Capillary electrophoresis-electrospray ion-trap mass spectrometry for the separation of chlorophenols

Eighteen positional isomers of chlorophenols were separated by capillary electrophoresis (CE) and detected on-line by electrospray ionization ion-trap mass spectrometry (MS). Conditions for the coupling of CE to MS, e.g., the concentration of carrier electrolyte, the sheath liquid composition and the sheath gas flow-rate were optimized. Diethylmalonic acid (5 mM) at pH 7.25 and isopropanol-250 mM dimethylamine (80:20) as sheath liquid were used. The activation parameters for ion-trap mass spectrometric analysis of chlorophenols were optimized. The mass spectra, obtained for all the analytes, revealed that the [M-H]- ion was the base peak for all chlorophenols. Moreover, conditions for CE-MS-MS detection were established and [M-H-HCl]- ions were detected.     

Detection and determination of chlorophenols and chlorophenoxyacetic acids by instrumental analysis

A quantitative method for the determination of chlorophenols and chlorophenoxyacetic acids in aqueous solutions is described. The samples investigated contained 2-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,6-trichlorophenol and their phenoxyacetic acid derivatives. The total amount of chlorophenols is determined by spectrophotometry, the ratio of individual chlorophenols by gas chromatography and the total quantity of phenoxyacetic acids by acidimetric titration. The determinations are carried out after extraction with diethyl ether, carbon tetrachloride and petroleum ether, respectively.     

Photocatalytic degradation of chlorophenols under direct solar radiation in the presence of ZnO catalyst

The photocatalytic degradation of chlorophenols was evaluated under direct solar radiation using commercial ZnO catalyst. Effects of several parameters such as a catalyst loading, pH of solution and initial concentration on the degradation process have been investigated. The photocatalytic degradation efficiency of chlorophenols at the optimum value of the parameters was compared under similar experimental conditions. The results of efficiency and mineralization showed the degradation of 2-chlorophenol and 2,4-dichlorophenol compound with the first order kinetic rate and the rate constant decreases as the initial concentration of the chlorophenols increase. However, the rate constant was strongly affected by type of chlorophenols compound present either 2-chlorophenol or 2,4-dichlorophenol. The highest removal of chlorophenols was obtained after 120 min and the final intermediate compounds of chlorophenols degradation are lower molecular weight compound consisting of acetic acid which was analyzed through the HPLC.     

Determination of chlorophenols in landfill leachate using headspace sampling with ionic liquid-coated solid-phase microextraction fibers combined with gas chromatography–mass spectrometry

A new microextraction technique based on ionic liquid solid-phase microextraction (IL-SPME) was developed for determination of trace chlorophenols (CPs) in landfill leachate. The synthesized ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), was coated onto the spent fiber of SPME for extraction of trace CPs. After extraction, the absorbed analytes were desorbed and quantified using gas chromatography–mass spectrometry (GC/MS). The term of the proposed method is as ionic liquid-coated of solid-phase microextraction combined with gas chromatography–mass spectrometry (IL-SPME-GC/MS). No carryover effect was found, and every laboratory-made ionic liquids-coated-fiber could be used for extraction at least eighty times without degradation of efficiency. The chlorophenols studied were 2,4-dichlorophenol (2,4-DP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP). The best results of chlorophenols analysis were obtained with landfill leachate at pH 2, headspace extraction for 4 min, and thermal desorption with the gas chromatograph injector at 240 °C for 4 min. Linearity was observed from 0.1 to 1000 μg L⁻¹ with relative standard deviations (RSD) less than 7% and recoveries were over 87%. The limit of detection (LOD) for pentachlorophenol was 0.008 μg L⁻¹. The proposed method was tested by analyzing landfill leachate from a sewage farm. The concentrations of chlorophenols were detected to range from 1.1 to 1.4 μg L⁻¹. The results demonstrate that the IL-SPME-GC/MS method is highly effective in analyzing trace chlorophenols in landfill leachate.     

Resonance electron capture by aniline molecules and its derivatives

Processes of the formation of negative ions from aniline and its derivatives were studied by the resonance electron capture technique. The results were compared with those obtained earlier for molecules of benzene, phenol, and chlorophenols. It was concluded that the processes of formation of negative ions in aniline differ substantially from those in benzene and phenol. The triplet series of resonances beginning from the resonance at 2.6 eV is observed.     

Rapid determination of nineteen chlorophenols in wood, paper, cardboard, fruits, and fruit juices by gas chromatography/mass spectrometry.

