Pulsed Corona Discharge-Induced Reactions of Acetophenone in Water

The reactions of acetophenone in water by pulsed corona discharges have been investigated to provide fundamental information concerning the reactions of acetophenone in water. Experimental results indicated that photolysis of acetophenone did not involve a hydroxyl radical mechanism and the majority flux of hydroxyl radicals originated from the dissociation of gas-phase oxygen in the plasma channels. The rate constants for photolysis and pyrolysis were determined to be 1.5×10^–7 M-s^–1, 2.2×10^–4 s^–1, respectively. The rate constant for the oxidative reactions was measured as 1.2×10^–7 M-s^–1. Results from this study support the proposal that acetophenone degradation reaction proceed through the oxidative reaction pathway, where molecular oxygen accelerates acetophenone degradation, photolysis, and pyrolysis pathways.     

Review on gaseous chlorinated organic pollutants electron beam treatment

Literature on chlorinated organic compounds (Cl–HC) treatment in different conditions using EB-irradiation was reviewed and results of the studies are reported, and compared with own results. The differences in degradation efficiency of aliphatic and aromatic Cl–HC compounds were compared. The experiments and the calculations were performed for air, N₂, He and H₂ gas matrices and influence of different additives such as water vapour and NH₃ on the process were studied. The general chemical mechanism of Cl–HC degradation in gas phase under EB-irradiation has been proposed.     

Radiolytic degradation of malathion and lindane in aqueous solutions

Degradation of malathion and lindane pesticides present in an aqueous solution was investigated on a laboratory scale upon gamma-irradiation from a ⁶⁰Co source. The effects of pesticide group, presence of various additives and absorbed dose on efficiency of pesticide degradation were investigated. Gamma-irradiation was carried out in distilled water solutions (malathion and lindane) and in combination with humic solution (HS), nitrous oxide (N₂O) and HS/N₂O (lindane) over the range 0.1–2 kGy (malathion) and 5–30 kGy (lindane). Malathion was easily degraded at low absorbed doses compared to lindane in distilled water solutions. Absorbed doses required to remove 50% and 90% of initial malathion and lindane concentrations in distilled water solutions were 0.53 and 1.77 kGy (malathion) and 17.97 and 28.79 kGy (lindane), respectively. The presence of HS, N₂O and HS/N₂O additives in aqueous solutions, significantly improved the effectiveness of radiolytic degradation of lindane. Chemical analysis of the pesticides and the by-products resulted from the radiolytic degradation were made using a gas chromatography associated with mass spectrometry (GC–MS). Additionally, the final degradation products of irradiation as detected by ion chromatography (IC) were acetic acid and traces of some anions (phosphate and chloride).     

Formation of the main gas compounds during thermal analysis and pyrolysis: Betaine and betaine monohydrate

The thermochemical behaviour of betaine and betaine monohydrate was investigated under two degradation conditions. Betaine was heated up to 700°C at 10°C min^–1 in air and nitrogen flows and the evolved gas was analysed with the combined TG-FTRIR system. The evolved gas from betaine pyrolysis at 350 and 400°C was analysed by gas chromatography using mass-selective detection (Py-GC/MSD). In addition, the electron impact mass spectra of betaine and betaine monohydrate were measured.Esterification is one of the most important pyrolytic processes involving beta- ines. Even glycine betaine can change to dimethylglycine methyl ester via intermolecular transalkylation by heating. Trimethylamine, CO₂, and glycine esters were the main degradation products. Small amounts of ester type compounds evolved both in pyrolysis and with TG-FTIR. The monohydrate lost water between 35 and 260°C while the main decomposition took place at 245-360°C. The residual carbon burnt in air to CO₂ up to a temperature 570°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

Ethanol Conversion in an Aqueous Solution upon Aluminum Valve Anode Microdischarge Treatment

The conversion of 0.1–2.0 M aqueous ethanol solutions in the carbonate electrolyte by treatment with a microdischarge at an anode made of the AMg-6 aluminum–magnesium alloy was studied. It was shown that the microdischarge treatment leads to degradation of ethanol yielding hydrogen, carbon monoxide, ₁–₄ hydrocarbons, methanol, formaldehyde, acetaldehyde, 1,2-propylene glycol, 2,3-butylene glycol, water, and acetic acid. The mechanism of relevant processes is discussed, which suggests a multiplicity of ethanol degradation pathways in vapor–gas bubbles.     

