Showing papers in "Chromatographia in 1975"
TL;DR: In this article, a general introduction on the advantages and special requirements of gas chromatography in glass capillaries is described to an extent not convered in the authors' previous paper.
Abstract: After a general introduction on the advantages and special requirements of gas chromatography in glass capillaries the methods of preparing and testing thin film capillaries are described to an extent not convered in the authors' previous paper. By means of a series of chromatograms of typical artificial and genuine samples it is shown that the use of glass capillaries of variable length and with various stationary liquids does not present technical or methodical difficulties. With regard to temperature stability there is no difference in performance between packed and glass capillary columns. Moreover the preparation of glass capillary columns is easy, their separation efficiency is much better and the tailing behaviour is often superior in comparison with packed columns.
119 citations
TL;DR: Porous silica microspheres with bonded hydrocarbon phases have been prepared for high-performance reverse-phase liquid chromatography as mentioned in this paper, and these bonded-phase particles exhibit high efficiency because of their small size (∼7 μm), narrow particle size distribution, and excellent solute mass transfer characteristics.
Abstract: Porous silica microspheres with bonded hydrocarbon phases have been prepared for high-performance reverse-phase liquid chromatography. These bonded-phase particles exhibit high efficiency because of their small size (∼7 μm), narrow particle size distribution, and excellent solute mass transfer characteristics. Slurry-packed 25 cm×0.32 cm i. d. columns of 7 μm particles modified with octadecyl groups (18% C) exhibit plate height of <0.005 cm with water/methanol mobile phases at 50°C. The high concentration of octadecyl, dimethylbenzyl and trimethyl groups that are introduced by reaction with chlorosilanes minimizes band tailing due to solute adsorption by residual silanol groups on the support surface. These small particles are prepared with different size pores, which determine the level of organic stationary phase and resultant chromatographic retention. These particles with various pore sizes permit optimum reverse-phase interaction with solutes of different molecular weight.
98 citations
TL;DR: In this article, the capacity ratio k was determined for decane, hexadecane, eicosane, and squalane from SFC experiments between 30 and 70°C and up to 170 bar using chemically bonded Carbowax 400 and fluid carbon dioxide as stationary and mobile phases respectively.
Abstract: Capacity ratios k have been determined for decane, hexadecane, eicosane, and squalane (2,6,10,15,19,23-hexamethyltetracosane) from SFC experiments between 30 and 70°C and up to 170 bar using chemically bonded Carbowax 400 and fluid carbon dioxide as stationary and mobile phases respectively. The results show that log k (ρmob) isotherms are much more appropriate than log k (p) isotherms (ρmob = density of the mobile phase,p=pressure) for the discussion of the pressure and temperature dependence of k values from SFC experiments.
83 citations
TL;DR: The optimal conditions for maximum precision in chromatography without advanced data handling are determined.
Abstract: The uncertainty in the determination of the time integral of analytical signals due to base-line noise is calculated for specified noise types of frequent occurrence. The influence of time constants, integration time and analog or digital filters on the precision is considered. The optimal conditions for maximum precision in chromatography without advanced data handling are determined.
60 citations
TL;DR: An open split-type connection is described with a platinum capillary as the inlet line to the mass spectrometer, suited to various types of columns, but especially for glass capillaries.
Abstract: An open split-type connection is described with a platinum capillary as the inlet line to the mass spectrometer. This connection device is suited to various types of columns, but especially for glass capillaries. Advantages of the open split are (i) a rather high yield, (ii) high flexibility with regard to column parameters, and (iii) optimal reliability, because the open split requires no vacuum-tight seal of the column to the spectrometer and no special geometry of the column end. An additional feature is the possibility of suppressing very large (solvent) peaks.
60 citations
TL;DR: Practical applications of three such techniques, the principles of which are not new, are described; namely, multiple detection, odour analysis, and two-dimensional analysis.
Abstract: The fact that gas chromatography on glass capillary columns is far from being exploited to its full potential is due to two main reasons: widespread disappointment in poor quality columns and insufficient know-how in the application technique. In order to provide facts about the true situation, general information is given here about performance and durability of a large number of glass capillary columns currently in routine use, some of these for years, at various laboratories. It is emphasized that glass capillaries, as well as the related chromatographic technique and equipment, cannot be successfully considered and handled using the experience gained from packed columns, but should be given particular consideration. The majority of existing glass capillary columns are used for the analysis of complex mixtures. In many instances even extreme separation efficiency may not achieve sufficient resolution. In these cases ancillary techniques may fill the remaining gap. Practical applications of three such techniques, the principles of which are not new, are described; namely, multiple detection, odour analysis, and two-dimensional analysis. A new technique for the introduction of large gaseous samples onto capillary columns is presented with a detailed discussion of its mechanism.
