bluuebunny/crossref_metadata_2025 huggingface dataset:
Apatite coated on organic polymers by biomimetic process: Improvement in its adhesion to substrate by NaOH treatment
Authors: Tanahashi Masami , Yao Takeshi , Kokubo Tadashi , Minoda Masahiko , Miyamoto Takeaki , Nakamura Takashi , Yamamuro Takao
Published: May 2005

A dense, uniform and highly biologically active bone‐like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure. First, a substrate is set in contact with particles of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyl‐eneterephthalate (PET), polymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone (PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed by the hydrolysis of an ester group on PET and PMMA and of an amide group on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, attached a large number of hydrated silica dissolved from the glass particles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite‐organic polymer composites thus obtained are expected to be useful as bone‐repairing as well as soft tissue‐repairing materials. © 1994 John Wiley & Sons, Inc.
Improved sensitivity and decreased sample size in a cytotoxicity test for biomaterials: A modified colony microassay using a microplate and crystal violet staining
Authors: Tsuchiya Toshie , Ikarashi Yoshiaki , Arai Tadashi , Ohhashi Jyunichi , Nakamura Akitada
Published: May 2005

Modified Eagle's minimum essential medium supplemented with 5% fetal calf serum was highly sensitive to cytotoxicity and formed large control colonies in the V79 colony assay. A highly sensitive cytotoxicity test was developed using 96‐well microtiter plates. Test chemicals or extracts of polyurethane materials containing the same chemicals were added 24 h after inoculation of cell suspensions. The cells were fixed and stained with crystal violet after additional culture for 6 days (V79 cells) or 10 days (Balb/3T3 cells). In terms of sensitivity and rapid quantitative measurement, this modified colony microassay, using a low cell density in 96‐well microplates, was superior to various cytotxicity tests such as colony, growth inhibition, cytolethality, and agar diffusion assays. © 1994 John Wiley & Sons, Inc.
Effectiveness of cleaning surgical implants: Quantitative analysis of contaminant removal
Authors: Rowland Shane A. , Shalaby Shalaby W. , Latour Robert A. , Von Recum Andreas F.
Published: May 2005

Surgical implants need to be free from contaminants before implantation. The effectiveness of a presently used Clemson bioengineering cleaning (CBC) protocol was evaluated for cleaning three different biomaterials (titanium, aluminum oxide, and polyethylene terephthalate, PET) contaminated with three different contaminants (calcium chloride, zinc chloride, and hexadecane). Radiolabeled tracer analysis (RTA), with the use of liquid scintillation, was used as the surface analytical technique to quantitatively determine the removed from the biomaterial surface. On average, the ultrasonic cleaning step removed 99.96% of all three contaminants from both titanium and aluminum oxide. The CBC protocol did not sufficiently clean PET fabric contaminated with hexadecane leaving 11.76% of the contaminant after the ultrasonic step. With the use of isopropyl alcohol in series with 1% Liquinox, the ultrasonic step cleaned the fabric soiled with hexadecane within 30 min, removing 99.85% of the hexadecane initially on the surface. RTA proved to be an excellent method of quantifying surface contamination on implant materials, and for assessing the effectiveness of cleaning protocols in question. © 1995 John Wiley & Sons, Inc.
A quantitative technique for reporting surface degradation patterns of UHMWPE components of retrieved total knee replacements
Authors: Cornwall G. Bryan , Bryant J. Tim , Hansson Carolyn M. , Rudan John , Kennedy Lloyd A. , Cooke T. Derek V.
Published: May 2005

A quantitative method of reporting surface degradation of the ultra‐high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow‐up visits enhanced the assessment of the retrieved TKR. © 1995 John Wiley & Sons, Inc.
In vitro cytotoxicity testing of neodymium‐iron‐boron magnets
Authors: Donohue V. E. , McDonald Fraser , Evans R.
Published: May 2005

