Flow injection analysis at μl/min flow rates

The characteristics of knitted open tube (KOT) figure eight reactors and coil reactors at l/min flow rates were compared using plate height (H) calculations and peak height measurements. Peak broadening independent of flow rate was seen for the figure eight KOT but not the coil at flow rates of 150–300 l/min. Below 150 /min, the plate height values of both reactors were inversely proportional to flow rate. It was concluded that a 0.5-m KOT figure eight reactor is the most effective way to introduce delay time for a 1 1 injection size and tubing of 0.3 mm I.D. Enhancement of peak height response was particularly pronounced at flow rates less than 100 l/min.     

Thermal analysis of magnesium hydroxide

Natural brucite and two precipitated Mg(OH)₂ samples were analysed in a simultaneous TG-DTG-DSC analyser. The initial dehydroxylation temperature of natural brucite is lower than those of the precipitated samples, but the maximum and final temperatures of the former are higher than those of the latter. The maximum temperatures of individual samples obtained from DTG and DSC curves are almost the same. Heats of reaction derived from peak areas for the three samples are not exactly the same, as they are influenced by the specific surface area of the individual sample. Activation energies deduced by Freeman and Carroll's method are very different from one another. This is attributed to the difference in pressure when the sample is crimped. A linear relationship is observed between the deduced activation energy and the specific height of the DSC peak.

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Zusammenfassung Natürlicher Brucit und zwei gefällte Mg(OH)₂-Proben wurden in einem simultanen TG-DTG-DSC-Analysator geprüft. Die Anfangstemperatur der Dehydroxylierung des natürlichen Brucits ist niedriger als die der gefällten Proben, doch sind Maximal- und Endtemperaturen des ersteren höher als jene der letzteren. Die an Hand von DTG und DSC-Kurven erhaltenen Maximaltemperaturen der einzelnen Proben sind fast identisch. Die aus den Peakflächen der drei Proben errechneten Reaktionswärmen sind nicht genau dieselben, da sie von der spezifischen Peakfläche der einzelnen Proben beeinflußt werden. Die mittels der Methode von Freeman und Carroll abgeleiteten Aktivierungsenergien sind von einander sehr verschieden. Sie werden den Unterschieden im Druck bei dem Schrumpfen der Probe zugeschrieben. Ein linearer Zusammenhang zwischen der abgeleiteten Aktivierungsenergie und der spezifischen Höhe der DSC-Peaks wurde beobachtet.

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Résumé La brucite naturelle et deux échantillons de Mg(OH)₂ précipités ont été étudiés par TG-TGD et DSC simultanées. La température initiale de la déshydroxylation de la brucite naturelle est plus faible que celle des deux échantillons précipités, mais les températures maximale et finale de déshydroxylation de la brucite sont plus élevées que celles des échantillons précipités. Les chaleurs de réaction déduites de l'aire des pics DSC des trois échantillons ne sont pas exactement les mêmes, puisqu'elles sont influencées par l'état de surface des échantillons individuels. Les énergies d'activation trouvées en appliquant la méthode de Freeman et Carroll sont très différentes les unes des autres. Elles sont attribuées à la différence de pression au niveau de l'échantillon. On a observé une relation linéaire entre l'énergie d'activation déduite et la hauteur spécifique du pic DSC.

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Mg(OH)₂ -- . , , - , . - , , . , , , , . , —, , . - .

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The authors wish to thank Dr. T. C. W. Mak, Department of Chemistry, The Chinese University of Hong Kong, for taking the X-ray diffraction data.     

