Separation of phthalates by cyclodextrin modified micellar electrokinetic chromatography: Quantitation in perfumes

A new CE method has been developed for the simultaneous separation of a group of parent phthalates. Due to the neutral character of these compounds, the addition of several bile salts as surfactants (sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STDC), sodium taurocholate (STC)) to the separation buffer was explored showing the high potential of SDC as pseudostationary phase. However, the resolution of all the phthalates was not achieved when employing only this bile salt as additive, being necessary the addition of neutral cyclodextrins (CD) and organic modifiers to the separation media. The optimized cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method consisted of the employ of a background electrolyte (BGE) containing 25 mM β-CD-100 mM SDC in a 100 mM borate buffer (pH 8.5) with a 10% (v/v) of acetonitrile, employing a voltage of 30 kV and a temperature of 25 °C. This separation medium enabled the total resolution of eight compounds and the partial resolution of two of the analytes, di-n-octyl phthalate (DNOP) and diethyl hexyl phthalate (DEHP) (Rs ~ 0.8), in only 12 min. The analytical characteristics of the developed method were studied showing their suitability for the determination of these compounds in commercial perfumes. In all the analyzed perfumes the most common phthalate was diethyl phthalate (DEP) that appeared in ten of the fifteen analyzed products. Also dimethyl phthalate (DMP), diallyl phthalate (DAP), dicyclohexyl phthalate (DCP), and di-n-pentyl phthalate (DNPP) were found in some of the analyzed samples.     

The role of Fe(II) in the increased medicinal potency of curcumin analyzed by electrochemical methods

The formation of complexes of curcumin and Fe(II) was studied in aqueous media at pH 5.7 ± 0.1 by polarography, amperometry and spectrophotometry. The polarogram indicated formation of complexes between curcumin and Fe(II). Curcumin produces a well-defined direct current polarogram and differential pulse polarogram in 0.1 M ammonium tartrate (supporting electrolyte) at pH 5.7 ± 0.1. The stoichiometry of the Fe(II)-curcumin complex is 1 : 1. Anticancer studies on the drug and its metal complex have been performed against sarcoma cells (in-vitro), revealing the complex to be more potent in anticancer activity compared to the parent drug.     

Determination of acipimox in capsules by differential pulse polarography

A differential pulse polarographic (DPP) method has been developed for the determination of acipimox in its pharmaceutical formulations. Using Sörensen buffer pH 6.0 as supporting electrolyte a single, irreversible peak occurred at –0.79 V vs an Ag/AgCl reference electrode. The peak height vs concentration plot was found to be linear over the range of 10^–6 to 6 × 10^–4 mol/l. The detection limit is 60ng/ml. The analysis of a series of 10 Olbetam® 250 mg capsules showed an overall standard deviation of ± 4.18 mg and a S_rel of ± 1.66%, respectively.     

吡咯并吡咯二酮与低聚噻吩共聚物电荷传输性质的理论研究

利用密度泛函理论对吡咯并吡咯二酮(DPP)与噻吩形成共聚物的低聚物(PDPP-n T)m的电子结构及二体堆积模型的电荷传输性质进行计算.结果表明,随着聚合物单元内DPP浓度增加,噻吩数减少,聚合物分子的HOMO和LUMO能级同时降低,并且HOMO-LUMO带隙变小;链内相邻DPP单元的电子波函数有效重叠增大,显著改善了链内的电子传输能力;同时分子主链的刚性增强,使分子链间LUMO轨道重叠增强,电子转移积分增大;最终体系由p型向双极性材料转化.     

Singular optimal controls of stochastic recursive systems and Hamilton–Jacobi–Bellman inequality

In this paper, we study the optimal singular controls for stochastic recursive systems, in which the control has two components: the regular control, and the singular control. Under certain assumptions, we establish the dynamic programming principle for this kind of optimal singular controls problem, and prove that the value function is a unique viscosity solution of the corresponding Hamilton–Jacobi–Bellman inequality, in a given class of bounded and continuous functions. At last, an example is given for illustration.     