Neodymium‐iron‐boron magnets are being increasingly used in orthodontic and orthopedic appliances. The purpose of this study was to investigate the in vitro cytotoxicity of these new “super” magnets. A modified agar overlay technique was performed using both L929 mouse fibroblasts and adult human oral mucosal fibroblasts. The neodyium‐iron‐boron magnets were tested in the following forms: uncoated magnetized, uncoated demagnetized, parylene coated demagnetized, and parylene coated magnetized. Results revealed that uncoated magnetized, uncoated demagnetized, and parylene coated magnetized were cytotoxic to both L929 mouse fibroblasts and human oral mucosal fibroblasts. However the parylene coated demagnetized neodymium magnets were only cytotoxic to the human mucosal fibroblasts. This study supports the hypothesis that these are cytotoxic effects of possibly corrosion products and of magnetism. The specific toxic effects of parylene were not examined in this present study. Statistical analysis (Mann‐Whitney U‐test, p = 0.014) suggested that, in this experiment, the human oral mucosal fibroblasts were more sensitive to the effects of these rare earth magnets. With the evidence of a biological effect, the use of implanted magnets must at present be limited until the safety can be assured. © 1995 John Wiley & Sons, Inc.
The response of cancellous and cortical canine bone to hydroxylapatite‐coated and uncoated titanium rods
Authors: Rashmir‐Raven A. M. , Richardson D. C. , Aberman H. M. , De Young D. J.
Published: May 2005

Because of the recent trend in total hip arthroplasty to achieve direct contact of the endoprosthesis with cortical bone, comparison of bone apposition from cortical bone and cancellous bone was performed. The response of cortical and cancellous bone to hydroxylapatite was also compared. Implants in cortical bone demonstrated a higher interface shear strength and more bone apposition than those in cancellous bone over all time periods tested. Hydroxylapatite coating increased the interfacial shear and bone apposition in cortical bone at all time periods and in both the 3‐ and 6‐week cancellous bone models. The potential effect of stress shielding (and subsequent bone resorption) by femoral stems ingrown with cortical bone is discussed. © 1995 John Wiley & Sons, Inc.
Modification of polyethylene terephthalate (dacron) via denier reduction: Effects on material tensile strength, weight, and protein binding capabilities
Authors: Phaneuf Matthew D. , Quist William C. , Bide Martin J. , LoGerfo Frank W.
Published: May 2005

Thrombosis remains a significant and potentially catastrophic complication of polyethylene terephthalate (Dacron) prosthetic vascular graft implantation. Numerous attempts have been made to create a novel surface that reduces the adverse effects of blood interaction with the material. The purpose of this study was to create reactive groups on Dacron without significantly altering the chemical and physical properties of the biomaterial. These groups would then serve as “anchor sites” for covalent attachment of the blood protein albumin to the surface, thus creating a more biocompatible surface. Denier reduction, an established textile chemistry procedure that creates carboxyl groups on the fiber surface via hydrolysis of the material, was performed at 100°C using sodium hydroxide concentrations of 0.5, 1.0, 2.5, and 5.0% (treated materials referred to as 0.5% hydrolyzed etc.). Tensile strength determination of hydrolyzed materials revealed no statistically significant difference in material strength between control, 0.5, and 1.0% hydrolyzed materials; the 2.5 and 5.0% hydrolyzed materials had significant strength loss as compared to the controls. Significant fiber weight loss occurred in the 1.0, 2.5, and 5.0% hydrolyzed Dacron segments. The 0.5% hydrolyzed material did not have any significant weight loss. Covalent linkage of 125I‐albumin to these modified materials using the crosslinker 1‐ethyl‐3‐(3‐dimethyl aminopropyl)‐carbodiimide hydrochloride (EDC) resulted in the 0.5% hydrolyzed material having the greatest protein binding (330 ng/mg Dacron, 2.4‐fold greater than control). Incubation of the 0.5% hydrolyzed material with EDC and various concentrations of 125I‐albumin resulted in the 14.80 m̈M solution permitting the greatest binding per milligram Dacron (330 ng/mg Dacron). Scanning electron microscopy, performed blindly, revealed no change in the 0.5% hydrolyzed Dacron as compared to untreated Dacron. The 5.0% hydrolyzed Dacron, however, had noticeable structural damage on the outer periphery of the fiber surface. Observation of the untreated Dacron with nonspecifically bound albumin showed scattered areas of albumin adherent to the fiber surface whereas covalent linkage of albumin to the 0.5% hydrolyzed Dacron via EDC crosslinking showed numerous albumin moieties on each fiber. This study demonstrates that a clinically accepted biomaterial (Dacron) can be chemically modified, without significantly altering the physical and chemical characteristics of the biomaterial, in order to covalently bind albumin to the fiber surface. Thus, these results serve as foundation for creating potential novel biomaterials without significantly altering the properties of the original biomaterial. © 1995 John Wiley & Sons, Inc.
Determination of volatile halogenated hydrocarbons in tap water, seawater and industrial effluents by glass capillary gas chromatography and electron capture detection
Authors: Eklund Göran , Josefsson Björn , Roos Claes
Published: May 2005

