bluuebunny/crossref_metadata_2025 huggingface dataset:
Verification of nonproduction of chemical warfare agents: I. Determination of organophosphorus compounds by microcolumn liquid chromatography with flame photometric or thermionic detection
Authors: Kientz Charles E. , Verweij Albert , De Jong Gerhardus J. , Th. Brinkman Udo A.
Published: May 2005

Microcolumn liquid chromatography (micro‐LC) with on‐line flame photometric (FPD) or thermionic detection (TID) has been used for the determination of a series of organophosphoric and organophosphonic acids isolated from various sample matrices. Silica‐based ion‐exchange materials and polymer packings have been used as stationary phases. In order to improve the sensitivity (expressed in concentration units) of the technique, trace enrichment via a miniaturized precolumn (4 mm × 1 mm i.d.) and direct large‐volume injections (1–10 μL) of aqueous samples have been studied. As an application, the verification of nonproduction of chemical warfare agents and their alleged use have been investigated by analyzing their hydrolysis products in spiked surface water and soil samples. The application of both the precolumn technique and large‐volume injections permit the detection of organophosphorus acids in water and soil at the low ppm level.
Verification of nonproduction of chemical warfare agents: II. Large volume injections in microcolumn liquid chromatography using flame photometric detection
Authors: Kientz Charles E. , Verweij Albert , De Jong Gerhardus J. , Th. Brinkman Udo A.
Published: May 2005

The sensitivity and separation performance of microcolumn liquid chromatography coupled with a flame photometric detector were considerably improved by the direct injection of large sample volumes (approximately 10 μL) and by peak compression. Extremely narrow peaks can be obtained by adding displacers such as hydrochloric acid (ion‐exchange mode) or n‐butanol (reversed‐phase mode) to the sample.

The system was used for the determination of ethyl methylphosphonic acid, isopropyl methylphosphonic acid, and pinacolyl methylphosphonic acid which are the hydrolysis products of the super‐lethal nerve agents VX, sarin, and soman, respectively, and of the final degradation product, methylphosphonic acid. The detection limits for the alkyl methylphosphonic acids and sarin in water were 1–20 ppb.

Two examples were used to demonstrate the practicality of the present procedure. Sarin and the much more polar isopropyl methylphosphonic acid were simultaneously determined in a spiked surface water sample used for verification studies. Low‐ppb levels of phosphorous acid were identified in mustard gas.
Purification of proteins and peptides for sequence analysis using microcolumn liquid chromatography
Authors: Moritz Robert L. , Simpson Richard J.
Published: May 2005

Reversed phase microcolumn (0.32 mm i.d.) liquid chromatography was used to purify low‐picomole amounts of proteins and peptides suitable for structural analysis. Using this approach, rapid trace enrichment (concentration) of low nanogram levels of proteins from volumes as high as 500 μL down to 1–2 μL was demonstrated. The total system recovery (including manual collection and reinjection) for 50 ng of lysozyme was >95%; the overall recovery after five injections was 90%. Using the same packing, Brownlee RP‐300, the resolution of a standard mixture of proteins was comparable for columns varying in length from 250 mm to 10mm. Identification by amino acid sequence analysis of selected peptides recovered from a sub‐10 pmol Staphylococcus aureus V8 protease digest of recombinant murine interleukin‐6 (IL‐6) was achieved.
Immobilized metal affinity chromatography with fused silica microcolumns
Authors: Flurer Cheryl L. , Novotny Milos
Published: May 2005

Fused silica capillaries of 250 μm i.d. were slurry‐packed with a TSK Chelate‐5PW stationary phase. Cu(II) was immobilized on the iminodiacetate surface, and proteins were separated using either an increasing imidazole gradient or a decreasing pH gradient. The microcolumn system increases detection sensitivity without affecting chromatographic behavior. The possible use of this system in the study of tertiary structure relationships between related proteins is explored.
Measurement of thermodynamic quantities of micellar solubilization by micellar electrokinetic chromatography with sodium dodecyl sulfate
Authors: Terabe Shigeru , Katsura Takehisa , Okada Yukihirao , Ishihama Yasushi , Otsuka Koji
Published: May 2005

Micellar electrokinetic chromatography (MEKC) allows the calculation of distribution coefficients between a micelle and the surrounding aqueous phase from the measurement of the migration time, provided the critical micelle concentration (CMC) and the phase ratio are known. Thermodynamic quantities such as enthalpy and entropy changes of micellar solubilization were calculated from the temperature dependence of the distribution coefficients. Sodium dodecyl sulfate (SDS) was employed to prepare a micellar solution and its CMCs and partial specific volumes at different temperatures were measured. The relationship between the molecular structures of solutaes and the resulting thermodynamic quantities was investigated. The temperature inside the capillary was calculated from the temperature dependence of the distribution coefficient.
Diluted versus undiluted cyclodextrin derivates in capillary gas chromatography and the effect of linear carrier gas velocity, column temperature, and length on enantiomer separation
Authors: Hardt Ingo , König Wilfried A.
Published: May 2005