Although the use of pentachlorophenol (PCP) is prohibited in most countries, it is still widely found in the wood of pallets, containers, crates and in cardboard, paper, etc. Such material may contain not only PCP but other chlorophenols as well. Wooden crates and cardboard boxes are often used to store and transport fresh fruits. Consequently, chlorophenols present in the wood may contaminate the stored fruits by migration. To ascertain that packaging, storage material, and fruit raw materials are free from chlorophenol residues, we developed a rapid and sensitive method for the detection of 19 chlorophenols by gas chromatography/mass spectrometry (GC/MS). The test portions are directly extracted and acetylated in a solution of sodium carbonate in the presence of acetic anhydride and hexane. The hexane layer is analyzed, without further purification, by GC/MS in the selective-ion monitoring mode. The method allows the analysis of >40 samples/day with detection limits of <20 microg/kg for chlorophenols in wood, cardboard, and paper, and <2 microg/kg for chlorophenols in fruits. Typical recoveries of all chlorophenols were 94% from paper, 115% from cardboard, 51% from wood (depending on the size of the chips or shavings), and 93% from fruit puree.     

Catalytic hydrodechlorination reaction of chlorophenols by Pd nanoparticles supported on graphene

Chlorophenols are widely used as industrial chemicals such as herbicides, insecticides, wood preservatives, and disinfectants. However, chlorophenols are very toxic materials and they have become the cause of current environmental issues. Hydrodechlorination (HDC) reaction is a more environmentally friendly removal method of chlorophenols than other methods. In this paper, Pd–modified graphene was prepared and applied to HDC reaction. Pd supported on graphene (refer to Pd/G) was prepared using the recently reported microwave irradiation method. The Pd(II)/GO was made by impregnation methods of palladium precursors in solution phase and was subsequently reduced to Pd/G by microwave irradiation. The morphological and chemical structure of the Pd/G was characterized by XRD, SEM, ICP-MS, EDS, and TEM. It was found that the graphene-based Pd catalyst showed the highest catalytic performance among Pd/Y, Pd/MCM-41, and Pd/G catalysts. This is attributed to the smaller particle size and higher dispersions of Pd nanoparticles on the graphene surface. The catalytic HDC of chlorophenols was investigated. For HDC reaction, 100 ppm solution of chlorophenols such as 4-chlorophenol, six isomers of dichlorophenol, and 2,3,5-trichlorophenol in isopropanol was treated with catalyst and base, such as Na₂CO₃ and K₂CO₃, under a hydrogen gas at ambient pressure. The progress of the chlorophenol decomposition was analyzed with GC. All chlorophenols were completely decomposed within 2 h in the 3 % Pd/G catalyst. The reaction pathway of chlorophenols was elucidated from the conversion of chlorophenols and selectivities of products. The reuse of the catalyst was also studied. The performance of the recycled catalyst in HDC reaction up to six successive runs was observed.     

Ein neuer Photoionisationsdetektor für die Gas-Chromatographie

Zusammenfassung In einem Gas-Chromatographen wird der FID durch einen neuen Photoionisationsdetektor (PID) ersetzt. Der Photoionisationsdetektor wird kurz beschrieben und auf seine operativen Vorteile (einfache Anwendung, Fehlen von Betriebsmitteln wie Brenngase usw.) hingewiesen. Es werden einige Messungen mit dem modifizierten Gerät vorgenommen und die Ergebnisse mit denen des FID verglichen. Bedingt durch systemspezifische Vorteile des Photoionisationsdetektors—verglichen mit dem FID ist der Rauschpegel stark vermindert und wegen des größeren Wirkungsgrades der Photoionisation steht ein höheres Signal zur Verfügung—sowie durch das Fehlen von O₂ und seinen Problemen ist eine erhebliche Empfindlichkeitssteigerung des Gesamtsystems festzustellen. Außerdem ergibt sich, wiederum verglichen mit dem FID, ein weiterer Dynamikbereich. Weiter werden mit Hilfe des Photoionisationsdetektors gewonnene Meßergebnisse mit publizierten Ergebnissen anderer Detektoren verglichen und die Vorteile des PID aufgezeigt.

