Simultaneous determination of yohimbine and boldine by first-derivative synchronous spectrofluorimetry

A method for the simultaneous determination of yohimbine and boldine in mixtures by first-derivative synchronous spectrofluorimetry has been developed. The method is based on their native fluorescence in 0.1N sulphuric acid medium. The constant wavelength difference chosen to optimize the determination was =_em -_em=82 nm. Yohimbine was measured at _ex//_em= 285/367 nm, and boldine at _ex/_em=272/354 nm. The range of application is 10–500 g/l for yohimbine and 1–50 g/l for boldine. The method was applied to the determination of yohimbine and boldine in synthetic mixtures and pharmaceuticals, with errors generally 2%. Relative standard deviations were about 2%.Dedicated to Professor Fermin Capitán on his 72th birthday     

Luminescence of dimeric Tl(I)-complexes: Metal-metal interaction in the electronically excited state

Summary Dimeric diethyldithiocarbamatethallium(I) [Et ₂NCS₂Tl]₂ shows a red emission at _max=608 nm which undergoes a huge Stokes shift with regard to the excitation maximum at =246 nm. It is suggested that the emission originates from a sp excited state which is characterized by strong metal-metal bonding.

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Lumineszenz von dimeren Tl(I)-Komplexen: Metall-Metall-Wechselwirkung im elektronisch angeregten Zustand (Kurze Mitt.)

Zusammenfassung Dimeres Thallium(I)diethyldithiocarbamat [Et ₂NCS₂Tl]₂ zeigt eine rote Emission mit _max=608 nm und eine große Stokes'sche Verschiebung im Bezug auf das Anregungsmaximum von =246 nm. Die Emission wird einem sp angeregten Zustand zugeordnet, der durch eine starke Metall-Metall Wechselwirkung charakterisiert ist.

     

2-(α-Pyridyl)-thioquinaldinamide (PTQA)-A novel fluorimetric reagent in inorganic trace analysis. I: The nonextractive,nonquenching fluorescent method for the determination of chromium(VI)

A direct fluorimetric method for determining Cr(VI) in aqueous solutions is described. The nonfluorescent reagent 2-(-pyridyl)-thioquinaldinamide (PTQA) and Cr(VI) interact to produce an intensely fluorescent species [_ex(max) 360 nm; _em(max) 500 nm] showing constant and maximum fluorescence intensity in slightly acidic media (0.18N–1.08N H₂SO₄). The fluorescence attains its maximum value within 5 min and remains unchanged for 24 h. The system obeys Beer's law from 2 ng/ml to 0.8 g/ml of Cr(VI). Over sixty cations, anions and complexing agents are without any effect on the fluorimetric determination of 0.1 g/ml of Cr(VI). The method has been tested with synthetic mixtures, steels, solutions containing both Cr(III) and Cr(VI), and environmental samples.     

Structural Anisotropy of Fractal Aggregates and Its Exhibition in Electrooptical Effects

The first experimental examination of orientational turbidimetric effect [differential orientational spectrum of optical density D() in suspensions of fractal clusters was presented. Experiments were performed for aqueous suspensions of powdered Aerosil OX-50 aggregates ordered by the alternating electric field oriented along or across the unpolarized light beam. Experimental differential spectra D() are essentially different from the known spectra for bacterial and yeast suspensions. In particular, the points of zero effect lie in the red (but not in the blue) region of spectrum, and the |D()| dependence is a decreasing function in the range 300–800 nm. To explain these results, a theory was developed based on the three-dimensional lattice model of cluster-cluster aggregation and the optical model of interacting dipoles. This theory confirms main conclusions obtained previously in the Rayleigh–Debye–Hans approximation (Khlebtsov, N.G. and Mel'nikov, A.G., Kolloidn. Zh., 1998, vol. 60, no. 6, p. 843) and agrees with experimental D() spectra. It was shown experimentally and theoretically that the structural anisotropy of aggregates exhibited scale invariance, and the differential spectra for the aggregates with various numbers of particles are described by a single universal curve D(kR _g), where k= 2/ and R _gis the mean radius of gyration of aggregates.     

