The crystal structures of α, ω-diaminoalkanecadmium(II) tetracyanonickelate(II)-Aromatic molecule inclusion compounds. V. Toluidine clathrates of the hosts built of the diamines, 1,4-diaminobutane, 1.5-diaminonentane,and 1,8-diaminooctane

The crystal structures have been analyzed for the threeo-toluidine clathrates,catena-[catena--(1,4-diaminobutane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(2/3),4-o,catena-[catena--(1,5-diaminopentane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(3/4),5-o, andcatena-[catena--(1,8-diaminooctane)cadium(II) tetra--cyanonickelate(II)]-o-toluidine(1/1),8-o, for am-toluidine onecatena-[catena--(1,5-diaminopentane)cadmium(II) tetra--cyano-nickelate(II)]-m-toluidine(1/1),5-m, and for ap-toluidine onecatena-[catena--(1,8-diaminooctane)cadium(II) tetra--cyanonickelate(II)]-p-toluidine(1/1),8-p. 4-o crystallizes in the triclinic space groupP,a/Å = 9.806(3),b/Å = 14.388(3),c/Å = 7.725(2), /° = 89.71(2), /° = 89.96(2), /° = 98.12(2),V/ų = 1078.8(5),Z = 2, 3750 reflections,R = 0.056;5-o: tetragonalP4lmmm, (a = b)/Å = 7.485(7),c/Å = 10.06(3),V/ų = 563(2),Z = 1, 573 reflections,R = 0.19;8-o: monoclinicP2/m,a/Å = 11.513(4),b/Å = 7.626(1),c/Å = 7.101(1), /° = 109.63(3),V/ų = 587.2(2),Z = 1, 1682 reflections,R = 0.058;5-m: orthorhombicPbam,a/Å = 12.254(6),b/Å = 20.62(1),c/Å = 7.804(1),V/ų = 1972(1),Z = 4, 2240 reflections,R = 0.059; and8-p: triclinic,P,a/Å = 11.52(1),b/Å = 7.632(3),c/Å = 7.039(4), /° = 88.93(4), /° = 109.71(5), /° = 82.81(9),V/ų = 576.9(6),Z = 1, 2598 reflections,R = 0.042. Their structures are substantially similar to the already-known structure ofcatena-[catena--(1,6-diaminohexane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(1/1): the guest toluidine molecules are accommodated in the cavities formed betweencatena-[cadmium(II) tetra--cyanonickelate(II)] layers bridged by the ambidentate ,-diaminoalkane ligands at the cadmium(II) atoms. The carbon chain length of the ,-diaminoalkane influences the number of cavities per formula unit and the deformation of the metal complex layers.     

Accommodation of an aliphatic guest molecule in hofmann-diaminooctane-type host. A model structure of a pillared intercalation compound

catena-[catena--(1,8-Diaminooctane)cadmium(II) tetra--cyanonickelate(II)]-(1-hexanol)(1/1) has been prepared as the first example of an aliphatic guest clathrate of the Hofmann-type and analogous metal complex hosts. The clathrate crystallizes in the monoclinic space groupP2/m,a=11.470(2),b=7.782(1), andc=6.945(1) Å, =105.29(1)°,Z=1;R=0.043 for 1865 reflections. The structure presents a model of pillared intercalation compounds formed between layers of metal complex sheets pillared by ,-ambidentaten-alkaneskeletal ligands andn-alkyl derivative guests. Supplementary Data relating to this article are deposited with the British Library as supplementary publication SUP 82069 (16 pages).     

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).

     

Spectrophotometric Determination of the Polyiodohalides of Organic Nitrogen-Containing Cations

The following biologically active diiodohalides of organic cations were studied: N-cetylpyridinium, trimethylbenzylammonium, triethylbenzylammonium, and N,N-dimethylmorpholinium diiodochlorides; N-cetylpyridinium, tetramethylammonium, tetrabutylammonium, and N,N-dimethylmorpholinium diiodobromides; and N,N-dimethylmorpholinium and butyroylcholinium triiodides. A simple and rapid procedure was proposed for the determination of the above compounds; it is based on the conversion of organic diiodohalides into the corresponding triiodides (_{300 nm} 4 × 10⁴; _{370 nm} 2 × 10⁴) in the presence of excess potassium iodide (RSD 2%). An extraction–spectrophotometric method was developed for the quantitative determination of the biologically active compounds in pharmaceutical dosage forms based on their ion associates with anionic dyes, erythrosine (m _min = 1.25–3.30 g; RSD 3%) and Bromothymol Blue (m _min = 3.85 g; RSD = 3%), or a cationic dye—1,3-dimethyl-2-(4-morpholinophenyl)azobenzimidazolium phenylsulfate (m _min = 2.32–8.26 g; RSD 4%). The developed procedures were used for monitoring drug substances in model pharmaceutical preparations (RSD 4%).     