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A new photoionization detector for gas chromatography

Summary In a commercially available GC the FID was replaced by a newly designed photoionization detector (PID). The PID and its operational advantages (ease of use, no neccessity for combustion gas and the related facilities) are described briefly. Some measurements are made with the such modified GC and the results are compared with those obtained with the FID. Specific advantages of the PID — compared to a FID — the noise level caused by the system is lower and (due to the higher ionization efficiency of the PID) the signal is larger — and due to the lack of oxygen and its altendant problems the overall system sensitivity is strikingly better. In addition, the dynamic range — again compared with the FID — is wider. Further, performance data obtained with the PID are compared with published data of other detectors and the advantages of the PID are shown clearly.

     

Application of carbon nanotubes as solid-phase extraction sorbent for analysis of chlorophenols in water samples

The aim of this work was to investigate the efficiency of various MWCNTs as SPE materials for the preconcentration of chlorophenols. The COOH-functionalized MWCNTs and MWCNTs were used as SPE sorbents. To evaluate the capability of MWCNTs for the preconcentration of chlorophenols from water samples, 2,4-chlorophenol, 4-chlorophenol, 2,4,6-chlorophenol, 2,6-chlorophenol, 3,4-chlorophenol, and 2-chlorophenol were used as model compounds. Chlorophenols were extracted with acetone, methanol, ethanol, and dichloromethane, and determined by gas chromatography–mass spectrometry. COOH-functionalized MWCNTs <8 nm were found to be the best sorbent for the tested chlorophenols. For COOH-functionalized MWCNTs <8 nm, the recovery rates for all chlorophenols were higher than 50% when acetone or ethanol was used as eluents. In the case of dichloromethane elution, recovery rates for chlorophenols were from 62.0% for 2,6-DCP to 116.8% for 2,4-DCP; only for 2,4,6-TCP was the recovery rate 30.6%. Similar percentage recoveries were achieved with methanol as the eluent.     

Pneumatik in der Gas-Chromatographie

Zusammenfassung Quantitative Analysen in der temperaturprogrammierten Gas-Chromatographie mit Wärmeleitfähigkeitszellen sind nur möglich, falls die Trägergasgeschwindigkeit am Kolonnenausgang konstant ist. Die übliche Regelung der Trägergasgeschwindigkeit durch Differenzdruckregler bricht zusammen für diesen Zweck, wenn der pneumatische Widerstand der Capillarkolonne groß ist. Es wird eine Methode vorgeschlagen, die Zeitverzögerung der pneumatischen Regelung zu vermeiden.

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Summary Quantitative analyses in programmed-temperature gas chromatography are possible with katharometer only, if the outlet velocity of the carrier gas is constant. The usual control of the flowrate by differential pressure controllers breaks down for such purposes if the pneumatical resistance of the capillary column is high. A method is proposed to avoid the time delay of the pneumatical regulation.

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I. Mitt.: Deininger, G., u. I. Halász: diese Z. 228, 81 (1967).

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Die Autoren danken der Deutschen Forschungsgemeinschaft, Bad Godesberg, und der Max Buchner-Forschungsstiftung, Frankfurt a.M., für finanzielle Unterstützungen zu dieser Arbeit.     

The removal of chlorinated organic herbicide in water by gamma-irradiation

In this study, the radiation-induced degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide in aqueous solution was studied under various conditions as a function of irradiation dose in the absence and presence of hydrogen peroxide. The obtained data confirmed that largest yield of radiolytic degradation is obtained in oxidation processes/ionizing radiation, where oxidation is carried out with hydroxyl radicals. For complete degradation of 50?ppm 2,4-D, a required dose was lower in the presence of hydrogen peroxide. The formed major toxic phenolic intermediates were 2,4-dichlorophenol (2,4-DCP) and 4-chlorophenol (4-CP). The chemical analysis of the 2,4-D and the intermediates resulted from the radiolytic degradation were performed using a gas chromatography associated to mass spectrometry (GC?CMS) with ion trap dedector (ITD) and ion chromatography (IC). The formation of chlorophenols in addition to chloride, formaldehyde and carboxylic acids was studied as a function of absorbed dose.     