Synthese von Metallkomplexen des Tetra-(2,3-anthra)-tetraazaporphins und Vergleich ihrer Elektronenabsorptionsspektren mit denen anderer anellierter Tetraazaporphinsysteme

Copper, nickel and aluminium derivatives of tetra-2,3-anthratetraazaporphin bearing different substituents in the anthracen part have been prepared. The absorption spectra of these substances in different solvents are given and compared with metal complexes of other linearly annellated tetraazaporphins. In the series of vanadyl complexes of tetraazaporphin (_max 597 nm), tetra-[1,2-(4-tert-butyl)-benzo]-tetraazaporphin (_max 698 nm), tetra-[2,3-(6-tert-butyl)-naphtho]-tetraazaporphin (_max 807 nm), tetra-2,3-(anthra)-tetraazaporphin (_max 932 nm), tetra-2,3-(tetraceno)-tetraazaporphin (_max 1055 nm), the absorption maxima of the Q-band are shifted per annellated benzene ring about 100 nm to longer wave lengths.

     

Selective determination of copper with pyridoin phenylhydrazone as chromogenic extraction reagent

Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex ( _max=450 nm,=2.1×10⁴l· mole^–1·cm^–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol ( _max=440 nm,=2.0×10⁴l·mole^–1·cm^–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.

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Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( _max=450 nm,=2,1×10⁴l·mol^–1·cm^–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( _max=440 nm,=2,0×10⁴l·mol^–1·cm^–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.

     

Pressure and temperature effects on the excess deuteron and proton conductance

The limiting molar conductances ° of deuterium chloride DCl in D₂O were determined as a function of pressure and temperature in order to examine the proton-jump mechanism in detail. The excess deuteron conductances °_E(D ⁺), as estimated by the equation [°_E(D ⁺) = °(DCl/D ₂ O) – °(KCl/D ₂ O)], increases with an increase in the pressure and temperature as well as the excess proton conductance [°_E(H ⁺) = °(HCl/H ₂ O) – °(KCl/H ₂ O)]. The isotope effect on the excess conductances, however, depends on the pressure and temperature contrary to the model proposed by Conway et al.: °_E(H ⁺)/°_E(D ⁺) decreases with increasing pressure and temperature. The magnitude of the decrease with pressure becomes more prominent at lower temperature. These results are discussed in terms of the pre-rotation of adjacent water molecules, the bending of hydrogen bonds with pressure, and the difference in strength of hydrogen bonds between D₂O and H₂O.     

Anisotropie der WÄrmeleitung in gedehnten Elastomeren

Zusammenfassung An einigen schwach vernetzten, gedehnten Elastomeren und an gedehntem Weich-PVC wurde die WÄrmeleitfÄhigkeit senkrecht zur Dehnungsrichtung in AbhÄngigkeit von der Temperatur zwischen –10 C und +45 C gemessen. Die Dehnung blieb wÄhrend einer Messung konstant. ist kleiner als die WÄrmeleitfÄhigkeit der ungedehnten (isotropen) Substanz und nimmt mit steigender Dehnung ab. Die Anisotropie der WÄrmeleitfÄhigkeit zeigt sich besonders deutlich ( / ₀0,8 bis 0,9 für=200%) — gleiche Dehnung vorausgesetzt — bei Polymeren, deren Kettenmolekeln polare Seitengruppen enthalten (z. B. Butadien — Acryl-nitril — Copolymer, Polychloropren, chlorsulfoniertes PolyÄthylen), wÄhrend sie bei solchen, deren Molekelketten nur unpolare Seitengruppen enthalten (z. B. Naturkautschuk, Polyisobutylen), kaum in Ersoheinung tritt. Bei Weich-PVC sinkt die Anisotropie bei gleicher Dehnung mit dem Weichmachergehalt und verschwindet fast ganz bei Weichmacherkonzentrationen über 60 Gew.%, d.h. der Quotient / ₀ geht gegen 1, und zwar um so schneller, je grö\er die Wirksamkeit des Weichmachers ist. Eine ZeitabhÄngigkeit der Anisotropie konnte nicht beobachtet werden.

