bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer comparisons of variables in capillary gas chromatography
Authors: Ingraham D. F. , Shoemaker C. F. , Jennings W.
Published: May 2005

A series of computer‐constructed van Deemter curves that permits evaluation of a number of variables in capillary gas chromatography is presented. The graphs permit the comparison of inter‐related parameters, including the choice of carrier gas (hydrogen vs helium vs nitrogen), column length (10‐100 m), column diameter (0.20, 0.25, 0.32, 0.4 mm), solute partition ratios (0‐10), and liquid phase film thickness (0.1, 0.25, 0.5, 1.0 μm). The curves are evaluated, both in terms of the relative magnitude of the optimum average linear carrier gas velocity, and in terms of the significance of the sharpness of the curve.
Oil spill identification by high‐speed HPLC
Authors: Grimalt J. , Albaigés J.
Published: May 2005

The use of high‐speed HPLC in oil spill identification problems has been evaluated in terms of analysis time and reliability. The aromatic fraction was analyzed by reverse‐phase chromatography on a 3 μm packing, with detection at 210 and 287 nm, in less than 20 minutes. The profiles exhibited by several Spanish and Middle East crude oils were differentiated by simple statistical parameters. The effect of environmental weathering on the samples has also been investigated. An Arabian light crude oil was still identifiable after four months' simulated marine weathering.
General applications of fused silica capillary column (FSCC) chromatography to the analysis of non‐priority pollutant organics in environmental samples
Authors: Hunt G. T. , Hoyt M. P.
Published: May 2005

Further applications of fused silica capillary columns (FSCC) to the analysis of environmental samples are presented. The chromatographic behavior (RT, RRT) of organic compounds of environmental significance not listed as Consent Decree Priority Pollutants is investigated on an SE‐54 FSCC. Retention indices (RRT) and mass spectral response factors (RF) are presented for a total of 28 compounds including a number of chloro‐ and nitro‐substituted anilines, alkylpyridines, and alkylquinoline derivatives. The direct application of the FSCC/MS interface to the analysis of these compounds in actual environmental samples is presented, including vent emissions from a fungicide manufacturing process, and contaminated soil and water samples from two metropolitan Boston construction sites.
Capiliary columns with immobilized stationary phases. Part 5: Determination of column bleeding; re‐silylation
Authors: Grob K. , Grob G.
Published: May 2005

The bleeding of apolar high temperature columns may well be the critical factor limiting their applicability for GC/MS‐coupling, and for high temperature analyses. Therefore, a bleeding determination procedure has been designed as a basis for a systematic approach to the production of low‐bleed columns. Re‐silylation is a traditional method of reducing column bleeding. Increased efficiency of re‐silylation becomes feasible with immoblized coatings. Experience gained so far shows that resilylation of immoblized coatings may indeed result in the expected strongly reduced bleed rates and in improved overall column quality. Re‐silylation may also contribute to column washing by enhancing the solubility of adsorbed contaminants.
A universal sample injection system for capillary column GC using a programmed temperature vaporizer (PTV)
Authors: Poy F. , Visani S. , Terrosi F.
Published: May 2005

This article describes the use of a programmed temperature vaporizer injection system which overcomes many of the classical problems associated with other injection techniques employed in capillary GC. The system can be operated in three distinct modes.
Chromatographic performance of deuterated solvents in reversed phase micro high performance liquid chromatography
Authors: Jinno K.
Published: May 2005

The chromatographic performance of the deuterated solvents, CD3OD and D2O, has been investigated in reversed‐phase micro high performance liquid chromatography. The chromatographic performance of CD3OD is only slightly superior to that of CH3OH. However, the performance of D2 is significantly superior to that of H2O, separation of aromatics being improved by about 30%. D2 is a particularly powerful solvent for the separation iof deuterated and non‐deuterated compounds.
A simple procedure for evaluating the heterogeneity parameter and the ratio of molecular sizes of solute and solvent by using HPLC data
Authors: Dawidowicz A. , Jaroniec M.
Published: May 2005

Based on the relationship defining the dependence of the capacity ratio upon the composition of the mobile phase, a simple numerical procedure is proposed for evaluating the heterogeneity parameter and the ratio of molecular sizes of solute and solvent. This procedure is examined by using HPLC data for pesticides chromatographed in isooctane/dichloromethane eluent on Lichrosorb at 291 K.
Effect of viscosity on stationary phase stability in capillary column gas chromatography
Authors: Wright B. W. , Peaden P. A. , Lee M. L.
Published: May 2005

With recent advances in column technology it is now possible to prepare highly efficient, very inert, and thermally stable capillary columns coated with nonpolar polysiloxane stationary phases. Unfortunately, the same degree of success has not been achieved for some of the more polar polysiloxane phases. A parameter that has been studied little in the past in relation to stationary phase film stability is the viscosity of the stationary phase. In this paper the efficiency and stability of coated columns are correlated to the viscosity of the phase. Due to their structure, the viscosity of the phenyl‐containing polysiloxanes change rapidly with temperature and hence, thin‐film coatings are not stable at elevated temperatures. By using high viscosity phenyl‐containing methylphenylpolysiloxanes which were recently synthesized, efficient and stable columns have been prepared.
Determination of cyclosporin A in blood and plasma by column switching‐HPLC after rapid sample preparation
Authors: Nussbaumer K. , Niederberger W. , Keller H. P.
Published: May 2005

