REFRACTOMETRY AND TEXTURES OF METHYL-CYANOETHYL CELLULOSE/DICHLOROACETIC ACID LIQUID CRYSTA LLI NE SOLUTIONS^+

An Abbe refractometer with a rotatable polarizer mounted on the eyepiece is used for determining the two principal refractive indices of methyl-cyanoethyl cellulose/dichloroacetic acid liquid crystalline solutions. The critical concentration where the mesophase appears can be determined according to the variation of the increment of the refractive index with the concentration. Mesophase textures of the liquid crystalline solutions are observed and the influence of the concentration on mesophase textures is also discussed.

Dichloroacetic Acid (DCA)-Induced Cytotoxicity in Human Breast Cancer Cells Accompanies Changes in Mitochondrial Membrane Permeability and Production of Reactive Oxygen Species

Cancer cells utilize cytosolic glycolysis for their energy production even in the presence of adequate levels of oxygen (Warbug effect) due to mitochondrial defects. Dichloroacetic acid (DCA) shifts cytosolic glucose metabolism to aerobic oxidation by inhibiting mitochondrial pyruvate dehydrogenase kinase (PDK) and increasing pyruvate uptake. Therefore, DCA has potential in reversing the glycolytic metabolism defect in cancerous cells. DCA is also known to induce apoptosis in a number of cancer cell lines, the mechanism of which is not well understood. In this study, an attempt has been made to investigate the effects of DCA on aggressive human breast cancer (MCF-7) cells as compared with less aggressive mouse osteoblastic (MC3T3) cells. Cell cytotoxicity was determined by MTT, crystal violet and Trypan blue exclusion assays. Western blot was used to detect any changes in the expression of apoptotic markers. Flow cytometry was used to measure apoptotic and necrotic effects of DCA. Mitochondrial integrity was determined by change in mitochondrial membrane potential (Δψm), whereas oxidative damage was determined by production of reactive oxygen species (ROS). DCA caused a concentration-dependent cytotoxicity both in MCF-7 and MC3T3 cell lines. MCF-7 cells were most affected. Flow cytometry results showed a significantly higher apoptosis in MCF-7 even at lower concentrations of DCA. However, higher concentrations of DCA were necrotic. Western blotting showed an increased expression of Mn-SOD-1 upon DCA treatment. Further, DCA decreased Δψm and increased ROS production. The effects of DCA were more pronounced on MCF-7 cells as compared to MC3T3 cells. Our results suggest that DCA-induced cytotoxicity in cancerous cells is mediated via changes in Δψm and production of ROS.

Treatment Process for the Low Residual of Dichloroacetic Acid in Lauramidopropyl Betaine

Without using sodium sulfite or oxides,The content of residual dichloroacetic acid in lauramidopropyl betaine was reduced by technology improvement.The effects of reaction temperature,pressure,reaction time,pH and color on the residual dichloroacetic acid were studied.The optimum conditions were screened out,i.e.processing time of 3 h,processing temperature of 120℃,pressure of 0.11 MPa and pH of 12.0.Hereby the dichloroacetic acid residues could be reduced from 450 mg/kg to less than 50 mg/kg,and the color of the product was below 70 hazen.

Effects of adding sodium dichloroacetate to low-protein diets on nitrogen balance and amino acid metabolism in the portaldrained viscera and liver of pigs

Background:Identifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein(LP)diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants.In this study,we investigated the effects of adding sodium dichloroacetate(DCA)to a LP diet on nitrogen balance and amino acid metabolism in the portal-drained viscera(PDV)and liver of pigs.To measure nitrogen balance,18 barrows(40±1.0 kg)were fed one of three diets(n=6 per group):18%crude protein(CP,control),13.5%CP(LP),and 13.5%CP+100 mg DCA/kg dry matter(LP-DCA).To measure amino acid metabolism in the PDV and liver,15 barrows(40±1.0 kg)were randomly assigned to one of the three diets(n=5 per group).Four essential amino acids(Lys,Met,Thr,and Trp)were added to the LP diets such that these had amino acid levels comparable to those of the control diet.Results:The LP-DCA diet reduced nitrogen excretion in pigs relative to that of pigs fed the control diet(P<0.05),without any negative effects on nitrogen retention(P>0.05).There were no differences between the control and LP-DCA groups with respect to amino acid supply to the liver and extra-hepatic tissues in pigs(P>0.05).The net release of ammonia into the portal vein and production rate of urea in the liver of pigs fed the LP-DCA diet was reduced relative to that of pigs fed the control and LP diets(P<0.05).Conclusion:The results indicated that addition of DCA to a LP diet can efficiently reduce nitrogen excretion in pigs and maximize the supply of amino acids to the liver and extra-hepatic tissues.

