bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyacrylamide‐modified polypropylene hollow fibers for capillary electrophoresis
Authors: Liu Peter Z. , Malik Abdul , Kuchar Marvin C. J. , Lee Milton L. 
Published: May 2005

AbstractSurface treatment methods were developed for bonding of a polyacrylamide layer on the inside surface of polypropylene hollow fiber columns for capillary electrophoresis. Details of different modification procedures involving surface activation and in situ polymerization, using dynamic and static coating of reagents, are described. Both linear and cross‐linked polyacrylamide modified surfaces greatly improved the electrophoretic performance of the capillaries. The column efficiencies for model proteins reached as high as 370,000 theoretical plates on an 85 μm i.d. polyacrylamide surfacetreated polypropylene hollow fiber column. A variety of applications, including the separation of several very polar compounds at a pH of 10.6, were demonstrated. Reproducibility measurements were used to illustrate the performance and high pH stability of the resultant columns.
Optimization of resolution of 13 diuretics in CZE by controlling capillary length and electroosmotic flow velocity
Authors: Jumppanen Juho Hermanni , Riekkola Marja‐Liisa , Haario Heikki 
Published: May 2005

AbstractThe separation of diuretics in CZE can be further improved by controlling the capillary length and the analysis times independently, while other parameters are kept constant. This can be done by using a modifier in the electrolyte solution which has a strong effect on the electroosmosis, but negligible effect on the selectivity of the electrolyte system.In this work, [Cu(NH3)4]2+ was used at low concentration (0 – 140 μM) to control the electroosmotic flow velocity (veo) and hence the analysis time, determined as the migration time of the last migrating compound (tfin). With other parameters, especially V, kept constant, the use of shorter capillaries enables the use of high electric field strength for the separation.The use of quadratic regression models proved to be an effective way to study the effect of Ltot and tfin on the Rs of each analyte pair. The theoretical values for the separation of peak maxima correlated well with the values predicted by the empirical regression models. The actual band broadening was much stronger, however, than what was predicted by the overly simplified theoretical calculations based on the electrophoretic mobilities as well as the self diffusion coefficients of the diuretics, determined by the two marker technique. Further study is needed on theoretical modelling of the band broadening, while the use of regression models and desirability functions provided a convenient way to determine the optimal conditions.The results showed that independent control of Ltot and tfin offers an effective way to further optimize capillary electrophoretic separation. This method should prove important in cases where sufficient separation is difficult to achieve.
Calculation of statistical attributes in small regions of separations: Variation of overlap probability along the separation coordinate
Authors: Davis Joe M. 
Published: May 2005

AbstractTheory based on the extended statistical model of overlap (SMO) is proposed to predict the numbers of components in small regions of separations and the likelihood of overlap along the separation coordinate. The extended SMO is an expansion of theory begun a decade ago and, unlike its predecessor, allows one to estimate statistical parameters from separations containing peaks of variable density. These estimations are made possible by frequencies that scale the relative density of peaks. Using a frequency determined from a complex separation, one can critique overlap in small regions of the separation containing as few as five components. The ability to quantify overlap in small regions allows one to characterize local overlap patterns that would be obscured by interpretation of large regions. Furthermore, with the frequency, the probability of forming singlet and multiplet peaks can be calculated along the separation coordinate. Unlike with earlier theory, the frequency allows the values of these probabilities to change continuously throughout the separation. Applications of theory are made to four gas chromatograms of lime oil, which were developed by different temperature programs to vary the peak density therein.
Low concentration drug analysis by semi‐microcolumn liquid chromatography with a polymer‐coated mixed‐function precolumn
Authors: Shirota Osamu , Suzuki Ayako , Kanda Taketoshi , Ohtsu Yutaka , Yamaguchi Michihiro 
Published: May 2005