氯酚为前生体生成二噁英类的研究进展

评述了氯酚作为前生体生成二噁英类的问题，总结了热过程、光转化、酶反应三种途径中氯酚生成二噁英类的条件及机制。热过程中氯酚缩合成二Wu英的主要影响因素为：温度、热解时间、含氧量和催化剂；而光转化过程中光强、溶剂种类、光敏物质的存在对氯酚生成Wu英有影响，热过程和光转化的反应机制均是通过自由基来完成的。     

Trennung,Identifizierung und Bestimmung von Bactericiden auf der Basis von halogenierten Aromaten mittels Gas-Chromatographie

The separation of a mixture of 22 bactericides has been achieved by gas chromatography on columns with silicone rubber W-982 as stationary phase with temperatures between 100° and 300°C. The unchanged compounds as well as their silylation products have been used. The latter are more conveniently used especially for the quantitative determination. To be able to calculate the retention indices after Kovats gas chromatography has been performed isothermally at 180°C for the more volatile compounds and at 250°C for all other bactericides.The retention indices obtained under these conditions are tabulated together with the limits of detection.     

Bestimmung der Mutarotation von Monosacchariden mittels Gas-Chromatographie — Aufklärung verschiedener Fructose- und Sorboseformen mit Gas-Chromatographie,Infrarot- und Massenspektroskopie

The mutarotation of a monosaccharide in solution can be investigated by gas chromatography. After varying time intervals the dissolved monosaccharides were deep-frozen with liquid air, lyophilized, silylated and the α- and β-forms gas-chromatographically determined. The calculated velocity constants for glucose are in good agreement with the results from rotation measurements. The gas chromatogram of mutarotated fructose shows five components. By means of infrared and mass spectroscopy the pyranoside and furanoside forms as well as the open-chain ketal form can be characterized. The composition of the equilibrium mixture was investigated. Similarly, sorbose and galactose were studied. A furanoside, a pyranoside and an open-chain ketal form could be shown from sorbose, while galactose gave a furanoside and two pyranoside forms.     

Determination of Chlorophenols in Wastewater with Methyl Chloroformate Derivatization,Solid Phase Extraction,and Gas Chromatography–Mass Spectrometry

The determination of chlorophenols in wastewater with methyl chloroformate derivatization, solid phase extraction, and gas chromatography–mass spectrometry is reported. In order to employ this combined solid phase derivative extraction method, quantitative extraction was performed by the introduction of 100 mL of sample in 1.0 mol L^?1 sodium hydroxide into a column containing 500 mg of packed resin at a flow rate of 1.0 mL/min. The chlorophenols were retained and derivatized quantitatively in the column by the introduction of 0.25 mL of methyl chloroformate. The derivatized analytes were eluted with 5.0 mL of hexane before the effluent was dried under a stream of nitrogen. The dried solution was diluted to a volume of 50 µL with hexane followed by analysis by gas chromatography–mass spectrometry. The preconcentration parameters were optimized and under these conditions: limits of detection from 0.010 to 0.423 µg L^?1, a preconcentration factor of 2500, and precision values from 4.8 to 7.7% as the relative standard deviation were obtained. The method was employed for the analysis of water samples and the recoveries of the analytes were between 76 and 103%.     

Use of ethyl ethers, deuteriomethyl ethers and cyclic n-butylboronates of hydroxychlorobiphenyls in identification of metabolites of polychlorinated biphenyls.

The mass spectra and gas chromatographic properties of a number of chlorobiphenylols, chlorobiphenyldiols, chlorophenols and naphthols, as well as their methyl, deuteriomethyl and ethyl ethers and some cyclic n-butylboronates have been investigated. Metabolism experiments with 4'-chloro-4-biphenylol showed that the selective use of ethylation and methylation is most effective in both detection and structure elucidation of metabolites partly methylated by metabolic processes. The usefulness of deuteriomethylation in such studies seems to be limited. The formation of cyclic n-butylboronates provides specific information on o-dihydroxy derivatives of chlorobiphenyls.     

Pneumatik in der Gas-Chromatographie

Zusammenlassung Extrem hohe TrÄgergasgeschwindigkeiten sind in der druckprogrammierten Gas-Chromatographie (PPGC) nicht ungewöhnlich. Für das Split-system vor der Kolonne wird eine einfache pneumatische Regelung beschrieben, um sehr hohe Verluste an TrÄgergas zu vermeiden oder unerwünschte VerÄnderungen des Eingangsdrucks beim Schlie\en desProbeteilers zu verhindern. Die Konstruktion einer Misch- und Splitkammer MS zwischen der Kolonne und dem Detektor wird gebracht. Mit Hilfe von MS und der Regelung des Ausgangsdrucks der Kolonne sind quantitative Analysen in PPGC mit massengeschwindigkeitsanzeigenden Detektoren möglich. Eichfaktoren der Komponenten, Rausch und Drift des Flammenionisationsdetektors sind dabei unabhÄngig von der Strömungsgeschwindigkeit in der Kolonne. Die nur komplizierte Anwendbarkeit von konzentrationsempfindlichen Detektoren in der quantitativen PPGC wird diskutiert.