A method for the determination of cyclosporin A in human whole blood and plasma is described which uses liquid chromatography with step gradient elution and a column switching technique. The chromatographic conditions chosen allow simple and rapid sample preparation, so that a result can be obtained within one hour. Blood and plasma are deproteinized with diluted methanol and an aliquot of the clear supernatant is directly injected. The detection limit for cyclosporin A is about 20 ng/ml starting from a 0.5 ml sample. The method is sensitive enough for monitoring the drug in the therapeutic range.
The use of chemically bonded stationary phases in thin‐layer chromatography‐a survey
Authors: Th. Brinkman U. A. , de Vries G.
Published: May 2005

An overview is given of the literature publisned in the field of thin‐layer chromatography on chemically bonded phases. Aspects which merit further attention are: quantitative analysis, organic solvent selection, stationary phase characteristics, surface modification of precoated silica plates, ion‐pair chromatography and correlation of thin‐layer and column chromatographic data.
A novel approach to the qualitative and quantitative assay of HPTLC plates: Second and fourth derivative recording of spectrophotodensitograms
Authors: Traveset J. , Such V. , Gonzalo R. , Gelpi E.
Published: May 2005

One of the limitations due to lack of resolution for a given pair of analytes in TLC or HPTLC is the need to optimize the system. In Practice this requires time, rerunning of the sample in different developing solvents, and a great deal of expertise on the part of the analyst.

In our experience, application of first and second derivative recording techniques to HPTLC facilitates and speeds the whole process, permitting qualitative and quantitative assay of most unresolved spots. Consequently, we have now extended our instrumental capabilities to fourth derivative measurements. For this purpose, we have added a homemade electronic unit in series with the one previously used for first and second order derivatives. Thus, we have been able to evaluate the potential advantages of higher order derivatives for HPTLC analysis of unresolved components in various pharmaceutical products. A comparison of second and fourth order derivative measurements of seriously overlapping HPTLC components in a sample of preservatives used in the pharmaceutical industry suggests that the lower order derivatives might be a better choice in view of the higher accuracy and precision of the corresponding data. This is supported by the results of other applications, such as the assay of a commercial colorant, and a syrup formulation. The observed lack of precision of fourth order measurements stems from the fact that although the second and higher order derivatives produce narrower bandwidths, thus contributing to improved resolution, the signal to noise ratio decreases and satellite peak interactions increase, thus rendering correct discrimination of the fine structural detail of overlapping components more difficult.
Endcapping of high performance liquid chromatography packings derived from silica gel
Authors: Dewaele C. , Mussche P. , Verzele M.
Published: May 2005

The effect of endcapping a reversed phase chromatographic packing material derived from silica gel depends on the degree of derivatization of the phase. The effect can be dramatic for phases with low loading. Whether an octadecylated silica gel has been endcapped or not can be ascertained by chromatographing the pair naphthalene/1‐nitronaphthalene with a water/methanol eluent producing at least k' ≈ 10 for naphthalene. The ratio of the two k' values is 1.4 or higher for an endcapped material, while it is only 1.1 ‐1.2 for a non‐endcapped phase. A similar approach fails to give conclusions of similar utility for octylated silica gels.
Pattern recognition for analysis of cigarette smoke by capillary gas chromatography. Part 1: Total particulate matter (TPM)
Authors: Hsu F. S. , Good B. W. , Parrish M. E. , Crews T. D.
Published: May 2005

Complex smoke profiles from fused silica capillary gas chromatography of different cigarette types produce rich information requiring computer and sophisticated statistical analysis to reveal the hidden correlation patterns. In our technique, a Cambridge pad containing total particulate matter (TPM) is extracted with Freon‐11 in a micro‐Soxhlet apparatus. The condenser is maintained at −15°C. After extraction, Freon‐11 is allowed to evaporate under mild conditions. Bis(trimethylsilyl)trifuoroacetamide (BSTFA) is subsequently added to the extract. Trimethylsilylation is completed by maintaining the reaction vessel at 60°C for two hours. A microprocessor‐controlled capillary gas chromatograph with an automatic sampler is used to generate profiles. A link to a host computer provides for transmission of profile reports and access to various statistical and graphic packages. Factor and discriminant analyses are applied to gas chromatographic data from TPM extracts because of their ability in data reduction, pattern extraction and ranking the importance of the gas chromatographic peaks. Some preliminary results from these statistical analyses are discussed.
Correlations between van der Waals volume and retention data of alkylbenzene derivatives in reversed phase micro high performance liquid chromatography
Authors: Jinno K. , Ishigaki A.
Published: May 2005

The structure‐retention relationship in reversed phase micro high performance liquid chromatography has been investigated for substituted alkylbenzene derivatives. The correlation between van der Waals volume and retention data was completely linear and any deviation from this relation might becaused from the overlap volume of substituent alkyl chains. Standard enthalpies of transfer from the mobile to the stationary phase are also proportional to the van der Waals volume of each solute; the results indicate that the mechanism of reversed phase liquid chromatography might involve a solute‐induced volume change in the mobile phase.
Concentration profiles and breakthrough curves in non‐linear chromatography
Authors: Said A. S. , Al‐Nafea M. , Al‐Ali H. , Hamad E.
Published: May 2005

