bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation strategies for the determination of residues of explosives in soils using micellar electrokinetic capillary chromatography
Authors: Mussenbrock Elmar , Kleiböhmer Wolfgang 
Published: May 2005

AbstractMicellar electrokinetic capillary chromatography (MEKC) separation strategies for the determination of residues of explosives in soils are presented. Compared to former publications, the number of explosives determined was increased up to 24 compounds in which all EPA priority substances are included. Separation characteristics were investigated as a function of different organic modifiers. Using 1 vol% of methanol, separation was realized for all 24 compounds, including all of the isomers of the mono‐and dinitrotoluenes. Furthermore, the lipophilic and hydrophilic parts of the surfactant were varied, and the best separation characteristics were obtained with sodium dodecyl sulphate (SDS). Even the suitability of mixed micelles for the analysis of nitroaromatics was tested. With the help of mixed micelles consisting of SDS and the amphoteric surfactant SB‐12, separation of 22 out of 24 explosives was realized. With significantly changed selectivities, complete separation required less than 12 minutes.
Comparative study of colombian rue oils by high resolution gas chromatography using different detection systems
Authors: Stashenko E. E. , Villa H. S. , Combariza M. Y. 
Published: May 2005

AbstractVolatile secondary metabolites from different parts (flowers, leaves, stems, and roots) of Colombian rue (Ruta graveolens) were obtained by combined steam distillation‐solvent extraction. The various oils were analyzed by means of GC using FID, NPD, or MSD. The chemical composition of the oils extracted from the aerial parts differed drastically from those extracted from the roots. 3‐Pyrrolidinol, 1,4‐dimethylpiperazine, and various 1,3‐benzodioxole derivatives were detected in the Colombian rue oil for the first time.
Resolution of ampholytes focused in a natural pH gradient moving in a tapered capillary
Authors: Šlais K. 
Published: May 2005

AbstractChanges in the resolution of peaks of ampholytes during their migration and focusing in a natural pH gradient which moves electrophoretically in a tapered capillary are discussed. The influence of the capillary geometry on the needed potential drop as well as on the pressure drop accompanied by the renewing of the electrolytes is estimated. The expected performance of focusing according to the suggested model is related to that of focusing of the ampholytes in a pH gradient moving in a capillary of constant cross‐section.
Open crown ether polysiloxane stationary phases for capillary gas chromatography
Authors: Cai Lin‐Shuang , Wu Cai‐Ying , Han Hui‐Ming 
Published: May 2005

AbstractIn this paper, two new open crown ether polysiloxane stationary phases were prepared for capillary gas chromatography. Chromatographic characteristics, including column efficiency, operational temperature range, thermal stability, and polarity were studied. The open crown ether polysiloxane was found to have unique selectivity for alcohols, aromatic hydrocarbons, and nitrogen‐containing compounds. The separation mechanism and various thermodynamic parameters are discussed.
Preparation of silica porous‐layer open‐tubular columns using fused silica capillaries
Authors: Yun Hao , Markides Karin E. , Lee Milton L. 
Published: May 2005

AbstractWe report a simple method for the preparation of silica PLOT columns using fused silica capillaries. In this method, silica particles were suspended in a methylene chloride/pentane solution containing polymethylhydrosiloxane and passed through the capillary tubing. This caused the silica particles to be dynamically coated on the inner wall of the fused silica capillary. The column was dried and heated, which facilitated the simultaneous deactivation and bonding of a uniform mono‐layer of porous silica on the inner wall of the capillary tubing. These columns were used to separate light hydrocarbons, chlorinated hydrocarbons, and aromatic compounds.
Resolution effects of organic additives on the MEKC enantiomeric separations of tri aza aromatic ligand compounds of iron(II)
Authors: See Marjorie M. , Elshihabi Said , Burke John A. , Bushey Michelle M. 
Published: May 2005