Critical behavior and interfacial tension of mixtures of propylene glycol and ethylene glycol oligomers

This investigation presents an analysis of the critical behavior of mixtures of oligomers of propylene glycol, PG₁₇, and ethylene glycol, EG_n, withn=3, 4, 5, 6.4, 8.7, 12.1 and 22.1. The critical coordinates, _c andT _c were determined from the phase diagrams. The critical compositions compare very well with the Huggins-Flory predictions. The interaction parameter _n is around one for EG₃, EG₄ and EG₅ and it increases up to two for the higher oligomers. The break in the interaction parameter also corresponds to a minimum in the critical temperature. The phase diagrams and the interfacial tension were used to get the critical exponents and , respectively. The data were analysed with two approaches. First, from the temperature dependence of the length of the tie-lines and of the interfacial tension up to the upper critical solution temperature, UCST. Second, with the data at 30°C using the critical temperature of the systems as the variable. The first method led to =0.39±0.05 in good agreement with the result of the second method, =0.37±0.04. The exponents for the interfacial tension, , determined with the first method for PG₁₇ with EG_6.4, EG_8.7 and EG_12.1 are =1.66±0.11, 1.46±0.25 and 1.73±0.18, respectively. The second method led to =1.17±0.14. The critical exponents are compared to mean field and ising-3D predictions.     

μSr studies of free radicals in the gas phase

Muonium (Mu=₊+e^-) is the bound state of a positive muon and an electron. Since the positive muon has a mass about 1/9 of the proton, Mu can be regarded as an ultra light isotope of hydrogen with unusually large mass ratios (MuHDT=1/9123). The muon spin rotation technique (SR) relies on the facts that (1) the muon produced in pion decay, ^{+ +} + , is 100% spin polarized and (2) the positron from muon decay is emitted preferentially along the instantaneous muon spin direction at the time of the muon decay.In transverse field SR (TF-SR), the precession of the muon spin in muonium substituted radicals is directly observed by detecting decay positrons time differentially. From observed radical frequencies, the hyperfine coupling constants (A ) of C₂H₄Mu, C₂D₄Mu,¹³C₂H₄Mu, C₂F₄Mu, and C₂H₃FMu are determined. In the longitudinal field avoided level crossing (LF-ALC) technique, one observes the resonant loss of the muon spin polarization caused by the crossing of hyperfine levels at particular magnetic fields. The LF-ALC method together with the information onA obtained from TF-SR allows one to determine the magnitude and sign of the nuclear hyperfine constants at - and -positions. Results are compared with hydrogen substituted ethyl-radicals and isotope effects are discussed.     

Colloid chemical studies of polystyrene latices polymerized without any surface-active agents

Summary The influence of secondary minimum for the stability of spherical colloid has been studied using a series of soap-free polystyrene latices from 350 m to 1400 m in diameter.The critical flocculation concentration (c. f. c.) and the zeta-potential at the c. f. c. for each latex were determined with several salts of different ionic valencies. The values of c. f. c. varied with the particle size, reaching a maximum value at 750 m and then decreasing gradually with the diameter.Another phenomenon detected in the experiment was the complete reversibility of coagulation which was observed only in the cases of large size latices, i. e., the coagulates of large size particles were fully redispersed in the solution by stirring. The time-dependence of their sedimentation curves was reproducible.These experimental results could not be explained by the simple theoretical consideration for stability of suspension. The satisfactory explanation is given only using the term of secondary minimum of interaction potential, i. e., the origin of coagulation was shifted from the ordinary primary minimum to the shallow secondary minimum at about 750 m of the particle diameter.

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Zusammenfassung Der Einfluß des Sekundär-Minimum auf die Stabilität von Kolloiden wurde an seifenfreien Polystyrol-Latex-Suspensionen mit einem Durchmesser von 350 m bis 1400 m untersucht. Die kritische Flockungskonzentration (c. f. c.) und das Zeta-Potential bei c. f. c. wurde mit verschiedenen Salzen bestimmt.Der Wert von c. f. c. ändert sich mit der Teilchengröße.Ein weiterer wichtiger experimenteller Befund ist die vollständige Reversibilität der Flockung bei größeren Latices.Derartige Versuchsergebnisse können durch das Sekundär-Minimum befriedigend erklärt werden.

