Spectrofluorimetric flow-injection determination of tertiary amines in non-aqueous media

The cyclic condensation of malonic acid with acetic anhydride in non-aqueous media is catalyzed selectively by tertiary amines. This derivatization reaction is adapted for flow injection analysis. A reaction pathway for the cyclization of a mixed anhydride condensate to form a fluorescent fully acylated phloroglucinol carboxylic acid is proposed. The effects of reaction parameters on the sensitivity of the reactionare described and calibration data are presented for ?2.7 mM triethylamine, tripentylamine, N,N-diethylaniline and pyridine. A secondary amine (diethylamine) gave a negligible response, but both primary and secondary amines partially quenched the fluorescence induced by a tertiary amine.     

On the theory of polarographic maxima

The theory of polarographic maxima is presented taking into account the interaction of momentum transport, the electrostatic potential field, the adsorption—desorption and the faradaic processes. Several earlier results are generalised. The systems approach employed here is also extended to quasi-linear situations.     

The polarographic reduction of 5H-benzo[a]phenothiazin-5-ones in non-aqueous media

The polarographic behavior of 5H-benzo[a]phenothiazin-5-one and its ring-substituted derivatives at a dropping mercury electrode was studied in N,N-dimethylformamide (DMF). Each compound gave well-defined two reduction waves, the half-wave potentials of which linearly correlated with theHammett substituent constant _p . For the parent compound, 5H-benzo[a]phenothiazin-5-one, the polarographic behavior was also investigated in selected other solvents. From the similarity with the behavior of anthraquinone, the results obtained in a mixed solvent,DMF—methylcellosolve, were explained by assuming a disproportionation reaction between the parent compound and its dianion.

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Die polarographische Reduktion von 5H-Benzo[a]phenothiazin-5-onen in nichtwäßrigen Medien

Zusammenfassung Es wurde das polarographische Verhalten von 5H-Benzo[a]phenothiazin-5-on und dessen ringsubstituierten Derivaten an der tropfenden Quecksilberelektrode in N,N-Dimethylformamid (DMF) untersucht. Alle Verbindungen gaben zwei wohldefinierte Reduktionswellen, deren Halbwellenpotentiale mit denHammett'schen Substituentenkonstanten _p eine gute lineare Korrelation ergaben. Bezüglich der Stammsubstanz, 5H-Benzo[a]phenothiazin-5-on, wurde das polarographische Verhalten auch in einigen anderen Lösungsmitteln untersucht. Aus Parallelen mit dem Verhalten von Anthrachinon wurden die Ergebnisse, die inDMF—Methylcellosolv als gemischtem Lösungsmittel erhalten wurden, unter der Annahme einer Disproportionierungs-Reaktion zwischen der Stammverbindung und dessen Dianion erklärt.

     

Cerimetry in non-aqueous media

Summary It was found that ceric oxalate is an intermediate product in the oxidation of oxalic acid by ammonium hexanitrato cerate in solvents such as acetonitrile, and a mixture of acetonitrile and glacial acetic acid. Conditions for the formation of ceric oxalate and its decomposition into carbon dioxide and cerous oxalate have been studied. An analytical method for the estimation of oxalic acid in non-aqueous media has been evolved based on this reaction.

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Zusammenfassung Es wurde festgestellt, daß bei der Oxydation von Oxalsäure mit Ammoniumhexanitratocerat(IV) in Acetonitril oder einem Gemisch von Acetonitril und Essigsäure Cer(IV)-oxalat als Zwischenprodukt auftritt. Die Bedingungen für die Bildung von Cer(IV)-oxalat und seine Zersetzung zu CO₂ und Cer(III)-oxalat wurden untersucht. Ein Verfahren zur Oxalsäurebestimmung in nichtwäßrigem Medium wurde ausgearbeitet.