The effect of humidity on the degradation of Nafion membrane

Controlling the activity of water in the reactant streams is critical both to the design of fuel–cell systems and to the useable life of membrane separators. In this study, fuel–cell durability tests were conducted under different levels of relative humidity. The emission rates of various degradation products such as HF, SO₄²⁻ and TFA (trifluoroacetic acid) were determined as a function of water activity. The degradation of the membrane was accelerated as the level of water activity is reduced. The membranes become less conductive, more brittle and rigid after fuel–cell testing. ATR-FTIR investigations showed that the decomposition of the ether group in the middle of side chain corresponds well with the detection of a TFA product. Thermogravimetric analysis also showed a decrease in thermal stability after testing at lower humidity. Formation of cracks was observed in membranes degraded under conditions of low humidity. A model of membrane degradation based on the main chain unzipping process indicates that the mechanism changes with water activity. Finally, the representative reaction pathways in each degradation scheme were postulated.     

Determination of cadmium and lead in river water by sequential metal vapor elution analysis using a step-heated column

Determination of cadmium and lead in river water by sequential metal vapor elution analysis (SMVEA, column temperature; >1210 K) with argon carrier gas and an atomic absorption detector (AA) is reported. The column was a molybdenum tube inserted a tungsten coil. The flow rate of carrier gas was 1.8 ml min^–1. Cadmium and lead were separated from Ca, Fe, K, Na, and Zn metal vapours by SMVEA with the step-heated column (1210–1520 K) at an atomization temperature of 1830 K. Under the optimal experimental conditions, the recoveries of spiked-cadmium and lead in river waters were in the range of 91 to 106%. It is to determine cadmium and lead in river water without the interferences by matrix elements observed by electrothermal AAS, after only the addition of hydrochloric acid to the sample.     

A rapid and sensitive GC–MS method for determination of 1,3-dichloro-2-propanol in water

A rapid analytical method for sensitive determination of 1,3-dichloro-2-propanol (1,3-DCP) in river water has been developed. 1,3-DCP is extracted from water with ethyl acetate. After filtration through sodium sulfate the ethyl acetate phase is analyzed by gas chromatography–mass spectrometry. The method uses 1,3-DCP-d₅ as internal standard. Different extraction solvents, concentrations of ammonium sulfate in the water samples, and the effect of humic acid were tested and their influence on the recovery of DCP has been evaluated. The method quantification limit was 0.1 g L^–1. For spiked water samples (0–5.2 g L^–1, n=21) a repeatability coefficient of variation of 5.4% was obtained. The average recovery rate of 1,3-DCP was 105±3% (n=21). Stability tests, which were carried out with Danube river water, led to an estimated 1,3-DCP degradation rate of 0.008±0.0008 day^–1 at 6°C.     

Determination of methylmercury fluxes across the air–water and air–soil interfaces by gas chromatography with electron capture detection

A method for the determination of methylmercury (MeHg) fluxes across the air–water and air–soil interfaces was developed using an in situ chamber. The MeHg in the air coming out of the chamber was captured by a column containing sulfhydryl cotton fiber adsorbent. MeHg was then desorbed from the column by using 2 mol L^–1 HCl. The MeHg in the effluent was extracted with benzene, and determined by gas chromatography with electron capture detection. Finally, the MeHg flux was calculated using the chamber. The method was applied to simulated experiments, and the results showed that the MeHg fluxes in the air–water system were higher than those in the air–soil–water system. The method was also successfully applied to the field measurements of an environment polluted by a chemical factory, and the results showed that the MeHg fluxes across the air–soil and air–water interfaces were 0.21–3.09 and 0.14–0.79 ng m^–2 h^–1, respectively. The method will be a useful tool in the environmental study of MeHg.     

Self- and heteroassociates of cumyl hydroperoxide: FTIR-spectroscopy, chemometrics (factor analysis) and quantum chemical calculations

Self- and heteroassociation of cumyl hydroperoxide and acetophenone in n-decane solutions were studied by FTIR spectroscopy (3100–3700 cm⁻¹, 298–358 K). To interpret spectroscopic data, the new approach of factor analysis was offered. Equilibrium constants and thermodynamic parameters of associate formation were determined. The DFT calculations of cumyl hydroperoxide conformations, their self- and heteroassociates were carried out.     

