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  • Articles  (1,251)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 10 (1972), S. 82-90 
    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Precipitation ; Kinetics ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La cinétique de la formation et de la transformation des précipités de phosphate de calcium, obtenus en mélangeant de volumes égaux de solutions à 6×10−3 M de calcium total et/ou phosphate total est étudiée à 25°C. Les solutions de phosphate sont préajustées à un pH de 7.4. Les changements de pH et de turbidité des solutions sont suivis simultanément en fonction du temps. Les précipités sont isolés à des intervalles de temps variables et caractérisés par diverses méthodes physico-chimiques. Initialement un précipité avec un rapport molaire Ca/P de 1.5, amorphe aux rayons X et en diffraction électronique, est formé. Le spectre IR indique la présence de PO 4 3− et de HPO 4 2− . Après une période métastable, on observe la précipitation d'un matériel cristallin dans ou sur la phase amorphe. Vingt quatre heures après préparation de l'échantillon les précipités présentent surtout les caractères du phosphate octocalcique.
    Abstract: Zusammenfassung Die Kinetik der Bildung und Transformation von Calciumphosphat-Niederschlägen wurde bei 25°C untersucht. Es wurden dazu gleiche Volumen von Lösungen gemischt, bei einer Konzentration von 6×10−3M totales Calcium und/oder totales Phosphat. Die Phosphatlösungen wurden zuerst auf pH 7,4 eingestellt. Veränderungen des pH und Trübung der Lösungen wurden gleichzeitig als eine Funktion der Zeit aufgezeichnet. Niederschläge wurden in verschiedenen Zeitintervallen isoliert und mit verschiedenen physiko-chemischen Methoden charakterisiert. Am Anfang wurde ein Niederschlag mit einem molaren Ca/P-Verhältnis von 1,5, im Röntgenbild und in der Elektronendiffraktion amorph, gebildet. Infrarotspektren deuteten die Anwesenheit von PO 4 3− - und HPO 4 2− -Ionen an. Nach einer metastabilen Periode erfolgte ein Niederschlag aus kristallinem Material innerhalb oder auf der amorphen Substanz. 24 Std nach der Herstellung der Proben zeigten die Niederschläge in der Hauptsache die Charakteristiken von Octocalciumphosphat.
    Notes: Abstract The kinetics of the formation and transformation of calcium phosphate precipitates obtained by mixing equal volumes of solutions, 6×10−3 M in total calcium and/or total phosphate was investigated at 25°. The phosphate solutions were preadjusted to pH 7.4. Changes of the pH and turbidity of the solutions were followed simultaneously as a function of time. Precipitates were isolated at various time intervals and characterized by different physicochemical methods. Initially a precipitate with a molar Ca/P ratio of 1.5, amorphous to X-ray and electron diffraction was formed. IR spectra indicated the presence of PO 4 3− and HPO 4 2− ions. After a period of metastability, precipitation of a crystalline material within or upon the amorphous matter occurred. Twenty four hours after sample preparation the precipitates showed mainly the characteristics of octacalcium phosphate.
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  • 2
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    Calcified tissue international 16 (1974), S. 145-152 
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
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  • 3
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    Calcified tissue international 23 (1977), S. 13-17 
    ISSN: 1432-0827
    Keywords: Dental calculus ; Glycopeptide ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for the isolation and purification of a sulphated glycopeptide from human supragingival calculus. The compound was isolated after using EDTA treatment, 2 M CaCl2 extraction, proteolytic digestion, ethanol precipitation, and finally purified by DEAE cellulose chromatography. It migrated as a single component on cellulose acetate electrophoresis, and chemical and infrared spectral analysis showed the presence of covalently attached sulphate groups. The sulphated glycopeptide was distinguished from being a sulphated glycosaminoglycan.
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  • 4
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
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  • 5
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    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 6
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    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
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  • 7
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    Aquatic sciences 51 (1989), S. 108-128 
    ISSN: 1420-9055
    Keywords: Chemistry ; mountain lakes ; silica ; acidity ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 μeq 1−1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.
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  • 8
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    Accreditation and quality assurance 5 (2000), S. 409-413 
    ISSN: 1432-0517
    Keywords: Key words Metrology ; Comparisons ; Chemistry ; Standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.
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  • 9
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    Calcified tissue international 14 (1974), S. 3-14 
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Abstract: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notes: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
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  • 10
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    Calcified tissue international 7 (1971), S. 150-162 
    ISSN: 1432-0827
    Keywords: Uranium ; Bone ; Distribution ; Fission ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une concentration moyenne de 2.4×10−8 g U/g de cendre a été obtenue à partir de l'os humain normal. La microdistribution de l'uranium dans l'os indique que cet élément est surtout limité à surface de l'endoste et, en particulier, aux surfaces de l'os lamellaire et aux parois des canaux de Havers, ouverts dans l'os corticol. Cette répartition suggère que l'uranium se présente sous une forme chimique impropre à son incorporation dans l'apatite osseux: il ne semble donc pas exister une distribution diffuse significative de l'uranium dans l'os.
    Abstract: Zusammenfassung Eine mittlere Konzentration von 2,4×10−8 g Uran/g Asche wurde in normalen menschlichen Knochen gefunden. Die Feinverteilung von Uran im Knochen zeigt, daß dieses Element hauptsächlich an der endostalen Oberfläche vorkommt, insbesondere an der Oberfläche des trabeculären Knochens und an den Wänden der offenen Haversschen Kanäle im kortikalen Knochen. Diese Verteilung läßt vermuten, daß Uran in einer chemischen Form vorliegt, welche sich für den Einbau in das Knochenapatit nicht eignet. Daraus folgt, daß keine signifikante diffuse Verteilung des Urans innerhalb des Knochens vorliegt.
    Notes: Abstract A mean concentration of 2.4×10−8 g U/g ash has been obtained for normal human bone The microdistribution of uranium in bone indicates that this element is mainly restricted to endosteal surfaces; in particular the surfaces of trabecular bone and the walls of open Haversian canals in cortical bone. This distribution suggests that uranium is present in a chemical form that is not acceptable for incorporation into bone apatite and consequently there does not appear to be a significant diffuse distribution of uranium throughout bone.
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  • 11
    ISSN: 1432-0827
    Keywords: Morphology ; Glycosaminoglycans ; Cartilage ; Chemistry ; Audioradiography ; Healing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une perte de substance ostéo-cartilagineuse, de taille limitée et identique, est réalisée chez le lapin adulte et la cicatrisation est étudiée histologiquement et par autoradiographie après marquagein vitro au35S-sulfate. Une analyse microchimique est pratiquée pour le contenu et la composition en glycosaminoglycanes. 1. Entre la première semaine et la 4ème et 8ème semaine, un tissu conjonctif non-métachromatique se différencie en un cartilage métachromatique et la quantité de sulfate de chondroitine augmente de façon significative aux dépens des glycoprotéines. 2. Jusqu'à la 4ème semaine, la perte de substance est surtout comblée par de l'os néoformé: après cette période, la région est comblée au delà de la limite de la surface articulaire. 3. Le cartilage hyalin, ressemblant morphologiquement, autoradiographiquement et chimiquement au cartilage articulaire, en ce qui concerne la distribution en glycosaminoglycanes, constitute la surface articulaire de la perte de substance comblée dans un tiers des cas après 8 semaines. Le cartilage hyalin s'observe surtout dans les régions où de l'os néoformé a comblé la cavité médullaire. 4. Dans les deux tiers des cas, après 8 semaines, les surfaces articulaires des zones comblées comportent, non seulement du cartilage, mais aussi du tissu fibreux se formant essentiellement sur les parties latérales et dans les régions, où la cavité médullaire, fliant face, à la surface articulaire, n'a pas été comblée par du tissue osseux. La fraction glycoprotéique augmente par rapport à la fraction chondroitine sulfate. 5. Dans la majorité des cas, après 20 semaines, le cartilage néoformé subit des phénomènes dégénératifs, qui se traduisent par une diminution en chondroitine sulfate.
    Abstract: Zusammenfassung Bei ausgewachsenen Kaninchen wurde ein begrenzter, standardisierter, osteochondraler Defekt hervorgerufen, und das regenerierte Gewebe wurde histologisch und autoradiographisch durch Markierung in vitro mit35S-Sulfat und durch mikrochemische Bestimmung des Gehaltes und der Zusammensetzung der Glykosaminglykane untersucht. Die wichtigsten Befunde waren: 1. Zwischen 1 und 4–8 Wochen veränderte sich nichtmetachromatisches Bindegewebe zu metachromatisch gefärbtem Knorpel, und der Anteil an Chondroitin-Sulfat nahm auf Kosten der Glykoproteine signifikant zu. 2. Bis zu 4 Wochen war der Hauptteil des defekten Gebietes mit neugebildetem Knochen gefüllt; nach dieser Zeit lag dieser Bezirk oberhalb der Verknöcherungsgrenze in Richtung der Gelenkoberfläche. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 4. Nach 8 Wochen bestanden Teile der Gelenkoberfläche des Defektes in zwei Dritteln der Fälle nicht nur aus Knorpel, sondern auch aus fibrösem Gewebe, welches vor allem in den seitlichen Teilen des Defektes und an Stellen vorlag, wo die Markhöhle gegenüber der Gelenkoberfläche nicht mit Knochengewebe verschlossen worden war. Die Glykoproteinfraktion nahm im Vergleich zur Chondroitin-Sulfatfraktion zu. 5. Nach 20 Wochen zeigten sich in den meisten Fällen bei neugebildetem Knorpel degenerative Veränderungen, welche durch eine gewisse Abnahme des Chondroitin-Sulfats wiedergegeben wurden.
    Notes: Abstract A limited, standardized osteochondral defect was created in adult rabbits and the regenerated tissue was examined histologically and autoradiographically after labellingin vitro with35S-sulphate, and microchemically for its content and composition of glycosaminoglycans. The principal findings were: 1. Between 1 week and 4 to 8 weeks, non-metachromatic connective tissue differentiated to metachromatically stained cartilage, and the proportion of the chondroitin sulphate increased significantly at the expense of the glycoproteins. 2. Up to 4 weeks, the major part of the defect area was filled with newly formed bone; after this time, the area lay above the level of the “tidemark”, towards the articular surface. 3. Hyaline cartilage with morphological, autoradiographic and chemical resemblance to the articular cartilage in terms of the distribution of glycosaminoglycans constituted the articular surface of the defect area in one-third of the cases at observation times after 8 weeks. Hyaline cartilage was observed mainly in areas where newly formed bone had closed the medullary cavity. 4. In two-thirds of the cases, after 8 weeks, parts of the articular surface of the defect consisted not only of cartilage but also of fibrous tissue, occurring mainly in the lateral parts of the defect and in areas where the medullary cavity facing the articular surface had not been sealed by bone tissue. The glycoprotein fraction increased relative to the chondroitin sulphate fraction. 5. In most cases after 20 weeks, newly-formed cartilage underwent degenerative changes, which were reflected in some reduction of the chondroitin sulphate.