     

Electrostatic stabilization in non-aqueous media

This paper discusses electrostatic stabilization of dispersions in non-aqueous media. It begins with the theory of repulsion, with particular attention to the roles of the dielectric constant and ionic strength of the liquid medium. Results for flat plates and spheres are compared. Methods are reviewed to measure the dielectric and electric parameters in non-aqueous media, in conjunction with procedures to determine the mechanical properties of electrostatically stabilized, concentrated suspensions.From theoretical considerations it appears that the extent of the electrostatic stabilization in non-aqueous media is extremely sensitive to the dielectric constant ϵ of the liquid, affecting stability in particular through the degree of dissociation of the stabilizing electrolyte. It is essential that, besides the presence of charge on the particles, there also are certain levels of ions in the solution to ensure a sufficient force of repulsion. It is expedient to distinguish three regimes of ϵ: (a) ϵ ⩾ 11, the (semi-)polar range, where systems can be charge-stabilized more or less as in aqueous systems, (b) the low-polar regime (5 ⩽ ϵ ⩽ 11), where electrostatic stabilization is possible provided some dissociated electrolyte is present and (c) the apolar range (ϵ⩽ 5), where screening is exclusively determined by the polarization of the solvent, and where electrostatic stabilization may be more problematic.Concentrated dispersions of solids in liquid nonionic carriers with dodecyl-benzene sulphonic acid (HDBS) as the stabilizer arc good models for the ‘low polar’ category, as detailed experimental data illustrate. In such media HDBS creates a ζ-potential, and enhances the dielectric constant and the ionic strength of the continuous phase. Especially when attraction between suspended salt particles in liquid nonionics is weak, electrostatic stabilization is easily achieved. This is particularly noticed in the rheology of the concentrated suspensions of some salts.     

Generation of bismuthane in non-aqueous media

The generation of BiH₃ in non-aqueous media in an MHS-10 Perkin-Elmer hydride generator is studied. Optimal conditions for generation of BiH₃ inN,N-dimethylformamide, dimethylsulfoxide and formamide (concentration of NaBH₄, acidic medium, optimum volume, characteristic concentration and detection limit) are studied. The results obtained are compared with those corresponding to hydride generation in aqueous medium.     

Filamentous bacteriophage stability in non-aqueous media.

BACKGROUND: Filamentous bacteriophage are used as general cloning vectors as well as phage display vectors in order to study ligand-receptor interactions. Exposure to biphasic chloroform-water interface leads to specific contraction of phage, to non-infective I- or S-forms. RESULTS: Upon exposure, phage were inactivated (non-infective) at methanol, ethanol and 1-propanol concentrations inversely dependent upon alcohol hydrophobicity. Infectivity loss of phage at certain concentrations of 1-propanol or ethanol coincided with changes in the spectral properties of the f1 virion in ultraviolet fluorescence and circular dichroism studies. CONCLUSIONS: The alcohols inactivate filamentous phage by a general mechanism--solvation of coat protein--thereby disrupting the capsid in a manner quite different from the previously reported I- and S-forms. The infectivity retention of phagemid pG8H6 in 99% acetonitrile and the relatively high general solvent resistance of the phage strains studied here open up the possibility of employing phage display in non-aqueous media.     

Oxidation of aromatic amines with chromyl chloride-I : Oxidation of aromatic primary amines

The oxidation of aromatic primary amines with chromyl chloride in carbon tetrachloride or chloroform, results in the formation of intermediate solid adducts (Etard adducts) which, on hydrolysis, give azobenzenes(1), 1,4-benzoquinones(2),anilino-1,4-benzoquinones(3), 1,4-benzoquinone anils(4)and anilino-1,4-benzoquinone anils (5) in yields which depend on the position, nature and degree of substitution of the ring.     

Macrocyclic lactones via biocatalysis in non-aqueous media

The enantiospecificity of lipase-catalyzed lactonization of chiral (w-1)-hydroxy acids to form diolides in non-aqueous medium was investigated.     

Titrations of some steroidal bases in non-aqueous media

Summary The potentiometric and catalytic thermometric titrations of some newly synthetised steroidal compounds containing the pyridine nucleus are performed with 0. 1 M perchloric acid in acetic acid. Amounts of 15.32–37.71 mg were determined with a relative standard deviation < 0.89 %. Results of separate determinations of the bases by catalytic thermometric and potentiometric titration are in good agreement.By means of the data of potentiometric titrations, pK-values of the investigated compounds were estimated and some possible explanations are provided for the noticeable differences in the two pairs of geometrical isomers. The obtained results show that these compounds behave as relatively stronger bases (pK 6.04–7.03) in acetic acid. It has also been found that the introduction of one vinyl-group into -position of the pyridine nucleus has no essential influence on the basicity, as confirmed by the obtained pK-values.Determination of the isomeric ketones, 3-acetoxy-17-picolinylidene-5-androstene-16-ones, in mixture was successfully performed by potentiometric titration in acetic anhydride only.