离子色谱法测定生活饮用水中二氯乙酸、三氯乙酸和氯酸盐

目的:建立离子色谱法对生活饮用水中的二氯乙酸、三氯乙酸和氯酸盐进行同时测定。方法:选择AS19离子色谱柱作为分析柱,氢氧化钾淋洗液体系,浓度范围在6~40 mmol/L之间进行梯度淋洗,进样体积500μL,流速1.0 mL/min;水样经Ag/H净化柱处理和0.2μm滤膜过滤后,进行离子色谱分析。结果:二氯乙酸、三氯乙酸和氯酸盐在5~100μg/L范围内线性关系良好,r≥0.999,检出限分别为0.97μg/L、2.29μg/L、0.75μg/L,回收率在93.0%~99.7%之间,相对标准偏差≤1.74%。结论:该方法操作简单、灵敏度高、准确性好,适用于日常监测任务。

气相色谱法测定生活饮用水中二氯乙酸和三氯乙酸

本次检验方法依据《生活饮用水标准检验方法 第10部分:消毒副产物指标》(GB/T 5750.10—2023),建立气相色谱法测定饮用水中二氯乙酸和三氯乙酸。样品采用浓硫酸酸化,1.2-二溴丙烷为内标物质萃取,硫酸-甲醇溶液衍生,然后经SE-30型号毛细管柱分离,电子捕获检测器检测。结果表明:二氯乙酸和三氯乙酸线性范分别在0~200μg/L和0~100μg/L,线性关系良好,相关系数R>0.998,检出限均为0.9μg/L,最低检出质量浓度为2.7μg/L,加标回收率范围依次为在95.7%~104%和97.3%~102%,相对标准偏差为1.2%~2.8%。结论:本次研究饮用水中二氯乙酸和三氯乙酸标准曲线、检出限、精密度和准确度的实验数据均符合标准方法质量要求,但发现该实验方法繁琐,不易操作,衍生时间较长等缺点,实验室可基于此次的初步研究,可继续探讨优化二氯乙酸和三氯乙酸检测条件,具有指导意义。

离子色谱法同时测定饮用水中二氯乙酸和三氯乙酸

使用离子色谱法同时测定饮用水中二氯乙酸和三氯乙酸时,在氢氧根体系中同时加入碳酸钠和乙腈可有效改善分离度,不需要梯度淋洗即可实现有效分离。测定结果显示,二氯乙酸和三氯乙酸在0~200.0μg·L^(-1)线性关系良好,相关系数均达0.999以上,二氯乙酸检出限为0.8μg·L^(-1),三氯乙酸检出限为1.0μg·L^(-1),相对标准偏差均小于4%,加标回收率均在94.0%~100.7%。

在线超滤-离子色谱法同时测定生活饮用水5种消毒副产物

为了同时测定生活饮用水中的5种消毒副产物DCAA,TCAA,ClO_(2)^(-),BrO_(3)^(-)和ClO_(3)^(-)的含量,旨在构建一种高效便捷的在线超滤-离子色谱法。通过使用Metrohm metrosep a supp18-250型色谱柱,淋洗液结合浓度为14 mmol/L NaOH淋洗液,流速0.6 mL/min,以及质量分数为1%H_(2)SO_(4)抑制器再生液,运用英蓝在线超滤技术,可有效地对生活饮用水中的三氯乙酸(CCl_(3)COO^(-))(TCAA)、二氯乙酸(CHCl_(2)COO^(-))(DCAA)、亚氯酸盐(ClO_(2)^(-))、氯酸盐(ClO_(3)^(-))、溴酸盐(BrO_(3)^(-))进行分离检测,且同时进行其方法线性、准确度、精密度、检出限、定量限及加标回收率的检测。通过试验发现,标准曲线相关系数远高于0.995,相对标准偏差不超过3%。此外,加标回收率介于96.7%~102.7%,在37 min内,就能够完成5种生活水体中的消毒副产物的分析,每个物质组分检测灵敏度极高,检测周期极短,分析效率很高,因此适用于大规模的生活饮用水的测试。