Determination of nisoldipine in film tablets by differential pulse polarography

Summary A differential pulse polarographic (DPP) method was developed for the determination of nisoldipine in Baymycard^® film tablets without interference from excipients. Nisoldipine is reduced at the dropping mercury electrode in a single, irreversible peak. Linearity between the nisoldipine concentration and the peak height was observed in the 5·10^–4–10^–7 M concentration range. The detection limit is 22 ng/ml. The analysis of a series of 10 Baymycard^® 5 mg film tablets showed a standard deviation of ±0.115 mg and aS _rel of ±2.30%, respectively.

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Gehaltsbestimmung von Nisoldipin in Filmtabletten mittels differentieller Pulspolarographie

Zusammenfassung Eine Bestimmung von Nisoldipin in Baymycard^® Filmtabletten mittels differentieller Pulspolarographie (DPP) wurde entwickelt, die keine Störungen durch Tablettenhilfsstoffe aufweist. Nisoldipin wird an der tropfenden Quecksilberelektrode in einem einzigen, irreversiblen Peak reduziert. Linearität zwischen Nisoldipinkonzentration und Peakhöhe wurde im Konzentrationsbereich von 5·10^–4–10^–7 M festgestellt. Die Bestimmungsgrenze beträgt 22 ng/ml. Die Analyse einer Serie von 10 Baymycard^® 5 mg Filmtabletten ergab eine Standardabweichung von ±0.115 mg, dies entspricht einerS _rel von ±2.30%.

     

A POLAROGRAPHIC CATHODIC WAVE OF VITAMIN C

The cathodic wave of vitamin C has not been reported in the literature so far.Its E_(1/2)wasfound at-1.85 volt vs.Ag/AgCl(25℃)in the base solution of 0.1mol/L Bu_4NI.Variouselectrochemical and spectral techniques were used for studying the electrode reaction.They all showed that the electrode reaction was quasi-reversible while C was more than1.0×10~(-6)mol/L and mainly adsorptive while C was less than 1.0×10~(-6)mol/L at a mercuryelectrode.The electron transfer number was 2 and the electron transfer coefficient 0.57.Using DPP techniques,the linear response range was 5.0×10~(-7)-2.0×10~(-3)mol/L and thedetection limit 1×10~(-7)mol/L.     

Synthese und polarographisches Verhalten von 2H-Isoindol-4,7-dionen

Summary 2-Phenylthio-1,4-benzoquinone (1 a) reacts with azomethine ylide AY-A to give 2-methyl-5-phenylthio-2H-isoindole-4,7-dione (4 f). With 2-(N-methylanilino)-5-methyl-1,4-benzoquinone (1 b), the azomethine ylide AY-B undergoes cycloaddition to yield an inseparable mixture of 5a-methyl-8-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydro-pyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bI) and 9a-methyl-7-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydropyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bII). The structures of5 bI and5 bII were established on basis of two-dimensional-NMR-techniques. The mechanism of the cycloaddition of azomethine ylides to 1,4-quinones was studied on basis of cyclovoltammetric investigations. To determine the electron affinity of the isoindoledione derivatives4 a–f and5 a–b the peak potentials were measured by differential pulse polarography (DPP).

     

Polarographic Behavior of Human Plasma Thrombin and Changes in Its Anticoagulation Activity Through Various Conformations

Thrombin plays a pivotal role in the regulation of blood fluidity and therefore constitutes a primary target in the treatment of various hemostatic disorders. For this differential pulse polarography has been developed in an appropriate supporting electrolyte, which produced well‐defined DPP peaks. The average prothrombin time (PT) in citrated plasma samples was determined, which indicated decrease of average PT with rise of thrombin and albumin concentrations, while PT resulted differently (increase) with heparin, thus confirming their role in anticoagulation activity. The PT of thrombin‐heparin and thrombin‐albumin conformations showed sharp increased and steady decreased respectively. Thus, two opposite actions of thrombin, coagulation (thrombin‐albumin) and anticoagulation (thrombin‐heparin) may prove fruitful in clinical approach for thrombotic disorders.     

Conjugated Microporous Networks on the Basis of 2,3,5,6‐Tetraarylated Diketopyrrolo[3,4‐c]pyrrole

π‐Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4‐c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave‐assisted Yamamoto or Sonogashira cross‐coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m² · g⁻¹.