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With 7 figures in 10 details and 2 tables     

Capillar-Gas-Chromatographie mit ECD- und MS-Detektion zur quantitativen Bestimmung von Pentachlorphenol im menschlichen Plasma und Harn

Zusammenfassung Pentachlorphenol (PCP) wurde im Plasma und Harn mittels Capillar-Gas-Chromatographie und ECD-Detektion erfaßt. Die parallele Analyse mit einem massenselektiven Detektor erbrachte nahezu identische Werte (r=0,9978). Die Nachweisgrenzen lagen bei ca. 5 g PCP/l Harn bzw. ca. 10 g PCP/l Plasma. Die Untersuchung von 27 Personen ohne beruflichen bzw. besonderen usuellen Kontakt mit Pentachlorphenol ergab mediane PCP-Konzentrationen im Plasma von 28 g/l (95.0 Perzentil 149 g/l) bzw. im Harn von 10 g/l (95.0 Perzentil 55 g/l).

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Determination of pentachlorophenol in human plasma and urine samples by capillary gas chromatography with ECD- and MS-detection

Summary Pentachlorophenol (PCP) levels in plasma and urine samples were determined by capillary gaschromatography and EC-detection. The results of the parallel analysis of samples with a selective mass detector correlated well (r=0.9978). The detection limits were around 5 g PCP/l urine and around 10 g PCP/l plasma respectively. A study on 27 persons occupationally not exposed to PCP or without a known special ecological intake of PCP showed median PCP levels of 28 g/l plasma (95.0 percentile: 149 g/l plasma) and 10 g/l urine (95.0 percentile: 55 g/l).

     

Cadmium induced changes of the metabolic activity of the freshwater snailPlanorbis corneus estimated by direct calorimetry

By use of f1ow-microcalorimetric studies the effect of cadmium in the sublethal concentration range (0.5-h LC_{5 0} is 1.69 mg/l) on the metabolic activity of the freshwater snailPlanorbis corneus was revealed. The high toxicity was confirmed by the change in the heat production rate (mean value is 453 W/g fresh weigth) in a cadmium perfusate down to a concentration of 0.01 g/l. The decrease in heat output depended on the cadmium concentration and amounted from 19% at 0.01 g/l to 88% at 1000 g/l. The microcalorimetric method proved to be a useful continuous-f1ow technique to assess qualitatively and quantitatively the toxic effects of cadmium on an aquatic organism already 4 hours after exposure.

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Zusammenfassung Mit Hilfe der Flow-Mikrokal orimetrie wurde die Uirkung von Cadmiumchlorid im subletalen Konzentrationsbereich auf die Stoffwechselaktivitat der SüwasserschneckeP1anorbis corneus untersucht. Die Wärmeproduktion der Tiere sank im Mittel von 435W/g Frischgewicht bei einer Cadmiumkonzentrat i on von 0.01 g/l auf 81Z und bei 1000 g/1 auf 19Z. Die Kalorimetrie eruies sich als eine nützliche Flow-Technik, mit der die Toxizität von Cadmium qualitativ und quantitativ bereits 4 Stunden nach der Exposition erfat werden kann.

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$ /LC₅₀=1,69 // planorbis corneus. $ / 453 / 0,01 /. 19% 0,01 / 88% 1000 /. , $ $ .

     

Production of certified reference material

Summary Carbon has been determined in 31 European reference steels in the range of 11–2561 g/g C, using an absolute calibration method.High-purity calcium carbonate was used as the calibration material and weighing was carried out by means of a balance with extremely small weighing error. Both synthetic calibration samples and test samples were processed alternatingly under identical conditions, and the analyses were completed in the shortest possible time.In 28 of the cases examined, results were lower than the certificate values, by an average of 27 g/g. The interval of uncertainty of the accuracy was 6 g/g (probability 99%).