AbstractWe have utilized micellar electrokinetic chromatography with sodium deoxycholate micelles to separate the enantiomers of bis(8‐((pyridine‐2‐methylene)amino)quinoline)iron(II) hexafluorophosphate, Fe(PMAQ)2(PF6)2, bis(8‐((pyridine‐2‐methylene)amino)lepidine iron(II) hexafluorophosphate, Fe(PMAL)2(PF6)2, and bis(1‐(2‐pyridinyl)ethylidine)‐8‐aminoquinoline iron(II) hexafluorophosphate, Fe(PEAQ)2(PF6)2. The influence of 13 water miscible organic additives on the resolution of each pair of enantiomers was investigated. Significant changes in resolution are seen depending upon the particular organic additive used in the separation buffer. In addition, the effects of acetone concentration on the resolution of these enantiomers in bile salt solution was investigated. Resolution for all three pairs of enantiomers is maximized in a buffer solution containing 15% acetone. © 1995 John Wiley & Sons, Inc.
Micro LC on cellulose triacetate (CTA): Influence of particle diameter and column temperature
Authors: Chen Jian , Steenackers Dirk , Sandra Pat 
Published: May 2005

AbstractFused silica columns (320 μm i.d.) were packed with 10 μm, 15–25 μm, and 25–40 μm microcrystalline cellulose triacetate (CTA) and the influence of the particle diameter on column efficiency was investigated. The dependence of retention, selectivity, resolution, and analysis time on column temperature was studied for the separation of several racemates on microcolumns packed with 15–25 μm CTA. © 1995 John Wiley & Sons, Inc.
Microwave extraction in analytical chemistry of pollutants: Chlorinated benzenes
Authors: Onuska Francis I. , Terry Ken A. 
Published: May 2005

AbstractThe microwave energy produced in a cavity of the magnetron was used to extract chlorinated benzenes from water samples. This dynamic extraction method employs a stream of helium. Results were compared with those obtained by liquid‐liquid and the large volume extractions. The microwave extraction provides results that are comparable with those obtained using other techniques, while offering the advantages of speed. The preconcentration factors are approx. 1000 and corresponding detection limits for 1 liter of water are in the pg/L range, when determination of individual polychlorinated benzene congeners is performed using HRGC/MS/ selected ion monitoring. © 1995 John Wiley & Sons, Inc.
In‐situ hydrolysis/methylation pyrolysis CGC for the characterization of polyaramides
Authors: Venema Arnold , Boom‐Van Geest Renie C. A. 
Published: May 2005

AbstractSome parameters influencing the in‐situ methylation by tetramethylammonium hydroxide (TMAH) during pyrolysis have been investigated with model compounds and polyaramides. Both pyrolysis temperature and excess TMAH (pH effect) influence the methylation of carboxy‐, aromatic amino‐, and hydroxyl‐functional groups. While the solvent of TMAH, i.e., methanol or water hardly influenced the methylation of the model compounds, the solvent effect was significant for the polyaramides. This can be explained by assuming a transesterification mechanism rather than hydrolysis/methylation. N‐methylation prior to the decomposition of polyaramides also may not be excluded. © 1995 John Wiley & Sons, Inc.
On‐line LC‐GC transfer via a hot vaporizing chamber and vapor discharge by overflow; increased sensitivity for the determination of mineral oil in foods
Authors: Grob Konrad , Bronz Marianne 
Published: May 2005

AbstractThe modified LC‐GC transfer technique with concurrent eluent evaporation reduces losses of volatile components. The LC fraction is transferred by the LC pump. Evaporation occurs in a heated capillary into which a piece of wire is introduced. Vapors are discharged by overflow. This enables the reduction of the oven temperature to the minimum that prevents recondensation and to obtain more efficient phase soaking for the retention of volatile solutes. The technique was applied to improve sensitivity of the analysis of mineral oil in foods. © 1995 John Wiley & Sons, Inc.
Parallel column gas chromatography
Authors: Owens Patrick M. , Loehle David W. , Scott Beverly S. , Gonzalez Rodney S. 
Published: May 2005