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  • 12
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    Calcified tissue international 8 (1971), S. 228-236 
    ISSN: 1432-0827
    Keywords: Skin ; Calcinosis ; Keratin ; Chemistry ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des études histologiques antérieures ont montré que le follicle pileux est particulièrement susceptible de se calcifier, lorsque la peau de rats hypercalcémiques est lésée. Des analyses chimiques et par diffraction aux rayons X du follicule ont confirmé ce résultat. — En se basant sur l'augmentation du calcium et du phosphore, les calcifications débutent dans le tissue folliculaire 6–12 h après une blessure d'intensité moyenne de la peau de rats, ayant reçu du dihydrotachysterol (DHT), et 24–48 h après une blessure similaire chez des rats non injectés. Les diagrammes de diffraction aux rayons X sont diffus. Trois heures après la blessure, on note une augmentation du calcium du tissu folliculaire qui ne semble pas en rapport avec le DHT qui traduit probablement une liaison de calcium plutôt qu'un dépot minéral.
    Abstract: Zusammenfassung Frühere histologische Untersuchungen haben gezeigt, daß der Haarfollikel besonders anfällig für Verkalkungen ist, wenn die Haut von hypercalcämischen Ratten verletzt wird. Dieses Resultat wurde nun durch direkte chemische Bestimmungen und Röntgendiffraktions-analysen von Follikelgewebe bestätigt. Aufgrund der erhöhten Calcium- und Phosphatwerte kann gesagt werden, daß nach einer leichten Quetschung der Haut von Ratten, die mit Dihydrotachysterol (DHT) behandelt wurden, im Haarfollikelgewebe nach 6–12 Std Mineral-ablagerungen stattfanden, wogegen Kontrollratten mit der gleichen leichten Hautverletzung diese Ablagerungen erst nach 24–48 Std zeigten. Röntgendiffraktionsanalysen ergaben ein diffuses Apatit-Muster. Innerhalb 3 Std nach der Verletzung wurde ein Anstieg des Calcium-gehaltes im Follikelgewebe beobachtet, der nicht im Zusammenhang mit der DHT-Behandlung stand, also nicht eine Mineralablagerung, sondern eher eine Bindung von Calcium widerspiegelte.
    Notes: Abstract Previous histological investigations have shown that the hair follicle is particularly susceptible to mineralization when the skin of hypercalcaemic rats is injured. Direct chemical and X-ray diffraction analyses of follicle tissue have now confirmed this finding. As judged by increases in both calcium and phosphorus, mineral deposits began to form in hair follicle tissue 6–12 h after a mild crush injury to the skin of rats dosed with dihydrotachysterol (DHT), and 24–48 h after a similar injury to the skin of non-dosed rats. X-ray diffraction gave a diffuse apatite pattern. Within 3 h of injury there was a rise in the calcium content of follicle tissue which was not related to DHT-dosing and which was probably a reflection of calcium binding rather than mineral deposition.
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  • 13
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    Calcified tissue international 8 (1971), S. 304-319 
    ISSN: 1432-0827
    Keywords: Chemistry ; Calcium ; Phosphate ; Solubility ; Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un programme d'ordinateur a été mis au point pour calculer les activités ioniques du calcium et l'orthophosphate dans un grand nombre de solutions. Dans le cas de solutions synthétiques, les calculs sont vérifiés en comparant les valeurs de pH, obtenues par ordinateur, avec celles observées expérimentalement. Des essais de ce type, avec des solutions possèdant des concentrations de calcium et d'orthophosphate trouvées dans les liquides biologiques et à des valeurs de pH variant de 3.00 à 10.00, indiquent que le programme est adapté pour des applications biologiques. Le programme n'est pas effectif pour des solutions, dans les lesquelles l'ion bromure est la source principale de la force ionique, sans doute, par manque d'équation étendue de Debye-Hückel dans ces circonstances. Aucune formation de complexe de phosphate de sodium n'a été notée à des concentrations biologiques normales.
    Abstract: Zusammenfassung Es wurde ein Computer-Programm ausgearbeitet, um die Ionenaktivitäten von Calcium und Orthophosphat in einer breiten Varietät von Lösungen zu berechnen. Die Berechnungen wurden bei synthetischen Lösungen durch Vergleiche zwischen den auf diese Weise errechneten pH-Werten und den experimentell gefundenen kontrolliert. Diese Art Kontrollen mit Calcium-und Orthophosphatkonzentrationen, wie sie in biologischen Flüssigkeiten gefunden werden, und mit pH-Werten zwischen 3,0 und 10,0 wies darauf hin, daß das Programm für biologische Anwendungen geeignet war. Das Programm konnte nicht benützt werden für solche Lösungen, bei welchen hauptsächlich das Bromidion zur Einstellung der Ionenstärke verwendet wurde, vermutlich weil die erweiterte Debye-Hückel-Gleichung unter diesen Umständen nicht anwendbar ist. Die Bildung eines Natriumphosphat-Komplexes unter normalen biologischen Konzentrationen konnte nicht nachgewiesen werden.
    Notes: Abstract A computer program has been designed to calculate the ionic activities of calcium and orthophosphate in a wide variety of solutions. In the case of synthetic solutions the calculations were checked by comparing the computed pH values with those observed experimentally. Tests of this type with solutions having the concentrations of calcium and orthophosphate found in biological fluids and with pH values ranging from pH 3.0–10.0 indicated that the program was suitable for biological applications. The program was not effective for solutions in which the bromide ion was a principal source of ionic strength probably because of the failure of the extended Debye-Hückel equation under those circumstances. No evidence for the formation of any sodium phosphate complex at normal biological concentrations could be found.
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  • 14
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    Calcified tissue international 10 (1972), S. 171-197 
    ISSN: 1432-0827
    Keywords: Amorphous ; Crystalline ; Calcium phosphate ; Chemistry ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des échantillons non lavés de phosphate de calcium amorphe (ACP) contiennent une fraction labile, non remplaçable, riche en phosphate acide avec un rapport Ca/P faible: cette fraction est perdue de façon irréversible au cours du lavage. De l'ACP frais, précipité entre pH 6.6–10.6, varie dans un rapport molaire Ca/P de 1.18 à 1.50 et dans un rapport HPO 4 2− /P total de 33.0% à 10.1%. A pH 7.40, de l'ACP frais a un rapport molaire Ca/P de 1.36±0.02 et contient 22.8 (±2.2)% HPO 4 2− . Les résultats obtenus avec du précipité non lavé ne peuvent s'expliquer par du Ca2+ emprisonné et de l'HPO 4 2− ou du Na+, Cl− et CO 3 2− exogènes. Les phosphates de calcium amorphes constituent une classe de sels ayant des caractères chimiques variables et des propriétés physiques identiques, comparables au verre. Le CaHPO4·xH2O non cristallin peut être un ACP, surtout au cours des phases précoces de formation. A des pH physiologiques, l'ACP se transforme en petits cristaux applatis contenant de fortes quantités de phosphate acide facilement remplaçable. Le fait de laver la couche de surface produit un changement chimique dans les nouveaux cristaux: des cristaux non lavés donnent des diagrammes de diffraction d'apatite peu cristallins, ainsi que des spectres infra-rouges peu nets, intermédiaires entre des apatites et du phosphate octocalcique. Des explications structurales sont proposées et les compositions minérales amorphe/cristalline de l'os et du cartilage sont recalculées.
    Abstract: Zusammenfassung Ungewaschene Proben von amorphem Calciumphosphat (ACP) enthalten eine unersetzliche labile Fraktion, welche reich an saurem Phosphat ist und ein niederes Ca/P-Verhältnis hat und welche während des Waschprozesses unwiderruflich verloren geht. Natives ACP, welches im pH-Bereich 6,6–10,6 ausgefällt wurde, variierte im molaren Ca/P-Verhältnis zwischen 1,18 und 1,50 und in HPO 4 2− /totales P zwischen 33,0 und 10,1%. Bei pH 7,40 hatte natives ACP ein molares Ca/P-Verhältnis von 1,36±0,02 und enthielt 22,8 (±2,2)% HPO 4 2− . Die Werte beim ungewaschenen Niederschlag rühren weder von aus dem Überstand aufgenommenem Ca2+ und HPO2−, noch von außen kommendem Na+, Cl− und CO 3 2− her. Die amorphen Calciumphosphate werden als eine Klasse von Salzen erkannt, welche veränderliche chemische, aber identische glasartige physicochemische Eigenschaften haben. Nicht kristallines CaHPO4·xH2O kann auch ein ACP sein, besonders in den frühen Bildungsstadien. Bei physiologischem pH verwandelt sich ACP in kleine plattenförmige Kristalle, welche große Mengen von leicht ersetzbarem saurem Phosphat enthalten. Das Waschen dieser Oberflächenschicht erzeugte chemische Veränderungen in den resultierenden Kristallen; ungewaschene Kristalle zeigten ein Diffraktionsmuster, das nur schwach demjenigen des kristallinen Aspatites glich, aber ein schlecht aufgelöstes Infrarotspektrum, welches zwischen Apatit und Octocalciumphosphat war. Es werden strukturelle Erklärungen für alle diese Phenomena diskutiert, und revidierte amorph/kristalline Mineralzusammensetzungen von Knochen und Knorpel wurden neu berechnet.
    Notes: Abstract Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca/P molar ratio from 1.18 to 1.50 and in HPO 4 2− /total P from 33.0% to 10.1%. At pH 7.40, native ACP had a Ca/P molar ratio of 1.36±0.02 and contained 22.8 (±2.2)% HPO 4 2− . Unwashed precipitate data could not be attributed to either trapped supernatant Ca2+ and HPO 4 2− or extraneous Na+, Cl−, and CO 3 2− . The amorphous calcium phosphates are recognized as a class of salts having variable chemical but identical glass-like, physicochemical properties. Non-crystalline CaHPO4·xH2O may also be an ACP, especially during early formative stages. At physiological pH, ACP transforms to small platy crystals containing large amounts of readily-replaceable acid phosphate. Washing this surface layer produced chemical alterations in the resultant crystals; unwashed crystals had poorly-crystalline apatitic diffraction patterns but exhibited poorly-resolved infrared spectra intermediate between apatite and octacalcium phosphate. Structural explanations for all these phenomena are discussed, and revised bone and cartilage amorphous/crystalline mineral compositions have been re-calculated.
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    Calcified tissue international 23 (1977), S. 39-44 
    ISSN: 1432-0827
    Keywords: Dental cementum ; Collagen ; Protein ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([α1(I)]2α2) accounted for more than 90% of the organic matrix, while Type III collagen ([α1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from α1(I) and α2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.