The treatment of the non‐linear isotherm in chromatography by one of the authors [1] is extended to other cases of practical interest. The original paper dealt with the case of an initially thin zone resulting in a Poisson distribution the asymmetry of which is a function of the plate number and the non‐linearity constant. The present work shows that the same relations apply to initially thick zones and to the cases of washing and deposition leading to simple relations for breakthrough curves. For significantly non‐linear isotherms other quasi‐Gaussian distributions can give a better fit.
Dependence of selectivity and resolution upon composition of the binary mobile phase in LSC
Authors: Jaroniec M. , Suprynowicz‐Sieńko D.
Published: May 2005

The recently derived general equation for the capacity ratio has been utilized to study the dependence of selectivity and resolution upon mobile phase composition. This equation accounts for differences in molecular size of solutes and solvents, and for the energetic heterogeneity of the adscrbent surface. Model calculations illustrating the influence of these factors on the selectivity and resolution are presented and discussed.
Femtogram level quantitative determination of nitroglycerin and metabolites in human plasma by GC‐MS negative ion chemical ionization, single ion monitoring
Authors: Settlage J. A. , Gielsdorf W. , Jaeger H.
Published: May 2005

Recent developments in the use of negative ion detection in GC‐MS have indicated the potential for highly sensitive analyses for certain compounds. This paper describes the application of the techniques to the assay of Nitroglycerin and its metabolites yielding sensitivity to two femtograms. Because of the low levels of nitroglycerin in biological media such sensitivity is highly desirable if not essential for meaningful measurements. In addition to sensitivity the method is shown to yield extremely good selectivity contributing further to the credibility of quantitative results.
Optimization of a scanning densitometer for fluorescence detection in high performance thin‐layer chromatography
Authors: Butler H. T. , Poole C. F.
Published: May 2005

Conditions for maximizing resolution and signal‐to‐noise ratios in fluorescence scanning densitometry of separations obtained by high performance thin‐layer chromatography are described. Resolution was found to be independent of most instrument parameters with a small decrease observed at wide slit widths. Signal was found to be markedly dependent on experimental parameters such as slit width, slit height, sensitivity setting, and the time constant of electronic filters. For recording chromatograms a slit width of 1.00 mm, a slit height slightly greater than the spot diameter, a low sensitivity setting (50 mV), electronic filtering, and a scan rate of 24 or 48 mm min−1 are commensurate with minimum recording time and maximum sample detectability without incurring a significant decrease in resolution.
Preparation of reversed‐phase high‐performance thin‐layer plates by in situ reaction with monochlorosilanes
Authors: Ericsson M. , Blomberg L. G.
Published: May 2005

The condition for in situ chemical modification of commercially available thin‐layer plates have been varied and the influence thereof upon reversed phase plate properties has been studied. The reaction variables studied were: average silica pore size, silica water content, use of tri‐ or monochlorosilanes as modifiers, reaction temperature, and addition of base. Coverage and activity of residual silanol groups was studied on modified plates.

Desired plate properties are high speed of development in aqueous solvents and low content of active residual silanol groups. Under the conditions tested, the lowest amount of residual silanols was achieved at the expence of the speed of development in aqueous media and vice versa.
Purification of OV‐17 by supercritical fluid fractionation for fused silica capillary gas chromatography
Authors: Barry E. F. , Ferioli P. , Hubball J. A.
Published: May 2005

Commercially available OV‐17 was partitioned into a low and a higher molecular weight fraction by supercritical fluid extraction with carbon dioxide. This higher molecular weight fraction is more thermally stable than the original OV‐17 due to its more viscous and gum‐like nature. Based on the growing evidence in the literature that a deactivating agent for fused silica open tubular columns should be compatible with the stationary phase, a precoat of 1,3,5‐trimethyl‐1,3,5‐triphenylcyclotrisiloxane was applied prior to the static coating of high molecular weight OV‐17. Fused silica OV‐17 columns prepared in this fashion are stable up to 300°C.
Evaluation of loop and pump injection systems in preparative liquid chromatography
Authors: Gazda Krystyna , Kowalczyk Jerzy S.
Published: May 2005

The usefulness of pump or loop injectors in preparative liquid chromatography was evaluated. The concentration distribution of samples flowing through a UV detector cell, directly connected to the injector, was recorded at various flow velocities, at various diameters of loop tubing, and using various methods of injection [injection with sample volumes equal to a fraction or total loop volume, etc.]. The most advantageous methods were found to be either use of a loop injector to inject only a fraction of its total volume or use of a pump. Both of these methods ensure a almost rectangular concentration distribution.
Quantitative determination of low concentrations of DHETX m. s. in human plasma by high performance liquid chromatography with fluorescence detection
Authors: Žorž M. , Marušič A. , Smerkolj R. , Prošek M.
Published: May 2005

