Determination of priority pollutant phenols by isocratic HPLC

Summary An isocratic high performance liquid chromatographic method, able to determine ng/l of Priority Pollutant Phenols (PPP) in water, is proposed. A Nucleosil 5 C 18 column and an 30 mM ammonium acetate (pH 5.0): acetonitrile: methanol (56:34:10) eluent are used. Linearity ranges from 5–50 ppm of phenols; variation coefficients are about 4% (n=7) at the 30 ppm level with a 5μl injection. Dual UV detection helps to identify different phenols. The use of an anionic exchanger column and of methanol: hydrochloric acid (9:1) as eluent allows selective preconcentration of priority phenols and recoveries in the range 79–105%.     

Determination of phenols by HPLC down to PPT levels

Summary A mixture of eleven priority pollutant phenols (PPP) have been separated using a Dionex 4000 chromatograph; VAL-U-PAK ODS (250 × 4.6 mm I.D.) column; eluents A: CH₃CN/0.2M NaH₂PO₄/CH₃COOH 40/60/1 and B: CH₃CN with/without gradient; detectors: UV-254 nm and Pulse Amperometric Detector (PAD) with glassycarbon electrode (+1.20V). With preconcentration unit (guard RP-18 column) on line and PAD, detectability limit at ten ppt was achieved. The method has been applied for determination of PPP in tap-water and in leachates from sanitary and industrial landfill sites.     

高效液相色谱-质谱联用法测定纺织品中的含氯苯酚

建立了高效液相色谱-质谱联用法检测纺织品中五氯苯酚(PCP)、四氯苯酚(TeCP)。选用ZORBAX XDB-C18柱(50 mm×2.1 mm,3.5μm)为分析柱,流动相为V(甲醇)∶V(纯水)=88∶12,流速为200μL/min;质谱条件选用气动辅助电喷雾离子源(ESI),检测方式为负离子多离子反应检测(MRM);PCP、TeCP标准曲线线性范围均为0.1~100μg/L;回收率为90%~99%;相对标准偏差为3.5%~7.6%(n=5);方法检测低限为5μg/kg。方法适用于纺织品中PCP、TeCP的测定。     

高效液相色谱法测定印刷线路板热解油中的酚类化合物

建立了反相液相色谱法测定废旧印刷线路板热解油中的酚类化合物的方法,热解油经过滤并溶解在甲醇溶剂中可直接进样进行反相高效液相色谱分析,采用色谱柱为kromasil C18(4.6 mm i.d.×250 mm,5μm);流动相为乙腈/乙酸-乙酸铵缓冲溶液(0.01 mol/L,pH 4.0);柱温25℃;流速为1.0 mL/min,梯度洗脱进行分离,讨论了流动相的组成及其pH值等因素对组分分离产生的影响。实验结果显示,4种酚类化合物线性回归方程的相关系数r为0.9985~0.9996,高、中、低3个添加水平的加标回收率为96.3%~102.6%,相对标准偏差小于6%。     

Photoaccelerated oxidation of chlorinated phenols

Exposure to visible light increases the rate of oxidation of chlorinated phenols by hydrogen peroxide in aqueous solution in either the presence or the absence of iron-based catalysts, which may be explained by the aqueous photoreactions of chloroquinone intermediates.     

Radiolytic transformations of chlorinated phenols and chlorinated phenoxyacetic acids

Hydroxyl radical reactions of selected chlorinated aromatic phenols (2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol) and chlorinated phenoxyacetic acids [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-D methyl ester, 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP)] were studied using the radiolysis techniques of pulse radiolysis and gamma radiolysis. Hydroxyl radical addition was the prominent reaction pathway for the chlorinated phenoxyacetic acids and also for the chlorinated phenols at pH values below the pK(a) of the compounds. A very prominent change in (*)OH reactivity was observed with the chlorinated phenoxide ions in high pH solutions. Two different reaction pathways were clearly present between the hydroxyl radical and the chlorinated phenoxide ions. One of the reaction pathways was suppressed when the concentration of chlorinated phenoxide ions was increased 10-fold. Amid a greater electron-withdrawing presence on the aromatic ring (higher chlorinated phenoxide ions), the hydroxyl radical reacted preferably by way of addition to the aromatic ring. Steady-state experiments utilizing gamma radiolysis also showed a substantial decrease in oxidation with an increase in pH of substrate.     