AbstractThe construction and performance of dual‐and triple‐column systems for the analysis of dilute drug samples are described. The systems are based on the following two separation processes: (1) deproteinization and analyte fractionation using a short polymer‐coated mixed‐function (PCMF) phase (10 mm × 4.0 mm i.d. column) and, (2) final separation using a C18 semi‐microcolumn (1.5 to 2.0 mm i.d.). The surface structure of the MF phase and the geometry of the packed column for the primary separation made it possible to inject hundreds of microliters of serum samples into the system. Analytes separated in the primary chromatography are transferred to the main column with or without an intermediate column (35 mm × 1.0 mm i.d.). A system using an intermediate column was designed to save time of analysis when a 1.5‐mm i.d.(and smaller) main column was used. The systems showed an increased concentration sensitivity for drug molecules, such as diazepam, carbamazepine, and phenobarbital, without any loss in chromatographic efficiency. Carbamazepine and phenobarbital at 12.5 ppb and 50 ppb, respectively, in human serum were detected with good S/N ratio.
Structural characteristics of pendant and copolymeric cyclodextrin polysiloxane stationary phases and their influence on chiral selectivity and resolution in capillary gas chromatography
Authors: Malik Abdul , Yun Hao , Yi Guoliang , Bradshaw Jerald S. , Rossiter Bryant E. , Markides Karin E. , Lee Milton L. 
Published: May 2005

AbstractThe dependence of gas chromatographic properties on stationary phase structural characteristics was evaluated for three different types of cyclodextrin‐bonded polysiloxanes: small‐rim‐tethered, large‐rim‐tethered, and copolymeric. Separation efficiency, chiral selectivity, and resolution were investigated as functions of stationary phase structural features such as length and chemical composition of the connecting arms, chemical composition of the substituent groups on the small rim of the cyclodextrin toroid, and the position(s) of connecting arm attachment(s) on the cyclodextrin rims. For all of the solutes and experimental conditions used in this study, the small‐rim‐tethered cyclodextrin phases were found to provide superior chromatographic performances compared to the other two types of cyclodextrin phases. The chiral selectivities of the investigated phases were found to depend both on chemical composition and length of the connecting arm(s). Shorter connecting arms were found to provide improved chiral selectivities. Stationary phases having a four‐carbon connecting arm with an etheric oxygen linkage in the chain provided higher chiral selectivities compared to stationary phases with hydrocarbon or phenoxy group‐containing connecting arm(s). The chiral selectivities of the studied phases did not change when the substituents at the C‐6 positions were changed from ‐CH2OCH2 to ‐CH3. Efficiency values of up to 5,000 theoretical plates per meter were obtained using 200 μm i.d. columns. Column efficiency was found to be independent of structural features of the cyclodextrin toroid and the connecting arms.
Enantioselective separations by capillary gas chromatography on derivatized cyclodextrins. Part IV: Enantioselective interaction model of 2,2‐dialkyl‐4‐alkoxycarbonyl‐1,3‐dioxolane derivatives on some substituted cyclodextrins
Authors: Jaques K. , Buda W. M. , Venema A. , Sandra P. 
Published: May 2005

AbstractAn evaluation of the effects of differently derivatized cyclodextrins and analyte geometry for a series of 2,2‐dialkyl‐4‐alkoxycarbonyl‐1,3‐dioxolane derivatives on enantioselectivity has been performed. It was shown that changes in the cyclodextrin cavity size, caused by either the choice of type (α‐, β‐ or γ‐cyclodextrin) or substitution pattern, strongly affect the selectivity of the chiral separation of the substituted dioxolanes. The geometry of the analyte also appears to be very important to the selectivity. A model of the inclusion complex is proposed.
Pore size influence in chiral packed column micro‐LC
Authors: Svensson Lars A. , Karlsson Karl‐Erik 
Published: May 2005

AbstractFused silica capillary columns containing α‐chymotrypsin‐modified silica were used to separate the enantiomers of naproxen. The separation was followed with a fluorescence detector that could be moved to several positions along the column. The interest was focused on the effect of the pore size of the original unmodified diol‐silica‐gel. The results indicate that the large pore material yields more efficient columns. It was also noted that the van Deemter plot reached a plateau value at higher flow rates for this large pore material. © 1995 John Wiley & Sons, Inc.
On‐line sample enrichment–capillary gas chromatography of aqueous samples using geometrically deformed open‐tubular extraction columns
Authors: Mol Hans G. J. , Janssen Hans‐Gerd , Cramers Carel A. , Brinkman Udo A. Th. 
Published: May 2005