A method is described for separation of low amounts of DHETX m. s. from human plasma, based on extraction and determination by high performance liquid chromatography with fluorimetric detection.
On‐column infrared monitoring for reversed phase liquid chromatography with deuterated solvents
Authors: Fujimoto Chuzo , Jinno Kiyokatsu
Published: May 2005

Infrared monitoring was accomplished in reversed phase HPLC on using deuterated solvents. The end of a micro HPLC column was flattend and used as a flow cell for on‐column IR detection. Detection of alkylbenzenes and oil‐soluble vitamins which were separeted on ODS packing with CD3CN/D2O and CD3OD, respectively, was performed at 2940 cm−1.
Improved quantitative capillary GC by the use of CO2 as secondary coolant in cold on‐column injection
Authors: Ogden M. W. , McNair H. M.
Published: May 2005

A comparison is made between air and carbon dioxide as secondary cooling gases in cold on‐column injection into capillary columns. Because CO2 is a more effective coolant than air, the injection zone can be kept at a colder temperature, thus preventing loss of sample vapor through the open injector even as the initial oven temperatures because greater than the boiling point of the solvent. Sample loss at these elevated temperatures is shown as a reduction in peak area as functions of column temperature during injection and different injection zone temperatures. The maximum allowable oven temperature during injection is significantly higher when CO2 is used as secondary coolant rather than air.
Reversed‐phase high‐performance thin‐layer chromatography of mono‐, di‐ and trisubstituted bile acid methyl esters
Authors: Iida T. , Yamauchi C. , Chang F. C.
Published: May 2005

A comparative study is reported on separation of series of mono‐, di‐, and trisubstituted methyl 5β‐cholanates, which differ only in the position and stereochemistry of hydroxyl or keto groups at position and stereochemistry of hydroxyl or keto groups at positions C‐3, C‐7, and/or C‐12, by reversed‐phase [with chemically‐bonded (C‐18) silica gel] and normal‐phase (silica gel) high‐performance thin‐layer chromatography (HPTLC). Methnol (or acetonitrile)/water systems were employed as mobile phase. Reversed‐phase HPTLC found to be particulary effective for separation of the stereoisomers of di‐ and trisubstituted compounds whereas the less polar monosubstituted isomers are well resolved in normal‐phase HPTLC.
A micro‐volume electron capture detector for use in high resolution capillary column gas chromatography
Authors: Wells G.
Published: May 2005

A new design for an electron capture detector cell is described. The cell is compatible with the requirements of high resolution capillary columns and is shown to be useful in applications that require high analysis speed. A unique method of sample introduction reduces the problems of sample loss by adsorption on the surfaces of the cell. Previously reported problems of sample loss by adsorption on active surfaces within the cell when using hydrogen carrier gas are shown to have been eliminated. Examples are shown demonstrating the increased speed of analysis that can be obtained when using hydrogen carrier gas and 100 micron diameter columns.
Determination of biogenic quaternary ammonium compounds on fused silica capillary columns with a splitless injector as a chemical reactor/pyrolysis chamber
Authors: Findeis P. M. , Farwell S. O.
Published: May 2005

A conventional splitless injector is used as a pyrolysis chamber or chemical reactor for the N‐demethylation of acetylcholine and other choline esters. The novel uses of 2‐aminoethanol as a N‐demethylation reagent in splitless injection and bonded‐phase fused silica capillary columns in the separation of the tertiary amine derivatives of choline esters are described. A comparison is made between non‐polar and moderately polar fused silica capillary columns in the separation of choline esters.
GC/MS analysis of chlorinated paraffins with negative ion chemical ionization
Authors: Müller Markus D. , Schmid Peter P.
Published: May 2005

Although chlorinated paraffins (CP) are produced in large amounts (300 000 tonnes per year), little is known about their occurrence in the environment due to the lack of specific and sensitive analytical methods. The present paper describes the GC/MS analysis of different CP's using capillary gas chromatography with on‐column injection and negative ion chemical ionization (NCI) mass spectrometry. Chromatographic resolution of groups of isomers and homologues was obtained. The chromatograms and mass spectra are discussed. The suitability of this method for trace analysis of a CP sample using multiple ion detection (MID) is described.
Analysis of volatile organic compounds in polymers by dynamic headspace and gas chromatography/mass spectrometry
Authors: Jacobsson Sven
Published: May 2005

An experimental method for the analysis of volatile organic compounds in polymers is described. The technique involves dynamic headspace sampling, collection, and concentration of the volatiles in a cold trap, followed by capillary column gas chromatography/mass spectometry. Flow switching is carried out by the Deans switching technique. Four technical polymers used as pharmaceutical packaging materials have been analyzed in order to demonstrate the method.
Large sample injection method (≥ 100 μL) for capillary GC using a commercial thermodesorption unit as injection device
Authors: Kirschmer P. , Oehme M.
Published: May 2005

A commercial thermodesorption and cold trap unit can be used as a large sample volume injection device in high resolution gas chromatography. Volumes of more than 100 μl can be injected. More than 97% of solvents, such as hexane, can be removed by a Tenax TA precolumn without any loss of compounds with volatilities comparable to naphthalene. Experimental conditions, recovery rates of polycyclic aromatic hydrocarbons, and the reproducibility of the method are described in detail. The method was successfully applied for the determination of PAH in air particulate matter extracts.
Direct gas chromatographic analysis of halogenated hydrocarbons at the part‐per‐trillion level
Authors: Zlatkis A. , Ghaoui L. , Wang F.‐S. , Shanfield H.
Published: May 2005