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.

     

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.     

Chemical microscopy of platinum metals and gold: Reactions with 4,4′-dipyridyldihydrochloride

Summary It has been shown that an acid solution of 4,4-dipyridyldihydrochloride can serve to identify low concentrations of most of the platinum metals and gold in 1-N hydrochloric acid solutions of their chlorides by the separation of characteristic micro crystalline precipitates. The reagent was most effective for palladium(II) and platinum(IV), which could be identified in a 20-l drop of sample containing less than 0.6g of metal. Under the conditions imposed, rhodium (III) was the only platinum metal which failed to yield a precipitate. By contrast, under similar conditions 2,2-dipyridyl failed to yield a crystalline precipitate with rhodium(III), ruthenium (III), and iridium(III). Cupric ion caused the separation of a crystalline complex with 4,4-dipyridyl reagent only at a relatively high metal concentration.

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Zusammenfassung Eine saure Lösung von 4,4-Dipyridyldihydrochlorid eignet sich zum Nachweis geringer Konzentrationen der meisten Platinmetalle und des Goldes in 1-n salzsauren Lösungen ihrer Chloride durch charakteristische Mikrokristallfällungen. Am wirksamsten ist das Reagens gegenüber Pd(II) bzw. Pt(IV), von denen sich weniger als 0,6g in einem 20-l-Tropfen nachweisen lassen. Unter den angegebenen Bedingungen gibt Rh(III) als einziges Platinmetall keinen Niederschlag. Dagegen gibt 2,2-Dipyridyl unter diesen Bedingungen außer mit Rh(III) auch mit Ru(II) und Ir(III) keine kristalline Fällung. Kupfer(II)-ionen bilden mit 4,4-Dipyridyl erst in relativ hoher Konzentration eine kristallisierte Komplexverbindung.

     

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     

Landolt-Reaktionen auf „Chlorgrundlage“ und ihre Anwendung zum Nachweis und zur Bestimmung katalytisch wirkender Spurenelemente. I

Zusammenfassung Gemische aus Ascorbinsäure, Hydrazin oder Zinn(II)-chlorid mit sauren, Chlorat und Chlorid enthaltenden Lösungen reagieren nach Art der bekannten Landolt-Reaktion unter Chlorausscheidung, die sich mit o-Tolidin indizieren läßt. Die Reaktion wird von Vanadin(V), Eisen(III) oder Osmium(VIII) katalysiert. Auf dieser Grundlage lassen sich diese Elemente sowohl chronometrisch wie auch mit Hilfe der Simultan-komparationsmethode bestimmen. Die Nachweisgrenzen liegen bei 0,1g V, 0,3g Fe bzw. 0,1g Os. Die Arbeitsvorschrift für die Analyse im Konzentrationsbereich 1 bis 10g/5 ml wird angegeben. Der relative Fehler bei der Simultankomparationsmethode liegt innerhalb 2%. Der Einfluß fremder Ionen wurde untersucht.

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Summary Mixtures of ascorbic acid, hydrazine or tin(II) chloride react with solutions containing acids, chlorate and chloride in accord with the familiar Landolt reaction, with liberation of chlorine. The latter can be detected witho-tolidine. The reaction is catalyzed by vanadium(V), iron(III) or osmium(VIII). On the basis of this behavior, it is possible to determine these elements chronometrically and also with the aid of the simultaneous comparation method. The detection limits are 0.1g V, 0.3g Fe, or 0.1g Os. The working directions are given for the analysis in the concentration range from 1 to 10g/5 ml. The relative error in the simultaneous comparation method is within 2%. The influence of foreign ions was studied.

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Résumé Les mélanges d'acide ascorbique, d'hydrazine ou de chlorure d'étain-II avec des solutions acides contenant chlorate et chlorure réagissent suivant la réaction bien connue de Landolt avec libération de chlore mis en évidence par l'o-tolidine. La réaction est catalysée par le vanadium-V, le fer-III ou l'osmium-VIII. Sur ce principe, on peut doser ces éléments aussi bien par chronométrie que par la méthode de comparaison simultanée. Les limites de dilution se situent à 0,1g V, 0,3g Fe ou 0,1g Os. On indique le mode opératoire de l'analyse dans le domaine de concentration de 1 à 10g/5 ml. L'erreur relative pour la méthode de comparaison simultanée est inférieure à 2%. On a étudié l'influence des ions étrangers.