A rapid and sensitive method to determine volatile organohalides in different types of waters has been developed. The chromatographic system is based on the resolving power of the glass capillary column and the high sensitivity of the electron capture detector. The capillary columns were connected to the detector so that the eluate from the column is mixed with thermostatted purge gas to minimize band broadening due to dead volumes. The low column bleeding and decreased band spreading from capillary columns enhance the sensitivity to very low levels: 1 fg (10−15g) for carbon tetrachloride, despite dilution of the column eluate by the purge gas.

The water samples of 100 ml were extracted with 1 to 10 ml n‐pentane which is the most practical alkane with respect to purity. When using high water to pentane ratios corrections had to be made, due to low extraction yield, to get accurate quantifications.

A column with Carbowax 400 stationary phase permits direct tap water injection. The water peak concealed the substances eluated after CHCl3 and CHBrCl2.

The gas chromatographic separation of haloforms in tap water could be shortened to 30 seconds using a 10 m SE–52 column with an increased film thickness.

Besides tap water and seawater, industrial waste water from a pulp mill was analyzed. Ten different halogenated organic compounds, ranging from 1 ng/I to 760 μg/I, were quantified in the different waters. Bromoform, which had not previously been found in seawater, was detected.

Chromatogram of a standard mixture containing 11 organohalides. Stationary phase, SE‐52; 33 m × 0.3 mm i.d. inj. temp. 200°, column temp. 50°, interface 250°, detector temp. 250°. Helium carrier gas flow rate, 36 cm/s, scavenger'gas flow 30 ml/min.

Split ratio 1:20, 1 = CH2CI2, 2 = CHC13, 3 = CH3CC13, 4 = CC14, 5 = CHCICCI2, 6 = CHBrCI2, 7 = CBrC13, 8 = CHBr2Cl, 9 = CCl2CC12, 10 = CHCl2l, 11 = CHBr3.
Capillary gas‐liquid chromatography of bile acids: Improvement with on‐column injection
Authors: Kariaganis Georg , Paumgartner Gustav
Published: May 2005

Analysis of trimethylsilylethers of methyl esters of bile acids exhibits high separation efficiency with a 20 m × 0.3 mm glass capillary column covered with a crystal layer of barium carbonate and coated with polyethyleneglycol 20000 as liquid phase [3]. The sensitivity and reproducibility of this method can be further improved by an on‐column injection technique according to Grob et al. [4].
Splitless injection and the solvent effect
Authors: Grob K. , Grob K.
Published: May 2005

Splitless injection is based on the solvent effect as a mechanism condensing large vapour clouds down to infinitely shortened bands. The effect is controlled by the parameters column temperature, volatility and amount of solvent, and rate of injection. By properly selecting the variables the effect can easily be optimized for any combination of sample and column. It is the purpose of this paper to provide the mechanistic understanding as required for this optimization, as well as some rules for the experimental realization. Potentialities and limitations of splitless injection are discussed, and the role of the solvent effect in on‐column injection is emphasized.
GC/MS investigations of the constituents in a diethyl ether extract of an acidified roast coffee infusion
Authors: Rahn W. , König W. A.
Published: May 2005

A roast coffee infusion (nicaragua arabica) was acidified (pH 1,5) with hydrochloric acid and extracted with diethyl ether in a perforator. After evaporation of the solvent the residue was treated with N‐methyl‐N‐trimethylsilyl trifluoroacetamide and analyzed by glass capillary GC/MS. The main components were identified by their electron impact and isobutane chemical ionization mass spectra. 1,2,4‐trihydroxy benzene, 1‐ethyl‐3, 4‐dihydroxy benzene and 2,3‐dihydroxy toluene were identified as new constituents of roast coffee with possible emetic properties.
Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 1. Evaluation by graphic methods
Authors: Ebel S. , Hocke J.
Published: May 2005