The effect of dilution of the chiral stationary phase octakis (3‐O‐butyryl‐2, 6‐di‐O‐pentyl)‐γ‐cyclodextrin in the achiral polysiloxane OV–1701 on the separation factor was investigated over a wide concentration range. The loss in enantioselectivity was only negligible down to a dilution of 50% (w/w), since the separation factor vs. concentration curves levels off at higher concentrations. Because of the strong temperature dependence of the separation factors, the properties of short columns (10 m and 4.5 m) were evaluated. These short columns, which allow operation at low temperatures and lead to enhanced separation factors were found to be appropriate for the separations of simple mixtures, because the gain in selectivity exceeded the loss in separation efficiency. For complex mixtures, the higher efficiencies of columns of at least 25 m in length were still necessary. A plot of In α vs. 1/T did not yield straight lines, but showed a significant curvature, leading to considerable relative errors if thermodynamic data were derived from these plots.
Simple method for the preparation of highly efficient polymer‐coated capillary electrophoresis columns
Authors: Malik Abdul , Zhao Zhongxi , Lee Milton L.
Published: May 2005

A simple method for the preparation of polymer‐coated fused silica capillary columns for electrophoresis is presented. It is shown that the static coating technique used in GC and SFC can be conveniently utilized for the preparation of highly efficient capillary electrophoresis columns. In this method, the coating solution contains appropriate proportions of three ingredients: a polymer, a surface derivatization reagent, and a crosslinking reagent dissolved in a suitable low‐boiling solvent. After coating, the column is subjected to heat treatment to immobilize the polymer film. Simplicity, rapidity, high column efficiency, batch‐to‐batch and run‐to‐run reproducibility, and long column life‐time are advantageous features of the new method. Column efficiencies of as high as 1.2 million theoretical plates were achieved for cytochrome c on a 96 cm long Ucon 75 H‐90,000 coated column. Efficient electrophoretic separation of five cytochrome c proteins was achieved on a Superox 4 coated column. The possibility of CE separation of histones on the new columns was also explored.
Systematic optimization of capillary electrophoretic separations using the overlapping resolution mapping scheme
Authors: Ng Choon Lan , Ong Chye Peng , Lee Hian Kee , Li Sam Fong Yau
Published: May 2005

In this study, the use of a systematic optimization scheme for capillary electrophoretic separations is described. This scheme utilizes the overlapping resolution mapping procedure to predict the optimum separation conditions for the separation of two groups of compounds, a group of seven flavonoids and a group of eight sulfonamides. The chosen parameters that affect the separation depend on the compounds in question. In the case of flavonoids, pH and SDS concentrations were chosen as the parameters for optimization, whereas in the case of sulfonamides, pH and β‐cyclodextrin concentrations were used. As few as nine experiments are required to achieve optimum conditions for the separation of all peaks. To confirm the validity of the optimization procedure, additional experiments chosen from the predicted optimum conditions were performed. The results show that satisfactory separation could be achieved by using the optimum conditions predicted by the scheme. All flavonoid and sulfonamide peaks were satisfactorily separated in about 30 and 8 min, respectively.
Use of a sheath flow cuvette for chemiluminescence detection of isoluminol thiocarbamyl‐amino acids separated by capillary electrophoresis
Authors: Zhao Jian‐Ying , Labbe Jill , Dovichi Norman J.
Published: May 2005

A post‐column reactor was designed for chemiluminescence detection in the capillary electrophoresis separation of isoluminol thiocarbamyl derivatives of amino acids. This system was characterized with respect to hydrogen peroxide concentration and flow rate, surfactant concentration, microperoxidase concentration, and mixing distance. A linear calibration curve (R >0.999) was constructed for isoluminol ranging from at least 30 femtomoles to the detection limit of 40 attomoles injected; the dynamic range of the instrument is at least three orders of magnitude. Detection limit for the isoluminol thiocarbamyl derivative of valine was 500 attomoles. The theoretical plate counts for the raw data are typically 1 × 105 for labeled amino acids, and a factor of two better for isoluminol.
Novel detection schemes for the trace analysis of amino acids and peptides using capillary electrophoresis
Authors: Sweedler Jonathan V. , Fuller Robert , Timperman Scott Tracht Aaron , Toma Verna , Khatib Karim
Published: May 2005

The ability of the cellular biochemist to understand events occurring in small subsections of an individual cell depends on available analytical techniques. Two unique capillary electrophoresis (CE) detection schemes for trace level peptide analysis are characterized: an on‐line, multichannel, laser‐induced fluorescence system and a post‐column radionuclide system. The fluorescence system has picomolar concentration detection limits (and zeptomole mass limits of detection) for tagged amino acids and peptides. Preliminary results are presented for a method to enhance the ability to fluorescently tag low concentrations of amino acids and peptides from neuronal subsections. The procedure takes advantage of the high local concentration of peptides within a synaptic vesicle to enhance the derivatization reaction. The other detection method described involves a post‐column35S detector to examine methionine or cysteine containing peptides. This system deposits the effluent from the separation capillary onto a membrane treated with a solid scintillator. After drying the membrane, the photon emission is imaged with a solid‐state integrating detector. The sensitivity for 35S labeled components is in the attomole range.
High‐speed GC/MS using narrow‐bore columns and ion trap detection
Authors: van Ysacker Peter G. , Janssen Hans‐Gerd M. , Snijders Henri M. J. , Leclercq Piet A. , Cramers Carel A. , van Cruchten Huub J. M.
Published: May 2005