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Herstellung zertifizierter ReferenzmaterialienGenaue Bestimmung von Kohlenstoff in Stählen im Bereich von 11–2561g/g

Zusammenfassung Die Kohlenstoffgehalte von 31 europäischen zertifizierten Referenzstählen im Arbeitsbereich von 11–2561 g/g Kohlenstoff wurden durch absolute Eichung überprüft.Die hinreichende Reinheit des Eichmittels Calciumcarbonat wurde sichergestellt und ein Wägesystem mit einem hinreichend kleinen Wägefehler benutzt.Das gleiche Verhalten von synthetischen Eichproben und Analysenproben im Analysenprozeß wurde hergestellt und beide Probearten wechselweise unter konstanten Systembedingungen innerhalb kürzester Zeitspanne untersucht. In 28 der untersuchten Fällen wurden im Mittel um 27 ppm tiefere Werte gefunden als in den Zertifikaten angegeben. Das Unsicherheitsintervall der Richtigkeit der gefundenen Werte lag mit einer Wahrscheinlichkeit von 99% im Mittel bei 6 g/g.

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Abbreviations CRM Certified reference material - ppm g/g The author thanks Mr. E. Weichert for his excellent direction of the practical work.     

A sensitive method for the determination of nitroamines in alcoholic beverages

Summary Nitrosamines in alcoholic beverages and malted barley were analysed by adsorption from the gas phase onto a porous polymer trap of Chromosorb 104 and subsequent desorption of the trapped compounds directly to a gas chromatograph fitted with glass capillary column and alkali-FID. The detection limit for NDMA was 0.05 g/l in beer samples and 0.3 g/kg in malted barley.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Chlorine and bromine contents in tobacco and tobacco smoke

The chlorine and bromine contents in tobacco and tobacco smoke in both the particulate and gaseous phases were studied by neutronactivation analysis. Methyl chloride and methyl bromide concentrations were measured in the gaseous phase by gas-liquid chromatography — mass spectrometry. The chlorine and bromine contents in nine brands of cigarettes were on the average as follows: Tobacco—6600 ppm chlorine and 110 ppm bromine. Cigarette smoke, particulate phase—68 g chlorine and 1 g bromine per cigarette. Cigarette smoke, gaseous phase—90 g chlorine and 5 g bromine per cigarette. In the gaseous phase methyl chloride accounted for 60% of the total chlorine and methyl bromine for 80% of the total bromine.     

Peculiarities in oxidative conversion of methane to C2 hydrocarbons over CaO?CaCl2 catalysts

Experimental data for the oxidative dimerization of methane over CaO–CaCl₂ systems indicate that C₂ hydrocarbons are formed with the participation of chlorine generated by the catalyst surface under the effect of a reaction medium. A heterogeneous-homogeneous scheme for this process is suggested.

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CaO–CaCl₂ , C₂- , . - .

     

Spectrofluorimetric determination of traces of indium with 5-chiorosalicylidene-o-aminophenol

A Spectrofluorimetric method for microdetermination of indium, based on the formation of a fluorescent 21 (ligand:metal) complex between In (III) and 5-chlorosalicylidene-o-aminophenol at an apparent pH of 4.70 in an aqueous-ethanol medium (50% v/v ethanol) is proposed. The calibration graph is linear over the range 10.0–80.0 g/l, the relative standard deviation 2.7% and the detection limit 1.5 g/l. The method has been applied to the determination of indium in synthetic samples and natural waters.     

C-C bond formation at polynuclear metal centers

Studies on C-C bond formation between simple hydrocarbon species such as CH₂, C=CH₂, CH=CH₂, CH₂=CH₂, CH₂=C=CH₂ and CHCH at a diruthenium center suggest that the process is promoted when the dimetal center can readily compensate for the two electrons lost in the formation of the new C-C bond. Thus, whereas -CH₂ and ethene combine only under forcing conditions, the combination of -CH₂ with allene or ethyne, which have additional -electrons available for coordination, occurs readily at room temperature. Likewise, the availability of uncoordinated -electrons in -C=CH₂ allows vinylidene to link rapidly with ethene at room temperature. Alkyne complexes [Ru₂(CO)(-RCCR)(-C₅H₅)₂] (R=CF₃ or Ph) react only under vigorous conditions with additional alkyne to give [Ru₂(CO)(-C₄R₄) (-C₅H₅)₂], but give these same species at room temperature in the presence of acid, shown to be due to the intermediacy of highly reactive 30-electron -vinyl cations. Thermally, alkyne linking proceedsvia three-alkyne species [Ru₂(-C₆R₆)(-C₅H₅)₂] to a four-alkyne complex [Ru₂(-C₈R₈)(-C₅H₅)₂], containing an unprecedented C₈ ligand composed of a C₆ ring with a C₂ tail. Treatment of [Ru₂(CO)(-RCCR)(-C₅H₅)₂] with unsaturated metal fragments gives trimetal complexes such as [Ru₃(CO)₅(₃-CF₃CCCF₃) (-C₅H₅)₂]. The MeCN derivative of this species undergoes unusual linking processes on reaction with additional alkyne to giveinter alia [Ru₃(CO)₃(₃-CCF₃){₃-C₃(CF₃)₃}(-C₅H₅)₂], arising from alkyne cleavage, and [Ru₃(CO)₃{₃-C₄(CF₃)₂(CO₂Me)₂}(-C₅H₅)₂], a closo-pentagonal bipyramidal Ru₃C₄ cluster.     