The paper discusses errors and error propagation in respect of graphic methods in quantitative in situ measurements in TLC. An error of 0.3% is possible by measuring only peak height if optimal conditions are chosen. This is in good agreement with analysis done practically which gives errors in the order of 0.3–0.6%. If the peak area is evaluated using the approximation peak height × half width, the error is in the order of 0.6%, but in real experiments only 1.5% had been found. Systematic errors in determining peak heights are introduced by the time constant of the amplifiers and the recorder.
GLC studies of diffusion of some selected solvents in polypropylene and the calculation of the activation energy of diffusion
Authors: Abushihada A. M. , Shunbo F. E. , Al‐Sultan Y. Y.
Published: May 2005

A thorough survey of the past and current available literature shows that the diffusion of the solvents toluene, ethylbenzene, ortho‐, meta‐, and para‐xylenes in polypropylene has not been studied so far, although such studies find practical applications in various industrial problems. Diffusitives and the activation energies of the above mentioned solvents in polypropylene were determined in the temperature range of 45–120°C by gas chromatography. The values obtained in this communication compare fairly with those determined by conventional techniques for analogous systems, confirming the reliability of the gas chromatography as a powerful tool for diffusion measurement and the authenticity of the data presented herein.
The absolute retention index in chromatography. Part 1
Authors: Said A. S. , Hussein F. H.
Published: May 2005

A definition for an absolute retention index is given. This index is independent of whether the process is isothermal or temperature programmed. The relation between this index and Kovats's index is discussed. General equations are derived for the retention times of homologous series, from which the position of the air peak or missing members can be determined. Methods used in the literature for air peak determination are improved and extended to other cases of interest. The retention index in temperature programmed chromatography is reexamined in the light of recent publications on temperature programming.
Simultaneous determination of acidic, basic and alcoholic substances relating to monoamine hormones and metabolites in biological material by mass fragmentography (GC/MF)
Authors: Kobelt Reinhard , Wiesener Günther
Published: May 2005

A method is described for the simultaneous quantitative determination of monoamines and related compounds from urine and brain tissue samples in the pg‐range, using a GC/MF instrument LKB‐2091 provided with a multiple ion detection (MID) system and capillary columns. The simultaneous detection of “fingerprints” with fourteen and more compounds during one single GC run was achieved after the intoduction of “time gates” for the detection of the different characteristic masses. Several modifications to the LKB equipment permitted exact reproducibility of retention times, which is essential for the use of “time gates”. The detection of “fingerprints” with these acidic, basic and alcoholic substances was achieved by the extraction of the dried biological samples with silylating agents.
Separation of nebramycin components by ion‐exchange thin‐layer chromatography
Authors: Pauncz Judit Kádár
Published: May 2005

A thin‐layer chromatographic method on chromatoplates coated with Dowex 50 × 8 ion‐exchange resin, suitable for the separation of 5 nebramycin components, was developed.
An HPLC fluorescence detection system for amines
Authors: Frei R. W. , Lawrence J. F. , Th. Brinkman U. A. , Honigberg I.
Published: May 2005

A detection system is described which is based on fluorescent ion‐pair formation between tertiary amine drugs and dimethoxyanthracene sulphonate. A dynamic micro‐extraction principle is then used to isolate the ion‐pairs from the excess reagent. The band broadening of this extraction detector was kept below 20% using standard auto‐analyser equipment. With the enhanced selectivity and sensitivity of this approach it was possible to analyse chloropheniramine in urine at ppb concentrations using a pre‐column clean‐up trace enrichment step.
Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 3. The determination of the primary statistical errors
Authors: Ebel S. , Glaser E.
Published: May 2005

The paper describes the measurement and calculation of the primary statistical errors in the evaluation of TLC or HPTLC using in situ reflectance measurements. The primary errors are the errors of the sample volume spotted onto the plate, errors caused by the chromatographic process itself, the positioning error of the plate with respect to the centre of the light beam and the error in the light measurement. By scanning the same spot, the same track or the same plate under different conditions, the various errors can be determined.
Preparation of wall‐coated open tubular columns after surface roughening by means of amorphous silica
Authors: Badings H. T. , Van der Pol J. J. G. , Wassink J. G.
Published: May 2005

A new method for the preparation of wall‐coated glass capillary columns after surface roughening by means of amorphous silica is described. After the glass capillary has been leached, a small quantity of amorphous silica is deposited evenly on the inner surface. This is done by passing a plug of dilute water glass through the capillary, followed by a flow of gaseous hydrochloric acid. The roughened surface is stabilized, deactivated and finally coated.

