerate residue was determined by gas‐liquid chromatography with a flame ionization detector. The results were quantitated by comparing integrator counts obtained from extracts of treated samples with those obtained from known standards. The method was sensitive to 0.00054% fenvalerate by weight. Recoveries from fabric treated with 0.00054% to 0.215% averaged 94.8%. The response of the detector was linear over a 400‐fold range of fenvalerate concentrations.
Behavior of fused silica capillaries subjected to gamma radiation. Part 1: Chromatographic performance
Authors: Hubball J. A. , DiMauro P. , Barry E. F. , Chabot G. E. 
Published: May 2005

AbstractFused silica capillaries deactivated with D4 and coated with OV‐1 were subjected to cobalt‐60 gamma radiation in order to elucidate the effect of incident radiation on column performance. The chromatographic performance of these open tubular columns in which OV‐1 was polymerized in situ was found to be dependent on the dosage of radiation and was evaluated before and after the irradiated columns were rinsed with solvent. Of the radiation dosages employed, 3 MRad produced superior chromatographic performance coupled with very favorable residual surface activity.
Residue analysis of organophosphorus pesticides in food with two‐dimensional gas chromatography using capillary columns and flame photometric detection
Authors: Stan H.‐J , Mrowetz D. 
Published: May 2005

AbstractTwo‐dimensional gas chromatography with two capillary columns of different polarity (SP 2100 and OV 225) is used for pesticide residue analysis in food samples. By means of “live chromatography” applying pneumatic switching technique according to Deans, unequivocal identification of 57 organophosphorus pesticides in food samples is achieved at trace concentrations. The instrument is equipped with only one injection port and one flame photometric detector. On‐line data processing is very helpful, especially in calibration and checking the system's reliability with the multitude of test compounds. The complete pesticide residue analysis including clean‐up of about six food samples can be completed by one person in 8 hours.
A method of calculating the specific retention volumes of substances from their retention indices and specific retention volumes of n‐alkanes
Authors: Golovnya R. V. , Grigoryeva D. N. 
Published: May 2005

AbstractThe choice of stationary phase for gas chromatography is dictated by the nature of the analytes. Polarity and selectivity are known to play an important role. This paper suggests equations for calculation of specific retention volumes of any compounds from their retention indices.
Behaviour of fused silica capillaries subjected to gamma radiation. Part 2: Physical aspects
Authors: Barry E. F. , Chabot G. E. , Ferioli P. , Hubball J. A. , Rand E. M. 
Published: May 2005

AbstractFive commercial varieties of uncoated fused silica capillary tubing used in high resolution gas chromatography were subjected to cobalt‐60 gamma radiation. The advantages and superior performance of fused silica open tubular columns coated with OV‐1 and subsequently immobilized or crosslinked in situ by radiation is reported in a previous paper in this Journal; however, in this investigation a loss in flexibility of irradiated capillaries was also noted. Quantitative measurements on flexibility were performed on specimens of irradiated fused silica capillaries, indicating that changes do indeed occur upon irradiation. Scanning electron micrographs also illustrate slight deterioration of the outer protective polyimide coating. Most surprisingly, it was also established that a variation does exist in the flexibility of the commercially available raw material studied.
Ion‐pair chromatography with UV absorbing counterions on reversed‐phase layers. Part 1: Chromatography with hydroxynaphthalenesulfonic acids
Authors: Volkmann D. 
Published: May 2005

AbstractThe results of ion‐pair chromatography with UV‐absorbing counterions are described. Hydroxynaphthalenesulfonic acids are used as ion pair formers, and alkaloids as test samples. The separations are performed on silanized silica gel from Merck and KC18F plates from Whatman. The influence of the counterion on the Rf‐value is demonstrated. Some alkaloids exhibit characteristic fluorescence as ion pairs.
Comparison of gas chromatographic and gas chromatographic/mass spectrometric techniques for the analysis of TNT and related nitroaromatic compounds
Authors: Weinberg D. S. , Hsu J. P. 
Published: May 2005