中空纤维液相微萃取-高效液相色谱法测定纺织品中10种含氯苯酚类化合物

建立了中空纤维液相微萃取-高效液相色谱法测定纺织品中10种含氯苯酚类化合物的方法。系统地优化了影响萃取效率的因素,得到的最佳萃取条件为：萃取溶剂为正己烷,接受相NaOH溶液的浓度为0.10 mol/L,萃取时间为60 min,搅拌速度为600 r/min。在最佳萃取条件下,10种含氯苯酚在0.01～1.00 mg/L范围内线性关系良好（r>0.999）,10种含氯苯酚的检出限（信噪比为3）为0.01 mg/kg,富集倍数为95～101。在空白样品中添加0.01、0.05和0.1 mg/kg 3个不同水平的10种含氯苯酚类化合物,其平均回收率为78.8%～105.1%,相对标准偏差为0.3%～7.3%。研究结果表明该方法灵敏度高、简便、准确,可用于纺织品中含氯苯酚类化合物的测定。     

Gas-phase radiation-chemical formation of dioxins from chlorinated phenols

The gas-phase radiation-chemical formation of dioxins from chlorinated phenols in the electron-beam removal of toxic impurities from industrial gases is considered. A kinetic model of the process is proposed. Conditions under which the efficiency of removal of the above compounds from gases significantly decreases were determined with the use of this model. The results of a numerical simulation are compared with currently available experimental data.     

Determination of chlorinated paraffins by GC-MS

Summary Although chlorinated paraffins are widely used and therefore produced in large amounts (about 250 kt/a) — with well known problems —, there is a lack of a selective, highly sensitive and reproducible analytical method for the determination of these substances. Such a method is presented using GC/MS with electron impact ionization for their quantitative determination. The samples, pretreated with conc. sulphuric acid, were cleaned up by solid-phase extraction on alumina, and the chlorinated paraffins were determined by GC/MS using highly selective ion clusters.By this method, determination limits of 3 ng (corresponding to about 1.5 ppb) were routinely obtained. In contrast to the general methods of maximum signal selection or the selection of molecule ions in mass spectroscopy, the presented approach leads to higher selectivity, less discrimination between different types of chlorinated paraffins and allows to obtain further information on the degree of chlorination.     

Determination of ionol in oils in the presence of low-molecular-weight phenols using reversed-phase HPLC

A procedure was developed for extracting phenol-type antioxidants from oils. The extraction system consisted of isopropanol, 25% NH₃, water, and ammonium sulfate as a salting-out agent. The optimum conditions were found for determining ionol in the presence of phenol and alkylphenols in the isopropanol extract using reversed-phase HPLC with an UV-detector. The time of analysis was 55 min. The detection limits in oils (taking into account extraction preconcentration) were 0.0005 mg/L for phenol, 0.0006 mg/L for cresols, and 0.015 mg/L for ionol.     

HPLC determination of volatile phenols in wines

Summary An alternative to the traditional solvent extraction method used to extract and rapidly quantify ethyl-and vinylphenol and ethyl-and vinylgaiacol from wine is presented. The method is based on retention of volatile phenols on adsorbants. Among the tested resins, the most efficient, AG 2-X8 (anion exchange resin), worked as well with a synthetic solution as with wines. The percolation of clarified wine adjusted to pH 9 on this resin permits, in particular, the elimination of organic acids. Phenols are not eluted after rinsing the column with 1N HCl, but are eluted with methanol after this treatment. Good recovery (91 %) and good repeatability are observed. The eluate is directly analysed by HPLC on an RP18 column after two-fold dilution in water. The four volatile phenols were completely separated and detected by UV at 280 nm with high sensitivity (20–40 ppb). No interference with other compounds were noted in the different wines analysed.     

