Mechanistic considerations on photoreaction of organic compounds via excitation of contact charge transfer complexes with oxygen

Reactions of various organic compounds induced by excitation of their contact charge transfer (CCT) pairs with oxygen were classified into three types of behaviour on the basis of reaction products. It is proposed that the excited state of the CCT pairs gives the products through the most isoenergetic course along the plausible exothermic pathway.     

Investigation of polar organic solvents compatible with Corona Charged Aerosol Detection and their use for the determination of sugars by hydrophilic interaction liquid chromatography

A range of organic solvents (ethanol, isopropanol and acetone) has been investigated as alternatives to acetonitrile and methanol when used in conjunction with Corona Charged Aerosol Detection (Corona CAD). These solvents have been evaluated with regard to their effect on the response of the Corona CAD. Three dimensional response surfaces were constructed using raw data showing the relationship between detector response, analyte concentration and percentage of organic solvent in the mobile phase, using sucralose or quinine as the test analyte. The detector response was non-linear in terms of analyte concentration for all solvents tested. However, detector response varied in an approximately linear manner with percentage of organic solvent over the range 0–40% for ethanol or isopropanol and 0–80% for acetone and methanol. The chromatographic performance of the various solvents when used as aqueous–organic mobile phases was evaluated for isocratic and gradient separations of sugars and sugar alcohols by hydrophilic interaction liquid chromatography (HILIC) using an Asahipak NH2P-504E column coupled with Corona CAD detection. It was found that whilst acetonitrile provided the highest column efficiencies and lowest detection limits of the solvents studied, acetone also performed well and could be used to resolve the same number of analytes as was possible with acetonitrile. Typical efficiencies and detection limits of 5330 plates m⁻¹ and 1.25 μg mL⁻¹, respectively, were achieved when acetone was used as the organic modifier. Acetone was utilised successfully as an organic modifier in the HILIC separation of carbohydrates in a beer sample and also for a partially digested dextran sample.     

Flow injection—atomic absorption spectrometry with organic solvents

A flow injection technique with an organic solvent carrier stream is recommended for the determination of trace elements by atomic absorption spectrometry. Carrier streams of methyl isobutyl ketone and especially n-butyl acetate are effective in enhancing sensitivity. The proposed method permits about 300 determinations per hour with a relative standard deviation of less than 5%.     

Novel microwell assay with high throughput and minimum consumption for organic solvents in the charge transfer-based spectrophotometric determination of clarithromycin in pharmaceutical formulations

Background

Clarithromycin (CLM) is a semi-synthetic macrolide antibiotic with a broad antibacterial spectrum. It has a potent activity against Myc. Pneumonia, Legionella Spp., H. Influenza, and Mor. Catarrhalis. It is also used for prevention and treatment of disseminated M. Avium infections in patients with AIDS. The therapeutic importance and wide use of CLM promotes the growing interest in developing proper methods for its determination in bulk and pharmaceutical formulations.

Results

The present study describes the development and validation of a novel assay that can increase the throughput and reduce the consumption of organic solvents in the charge transfer (CT)-based spectrophotometric determination of CLM. In this assay, the CT reaction between CLM as n-electron donor and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a π-electron acceptor was performed in the 96-microwells of an assay plate. The color signals of the CT complex were measured at 450 nm by microwell-plate absorbance reader. The linear range of the assay was 20?850 μg mL^?1. The limits of detection and quantitation were 15.5 and 51.2 μg mL^?1, respectively. The proposed assay gave very high precisions; the relative standard deviation (RSD) values did not exceed 1.82%.

Conclusions

The assay described herein has a high throughput property that facilitates the processing of large number of samples in a reasonable time. As well, it consumes minimum volumes of organic solvents, thus it significantly reduces the exposures of the analysts to the toxic effects of organic solvents, and reduce the analysis cost by 50-folds. The results demonstrated that the proposed assay has great practical value in the routine analysis of CLM in quality control laboratories.

