A convenient and sensitive method for haloacetic acid analysis in tap water by on‐line field‐amplified sample‐stacking CE–ESI‐MS

In this study, we propose a simple strategy based on flow injection and field‐amplified sample‐stacking CE–ESI‐MS/MS to analyze haloacetic acids (HAAs) in tap water. Tap water was passed through a desalination cartridge before field‐amplified sample‐stacking CE–ESI‐MS/MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300‐ to 1400‐fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected‐ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on‐line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively.     

Physicochemical and adsorption properties of hypercross‐linked polystyrene with ultimate cross‐linking density

The paper describes unexpected properties of hypercross‐linked polystyrenes with ultimate cross‐linking degrees of 300, 400, and 500%, where three, four, or five methylene links, respectively, could bind each polystyrene phenyl ring to its spacious neighbors. The polymers exhibit a strong electron spin resonance signal, unusual spectra in IR, UV, and visible ranges, and they are not typical dielectrics. The nonfunctionalized hypercross‐linked polymers absorb significant amounts of inorganic acids, salts, and bases due to interactions of protons or other cations with electron‐donating fragments of the aromatic network with the high extent of mutual connectivity and also due to dispersion interactions of anions with the polymer matrix.     

Physico-chemical aspects of polyethylene processing in an open mixer. Part 25: Mechanisms of aldehyde and carboxylic acid formation

Aldehydes and acids can be formed in numerous reactions in oxidizing polyethylene melts. Significant amounts of aldehydes result from β-scission of alkoxy radicals that are formed on bimolecular hydroperoxide decomposition. There are also large amounts of aldehydes expected from acid-catalyzed decomposition of allylic hydroperoxides as soon as enough acids have accumulated for efficient catalysis. There are difficulties in explaining the formation of aldehydes at a constant rate in sufficient amount for explaining the experimental data. There are much less difficulties with the constant rate of carboxylic acid formation. The α,γ-keto-hydroperoxides that are formed on chain propagation might account for the bulk of the acids formed at a constant rate.The foremost problems with the acids pertain to their formation at increasing rates in the initial as well as in the advanced stages. Formation and decomposition of α,β-di-hydroperoxides and α,γ-di-hydroperoxides is a possibility in this respect. Similarly, α,β-keto-hydroperoxides might be formed on peroxidation in the α-position to ketone groups in the advanced stages. There are considerable difficulties in elucidating the exact role of the aldehydes that are usually seen as the main precursors of the acids. Although there are many possibilities for transformation of aldehydes into acids, the free radical mechanisms envisaged usually have considerable disadvantages. These disadvantages result essentially from fast decarbonylation of acyl radicals and even faster decarboxylation of acyl-oxy radicals. Direct transformation of peracids into acids on reaction with double bonds is always a possibility. Moreover, in the low temperature range (150-160 °C) where hydroperoxides are accumulating, direct reaction of aldehydes with primary and/or secondary hydroperoxides will also yield acids.     

Physico-chemical aspects of polyethylene processing in an open mixer. Part 24: Experimental kinetics of aldehyde and carboxylic acid formation

The experimental kinetics for carboxylic acids shows more complexity than that for ketones. The fitting of the experimental results for the initial stages to the equation consisting of a linear and a quadratic term in processing time accounts well for the ketone data but not for the acid data. Instead of that, the data for the acids show fair fit to an equation containing a linear term and another term that is cubic in processing time. In the temperature range of the experiments the linear term is practically constant. The cubic term increases strongly with temperature. The combination of a linear and a quadratic term can account for the advanced stages of processing. The corresponding quadratic term shows strong increase if the processing temperature passes from 150 to 160 °C. However, for higher processing temperatures it remains constant within experimental error. The difference carbonyl absorbance measured after treatment of the polyethylene films with ammonia corresponds to the sum of the acids and aldehydes. It shows similarly complex kinetics. Some of the difficulties encountered with the experimental kinetics cannot be resolved with the data available. It is only the comparison with the formal kinetics based on potential mechanisms of product formation that allows for better understanding of the experimental results.     

Degradation of Amino-(3-methoxyphenyl)methanephosphonic Acid by Alternaria sp

Alternaria sp. isolated from the surface of carrot ( Daucus carota ) seeds appeared to be able to degrade amino-(4-methoxyphenyl)-methanephosphonic acid using it as a sole source of carbon, nitrogen, and phosphorus for growth.     