Fast gas chromatographic separations can be achieved by vacuum‐outlet operation and by applying narrow‐bore columns. In this work, the combination of 50 μm i.d. columns with ion trap mass spectrometric detection is evaluated. Detection limits in the electron ionization mode, and in the chemical ionization mode using CH4 as the reaction gas, are 1 pg and 5 pg, respectively. Owing to the high sensitivity of the ion trap mass spectrometer, a significant improvement in the working range in comparison with other detection systems is obtained. The small column flows cause no loss of mass spectral resolution and sensitivity. The performance of the system is demonstrated by the analysis of some real‐world samples.
Electrophoretic focusing in a natural steady state moving pH gradient
Authors: Šlais Karel
Published: May 2005

The physical and mathematical basic of a natural steady state, moving pH gradient is outlined. With certain approximations, a differential equation of the concentration of the component contributing to the natural steady state, moving pH gradient is formulated. Solutions of the differential equation and the relationships to the resolution calculations of both carriers and trace components present in the large excesses of carriers are presented. The steady state distribution profiles of both amphoteric and nonamphoteric components predict Gaussian distributions only if and when the conductivity and the pH gradient remain constant within the moving focused zone. The practical significance of the model is shown by its application to isoelectric focusing (IEF) with electrophoretic mobilization, to isotachophoresis (ITP) with polyampholytic spacers, and to related methods. It is shown that the presented approximate model represents the transition between classical models of IEF and ITP.
Evaluation of solvent venting with a gas purge for the introduction of microliter sample volumes in supercritical fluid chromatography
Authors: Berg Bjørn E. , Hansen Ellen M. , Flaaten Anne M. , Greibrokk Tyge
Published: May 2005

Peak broadening and sample recovery are important considerations when working with large sample volume injections in capillary SFC. To measure possible contribution to peak broadening in the venting valve, a tee coupling was inserted between the retention gap and the column. A standard sample containing glyceryl esters was injected. Based on time variance measurements, the venting valve did not lead to measurable band broadening. Recovery was found to be dependent on the length of the retention gap, the CO2/He ratio in the purge gas, and the temperature of the retention gap. Cryofocusing was needed to increase the recoveries of volatile n‐alkanes. To increase the recoveries of glyceryl esters, an enhanced CO2/He ratio was needed.
Importance of molecular shape in supercritical fluid chromatography using a porous glassy carbon adsorbent stationary phase
Authors: Larkins William C. , Olesik Susan V.
Published: May 2005

The effect of a solute's shape on retention using porous glassy carbon (PGC) as a stationary phase in supercritical fluid chromatography (SFC) is described. A series of stilbene and stilbene‐like molecules that have similar solvatochromic parameters but markedly different three dimensional configurations was used to explore the possible effects of molecule shape on PGC adsorption. The extent of π‐π interactions between the solutes (stilbene and stilbene‐like molecules) and the carbon surface was predominately controlled by the three‐dimensional shape of the solutes. In every case the planarity of the solute correlated with the retention of the solute.
Diluted modified cyclodextrins as chiral capillary gas chromatographic stationary phases: Influence of the polysiloxane solvents on enantioselectivity and column efficiency
Authors: Dietrich Armin , Maas Birgit , Mosandl Armin
Published: May 2005

The influence of different polysiloxane solvents on the efficiency and stereoselectivity of columns coated with mixtures of heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin (DIME‐6‐TBDMS‐β‐CD) and the polysiloxanes was investigated. In the case of DIME‐6‐TBDMS‐β‐CD, the enantioselectivity of the chiral selector is strongly influenced by the polysiloxane used as diluting phase. Enantioselectivities achieved using apolar polysiloxanes are usually higher than those obtained with increased cyclodextrin content in a more polar polysiloxane, without the drawback of reduced column efficiency resulting from high cyclodextrin content. Changing the polarity of the polysiloxane can also be useful for limited “selectivity tuning” of the chiral stationary phases, for resolving randomly co‐eluting peaks.
Effects of pH and organic solvent on chromatographic behavior in capillary electrochromatography
Authors: Kitagawa Shinya , Tsuda Takao
Published: May 2005

Electrochromatography is demonstrated using a 50 μm i.d. capillary column. The separation of solutes due to their different mobilities is obtained by the application of high voltage along the column. The elution times of solutes are dependent on the pH and composition of the eluent. Both electrophoretic and electroosmotic flow velocities are almost constant between 30 and 90% methanol in the eluent, and they increase with more than 90% methanol. The pH dependence of the electroosmotic flow velocity may be related to the dissociation of unreacted silanol groups on the surface of the ODS‐silica particles.
Electrogenerated chemiluminescence detection for capillary electrophoresis
Authors: Gilman S. Douglass , Silverman Charlotte E. , Ewing Andrew G.
Published: May 2005

Electrogenerated chemiluminescence (ECL) detection based on the reaction of luminol and H2O2 has been developed for capillary electrophoresis. The ECL response at carbon fiber and platinum wire microelectrodes has been investigated. Carbon fiber electrodes are observed to be less sensitive than platinum electrodes but provide a more stable response. The ECL response at a carbon fiber electrode is linear over three orders of magnitude for luminol with a linear correlation coefficient of 0.998. Mass detection limits of 92 amol and 260 amol have been obtained for luminol using platinum wire microelectrodes and carbon fiber microelectrodes, respectively. The influence of hydrogen peroxide concentration (in the detection buffer resrvoir) on the luminescence response has been examined and found to be dependent on electrode type. The dependence of the ECL response on the applied voltage at the microelectrode has been studied for both electrode types. Capillary electrophoresis with ECL detection has been used for analysis of amines derivatized with N‐(4‐aminobutyl)‐N‐ethylisoluminol coupled to N, N‐disuccinimidylcarbonate (ABEI‐DSC). Detection limits of 2.0 fmol and 0.96 fmol are obtained for n‐octylamine and n‐propylamine, respectively. In addition, ABEI‐DSC has been used to successfully label the tripeptide Val‐Tyr‐Val, and micellar electrokinetic capillary chromatography has been used with ECL detection for the separation of ABEI‐DSC labeled amines.
Cyclodextrin PLOT columns for the gas‐solid chromatographic separation of light hydrocarbons and inorganic gases
Authors: Reid George L. , Armstrong Daniel W.
Published: May 2005