56 citations
TL;DR: A system of collecting separated sub-μg fractions in glass capillary traps, which makes direc re-injection from these traps possible, completes the methods presented.
Abstract: Methods for the preparation of wide-bore glass capillary columns for gas chromatography are presented. The pretreatment of the columns (etching, carbonization, deactivation and/or surface-coating with porous materials), and the coating of them with polar or apolar phases (preferably by the static method) is described. The performance of the columns prepared is evaluated and a number of applications are given, such as analysis of volatile compounds, pesticides, lipids and GC/MS analysis. In some respects, the wide-bore glass capillaries have advantages over the narrow-bore types. They can be installed very easily in GC-instruments, and permit the analysis of larger samples. A system of collecting separated sub-μg fractions in glass capillary traps, which makes direc re-injection from these traps possible, completes the methods presented.
45 citations
TL;DR: In this paper, a general discussion of the separation number (TZ) and the effective peak number (EPN) is presented and their meaning and interrelationship is explained with help of a generalized term.
Abstract: A general discussion of the separation number (TZ) and the effective peak number (EPN) is presented and their meaning and interrelationship is explained with help of a generalized term. The relationship between the separation values and the retention index difference is derived and the choice of the homologous series and peak pair used for column testing is considered. The similarities and dissimilarities between the separation values and the number of theoretical plates and HETP and their respective advantages are discussed. In the second part of the paper, a further improvement in the separation value concept is proposed: the use of separation value vs. retention time plots as well as plots representing the rate of producing the separation values against the carbon number.
40 citations
TL;DR: In this paper, the relationship between the RM values of a number of aromatic nitro compounds and the composition of the solvent (moving phase) is interpreted in terms of an adsorption model.
Abstract: SummaryThe relationship between the RM values of a number of aromatic nitro compounds and the composition of the solvent (moving phase) is interpreted in terms of an adsorption model. In accordance with this model, linear RM vs. log XS plots were obtained (XS is the mole fraction of the polar solvent) in wide composition ranges, the slopes of the plots being related to the molecular mechanism of adsorption and thus to the molecular structure of the chromatographed solute. The slopes indicate one-point attachment of the samples with one polar group and predominant two-point attachment of the samples with two or more polar groups (−NO2, −NH2, −OH). As in the case of the systems investigated in the previous papers of this series, the RM vs. log XS plots tend to spread fanwise with dilution of the polar solvent (improved selectivity).
29 citations
TL;DR: In this article, a colloidal solution of graphitized carbon black (GCB) is used to precoating a glass capillary column with a stationary phase, which is then applied to the column.
Abstract: The critical factor in the preparation of glass capillary columns is the coating of the inner wall with stationary phase. Difficulty is usually met when a very polar compound has to be coated and statisfactory results are obtained only when the inside surface is roughened. Though a number of devices have been suggested, reproducible results are seldom obtained. The outstanding properties of graphitized carbon black (GCB) permit the formation of an ideal precoating of a glass capillary upon which any stationary phase can be applied. The precoating is carried out by flowing through the capillary a colloidal solution of GCB obtained by exposing a 1% solution in methylene chloride to an ultrasonic generator. A colloidal solution is obtained by means of this treatment, which after introduction into the capillary and evaporation of the solvent leaves a layer, which strongly adheres to the surface and is not even removed by washing with polar and non polar solvents. After washing the graphite surface a new stationary phase can be coated on it. A great variety of columns of different polarity can be prepared such as SP 1000, apiezon, carbowax, SE 30 and SE 52, and their characteristics are evaluated. The use of a colloidal solution prepared by ultrasonic means can be extended also to the preparation of gas solid columns.
28 citations
TL;DR: The metallised-membrane electrode was developed mainly for use in pocket-sized instruments to measure oxygen or carbon monoxide in coal-mine atmospheres as mentioned in this paper, and was used as a detector in a simple portable chromatographic system to allow both these gases to be determined.
Abstract: The metallised-membrane electrode was developed mainly for use in pocket-sized instruments to measure oxygen or carbon monoxide in coal-mine atmospheres. One version of the electrode, which can detect carbon monoxide and hydrogen in air in the ppm range, has been used as a detector in a simple portable chromatographic system to allow both these gases to be determined. The application described here is to analyse exhaled air, in order to deduce the carbon monoxide content of the blood and the hydrogen production of bacteria in the gut.