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Summary Thermal conductivity of some crosslinked strained elastomers and plasticized polyvinylchloride was measured normal to the direction of strain as function of temperature between –10 C and +45 C. The strain was held constant during one measurement. is smaller than the thermal conductivity of the unstrained (isotropic) material and decreases with increasing strain. The anisotropy of thermal conductivity appears specially clear ( / ₀ about 0,8 to 0,9 for=200%) — the same strain presumed — with polymers the chain molecules of which contain polar sidegroups (e. g. butadiene — acrylonitrile — copolymer, polychloroprene, chlorsulfonated polyethylene), whereas it can hardly be observed with polymers the chain molecules of which contain only non-polar sidegroups (e. g. natural rubber, polyisobutylene). Concerning strained plasticized Polyvinylchloride the anisotropy decreases at constant strain with the content of plasticizer and nearly vanishes at weight fractions above 60% plasticizer, that means, the quotient / ₀ will become 1. The decrease is the more rapid the greater the plasticizing effectiveness is. A time dependence of the anisotropy has not been observed.

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Herrn Prof. Dr.K.-H. Hellwege und Herrn Dr.W. Knappe danke ich für eingehende Diskussion und Förderung dieser Arbeit.     

Photometrische Bestimmung von Zirkoniumoxidchlorid in Speisesalz

Zusammenfassung 2-Chinolylfluoron bildet mit Zirkonium einen 14-Komplex, dessen Extinktionskoeffizient bei 539 nm _max=165000 ist. Das Bestimmungsverfahren für ZrOCl₂ in Speisesalz wird auf dieser Farbreaktion aufgebaut.

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Photometric determination of ZrOCl₂ in table salt

2-Quinolylfluorone forms a 14-complex with zirconium. Owing to its high extinction coefficient _max=165000 at =539 nm the complex can be used for the determination of ZrOCl₂ in table salt.

     

Exciton Chirality. (A) Origins of and (B) Applications from Strongly Fluorescent Dipyrrinone Chromophores

Summary. (A) The origin of exciton interaction and examples of its application to organic stereochemistry are presented. (B) N,N-Carbonyl-bridged dipyrrinones constitute a new class of highly fluorescent chromophores suitable for investigations of stereochemistry and absolute configuration. N,N-Carbonylxanthobilirubic acid esters are strongly fluorescent, with a fluorescence quantum yield (_F) 0.8, but produce only weak exciton CD from the trans-1,2-cyclohexanediol template. The ester of an analog with benzoic acid replacing propionic, N,N-carbonyl-8-(4-carboxyphenyl)-3-ethyl-2,7,9-trimethyl-(10H)-dipyrrin-1-one, exhibits strong fluorescence (_F=0.68, _em=493nm, _ex=422nm in CHCl₃) and UV-Vis absorption (21000 at 424nm) in organic solvents. Its diester with (1S,2S)-cyclohexanediol is fluorescent and exhibits exciton circular dichroism (=+15dm³·mol^–1·cm^–1, =432nm; =–4dm³·mol^–1cm^–1, =380nm) that correlates with the Exciton Chirality Rule.     

Unicyclic Graphs with Minimal Energy

If G is a graph and ₁,₂,..., _n are its eigenvalues, then the energy of G is defined as E(G)=|₁|+|₂|++| _n |. Let S _n ³ be the graph obtained from the star graph with n vertices by adding an edge. In this paper we prove that S _n ³ is the unique minimal energy graph among all unicyclic graphs with n vertices (n6).     

Determination of boron with chromotropic acid by first-derivative synchronous spectrofluorimetry

Summary A method for the determination of traces of boron by first-derivative synchronous spectrofluorimetry is proposed. It is based on the formation of a fluorescent complex with chromotropic acid at pH 6.7. The constant wavelength difference chosen to optimize the determination is =_em–_ex=24 nm. The range of application is between 2.0 and 20.0 /l of boron, the detection limit 0.4 g/l and the relative standard deviation 3.2%. A study was made of the influence of several ions as potential interferents. The method has been satisfactorily applied to the determination of boron in plants, fertilizers and natural waters.     