Alpha and beta cyclodextrin (α‐ and β‐CD) were chemically bonded to porous layer fused silica open tubular columns and used as gas‐solid chromatographic (GSC) stationary phases for the separation of C1 to C6 hydrocarbons and a variety of inorganic gases. In general, these cyclodextrin PLOT columns were superior to the analogous packed columns. The capillary columns show similar selectivities with an increase in efficiency and number of theoretical plates over the packed columns. The cyclodextrin stationary phases show good selectivities toward the light hydrocarbons and inorganic gases on capillary columns as short as ten meters. Subambient temperatures allow the baseline resolution of oxygen from nitrogen. These columns have been effectively utilized at temperatures up to 260°C without loss of efficiency or degradation of selectivity.
Reversed‐phase liquid chromatography coupled on‐line with capillary gas chromatography II. Use of a solvent vapor exit to increase introduction volumes and introduction rates into the gas chromatograph
Authors: Goosens Elise C. , de Jong Dirk , de Jong Gerhardus J. , Th. Brinkman Udo A.
Published: May 2005

A large‐volume introduction system for capillary gas chromatography (GC) is described which can be coupled on‐line with reversed‐phase liquid chromatography (LC) using 2 mm i.d. LC columns. An on‐column interface with a special retention gap, coated with a very thin film (0.02 μm) of Carbowax was used. Insertion of a solvent vapor exit before the analytical gas chromatography column allowed the solvent evaporation rate for an azeotropic acetonitrile/water mixture (84:16, v/v) to increase from 20 to 175 μL min−1 at 91°C and 150 kPa inlet pressure. A volume of 200 μL of this mixture containing phenanthrene and the potential basic drug eltoprazine, could be injected into the retention gap at introduction rates up to 200 μL min−1, under partially concurrent solvent evaporation conditions. Repeatability (CV = 2.4%) and linearity (at least 10–1000 ng mL−1) were satisfactory. The Carbowax‐coated retention gap has a relatively large retention power for the polar solute. This means that the solvent can be completely evaporated through the vapor exit without loss of analyte. With apolar solutes, losses will occur if evaporation is unduly prolonged. In order to allow the use of a nitrogen‐phosphorus detector, a special pressure‐balanced carrier gas circuit was designed and tested for total solvent‐free performance of the detector. With this set‐up, 150 μL injections of eltoprazine in the acetonitrile/water azeotrope were made at an introduction rate of 200 μL min−1. No traces of acetonitrile were detected, while analyte detectability was 20‐fold higher than with the FID.

Finally, the practicability of reversed‐phase LC‐GC was demonstrated by on‐line heart‐cutting of the phenanthrene‐containing fraction from a 2 mm i.d. LC column using acetonitrile/water (84:16, v/v) as eluent, and analyzing it by capillary GC‐FID.
New μLC/GC interface
Authors: Rusek Miroslav , Cigánková Marie , Krejčí Miloš , Kahle Vladislav
Published: May 2005

The combination of a microcolumn liquid chromatograph with a gas chromatograph is described. The new interface is based on the principle of pneumatic regulation of the effluent flow from the microcolumn chromatograph. In the course of operation, the analyte does not contact the metal components of the apparatus.
Preparation and evaluation of supercritical carbon dioxide‐packed capillary columns for HPLC and SFC
Authors: Tong Daixin , Bartle Keith D. , Clifford Anthony A.
Published: May 2005

Preparation of packed capillary columns with supercritical carbon dioxide as the packing carrier is demonstrated; column performance was evaluated by both HPLC and SFC. It is shown that this procedure yields excellent column performance. The density of the packed bed can be controlled by varying the restrictor dimensions and the packing pressure. Column preparation using a supercritical fluid is more rapid than with liquid slurry packing and yields good column stability. Because supercritical fluids have a wider range of viscosities and velocities, in comparison with gases and liquids, a wide choice of packing conditions is available. Several applications of columns packed by this method are presented.
Chiral separations using packed capillary liquid chromatography
Authors: Cortes Hernan J. , Nicholson Lawrence W.
Published: May 2005