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Summary In pressure (i.e. flow) programmed gas chromatography (PPGC) extremely high carrier-gas flow-rates are not unusual. A simple pneumatic control is described for the splitting system before the column to avoid extreme losses of the carrier gas or to avoid unwanted changes of the inlet pressure by closing the splitter. A mixing-and splitting-chamber MS between the column and the detector is constructed. With the help of MS and the control of the outlet pressure of the column quantitative analysis in PPGC with mass-flow sensitive detectors is possible. The normalization factors of the compounds, the noise and the drift of the flame-ionization detector is now independent of the flow rate in the column. The sophisticated applicability of concentration sensitive detectors in quantitative PPGC is discussed.

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III. Mitt.: Deininger, G., u. I. Halász: diese Z. 228, 321 (1967)

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Die Autoren bedanken sich bei der Deutschen Forschungsgemeinschaft, Bad Godesberg, mit deren finanzieller Unterstützung diese Arbeit ausgeführt wurde.     

Separation of chlorophenoxyacetic acids and chlorophenols by using capillary zone electrophoresis

In this study, the choice of electrolyte systems for the separation and detection of a range of chlorophenoxyacetic acids and chlorophenols by means of capillary zone electrophoresis (CZE) is discussed. A series of acetate buffers over the buffering capacity pH range 4.03-5.5 were initially chosen for the separation. It was found that chlorophenoxyacetic acids could be separated at pH 4.03 and 4.5 but the most satisfactory separation of chlorophenols was obtained at pH 5.5. The factors affecting separation selectivity, including the addition of organic modifiers, was also studied. The use of 25% 2-butanol, 5% ethylene glycol and 10% acetonitrile as organic solvents resulted in the total separation of both classes of these compounds but poor peak shape of chlorophenols resulted and a number of chlorophenoxyacetic acids were not well separated. A borate-phosphate buffer gave improved peak shape of chlorophenols. Further improved separation of the components of the mixture was obtained by the addition of 2 mM fully methylated-beta-cyclodextrin to the 35 mM borate- 60 mM phosphate buffer at pH 6.5, maintaining good peak shape. In this case, separation of the two compound classes, chlorophenoxyacetic acids and chlorophenols, is achieved, with complete resolution of individual compounds in less than 5 min with high efficiency (of the order of 150,000 plates for the ca. 40 cm column). The method is applied to a commercial 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide mixture.     

阴离子交换树脂富集净化环境水样中氯代酚方法的研究

采用阴离子交换树脂为萃取剂富集、净化环境水样中氯代酚类化合物（CPS）。选取8种具有代表性的CPs,对三种不同型号、两种不同交换形式的强碱阴离子交换树脂进行实验,筛选出最佳萃取剂及最佳实验条件。8种CPS在自来水水样中的回收率均大于95％;在海河水样中三、四、五氯代阶回收率大于92％。此外,本法与SeP－PakC18小柱法还进行了富集、净化污水中三氯酚（PCP）的对比实验,结果表明：本法净化效果好,PCP回收率90．5％,而C18小柱法背景干扰大,无法测量。     

Monitoring chlorophenols in industrial effluents by solid-phase microextraction–gas chromatography–mass spectrometry

A method for the determination of 19 chlorophenols in industrial effluents samples using solid-phase microextraction (SPME) coupled to gas chromatography–mass spectrometry has been developed. Four kinds of different SPME fibres have been studied. Among them, the polyacrylate and carbowax®-divinylbenzene fibres were the most adequate. The extraction process was optimized by means of the experimental design, which allows the study of a large number of factors with a reasonable number of experiments. The optimized method allows the determination of the studied chlorophenols in complex matrices with a high organic content with detection limits down to 0.07?ng?mL^?1 and RSD ranging from 4.4% to 13.8%. The recovery studies with spiked real effluent samples at low levels of chlorophenols ranged from 59.8% to 142.1% for the lowest level (0.5?ng?mL^?1) and from 79.6% to 115.8% for the highest spiked level (2?ng?mL^?1). These results show the suitability of the proposed method to monitor chlorophenols in complex samples. 2,4,5-TCP was detected at concentrations close to its limits of detection in effluents coming from an oil refinery.