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  • 16
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    Calcified tissue international 23 (1977), S. 87-94 
    ISSN: 1432-0827
    Keywords: Calcium ; Osteoporosis ; Lactation ; Chemistry
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    Topics: Biology , Medicine , Physics
    Notes: Summary The calcium homeostatic mechanism was challenged in adult female rats by feeding them a calcium-deficient diet containing oxalate, and by subjecting them to pregnancy and lactation. The regimen caused a substantial weight loss, especially in those animals which reared their young well. Severe hypocalcaemia was observed in the lactating rats. Serum-P was slightly elevated. The content of hydroxyproline in serum was considerably elevated, reflecting the degree of calcium deprivation. Serum proteins were least influenced. The calcium depriving regimen reduced the growth of long bones, but did not stop it. The ash content of the bones was considerably reduced, the degree of reduction depended on the degree of calcium deprivation. Ash as percentage of total bone organ was reduced, but not to the same extent as total ash. Analyses of different parts of femur showed that the proximal and distal parts had lost more bone mineral than the diaphyseal shaft. The ash content of cortical bone tissue from the femur was estimated by a volumetric method. No differences were observed between test groups and controls, indicating that no measurable amounts of bone mineral had been removed from the walls of the vascular canals or by osteocytic osteolysis. Planimetric determinations on cross sections from femora disclosed that a great amount of bone had been removed from the endosteal surface of the diaphysis, while the periosteal surface demonstrated reduced bone apposition.
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  • 17
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    Calcified tissue international 8 (1971), S. 197-210 
    ISSN: 1432-0827
    Keywords: Fluorescence ; Calcium ; Collagen ; Chemistry ; Bone ; Dentine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des composants fluorescents de l'os et la dentine sont séparés des hydrolysats alcalins de leur marice sur des colonnes Sephadex C25 CM d'échange cationique. Les concentrations en fluorescence et le spectre d'excitation (λ max 330 nm) et d'émission (λ max 395 nm) sont les mêmes que ceux observés au niveau des matrices intactes et gélatinisées. Les paramètres de fluorescence ne sont pas altérés par hydrolyse. La filtration sur gel à l'aide de colonnes Sephadex G 10 perment de différencier le matériel isolé en deux composants, ayant la même fluorescence et la même absorption UV. La fluorescence est indépendante de pH de 3.5–9.5. Des études de dialyse et de filtration sur gel de matrices gélatinisées indiquent une association étroite du matériel fluorescent avec les chaines polypeptidiques de collagène.
    Abstract: Zusammenfassung Fluorescierende Bestandteile aus Knochen und Dentin wurden in Sephadex C25 CM Kationen-Austauschersäulen von alkalischen Hydrolysaten ihrer Matrices getrennt. Die Fluorescenzintensitäten sowie die Erregungs- (λ max 330 nm) und Emissions- (λ max 395 nm) Spektren waren dieselben wie bei intakten und gelatinisierten Matrices. Die Fluorescenzparameter wurden durch die Hydrolyse nicht verändert. Eine Gelfiltration über Sephadex-G10-Säulen trennte das isolierte Material in 2 Komponenten auf, welche gleiche Fluorescenz- und UV-Absorptionseigenschaften zeigten. Im pH-Bereich zwischen 3,5 und 9,5 war die Fluorescenz unabhängig vom pH. Dialysierversuche sowie Gelfiltrationsexperimente mitden gelatinisierten Matrices zeigten eine starkgefügte Bindung des fluorescierenden Materials mit den Polypeptidketten des Kollagens.
    Notes: Abstract Fluorescent components in bone and dentine were separated from alkaline hydrolysates of their matrices on Sephadex C25 CM cationic exchange columns. The fluorescence levels, and the excitation (λ max 330 nm) and emission (λ max 395 nm) spectra, were the same as those observed in the intact and gelatinised matrices. The fluorescence parameters were unaltered by the hydrolysis procedure. Gel filtration on Sephadex G. 10 columns further resolved the isolated material into two components with the same fluorescence and UV absorption properties. The fluorescence was independent of pH over the range 3.5–9.5. Dialysis and gel filtration studies on the gelatinised matrices indicated a firmly-bonded association of the fluorescent material with the collagen polypeptide chains.
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  • 18
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    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Keywords: Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Abstract: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notes: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
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  • 19
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    Calcified tissue international 13 (1973), S. 259-270 
    ISSN: 1432-0827
    Keywords: Fluorapatite ; Exchange ; Chemistry ; Crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un échantillon minéral provenant de Burgess, Canada s'est révélé être un speciment exceptionnellement pur de fluoroapatite après analyse chimique et cristallographique. La composition globale de cet échantillon est la suivante: $$(Ca^2 )9.98(Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )0.02(PO_4^{3 - } )5.98(HCO_3^ - ,CO_3^{2 - } )0.02(F^ - )2$$ . L'axe cristallographique C est de 6.865 A et l'axe a de 9.374 A. Des expériences d'échanges réalisés à l'aide de45Ca,32P et18F indiquent la présence de gros cristallites de surface spécifique de l'ordre de 1 m2/g. Il apparait que l'interprétation physique des processus d'échange ne nécessite pas l'existence de compartiments séparés, avec chacun son propre facteur cinétique, les échanges semblent être simplement liés à un changement exponentiel dans l'énergie libre de la réaction. Pour la réaction suivante: $$(Ca)_5 (PO_4 )_3 OH solide + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F solide + (OH^ - )$$ , la constante thermodynamique de 101.26 a été calculée, suggérant que le fluorapatite se forme toujours aux dépens de l'hydroxyapatite dans des conditions physiologiques. Cette transformation se continue en abaissant le pH.
    Abstract: Zusammenfassung Eine Mineralprobe aus Burgess, Kanada, erwies sich nach chemischer und kristallographischer Analyse als außergewöhnlich reines Fluorapatit. Die Gesamtzusammensetzung entspricht: $$(Ca^{2 + } )_{9,98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0,02} (PO_4^{3 - } )_{5,98} (HCO_3^ - ,CO_3^{2 - } )_{0,02} (F^ - )_2 $$ . Die kristallographische c-Achse wurde bestimmt und ergab 6,865 Å, und die a-Achse ergab 9,374 Å. Austauschwerte, welche durch Anwendung von45Ca,32P und18F erhalten wurden, deuteten auf große Kristalliten mit einer spezifischen Oberfläche von ca. 1 m2/g. Die Befunde deuten darauf hin, daß für die physikalische Erklärung des Austauschvorganges keine separaten Kompartimente mit eigenen kinetischen Faktoren nötig sind, sondern daß der Austausch mit dem exponentiellen Wechsel in der freien Energie der Reaktion in einfacher Beziehung steht. Für die Reaktion $$(Ca)_5 (PO_4 )_3 OH_{in fester Form} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{in fester Form} + (OH^ - )$$ wurde als thermodynamische Konstante 101,26 errechnet, was darauf deutet, daß unter physiologischen Bedingungen immer Fluorapatit auf Kosten von Hydroxyapatit entsteht. Diese Umwandlung wird erhöht, wenn das pH erniedrigt wird.
    Notes: Abstract A mineral specimen from Burgess, Canada, proved upon chemical and crystallographic analyses to be an exceptionally pure sample of fluorapatite. The over-all composition corresponds to $$(Ca^{2 + } )_{9.98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0.02} (PO_4^{3 - } )_{5.98} (HCO_3^ - ,CO_3^{2 - } )_{0.02} (F^ - )_2 $$ . The crystallographic c-axis was determined to be 6.865 Å, and the a-axis 9.374 A. Exchange data obtained by employing45Ca,32P, and18F indicate the presence of large crystallites with a specific surface of the order of 1 m2/g. It is indicated that the physical interpretation of the exchange process does not require the existence of separate departments, each with its own kinetic factor, but that the exchange may be simply related to the exponential change in the free energy of the reaction. For the reaction $$(Ca)_5 (PO_4 )_3 OH_{solid} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{solid} + (OH^ - )$$ the thermodynamic constant has been calculated to be 101.26, implying that fluorapatite always will form at the expense of hydroxyapatite under physiologic conditions. This transformation will be furthered by lowering the pH.
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  • 20
    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
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    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 21
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    Astrophysics and space science 224 (1995), S. 81-84 
    ISSN: 1572-946X
    Keywords: Chemistry ; Depletions ; Shocks ; IRAS 05338-0624 ; NGC 1333 IRAS 4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High resolution interferometer and single-dish observations of young, deeply embedded stellar systems reveal a complex chemistry in the circumstellar environments of low to intermediate mass stars. Depletions of gas-phase molecules, grain mantle evaporation, and shock interactions actively drive chemical processes in different regions around young stars. We present results for two systems, IRAS 05338-0624 and NGC 1333 IRAS 4, to illustrate the behavior found and to examine the physical processes at work.
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    Astrophysics and space science 216 (1994), S. 153-154 
    ISSN: 1572-946X
    Keywords: Chemistry ; Molecular Hydrogen ; Cloud Models
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    Topics: Physics
    Notes: Abstract Observations of the CO J=1-0 line are commonly used as a tracer for molecular material in clouds. The ratio of the H2 column density to the integrated intensity of this line,X, is often taken to be constant, despite theoretical and observational uncertainty. We have tried to identify how this ratio depends on cloud parameters, testing a simple theoretical argument suggesting its invariance with respect to density. The apparent constancy can be understood if clouds are clumpy on scales of Av ≈ 1-2 mag.
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    Boundary layer meteorology 85 (1997), S. 197-222 
    ISSN: 1573-1472
    Keywords: Turbulence ; Chemistry ; Closure ; Convective boundary layer
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    Topics: Geosciences , Physics
    Notes: Abstract We study the interactions of chemistry and turbulent mixing of tracersin the convective boundary layer with a second-order closure model,including higher order chemistry terms. In order to limit the number of predictive equations we prescribe the profiles for ¯w¯Θ, ¯w¯θ ¯θ and the lengthscale l. However, for model validation we treat temperature and humidity asinert tracers, and compare the results with profiles observed during theAir Mass Transformation Experiment, and with similarity expressions for thesurface layer. We find good agreement of the mean profiles, but the (co-)variances are slightly underpredicted. Furthermore, the model usesdiagnostic equations expressing third moments of concentration in terms ofsecond moments and their vertical derivatives. They are compared withlarge-eddy model results, showing good agreement and, therefore, thesimplifications are justified. The model is applied to the transport of two gases subject to one bimolecular reaction. The importance of concentration correlations on themean transformation rate is studied. For two gases diffusing in oppositedirections we find for moderate and fast chemistry a 50% and90% decreased transformation rate due to the negatively correlatedconcentrations. These values are similar to large-eddy results of Schumannand Sykes et al. For two bottom-up tracers we find that the covariance ofboth reactive species is either positive or negative, increasing or reducingthe effective transformation rate depending on the Damköhler number (the ratio of the turbulent and the chemistry timescale). A significantdirect influence of chemistry on the flux divergence is found in bothcases. According to the model the effective transport to mid-levels of theboundary layer is increased when two reactive tracers diffuse in oppositedirections, and decreased in the case of two bottom-up tracers.