生活饮用水中二氯乙酸、三氯乙酸测定方法的优化与探究

本优化方法以GB/T 5750.10-2023为参照,对生活饮用水中二氯乙酸、三氯乙酸的测定方法的进行优化和探究。通过对测定二氯乙酸、三氯乙酸的样品前处理过程、仪器设备条件两方面进行优化。结果显示,优化后的生活饮用水中二氯乙酸、三氯乙酸最低检测质量浓度测定10次的检出率分别为70%和60%;二氯乙酸高中低不同浓度的相对标准偏差分别为2.01%、3.39%、3.67%,三氯乙酸高中低不同浓度的相对标准偏差分别为2.98%、3.71%、2.39%;二氯乙酸高中低不同浓度的回收率在92.85%~96.61%,三氯乙酸高中低不同浓度的回收率在91.14%~97.13%。经优化的检验检测的数据和结果符合标准要求,方法操作简单易行,最低检测质量浓度合适,精密度好、准确度高,可以准确测定生活饮用水中二氯乙酸和三氯乙酸。

Dichloroacetic acid and rapamycin synergistically inhibit tumor progression

Mammalian target of rapamycin(mTOR)controls cellular anabolism,and mTOR signaling is hyperactive in most cancer cells.As a result,inhibition of mTOR signaling benefits cancer patients.Rapamycin is a US Food and Drug Administration(FDA)-approved drug,a specific mTOR complex 1(mTORC1)inhibitor,for the treatment of several different types of cancer.However,rapamycin is reported to inhibit cancer growth rather than induce apoptosis.Pyruvate dehydrogenase complex(PDHc)is the gatekeeper for mitochondrial pyruvate oxidation.PDHc inactivation has been observed in a number of cancer cells,and this alteration protects cancer cells from senescence and nicotinamide adenine dinucleotide(NAD^(+))exhaustion.In this paper,we describe our finding that rapamycin treatment promotes pyruvate dehydrogenase E1 subunit alpha 1(PDHA1)phosphorylation and leads to PDHc inactivation dependent on mTOR signaling inhibition in cells.This inactivation reduces the sensitivity of cancer cells'response to rapamycin.As a result,rebooting PDHc activity with dichloroacetic acid(DCA),a pyruvate dehydrogenase kinase(PDK)inhibitor,promotes cancer cells'susceptibility to rapamycin treatment in vitro and in vivo.

Behaviour of Haloacetic Acids in Drinking Water Distribution Systems

To guarantee the safety of drinking water quality after chlorination, the formation, distribution and factors influencing the concentrations of haloacetic acids (HAAs) in a water distribution system (WDS) were investigated both on a full-scale WDS (FWDS) and pilot-scale WDS (PWDS) within a city in northern China. The results of both investigations showed that trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were the dominating types of HAAs. In the FWDS, variations in the HAA content showed negative correlations with total residual chlorine, pH and non-purgeable organic carbon (NPOC) and positive correlations with temperature and UV254. In the PWDS, the concentration of HAAs after rechlorination followed the rule of ‘first rise and then fall’; therefore, locating an appropriate rechlorination point and lowering the single chlorine dosage could be used as effective measures to control the HAA content in WDSs. © 2016, Tianjin University and Springer-Verlag Berlin Heidelberg.