Large sample volume on‐column injection (up to 250 μL) of n‐pentane solutions of halogenated hydrocarbons has been employed for the direct measurement of both low‐boiling and high‐boiling compounds in what is essentially a single run. Two‐bonded phase, fused‐silica capillary columns are joined in series, through which the low‐boiling compounds are first chromatographed and detected with an electron capture detector. High‐boiling compounds are then trapped in a section joining the two columns, and subsequently chromatographed in the second column, using the same detector. This procedure permits analysis at the ppt level.
A miniature gradient elution system for liquid chromatography with packed capillary columns
Authors: Karlsson K.‐E. , Novotny M.
Published: May 2005

A miniaturized continuous gradient elution system was designed for work with packed capillary columns. The retention reproducibility achieved is adequate for many practical applications.
Characterization of OV‐1/FFAP‐mixture coated glass capillary columns used for the separation of free fatty acids
Authors: Pörschmann J. , Welsch T. , Engewald W. , Vigh Gy.
Published: May 2005

As an alternative to acid pretreated UCON and FFAP capillaries for the analysis of wide‐boiling free fatty acid mixtures, OV‐1 : FFAP phase mixtures were used on high‐temperature silylated inert glass capillary columns. The HETP‐carrier gas velocity curves, peak asymmetry factors, coating efficiency, gas phase and stationary phase contributions to the mass transfer resistance were determined for various OV‐1 : FFAP ratios. Mixed‐phase capillaries showed optimum performance at a 2 : 1 OV‐1 : FFAP ratio. The thermal and long‐term stability of OV‐1‐stabilized FFAP columns surpassed those of the UCON and pure FFAP reference column used.
ODS phases for ion chromatography
Authors: Cooke M.
Published: May 2005

Several ODS phases have been dynamically modified to act as ion exchangers. Their ability to separate inorganic ions has been evaluated. The different properties of these materials are demonstrated and a method for eliminating the appearance of the system peak is described.
Determination of 1‐nitropyrene by thin‐layer chromatography in a diesel exhaust particulate extract
Authors: Brown K. K. , Poole C. F.
Published: May 2005

A method is described for the determination of 1‐nitropyrene in a diesel exhaust particulate extract by thin‐layer chromatography. 1‐Nitropyrene is determined as 1‐aminopyrene after prechromatographic reduction and isolation by solvent partition. The fluorescence response of 1‐aminopyrene is approximately 1000‐fold greater than that of 1‐nitropyrene. The poor fluorescence stability of 1‐aminopyrene on silica gel plates prevents in situ detection by scanning densitometry unless the plates are impregnated with a mixture of 2,6‐di‐tert‐butyl‐4‐methylphenol and Fomblin H‐Vac. A linear response from 1 to 150 ng of 1‐aminopyrene and a detection limit of 1.0 ng were obtained using the impregnated plates. For fourteen samples of a diesel exhaust particulate extract the concentration of 1‐nitropyrene was determined to be 165 μg/g with an RSD = 9.0%. No significant interferences were observed from other nitro‐ or aminopolycyclic aromatic compounds present in the extract.
Optimization of retention time of aromatic acids in liquid chromatography from log P and predicted pKa values
Authors: Hanai T. , Hubert J.
Published: May 2005

For optimization of liquid chromatography separations, several approaches have been reported, among them the use of the hydrophobic fragmental constant, as proposed by Rekker [1]. The fragmental constant is derived from the partition coefficients of various solutes between octanol and water and represents a summation of solubility parameters: van der Waals volume, π ‐ π interactions, hydrogen bonding, etc. With these constants the optimization of reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing was feasible, although large error was found for the eluent with a high concentration of organic modifier or water. This is probably due to the heterogeneous solvation of the surface of the packings and to various solvent effects. In addition, when the acid dissociation constant was known, the retention times of aromatic acids in the ionic form were also predicted using the hydrophobic fragmental constant and the dissociation constant. By comparison of the previous data and a method proposed by Perrin et al. [2] it was possible to predict the dissociation constant of aromatic acids and optimize separation in reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing. Furthermore, an equation for calculating the capacity ratios in a given pH eluent was proposed and the predicted and observed capacity ratios of aromatic acids in several eluents were examined in order to improve the above system.
Determination of tetraiodothyronine in serum by HPLC and electrochemical detection
Authors: Besenfelder E.
Published: May 2005