This paper furnishes details of the technique and information about the performance of a number of columns prepared by the method.
Are we using the full resolving power of capillary GC?
Authors: Neu H. J. , Zinburg R.
Published: May 2005

Precise evaluation of the chromatographic data by means of the relative retention will allow the full use of the resolution achieved by capillary columns. In practice, retention‐index determination is best suited for this purpose. The reproducibility of retention‐index determination strongly depends, among other factors, on the accuracy of retention time measurement. A reproducibility of ±0,05 i.u. can be easily achieved with modern gas chromatographic equipment, provided the retention times can be measured with an accuracy of at least ±0.01%. This can be shown by error propagation analysis of retention‐index calculation performed with the aid of a programmable pocket calculator.
Glass capillary gas chromatography of amino acid enantiomers
Authors: Nicholson Graeme J. , Frank Hartmut , Bayer Ernst
Published: May 2005

Glass capillaries coated with Chirasil‐Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino‐acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable.
Practical limitations of capillary gas chromatography
Authors: Schomburg G.
Published: May 2005

Glass capillary gas chromatography is a high resolution separation method which allows the qualitative and quantitative analysis of even complex mixtures, which may contain many components–also isomeric–in a wide range of volatilities, polarities and concentrations.

The principal limitation of gas chromatographic application is given by an insufficient volatility of the species to be separated. Elevated temperatures have to be applied if the application range is to be extended and to achieve steep peak profiles, i.e. low detection limits at high resolution. The use of elevated temperatures is limited, of course, by the temperature stability of both the solvent (stationary liquid and support) and the solutes.

The problems of trace analysis for low volatility compounds at high resolution and its limitational parameters regarding sampling, separation and detection are discussed.

The applicability of glass capillary columns in this field is influenced by the following parameters: tailing behaviour; irreversible adsorption of polar and decomposition of unstable solutes; thermal stability of stationary liquid (including the support deactivation); separation efficiency and sample capacity (film thickness).

Multidimensional gas chromatography using capillary columns coupled either with a packed or another capilllary column for preseparations may be applied with advantage in the analysis of complex mixtures.
Effects of the porous structure of particles on selectivity in liquid chromatographic systems
Authors: Kowalczyk J. S. , Gazda K. , Herbut G.
Published: May 2005

The effects produced in liquid‐solid chromatography by the heterogeneity of adsorbent particles on the behaviour of a number of substances were studied. As adsorbent silica gels were used which varied

In specific surface area and pore size,

In the diameter of particles of the same microporous structure.

A second series of experiments was conducted at various temperatures.

The dependences which were based on measurements of equivalent retention volumes were found to deviate somewhat from those theoretically predicted. However, they confirm and supplement some previous observations [l–5] according to which mass transport may be effected by only a portion of the packing particles if their porous structure is adequately heterogeneous. These observations are in contrast with views expressed by some authors [6, 7] who maintain that differences in mass transport resistance may only result in peak deformation.

It has also been demonstrated that the effects of the heterogeneity of particle structure in liquid chromatographic systems can be reduced by increasing the temperature.
Determination of dichloroacetic acid in plasma and urine
Authors: Heizmann P. , Von Alten R.
Published: May 2005

A method for the measurement of dichloroacetic acid in plasma or urine has been developed. The method involves extraction of dichloroacetic acid into diethyl ether, evaporation of the etheric phase to a small volume and derivatization with diazomethane. Trichloroacetic acid was used as an internal standard. Concentrations as low as 50 ng/ml can be determined.
High performance liquid chromatographic resolution of the optical isomers of D,L‐tryptophane, D,L‐5‐hydroxytryptophan and D,L‐dopa on cellulose columns
Authors: Gübitz G. , Jellenz W. , Schönleber D.
Published: May 2005

The application of HPLC for the purpose of separation of some amino acid racemates with aromatic substituents is described.

Using simple untreated cellulose with an average particle size of 7 μm as stationary phase, complete resolution of D,L‐tryptophane and D,L‐5‐hydroxytryptophane can be obtained. D,L‐3,4‐dihydroxyphenylalanine is resolved partially.