AbstractThe use of capillary column gas chromatography and gas chromatography/mass spectrometry for the analysis of a series of standard solutions (0.1 to 10 μg/ml) of 2,4,6‐trinitrotoluene (TNT) and eight other nitroaromatic components was evaluated. The techniques included gas chromatography with electron capture detection (GC/ECD), full scan and selected ion monitoring gas chromatography/mass spectrometry with electron impact ionization (EI/FS and EI/SIM), full scan and selected ion monitoring gas chromatography/mass spectrometry with positive ion chemical ionization using methane reagent gas (PICI/FS and PICI/SIM), and full scan and selected ion monitoring gas chromatography/mass spectrometry with negative ion chemical ionization using methane reagent gas (NICI/FS and NICI/SIM). The performance of the techniques was comapared by determining the linear response range, precision, and detection limits of the analyses.
A polar glass capillary column for residue work
Authors: Rinderknecht F. , Wenger B. 
Published: May 2005

AbstractPolydiethylene glycol adipate (DEGA) has been successfully used as stationary phase for residue analysis by glass capillary gas chromatography. A specially stabilized version of the phase yields a good polar column which is stable up to 250°C when used in temperature programmed cycles. The paper lists 90 pesticides that have been successfully chromatographed in ng quantities on a DEGA column.
An investigation of microbore reverse‐phase columns containing 3 μm packing materials
Authors: Vadukul N. K. , Loscombe C. R. 
Published: May 2005

AbstractA procedure for packing 15 cm × 1 mm id reverse‐phase microbore columns with 3 μm silicas obtained from different manufacturers is described. The speed of analysis and detection limits are compared to those obtained with a 50 cm × 1 mm id column packed with 10 μm ODS. The effect of detector time constant on the system, and flow rates on column efficiency are also examined.
Flavor analysis by HRGC/FT‐IR: Cherimoya (Annona cherimolia, mill.) fruit volatiles
Authors: Herres W. , Idstein H. , Schreier P. 
Published: May 2005

AbstractThe volatiles of fresh cherimoya (Annona cherimolia, Mill.) fruit pulp were separated by combined high‐vacuum distillationliquid/liquid extraction (pentane/dichloromethane 2+1). After preseparation by liquid chromatography on silica gel three fractions (I‐III) were obtained by eluting with pentane (I), pentane/diethyl ether (9+1) (II), and diethyl ether (III), and fractions II and III were subjected to HRGC/FT‐IR analysis. 26 volatile compounds comprising nearly all the main components (range, 10–300 μg/kg fruit pulp) were identified by this technique for the first time in cherimoya fruit.
Analysis of coal tar and petroleum pitches by computerized pattern recognition
Authors: Moncur J. G. , Bradshaw W. G. 
Published: May 2005

AbstractPyrolysis gas chromatography (P/GC) has been successful in differentiating coal tar pitches which are used in the manufacture of high temperature graphite materials [1,2]. In the present study, coal tar and petroleum pitches received from five suppliers were readily differentiated using three distinct methods of polymer analysis: dynamic headspace and pyrolysis gas chromatography mass spectrometry (DH/GC/MS and P/GC/MS, [3]), and pyrolysis mass spectrometry (P/MS, [4,5]). All of these methods are appropriate for the analysis and pattern recognition study of coal and petroleum products; however, methods which incorporate GC usually necessitate long analysis times and are subject to problems associated with gas chromatographic reproducibility (e.g. active sites [6], and nonconstant retention times). As a fingerprint analysis method, P/MS is rapid and ideally suited to computerized pattern recognition study of pitches due to the simple format of P/MS data (computer tabulation of normalized intensities versus masses); whereas, in the present study, the normalized peak area versus retention time date from DH/GC/MS and P/GC/MS analyses were not suitable for direct input to a computerized pattern recognition analysis program, (due to non‐constant retention times and improper data format). One limitation is that P/MS does not provide positive identification of thermally evolved products (as can DH/GC/MS and P/GC/MS) due to the complexity of the spectra of a mixture of compounds produced by P/MS. Within the limits of the commercial instrumentation and computer programs used in this study, a combination of all three techniques provided the greatest capability for the differentiation of the five coal tar and petroleum based pitches studied.
Influence of injection systems on the gas chromatographic analysis of oxygenated dibenzothiophenes
Authors: Vignier V. , Berthou F. , Picart D. 
Published: May 2005

AbstractAnalytical methods are described for identification and monitoring of the oxygenated metabolites of dibenzothiophene. Since such compounds are thermolabile, GC analysis is seen to be hardly feasible with conventional injectors such as all‐glass moving needle or splitless injectors. Only on‐column injection gives no degradation products. In addition, reversed‐phase HPLC is particularly suitable for the analysis of the sulfone or sulfoxides of dibenzothiophenes.