Gas chromatographic determination of phenol compounds with automatic extraction and derivatization

Two gas chromatographic procedures for the determination of a variety of substituted phenols in water samples are described. The phenols were extracted or extracted-derivatized by using a continuous liquid-liquid extraction-derivatization system and quantified with flame ionization detection. Ethyl acetate was found to be the most efficient solvent for phenols whereas n-hexane yielded essentially the same recoveries for derivatized phenols. Between 0.1 and 300 mg/l of the different phenols can be detected with a relative standard deviation 1.1 and 3.7%. The acetate esters of six phenols were formed by the direct addition of acetic anhydride to the organic extractant. The stable acetate esters thus formed were isolated by using a standard dimethyl polysiloxane gas chromatographic column.     

Catalytic Thioalkylation of Phenols Based on Mannich‐Type Phenol

A thioalkylation of phenols involving reactive phenols, aldehydes, and thiols is described under Mannich‐type phenol catalysis to afford thiomethyl phenols in good yields.     

Oxidant‐Controlled Catalytic Transformations of Phenols with Unexpected Cleavage of Aromatic Rings

Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well‐developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under‐represented. This work describes a novel CuCl‐catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag₂CO₃ as the oxidant. Interestingly, simply changing the oxidant to K₂S₂O₈ results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant‐controlled catalytic transformations of phenols.     

A mild conversion of arylboronic acids and their pinacolyl boronate esters into phenols using hydroxylamine

Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields.     

黄渤海近岸海域酚类内分泌干扰物分布特征及其来源解析

在黄渤海近岸海域采集了34个水体样品,利用HPLC-MS/MS分析了双酚A、辛基酚、壬基酚、2,4-二氯酚、对叔丁基苯酚和对特辛基苯酚等6种酚类内分泌干扰物的含量,并探讨了其分布特征及来源.结果表明,中国北部近岸海域6种酚类内分泌干扰物的含量范围在5.25～1351.20ng/mL之间.结合因子分析和层次聚类分析结果,说明渤海、黄海近岸海域中酚类化合物主要以辛基酚、壬基酚、2,4-二氯酚为主,局部海域伴有双酚A的高残留;从整个海域范围看,黄渤海近岸海域水体中酚类化合物污染状况具有区域特征,整体呈现出南高北低的特点,且酚类物质分布具有明显的地区特性,一定程度上具有聚集性;来源解析结果表明黄渤海近岸海域中酚类内分泌干扰物主要来源为生活污水和工业废水.     

渗透汽化膜处理含酚废水

用四种不同结构的聚二甲基硅氧烷及其改性有机硅膜分离舍酚废水.研究了分离温度、酚浓度以及不同种类酚对透过速率及分离系数的影响。结果表明聚合物中有机硅成份的含量对透过速率及分离系数均有较大影响。渗透汽化法分离含酚废水是一个有前途的方法。     

Development of an SPME/ATR-IR chemical sensor for detection of phenol type compounds in aqueous solutions.

A new method, based on a combination of solid phase micro-extraction (SPME) and attenuated total reflection infrared (ATR-IR) spectroscopy, was developed for the detection of phenols in aqueous solutions. Several types of phenols were studied including phenols attached to methyl, hydroxyl, chlorine and nitro groups, which are environmentally toxic. Because of the polarity of the phenol-type compounds, the performance of six polymers in attracting phenols was investigated. Results indicated that poly(acrylonitrile-co-butadiene) was the most suitable SPME phase among the investigated polymers. To further increase the sensitivity in phenol detection, factors, such as the pH effect, salt effect and thickness of the SPME phase, were investigated. Results indicated that pH values affected the neutral form percentage of the analytes strongly and, hence, affected the detected signals. Due to the acid nature of phenols, phenol detection occurs best in solutions with a low pH value. A two- to three-fold increase in signals was observed after the addition of salt into the solution. The results on the examination of standard curve linearity indicated that the regression coefficients (R2) were higher than 0.996 for four types of phenols. The obtained detection limits for phenols were lower than 200 micrograms L-1 for most of the compounds.     