AbstractA parallel column gas chromatography (PCGC) methodology that simultaneously collects retention information on multiple stationary phases is presented. The multidimensional PCGC configuration links a precolumn in series with a set of parallel analytical columns (having different stationary phases) all connected to a single detector. GC peaks heartcut from the precolumn are detected as a series of peaks due to retention differences on parallel columns. This provides a GC retention pattern that is characteristic of the analyte, the stationary phase array, and the conditions of the analysis. PCGC peak patterns observed for groups of C8, C9, and C10 compounds are presented. The use of PCGC with infrared and mass spectral detectors is reported. A methodology to account for changes in GC operating parameters using relative retentions of analytes to internal standards is presented. The first use of thermodynamic retention parameters to model retention behavior on parallel analytical columns under different temperature profiles is presented. Retention predictions within 0.3‐0.6% of experimental values are reported. These results indicate that PCGC has potential as a general qualitative analysis tool. Future efforts to calibrate retention predictions, to transport PCGC results between instruments, and to optimize the number of parallel columns are proposed. © 1995 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
Aqueous alkylation of anions for static headspace sampling with analysis by capillary gas chromatography‐mass spectrometry
Authors: Mulligan Kevin J. 
Published: May 2005

AbstractThe formation of ethyl derivative from anions and the conjugate bases of weak acids through the reaction with ethyl p‐toluenesulfonate in strongly basic aqueous systems was used as a precursor to analysis by static headspace sampling with capillary gas chromatography‐mass spectrometry. A host of materials are amenable to the technique including: cyanide, butyrate, caproate, fluoroacetate, iodide, and phenol. These analytes were used to study the performance of the system in relation to the behavior of commercially obtained ethyl derivatives. 18‐Crown‐6 (1,4,7,10,13,16‐hexaoxacyclooctadecane) effectively catalyzes the reaction which appears to require the presence of high concentrations (5 M) of a basic salt, such as potassium carbonate. A 1:1 (molar) mixture of dibasic and tribasic potassium phosphate effectively substitutes for potassium carbonate and provides improved performance for fluoroacetate while reducing interferences such as diethyl carbonate. Quantitative yields were obtained in the concentration range 0.05‐2 mM, except for cyanide which produced propionitrile with an efficiency of 55–80%. Fructose, at the 10% w/v level, exerted little influence upon the reaction. Calibration curves (selected ion monitoring) were linear between 0.001 and 1 mM. This approach extends the applicability of static headspace sampling and offers a potentially simple alternative to ion chromatography for complicated matrices. It should prove useful for confirming results obtained by other methods or for screening poorly characterized samples. © 1995 John Wiley & Sons, Inc.
Separation and fluorescence enhancement of dansyl amino acids assisted by γ‐cyclodextrin and bovine serum albumin as mobile phase additive in microcolumn liquid chromatography
Authors: Takeuchi Toyohide , Miwa Tomoo , Chu Jianhua 
Published: May 2005

AbstractThe effects of γ‐cyclodextrin and bovine serum albumin as mobile phase additives on fluorescence intensity and retention of dansyl amino acids (Dns‐AAs) have been examined in microcolumn liquid chromatography. Polymercoated mixed‐functional silica packings were employed for the separation column. The concentrations of the additives, acetonitrile, and buffer affected the signal intensity and retention of DNA‐AAs. The use of the mobile phase additives improved the detection limits by a factor of as much as 7.4. © 1995 John Wiley & Sons, Inc.
Evaluation of a spatial scanning laser fluorometric detector for capillary electrophoresis: Application to studies of band migration and dispersion
Authors: Clark Brian K. , Sepaniak Michael J. 
Published: May 2005

AbstractWe report herein the development and evaluation of modified capillary electrophoresis instrumentation with laser fluorometric detection which allows for the convenient and precise translation of the detection zone along the length of the separation column. This instrumentation is utilized for fundamental studies of band dispersion, analyte mobility alterations, sample stacking, and the determination of diffusion coefficients. The feasibility of using this instrumentation to improve the signal/noise ratio and decrease analysis time is also presented. DNA restriction digest separations employing soluble polymer buffer systems with oncolumn fluorescent labeling was used to illustrate the unique advantages of this experimental design.
Associative learning in degenerative neostriatal disorders: Contrasts in explicit and implicit remembering between Parkinson's and huntington's diseases
Authors: Sprengelmeyer R. , Canavan A. G. M. , Lange H. W. , Hömberg V. 
Published: May 2005