The α‐value and resolution for D,L‐tryptophane was found to be 1.5.
Effect of test temperature on separation number
Authors: Jennings Walter , Yabumoto Kan
Published: May 2005

The separation number is affected by a variety of extra‐column factors (e.g. the injection process, the nature of the sample, and plumbing defects in the inlet and detector) as well as factors related to column efficiency. The magnitude of the separation number, as affected by the column, varies inversely with column temperature and directly with the partition ratios of the test compounds. The interrelationships of column temperature and partition ratios are explored.
HPLC of fatty acid esters of mono‐ and polyhydric alcohols. Part 2: Preparative separation
Authors: Henke H. , Dietrich W.
Published: May 2005

This paper demonstrates how simply and rapidly fatty acid esters of mono‐ and polyhydric alcohols can be separated quantitatively in preparative quantities on Lobar® RP‐8 packed columns. After the separation of unknown mixtures, the isolated esters are identified from spectroscopic data (IR/NMR) and, after saponification of the ester components (fatty acids and alcohols), from the retention times of gas and high‐pressure liquid chromatographic separations. Thus, in particular, sparingly volatile or nonvolatile partial esters of polyhydric alcohols, as well as the long‐chained full esters, can be determined qualitatively and quantitatively.

The following fatty acid esters of mono‐ and polyhydric alcohols have been separated: the i‐propylesters of the laurinic and myristinic acids, the i‐butyl‐, i‐octyl‐ and i‐octadecyl‐esters of the palmitinic and stearic acids, the mono‐ and di‐fatty acid esters of the 1,3‐bis‐(2‐hydroxyethyl)‐5,5‐dimethylhydantoins, the mono‐, di‐ and tri‐esters of the trimethylalpropane and the full esters of the pentaerythrite.
Influence of chamber saturation in thin‐layer chromatography on theoretical and experimental parameters of mixture separations
Authors: Różyło J. K. , Ościk‐Mendyk B.
Published: May 2005

The influence of chamber saturation in thin‐layer chromatography on theoretical and experimental parameters of mixture separations were examined. Five different types of chambers for development of chromatograms were taken into consideration. The relation found experimentally differed widely from that calculated using Ościk's equation for different method of carrying out of the chromatographic process. The investigations presented here show the possibility of choosing chromatographic chambers which are optimum for theoretical studies on the process of thin‐layer chromatography.
Analysis of drugs and related compounds by capillary column GLC
Authors: Vandenheuvel W. J. A. , Zweig J. S.
Published: May 2005

This article describes the development of the application of capillary column GLC methods to steroids, prostaglandins and especially drugs and their metabolites in samples of biological origin. The wide variety – in terms of structures and pharmacological properties – of drugs now analyzed by capillary column GLC is made evident. Reasons for use of capillary rather than packed columns are given. The frequent use of and need for derivatization procedures prior to chromatography is emphasized. A bibliography of 83 references is included in the manuscript.
Chromatogram surgery
Authors: Janssens G.
Published: May 2005

A computer program is developed on a Hewlett‐Packard 3354 B Laboratory Automation System to eliminate background in gas and liquid chromatograms. Moreover undesired peaks, such as solvent peaks and spikes, can be excluded by selecting appropriate method parameters or by application of the integrator‐timed events directly affecting peak integration. Injudicious application of these codes deforms the chromatograms. Peaks can be labelled with retention times, areas or amounts.
Determination of adsorption by fluorescence in gas chromatography
Authors: Driessen O. , Lugtenberg J.
Published: May 2005

PMBF2, a pyrromethene pigment, can be used in gas chromatography. Because of its fluorescence, adsorption sites on glass columns and connections can be traced in situ. The compound can be employed to check the inertness of glass surfaces after deactivation procedures. Some applications are described.
Volatile phase profiling of mainstream smoke by glass capillary gas‐chromatographic techniques
Authors: Good B. W. , Parrish M. E. , Douglas D. R.
Published: May 2005

A heated injection system for a microprocessor‐controlled GC has been developed for the (GC)2 analysis of the volatile phase of whole smoke of a cigarette. Effects of injection port temperature and the presence of a Cambridge filter pad are demonstrated. Chromatograms are shown for smoke samples with and without a Cambridge Filter with the sample valve oven at 25°, 165° and 205°C. The use of a flame ionization and a nitrogen‐phosphorous detector is illustrated.
Evolution and application of the fused silica column
Authors: Jennings Walter
Published: May 2005