AbstractThe effect of geometrical deformation of open‐tubular extraction columns on peak dispersion of retained solutes is evaluated. By coiling or stitching of the columns peak dispersion is decreased, with a factor of two and more than five, respectively, due to secondary flow enhanced radial dispersion. This enables the increase of sampling flow rates in on‐line extraction‐GC using open‐tubular extraction columns up to 4 mL/min while still obtaining quantitative trapping of the analytes. © 1995 John Wiley & Sons, Inc.
Cyclodextrin derivatives in GC separation of racemic mixtures of volatiles. Part IX. The influence of the different polysiloxanes as diluting phase for 2,3‐di‐O‐acetyl‐6‐O‐t‐butyldimethylsilyl‐β‐cyclodextrin on the separation of some racemates
Authors: Bicchi C. , D'Amato A. , Manzin V. , Galli A. , Galli M. 
Published: May 2005

AbstractThe results of a series of experiments concerning the GC enantioseparation of some racemates on columns coated with 2,3‐di‐O‐acetyl‐6‐O‐t‐butyldimethylsilyl‐β‐cyclodextrin diluted in two different polysiloxanes (PS‐086 and OV‐1701) are reported. The investigation is centered on the influence of the diluting phase on the separations of the racemates investigated [δ‐heptalactone, linalyl acetate, and an homologous series of cis‐2‐(2‐alkyl‐cyclopropyl)‐ethanol (alkyl from ethyl to heptyl)] because one of the two polysiloxanes separated them, whereas the other did not. Column retention and efficiency characteristics were investigated as a function of the diluting phase. Retention increase (RI) and Gibbs–Helmholtz parameter (ΔR,SΔG) were determined for each of the above racemates, analyzed by different mixtures of the CDD selector with the two diluting phases. © 1995 John Wiley & Sons, Inc.
Analysis of fumonisin B1 in corn by capillary electrophoresis with fluorescence detection of the FMOC derivative
Authors: Holcomb Manuel , Thompson Harold C. 
Published: May 2005

AbstractA new method has been developed for the analysis of fumonisin B1 in corn using capillary electrophoresis. Fumonisin B1 is the major fumonisin metabolite produced by the fungus Fusarium moniliforme and has been implicated in human and animal diseases. Fumonisin B1 was extracted from corn with acetonitrile/water (50/50) and cleaned up with a Waters C18 Sep‐Pak Vac cartridge. Fumonisin B1 was quantitated after elution from the C18 Sep‐Pak column using capillary electrophoresis (CE) with a 25 mM sodium borate buffer (pH 9.0) containing 10% acetonitrile and fluorescence detection of the FMOC derivative. The minimum detectable amount in corn was 0.5 ppm. Recovery values in spiked corn averaged over 96% over the range 1–20 ppm. © 1995 John Wiley & Sons, Inc.
Application of peralkylated β‐CDs capillary columns for the GC separation of positional isomers of industrial chemicals
Authors: Dai Rongji , Fu Ruonong , Zhou Wei 
Published: May 2005

AbstractPeralkyiated β‐cyclodextrins were used as stationary phases to separate positional isomers of industrial chemicals. Their selectivity was measured using isomers of dimethylphenols. Among the peralkylated β‐cyclodextrins, permethylated β‐cyclodextrins possess the highest selectivity. Finally, they were used to separate some positional isomers such as disubstituted benzene and so on. The results show that peralkylated β‐CDs were excellent GC stationary phases in industrial analysis.
Capillary electrophoresis/electrospray ionization ion trap mass spectrometry using a sheathless interface
Authors: Ramsey Roswitha S. , McLuckey Scott A. 
Published: May 2005

AbstractThe sensitivity that can be obtained with the quadrupole ion trap for on‐line CE analysis using a sheathless electrospray interface and gold‐tipped columns is examined. Capillaries of different i.d. are compared in continuous infusion experiments and the effects of sheath solvents on the signal for some peptides and proteins are illustrated. The sheathless CE/ITMS system using 20 μm i.d. columns is shown to provide mid‐attomole detection levels for leucine enkephalin in total ion electropherograms under full scan conditions. Good quality MS/MS spectra are also obtained for low femtomole injections of this peptide.
Modification of the inner capillary surface by the sol‐gel method: Application to open tubular electrochromatography
Authors: Guo Yong , Colón Luis A. 
Published: May 2005