Enhanced ozonation of dichloroacetic acid in aqueous solution using nanometer ZnO powders

Nanometer zinc oxide （ZnO） powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid （DCAA） in aqueous solution. The batch experiments were carded out to investigate the effects of key factors such as catalyst dosage, ozone dosage, solution pH and tert-butyl alcohol （t-BuOH） on the degradation efficiency of DCAA. Density functional theory （DFT） was adopted to explore the mechanism of generating hydroxyl radical （＇OH） on the ZnO surface. The results showed that adsorption and ozonation processes were not effective for DCAA removal, and the addition of ZnO catalyst improved the degradation efficiency of DCAA during ozonation, which caused an increase of 22.8% for DCAA decomposition compared to the case of ozonation alone after 25 min. Under the same experimental conditions, the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93, 6.88, and 10. With increasing the concentration of t-BuOH from 10 to 200 rag/L, the degradation of DCAA was significantly inhibited in the process of catalytic ozonation, indicating that ZnO catalytic ozonation followed ＂OH reaction mechanism. Based on the experimental results and DFT analysis, it is deduced that the generation of ＂OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface. It is also concluded that ZnO may be an effective catalyst for DCAA removal, which could promote the formation of .OH derived from the catalytic decomposition of ozone.

Determination of Glycolate Acid, Mono- and Dichloroacetic Acids in Synthetical Betaine by Anion-exchange Chromatography

An anion-exchange chromatography method combined solid phase extraction （SPE） was developed for the simultaneous analysis of glycolate acid （GL）, monochloroacetic acid （MCA） and dichloroacetic acid （DCA） in synthetical betaine products. The analytes and unknown anionic impurities were well separated on a Metrosep A supp5 anion-exchange column （150 mm×4 mm） with 2.0 mmol/L Na2CO3＋2.0 mmol/L NaHCO3 solution as eluent. Suppressed conductivity detection was used. A strong cation exchange （SCX） solid phase extraction （SPE） cartridge was used to reduce the concentration of matrix betaine and a Cleanert IC-Ag pretreatment cartridge was used to remove high Cl- concentration. The detection limits of GL, MCA and DCA were 0.09, 0.017 and 0.05 μg/L, respectively. The relative standard deviations （RSDs） of the retention times and peak areas were less than 0.09% and 0.49%, respectively. The recoveries of the three analytes were between 90.6% and 100.8%. The analytical results showed that GL and DCA were present in high concentration and no MCA was found when the proposed ion chromatography method was applied to three synthetical betaine samples. The proposed method is simple, sensitive and timesaving, and is also suitable for routine analysis in quality control of synthetical betaine products.

Preparation and characterization of Pd/Fe bimetallic nanoparticles immobilized on Al_2O_3/PVDF membrane:Parameter optimization and dechlorination of dichloroacetic acid

Using a liquid-solid phase inversion method, a hybrid matrix poly（vinylidene fluoride）（PVDF） membrane was prepared with alumina（Al2O3） nanoparticle addition. Pd/Fe nanoparticles（NPs） were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy（SEM） and Transmission Electron Microscopy（TEM）. The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid（DCAA） dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.

超高效液相色谱串联质谱法和离子色谱法测定饮用水中二氯乙酸、三氯乙酸的比对

目的:分别利用超高效液相色谱串联质谱法与离子色谱法对生活饮用水中二氯乙酸、三氯乙酸进行测定,比较其检测性能。方法:样品经滤膜过滤后,以乙腈/0.05%乙酸水溶液作为流动相,梯度洗脱,以三重四极杆质谱检测器进行检测,根据保留时间和特征离子峰进行定量分析。离子色谱法以KOH作为淋洗液,IonPac AS19分析柱和IonPac AG19保护柱,8~40 mmol·L^(-1)梯度淋洗,以电导检测器检测。从检测时间、准确度、精密度、检出限等方面对两种方法进行对比。结果:两种方法测定二氯乙酸、三氯乙酸线性良好,超高效液相色谱串联质谱法测定二氯乙酸检出限为0.000 6 mg·L^(-1),三氯乙酸检出限为0.001 8 mg·L^(-1),检测时间为4.5 min;离子色谱法测定二氯乙酸检出限为0.001 2 mg·L^(-1),三氯乙酸检出限为0.002 2 mg·L^(-1),检测时间为32 min。两种方法精密度和准确度均满足实验要求。结论:生活饮用水中二氯乙酸、三氯乙酸可以用以上两种方法进行定性和定量分析,其中离子色谱法所需有机试剂少,但检测时间长,检测限较高;超高效液相色谱串联质谱法检测限较低,灵敏度高,检测时间短。日常检测工作中,可根据水样具体情况,选择合适的检测方法。