AbstractThe performances of 12 patients with Parkinson's disease (PD), 16 with Huntington's disease (HD), and young and old healthy controls were assessed on a number of tests of verbal and nonverbal declarative memory, on a test of nonmotor conditional associative learning (words and colors), and on a number of reaction time (RT) tasks. The RT tasks consisted of cued simple and choice reactions. The relationship between the precue and the imperative stimulus in the S1–S2 paradigm was nonarbitrary in the first series and arbitrary in the second series. The series with arbitrary S1–S2 associations was repeated across two successive blocks of trials. The rationale of the study was to investigate the function of the basal ganglia “complex loop,” and it was postulated that HD patients would show greater deficits because of greater involvement of the caudate nucleus. The patients with HD had the slowest RTs. Across the two blocks with arbitrary S1–S2 associations, the patients with HD but not PD nevertheless showed evidence of learning in their precued RTs. In contrast, the patients with PD were better able to remember the associations in free recall than were the HD patients. It is concluded that patients with PD have relatively greater deficits in procedural learning, whereas those with HD have relatively more impairments in declarative memory, and the greater level of cognitive impairment in HD overall is interpreted as being due to more serious damage to the caudate loop.
The abnormality of N30 somatosensory evoked potential in idiopathic Parkinson's disease is unrelated to disease stage or clinical scores and insensitive to dopamine manipulations
Authors: Onofrj M. , Fulgente T. , Malatesta G. , Ferracci F. , Thomas A. , Curatola L. , Bollettini F. , Ragno M. 
Published: May 2005

AbstractWe recorded short latency somatosensory evoked potentials (SEPs) to median nerve stimuli in 40 patients affected by idiopathic Parkinson's disease (PD) classified from I to IV on the Hoehn and Yahr disability scale. SEPs were recorded before and after chronic administration of L‐Dopa and bromocriptine, before and after acute administration of L‐Dopa. Fourteen patients experiencing wearing off and dystonic‐dyskinetic disturbances were recorded during the occurrence of these oscillations of their clinical status. Absent or reduced N30 components were found in 32.5% of patients. SEPs were not modified by acute or chronic administration of L‐Dopa or bromocriptine or during off and dystonic or dyskinetic conditions. Multiple correlations of N30 with scores of the Unified Parkinson's Disease Rating Scale showed that N30 abnormality did not classify patient with prominent clinical features, nor did it predict the outcome of treatment.
Effect of cisapride on response fluctuations in Parkinson's disease
Authors: Djaldetti Ruth , Koren Maya , Ziv Ilan , Achiron Anat , Melamed Eldad 
Published: May 2005

AbstractImpaired gastric emptying may be the cause for some response fluctuations in Parkinson's disease (PD), especially the “delayed‐on” and “no‐on” phenomena. Cisapride is a prokinetic drug that enhances gastric emptying by releasing acetylcholine from the myenteric plexus. Tolerability and safety as well as efficacy of cisapride was studied in an open‐label trial on 15 fluctuating PD patients. Twelve patients had “delayed‐on” and six had “no‐on” phenomena. They filled out daily diaries on times of levodopa intake and of turning “on” and “off” for 1 week on levodopa alone and for an additional week of pretreatment with cisapride, 30 min before early morning, early afternoon, and late evening doses of levodopa. Cisapride significantly shortened latency to “on” from 60 ± 20 to 45 ± 19 min after the morning dose and from 63 ± 17 to 47 ± 22 min after the evening doses. Patients with “no‐on” phenomenon had a decreased number of dose failures from 23 before to nine during cisapride treatment. The drug was well tolerated, with no important side effects. Our study supports the role of impaired gastric emptying in some subtypes of motor fluctuations and indicates that they may be improved by prokinetic drugs.
International guide to drugs for Parkinson's disease
Authors: Oertel W. H. , Dodel R. C. 
Published: May 2005

AbstractPharmacotherapy of Parkinson's disease (PD) has become so effective that patients with PD can enjoy a nearly normal life, including travel for several years. The degree of international travel of patients with PD and in particular the recent increased coordination between health systems in the European community call for a detailed information on the different antiparkinsonian drugs available worldwide. To provide an overview for physicians and patients on the diversity of preparations available in the different countries, we compiled the most commonly used substances along with their size of dosage and formula in an international guide to drugs for PD.
Unique myoclonic pattern in corticobasal degeneration
Authors: Brunt Ewout R. P. , van Weerden Tiemen W. , Pruim Jan , Lakke Johannes W. P. F. 
Published: May 2005