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  • 24
    ISSN: 1432-0878
    Keywords: Milk ; Fat globule membrane ; Carbohydrates ; Chemistry ; Ruthenium red ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fat globules of the cream fractions of human and rat milk were stained with ruthenium red. Under the electron microscope, discrete granules and an amorphous coat of lesser density are seen at the surface of the milk fat globules. Since ruthenium red binds anionic groups selectively, it is probable that the granules containe the greatest concentration of these groups. The cream fraction of rat milk contains hexoses, hexosamines, methylpentoses and sialic acid. Methylpentoses and hexosamines are significantly enriched in the cream fraction. It is concluded that the finding of a surface coat in milk fat globules is in keeping with the Bargmann-Knoop model and suggests a distinct mechanism for carrying certain complex carbohydrates in milk. The role of the negative charges at the outer surface of the membrane coat in maintaining fat globules in suspension and in binding certain cations such as calcium is suggested.
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  • 25
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; Codeine phosphate drug substance ; Opium alkaloids
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    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid procedure for the evaluation of codeine phosphate drug substance derived from poppy straw or opium concentrate is described. The gradient HPLC procedure employs a pH 2.5 phosphate buffer, methanol and acetonitrile mobile phase at 40°C and a μBondapak C-18 column. Eight opium alkaloids, including the four major alkaloids, are separated from each other. The paper describes details of the assay procedure and presents data documenting the linearity, specificity, precision, and sensitivity of the method.
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  • 26
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; External variance determinations ; Column and system compatibility ; Microbore and fast LC
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    Topics: Chemistry and Pharmacology
    Notes: Summary The demand for faster, more economic and convenient high-efficiency LC analyses has led to the development of microbore and fast columns. However, to utilize their benefits, the low column dispersions produced by these new technologies necessitate low external variances in the total system. This paper describes the determination of the external variance of microbore, fast and conventional LC systems by a column method. Compatibility with the relevant column technologies is evaluated by a method involving the comparison of the external and column dispersions. Direct comparison of chromatograms of an 8-component mixture, on a set of columns of various diameters and lengths, shows the relative speed, economy and sensitivity obtainable in practice. The problem of reduced sample loadability is considered and the practical solution of peak compression illustrated.
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  • 27
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention prediction system ; UV multichannel detector ; Polycyclic aromatic hydrocarbons
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention prediction system assisted by a micro-computer coupled with an UV multichannel detector has been investigated in the separation of polycyclic aromatic hydrocarbons. The method offered very precise identification of components in NBS-SRM-1647 sample without any standard reference substances. It has been proven that the system makes very precise, non-pollutive and convenient environmental analysis possible.
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    Chromatographia 20 (1985), S. 313-322 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tetracyclines antibiotics ; Quantitation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The use of high-performance liquid chromatography (HPLC) for the identification and determination of tetracycline antibiotics is reviewed. HPLC chromatograms provide fast identification by retention time, tR, and precise quantitation by measurement of peak height or peak area. For separation of tetracycline compounds, most HPLC methods use reversed-phase C18 or C8 columns and UV detection. The HPLC solvent system should have a pH of about 6 to prevent steric changes in the tetracycline molecule. For accurate quantitation it is necessary to avoid tailing and this is accomplished by adding a zwitter ion to the solvent system. Methanol and acetonitrile are frequently used as organic modifiers in these solvent systems. In a single analysis, HPLC methods can be used to separate as many as nine or ten commercially used tetracycline compounds and to determine four to five tetracyclines in commercial tetracycline preparations or in biological fluids.
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  • 29
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Resolution of optical isomers ; Chiral column ; Pyrethroids ; Fenvalerate
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    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of the optical isomers of fenvalerate [cyano(3-phenoxyphenyl)methyl 2-(4-chlorophenyl)-3-methylbutyrate] has been carried out by high-performance liquid chromatography (HPLC) on a chiral column with (R)-N-3,5-dinitrobenzoyl-phenyl-glycine (DNBPG) covalently bonded on aminopropyl silica and eluted with mixtures of methanol, 2-propanol, and hexane. The system was applied to the analysis of Pydrin®, an emulsifiable concentrate formulation of fenvalerate, and to the residue analysis of fenvalerate in milk samples. For the analysis of Pydrin® the only requirement was the proper dilution of Pydrin® with hexane. For the analysis of residues in milk, fenvalerate was extracted with hexane after precipitating the milk proteins with acetonitrile and removing the precipitate by filtration; the hexane extract was concentrated to small volume and filtered before being analyzed by HPLC.
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    Chromatographia 20 (1985), S. 487-494 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size-exclusion chromatography ; Controlled-porosity glasses ; Boron-enriched glass surface ; Adsorptive properties
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    Topics: Chemistry and Pharmacology
    Notes: Summary Controlled-porosity glasses (CPG) are sieves for macromoleculars, very widely applied in chromatographic columns for the separation of polymers and biopolymers by means of size-exclusion chromatography (SEC) and affinity chromatography. This paper deals with the influence of the thermal treatment of CPG on the elution of polymers in SEC columns. The problem is examined for a few mobile phases and for glasses having different porosities. Additionally, the SEC results obtained are compared with the adsorption properties of the glases investigated.
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  • 31
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Cysteinyldopamine ; Tyrosinase ; Autoxidation
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    Topics: Chemistry and Pharmacology
    Notes: Summary 5-S-Cysteinyldopamine, a new metabolite of dopamine, was determined in urine by high-performance liquid chromatography with electrochemical detection. The catechol was detected in 14 of 21 melanoma patients and 7 of 21 normal subjects; the highest values were 657 μg/day for melanoma patients and 44 μg/day for normal subjects. These results suggest that the cysteine conjugate may arise from autoxidation of dopamine but tyrosinase may also participate in the oxidation.
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  • 32
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    Chromatographia 21 (1986), S. 136-142 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemical reaction detector ; Carbamate insecticides ; Quantitation
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    Topics: Chemistry and Pharmacology
    Notes: Summary For the determination of trace amounts of carbamate insecticides in vegetables the combination of liquid chromatography with post column chemical derivatization (chemical reaction detector) is used. In a two step reaction detector the carbamates are firstly saponified in 0.01 M sodium hydroxide at 80°C with a reaction time of 30sec. To this mixture OPA reagent is added to detect the methylamine generated in the saponification. Optimization strategies for this reaction are demonstrated. At a temperature of 80 °C a reaction time of 80 sec is sufficient for quantitative transformation of the methylamine. The peak dispersion can be reduced and hence the detection limit improved by decreasing the diameter of the tubes and by diminishing dilution through the addition of reagent. A 1∶24 ratio of reagent to column (reactor) effluent is possible with cyclone-type mixers. The quantitation of carbamates in different vegetables is demonstrated. The detection limit is 20ppb at a signal to noise ratio of 10∶1.
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  • 33
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    Chromatographia 21 (1986), S. 205-213 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral phases ; Optimization of separation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation and properties of chiral bonded phases with amino acid groups are described. These phases were used in non-polar eluents and in aqueous systems in the presence of Cu2+ ions in the ligand-exchange mode. The optimization of chiral resolution is demonstrated for both cases. With non-polar eluents similarity between bonded groups and solutes is required. The elution could be accelerated by non-protonic moderators. Ligand-exchange separation is influenced by the copper content of the eluent and the stationary phase, the organic moderator concentration, the pH and ionic strength of the buffer and by the temperature. Structural requirements of both the bonded groups and of the solutes for chiral separation are discussed.
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  • 34
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase capacity factors ; Cavity term ; Molar volumes
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    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase liquid chromatographic capacity factors are well correlated by an equation of the form: $$logk' = (logk')_0 + mV/100 + s\pi ^* + b\beta + a\alpha $$ wheremV/100 measures the cavity term and π*, β, and α are the solvatochromic parameters that measure solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity respectively. Liquid molar volume (molecular weight divided by liquid density at 20°C) $$\bar V$$ , and computer-calculated intrinsic (van der Waals) molecular volume, $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ , are compared as measures of the cavity term in a number of correlations. $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ leads to more precise correlations as well as to a “cleaner” dissection of the multiple solute/solvent interactions. The opposing exoergic effect of solvent donor/solute acceptor hydrogen bonding, and endoergic cavity term are the main factors influencing HPLC capacity factors.
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  • 35
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    Chromatographia 22 (1986), S. 40-42 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pyridate ; CL-9673 ; Reversed phase
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    Topics: Chemistry and Pharmacology
    Notes: Summary The application of a simple reversed-phase, HPLC-UV method for the determination of the contact herbicide pyridate and its main metabolite 3-phenyl-4-hydroxy-6-chloropyridazine-known as CL-9673-in green cereals, grains and straw is described. The method is based on a simple extraction, separation of pyridate from its metabolite, hydrolysis of pyridate to CL-9673, high-performance liquid chromatographic separation of CL-9673 in both fractions using only one reversed phase column and UV-detection. The method is sensitive down to 3 ngg−1 CL-9673 in green plants and grain and 5ngg−1 in straw. In the range 0.05–1.0mgkg−1 recoveries are between 73.7% and 109% from green plants, between 77.7% and 102% from grains and between 77.3% and 87.5% from straw.
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  • 36
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Betablocker drugs ; Lipophilicity ; Capacity factors ; Distribution coefficients
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    Topics: Chemistry and Pharmacology
    Notes: Summary The reverse-phase, high-pressure liquid chromatographic capacity factors (k') of a series of 18 betablocking agents were determined in order to establish correlations with their distribution coefficient values (D), obtained from four bibliographic sources. Under the three pH conditions studied (3.5, 6.2 and 7.5) statistically significant linear correlations (p〈 0.002) between log k' and log D values were obtained for the four series studied. In this series it is concluded that the k' factor is a useful and reliable relative lipophilicity parameter.
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  • 37
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    Chromatographia 22 (1986), S. 81-87 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Recycle chromatography ; Pressure dependence ; Capacity factor
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    Topics: Chemistry and Pharmacology
    Notes: Summary It was found experimentally that the potential for routine, rapid high-efficiency separations by alternate column, recycle, reversed-phase chromatography is limited by the increase of capacity factors with pressure.
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  • 38
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aromatic acid isomers ; Low capacity ion-exchange resin ; Microbore packed columns
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    Topics: Chemistry and Pharmacology
    Notes: Summary A low-capacity, anion-exchange, porous-polymer resin was used as the packing material in a microbore column. Using a phosphate buffer containing various organic modifiers, retention behavior of substituted benzoic acid isomers with amino, chloro, methyl, nitro and carboxylic groups was investigated. The effect of ethanol, acetonitrile and sodium dodecylsulfate used as organic modifiers on the retention behavior at various eluent pH values was studies and optimum separations of the positional isomers reported.
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  • 39
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    Chromatographia 18 (1984), S. 668-672 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed eluents ; Preferential sorption of eluents ; Pressure effects
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    Topics: Chemistry and Pharmacology
    Notes: Summary Pronounced base line perturbations were repeatably observed in LC both in alternating recycling and in backflushing experiments when binary eluents and refractometric detectors were used. The perturbations which we call eigenzones appeared immediately after operating the recycling or the backflushing valve, and their size and shape depended on the nature of both the column filling and the mixed mobile phase as well as on the pressure drop across the column. Experimental results presented confirm that the primary causes of the eigenzones were the pressure changes in the columns which influenced the sorption equilibrium of mixed eluent components within the column packing. Some practical consequences of this effect are briefly discussed.