Reduction of the internal diameter of the column used for the separation of enantiomers by liquid chromatography to microcolumn dimensions (0.1‐0.5 mm i.d.) offers significant advantages to the technique, such as low eluent consumption, reduced packing material needs which ensures column‐to‐column reproducibility and lower column costs, and high efficiencies, among others. The present report documents studies conducted in the preparation of highly efficient microcolumns for chiral separations using Chiracel OD stationary phase (3,5‐dimethylphenylcarbamate derivative of cellulose). The resolution, efficiency, and peak asymmetry values obtained using microcolumns were significantly better when compared to a conventional size column (4.6 mm i.d.) of the same length (25 cm). These results may be explained by the more efficient column packing process when using fused silica tubing of narrow diameter as column material. The use of long (80 cm) microcolumns yielded increases in enantiomer resolution of 200–300%. Operation of the long microcolumns at high linear velocities resulted in resolution increases over conventional columns without a decrease in analysis time. In addition to much improved column performance, miniaturization of chiral separation systems has a significant economic impact. Since operating flow rates are 5 μL min−1 compared to 1–2 mL min−1 for conventional columns, a significant savings in the cost of solvents and solvent disposal can be realized by using the microcolumn technology. In addition, the small amount of packing material required to prepare a microcolumn significantly reduces column costs.
Scanning electrochemical detection in capillary electrophoresis
Authors: Ferris Sandra S. , Lou Guoan , Ewing Andrew G.
Published: May 2005

Scanning electrochemical detection has been combined with capillary electrophoresis to increase the resolving power for closely eluting solutes. This detection mode has been characterized and provides voltammetric information for easily oxidized solutes with linear detection over concentrations in the 10−3 to 10−5 M range. Detection limits for catechols range from 360 amol to 740 amol (2.3 μM to 6.6 μM concentrations). Finally, two neutral solutes, catechol and tryptophan, co‐elute under zone electrophoresis conditions, but are resolved with scanning detection.
Chitosan coated capillary with reversed electroosmotic flow in capillary electrophoresis for the separation of basic drugs and proteins
Authors: Sun Peng , Landman Adam , Hartwick Richard A.
Published: May 2005

An enhanced surface coating method was developed for capillary electrophoresis (CE) using the natural polymer chitosan. The cationic property of chitosan at pH below 6.5 created a reversed electroosmotic flow (EOF) in the capillary. The EOF changed significantly with the run buffer pH at values below 4.0, with less pH dependency at values in the pH range of 4.0‐5.5. The new coating exhibited good performance reproducibility. The relative standard deviation (RSD) of EOF was 0.77%. The EOF changed an average of 2.4% after 10 h normal use. The EOF started to change significantly after a constant electric field (300 v cm−1) had been applied for 20 h. This capillary with a reversed EOF can be used to reduce the solute‐wall interaction problem for separations of basic analytes, for example, separations of positively charged proteins and basic drug enantiomers.
Simple detector for microcolumn LC using electrospray ionization
Authors: Št́astná Miroslava , Krejčí Miloš , Kahle Vladislav
Published: May 2005

A simple detector for microcolumn liquid chromatography using electrospray ionization is described. The principle operational parameters of the detector were evaluated. The minimum detectable quantity for a variety of analytes is in the 10−10 mole range or below.
Analytical merit of electrospray ion mobility spectrometry as a chromatographic detector
Authors: Chen Yong Hong , Hill Herbert H. , Wittmer Douglas P.
Published: May 2005

Electrospray ionization ion mobility spectrometry (ESI‐IMS), a technique which has only recently become analytically useful, has been evaluated for use as a detector for microbore liquid chromatography and capillary electrophoresis. Figures of merit for ESI‐IMS were determined. Detection limits as low as 1 × 10−15 mol s−1 were measured, with a linear response range of 3 to 4 orders of magnitude and with reproducibility within 3% (relative standard deviation of peak area). Gradient elution with water/methanol mobile phase did not perturb chromatographic baseline, compound response, or product ion mobility. Both positive and negative ion mobility spectra for more than 30 compounds demonstrated the sensitivity of ESI‐IMS response to a wide range of analytes. Finally, the concept of using ESI‐IMS as an ionization source for gasphase samples was presented, potentially unifying detector application for both gas and liquid chromatography.
Self‐assembled alkylsilane monolayers for the preparation of stable and efficient coatings in capillary electrophoresis
Authors: Huang Mingxian , Dubrovcakova‐Schneiderman Eva , Novotny Milos V. , Fatunmbi Hafeez O. , Wirth Mary J.
Published: May 2005

The approach of forming self‐assembled monolayers on the surface of fused silica capillaries has been evaluated for capillary electrophoresis of proteins. Two polymer matrices (polymerized acrylamide or methacryloyl‐Tris) were successfully grafted on the self‐assembled monolayers, as evidenced by electroosmotic flow measurements and efficient separations of model proteins.
Gas chromatography‐atomic emission detection (GC‐AED) set‐up for bio‐monitoring of PCBs and methylsulfonyl‐PCBs
Authors: Janák Karel , Grimvall Eva , Östman Conny , Colmsjö Anders , Athanasiadou Maria , Bergman Åke
Published: May 2005

Gas chromatography‐atomic emission detection (GC‐AED) has been evaluated in order to determine the optimal conditions for chlorine and sulfur response of chlorinated biphenyls (CBs) and methylsulfonyl metabolites of CBs (MeSO2‐CBs). The influence of the shape of the capillary column end facing the plasma, make‐up gas flow, additional transfer line make‐up gas flow and reagent gas flows on the detector response has been studied. Using an additional make‐up gas flow applied through a transfer line capillary having a decreased outlet diameter yielded an increased detector response with minimum detectable levels for sulfur and chlorine of 1.7 and 20 pg, respectively. Further, a substantial decrease in peak tailing was achieved. The applicability of the method for analysis of biological materials is demonstrated by the determination of the main CB congeners present in human blood and of MeSO2‐CBs in seal blubber.
Determination of trace quantities of volatile sulfur compounds in aqueous solutions by gas chromatography after purge and trap isolation and cryogenic focusing
Authors: Wardencki Waldemar
Published: May 2005