Tetraiodo‐L‐thyronine (T4) in human serum was determined by HPLC using a nonphysiological internal standard. For sample preparation, a cation exchange resin, RP‐chromatography on C‐18 or phenylphase, and electrochemical detection (Metrohm 656 or BAS‐LC 4 A) were employed. The mobile phase (0.8 ml/min) was 10 mM H3PO4/CH3OH (40/60 v/v) or 10 mM H3PO4/CH3CN (70/30 v/v, 1.5 ml/min), the voltage applied 800 mV. The coefficient of variation (day to day) was 6.8% (N = 40); concentrations of T4 found were 11 to 20% lower than those obtained by two different commercially available immunoassays.
Analysis of dust and surface swab samples for octachlorodibenzo‐p‐dioxin and heptachlorodibenzo‐p‐dioxins by fused silica capillary GC with EC detection
Authors: Korfmacher W. A. , Rushing L. G. , Nestorick D. M. , Thompson H. C. , Mitchum R. K. , Kominsky J. R.
Published: May 2005

A method is described for the analysis of contaminated building dust samples and surface swab samples for octachlorodibenzo‐p‐dioxin (OCDD) and heptachlorodibenzo‐p‐dioxins (HpCDDs). The samples were analyzed by fused silica capillary GC combined with electron capture detection. Analysis was preceded by a short HPLC cleanup step designed to remove polychlorinated biphenyls (PCBs) and other compounds that might interfere. The method was found to work successfully on surface swab and dust samples known to contain PCBs, OCDD, and HpCDDs. The overall recovery of the analysis procedure for OCDD was found to be approximately 80%. The detection limit for the method was sample dependent, but for one typical set of surface swab samples was 0.2 μg/m2 of OCDD.
Preparative HPLC. Part 2. Purification of β‐lactam derivatives using laboratory‐assembled equipment
Authors: Matlin S. A. , Chan L.
Published: May 2005

The capabilities of a preparative chromatograph assembled at moderate cost from commercially available components are examined in relation to the purification of β‐lactam derivatives. It is shown that high efficiency separations can be achieved rapidly, economically, and on a scale sufficient to provide adequate quantities of material for spectroscopic identification and biological testing. In the synthesis of a large batch of aminopropyl silica for preparative HPLC purification of an impure sample of cephacetrile, three different grades of silica were investigated. The material giving the best performance was prepared on a 100 g scale and baseline separations for 0.5 g loadings of the impure cephacetrile were obtained on a 30 cm × 2.2 cm i.d. column. The pure cephalosporin was recovered in high yield by freeze drying of the eluate.
Determination of metabolites relating to the tryptophan‐NAD pathway in rat urine by cellulose high performance thin‐layer chromatography
Authors: Yamada M. , Minami Y. , Yuyama S. , Suzuki T.
Published: May 2005

High performance thin‐layer chromatography (HPTLC) was used to determine 12 metabolites of the tryptophan‐NAD pathway in rat urine. The method of separation described in the previous report was improved. The metabolites were separated on the cellulose plate by using five multiple developments with four solvent systems. The plate was scanned by the TLC scanner at 254 nm and the amounts of the metabolites were calculated by comparing peak areas of the scanning curves obtained for the urine sample and for the authentic standards. This procedure can be used as a semiquantitative determination method for the metabolites in biological fluids.
Sequential centrifugal layer chromatography (SCLC): A New technique for the isolation of natural compounds. Part 1: Description of the method and practical aspects
Authors: Nyiredy Sz. , Erdelmeier C. A. J. , Sticher O.
Published: May 2005

Sequential centrifugal layer chromatography (SCLC), a new preparative planar separation technique, combines the advantages of preparative centrifugal layer chromatography (CLC) and analytical, horizontal, anticircular, and sequential thin‐layer chromatography (TLC). In this on‐line preparative method, solvent delivery is locally and temporally variable, which means that the mobile phase can be brought onto the plate at any desired place.

The SCLC apparatus operates in two modes: circular, with the help of centrifugal force in an inclined position, and anticircular, by means of capillary action in a horizontal position. These two operation modes can be combined and repeated as often as required, hence the separation space becomes practically unlimited. In this way the capacity and separation performance is significantly increased.

In the present paper the apparatus and the method are described and some practical aspects are mentioned.
Quantitative HPTLC analysis of carboxylic acids in wine and juice
Authors: Lin L. , Tanner H.
Published: May 2005

The need for quick and specific assay of carboxylic acids in wine and non‐fermented beverages is explained. The method developed in this work is based on high performance thin‐layer chromatography (HPTLC) followed by densitometric evaluation. Untreated samples, with the exception of red wines which were destained, were directly sprayed onto the cellulose layer. The chromatogram was developed with ethyl acetate‐toluene‐water‐formic acid 60:20:20:15, then stained with xylose‐aniline reagent. Densitometric scanning is by absorbance at 546 nm. The method is quick, sensitive, and has a wide dynamic range for the acids analyzed.
Sequential centrifugal layer chromatography (SCLC): A new technique for the isolation of natural compounds. Part 2: Comparative study on centrifugal layer chromatography (CLC) and SCLC for the separation of furocoumarin isomers
Authors: Erdelmeier C. A. J. , Nyiredy Sz. , Sticher O.
Published: May 2005

The new sequential centrifugal layer chromatography extends the possibilities for preparative separation of furocoumarin isomers. In the present work, isobergapten, pimpinellin, bergapten, isopimpinellin, and sphondin were isolated from a prepurified extract of Heracleum sphondylium roots using two different techniques, namely, centrifugal layer chromatography (CLC) and sequential centrifugal layer chromatography (SCLC). The former technique was carried out with four plates, whereas the latter method required only one plate, using the same mobile phase in each case. A further advantage of the SCLC method was that all completely separated compounds could be quickly and efficiently eluted in small volumes of mehtanol.
Inorganic and organic mercury analysis by HPTLC and in situ densitometric detection. Application to real samples
Authors: Bruno P. , Caselli M. , Traini A.
Published: May 2005