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  • 40
    ISSN: 1612-1112
    Keywords: Polycyclic aromatic hydrocarbons ; Column liquid chromatography ; Polyphenyl bonded phases ; Retention and carbon content
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    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the retention of PAHs having various molecular sizes and the carbon contents (%) of bonded stationary phases with various types of ligands were investigated. The examined stationary phases were phenyl, diphenyl, triphenyl and benzyl-bonded silicas. The data indicated that sometimes it is not true that the retention of any solute relates linearly to the carbon content of the stationary phase. As the result, it is suggested that the pore size distribution of the silica support, the bulkiness of the ligand bonded to the silica and the molecular size of solute should also be considered before any precise statement can be made.
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  • 41
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Metalloporphyrins ; 5,10,15,20-Tetraphenylporphine
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    Topics: Chemistry and Pharmacology
    Notes: Summary The Co(II), Ni(II), Fe(III) and V(IV) complexes of tetraphenylporphine (TPP) can be eluted at short retention times from a LiChrosorb RP-18 column with pure ethanol. However, both Mn(III) and Co(III) complexes of metal TPP chloride type are so strongly retained on the column that they cannot be eluted. While the retention of other metal teraphenylporphine complexes was not affected, that of the metal(III) complexes of the TPP chloride type especially MnTPPCl and CoTPPCl, decreases dramatically with an increase in the concentration of NH4Cl added into the mobile phase; a linear relationship between logk' and log[NH4Cl], with the slope of about−1, has been observed for these two metal(III) complexes in the NH4Cl concentration range from 2.5×10−4 to 1.3×10−2 mol/l. Thus, the specific control of the retention of the metal(III) complexes is enabled by conditioning the NH4Cl content of the mobile phase, and the chromatographic separation is demonstrated.
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  • 42
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    Chromatographia 22 (1986), S. 55-58 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1-Octanol/water partition coefficient ; Cellulose acetate ; Reverse osmosis
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    Topics: Chemistry and Pharmacology
    Notes: Summary The adsorption properties of esters, aldehydes, ethers and amides on cellulose acetate, which is commonly used as a reverse osmosis membrane material, in an aqueous solution system were measured by high-performance liquid chromatography. The adsorption property was characterized with the specific retention volume. For a noncyclic homologous series the logarithm of the specific retention volume was linearly correlated with the logarithm of the partition coefficient between 1-octanol and water. The fact that the slopes of these regression lines are almost identical confirms that the dominant effect on adsorption is the hydrophobic interaction between cellulose acetate and the solute molecule. The intercept represents the effect of the polar groups on adsorption. The effect of the polar group decreases as follows: ―C(O)O―, ―CO―, HCON〈 〉 CH3CON〈 〉 ―OH, ―O―.
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  • 43
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dihydroartemisine ; Interconversion equilibrium ; Multiple-peaks
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    Topics: Chemistry and Pharmacology
    Notes: Summary The interconversion between the α- and β-isomers and the multiple-peaks of dihydroartemisinine (dihydroqinghaosu) were investigated in reversed-phase, highperformance liquid chromatography. A convenient method using the Gaussian distribution function instead of the Schmidt graphical method for the theoretical calculation of the “diffuse” probability curves versus the fraction of the dead time on column as β form was introduced. Based on the theoretical probability curves and the experimental multiple-peak chomatograms, the effects of temperature and flow velocity on the accuracy and precision of analysis of dihydroartemisinine are indicated and the activation energy of the interconversion between α- and β-isomers of dihydroartemisinine is estimated.
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  • 44
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nucleotides ; Mytilus edulis ; Smooth muscle
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the analysis of the 5′ mono-, di- and triphosphates of adenosine, guanosine, uridine and cytidine, as well as uridinediphosphate-glucose and cyclic AMP. Separation is achieved by reversed-phase ion-pair chromatography with linear gradient elution. Application of this method to the analysis of nucleotides in smooth molluscan muscles is described, including the determination of cAMP-levels and the calculation of energy charges for all of the four nucleotide systems.
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  • 45
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porphyrin ; Metalloporphyrin ; Hematoporphyrin IX
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    Topics: Chemistry and Pharmacology
    Notes: Summary The feasibility of reversed-phase high-performance liquid chromatography for the separation of metal complexes of hematoporphyrin IX (Hp) is described. The retention order, Zn-complex〈Hp (free acid)〈 Ni-complex〈Cu-complex, is regular on an octadecylbonded stationary phase with different compositions of an aqueous methanol mobile phase. These four compounds can be successfully separated within about 8 min on a LiChrosorb RP-18 column (250×4-mm i.d.) with a 85:15 (vol/vol) mixture of methanol and phosphate buffer (pH 3) at a flow rate of 1 ml/min.
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  • 46
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    Chromatographia 22 (1986), S. 157-159 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonol aglycones ; Isocratic elution ; Wine phenolics
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    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC isocratic elution procedure which allows the separation of flavonol aglycones in wine without interference from other phenolics of low molecular weight is described. The method has been applied to the separation, identification and quantitative estimation of flavonol aglycones in ether extracts of different Spanish wines (red and white table wines and Sherry finos). The results suggest that these determinations, associated with other analyses, would permit the chemical characterization of wines.
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  • 47
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    Chromatographia 23 (1987), S. 796-802 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Steroids ; Rat tissue ; Purification by extraction
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    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method for analysis of steroids in the tissue of laboratory animals is described. A two-stage solid extraction procedure, utilizing Sep-pak C18 and graphitized carbon black, gives a purified product. Steroids in this extract were separated by multistep gradient elution with a reversedphase liquid chromatography system, using acetonitrilewater as solvent. Several columns with different geometry and phase loading were investigated. Optimum resolution was obtained with a medium covered and spherical particle. The applicability of this method was successfully demonstrated in the analysis of the testis and adrenal gland of rat.
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  • 48
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    Chromatographia 23 (1987), S. 814-817 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Ammonium tungstophosphate ; Aminoacids
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    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of aminoacids on columns of silica coated with different percentages of ammonium tungstophosphate at several buffer phosphate concentrations is reported. The stationary phase shows a high selectivity towards aminobutyric acids and methyl derivatives of tryptophan due to the distance between the carboxylic group and the −NH 3 + group involved in the cation-exchange process and/or to the steric hindrance by a methyl substituent. A relationship between HPLC and HPTLC data has been verified and applied to the prediction of the separation of six aminoacids.
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  • 49
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    Chromatographia 23 (1987), S. 934-938 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calibration ; Confidence interval ; Limit of determination ; Limit of calibration
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    Topics: Chemistry and Pharmacology
    Notes: Summary In HPLC calibration the expressions lowest calibration limit and determination limit are defined in statistical terms. The lowest calibration limit is the minimum mass in the measured series of calibration points. It is calculated from the confidence interval of the inverse of the calibration function as the lowest mass limit that may be differentiated from zero mass with a preset probability of error. If the calculated lowest calibration limit is lower than the actual data, points at lower concentration may be measured. The determination limit is the smallest concentration of an analysis that is differentiated from the concentration zero or an apparent blind value in the calibration curve with a given probability of error. Using two different UV-detectors (variable wavelength and photodiode-array) the lowest calibration limit is experimentally evaluated and compared with specific data for the detectors.
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  • 50
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    Chromatographia 18 (1984), S. 175-182 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fourier transform IR ; Polar compounds ; Coal products
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    Topics: Chemistry and Pharmacology
    Notes: Summary Fourier-transform infrared spectrometry (FTIR) was utilized as a detection system for high-performance liquid chromatography of polar compounds on a normal bonded-phase system. In addition to FTIR, UV (254 nm) and refractive index detection were employed in the separation of model compounds containing oxygen and nitrogen atoms in their molecules (phenols, alcohols, neutral and weakly basic nitrogen compounds). A polar amino-cyano (PAC) bonded-phase column was employed with a binary mobile phase (98:2 CDCl3:CH3CN). The separations and the information gained from each detector is discussed, including interactions between sample material and mobile phase. A polar fraction of a coal-derived product is also chromatographed under identical conditions. The results based on FTIR detection and chromatographic retention behavior suggest the exclusive presence of hindered and unhindered phenols.
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  • 51
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    Chromatographia 18 (1984), S. 211-215 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkylbenzenes ; PAHs ; Retention prediction ; Microcomputer
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    Topics: Chemistry and Pharmacology
    Notes: Summary The microcomputer-assisted retention prediction system in C18 reversed-phase HPLC is described. The system is based on the use of the hydrophobic parameter and the correlation factor of alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) which are highly correlated to their retention in reversed-phase HPLC. The system is evaluated by comparing the retention data between measured and predicted values. One of the typical examples applied for PAH analysis in the extracts of diesel particulate matter shows the high potential of the system investigated.
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  • 52
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    Chromatographia 18 (1984), S. 216-220 
    ISSN: 1612-1112
    Keywords: Cation exchangers ; Column liquid chromatography ; Exchange capacity, determination ; Organic peroxidation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Two oxidation procedures for the synthesis of silicabased aliphatic sulfonic acid cation-exchangers for HPLC are described. Several reaction conditions for oxidizing a terminal-bonded thiol with organic peroxides are provided along with their yields, capacities, reproducibility, and chromatographic behavior. Also, three methods for determining exchange capacity are discussed, and their relationship to the capacity factors of charged solutes is compared. The maximum capacity determined by the titration of the bonded silica was 0.34 meq/gram. The general problems of synthesizing cation-exchangers, measuring their efficiencies and exchange capacities, and evaluating their overall performances are outlined.
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  • 53
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-column derivatization ; Ultraviolet detector sensitivity ; Dihydroartemisinin ; Diacetyldihydrofluorescein
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    Topics: Chemistry and Pharmacology
    Notes: Summary The use of diacetyldihydrofluorescein (DADF) for derivatization of dihydroartemisinin (dihydroqinghaosu, DHQHS) is proposed. The reaction between DHQHS and this reagent in the presence of 4-dimethylaminopyridine (DMAP) and N,N′-dicyclohexylcarbodiimide (DCC) was complete in 8 hours at room temperature giving about 80 per cent theoretical yield. The derivative showed intense UV absorption, thus providing a sensitivity of 0.1 nanogram by UV detection after column separation. The influences of the ratio of the reagents, reaction temperature, chromatographic conditions and the extent of detection linearity were investigated. The reaction gave consistent results and chromatographic separation was not affected by an excess of the reagent or side products.
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  • 54
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    Chromatographia 18 (1984), S. 369-373 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange ; dynamic ; Metal ions ; Equilibria effects
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    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibria occurring during the dynamic ion exchange separation of metal ions were examined, and their effect on the chromatography of the metal ions was evaluated. Bonded reversed-phase silica, pure organic reversed phase, and silica columns were used to differentiate between the role of silica and the reverse phase. The results show that system peaks had the most important influence on the applicability of dynamic exchangers to quantitative metal ion determinations. The response of system peaks to sample composition (pH, ionic strength, matrix effects) was complicated and could not be predicted easily. Equilibria effects that can cause analytical errors were identified and recommendations for elimination of such errors are given.