Photodecomposition of poly(styrene peroxide)

Photodecomposition of poly(styrene peroxide) (PSP) has been carried out in detail by irradiating (300-360 nm) the PSP solution in CHCl₃ and the products were analyzed by gas chromatography-mass spectrometry (GC-MS) method. In addition to benzaldehyde, α-hydroxy acetophenone and phenyl glycol reported in earlier studies, two new products, viz., α-methoxy acetophenone and α-benzyloxy acetophenone were also observed, the mechanism of their formation discussed. The plausible reasons for the higher percentage of disproportionation products in PSP photolysis compared to that reported in its thermolysis are also discussed.     

Detachment of colloids from a solid surface by a moving air-water interface

Colloid attachment to liquid–gas interfaces is an important process used in industrial applications to separate suspended colloids from the fluid phase. Moving gas bubbles can also be used to remove colloidal dust from surfaces. Similarly, moving liquid–gas interfaces lead to colloid mobilization in the natural subsurface environment, such as in soils and sediments. The objective of this study was to quantify the effect of moving air–water interfaces on the detachment of colloids deposited on an air-dried glass surface, as a function of colloidal properties and interface velocity. We selected four types of polystyrene colloids (positive and negative surface charge, hydrophilic and hydrophobic). The colloids were deposited on clean microscope glass slides using a flow-through deposition chamber. Air–water interfaces were passed over the colloid-deposited glass slides, and we varied the number of passages and the interface velocity. The amounts of colloids deposited on the glass slides were visualized using confocal laser scanning microscopy and quantified by image analysis. Our results showed that colloids attached under unfavorable conditions were removed in significantly greater amounts than those attached under favorable conditions. Hydrophobic colloids were detached more than hydrophilic colloids. The effect of the air–water interface on colloid removal was most pronounced for the first two passages of the air–water interface. Subsequent passages of air–water interfaces over the colloid-deposited glass slides did not cause significant additional colloid removal. Increasing interface velocity led to decreased colloid removal. The force balances, calculated from theory, supported the experimental findings, and highlight the dominance of detachment forces (surface tension forces) over the attachment forces (DLVO forces).     

Application of tertiary amines for arsenic and selenium signal enhancement and polyatomic interference reduction in ICP-MS analysis of biological samples

Water soluble tertiary amines enhance signals and decrease polyatomic chloride interferences in the direct inductively coupled plasma – mass spectrometric (ICP-MS) determination of As and Se in biological samples. Preliminary experiments with amine concentrations and nebulizer flow rates produced element and interference signal intensity changes. Arsenic and Se ICP-MS determination parameters have been optimized by a simplex procedure with amines in an argon plasma or without amines but with addition of N₂ to the Ar. Variables include RF (radio frequency) power, nebulizer gas flow rate, intermediate gas flow rate, and amine concentration or nitrogen gas flow rate. Detection limit, minimization of polyatomic ion intensities, and reproducibility have been evaluated as reponse factors. The signal enhancement and element-to-molecular interference ratios differ to some extent with analyte intensity optimum operating conditions. The detection limits with addition of nitrogen (16 pg mL^–1 for As and 180 pg mL^–1 for Se) or of amines (8 pg mL^–1 for As and 120 pg mL^–1 for Se) and the extent of chloride interference minimization were compared. Amines addition was more beneficial. Biological standard reference materials and food and fecal samples were analyzed following different sample dissolution procedures.     

Thermal degradation of poly(4-chloromethyl-α-acetoxystyrene) and poly(4-chloropropyl-α-acetoxystyrene)

The thermal degradation behaviour of two poly(4-ω-chloroalkyl-α-acetoxystyrene)s has been studied by means of dynamic and isothermal thermogravimetric analysis and gas chromatography-mass spectroscopy. The results show that two reactions occur during the first stage of the process. An elimination reaction gives acetic acid as major volatile species and a residue formed of para-substituted polyphenylacetylenes. A depolymerization reaction gives principally the para-substituted acetophenone corresponding to the starting monomer, and explains the low molecular weights of the residues. These two reactions are simultaneous in the case of poly(4-chloromethyl-α-acetoxystyrene), but are distinguishable in the case of poly(4-3-chloropropyl-α-acetoxystyrene). Kinetic parameters of the overall decomposition of these two polymers have been calculated and compared with those of poly(4-2-chloroethyl-α-acetoxystyrene).     