AbstractThe sol‐gel procedure was used to prepare an organically modified silica glass coating material which was used as the stationary phase for reversed‐phase open tubular electrochromatography. The unique column preparation scheme is simplified by combining the synthesis of the stationary phase and the attachment of the supporting porous glass matrix in a single‐step procedure. This approach significantly increases surface area which results in a higher phase ratio. Controlling the amount of the precursor materials used in the sol‐gel solution provides a means to adjust the carbon content in the stationary phase. The column performance was evaluated using a test mixture of polycyclic aromatic hydrocarbons; under certain experimental conditions, efficiencies around 500,000 theoretical plates per meter were obtained for some test solutes.
High temperature liquid chromatography on packed capillary columns with nonaqueous mobile phases
Authors: Trones Roger , Iveland Asbjorn , Greibrokk Tyge 
Published: May 2005

AbstractThe need for a high resolution chromatographic technique for analyzing compounds that are heavy, relatively polar, have low water solubility, and are not adequately separated by regular HPLC methods, has led to the development of a high temperature liquid chromatography system. The increased diffusion coefficients and reduced viscosity at higher temperatures resulted in high separation velocities and allowed long columns to be used. The HTLC system contained 70 cm columns and nonaqueous mobile phases. Packed capillary columns prevented radial temperature gradients which otherwise would reduce the efficiency. The capillary columns were packed with a reversed phase material (ODS) using supercritical carbon dioxide as the slurry fluid. A new method for preparing a ceramic frit inside the column was developed. The frit withstood pressures of at least 600 bar. The robustness of the columns in a nonaqueous environment with elevated temperature was tested and found satisfactory for 150 injections with a temperature program at each injection. Isothermal elution or temperature programming in the 50–150°C range reduced the analysis time significantly. Compounds which were completely retained at room temperature eluted with good peak shape at elevated temperature.
Evidence of peripheral axonal neuropathy in primary restless legs syndrome
Authors: Iannaccone Sandro , Zucconi Marco , Marchettini Paolo , Ferini‐Strambi Luigi , Nemni Raffaello , Quattrini Angelo , Palazzi Stefano , Lacerenza Marco , Formaglio Fabio , Smirne Salvatore 
Published: May 2005

AbstractRestless legs syndrome (RLS) is a well‐defined clinical entity characterized by an unpleasant creeping sensation arising in the legs with an irresistible need to move them. The trouble is more pronounced when the affected people lie in a prolonged rest position and try to fall asleep. It is known that RLS may be consequent to systemic disorders and to diseases affecting the central or peripheral nervous system. The International Classification of Sleep Disorders states that peripheral neuropathy should be ruled out by medical history and clinical grounds before diagnosing primary RLS (pRLS). The present study extended peripheral nerve investigation in eight consecutive pRLS patients with normal neurological examination results and showed that all patients exhibited two or more electrical, psychophysiological, and/or morphological features of peripheral axonal neuropathy. Morphometric analysis of sural nerve showed a significant reduction in myelinated fiber density and g ratio (axon diameter/fiber diameter) in the pRLS group compared with eight control biopsy specimens. These results suggest that axonal neuropathy is often present in patients with RLS. A comprehensive peripheral nerve investigation should be considered in RLS patients.
Striatal dihydroxyphenylalanine decarboxylase and tyrosine hydroxylase protein in idiopathic Parkinson's disease and dominantly inherited olivopontocerebellar atrophy
Authors: Zhong Xiao‐Hui , Haycock John W. , Shannak Kathleen , Robitaille Yves , Fratkin Jonathan , Koeppen Arnuf H. , Hornykiewicz Oleh , Kish Stephen J. 
Published: May 2005