TL;DR: In this article, two kinetic mechanisms have been developed theoretically, involving the fraction of sample that is ionized in the detector, is found to be consistent with the experimental data, and they are used to detect electron capture in gas chromatography.
Abstract: Constant current electron capture detection in gas chromatography has increased the range and improved the stability of electron capture detector analysis. Systematic non-linearities of response have been seen for some compounds. Various electronic phenomena have been investigated and found not to be the cause. Two kinetic mechanisms have been developed theoretically. One of these, involving the fraction of sample that is ionized in the detector, is found to be consistent with the experimental data.
TL;DR: In this article, the separation and quantitative analysis of piperine and its isomers by HPLC on aluminum oxide is described and the influence of light (photoisomerization) on ground pepper and pepper extracts is illustrated.
Abstract: The separation and quantitative analysis of piperine and its isomers by HPLC on aluminum oxide is described. Only piperine has a strong pungent taste. The isomers of piperine occur in pepper and in pepper extracts. The influence of light (photoisomerization) on ground pepper and pepper extracts is illustrated.
TL;DR: In this article, a method of studying glass capillary coating is described; the method facilitates evaluation of coating defects, and an example of an analysis of a tobacco head space concentrate with a high resolution glass column is given and further possibilities are discussed.
Abstract: Several aspects of high resolution glass capillary columns for gas chromatography are discussed, such as different methods for improving film formation, adsorption effects, temperature stability etc. A method of studying glass capillary coating is described; the method facilitates evaluation of coating defects. An example of an analysis of a tobacco head space concentrate with a high resolution glass capillary column is given and further possibilities are discussed.
TL;DR: In this paper, the authors present a method for quantifying the separation power of a gas chromatography column using the retention index and the TZ data, which combines selectivity and separation quality in a simple and clear way.
Abstract: The separation number, TZ, is a practical measure of separation quality. TZ strongly depends on k. Sum of all TZ over the whole k-range divided by the uncorrected retention time tms of the last peak is a good measure of the separation power. The combined use of TZ and retention index data combines selectivity and separation quality in a simple and clear way. The aualitative range of a capillary column, open tubular or micro-packed, is at best expressed by the retention index range at the column temperature and is strongly dependent on the time of analysis. The acceptable temperature range of a capillary column, from far subambient to the acceptable upper limit can be simply expressed by computed data as well as the defined qualitative range. For the precalculation of both simple pocket computer programs are presented. The ‘four inlet-outlet-concept’ of gas chromatography columns (including capillaries) is discussed briefly; it offers new possibilities for analytical as well as quality check purposes, including accurate measurements of split ratios and flow rates; the tightness of the system under real life conditions can be measured by integrator, by on-line data acquisition systems as well as by hand. Sample transfer lines can simply be made as inactive as the most inactive glass capillary. This is important if we want to use the capillaries in our environment as instrument for quantitative analysis from 100 to 10−10% concentration by split or splitless injection and by capillary enrichment. Quantitative backflush and quantitative hinflush [8] or other new possibilities for capillaries, run in the four-inlet-outlet-mode, are discussed.
TL;DR: The availability of gas chromatographic detectors selective for phosphorus, sulfur, nitrogen and halogens has greatly increased the amount of qualitative information that can be gathered from an unknown sample as mentioned in this paper.
Abstract: The availability of gas chromatographic detectors selective for phosphorus, sulfur, nitrogen and halogens and the possibility of their simultaneous operation with each other or with conventional universal detectors has tremendously increased the amount of qualitative information that can be gathered from an unknown sample. Selective detectors when used simultaneously permit the calculation of percentage ratios of heteroatoms which represent additional information for qualitative identification. Combination of parallel columns with selective detectors reduces the total time needed for analysis and introduces additional information due to the different polarity of the columns.
TL;DR: Whiskers have been grown on the inner walls of glass open tubular columns and provide a means of attaining favourable phase ratios.
Abstract: Whiskers have been grown on the inner walls of glass open tubular columns and provide a means of attaining favourable phase ratios.
TL;DR: In this paper, the relative molar entropy of a solution is proportional to the molar enthalpy of solution and a variation of rotational entropy during solution, and the variation of the rotation is dependent on the geometrical structure of solute molecules.