Fused silica is an evolutionary product of continuing efforts to improve our chromatographic capabilities. It offers the normal user new horizons in inertness, chromatographic reproducibility, ease of column installation, and possibilities in on‐column trapping. Since this writing, chemically bonded phases in several film thicknesses became available on fused silica columns, and these are especially well suited to on‐column injections. The use of fused silica syringe needles to inject directly onto fused silica columns seems particularly interesting. Evolution is, of course, a continuous process and it would appear that we can expect continuing developments in this exciting area.
The theoretical basis of column chromatography in multicomponent separations. Part 2: Peak capacity. Column systems with good selectivity
Authors: Peichang Lu , Xiuzhen Li , Yukuei Zhang
Published: May 2005

The selectivity of a column system, S, defined by equation 28, includes a variation coefficient (β) of plate number with capacity ratio which has a large influence on the peak capacity, as shown in Fig. 18. Some typical chromatograms are given. In order to predict S for a column system from Kovat's Index, equations 40 and 41 are given to calculate the constant of the carbon number rule for squalane at different temperatures or for different stationary phases. The specific retention value of heptane on squalane at different temperatures can be calculated from equation 42. The nonpolarity index, defined by equation 43, was used to calculate the retention value of heptane on various stationary phases. In liquid chromatography, the order of elution may be reversed by changing the composition of the eluent on the same chemically bonded silica (manufactured in China). The linear relations between the log retention values of different kinds of solutes or of a single solute on the silicas of different surface areas when using the same eluent are given.
Day‐dream on process and laboratory gas chromatography
Authors: Guillemin C. L.
Published: May 2005

Three main problems have to be solved in process gas chromatography: psychological, technical and economic.

A simple concept already used with success for fifteen years by the author, called the Deferred Standard, is an answer for process GC and, to some extent, laboratory GC as well.

That the injection of a pure compound in each analytical sequence is reproducible demonstrates the good working order of PGC. Accurate quantitative results may be obtained because the gas density balance is used as a calibrator detector for determining the relative response factors of the components of interest with respect to the Deferred Standard.

By suppressing any calibration standards in process and laboratory chromatography, the Deferred Standard may reveal itself as a time and money saving technique.
Evaluation of syringe handling techniques for injections into vaporizing GC injectors
Authors: Grob K. , Rennhard S.
Published: May 2005

Unequal elution of sample components of different volatility out of the syringe needle is one of the major causes for discrimination occuring during the injection, i.e. the phenomena which results in peak areas for the high boiling compounds which are too small compared with the volatiles. This problem, associated with all vaporizing injectors that are used with syringes, can be minimized by careful choice of the needle handling technique. Various methods are compared experimentally. The “solvent flush” method is discussed in detail and demonstrated to be ineffective for reducing losses in the syringe needle. The “hot needle” technique, where the empty needle is preheated in the injector before pushing the plunger, was found to be superior or equal to an improved “solvent flush” method (which included preheating the needle and omitting the air plug between sample and flushing solvent. Generally it was found that the discrimination due to the syringe needle was reduced for larger sample volumes, although no further changes were noticed when these exceeded 2.5 to 3μl.
Simultaneous analysis of all five organic priority pollutant fractions
Authors: Trussell A. R. , Moncur J. G. , Lieu Fong‐Yi , Leong L. Y. C.
Published: May 2005

Acrolein, acrylonitrile, volatile organics, base/neutral extractables, acid extractables, and pesticide fraction organics are analyzed in a single chromatographic run. This is accomplished by injecting the extractable organics, then applying a cryogenic focus to the front of the column, and desorbing the volatile components. The column utilized for this procedure is a fused silica open tubular (FSOT) column coated with the liquid phase SE‐54. Minimum detection limits of this procedure by electron impact GC/MS are shown to be⩽ 1 μg/liter in tests conducted on actual water samples.
Glass wool in the inserts of split injectors for capillary GC?
Authors: Grob K. , Neukom H. P. , Hilling P.
Published: May 2005

It has been reported that glass wool packed tightly into the glass liner of a vaporizing injector used in the splitting mode considerably reduces the standard deviation of the results obtained, because of improved evaporation of the sample prior to reaching the split point at the capillary column entrance. This finding could not be reproduced on using the same sample composition as reported in the literature, i.e. methanol/2‐ethyl‐1‐hexanol (1:1).

The standard deviations obtained were between 3 and 10% (depending on the conditions selected) and were not influenced significantly by the introduction of glass wool.