Determination of phenols in landfill leachate-contaminated groundwaters by solid-phase extraction

A solid-phase extraction method for phenols in landfill leachates was developed and optimized in order to solve the expected and observed problems associated with an anaerobic matrix containing high concentrations of salts and organic matter. Isolute ENV+ cartridges exhibited the best retention of phenols of the four sorbents examined, and was the only cartridge which a 1 L leachate sample could pass through. With the other cartridges, clogging made this impossible. The final method, which included 27 different phenols, gave detection limits of <0.1 microg/L (drinking water concentration limit for pesticides) for most phenols (25), and for 12 phenols <0.01 microg/L. Recovery rates (determined for four concentrations in the range 1-25 microg/L, two replicates of each) were in the range 79-104% (SD 1-12%), except for phenol (26+/-1.3%) and 2-methoxyphenol (62+/-4.2%). Up to 12 different phenols could be identified in leachates from three Danish landfills, ranging in concentration from 0.01 to 29 microg/L, which is at the lower end of the concentration range usually found for phenols in landfill leachates (sub-microg/L to mg/L).     

对位取代酚亚甲基桥三聚物的合成

本文报道通过2, 6-二羟甲基对取代酚和合适的对取代酚的缩合制备一系列对取代酚亚甲基桥三聚物的方法。产率一般为50%左右。     

Effect of phenols on the potentiometric response of a nitrate-ion-selective electrode

The effect of phenols containing different electron-withdrawing substituents on the potentiometric responses of several liquid PVC membranes containing the complex trioctylmethylammonium-nitrate, TOMA(+)NO(3)(-), is analyzed. The results make it possible to separate these phenols into two groups; those phenols containing electron-releasing groups, which produce almost Nernstian slopes, and those containing electron-withdrawing substituents, which generate sub-Nernstian slopes. The highly negative standard free energy of transfer of the aryl phenolic group from water to a cationic polar head suggests that these phenols are mainly located in the membrane phase associated with TOMA(+) via a cation-pi interaction. It seems that the strength of this interaction, and hence of the nitrate dissociation, is affected by the presence of phenols in an extension which correlates well with the kind of phenol present in these membranes and, consequently, with the type of their potentiometric responses.     

聚乙烯吡咯烷酮对油中酚类物质的吸附性能

煤焦油中酚类物质的有效分离,可实现其高附加值利用。针对酚类物质的分离,本研究采用聚乙烯吡咯烷酮(PVP)为吸附剂,研究了其对模型油中邻甲酚、间甲酚、对甲酚、1-萘酚和2-萘酚等的吸附性能。研究发现,PVP对酚类物质具有较大的吸附容量,其中对间甲酚、对甲酚、1-萘酚和2-萘酚的最大吸附量均可达1000 mg/g以上。同时发现,PVP上的Lewis碱性位点(C=O和C-N)可与酚羟基之间形成氢键作用,该作用的强度受酚类物质空间位阻影响。PVP具有一定的吸附选择性,在苯并呋喃或喹啉存在下,依然能够有效吸附2-萘酚。此外,使用过的PVP可再生并重复利用,同时实现酚的回收。可见,PVP是一种可用于分离煤焦油中酚类物质的优良吸附剂。     

Antioxidant activity of olive phenols: mechanistic investigation and characterization of oxidation products by mass spectrometry

In this work, the antioxidant activity of olive phenols is first characterized by their stoichiometries n(tot)(number of radicals trapped per antioxidant molecule) and their rate constants for the first H-atom abstraction k(1) by the stable radical DPPH. It appears that oleuropein, hydroxytyrosol and caffeic acid have the largest k(1) values, whereas dihydrocaffeic acid, an intestinal metabolite of caffeic acid, is the best antioxidant in terms of n(tot). For phenols with a catechol moiety n(tot) is higher than two, implying an antioxidant effect of their primarily formed oxidation products. A HPLC-MS analysis of the main products formed in the AAPH-induced oxidation of olive phenols reveals the presence of dimers and trimers. With hydroxytyrosol and dihydrocaffeic acid, oligomerization can take place with the addition of water molecules.The antioxidant activity of olive phenols is then evaluated by their ability to inhibit the AAPH-induced peroxidation of linoleic acid in SDS micelles. It is shown that olive phenols and quercetin act as retardants rather than chain breakers like alpha-tocopherol. From a detailed mechanistic investigation, it appears that the inhibition of lipid peroxidation by olive phenols can be satisfactorily interpreted by assuming that they essentially reduce the AAPH-derived initiating radicals. Overall, olive phenols prove to be efficient scavengers of hydrophilic peroxyl radicals with a long lasting antioxidant effect owing to the residual activity of some of their oxidation products.     