Development and Validation of an HPTLC–Densitometric Method for Determination of ACE Inhibitors

A high-performance thin layer chromatographic method coupled with densitometric analysis has been developed for measurement of benazepril and cilazapril, both pure and in their commercial dosage forms. The active substances were extracted from tablets with methanol (mean recovery 102%) and chromatographed on silica gel 60 F₂₅₄ HPTLC plates in horizontal chambers with ethyl acetate–acetone–acetic acid–water, 8:2:0.5:0.5 (v/v), as mobile phase. Chromatographic separation of these ACE inhibitors was followed by UV densitometric quantitation at 215 nm. Calibration plots were constructed in the range 0.4 to 2.0 g L^–1 for benazepril (2.0–10.0 g spot^–1) and from 0.5 to 1.5 g L^–1 for cilazapril (4.0–12.0 g spot^–1) with good correlation coefficients (r 0.990). The method was used to determine benazepril and cilazapril in pharmaceutical preparations with satisfactory precision (1.4% < RSD < 5.6%) and accuracy (1.7 < RE < 5.1).     

Zur coulometrischen Chloridbestimmung in konzentrierten S?uren mit potentiometrischer Indizierung und Polarisationsspannungsindikation

Zusammenfassung Die coulometrische Bestimmung geringer Chloridmengen im Gemisch von Methanol und 35%iger Schwefelsäure, 53%iger Phosphorsäure oder 37%iger Perchlorsäure kann ohne den Zusatz eines Leitelektrolyten sowohl mit potentiometrischer Indizierung als auch mit Polarisationsspannungsindikation vorgenommen werden. Das Verfahren mit potentiometrischer Indizierung, bei dem sich das Gesamttitrationsvolumen aus 10 ml Säure und 40 ml Methanol zusammensetzt, erlaubt die Bestimmung von 2,0 g/ml mit einer relativen Standardabweichung von 0,5%. Die kleinste noch bestimmbare Konzentration liegt bei 1,0 g/ml. Eine Erweiterung des erfaßbaren Konzentrationsbereiches ermöglicht die Anwendung der Polarisationsspannungsindikation. Im Gemisch von 1 ml Säure und 8 ml Methanol können noch 0,4 g/ml mit guter Genauigkeit titriert werden. Bei 2,0 g/ml Chlorid beträgt die relative Standardabweichung 2%. Für die Konzentration an der Nachweisgrenze errechnet sich 0,08 g/ml.

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Summary The coulometric estimation of small contents of chloride in a mixture of methyl alcohol and 35% sulphuric, 53% phosphoric or 37% perchloric acids can be performed without adding any supporting electrolyte. Both the two coulometric methods, with potentiometric indication as well as by indicating the end point with two identical electrodes polarized by practically constant current can be used. The potentiometric indication method, whereby the total titration volume consists of 10 ml of acid und 40 ml of methyl alcohol, permits the determination of 2.0 g/ml chloride with a relative standard deviation of 0.5%. The smallest concentration which is just possible to be determined is 1 g/ml. By application of the second coulometric method the estimation limit can be minimized. In a mixture of 1 ml of acid and 8 ml of methyl alcohol, it is possible to titrate 0,4 g/ml. The relative standard deviation for the concentration of 2,0 g/ml has been found to be 2%. The limit of detection is 0.08 g/ml.