Inorganic mercury and some organo‐mercury species have been separated as dithizonates by HPTLC and determined in situ at the subnanogram level by densitometric automatic scanning of the plate. The extraction efficiency of the dithizonates was tested at pH 1, 7, and 10. The Rf values for HgD, CH3HgD, C2H5HgD, and C6H5HgD are 0.15, 0.32, 0.35, and 0.28 respectively. The recovery of the tested mercury species in simulated and real samples has been investigated. Conditioning of the plates with NH3 prior to elution eliminates interference by many other metal ions. Some examples of real sample analysis (tap water, sea water, human urine) are reported.
Pneumatic pulse dampener for liquid chromatography
Authors: Gupta P. K. , Nikelly J. G.
Published: May 2005

A simple pulse dampener is described for use with reciprocating pumps. The dampener may be assembled locally form readily available components and consists mainly of a small reservoir of compressed helium which acts as a cushion to dampen the mobile phase pulsations pneumatically. Depulsing is 99% complete and is uniform through a wide pressure range. The pneumatic dampener allows the use of single‐ piston reciprocating pumps in conjunction with highly flow‐sensitive detectors at their highest sensitivity settings.
Non‐aqueous ion exchange chromatography, an alternative to buffered silica gel
Authors: Rüedi P.
Published: May 2005

A method is described for the HPLC separation of moderately acidic, dehydrated, and multi‐oxygenated diterpenoids, compounds which hitherto could not be handled by HPLC. It is based on chemically bonded silica strong cation exchangers in the protonated form, using organic solvents of the full polarity range as eluents. Thus a stable and easy‐to‐regenerate substitute for buffered silica gel is obtained.
Cold trap/reinjection interface for two‐dimensional gas chromatography
Authors: Hagman A. , Jacobsson S.
Published: May 2005

The construction and evaluation of an interface for two‐dimensional gas chromatography is described. The interface consists of commercially available components and is attachable to available gas chromatographs without any major modifications. The interface has been constructed so as to permit “heartcutting” as well as solute band concentration. Trapping is performed in a simple cold trap of fused silica. Flow switching is accomplished by Deans switching. Factors of the over‐all chromatographic performance are examined.
Multidimensional separation of isomeric species of chlorinated hydrocarbons such as PCB, PCDD, and PCDF
Authors: Schomburg G. , Husmann H. , Hübinger E.
Published: May 2005

A multidimensional GC‐system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n‐alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set‐up, the live‐switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference‐free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so‐called “linear” indices.
Total steroid profiling with capillary GC. Details on sample preparation
Authors: Vanluchene E. , Vandekerckhove D.
Published: May 2005

The accuracy and reproducibility of steroid and steroid conjugate determinations using capillary GC are evaluated. It is possible to analyze many unconjugated steroids, steroid sulfates, and some steroid glucuronides simultaneously, simply by using group fractionation based on successive hydrolysis and solvent extraction steps. However, a reliable determination of corticosteroid glucuronides can only be obtained after previous isolation of the glucuronides as a group, with ion exchange chromatography. In complex chromatograms, the combined use of nitrogen specific detection and flame ionization detection facilitates peak identification.
FABES and FAPES – transesterification of triglycerides with higher alcohols. Quantitation and mass spectrometric evaluation
Authors: Traitler H. , Richli U. , Winter H. , Kappeler A. M. , Monnard C.
Published: May 2005

In order to facilitate the gas chromatographic determination of butyric as well as other short chain fatty acids, triglycerides containing these fatty acids were transbutylated and transpentylated to give FABES (fatty acid butyl esters) and FAPES (fatty acid pentyl esters), respectively. This method allows the molecular weight of the compounds to be increased while their polarity is decreased. Short chain esters elute sufficiently separated from the solvent; due to the decreased polarity, elution of long chain fatty acids is only slightly retarded compared to the corresponding methyl esters. Quantitative evaluation over a large series of injections proved the linearity of correction factors in both cases, FABES and FAPES, with a slight deviation for 16:0 and 18:0, respectively. Structural characterization was performed by GC/MS. It was shown that there are characterstic fragmentations for FABES as well as for FAPES. The El‐mass spectra give structural information about the alcohol and acid moieties, the ester molecule and the Cl‐spectra indicate the molecular weight. The absence of abundant highly characteristic peaks in the spectra of these esters makes the detection of FABES or FAPES in complex mixtures more difficult than the detection of FAMES with their very characteristic ions at m/z 74 and 87.
Analysis of chemically modified polystyrenes with pyrolysis‐capillary gas chromatography
Authors: Venema A. , Sukkel J. T.
Published: May 2005

Pyrolysis‐capillary GC has been applied to the analysis of chemically derivatized polystyrenes. The reproducibility of the method and the influence of instrumentation has been discussed.
Analysis of polycyclic aromatic compounds in the fly ash of an incineration plant for radioactive waste
Authors: Tausch H. , Stehlik G.
Published: May 2005