     

Direction of the action of glycosidases fromLimnaea stagnalis on the carbohydrate groups of the (Fc)5 region of immunoglobulins M

The action of the combined glycosidases fromL. stagnalis on the carbohydrate groups of two monoclonal immunoglobins M (Waldenström's disease) — IgM_El (I) and IgM_Ser (II) — has been studied by the semiquantitative evaluation of densitograms of glycopeptides after their separation by disc electrophoresis in polyacrylamide gel. The accessibility of the oligosaccharide groups (OGs) to the action of the glycosidases according to the positions of the OGs in a particular domain of the (Fc)₅ region of a IgM decreases for (I) in the sequence C3 C4 > hinge, and for (II) in the sequence hinge > C4 > C3. The difference in the accessibilities of the OGs (I) and (II) is apparently explained by differences in the conformations of (I) and (II). A hypothesis has been put forward concerning the possibility of the partial degradation of (II) by the accompanying proteases.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–375, May–June, 1984.     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.

     

Proliferation and Insulin Secretion Function of Mouse Insulinoma Cells Encapsulated in Alginate/Sol-Gel Synthesized Aminopropyl-Silicate/Alginate Microcapsule

Alginate/aminopropyl-silicate/alginate microcapsules, ca. 15 m in membrane thickness and ca. 500 m in diameter, were prepared via sol-gel process. The aminopropyl-silicate membrane was derived from two silicone alkoxide precursors, tetramethoxysilane and 3-aminopropyl-trimethoxysilane on Ca-alginate micro gel beads. Pancreatic -cell line (MIN6) cells were encapsulated in the microcapsule. The encapsulated MIN6 cells proliferated and formed spheroidal tissues in vitro. The diameter of the MIN6 spheroids increased to approximately 250 m with an increase in the incubation period until the day 35. Storeptozotocin-induced diabetic mice became normoglycemia after implantation of the MIN6-enclosing microcapsules. The normoglycemic state remained until the retrieval of the implanted microcapsules for 1 month. These results indicate that the potential use of the alginate/aminopropyl-silicate/alginate microcapsule as a vehicle for a genetically engineered cell-enclosing therapeutic material delivery system.     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.     

Redox Properties of Trinuclear Osmium Carbonylhydride Clusters with Unsaturated Ligands

Schemes of redox transformations were proposed for osmium carbonylhydride clusters: trinuclear (-H)Os₃(-CR = CHR')(CO)_{1 0} (R = R' = H, Ph; R = H, R' = Ph), (-H)₂Os₃(₃-L)(CO)₉ (L = C = CHPh, CHCPh), tetranuclear CpMnOs₃ (-CH = CHPh)(-H)(-CO)(CO)_{1 1}, and trinuclear Os₃(₃-C = CHPh)(CO)₉. Two-electron reduction of the trinuclear clusters results in elimination of the unsaturated ligand with preservation of the metal framework.     

Synthesis of Osmium–Palladium Mixed-Metal Clusters with 2-(diphenylphosphino)Pyridine as a Bridging Ligand

Reaction of the pentanuclear cluster [Os₅C(CO)₁₄(PPh₂py)] in CH₂Cl₂ with 1.2 equivalents of Pd(MeCN)₂Cl₂ led to the high-yield synthesis of the new osmium–palladium carbonyl cluster [Os₅PdC(CO)₁₄(-Cl)Cl(-PPh₂py)] 1. Cluster 1 is thermally unstable and converts slowly in refluxing CHCl₃ to [{Os₄C(CO)₁₀(-Cl)(-PPh₂py)}(₄-Pd){Os₄C(CO)₁₂(-Cl)}] 2 and [{Os₄ (₅-C)(CO)₁₂(-Cl)}₂(-Pd₂Cl₂)] 3 in 4% and 67% yield, respectively. Reaction of 1 with iodine gave [Os₅PdC(CO)₁₄(-Cl)I(-PPh₂py)] 4 and [{Os₄(₅-C)(CO)₁₂(-I)}₂(-Pd₂I₂)] 5 in moderate yields. All complexes have been characterized by spectroscopic and single-crystal X-ray diffraction analysis.     

TLC technique for the detection and determination of gamma- BHC in biological material

Summary Five isomers present in technical benzene hexachloride were successfully separated by TLC on silica-gel G impregnated with silver nitrate solution. The -isomer was identified by running a control sample of -BHC. Measurement of the spot area was found suitable for the estimation of 5–20g of-BHC, and was applied to analysis of autopsy tissues. The limit of identification is 0.1g.

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Zusammenfassung Auf mit Silbernitratlösung imprägniertem Kieselgel G konnten dünn-schichtchromatographisch fünf Isomere aus technischem Hexachlorbenzol erfolgreich getrennt werden. Das-Isomere wurde mit Hilfe einer Vergleichsprobe identifiziert. Die Planimetrie der Flecken eignet sich zur Schätzung von 5–20 g-Hexachlorbenzol. Die Methode wurde zur Untersuchung von Autopsieproben angewendet. Die Nachweisgrenze beträgt 0,1g.

     

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.     

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).