The peak area ratio (methanol/2‐ethyl‐1‐hexanol) was found to depend on a number of parameters, such as: injector temperature; glass liner internal diameter; syringe handling technique; the relative position of the syringe needle exit and capillary column entrance; the sample volume injected; and the packing of the glass liner. Generally, the area ratio deviated further from the correct one (determined by cold on‐column sampling) when the glass liner was packed with glass wool.

On the basis of the results, it is speculated that either a complete evaporation of the sample should be achieved (which appears to be impossible under the conditions we used) or, alternatively, the sample should be given the least possible opportunity to evaporate, thus allowing it to enter the column in the form of droplets. The results were worse in terms of precision and accuracy the greater the partition of sample components between the liquid (droplet) and vapor phase. It is concluded that the use of evaporation aids such as glass wool cannot be generally recommended.
Separation of digitalis cardenolides by HPLC
Authors: Linley P. A. , Mohamed A. G. M.
Published: May 2005

The separation of Digitalis cardenolides has been carried out by HPLC on an adsorbent column. By choice of suitable mobile phase, isocratic elution permitted resolution of mixtures of (a) aglycones, (b) secondary glycosides, and (c) primary glycosides, while gradient elution provided a means of resolving more complex mixtures of these cardiac steroids. HPLC could therefore be used in the quality control of cardiotonic drugs replacing the TLC tests for related compounds currently used, and by suitable calibration could replace the colorimetric assay procedure normally used for such drugs.
Influence of structure and polarity of polysiloxanes on retention of N‐TFA butyl esters of amino acids
Authors: Boudah Fawzia , Abdeddaim Khélifa , Guermouche Moulay‐Hassane
Published: May 2005

In this work, we have investigated the influence of the polarities and structures of 13 polysiloxanes on the retention of some N‐TFA N‐butyl esters of amino acids. Gehrke [1] was the first to examine the possible relationship between polarity and retention data of amino acid derivatives for 9 stationary liquid phases. He concluded that the molecular structure of the stationary liquid phase is an important factor determining retention.
Application of ion‐exchange resin coated plates for thin‐layer chromatography of sulfonamides and some other chemotherapeutic compounds
Authors: Pauncz Judit Kádár
Published: May 2005

A thin‐layer chromatographic method is described for sulfonamides and some other chemotherapeutic compounds. Ion‐exchange resin precoated plates (Fixion 50 × 8 Na+, Chinoin, Budapest or Polygram Ionex‐25 SA‐Na, Macherey‐Nagel and Co.,Düren, FRG) are employed with Na2HPO4 or Na‐acetate (adjusted to different pH values) containing NaCl and tert‐butyl alcohol or ethanol as developing solvent system. For qualitative and/or semiquantitave determinations the chromatograms can be stained: (A) with o‐tolidine, after chlorination; (B) with p‐dimethylaminobenzaldehyde; (C) with p‐dimethylaminocinnamaldehyde.
High speed liquid chromatography with small bore columns
Authors: Xiuzhen Li , Guimin Zhou , Miansheng Bao , Yukui Zhang , Peichang Lu
Published: May 2005

Using a specially designed column system, we have systematically investigated the effect of mobile phase velocity on column efficiency. The performance of small bore columns operated at different linear velocities of mobile phase was examined for three different types of injection system. Using the value of H∞/u or n∞/t as a criterion of a high speed separation, we calculated values of n/t for different solutes according to the equation \documentclass{article}\pagestyle{empty}\begin{document}$ {{\rm n}\mathord{\left/ {\vphantom {{\rm n} {{\rm t}_{\rm r}^ \circ }}}\right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }} = {{{\rm n}^\infty } \mathord{\left/ {\vphantom {{{\rm n}^\infty } {{\rm t}_{\rm r}^ \circ }}} \right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }}\left({\frac{{1 + {\rm k'}}}{{{\rm k' + }\beta }}} \right)^2 $\end{document}; the results obtained are in agreement with the experimentally determined values. These systematic investigations culminated in the separation of seven compounds in less than 10 s; the respective chromatogram is shown.
High performance liquid chromatography/video fluorometry. Part II: Applications
Authors: Shelly D. C. , Fogarty M. P. , Warner I. M.
Published: May 2005

A video fluorometer is used as a detector for HPLC to characterize highly complex samples. Data selection and evaluation techniques are discussed so as to speed the spectral identification process. Several well‐known polynuclear aromatic hydrocarbons are found in the samples.
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

The 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

Among 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

The 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

Isocratic 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

It 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

A 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.