AbstractWe measured the levels of dopamine, tyrosine hydroxylase (TH) protein, and dihydroxyphenylalanine (DOPA) decarboxylase (DDC) protein in the striatum of 10 patients with idiopathic Parkinson's disease (PD) and 23 patients with dominantly inherited olivopontocerebellar atrophy (OPCA). The levels of dopamine were markedly reduced (2% of control) in the striatum of the patients with PD, whereas striatal dopamine in the patients with OPCA ranged from normal (<60% of control) to moderately reduced (20–60% of control) to severely depleted (<20% of control). Both TH and DDC protein levels were significantly lower than those of the controls in the striatum of all of the patients with PD and in the subgroup of patients with OPCA having severely depleted dopamine. In contradistinction, TH but not DDC protein levels were reduced in those patients with OPCA having moderately reduced dopamine levels. This suggests that in the early stage of nigrostriatal dopamine neurone degeneration, DDC levels may be less susceptible to neurodegenerative influences than is TH synthesis or, alternatively, DDC synthesis may be more aggressively upregulated. Unexpectedly, from the blot immunolabeling analysis an additional DDC‐immunoreactive band of slightly lower apparent molecular mass was detected in two of the patients with PD and in 12 of the patients with OPCA. This additional DDC band, which was not present in any of the control subjects, may reflect posttranslational modification(s) of DDC related to the neurodegenerative process.
Gonadal sex hormones and dystonia: Experimental studies in genetically dystonic hamsters
Authors: Löscher Wolfgang , Blanke Thomas , Richter Angelika , Hoppen Hans‐Otto 
Published: May 2005

AbstractIn some kinds of idiopathic dystonia, including paroxysmal dystonia, a role of sex hormones has been suggested because of female predominance and onset, recurrence, or exacerbation of dystonic symptoms with pregnancy. Similar effects of pregnancy have recently been reported in a model of paroxysmal dystonia, the genetically dystonic hamster. Dystonia in mutant hamsters of both genders is transient, i. e., exhibits spontaneous remission at around puberty, strongly suggesting involvement of gonadal sex hormones. For exploration of the role of sex hormones in dystonia, we undertook a series of ontogenetic experiments in male and female dystonic hamsters. Mutant animals of both genders exhibited the same postnatal development of dystonia with maximum severity of dystonic attacks between weaning and ∼40 days of age and spontaneous remission thereafter. As shown by plasma sex hormone determinations and, in females, vaginal cytology, spontaneous improvement of the movement disorder coincided with puberty in both genders. Male and female hamsters had about the same plasma levels of progesterone. Compared with nondystonic hamsters, onset of puberty was significantly retarded in both male and female dystonic hamsters. Furthermore, body weight gain was lower in dystonic animals, indicating retarded postnatal development. Gondectomy at time of weaning did not alter the age‐dependent development and remission of dystonia, suggesting that gonadal sex hormones are not critically involved in the disease in hamsters. We propose that transient paroxysmal dystonia in mutant hamsters is caused by postnatal retardation of brain development resulting in a temporary impairment of brain functions with spontaneous remission independent of gonadal sex hormones. In view of the fact that the brain can synthesize steroids such as progesterone independent of peripheral glands in both genders, such neurosteroids might be involved in the postnatal brain maturation that leads to remission of dystonia at around puberty in mutant hamsters.
Tremor as a factor in prolonged reaction times of Parkinsonian patients
Authors: Staude G. , Wolf W. , Ott M. , Oertel W. H. , Dengler R. 
Published: May 2005

AbstractProlonged reaction times and tremor are symptoms of Parkinson's disease (PD). Recently, we showed the existence of a systematic phase relationship between tremor‐at‐rest and the onset of voluntary motor responses in PD patients. In the present study we investigated whether this phase relationship contributes to the prolongation of reaction time in PD. Eight PD patients with prominent tremor‐at‐rest and five age‐matched controls performed rapid stimulus‐evoked index finger abductions under isometric conditions. Force and surface electromyogram (EMG) signals from first dorsal interosseus muscle were recorded and analyzed off‐line by means of automatic routines. Reaction times of PD patients exhibited a significant dependence of mean values and variability on the current tremor phase at the onset of the voluntary motor response. Responses with an onset of contraction during the beginning of an EMG tremor burst were substantially delayed (on average 50 ms) and showed more variability in comparison to responses initiated at later times in the tremor cycle. This effect can be modeled by a simple gating process splitting the tremor cycle into two different system states that supports and inhibits the initiation of voluntary motor responses, respectively. We conclude that attraction of voluntary motor initiation to the tremor oscillator clearly contributes to prolongation of reaction time in PD.