Abstract: Some relationships between enthalpy and entropy changes on selectivities of stationary phases in GLC are derived. It is shown that the relative molar entropy of solution is proportional to the relative molar enthalpy of solution and a variation of rotational entropy during solution. Application of these relationships to systems with simple and complex solute molecules (alkylbenzenes, isoparaffins and some spherical molecules) is discussed. The variation of the rotational entropy depends on the geometrical structure of solute molecules; therefore such a parameter may be used for identification.
TL;DR: In this paper, three sequential chromatographic equipments are used at the University of Aston to separate halocarbon mixtures at feed rate up to 1 litre per hour.
Abstract: Three sequential chromatographic equipments are in operation at the University of Aston fractionating mixtures ranging from polymeric materials using continuous gel permeation techniques through to high boiling organic mixtures such as fatty acids and essential oils. This paper describes in detail the performance characteristics of one of these equipments made up of twelve columns, 61 cm long and 7.6 cm diameter that has been successfully used to separate halocarbon mixtures at feed rate up to 1 litre per hour. The experimental results obtained with the equipment have been used to substantiate some theoretical developments proposed in the paper.
TL;DR: In this paper, a methode d'etude de the repartition of a solvant de chromatographie en phase gazeuse constitue d'un compose pur entre diverses phases bi and tridimensionnelles au sein d'one support.
Abstract: Nous proposons une methode d'etude de la repartition d'un «solvant» de chromatographie en phase gazeuse constitue d'un compose pur entre diverses phases bi et tridimensionnelles au sein d'un support. Pour cela, nous etudions les variations du volume de retention d'un solute arbitraire avec la temperature dans la region du point de fusion du solvant et nous observons des transitions caracteristiques de la transformation des phases en presence. Appliquee aux paraffines normales et aux alcools gras sur des chromosorbs et des spherosils plus ou moins microporeux, cette methode permet d'acceder aux proprietes de sorption anormales des etats liquides et solides superficiels. Elle confirme, en revanche, l'absence de mouillage des supports silanises par ces composes polaires ou non. Une application numerique pour une colonne tres chargee montre qu'il est toujours dangereux d'assimiler de telles phases stationnaires a un liquide normal.
TL;DR: In this paper, the additivity principle is applied to the calculation of the enthalpic selectivity of the stationary phases in GLC, and the experimental heat of solution is divided into the energy of the intermolecular interaction and energy of hole formation.
Abstract: The additivity principle is applied to the calculation of the enthalpic selectivity of the stationary phases in GLC. The experimental heat of solution is divided into the energy of the intermolecular interaction and the energy of the hole formation. The first is calculated using the dispersion interaction indices. They have been estimated for nonpolar systems using atomic refractions, van-der-Waals radii and coefficients of intramolecular shielding. The semiempirical factors for these calculations are estimated. The energy of the hole formation is measured experimentally. The calculated and experimental heats of solution for C6−C8 isoparaffins in squalane are compared. The standard deviation of the technique for such systems is about 0.2 kcal/mole.
TL;DR: In this paper, the capacity ratio of each section for benzene was measured and the film thickness was calculated utilizing the specific retention volume of benzene as measured on a packed column with high and low evaporation rates.
Abstract: Some procedures for solvent removal from glass capillary columns when coating dynamically with stationary phase have been examined. After coating and solvent evaporation, the columns were cut into sections, and the capacity ratio of each section for benzene was measured. Values of film thickness were calculated utilizing the specific retention volume of benzene as measured on a packed column. High and low evaporation rates were examined. At low rate, some stationary phase was transported towards the end of the column. At high rate, no such transport took place, but the many secondary plugs formed during the coating made the film thinner at the start of the column. However, slow as well as rapid evaporation resulted in good columns possessing uniform films which were stable to massive solvent injection. Non-uniformity of the film caused by intermediate evaporation rates, reduced by up to 26 % the efficiency of SF-96 columns.
TL;DR: In this article, a 50 m glass-capillary column with an inner diameter of 0.33 mm was installed in a Carlo Erba Fractovap 2301 AC, equipped with FID, linear temperature programmer and automatic injection-system.
Abstract: Because of the recent progress in lipid research, the availability of an excellent separation method for fatty acid methyl esters has become more and more important. A speical need exists for a good separation of cis and trans isomers, and of isomers with different positions of double-bonds. This goal was achieved by applying a 50 m glass-capillary column with an inner diameter of 0.33 mm, installed in a Carlo Erba Fractovap 2301 AC. The GC was equipped with FID, linear temperature programmer and automatic injection-system. The main characteristics of the system were a separation number of 47 and a theoretical plate number of 227052. The reproducibility of relative retention time and of weight %, expressed as maximum percent deviation of the mean values of 10 chromatograms was 0.26% and 1.53%, respectively. Preliminary results of the quantitative analysis of free cholesterol with a short OV-17 glasscapillary column, indicate a precision better than 0.8%.