A method for the determination of volatile organic sulfur compounds, such as dimethylsulfide (DMS), at the nanogram level in aqueous samples is described. A purge and trap technique was used to remove and preconcentrate DMS and other sulfur compounds from aqueous solutions. Trapping of the isolated compound was performed on Tenax TA and Carbosieve III S. The water vapor from the purging stream was removed by a commercially available Nafion tube inserted in a plastic container packed with molecular sieve 5A. Analytes, after thermal desorption, were recollected in a short fused silica capillary tube cooled with the vapors of liquid nitrogen to a temperature ca. −150°C. Next, sulfur compounds were revolatilized and directly transferred to the analytical capillary column for analysis. Detection was performed with a flame photometric detector. The whole procedure was optimized and checked using a homemade valving device easily coupled to any gas chromatograph. The method has been used to measure DMS and other volatile sulfur compounds in seawater of the Baltic Sea and in samples of water from three rivers in the Gdańsk, Poland, region.
Estimation of the dissociation constant for unreacted silanol groups on the surface of ODS‐silica from the relationship between ph and electroosmotic flow velocity in capillary electrochromatography
Authors: Kitagawa Shinya , Tsuda Takao
Published: May 2005

Electroosmotic flow in electrochromatography is generated by surface charges on the packing materials under an applied voltage. The surface charge density of ODS‐silica gel is increased by dissociation of unreacted silanol groups, and the dissociation constant is dependent on pH. We have developed an equation for the relationship between pH and electroosmotic flow velocity. By using this equation, we estimate the dissociation constant of unreacted silanol groups from their relationships in electrochromatography to be 10−4.3.

The proposed method has the following features: (1) the dissociation constant can be estimated in situ by using a column for electrochromatography or capillary electrophoresis without any alteration of the instrumentation, and therefore (2) the dissociation constant obtained is directly useful for the selection of separation conditions.
Effects of buffer concentration on the electrophoretic behaviors of small peptides in capillary zone electrophoresis
Authors: Chen Nong , Wang Lei , Zhang Yukui
Published: May 2005

It was found that unlike the electroosmotic flow, the electrophoretic mobilities of small peptides in capillary zone electrophoresis (CZE) were invariant over the buffer concentration range studied. Migration of these peptides in CZE is a electroosmotic‐governed process. The quantitative linear relationships between the logarithm of migration times (log tm) and the reciprocal of column temperature were investigated under different buffer concentrations to study the activation energies of diffusion (AED) as the function of the buffer concentration. The preexponential factors were quantitatively correlated with the structural parameters of the peptides studied. © 1995 John Wiley & Sons, Inc.
Comparison of selectivities for PCBs in gas chromatography for a series of cyanobiphenyl stationary phases
Authors: Hillery Barbara R. , Girard James E. , Schantz Michele M. , Wise Stephen A. , Malik Abdul , Lee Milton L.
Published: May 2005

Selectivity for polychlorinated biphenyl (PCB) congeners was examined for a series of cyanobiphenyl stationary phases, and the results were compared to a nonpolar 5% phenyl methylpolysiloxane phase and a shape‐selective smectic liquid crystalline phase. For all of the columns studied, the degree of ortho substitution of the congener was found to be a significant factor controlling chromatographic retention of PCBs. The retention pattern on six different cyanobiphenyl phases followed the same general pattern as on the liquid crystalline column, though the trends were more exaggerated on the liquid crystalline phase. While the general retention pattern was similar for all of the cyanobiphenyl phases studied, subtle differences were observed, resulting in significant selectivity differences. For isomeric planar PCB congeners, elution order could be correlated to length‐to‐breadth ratios. Among the cyanobiphenyl phases, the p,p‐ and the o,p,p‐cyanobiphenyl phases had the greatest enhancement of retention for planar congeners. A shapeselective test mixture reflected the similarity of retention on the cyanobiphenyl phases to both the 5% phenyl methylpolysiloxane phase and the smectic liquid crystalline phase. © 1995 John Wiley & Sons, Inc.
Investigation of parameters affecting the supercritical fluid extraction of polymer additives from polyethylene
Authors: Lou Xianwen , Janssen Hans‐Gerd , Cramers Carel A.
Published: May 2005

Polymer additives were extracted from polyethylene with supercritical carbon dioxide. The two‐film theory, which considers mass transfer across a phase boundary, is applied to qualitatively describe the kinetics of mass transfer from the core of the polymer particles into the supercritical fluid extractant. The effects of pressure, temperature, addition of benzene as a modifier, properties and concentrations of the solutes, static time, and supercritical fluid extractant flow rate on the extraction process are investigated systematically. At constant temperature the extraction rates first increase with increasing pressure. When pressure reaches a certain level, a further increase of the pressure does not further increase the extraction rates. At constant pressure, the extraction rates were found to increase first and then decrease with increasing temperature. In addition to pressure and temperature, the SFE extraction kinetics is also influenced by the solute concentration, and the rate‐limiting parameter in the extraction can be changed from solubility to diffusion during the course of the extraction. The magnitude of the effects of the experimental parameters depends on the properties and molecular weights of the solutes. The role of benzene as a modifier in the extraction of polymer additives from polyethylene is swelling the polymer particles and improvement of the solvent strength of the supercritical fluid extractant. Modifier effects were found to be more pronounced at lower temperatures. © 1995 John Wiley & Sons, Inc.
Capillary electrophoresis using air and helium as cooling fluids
Authors: Cifuentes Alejandro , Kok Wim Th. , Poppe Hans
Published: May 2005