Sensitivity enhancement of chlorinated phenols by continuous flow liquid membrane extraction followed by capillary electrophoresis

This paper describes a new analytical system, based on the combination of continuous flow liquid membrane extraction (CFLME) enrichment and capillary electrophoresis (CE) separation, for analysis of chlorinated phenols in water samples. Five chlorinated phenols including 3-chlorophenol (3CP), 4-chlorophenol (4CP) 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) were separated by CE with Tris/sodium dihydrogen phosphate solution containing methanol 1% (v/v) as the run buffer. CFLME related parameters were investigated and optimal enrichment was obtained by using 0.3 mol L(-1) Tris as acceptor and with a sample pH 5.0, a sample flow rate of 4.0 mL min(-1), and an enrichment sample volume of 150 mL. The detection limit (S/N= 3) was 6.9, 1.0, and 1.7 ng mL(-1) for DCP, PCP, and TCP, respectively. The reproducibility (RSD%, n = 6) was 5.7 for DCP, 2.5 for PCP, and 2.8% for TCP (n = 6). The proposed method was applied to the determination of chlorinated phenols in spiked water samples with relatively satisfactory recoveries.     

The surprisingly facile thermal dehalogenation of chlorinated aromatics by a hydroaromatic donor solvent. Tautomerization of chlorinated phenols and anilines

Up to 600 K, chlorinated benzenes and naphthalenes are inert in a hydrogen atom donating solvent such as 9,10-dihydroanthracene. However, when a hydroxyl or amine group is attached to the 2 or 4 position relative to chlorine, a surprisingly facile and selective hydrodehalogenation occurs at temperatures between 530 and 630 K. These features are the result of the onset of tautomeric equilibria for the chlorophenols or -anilines, creating the corresponding enones or imines, respectively, as reactive intermediates. The mechanism of dehalogenation involves the rate-determining transfer of a hydrogen atom from the solvent to the reactive intermediate according to a reverse radical disproportionation (RRD), followed by elimination of chlorine. The reactivity of mono- and dichlorophenols, chloroanilines, 4-chloro-1-naphthol, and 4-chloro-1-naphthylamine dissolved in 9,10-dihydroanthracene has been investigated. By means of density functional theory (DFT) calculations, the energies for the tautomers and their hydrogen affinities have been established. The experimental selectivities could be adequately reproduced by the computed data.     

比浊法测定氯化石蜡中氯量

以Na2CO3-MgO-KOH为灰化固定剂,用灰化法处理氯化石蜡样品。对测定条件、灰化条件及AgCl胶体的稳定性进行了考察。建立了比浊法测定氯化石蜡中氯的新方法。线性范围为0~5μg/mL。测定结果的相对标准偏差≤0.6%,加标回收率为97.5%~102.3%。     

Characteristics of phenol and chlorinated phenols sorption onto surfactant-modified bentonite

Surfactant-modified bentonite was synthesized by replacing adsorbed Na+ with long-chain alkyl quaternary ammonium cation, hexadecyltrimethylammonium bromide (HDTMAB). The sorption isotherms of phenol, p-chlorophenol, and 2,4-dichlorophenol were modeled according to the Langmuir and Freundlich equations. The Langmuir isotherm was found to describe the equilibrium adsorption data well. The mechanisms and characteristics of sorption of these ionizable organic contaminants onto surfactant-modified bentonite from water were investigated systematically and described quantitatively. The sorption properties are affected by the treatment conditions, such as amount of organobentonite, and the properties of organic compounds. Results indicated that adsorption of phenols from water was in proportion to their hydrophobicities, which increased with chlorine addition (phenol相似文献   

Electroanalytical chemistry of chlorinated phenols at a glassy carbon electrode

The electroanalytical chemistry of chlorinated phenols at a glassy carbon electrode in various solvent—electrolyte media is described. Differential pulse voltammetry may be used to determine chlorinated phenols in a methanol—0.07 M sulfuric acid medium. The determination of pentachlorophenol in liquid formulations is described. Cyclic voltammetric Studies are used to investigate the electrochemical reaction mechanisms of chlorinated phenols. The electrochemical oxidation products of these compounds are quite reactive, and follow-up chemical reactions result in electrode filming under the conditions studied.     

Determination of sterically hindered phenols by gas-liquid chromatography

Conclusions The possibility has been shown and the optimum conditions have been found for the identification of various 4-alkyl-2,6-di-tert-butylphenols by gas-liquid chromatography on the stationary liquid phases poly(ethylene glycol adipate) and Apiezon-L deposited on Celite C22.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1618–1622, July, 1970.