TL;DR: The Reproduzierbarkeit (als genahrte relative Standardabweichung) liegt bei ca. 1,4% as mentioned in this paper. But this is not the best of the bestimmung of Coffein with Phenacetin.
Abstract: Es wird fur die quantitative Auswertung von Dunnschicht-Chromatogrammen die Methode des internen Standards beschrieben. Am Beispiel der Bestimmung von Coffein mit Phenacetin als internem Standard wird die Methode erlautert. Das Verfahren vermeidet die Bestimmung einer Eichfunktion und erlaubt somit eine hohere Analysenzahl per DC-Platte. Die Reproduzierbarkeit (als genahrte relative Standardabweichung) liegt bei ca. 1,4%.
TL;DR: The development and current status of continous chromatography is reviewed and chromatographic separation has been practiced in laboratories and in industry for almost 30 years.
Abstract: Chromatographic separation on a continuous rather than batch basis has been practiced in laboratories and in industry for almost 30 years. The development and current status of continous chromatography is reviewed.
TL;DR: The best approach to using glass open tubular columns in routine work is the adoption of wide bore columns and on-column injection.
Abstract: The best approach to using glass open tubular columns in routine work is the adoption of wide bore columns and on-column injection. The technology involved is discussed using the analysis of urine steroids as an example.
TL;DR: In this article, an additional hydrogen treatment of graphitized thermal carbon black at 1000°C (GTCB) was undertaken to remove chemical inhomogeneity of the surface, and the peaks of oxygenated hydrocarbon derivatives became more symmetrical.
Abstract: Retention volumes (Henry constants) and differential molar change of internal energy\( - \Delta \bar U_1\) at low surface coverages on hydrogen-treated graphitized thermal carbon black (HTGTCG) for aldehydes, ketones and alcohols have been determined. An additional hydrogen treatment of graphitized thermal carbon black at 1000°C (GTCB) was undertaken to remove chemical inhomogeneity of the surface. After this treatment the peaks of oxygenated hydrocarbon derivatives became more symmetrical. Reduction of retention volumes after this treatment was observed only for substances with short hydrocarbon chains. The dependence during adsorption\( - \Delta \bar U_1\) on the structure of, and number of carbon atoms in, aldehydes, ketones and alcohols has been investigated. The Kovats' indices for the chromatography on HTGTCB were obtained and used for identification.
TL;DR: In this article, a computer program was developed for calculating the linear retention index even when some of the reference compounds are missing or the substance appears outside the range of reference compounds, and the requirement that the gas holdup time has to be measured has been overcome by using the computer to fit the data to a straight line.
Abstract: A computer program has been developed for calculating the linear retention index even when some of the reference compounds are missing or the substance appears outside the range of the reference compounds. The Kovats' index is also calculated and the requirement that the gas holdup time has to be measured has been overcome by using the computer to fit the data to a straight line. The program, written in FORTRAN, has been developed for an interactive system but could readily be adapted to any system.
BP1
TL;DR: In this article, a short historical review of the sequence of events which led up to the origination of glass capillaries, the development and performance of capillary drawing machines both of the author's design and commercially available, are discussed.
Abstract: After a short historical review of the sequence of events which led up to the origination of glass capillaries, the development and performance of capillary drawing machines both of the author's design and commercially available, are discussed. Mention is then made of the difficulties of coating capillaries with thin stable films of involatile organic liquids together with some thoughts on new methods for the surface treatment of the bore. New shapes for capillaries are suggested in terms of flat rather than the usual round columns, non uniform crinkled columns and specially shaped regular cores, which may be drawn into the tubes. Anodized alumina wire cores seem particularly attractive for this purpose. Finally, the subject of high speed gas chromatography is reviewed and an image of tomorrow's sub-picogram high speed analyser suggested.
LGC1
TL;DR: The fourth trial was designed to focus attention upon a difficult sample such as a fragment of aged paint film as mentioned in this paper, and it was shown that with strict observance of predetermined factors, the inter-laboratory reproducibility is of a high order.
Abstract: The fourth trial was designed to focus attention upon a difficult sample such as a fragment of aged paint film. It is shown that with strict observance of predetermined factors, the inter-laboratory reproducibility is of a high order. This emphasises the importance of the several lessons learnt in the course of the previous trials.