A comparative study on the properties of helium and air as thermostatting fluids in Capillary Electrophoresis (CE) has been carried out. Equations that relate the properties of fluids to their control of the temperature of the capillary are shown. Results from theory and experiments are compared under different cooling conditions, i.e., natural and forced gas convection, using air and helium. Experimental results are qualitatively in good agreement with those predicted by theory. The better thermostatting capability of helium compared to air is demonstrated by an improved efficiency in real separations and a lower degree of denaturation of a thermolabile protein during its purification by CE. © 1995 John Wiley & Sons, Inc.
Modifier addition in microcolumn supercritical fluid chromatography
Authors: Robson Mark M. , Raynor Mark W. , Bartle Keith D. , Clifford Anthony A.
Published: May 2005

Recent advances in techniques for the packing of microcolumns of down to 50 μm inner diameter using supercritical CO2 have led to rapid growth in the use of high efficiency packed capillary columns in SFC. Maximization of the usefulness and applications of these techniques requires gradient elution chromatography and the development of pumps capable of delivering 0.1 to 1 μl per minute of modifier. A micro SFC‐LC pump has been tested in the isocratic and gradient elution mode with CO2 as the supercritical fluid and methanol as the modifier. The pump was tested using the EPA priority PAHs as the test mixture with a specially treated ODS column and UV detection. Results are presented for testing in the isocratic and gradient elution modes and the retention times are shown to have a coefficient of variation of less than 2%. The application of this system to the analysis of PAHs in coal derivatives is shown. The problems encountered in the use of formic acid as a modifier in SFC are discussed. © 1995 John Wiley & Sons, Inc.
Analytical separation of Trichoderma Reesei cellulases by Capillary Zone Electrophoresis
Authors: Khaled Maha Y. , McNair Harold , Polite Lee , Pauls Richard
Published: May 2005

The Capillary Zone Electrophoretic separation of the four common enzymes of Cellulase, the endo‐(EG I, EG II) and the exo‐(CBH I, and CBH II) glucohydrolases from the fungi Trichoderma Reesei, is presented. The separation using underivatized fused silica capillaries with 0.03 M Na2HPO4 at an optimum pH of 9.2 proved successful, rapid, and reproducible. Variations in buffer type, ionic strength, pH, temperature, and reduced electroosmotic flow and their effects on the separation were investigated revealing a significant effect on the efficiency, the separation, and the integrity of the enzymes. © 1995 John Wiley & Sons, Inc.
Direct analysis of cortisol and cortisone in human urine by semi‐microcolumn liquid chromatography with mixed‐function precolumn
Authors: Kanda Taketoshi , Shirota Osamu , Ohtsu Yutaka , Yamaguchi Michihiro
Published: May 2005

A column‐switching system based on semi‐microcolumns is constructed for direct analysis of cortisol and cortisone in human urine samples. Urine samples (100 μl) were directly injected into a polymer‐coated mixed‐function (PCMF) column (35 mm × 1.5 mm i.d.), which removes proteins and fractionates an analyte‐containing zone. The analyte‐containing fraction was thereafter transferred to a C18 semi‐microcolumn (250 mm × 1.5 mm i.d.). The analytes were monitored with ultraviolet (UV) absorption at 242 nm, with the detection limit for cortisol and cortisone, 3 pmol/mL (at a S/N ratio of 5) for each. The system showed quantitative results for dilute standard samples using human urine as a solvent. The method could be applied to the routine assessment of cortisol and cortisone in human urine. © 1995 John Wiley & Sons, Inc.
Characterization of the physiological condition of Eucalyptus globulus labil by headspace HRGC analysis of the bouquet of odors
Authors: Mateus Eduardo P. , Farrall Maria H. , Paiva M. Rosa
Published: May 2005

The borer Phoracantha semipuntacta originates from Australasia and has spread to Africa, Europe, and America where it attains major pest status on eucalyptus crops. However, in an eucalyptus stand not all trees are equally attractive to females of P. semipunctata searching for ovipositing sites. Previous studies indicate a non‐random host selection process in which olfactory stimuli play an important role. Field experiments, conducted to decode the mechanisms of primary attraction, showed that eucalyptus logs originating from trees already attacked by the borer captured significantly more adults and eggs of P. semipunctata than the ones cut from vigorous trees. A High Resolution Gas Chromatography‐Head Space (HRGC‐HS) technique was used, to analyze and compare the profiles of the volatiles emitted by attacked, and unattacked E. globulus. Identification of the chromatographic peaks was achieved by GC‐MS. Significant differences were found between the two types of trees, particularly in the contents of α‐phellandrene, α‐pinene, and p‐cymene. A relationship between tree physiological condition—attacked or unattacked—and the bouquet of odors emitted was thus established.
The effects of cisapride on plasma L‐dopa levels and clinical response in Parkinson's disease
Authors: Neira Walter Diaz , Sanchez Vicenta , Mena Maria Angeles , de Yebenes Justo Garcia
Published: May 2005