氯乙酸的发展历程及新工艺展望

从乙酸氯化的原理和氯乙酸的生产工艺出发,较为系统地阐述了乙酸氯化法制备氯乙酸工艺在国内外的发展历程,综述了氯乙酸从间歇法到连续法生产工艺的演进。同时对国内氯乙酸行业的发展路线做了全面梳理。

离子色谱法测定饮用水中二氯乙酸和三氯乙酸

建立了一种直接进样离子色谱法测定饮用水中二氯乙酸、三氯乙酸的方法。采用高容量的阴离子色谱柱,进样体积为500μL,以25 mmol.L-1Na2CO3为淋洗液,流速1.0 mL.min-1,在30 min内可以测定饮用水中二氯乙酸和三氯乙酸,二氯乙酸、三氯乙酸的检出限分别为5.11,14.32μg.L-1,回收率在85.0%~103.2%。应用此方法对南方某市水源水和出厂水中二氯乙酸和三氯乙酸进行了测定。

离子色谱-串联电喷雾质谱法检测自来水中二氯乙酸和三氯乙酸

建立了一种采用离子色谱-串联电喷雾四级杆质谱联用技术检测自来水中可致癌的饮用水消毒副产物二氯乙酸和三氯乙酸的方法。该方法使用IonPacPrototype-10高容量阴离子交换柱为分离柱,以ICS-3000多功能色谱系统的淋洗液自动发生装置在线产生不同浓度的KOH淋洗液,在合适的梯度条件下,实现对自来水样品中两种卤代乙酸和多种常见阴离子的高效分离,经抑制器将淋洗液抑制为近中性后,在不添加有机溶剂的情况下,进入API3200 ESI-MS/MS质谱系统,选取适合的离子对和温度、能量条件,进行准确定量分析。在优化的色谱和质谱条件下,二氯乙酸和三氯乙酸的检出限分别为0.053和0.46μg/L。峰面积校正曲线的线性范围均跨越两个数量级以上。对4种不同浓度的标准溶液和实际样品连续9次进样,峰面积的相对标准偏差小于7%。选取北京市18个区县及全国部分省市的自来水样品进行检测,所得结果令人满意。挑选其中的典型样品进行不同浓度的标准加入实验,回收率在86.7%-119.0%之间。

离子色谱法测定环境水体中的卤乙酸和草甘膦

采用新型抑制器和电导检测器,建立了大体积直接进样离子色谱法测定环境水体中草甘膦和氯乙酸的方法。采用大容量IonPacAS9-HC阴离子色谱柱,进样体积为500μL,以25 mmol/L Na2CO3＋2.0 mmol/LNaOH为淋洗液,流速1.0 mL/min,在22 min内可以测定环境水体中的草甘膦、氯乙酸,其中草甘膦、二氯乙酸、三氯乙酸的检出限分别为0.03、0.005、0.014 mg/L（S/N=3）,回收率在92.6%～103.9%。用于测定河水和自来水中的草甘膦、二氯乙酸及三氯乙酸,结果令人满意。

衍生化气相色谱法同时测定尿中三氯乙烯的3种氯代乙酸代谢产物

建立了以三氯化铁为催化剂,乙醇与尿中三氯乙烯的3种代谢产物(一氯乙酸、二氯乙酸、三氯乙酸)乙酯衍生化的气相色谱测定方法。对乙酯衍生化温度、时间、三氯化铁用量、乙醇用量进行探讨,确定了最优化的衍生条件为4 mL尿样加入1.05 mmol三氯化铁、2 mL乙醇,90℃水浴50 min,经2 mL正己烷萃取后直接进样测定。尿中一氯乙酸、二氯乙酸、三氯乙酸的浓度分别在40～2 400、20～1 000、10～500μg/L范围内呈良好线性,相关系数分别为0.999 8、0.999 3和0.999 2,3种氯代乙酸在尿样中的平均加标回收率为104%、109%和106%。方法的检出限分别为4.67、1.32、0.27μg/L。该方法乙酯衍生化试剂低毒、低腐蚀性,反应条件温和,操作简便,已成功用于三氯乙烯职业暴露人群尿样中3种代谢产物的生物检测。