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  • 55
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amines ; Phenols ; Fourier transform I.R.
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    Topics: Chemistry and Pharmacology
    Notes: Summary Several chromatographic parameters have been examined as to their effect on detectability for microbore high-performance liquid chromatography coupled with Fourier-transform infrared spectrometry. Detection limits for several compound classes are presented as amount injected. Improvements in detectability for this technique are discussed.
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  • 56
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polystyrene packings ; Pre-column derivatization ; Thiamine compounds ; UV and fluorescence detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatography of thiochrome and related phosphate esters was studied on two different polystyrene packing materials. The adsorbents were compared with respect to capacity factors, plate heights and resolution factors measured with different mixtures of phosphate buffer (pH 8.5) and methanol. In contrast with derivatized silica, these phases were found to be stable using an alkaline mobile phase and sample. Fast separations were possible with good peak symmetry at all organic modifier concentrations.
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  • 57
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    Chromatographia 18 (1984), S. 445-448 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino-bonded stationary phase ; Ion-exchange ; Fermentation solution ; Biomass
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    Topics: Chemistry and Pharmacology
    Notes: Summary In this work the analytical separation of biomass hydrolysis and fermentation products is described. Aminobonded phase and ion exchange materials (HPX 87H, HPX 42A, μ Spherogel Carbohydrate) were used as HPLC stationary phases for the determination of monomeric and oligomeric carbohydrates, carbohydrate degradation and fermentation products. The HPX 42A and the amino-bonded phase columns are especially suitable for the analysis of the gluco oligomers. The HPX 87H column separates the monomeric sugars and their degradation and fermentation products (e.g. furfurals and ethanol) very well. Using the μ Spherogel Carbohydrate column the lower gluco-oligomers as well as the monomeric sugars and their degradation and fermentation products, can be determined within 35 minutes.
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  • 58
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral bonded phase ; Racemate resolution
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    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral stationary phase with an immobilized, optically active diamine was prepared for the separation of enantiomers. The synthesis of the phase was carried out by bonding (−)trans-1,2-cyclohexanediamine to microparticulate silica gel through the coupling agent 3-glycidoxypropylsilane. The resolution of the racemic compounds catechin, 2,2′-dihydroxy-1,1′binaphthyl and trans-1,2-cyclohexandiol, is reported.
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  • 59
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    Chromatographia 18 (1984), S. 495-498 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; PAHs ; Molecular shape recognition
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    Topics: Chemistry and Pharmacology
    Notes: Summary The molecular-shape recognition of polycyclic aromatic hydrocarbons has been studied on various stationary phases in reversed-phase high-performance liquid chromatography. The examined stationary phases were phenyl-, diphenyl-, triphenyl- and benzyl-bonded silicas. The results of regression analysis inidcated that triphenylsilica is the best packing material to recognize the difference in the molecular-shape of structural isomers. This fact was confirmed by the separation of 4-ring isomers.
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  • 60
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention data ; Substituted benzene derivatives ; Correlations
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    Topics: Chemistry and Pharmacology
    Notes: Summary The capacity factors of substituted benzene derivatives on bonded phases of various chain lengths in the reversed-phase mode have been measured and correlation of retention data between four stationary phases has been investigated by linear regression analysis. As a result, a difference in the retention mechanism between phases of shorter chain length and octadecylsilica was observed. In addition, it is also apparent that the multicombination treatment between retention data and descriptors such as π, HA, HD and σ promises the possibility of predicting the retention of substituted benzene derivatives on various reversed-phase stationary phases.
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  • 61
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyamines ; Dansyl derivatives ; Peak compression
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    Topics: Chemistry and Pharmacology
    Notes: Summary Analytical conditions for the high-speed, reversed-phase, liquid chromatographic of a diamine (putrescine) and polyamines (spermine and spermidine) were determined. Various elution modes were employed using the same mobile phase constituents: 20mM sodium heptane sulfonate and 20mM acetic acid as solvent A and, pure acetonitrile as solvent B. Samples were derivatized with dansyl chloride before injection. Under isocratic conditions, the separation of the three polyamines was achieved in 7 min. The use of a linear elution gradient led to the same analytical time but with a better resolution of the putrescine peak from non-polyamine frontal peaks. For these measurements, the sample size was 5μl. This volume was increased to 20μl and the use of a steep gradient combined with the peak-compression technique allowed a fast analysis in 2–3 minutes, which may be compared with a 30 min run time necessary when a conventional column is used.
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  • 62
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    Chromatographia 23 (1987), S. 395-400 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photokinetic data ; Reaction mechanism ; (E)-1-phenylpropene
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    Topics: Chemistry and Pharmacology
    Notes: Summary A combined method of high-performance liquid chromatography and UV-absorption spectroscopy is described for use in dynamic systems. It provides a way of obtaining detailed mechanistic information as well as quantitative data (rate constants, quantum yields), even though neither mechanism nor photoproducts are known. The kinetic treatment of the photoreaction of (E)-1-phenylpropene was successful, showing a photo-isomerization and a parallel step. Information on this additional step is obtained by using HPLC to observe the changes in the concentrations of the reactants' selectivity. The necessity of process control is demonstrated.
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    Chromatographia 23 (1987), S. 419-422 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acid esters ; Particulate material in seawater
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the determination of fatty acids of the molecular weight range of propionic to erucic acid is reported. The acids are converted to either p-bromophenacyl-or p-phenylphenacylesters and the esters are separated by HPLC and detected by UV-absorption. Twentytwo esters, including saturated, monoolefinic and polyunsaturated ones were separated within one HPLC-run. The detection limit is about 5 pmol per fatty acid. The application of the method to particulate material is described.
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  • 64
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange stationary phases ; Polymer coating ; Cross-linking
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    Topics: Chemistry and Pharmacology
    Notes: Summary PHEB=POLY(2-hydroxy, 3N-ethylenediamino)butadiene has been synthesized. This unsaturated pre-polymer can be immobilized on different, preferably inorganic supports of suitable porosity such as silica or alumina by cross-linking. Weak anion-exchange phase are obtained. Such phases do not have the disadvantages of organic polymeric phases, regarding pressure stability and swelling by solvent influence. The ion-exchange capacity and the retentivity of IE-separations can deliberately be varied via the thickness of the cross-linked polymer layer. Alumina can also be coated with PHEB applying the same cross-linking procedure. Such phases exhibit an exceptional chemical stability even when operated with mobile phases at very high pH-values. Separations of excellent selectivity are achieved for inorganic anions, as well as with mixtures of aliphatic and aromatic free acids also including hydroxy- (mono- or poly)carboxylic acids.
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  • 65
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase systems ; Stationary phase-solute interactions ; Polycyclic aromatics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capacity factors of peropyrene-type polycyclic aromatic hydrocarbons were measured using 15 different liquid chromatographic reversed phase systems. On the basis of the retention data the electric interaction indices have been calculated. Application of these indices for structure-retention studies on peropyrene-type polycyclic aromatic hydrocarbons is demonstrated.
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  • 66
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    Chromatographia 25 (1988), S. 31-36 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Radioactivity detector ; Solid scintillator ; Fibre-packed flow cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new type of flow-cell radiation detector for use in liquid chromatography which is packed with aligned scintillator fibers is described. A primary advantage of the fiber packed cell is that light generated by the scintillator is absorbed to a much less extent by the fibers than by the powder scintillator used in conventional flow cells. A detection efficiency of 55% has been obtained for carbon-14 using 0.1-mm diameter hand-pulled glass fibers. Computer modeling has shown that even better results can be obtained by using smaller and more uniform diameter fibers which will allow better packing. The fiber cell also demonstrates back pressures which are a factor of 50 less than the conventional cell and much less susceptibility to absorption of compounds because of its lower surface area.
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  • 67
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    Chromatographia 25 (1988), S. 854-860 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polystyrene ; Gradient elution ; Turbidimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polystyrene samples of narrow molecular-weight distribution have been eluted according to their molecular weight from columns packed with bare silica Si50, phenyl, or C18 bonded phase by gradients of methanol and tetrahydrofuran (THF) or ofiso-octane and THF. Among the six combinations investigated,iso-octane/THF with a silica column formed a proper normal-phase system whereas methanol/THF with a C18 column formed a proper reversed-phase system. The combinations of C18 column andiso-octane/THF or of Si50 column and methanol/THF gradient did not correspond to the approved polarity rules in high-performance liquid chromatography but were nevertheless effective in separating polystyrene mixtures by molecular weight. Methanol andiso-octane are nonsolvents for polystyrene whereas THF is a solvent. The solubility of polystyrene as a function of molecular weight and concentration was determined by means of turbidimetric titration of solutions in THF with the nonsolvents used in the gradients. The solubility and elution characteristics were almost identical on C18 columns or in methanol/THF combinations. The elution from phenyl bonded phase and Si50 columns usingiso-octane/THF gradients required more THF than the solubility experiments. Information is also given on the occurrence of multimodal elution patterns.
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  • 68
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polycyclic aromatic compounds ; Alkylated PAC ; Retention characteristics ; Normal phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention characteristics of series of polymethyl and mono-n-alkyl derivatives of benzene and pyrene, and also of parent polycyclic aromatic hydrocarbons (PAH), were studied using silica and aminopropyl- and cyanopropyl-modified silica. Differences in the selectivities for the studied compound groups were found between the three phases. Deviations from linear behaviour in plots of log (k′)vs. carbon number were observed for the methyl series. These are explained in terms of differences in π-electron delocalisation within the aromatic ring systems. Further, the effect of methyl substitution on selectivity decreased with an increasing number of aromatic rings. Results were obtained which indicated that the primary adsorption site in a cyano column used in normal phase mode, at least for PAH molecules, is the cyano group.
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  • 69
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    Chromatographia 25 (1988), S. 43-50 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phase ; Void volume ; Adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In reversed-phase liquid chromatography with n-alkyl bonded silica, the dead volume (V0) of the column is theoretically indeterminate owing to adsorption of organic modifier on n-alkyl chains and of water on silanol groups. With binary mobile phases, retention volumes of the mobile phase components and of their deuterated species are relaeed to the adsorption isotherms and V0 by equations which can be solved with some assumptions on the adsorbed layer composition. Methanol-water and acetonitrile-water systems are studied. As the experimental excess isotherm shows a linear part in the concentration range 50–80% in organic modifier, the hypothesis of an adsorbed layer of constant composition in this range is possible. When increasing the water content of the mobile phase, adsorption of water occurs up to saturation of silanol groups. Then the assumption of a constant water content for a mobile phase having more than 50% of water is applied. With the hypothesis of a constant adsorbed content of organic modifier when the eluent has more than 80% of organic modifier, V0 and the absolute isotherms are calculated over the entire range of mobile phase composition. Experimental retention behavior of the mobile phase components are totally explained by these V0 determinations. The retention times of commonly used V0 markers are compared with V0 values. It is shown that, when buffering the eluent, no visible effect on the distribution equilibrium is observed, so that injection of concentrated potassium nitrate is a convenient method to measure V0. With a few solutes with are UV detectable it is possible to measure V0 whatever the mobile phase composition in methanol-water and acetonitrile-water systems.