     

Spectrophotometric determination of water in organic solvents with solvatochromic dyes

The correlation between the absorbance at a fixed wave-length of a betaine dye in an organic solvent and the water content of the same solvent has been investigated. The betaine dyes investigated are 2,4,6-triphenyl-N-(3,5-diphenyl-4-hydroxyphenyl)pyiidinium betaine (I), 1-methyl-8-hydroxyquinolinium betaine (II), 1-methyl-6-hydroxyquinolinium betaine (III) and 2-methyl-5-isoquinolinium betaine (IV), and the organic solvents are ethanol, isopropanol, acetone, dioxan, acetonitrile and pyridine. The possibility of determining a trace amount of water in an organic solvent is demonstrated. The sensitivity of the method depends on solvent and dye but for example, 0.06 mg of water in 1 ml of acetonitrile can be detected with III with an ordinary spectrophotometer. The limitations of practical applications are discussed.     

Spectrophotometric determination of water in organic solvents with solvatochromic dyes-II

The correlation between the absorbance of a merocyanine dye in an organic solvent and the water content of the solvent has been investigated. The merocyanine dyes investigated are 1-methyl-4-[(4-oxocyclohexa-2, 5-dienylidene)-ethylidene]-1,4-dihydropyridine (I), 1-methyl-4-[(2-oxocyclohexa-3,5-dienylidene)-ethylidene]-1, 4-dihydropyridine, 1-methyl-2-[(4-oxocyclohexa-2,5-dienylidene)-ethylidene]-1, 2-di-hydropyridine and 1-methyl-2-[(oxocyclohexa-3,5-dienylidene)-ethyl-idene]-1, 2-dihydropyridine, and the organic solvents are isopropanol, acetone, acetonitrile and pyridine. The possibility of determining a trace amount of water in an organic solvent is demonstrated, and a procedure is proposed for the determination of trace water in pyridine. The sensitivity of the method depends on the solvent, being more sensitive in an aprotic solvent than in a protic one ; for example, 0.05 or 0.27 mg of water in 1 ml of acetonitrile or of isopropanol respectively can be detected with I, by use of an ordinary spectrophotometer.     

Absorption spectra of 2-styryl-4-phenyl-thiazole ethiodides in organic solvents of varying polarities and determination of the formation constant of the charge transfer complex formed

The electronic absorption spectra of some 2-styryl-4-phenyl-thiazole ethiodides are studied in organic solvents of different polarities. The shorter wavelength band appearing in the visible region is assigned to an intramolecular charge transfer (CT)-transition originating from the phenyl moiety to the positively charged hetero ring, while the longer wavelength one is due to an intermolecular CT-transition from the iodide ion to the 2-styryl-4-phenyl-thiazolinium cation. These assignments are based on the nature of the aldehydic residue and effects of solvent, concentration, and temperature on both the position and absorptivity of the CT complex-band. It is concluded that the CT complex formed will be highly solvated inDMF, DMSO, ethanol and methanol relative to in CHCl₃, dioxane and acetone. The formation constant of the CT complex in solutions of different polarities is determined at different temperatures. Furthermore, the thermodynamic parameters H ^o, G ^o and S ^o for complex formation are calculated and discussed.

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Absorptionsspektren von 2-Styryl-4-phenyl-thiazol-ethiodiden in verschiedenen Lösungsmitteln und Bestimmung der Bildungskonstanten der Charge-Transfer-Komplexe

Zusammenfassung Die Elektronenanregungsspektren einiger substituierter 2-Styryl-4-phenyl-thiazol-ethiodide wurden in einigen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorption bei kürzerer Wellenlänge wird einem intramolekularen Charge-Transfer (CT)-Übergang zugeordnet, die langwellige Bande einem intermolekularen CT-Übergang (Jodid—organ. Kation). Die Diskussion erfolgt basierend auf Substitutions-, Lösungsmittel-, Konzentrations-, und Temperatur-Effekten. Die Komplexbildungskonstanten und die thermodynamischen Parameter H ^o, G ^o und S ^o werden angegeben.