1H and 13C NMR Determination of the Enantiomeric Purity of Substituted 4-Amino-3- (thien-2-Yl)-Butyric Acids and 4-Amino-3-(Benzo[b]Furan-2-yl)-Butyric Acids,Ligands of the GabaB Receptor.

The enantiomeric composition and absolute configuration of 4-Amino-3-(benzo[b]furan-2-yl)-Butanoic Acids and of 4-Amino-3-(thien-2-yl)-Butanoic Acids 1 may be accurately determined by ¹H and ¹³C nuclear magnetic resonance analysis of the corresponding derivatives 3 prepared by reaction with chiral reagents. Correlation with HPLC is signaled.     

高寒草地暖季肥育牦牛肉质特性研究

对暖季育肥的麦洼牦牛的肉质特性进行了较系统的测试和分析,测定了10头供试牦牛肌肉中的PH值、系水率、肉的贮存损失、熟肉率和烹调损失率,肉色及大理石纹评分等,分析了肌肉中营养成分,微量元素含量及氨基酸含量;还测定了牦牛脂肪的熔点、碘价和皂化价,暖季育肥的补饲添加剂和埋植增重剂除对肉质特性的某些指标引起一些改变外,并未使肉质特性发生明显变化,牦牛埋植增重剂后引起肌肉中激素含量增加,牦牛肉质特性的研究对探明影响牦牛肉品质的因素,牦牛肉的保存和品质改善具有重要意义,将为牦牛肉品资源的开发利用积累有益的资料。     

Use of Micelles in the TLC Separation of Polynuclear Aromatic Compounds and Amino Acids

Abstract

The polynuclear aromatic compounds (PNA): anthracene, napthalene, phenanthrene, pyrene, pyrenecarboxaldehyde, benzo (a) pyrene, benzo (e) pyrene, perylene and fluorene can be chromatographed on polyamide TLC sheets using an aqueous micellar solution cf sodium dodecylsulfate (SDS) as the mobile phase. Reversed micellar solutions (of sodium dioctylsulfosuccinate) were used in a reverse phase chromatographic separation of amino acids. Some amino acids tended to streak slightly rather than move as discrete spots. Conditions could be adjusted, however, so that most of the amino acids and all PNA's would move as spots.     

游离芳香氨基酸和半胱氨酸对光诱导高铁肌红蛋白还原的影响

肌红蛋白(Myoglobin,Mb)中血红素辅基不仅具有储氧功能,也能吸收特定波长的光而影响蛋白功能表达。实验发现,部分游离的氨基酸对光诱导高铁肌红蛋白(metM b,Fe(III)-Mb)的还原过程及还原程度都有重要作用,因此,本文采用紫外-可见吸收光谱、圆二色谱、三维荧光光谱法,在光照体系中加入拥挤试剂来模拟细胞内拥挤环境,研究芳香氨基酸[色氨酸(Trp)、苯丙氨酸(Phe)、酪氨酸(Tyr)、半胱氨酸(Cys)]对metM b还原的影响。结果表明,含-OH或-SH的氨基酸(Tyr、Cys)能使metM b发生较好的光还原,无-OH或-SH基团的氨基酸(Trp、Phe)对metM b的光还原作用较弱,氨基酸促进metM b光还原的整个过程可能是分子间电子转移的过程。metM b在拥挤环境聚蔗糖70(Ficoll 70)中的光诱导还原程度比在稀溶液中高,拥挤试剂Ficoll70对蛋白的二级结构起保护作用,能够稳定血红素微环境。     

UPLC测定烟叶中的氨基酸含量

采用UPLC法测定烟叶中氨基酸的含量。Waters Acquity UPLC BEH C18色谱柱(2.1mm×100mm,1.7μm),AccQ.Tag Ultraa Eluent A及AccQ.Tag Ultraa Eluent B梯度洗脱,流速为0.7mL·min-1,波长:248nm,柱温55℃。18种氨基酸在0.0030-0.204mg/mL范围内有良好的线性关系(r0.9994),平均回收率(n=6)为98.7%。该方法10min内18种氨基酸可完全分离且具有快速、准确、重复性好的特点。