Cisapride (CIS) is a prokinetic agent that increases gastrointestinal motility in normal individuals and improves constipation in Parkinson's disease (PD). We studied the effects of CIS on the clinical response and the peripheral pharmacokinetics of orally administered L‐dopa given to patients with PD. Twenty patients with idiopathic PD and chronic constipation, whose response to L‐dopa was suboptimal or characterized by fluctuations, agreed to participate in an open study that lasted for 2 weeks. Fourteen patients completed the study (mean age 65 ± 9.3 years, mean duration of treatment 5.7 ± 4.2 years, mean L‐dopa daily doses 658.9 ± 269.9 mg); six patients were excluded due to lack of compliance or changes in medication during the study. The end points of the study included the mean levels of L‐dopa, the height of the peak of L‐dopa in plasma, mean plasma levels of 3‐OM‐dopa, and the speed and quality of gait and visuomanual corrdination before and during treatment with CIS. CIS increased peak plasma levels of L‐dopa by 37% and the mean plasma levels of L‐dopa by 13% with respect to those obtained with the same dose of L‐dopa before the addition of CIS. Therefor, CIS appears to increase early absorption of L‐dopa through acceleration of gastric emptying. CIS also increased plasma 3‐OM‐dopa levels, improved visuomanual coordination, and reduced gait disability. CIS improves gastrointestinal function and response to L‐dopa in patients with PD and could be a helpful add‐on medication in these patients.
Frontal and parietal premovement slow brain potentials in Parkinson's disease and aging
Authors: Bötzel K. , Mayer M. , Oertel W. H. , Paulus W.
Published: May 2005

During the anticipation of a stimulus that induces a predetermined pattern of behavior, a slowly increasing negative electric potential can be recorded from the human scalp at central and parietal electrodes and has been named contingent negative variation (CNV). We used a simple and a choice reaction time paradigm to investigate premovement potentials in patients with Parkinson's disease (PD) and in normal controls. There was a clear CNV in young subjects whereas it was negligible in the elderly control subjects and absent in the patients. In addition, we found a slowly increasing positive frontal potential. In normals the steepness of this potential decreased with the complexity of the task (simple vs. choice) and with age. This difference was abolished in the patients: If a slowly increasing positivity was observed at all, it was, on average, larger in the choice task. Reaction times of the patients were disproportionally prolonged in the simple compared to the complex task. These findings support the hypothesis that storing or initiating a simple preprogrammed motor response is more impaired in PD than selecting and initiating a motor response of a more complex task. The electrophysiological recordings suggest that impaired activation of the frontal lobes may be responsible for this deficit.
Tourettism associated with Huntington's disease
Authors: Jankovic Joseph , Ashizawa Tetsuo
Published: May 2005

The identification of the gene for Huntington's disease (HD) has made it possible to diagnose patients with HD who present with unusual or atypical features. We describe a 41‐year‐old man whose intial manifestation of HD was dominated by the presence of motor and vocal tics and other features of Tourette's syndrome. This case illustrates the broad range of clinical manifestation of HD and the usefulness of testing for the HD mutation in selected cases with familial movement disorders.
Psychiatric symptoms, atypical dementia, and left visual field inattention in corticobasal ganglionic degeneration
Authors: Rey G. J. , Tomer R. , Levin B. E. , Sanchez‐Ramos J. , Bowen B. , Bruce J. H.
Published: May 2005

We longitudinally examined the neuropsychological and psychiatric characteristics of an adult male with pathologically confirmed corticobasal ganglionic degeneration (CBGD). The patient was seen on an inpatient and outpatient basis by members of the Departments of Neurology and Radiology of the University of Miami School of Medicine. Longitudinal neuropsychological testing revealed a lateralized cortical‐subcortical dementia and left visual field inattention consistent with neurological and postmortem neuropathological findings of greater right hemisphere dysfunction. Symptoms of depression and obsessive‐compulsive symptomatology were also documented. Our findings are consistent with prior reports indicating that CBGD is characterized by lateralized cerebral dysfunction and suggest that a detailed neuropsychological examination is a useful procedure to assist in the differential diagnosis of this movement disorder.
Spread of symptoms in idiopathic torsion dystonia
Authors: Greene Paul , Kang Un Jung , Fahn Stanley
Published: May 2005

We reviewed the histories of 115 patients who had idiopathic dystonia and who were 21 years of age and younger at onset of symptoms and 472 patients with older than age 21. Patients with onset in the lower extremities tended to be younger at onset (mean age 8.4 years), have rapid spread of symptoms to other body parts, and to develop generalized dystonia. Patients with onset in the upper extremities tended to be older at onset (mean age 11.2 years) and were less likely to develop generalized dystonia, but were more likely to experience spread of symptoms many years after the disease began. Almost 20% of patients younger than age 22 began with torticollis, and 67% of these remained focal after a mean 14.9 years. In adults, dystonic symptoms remained focal in the majority, but ∼ 15–30% of patients presenting with blepharospasm, torticollis, laryngeal or brachial dystonia eventually experienced dystonia outside the initially involved segment. Almost 50% of children and adolescents with dystonia reported a family history of dystonia, compared with ∼ 10–13% of patients with torticollis, laryngeal or brachial dystonia. Less than 3% of patients with blepharospasm reported a family history of dystonia. There were only minor differences in the pattern of spread of dystonic symptoms between Jewish and non‐Jewish patients. Although younger patients were more likely to report a family history of dystonia, patterns of spread were the same for familial and sporadic patients in the same age range.