     

Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.

     

单个离子标准迁移自由能的测定

本文采用活化分析法测定参考解质Ph4AsPh4B晶体在水和有机溶剂中的溶解度和计算了它从水迁移到有机溶剂中的标准迁移Gibbs自由能△^s^wG^0t.根据Ph4AsPh4B假定,求得参考正负离子Ph4As^+和Ph4B^-的标准迁移Gibbs自由能.又通过测定Ph4AsTcO4,CsPh4B,KPh4B和CsTCO4等晶体在水和有机溶剂站的溶解度,求得TcO4^-,K^+,Cs^+等离子的标准迁移自由能,并对结果进行了讨论.     

化妆品中挥发性有机溶剂的通用检测方法

以化妆品配方中常见及禁用的36种有机溶剂为研究模板,建立了化妆品中挥发性有机溶剂残留评价初筛知识库、确证知识库和定量方法。初筛知识库包括双柱保留指数知识库和NIST质谱库。双柱保留指数知识库以保留指数为定性指标,选择极性的VF-1301ms和非极性的DB-5ms两根色谱柱,用顶空气相色谱-质谱法考察了36种有机溶剂在两种色谱分离系统中的保留特性。利用NIST MS search 2.0作为检索工具,同时建立了36种挥发性有机溶剂的顶空气相色谱-质谱定量方法。样品经60 ℃、30 min静态顶空后以连接了VF-1301ms石英毛细管色谱柱的气相色谱-质谱仪检测,外标法定量。方法检出限为0.01~3.3 μg/g,加标回收率为60.77%~126.60%。该方法从通用性的角度,为化妆品中挥发性有机溶剂残留的筛查、鉴别和定量提供方法,部分解决了测定化妆品中挥发性有机溶剂时需要针对不同检测目标建立不同方法以及潜在溶剂存在备选筛查的问题。     

Strain-induced reversal of charge transfer in contact electrification

We have contact! Material strain can have a dominating effect on contact electrification. When a deflated (relaxed) balloon is rubbed against teflon, the teflon surface charges positively, but when the same balloon is inflated (strained), the teflon surface charges negatively. This result illustrates that material strain can control contact electrification and alter the driving force of some (yet unknown) charge-transfer species.     

Photodecomposition and charge transfer complexes of acetylferrocene in binary solvents

Photoreactions of acetylferrocene in equimolar binary solvents: CCl₄ — cyclohexane and C₂Cl₄ — cyclohexane were investigated. Photoproducts were identified and the relations between the quantity of photoproducts, their quantum yield, the amount of decomposed acetylferrocene and exposure time and wavelength were determined. Equilibrium constantsK and molar extinction coefficients _c of the CT complexes formed between acetylferrocene and halogen derivative were determined.

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Photochemische Zersetzung und Charge-Transfer-Komplexe von Acetylferrocen in binären Lösungsmitteln

Zusammenfassung Die Photoreaktionen von Acetylferrocen in binären (äquimolaren) Lösungsmittelgemischen — CCl₄/Cyclohexan und C₂Cl₄/Cyclohexan — wurden untersucht. Die Photoprodukte wurden identifiziert und die Abhängigkeit ihrer Menge, der Quantenausbeute und der Menge des zersetzten Acetylferrocens von der Belichtungszeit und der Wellenlänge bestimmt. Die Gleichgewichtskonstanten und die molaren Extinktionskoeffizienten der Charge-Transfer-Komplexe zwischen Acetylferrocen und den Halogenverbindungen wurden ermittelt.

     

Effect of organic solvents on the reduction of oxygen in water

The effect of solvents on the reduction of oxygen was investigated by pulse voltammetry. The established differences in the effect of the investigated solvents on certain stages of the reduction of oxygen are determined to a significant degree by their concentration in the system. Suggestions about the mechanism of the toxic action of the solvents in biosystems are made. Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev-94. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 1, pp. 11–13, January–February, 1998.     