Fluorimetric determination of 1-naphthol and mixtures of carbaryl and 1-naphthol in micellar media

Summary The interaction of 1-naphthol with different types of anionic, cationic and non-ionic surfactants has been studied spectrofluorimetrically in order to obtain a sensitivity enhancement in the determination of this compound. At neutral pH, cetyl trimethyl ammonium bromide (CTAB) provides a 2-fold sensitivity enhancement of 1-naphthol and exhibits a weak interaction with carbaryl. In strong alkaline medium carbaryl is hydrolyzed to 1-naphthol and in the presence of CTAB micells, a 5-fold sensitivity enhancement and a limit of detection of 0.2 g·ml^–1 with a 101±3% percentage of recovery is obtained. These facts permit the development of an accurate method for the fluorimetric analysis of 1-naphthol and carbaryl mixtures, comprising the determination of the sum of both compounds (pH 12, 0.1% w/v CTAB, _em=449 nm, _ex=341 nm) and of the concentration of 1-naphthol (neutral pH, 0.4% w/v CTAB, _em=449 nm, _ex=312 nm).     

Influence of o-benzoquinone nature on initiation of radical polymerization by the o-benzoquinone—tert-amine system

o-Benzoquinones initiate radical polymerization of methacrylates under visible light irradiation in the presence of tertiary amines. Spectral sensitivity of the initiating system coincides with absorption bands of o-benzoquinone attributed to the S(*) (_max 400 nm) and S(n*) (_max 600 nm) transitions. The amine radicals (Am^·) initiating polymerization are generated by the photoreduction of Q in the presence of AmH from the triplet radical pair ³(QH^·, Am^·). The yield of Am^· depends on the difference between the volumes of substituents in the 3 and 6 positions of the quinoid ring and is maximal for symmetrically substituted o-benzoquinones. For a series of derivatives of symmetrical 3,6-di-tert-butyl-o-benzoquinone, the rate of photopolymerization of ,-bis(methacryloyloxyethyleneoxycarbonyloxy)ethyleneoxyethylene (OCM-2) in the presence of N,N-dimethylaniline is determined by the free energy (G _e) of electron transfer from the amine to photoexcited o-benzoquinone. The G _e value includes the energies of oxidation of the amines and reduction of the o-quinones and the energy of the 00 transition of the triplet excited state of o-benzoquinones, which are equal to their redox potentials. The photopolymerization rate is maximal for G _e 0.     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Ein Ger?t zur h?chstempfindlichen Differentialspektrophotometrie mit dem Rapidspektroskop

Zusammenfassung Eine Methode zur Differentialspektrophotometrie durch Modulation eines Monochromators wird beschrieben. Der Monochromator oscilliert mit variabler Bandbreite zwischen ₁ und ( ₁+). Wenn ( ₁+) die Wellenlänge des Absorptionsmaximums ist, erscheint am Photo multiplierausgang einer Sinuswelle, deren Amplitude der Extinktions differenz zwischen ¹ und ( ₁+) proportional ist. Die Schaltung zur ultralinearen Messung dieser Amplitude ist angegeben und ihre Anwendung mit dem Zweistrahlphotometer Rapidspektroskop gezeigt. Die Empfindlichkeit wird durch die Kombination um den Faktor 10 bis 100 gesteigert. Der Rauschpegel ist bei der Monochromator-Modulationstechnik etwa 10^–4 E.Das Differentialspektrum stellt die erste Ableitung eines Spektrums dar und gestattet die genauere Lokalisation von Schultern in steilen Flanken eines Spektrums. Die Kombination der beschriebenen Methode mit der Technik des Rapidspektroskops erlaubt es, dasselbe mit gleichem Erfolg wie ein Dual-Wavelength-Gerät einzusetzen.