Surface Modification of a Supported Pt Catalyst Using Ionic Liquids for Selective Hydrodeoxygenation of Phenols into Arenes under Mild Conditions

The selective and efficient removal of oxygenated groups from lignin-derived phenols is a critical challenge to utilize lignin as a source for renewable aromatic chemicals. This report describes how surface modification of a zeolite-supported Pt catalyst using ionic liquids (ILs) remarkably increases selectivity for the hydrodeoxygenation (HDO) of phenols into arenes under mild reaction conditions using atmospheric pressure H₂. Unmodified Pt/H-ZSM-5 converts phenols into aliphatic species as the major products along with a slight amount of arenes (10 % selectivity). In contrast, the catalyst modified with an IL, 1-butyl-3-methylimidazolium triflate, keeps up to 76 % selectivity for arenes even at a nearly complete conversion of phenols. The IL on the surface of Pt catalyst may offer the adsorption of phenols in an edge-to-face manner onto the surface, thus accelerating the HDO without the ring hydrogenation.     

Effect of the Structure of Phenols on Their Activity in the Reaction with Ethylbenzene Peroxy Radicals

In a study of the reactivity of sterically protected phenols in the reaction with ethylbenzene peroxy radicals as a function of their molecular structure and as compared with unprotected phenols, we have established the major characteristic features of the structure–antioxidant activity relation for phenols of different structures.     

A convenient ring formation of 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans from phenols and 2-aryl-2,2-dialkylacetaldehydes

A new and simple route for the preparation of 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans from phenols is described. In the presence of an acid catalyst phenols react with 2-aryl-2,2-dialkylacetaldehydes, prepared in good yield from 2-arylacetonitriles in 2 steps, to give 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans. Electron-donating substituents were required on the phenols in order to give 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans in good yield.     

环境水质中酚类优先监测物的气相色谱法测定

以气相色谱法（ＧＣ）测定了环境水质中的重点酚类污染物。选择乙酸酐作衍生化试剂、甲苯为萃取剂,比较了不同的衍生ｐＨ条件,给出了氢火焰离子化检测器（ＦＩＤ）分离测定酚类污染物的精密度和检出限。方法简便实用,经５家实验室验证表明：适用于监测地表水和污水中的酚类物质。６种酚类优先监测物的检测限为０．６～７μｇ／Ｌ。     

Simulating phenol high-performance liquid chromatography retention times as the pH changes. Mobile phase pH versus buffer pH

The HPLC retention times of several substituted phenols have been measured and simulated using Advanced Chemistry Development's LC simulator, using 50% acetonitrile (ACN) as the mobile phase. For alkyl- and nitro-substituted phenols, the quality of the simulation improves when pH of the mobile phase is estimated and used in the simulation. Simply using the pH of the buffer gives simulation results that are not as close to the actual retention times. However, the opposite is the case for halogenated phenols. The pK(a) values in 50% ACN for some of these phenols have also been determined, which tend to be one unit higher than the aqueous pK(a) values reported in the literature.     

Investigation into the determination of phenols extracted from automobile exhaust gases

A method is described in which phenols extracted from the condensate of automobile exhaust gases are determined directly by GLC. The quantities of various phenols found are calculated by using tridecane as an internal standard. The emission of phenols from cars running on fuels containing different concentrations of aromatics, and on leaded and lead-free fuels, has also been considered. The results show that the concentration of total phenols is dependent on the type of sample, and is strongly dependent on the concentration of aromatic hydrocarbons and of tetraethyl-lead in the fuel.     

Isolation and bioactivities of organic acids and phenols from walnut shell pyroligneous acid

Based on differences in acidity, organic acids and phenols were enriched by pH gradient extraction method from walnut shell pyroligneous acid. Contents of organic acids and phenols were measured by acid-base titration method and Folin colorimetric assay, respectively to assess the effectiveness of the extraction. In addition, the antimicrobial activity of the organic acids and antioxidant activity of phenols extracted were investigated. Chemical components of the extracts that were from the optimal concentrations of NaHCO₃ and NaOH were measured by GC-MS. The results showed that 5% NaHCO₃ could enrich the highest amount of organic acids, whereas 4% NaOH could enrich the highest amount of phenols. The enriched organic acids exhibited high antimicrobial activity, and the enriched phenols exhibited antioxidant activity under low concentrations, and demonstrated dosage dependency.     

Identification and determination of microgram amounts of phenol and chlorophenols by the Ring Oven technique

This paper reports investigations carried out on phenol and a number of chloro-substituted phenols using the Ring Oven technique in conjunction with the reagent 4-aminoantipyrine. The reactions with individual phenols and combined groups of phenols using in situ, and extraction methods are discussed.