AbstractWe describe two similar patients with a clinical diagnosis of corticobasal ganglionic degeneration (CBGD). After a period of increased action tremor, both patients developed a fixed posture in the right arm with a slow rhythmic myoclonus, which appeared to be caused by trains of highly synchronized and stimulus sensitive myoclonic discharges. Resetting of the spontaneous myoclonic discharges by peripheral and central stimulation and a jerklocked cortical potential were demonstrated in one case. The somatosensory evoked potentials (SEPs) showed abnormal parietal curves with small N20–P25 amplitudes and without giant SEP characteristics. The latencies of the cortical event and of the late responses, and the duration and distribution of the discharges compare best with those of the cortical reflex type of myoclonus. Localized parietal cortical damage, as indicated by clinical evidence and imaging techniques, may well explain the absence of a giant SEP in these patients with CBGD.
Reversible parkinsonian syndrome complicating cysticercus midbrain encephalitis
Authors: Verma Ashok , Berger Joseph R. , Bowen Brian C. , Sanchez‐Ramos Juan 
Published: May 2005

AbstractWe describe a clinical picture similar to Parkinson's disease in a patient with midbrain encephalitis due to cysticercosis. The clinical, radiographic, and cerebrospinal fluid findings suggested an inflammatory reaction to a dying cyst that involved midbrain structures. The encephalopathy appeared to worsen temporarily after the institution of anticysticercus therapy. A discordance between worsening parkinsonian symptoms and improving pyramidal features was noted. Virtually a complete clinical recovery eventually ensued.
Defects of cytochrome c oxidase in the substantia nigra of Parkinson's disease: An immunohistochemical and morphometric study
Authors: Itoh Kyoko , Weis Serge , Mehraein Parviz , Müller‐Höcker Josef 
Published: May 2005

AbstractDefects of respiratory chain complexes were considered as possible pathogenetic mechanisms in Parkinson's disease (PD). Changes of cytochrome c oxidase (COX) in four different nuclei of the substantia nigra of 8 PD cases and 10 age‐matched controls were investigated by means of morphometry and immunohistochemistry. Pigmented neurons with COX defects were randomly distributed within the four nuclei of PD cases, but only in the posterolateral nucleus was the numerical density of pigmented neurons with COX defects significantly increased compared with controls. The numerical density of pigmented neurons without COX defects was significantly reduced in the anteromedial, anterointermediolateral, and posterolateral nuclei in PD. The cell size of pigmented neurons with and without COX defects was significantly diminished in the anteromedial and posterolateral nuclei of PD cases. It is suggested that complex IV defects in nigral neurons are most probably a result of accelerated aging, but are least likely to be a primary aspect of the pathogenetic processes occurring in PD.
Levodopa induces apoptosis in cultured neuronal cells—A possible accelerator of nigrostriatal degeneration in Parkinson's disease?
Authors: Ziv Ilan , Zilkha‐Falb Rina , Offen Daniel , Shirvan Anat , Barzilai Ari , Melamed Eldad 
Published: May 2005

AbstractApoptosis is an active, intrinsic cell suicide program. We recently suggested that it may have a role in the death of nigrostriatal dopaminergic neurons in Parkinson's disease (PD). We now report that levodopa, the current major therapy for PD, is a potent inducer of apoptosis in cultured postmitotic chick sympathetic neurons. Levodopa, in a concentration range of 0.01–0.3 mM, caused the characteristic apoptotic cascade of cell shrinkage, massive membrane blebbing, and nuclear fragmentation, as evident by nuclear flow cytometry and fluorescence microscopy. Levodopa‐induced apoptosis was inhibited by antioxidants, indicating that it may be mediated by autooxidation‐reactive species. Levodopa treatment for PD may therefore constitute an additional challenge for the defective apoptosis‐inhibiting systems in the nigrostriatal neurons. Despite reassuring data from some, but not all, previous studies, these findings suggest that the possible in vivo toxic effects of levodopa on the survival of the remaining nigral neurons should be further explored.