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Summary A method for differential spectrophotometry by modulation of a single monochromator is described. A single monochromator oscillates with variable bandwidth between ₁ and ( ₁+ ). If ( ₁ + ) is the wavelength at maximal optical density, the photomultiplier output gives a sinus-wave, the amplitude of which is proportional to the optical density difference between ₁ and ( ₁+). The circuit for ultralinear measurement of this amplitude is described and details of its application with the split-beam spectrophotometer Rapidspektroskop are given. The sensitivity of the entire assembly is increased by a factor of between ten and one hundred. The noise level of the monochromator-modulated technique is about 10^–4 optical density units. The differential spectrum represents the first derivative of a spectrum and allows one to determine more exactly the location of shoulders in the slope of a spectrum.The combination of the described method with the techniques of the Rapid spektroskop thus provides facilities which equal those of a dual-wavelength apparatus.

     

Fluordiazadiphosphetidine, 24. Mitt.: Reaktion monosubstituierter Fluordiazadiphosphetidine mit Kaliumfluorid/Kronenether

Summary The reactivity of some monosubstituted fluorodiazadiphosphetidines towards potassium fluoride utilizing 18-crown-6-ether as a phase transfer catalyst has been studied. The following compounds were investigated: 2,2,2,4,4-pentafluoro-4-methoxy-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine, 2,2,2,4,4-pentafluoro-4-methylamino-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine, 2,2,2,4,4-pentafluoro-4-methylthio-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine, and a 1:1 mixture of 2,2,2,4,4-pentafluoro-4-(N²,N²-dimentyl-hydrazino)-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine and 2,2,2,4,4-pentafluoro-4-methylamino-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine. All reactions proceeded in a similar way and led to the disubstituted derivates of the starting materials and the potassium salt K₂(CH₃NPF₄)₂. In this way 2,2,4,4-tetrafluoro-2-methylamino-4-(N²,N²-dimethylhydrazino)-1,3-dimethyl-1,3,2⁵,4⁵-diazadiphosphetidine has been synthesized for the first time and a new way has been found for the synthesis of several compounds reported in literature.

Verstorben     

Spectrophotometric determination of clozapine in pharmaceuticals

New Spectrophotometric methods for the assay of clozapine (CZP) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CZP with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ceric ammonium sulphate to form a coloured species (_max 570 nm). Method B is also based on the oxidative coupling reaction of CZP withP-,N,N-dimethylpheny-lenediamine dihydrochloride (DMPD) in the presence of sodium hypochlorite to form a coloured species (_max 690 nm). Method C is based on the formation of coloured charge-transfer complex between CZP and chloranilic acid (_max 540 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2–25, 10–120 and 15–300 g/ml for methods A, B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CZP and the relative standard deviation values were within 1.0%.     

Spectrophotometric methods for the determination of labetalol hydrochloride in pure and dosage forms

Simple and sensitive Spectrophotometric methods for the determination of labetalol hydrochloride are described. The first two are based on the oxidative coupling reaction of labetalol hydrochloride withp-N,N-dimethyl-phenylenediamine dihydrochloride (method A, _max 685 nm) and 3-methyl-2-benzothiazolinone hydrazone hydrochloride (method B, _max 545 nm) in the presence of sodium hypochlorite and eerie ammonium sulphate as oxidants, respectively. The third depends on the formation of an ion-association complex of labetalol hydrochloride with suprachen violet 3B at pH 1.3, which is extracted into chloroform (method C, _max 565 nm). The methods obey Beer's law and the precision and accuracy of the methods were checked against the B.P. reference method and the relative standard deviations were in the range 0.35–0.52%. These methods are applied to the determination of labetalol in dosage forms.     

Four spectrophotometric methods for determination of nitrofurazone in pharmaceutical formulations

Four simple and sensitive visible spectrophotometric methods (A-D) for the determination of nitrofurazone in bulk samples and pharmaceutical formulations are described. They are based on the formation of colored species by treating either its reduction product with 3-methylbenzothiazolin-2-one hydrazone in the presence of ferric chloride (method A: _max 600 nm) or its hydrolysis product with thiobarbituric acid (method B: _max 520 nm, 440 nm) or barbituric acid (method C: _max 400 nm) or by oxidizing it with excess N-bromosuccinimide and determining the consumed NBS using metol-isonicotinic acid hydrazide (method D: _max 620 nm).