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  • 70
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phase solubility parameters ; Cyano-silica ; Amino-silica ; Diol-silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Extended solubility parameters have been determined for aminopropyl, cyanopropyl and 1,2-dihydroxypropyl propyl ether (diol) normal bonded-phase HPLC columns. Parameters were calculated from both the retention data of solutes (partition model) and empirically determined solvent strengths (adsorption-displacement model). The use of solvent strengths to calculate solubility parameters for these silica-based bonded stationary phases appears to be superior, since this technique avoids many of the problems that arise from their inherent heterogeneity. Normalized solubility parameters were also used to position these columns on a stationary phase selectivity triangle. The amino and cyano phases appear in regions of the tringle expected based on the properties of the pure liquids, but an ether linkage in the diol apparently neutralizes some of the acidity expected from this phase.
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  • 71
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Macrolide antibiotic azithromycin ; Intermediates of azithromycin ; Optimization of separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC is the most convenient method for the assay of the azithromycin (10-dihydro-10-deoxo-11-methyl-11-azaerythromycin A), a semisynthetic macrolide antibiotic and its reaction intermediates. Data concerning the effects of pH, temperature and column type are presented. The analytical procedures enabling the reliable assay of azithromycin and its intermediates, as well as other impurities are defined. Use of a reversed-phase octadecyl column, a pH of 9.3–9.5, and isocratic mode at ambient temperature are the best conditions of analysis.
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  • 72
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Metabolic disorders ; Xanthine and 2,8-dihydroxyadenine ; Urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 2,8-Dihydroxyadeninuria and xanthinuria are inborn enzyme disorders which must be under lifelong therapeutic control. Quantitative determination of 2,8-DHA and xanthine using reversed phase HPLC was performed. A new application for the separation of purines shortens analysis-time. Examples of the determination of 2,8-DHA and xanthine before and under certain therapies are shown. Long term monitoring of the patients offers the possibility of a reliable prophylaxis against stone recurrence.
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  • 73
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Indirect detection of non-electrolytes ; Simulation of induced peaks ; RP systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Induced peaks observed in indirect detection of nonelectrolytes in high-performance liquid chromatography are simulated. The equation representing the signal intensity of the induced peaks is derived, and it is verified by the experimental results. The peak area is proportional to (K b ′ +1) k a ′ /| a ′ —k b ′ |, where k a ′ ad k b ′ are the capacity factors of the visualization agent and the analyte, respectively.
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  • 74
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    Chromatographia 25 (1988), S. 162-166 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Analysis of metal ions ; Post column derivatisation ; Amperometric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for determination of metal ions subsequent to separation by ion chromatography has previously been developed. The method is based on Indirect Amperometric Detection whereby the decrease in the oxidation current, due to a dithiocarbamate ligand added post column, is monitored. Upon elution from the chromatographic column the metal ions are complexed by the ligand. As the complexes formed are electroinactive at the applied potential, the background current decreases according to the metal ion concentration. The method developed in this work involves addition to the reagent of Zn(II) as a auxiliary metal ion to displace the analyte metals from the chromatographic eluent ligand complexes after separation. Sodium bis(2-hydroxy-ethyl) dithiocarbamate was used as the postcolumn derivatising reagent. The addition of Zn(II) to the reagent causes some unforeseen behaviour in the chromatographic system.
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  • 75
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    Chromatographia 25 (1988), S. 199-204 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Catecholamines ; Urine ; Serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We developed an automated, two-column HPLC-method that can be used routinely to quantify the catecholamines norepinephrine and epinephrine in body fluids. The method is based on a new, laboratory-prepared SEC-HPAC column material, on the application of a microprocessor-controlled column-switching technique, and on the use of an integrated reaction system for postcolumn derivatization and trihydroxyindol-fluorescence monitoring. It allows the direct injection (upto 500 μl) of an appropriate biological fluid and distinguishes on its integrated sample-processing mode, its practicability, its chemoselectivity and-specivity, its detection limit (2 pg), its within- and between-run precision and its speed of analysis.
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  • 76
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pheophytinatonicke(II) ; Chlorophyll ; Pheophytin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC determination of pheophytinatonicke(II) (Pheo-Ni) prepared by the replacement of magnesium(II) in chlorophyll with nicke(II) is described. The good separation of PheoNi was obtained by using chemically bonded C18 as the stationary phase and acetone-methanol (50∶50, vol/vol) as the mobile phase. Conventional spectrophotometric method was also used for the determination of PheoNi. For the synthetic samples prepared by mixing (pheophytinato a) nicke(II) [(Pheo-a) Ni] and (pheophytinato b) nicke(II) [(Pheo-b) Ni], analytical values obtained by the spectrophotometric method were very high compared to those obtained by HPLC. In the proposed HPLC method, (Pheo-a) Ni and (Pheo-b). Ni could be determined in the concentration range of 0.028–30μg/ml and 0.038–30μg/ml with relative standard deviations (n=10) of 3.1% and 0.8%, respectively.
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  • 77
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonoid compounds ; Structure-retention relationships ; Reversed-phase systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase HPLC retention behaviour of different flavonoid compounds in different columns and with a range of methanol-buffer eluents was examined. Repeatibility and reproducibility of logk′ and Δlogk′ values were analyzed. Sharp group contributions, expressed as Δlogk′, were observed. These did not depend significantly on acid modifier type, column packing characteristics (C8 and C18) and dimensions (5,7 and 10μm) or the percentage of methanol in the mobile phase. A list of twelve group contributions is presented which is in agreement with literature data.
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  • 78
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    Chromatographia 25 (1988), S. 443-446 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Large scale separations ; Dissolution of silica ; Metallic contaminants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Possible contamination of purified product by the silica matrix is of considerable importance when considering process scale high-performance liquid chromatography (HPLC) as a separation methodology. The stability of silica supports in normal phase, reversed phase and affinity chromatography modes has been examined with organic solvents and water. Both inorganic and organic components were found, contributed by the support, and the chromatographic and distillation equipment. In all cases, based on assumed values of production, they were found to contribute less than 0.01% of impurities. In critical cases crystallisation or dialysis may be considered as a last stage of purification, with re-chromatography to maximise yields.
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  • 79
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fast atom bombardment mass spectrometry ; Nonionic detergents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Microcolumn liquid chromatography (LC) combined with fast-atom-bombardment mass spectrometry (FABMS) was applied to the analysis of nonionic detergents. The porous silver filter attached to the top of the capillary fused-silica tubing worked as the interface for coupling of micro LC and FABMS.
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  • 80
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    Chromatographia 25 (1988), S. 577-581 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Process scale ; Examples of separations
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    Topics: Chemistry and Pharmacology
    Notes: Summary The flexibility of process scale high performance liquid chromatography is demonstrated by three examples of reversed-phase separations (a) a standard purification (b) isolation of trace compounds, and (c) recovery from crystallisation mother liquors. It was shown that a material, thought to be acceptably pure, contained a toxic impurity, and a remaining impurity, a previously unseen component of potential therapeutic interest. Favourable cost data were indicated for example (3).
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  • 81
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzidine+diaminodiphenyl methane derivatives ; Preconcentration from urine ; UV and electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the title compounds 4,4′-DADPM, MOCA, 3,3′-DCB, 4-ADP and 4-ADPA listing on the EPA priority pollutant list, an analytical practicable, reliable, reproducible and sensitive procedure is required. Therefore a new method has been developed for the routine determination of these toxic aromatic amines in urine at the ppb level. The quantitative determination of amines is a suitable procedure of occupationally exposed persons. Urine sample preparation is done using simple liquid-liquid extraction followed by a precolumn enrichment (PRP1-material; Hamilton). Breakthrough measurements were done using an enrichment column packed with PRP1 material. The capacities of the studied amines ranged from 21.9mg/g to 96.6mg/g, while influent concentrations differed from 28.3mg/l to 332.0mg/l. The advantages of electrochemical detection regarding to selectivity and sensitivity are clearly indicated in this paper. Separation has been achieved applying reversed-phase-high-performance-liquid chromatography (LiChrosorb RP 18/5μm) followed by electrochemical or UV-detection. The detection limits employing an electrochemical detector at a potential of 1 V range from 2.2ng to 12.1ng. UV detection at 254 nm and 280 nm is about 10–100 times less sensitive. Recoveries from spiked water samples at the 5ppb levels were 75% to 96% respectively. The standard deviation of the developed procedure varies from 5.3% to 14%. Day-to-day repeatability is good.
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  • 82
    ISSN: 1612-1112
    Keywords: Thin layer chromatography ; Column liquid chromatography ; 21H, 23H-Porphine ; Metalloporphyrin complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic mobility of 21H, 23H-porphine and its Ni(II), Cu(II), Zn(II) and Pd(II) complexes were investigated by high-performance thin-layer chromatography on an octadecyl-bonded, silica gel plate with various polar organic solvents including alcohols, acetonitrile, dimethylsulfoxide and propylenecarbonate. The mobility generally decreases according to the central metal ion of the complex as follows: Zn(II)〉(free porphine)〉Ni(II)〉Pd(II)〉Cu(II). Methanol is a good choice of solvent for the separation of these metal porphine complexes. Successful separation of porphine and the four metal complexes is accomplished within 13 min on a LiChrosorb RP-18 column with methanol eluent.
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  • 83
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    Chromatographia 25 (1988), S. 717-720 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromtography ; Antifungla agent ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liqid chromatographic method is reported for the measurement of miconazole in systemic, fungal infectious patients. Pharmacokinetic data are presented for a single patient receiving miconazole therapy. Sample preparation involves protein precipitation by acetonitrile (1:1, vol/vol). Analyses are carried out on a reversed-phae chromatographic system using octadecylsilane stationary phase: a mobile phase consisting of 0.05 M acetate buffer (pH 7.4)acetonitrile (20:80, vol/vol) is used to elaute miconazole is quantified on the basis of ultraviolet absorption at 220 nm. The precision of the method ranged from 3.21% at 0.5 mg/L to 0.85% at 2.0 mg/L. The limit of quantification was established as 0.1 mg/L. Interference from other drugs that are co-adimistered such as amphotericin B, 5-fluorocytosine of ketoconazole and most other comonly encountered drugs was not observed.
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  • 84
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mobile phase composition and column temperature ; Retention prediction ; Polycyclic aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the logarithmic capacity factor measured in reversed-phase liquid chromatography and the operating conditions including the mobile phase composition and the column temperature is investigated. The strategy described herein can offer the possibility to predict the retention of polycyclic aromatic hydrocarbons without any experiments and standard materials, by utilizing equations describing the relationships between retention, temperature, mobile phase composition and physicochemical properties of the solutes previously stored in the program of the microcomputer-assisted retention prediction system. This concept is one of the most promising techniques for the optimization of the separation conditions in reversed-phase liquid chromatography.