Organic compounds adsorbed on fly ash from an incinerator for radioactive waste were investigated. Following Soxhlet extraction and concentration, analysis was performed by GC and GC/MS using high temperature silylated glass capillary columns coated with OV‐1 and SE‐54. Compound identification was based on retention data, relative detector responses, and mass spectra. Among other polycyclic aromatic compounds, series of gradually chlorinated PAHs containing four to seven aromatic rings were detected. For unequivocal identification, appropriate reference compounds were synthesized by chlorination of the corresponding parent PAHs.
Capillary supercritical fluid chromatography with simultaneous flame ionization and mass spectrometric detection
Authors: Holzer G. , Deluca S. , Voorhees K. J.
Published: May 2005

A simple interface between a capillary supercritical fluid chromatograph and an Extranuclear Simulscan mass spectrometer is described. The SFC column is directly inserted into the ion source through the existing GC‐interface. The system is equipped with a splitting device which allows simultaneous EI/MS and flame ionization detection when CO2 is used as the supercritical phase. The effect of source temperature and pressure on CO2 clustering was studied for optimization of source conditions. The performance of the system was evaluated with a series of model compounds and standard mixtures.
Capillary gas chromatography and mass spectrometry detection of anabolic steroids II
Authors: Cartoni G. P. , Giarrusso A. , Ciardi M. , Rosati F.
Published: May 2005

High resolution gas chromatography‐mass spectrometry has been used to detect anabolic steroids in urine. With fused silica capillary columns connected directly to mass spectrometer, the anabolic steroids could be detected after extraction, hydrolysis, and derivatization with a sensitivity better then 1 ppb. In vivo excretion and metabolism has been investigated for androstanolone, methandriol, oxymesterone, quindenione, and boldenone.
Conditions for accurate split injection of samples with wide boiling point range
Authors: Eyem J.
Published: May 2005

The effect of injection temperature, carrier gas flow rate, geometry of the glass insert, and column temperature program on the precision and accuracy of split injections was measured. Three types of injection techniques were compared: injection into a hot isothermal injector, isothermal injection with the injector at the solvent boiling point temperature, and programmed injection temperature. The last of these techniques produced the best accuracy and precision of analysis. Conditions for complete sample trapping at the beginning of programmed temperature analysis are described.
Optimization of selectivity using sequentially coupled capillary columns
Authors: Mayfield H. T. , Chesler S. N.
Published: May 2005

This investigation lays groundwork for the development of an optimization system for sequentially coupled capillary column systems. Three methods for calculating effective capacity factors were obtained from the literature and were tested to determine suitability for optimization use, using four test analytes and two dissimilar columns. This work concentrates on the development of a method for the estimation of optimum column temperatures in sequentially coupled systems.
Applications of a miniaturized fluorimetric photodiode array detector for capillary liquid chromatography
Authors: Gluckman J. C. , Novotny M.
Published: May 2005

A high sensitivity, multichannel fluorescence detector with small volume has been developed for capillary column liquid chromatography. Using an intensified linear photodiode array to monitor fluorescence emission, several important mixtures exhibiting native fluorescence have been examined following high efficiency separation on a capillary column. By correlating mass spectral, fluorescence spectral, and retention time data, information of potential utility in the structural elucidation of aromatic molecules contained in complex mixtures can be obtained. Examples include the separation and spectral examination of the polyaromatic compounds in samples of both biological and environmental interest.
Selectivity and selectivity tuning in capillary gas chromatography
Authors: Sandra P. , David F. , Proot M. , Diricks G. , Verstappe M. , Verzele M.
Published: May 2005

The selection of stationary phases in capillary gas chromatography is discussed. Methyl silicone, phenyl methyl silicone, trifluoropropylmethyl silicone, biscyanopropyl silicone, and high molecular weight (HMW) polyethylene glycol are considered to be the basic phases. Selectivities and polarities between these phases are obtained by selectivity tuning. Selectivity tuning can be performed in three different ways, namely by synthesizing a tuned stationary phase, by mixing the basic phases, or by coupling capillary columns of different selectivities. In coupling capillary columns the variables are column length, β‐value, temperature, and/or pressure.
On‐line multidimensional chromatography using supercritical carbon dioxide
Authors: Christensen R. G.
Published: May 2005

A two‐dimensional chromatographic separation is described which makes use of the unusual properties of supercritical carbon dioxide mobile phase. This solvent has the property of giving a separation of polycyclic aromatic hydrocarbons (PAH) on amine‐bonded columns similar to that given by usual normal‐phase solvents, and on octadecylsilane‐bonded columns similar to that given by usual reversed‐phase solvents.

Packed columns were used, arranged so that they could be switched in or out of the solvent flow. Polycyclic aromatic hydrocarbon mixtures isolated from coal tar were fractionated according to number of aromatic carbon atoms on an amine‐bonded column, and these fractions were trapped on an octadecysilane‐bonded column. They were subsequently eluted according to the polarity of the individual compounds. Separations from fractions containing 16 and 18 aromatic carbon atoms are shown.