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Titrationen einiger Steroidbasen in nichtwäßrigen Medien

Zusammenfassung Potentiometrische und katalytische thermometrische Titrationen wurden für einige neusynthetisierte Androstenverbindungen mit pyridinischem Kern mittels 0,1 M Perchlorsäure in Essigsäure durchgeführt. Mengen von 15,32–37,31 mg wurden mit einer relativen Standardabweichung von <0,89% bestimmt. Die Ergebnisse der katalytischen thermometrischen Titrationen stimmen mit denen der potentiometrischen gut überein.Auf Grund der Daten der potentiometrischen Titrationen wurden die pK-Werte der untersuchten Verbindungen berechnet und mögliche Erklärungen für ihre geometrischen Isomeren gegeben. Die erhaltenen Ergebnisse zeigen, daß diese Verbindungen in Essigsäure starke Basen (pK 6,04–7,03) sind. Ebenso wurde festgestellt, daß die Einführung einer Vynilgruppe in -Stellung des pyridinischen Kerns sehr wenig die Basizität beeinflußt, was die erhaltenen pK-Werte bestätigen.Die Bestimmung von isomeren Ketonen, 3 -Acetoxy-17-picolinyliden-5-adrosten-16-onen, in Mischung wurde erfolgreich durch potentiometrische Titration nur in Essigsäureanhydrid ausgeführt.

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The authors thank the Scientific Fund of SAP Vojvodina for partial financial support of the present work     

Analysis of heterocyclic aromatic amines

Heterocyclic aromatic amines are formed in protein and amino acid-rich foods at temperatures above 150 °C. Of more than twenty heterocyclic aromatic amines identified ten have been shown to have carcinogenic potential. As nutritional hazards, their reliable determination in prepared food, their uptake and elimination in living organisms, including humans, and assessment of associated risks are important food-safety issues. The concentration in foods is normally in the low ng g⁻¹ range, which poses a challenge to the analytical chemist. Because of the complex nature of food matrixes, clean-up and enrichment of the extracts are also complex, usually involving both cation-exchange (propylsulfonic acid silica gel, PRS) and reversed-phase purification. The application of novel solid-phase extraction cartridges with a wettable apolar phase combined with cation-exchange characteristics simplified this process—both the polar and apolar heterocyclic aromatic amines were recovered in one fraction. Copper phthalocyanine trisulfonate bonded to cotton (“blue cotton”) or rayon, and molecular imprinted polymers have also been successfully used for one-step sample clean-up. For analysis of the heterocyclic aromatic amines, liquid chromatography with base-deactivated reversed-phase columns has been used, and, recently, semi-micro and capillary columns have been introduced. The photometric, fluorimetric, or electrochemical detectors used previously have been replaced by mass spectrometers. Increased specificity and sub-ppb sensitivities have been achieved by the use of the selected-reaction-monitoring mode of detection of advanced MS instrumentation, for example the triple quadrupole and Q-TOF instrument combination. Gas chromatography, also with mass-selective detection, has been used for specific applications; the extra derivatization step needed for volatilization has been balanced by the higher chromatographic resolution.     

Flow-injection determination of secondary amines in non-aqueous solution with fluorescence detection

The procedure is based on derivatization with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole to form a fluorescent adduct. Interference from primary amines is overcome by on-line chemical masking with an equimolar mixture (58 mM) of o-phthalaldehyde and 2-mercaptoethanol with a tolerance of 20 mM 1-ethylpropylamine for the determination of dibutylamine (0.3 mM). The r.s.d. for dihexylamine (0.34 mM) is 1.3% (n=5) and the limit of detection (unweighted least-squares method) is 0.06 mM.     

Differential pulse polarographic determination of orthophosphate in aqueous media

The determination of orthophosphate in aqueous media by differential pulse polarography is described. It is based on determination of the molybdenum in 12-phosphomolybdic acid. High sensitivity is achieved by measuring the polarographic wave due to the catalytic reduction of perchlorate or nitrate in the presence of molybdenum(VI). The method is suitable for samples as small as 3.5 ml which contain as little as 9 ng of phosphorus per ml. The average relative deviation is 3.0% at the 0.045 mg/l. phosphorus level and 1.6% at the 1.2 mg/l. level. Results for the analysis of EPA quality-control water and real surface-water samples are reported.