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  • 85
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fractional factorial experimental designs ; Ruggedness test ; Method validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Recently much attention has been directed to the validation of analytical methods. The level of validation will depend on the method application. If a method is developed for general use, for instance by different analysts, instruments or laboratories, then the effect of these changes need evaluation. This is normally referred to as ruggedness testing, where the limitations of the method to changes in the specified conditions are examined. This paper examines the use of Plackett-Burman fractional factorial experiment designs for ruggedness testing in high performance liquid chromatography (HPLC). The ability of these designs to identify confounding effects is applied to the stability indicating analysis of Salbutamol and its major degradation product, AH4045. The results show that confounding effects, proving extremely pertinent to HPLC, can be identified. The assay proved rugged to most tested changes although not to the use of column packing material from different manufacturers.
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  • 86
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    Chromatographia 22 (1986), S. 231-234 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column reactor ; Crosheted PTFE construction ; Photochemical reaction detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Construction of crocheted photochemical reactors for use in high performance liquid chromatography is described. The design of these reactors is optimal for low intensity light sources because of their cylindrical configuration. Band broadening is minimized by the use of tightly crocheted narrow bore tubing and fittings modified to reduce dead volume. These reactors are suitable for most post-column photochemical reactions with the additional possibility of serving as mixing/delay coils, deoxygenation devices for electrochemical detectors, and as low dispersion detector cells for chemiluminesckent reactions.
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  • 87
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    Chromatographia 23 (1987), S. 31-32 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gonadal steroids ; Epimers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic separation of biologically active epimeric steroids was carried out using a combination of normal and reversed phases. Testosterone (17β-OH) was separated from its 17α-OH epimer epitestosterone using a normal phase silica column whereas their reduced 5α-metabolites were separated on a reversed phase system. The separation of other gonadal steroids including the epimers 20α- and 20β-hydroxypregn-4-en-3-one is also discussed. The technique is particularly useful for separating mixtures of naturally occurring steroid epimers prior to radioimmunoassay.
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  • 88
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ammonium acetate buffer eluent ; Chlorophylls and degradation products ; Marine phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An RP-HPLC procedure which separates chlorophylls and their degradation products is described. By employing an amonium acetate buffered mobile phase and a linear gradient elution, complex mixtures of chloroand phaeopigments are separated in less than 30 minutes. The method has been applied to the control of chlorophyll enzymatic degradation in cultures of two algal species, and has also been successfully used in the analysis of algal xanthophylls.
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  • 89
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkyl-bonded phases ; Retention behaviour ; Ligand density ; n-alkyl chain length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two series of bonded phases were synthesized employing LiChrospher Si 100, 10 μm and n-alkyldimethylmonochlorosilanes as silanizing reagents. In series A the n-alkyl chain length, n, of the bonded phase was varied between 1 and 20 at a constant ligand density of 3.5±0.2μmol·m−2. In series B the ligand density, d, was gradually changed from 0 to 4.1μmol·m−2 on the C1, C4, C6, C8 and C18 bonded phases, respectively. The capacity factors of benzoic acid esters and anilines as solutes were found to increase linearly with the n-alkyl chain length of packings at constant eluent composition (series A) up to a so-called critical chain length, ncrit, where the capacity factor remained constant. ncrit was in the range from 11 to 14. The same pattern was observed when plotting the solute capacity factor against the ligand density of the packing at constant n and constant eluent composition (series B). The critical ligand density, αcrit, varied between 2.3 and 3.2 μmol·m−2 depending on n and the solute. Furthermore, solute retention was slightly higher on RP packings with an even number of carbon atoms in the alkyl chain than on those with an odd number. These findings are consistent with the results of Berendsen and de Galan (J. Chromatogr., 196, 21 (1980)), Dill (J. Phys. Chem., 91, 1980 (1987)) and Simpson and Lau (to be published). The observed phenomena reflect the dynamic structure of RP silicas which are related to the mobility of solvated n-alkyl chains. Due to the lack of a precise conformational analysis of the surface of RP silicas, a semiquantitative model was applied to interprete the described dependencies.
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  • 90
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Behaviour of metal complexes ; Solvophobic theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of Cu(II), Fe(II), Ni(II) and Co(II) complexes with 4-(2-pyridylazo)resorcinol was studied. The experimental results were very sensitive even to less obvious operational parameters like the kind of the cation (sodium or ammonium) of the phosphate salt used as buffer. The puzzling pattern of the data obtained was interpreted in terms of the equations formulated by Horvath's ‘olvophobic” theory which correlates the capacity factors of the solutes with the surface tension of the mobile phase. A satisfactory rationalization of the data was obtained together with qualitative information on the stoichiometry and charge state of metal complexes. Useful suggestions about the direction to address the experimental work in order to obtain the best results was also obtained.
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  • 91
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand Exchange ; Diethylenetriaminepentaacetic acid ; Transition metal ion separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Basic alumina-bonded diethylenetriaminepentaacetic acid (DTPA) has been utilized for the separation and preconcentration of some transition metal ions on the basis of ligand exchange. Breakthrough capacity and rate of sorption have been studied. The distribution coefficients of 16 transition metal ions have been determined in demineralized water, 0.01 M sodium citrate and in four different pH systems. On the basis of differences in Kd values some quantitative separations of metal ions have been achieved. The greater selectivity behaviour (higher Kd values) of the adsorbent for Pt(IV)and Cr(III) has been utilized for their preconcentration in the presence of other metal ions. The method has been employed for the recovery of Pt(IV) and Cr(III) from tapwater and sea-water samples.
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  • 92
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gel permeation chromatography ; Cheese peptides ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The nitrogen fraction from cheese, soluble in phosphotungstic acid has been analyzed by gel permeation and high performance liquid chromatography. Elution profiles of this fraction on Sephadex G-10 show that there are no peptides of molecular weight higher than 700 daltons. Six fractions have been obtained. The first one has the peptides and some amino acids. Fractions II to VI contains mostly free amino acids. Fraction I has been separated into many peaks by HPLC. Six or seven of these peaks are presumed to correspond to peptides.
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  • 93
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Small-bore packed columns ; Air pollutants ; PAH, nitro and oxy-PAH ; Aldehydes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation of small bore columns (1 mm i.d.) packed with reversed-phase materials is described. High efficiency (Hmin=2 dp), coupled with a small C term (0.005 sec) have been obtained so that high speed can be combined with sufficient resolution for the separation of complex organic mixtures. These columns have been used for the separation of air pollutants dispersed in different matrices (air, particulate matter and rain water). Practical applications include the determination of aldehydes in air and emission samples, PAHs, nitrated and oxygenated PAHs in dust sampled from the stack of an industrial emission or collected in a urban area and the analysis of organic components dissolved in rain water collected at a rural site. Specific detection of these pollutants has been achieved by connecting small bore columns to UV absorbance, voltammetric and fluorimetric detectors. Mass spectra of some specific components have been recorded using the off-line technique.
    Type of Medium: Electronic Resource
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  • 94
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 23 (1987), S. 825-828 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gasoline ; Single-ring aromatic hydrocarbons ; Polycyclic aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This work reports a rapid and easy procedure for the analysis of the aromatic fraction in gasoline. No sample pretreatment is required, since the gasoline is diluted in methanol and directly injected into a liquid chromatograph. A spectrophotometer detector and a spectrofluorimeter detector are used in series. The procedure has been applied to a large number of Italian and European refined gasoline samples.
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  • 95
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 27 (1989), S. 27-30 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1,ω-Di(alkoxy)-polysulphides ; Retention contributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of S2Cl2 with alcohols yields products, the reversed-phase liquid chromatograms of which are similar to those of dialkyl-polysulphides RSnR, i.e., they represent homologous series. Four of the products were identified via GC-MS as 1,ω-di(alkoxy)-polysulphides having the general structure ROSnOR. Retention contributions of alkyl groups R and sulphur atoms in the −Sn — chain are not much different from values observed with polysulphides. The effect of oxygen, however, is only about −100 index units per O atom, while in dialkyl ethers values of −500 units have been reported.
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  • 96
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 27 (1989), S. 5-14 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention behaviour ; Column parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of small molecules on reversed phase or other hydrophobic stationary phases can be represented by k′ values of members of a homologous series at varying solvent compositions. The evaluation of simple linear relationships leads to the introduction of a set of four parameters that contain all the information about retention behaviour of this homologous series in the binary solvent system chosen. It is possible to extrapolate to a hypothetical non-hydrophobic molecule and a solvent, the polarity of which equals that of the stationary phase, to characterize the properties of the stationary phase — eluent system. In addition, a chromatographic method for determination of the phase ratio of the column is proposed.
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  • 97
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 23 (1987), S. 109-111 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal and reverse phase ; Aldicarb ; Aldicarb sulfoxide ; Aldicarb sulfone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Aldicarb, aldicarb sulfoxide, and aldicarb sulfone were chromatographed on an octyl-silica bonded-phase column and on an unmodified silica column using acetonitrile/water mobile phases. The elution order of the analytes from the silica column was different from that using the octyl-silica bonded phase and allowed confirmation of residues of aldicarb sulfoxide in citrus nectar. Isocratic elution of the unmodified silica column allowed rapid sample throughput.
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  • 98
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand-exchange chromatography ; Chiral bonded phase ; Racemate resolution ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolution of racemates on chiral chemically bonded silica gel by high-performance ligand-exchange chromatography is described. The stationary phase was prepared by bonding (−) trans 1,2 cyclohexanediamine to silica gel through the coupling agent 3-glycidoxypropyl silane. The resolution of several α-amino acids and of compounds of pharmaceutical interest is reported.
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  • 99
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange separation ; Preparative separations ; Human chorionic gonadotropin hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatography (HPLC) method was developed for the purification of 50mg crude human chorionic gonadotropin (HCG) hormone sample in one chromatographic run on a 250×10 mm SERVA DEAE Poliol-Si-500 column. During the 60-minute linear gradient of 0.05 M sodium sulfate, 0.05 M sodium hydrogen sulfate and 0.05% (v/v) acetonitrile in buffer “B” complete separation was accomplished in 40 min. Identity and purity of the fractions were checked by SDS electrophoretic method. The eluted HCG fractions were dialyzed for 24 hours to remove the buffer salts and liophilized. The activity of the hormone did not decreased significantly during the purification procedure.
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  • 100
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bovine milk ; Multivariate optimization ; Glycerophospholipids ; Molecular species separation ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The molecular species profile, representing the fatty acid combinations on the glycerol backbone, is the most fundamental description of an intact glycerophospholipid class and provides a key to understanding its functional characteristics. We have developed a powerful RP-HPLC method for the separation of molecular species, including so-called “critical pairs”, of natural mixtures of 1,2-diacyl-sn-glycero-3-phosphocholine 1,2-diacyl-sn-glycero-3-phosphoethanolamine from bovine milk and other natural sources. We have used a novel multivariate development and optimization strategy to locate the region of optimum separation conditions within a prechosen domain of the chromatographic parameter space.
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