A microgap impedance sensor for the determination of trace water in organic solvents

A microgap impedance sensor with a 50 μm gap was developed for the determination of trace water in organic solvents by coating poly(dimethyldiallylammonium chloride) (PDMDAAC) and ferricyanide/ferrocyanide composite materials on indium tin oxide (ITO). The electrochemical properties of the composite materials were investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We observed that the impedance response of the sensor depended on the concentration of trace water in the organic solvents. Under optimized conditions, the linear range for the determination of trace water was 0-0.06% for chloroform (CHCl(3)), 0-0.10% for acetone (CH(3)COCH(3)), 0-0.12% for tetrahydrofuran (THF), and 0-0.10% for acetonitrile (CH(3)CN), and the detection limits were 0.65, 1.54, 0.61, and 1.72 ppm, respectively. The results obtained from the impedance sensors were comparable to those obtained using the traditional Karl Fischer method.     

A quantitative determination of organophosphate pesticides in organic solvents

An amperometric acetylcholinesterase (AChE) biosensor based on thiocholine-hexacyanoferrate reaction was developed for the analysis of OPCs in pure organic solvents. The enzyme (AChE) was co-immobilized with an electron mediator, Prussian Blue, on the surface of a graphite electrode. The effect of organic solvents on acetylcholinesterase activity was estimated in the presence of polar (hydrophilic) and non-polar (hydrophobic) organic solvents in the range of 0.01–100%. The ability of the AChE biosensor to detect pesticides was demonstrated by quantitative determination of dichlorvos, fenthion and diazinon in ethanol solvent. The assay allows determination of OPCs in sub-micromolar concentration ranges with an overall assay time of 10 minutes. The sensing elements of the amperometric AChE biosensor can be stored in dry state for more than 2 months. The AChE biosensor possesses distinct advantages, including monitoring of hydrophobic substrates, elimination of microbial contamination, and relative ease of enzyme immobilization. Potential application areas include food analysis and environmental monitoring.     

水溶性电泳漆溶剂中有机成分的气相色谱分析

异丙醇,正丁醇,乙二醇单丁醚均为水溶性电泳漆溶剂中添加的有效成分,其含量的大小影响金属件着漆效果及经济成本,其中乙二醇单丁醚是电泳漆中高沸点溶剂,用作分散剂、湿润剂[1,2]。本文在文献[3,4]的基础上,考察了三种成分的气相色谱分离,确定了测定条件。1　实验部分1 1　仪器与测试条件日本产岛津GC-9A型气相色谱仪带C-R3A型色谱数据处理机。FID为检测器,1 6m×3 2mm玻璃柱,固定相GDX-103(60 80目),气化温度200℃,检测温度250℃,柱温144℃。载气:氮气50ml/min,氢气40ml/min,空气450ml/min。以保留时间定性,采用内标乙二醇单乙醚…     

The determination of the solubility of organic solvents in mineral acids

A knowledge of the solubility of organic solvents in aqueous solutions of mineral acids is shown to be important in solvent extraction studies. The method described depends upon the direct measurement of the amount of solvent thrown out of the aqueous phase on neutralization. The results of experiments on the solubility of iso-propyl ether in aqueous hydrochloric acid are given. The accuracy, limitations, and uses of the method are discussed.     

A new method for the determination of oxygen in organic compounds

Oxygen in compounds of carbon, hydrogen, and oxygen can be determined by heating the sample with an excess of strontium oxide and graphite in. a nickel bomb or sealed Vycor glass tube. During the heating period, three hours at 650° C, the oxygen of the sample is converted to carbonate. The carbonate is then determined volumetrically. The accuracy of the method was found to be ± 0.3% (absolute percentage error) for several types of compounds. Most elements other than carbon, hydrogen, and oxygen interfere. Compounds like phenol, that are exceedingly resistant to complete pyrolysis, yield low resuilts. Carbon in organic compounds can be determined by heating the sample with barium nitrate, and subsequently determining carbonate in the mixture.