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Herrn Prof. Dr. M. von Stackelberg zum 70. Geburtstag gewidmet.

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Wir danken Herrn Chem.-Ing. K. Zinke für seine Mitarbeit.     

Dosage de micro quantités de cuivre bivalent par précipitation en picrate de cupritétrammine

Résumé On propose une méthode de dosage de microquantités de cuivre-II par précipitation sous forme de picrate de cupritétrammine. Cette méthode est fondée sur la précipitation du cuivre-II en présence d'un excès de picrate de sodium en milieu ammoniacal et sur le dosage colorimétrique de l'acide picrique résiduel après extraction sous forme de picrate de bleu de méthylène.Cette méthode permet le dosage de 1 à 10 g de cuivre-II, avec une erreur maximale de ± 5%.La présence des cations zinc (jusqu'à 200g), argent (jusqu'à 500g), cobalt (jusqu'à 50g), cadmium (jusqu'à 100g), nickel (jusqu'à 20,g) et chrome (jusqu'à 50 g) ne gêne pas le dosage.Cette méthode peut servir à doser le cuivre dans les cendres végétales.

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Summary A method is suggested for the determination of micro amounts of copper(II) by precipitation as the picrate of cupritetrammine. This method is based on the precipitation of the copper(II) in the presence of an excess of sodium pierate in an ammoniacal milieu and on the colorimetric determination of the residual picric acid, after extraction in the form of the picrate of methylene blue. This procedure permits the determination of from 1 to 10g of Cu(II) with a maximum error of ± 5%.The determination is not impaired by the presence of the cations: zinc up to 200 g), silver (up to 500g), cobalt (up to 50g), cadmium (up to 100g), nickel (up to 20g), and chromium (up to 50g).This method may be employed for determining copper in vegetable ashes.

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Zusammenfassung Bin Verfahren zur Bestimmung von Mikromengen Kupfer(II) durch Fällung als Kupfertetrammin-Pikrat wird vorgeschlagen. Es beruht auf der Fällung von Kupfer in Gegenwart überschüssigen Natriumpikrats in ammoniakhaltiger Lösung und der kolorimetrischen Bestimmung der restlichen Pikrinsäure nach Extraktion als Methylenblaupikrat. 1 bis 10g Cu(II) lassen sich mit einem maximalen Fehler von ± 5% bestimmen. Die Anwesenheit von < 200g Zn, < 500 g Ag, < 50g Co, < 100g Cd, < 2°g Ni und < 50g Cr stört die Bestimmung nicht. Das Verfahren eignet sich zur Bestimmung von Kupfer in Pflanzenasehen.

     

Elements in car and truck tires and their volatilization upon incineration

The trace metal loading of used car and truck tires and the fractions of the metals volatilized upon incineration of the tire were determined. INAA was chosen due to its multielement analysis capability and its low detection limit for many elements. A high purity planar germanium detector was used. Among the elements measured were, Al (4–150 g/g), Ti (41–730 g/g), V (0.04–0.4g/g), Mg (>80–580 g/g), Zn (1–2.2%) as typical concentrations; also some amounts of antimony, bromine and arsenic have been found. Major differences in elemental concentrations have been observed between the tread and the wall of a tire, and also between different brands.     

Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

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. , . .

     

Radioimmunoassay of somatotropin using second antibody polyethylene glycol combination separation system

We describe a radioimmunoassay procedure for human somatotropin using second antibody — polyethylene glycol (PEG) combination for the separation of antibody bound and free antigen. The assay is done by a single incubation of 18 hours or with one hour pre-incubation and 3 hours post-incubation at room temperature (25 °C) and uses 0.1 m of serum sample. The assay covers a range of 0–40 g/ and has a sensitivity of 0.6 g/ of somatotropin. The assay is validated by inter-assay and intra-assay variations, recovery and parallelism tests.