Esterification of C2−C16 dicarboxylic acids to n-butyl esters in aqueous solutions for their gas chromatographic analysis

Summary C₂–C₁₆ dicarboxylic acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification in water/n-butanol mixtures with mole ratios between 0.02 and 2.53 can be utilized for the quantitative determination of the dicarboxylic acids by gas chromatography. The presence of water does not interfere at water/n-butanol mole ratios below 0.27. For mole ratios above 0.27 anhydrous sodium sulfate has been used for binding the water. The mole ratio range was 0.25–0.75 for anhydrous sodium sulfate/water, and 0.32–1.3 for sulfuric acid/anhydrous sodium sulfate.     

Quantitative gas-chromatographische Bestimmung von Acetophenonrestmengen in Mannichbase

Zusammenfassung Ein Verfahren zur quantitativen gas-chromatographischen Bestimmung von Acetophenonrestmengen (0,1–4,0%) in Mannichbase wurde ausgearbeitet. Als flüssige Phase diente Polyethylenglykol PEG 1540 und Chromosorb G als Träger. Die Analyse wurde unter isothermischen Bedingungen (150° C) mit einem Flammen-Ionisationsdetektor durchgeführt. Das Verfahren des inneren Standards wurde angewendet und die graphische Abhängigkeit des Acetophenongehalts (%) vom Verhältnis der Acetophenon und Phenoloberflächen (A _a /Aph) bestimmt. Nach der entwickelten Methode können Acetophenonrestmengen in industrieller Mannichbase bestimmt werden.

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Quantitative gas-chromatographic determination of residual acetophenone in mannich base

Summary A procedure was worked out for the determination of 0.1–4.0% of residual acetophenone in commercial Mannich base. Mobile phase was polyethyleneglykol PEG 1540 and Chromosorb G served as carrier material. Isothermic conditions (150° C) were applied and a flame-ionisation detector was employed. The method of internal standard was utilized and the dependence of the acetophenone content (%) on the ratio of the acetophenone and phenol peak areas was determined. The new method was successfully used for the analysis of industrially produced Mannich base.

     

Degradation of Organic Contaminants in Water by Pulsed Corona Discharge

Degradation of organic contaminants in water by high-voltage pulse discharges was investigated. The effects of gas flow rate and liquid conductivity on the degradation of 4-chlorophenol were studied. With the increase of time, the liquid conductivity increases, which have an important effect on discharge. Meanwhile, with the increase of time, the concentration of H₂O₂ increases. Addition of 200 mg/L H₂O₂, the conversion of 4-chlorophenol was greatly enhanced. This may be due to the synergistic effect of high-voltage pulsed discharge and H₂O₂. Also, it was found that the influence of quantity of TiO₂or CuO on degradation of acetophenone is not apparent, maybe the presence of metal oxides hinders the formation of plasma channel due to increase of collusions between metal oxides and oxygen.     

Determination of trace amounts of morpholine and its thermal degradation products in boiler water by HPLC

Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 g ml^–1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.     

Sigma complexes in the pyrimidine series

Complexes of the Meisenheimer type — potassium salts of 2H-5-nitro-4,6-dimethoxy-2-acetonyl- and 2-phenacylpyrimidines — were obtained for the first time by reaction of 5-nitro-4,6-dimethoxypyrimidine with acetone and acetophenone in the presence of potassium hydroxide. The structures of the complexes were proved by their oxidation to, respectively, 5-nitro-4,6-dimethoxy-2-acetonyl- and 2-phenacylpyrimidines and by means of their PMR and IR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1389–1391, October, 1978.     

Gas chromatographic determination of chlorothalonil and its metabolite 4-hydroxy-2,5,6-trichloroisophtalonitrile (HTI) in water

Summary A gas chromatographic method, with electron capture detection and mass spectrometric confirmation, is described for the determination of chlorothalonil and its metabolite 4-hydroxy-2,5,6-trichloroisophtalonitrile (HTI) in water samples. Water is saturated with sodium chloride and acidified to pH<2 with dilute sulfuric acid. After extraction with dichloromethane, HTI was methylated with diazomethane. The extract obtained was cleaned with basic alumina. Chlorothalonil and the methylated HTI-derivative were determined by gas chromatography with electron capture detection (GC-ECD) and confirmed by gas chromatography-mass spectrometry (GC-MS). The limit of detection, depending on the nature of the water samples is for both compounds between 0.01–0.03 g 1^–1 water. The average recovery in ground water is 87% for chlorothalonil and 82 % for HTI.