具有丰富介孔Cu-SAPO-34催化剂制备及其低温氨气选择性催化还原反应(英文)

氮氧化物(NO_x)是主要的大气污染物之一,与光化学烟雾、全球气候变暖等环境问题密切相关.随着汽车产业的高速发展,柴油车排放尾气中的NOx脱除成为国内外尾气催化净化领域最突出的难点之一.其中氨气选择性催化还原技术(NH_3-SCR)由于其高效率、低成本的特征已成为主要的移动源脱硝技术.目前,实际应用中最广泛的是V_2O_5-WO_3(MoO_3)/TiO_2催化剂,然而一些不可避免的因素仍然存在,比如V具有较强的毒性,较高的操作温度,较窄的活性温度窗口以及易将SO_2氧化为SO_3导致催化剂表面会有大量的硫酸盐沉积而失活等.因此很有必要开发一种无钒SCR催化剂.近年来,分子筛负载过渡金属作为催化剂引起了研究者的广泛兴趣,其中Cu-CHA分子筛催化剂因其高SCR活性,高N2选择性,较宽的温度窗口以及优异的稳定性引起研究者的广泛关注.就Cu/SAPO-34而言,传统的制备方法是利用离子交换法将Cu离子引入到SAPO-34微孔孔道中,然而由于微孔会限制Cu离子的分布,导致绝大多数Cu优先分布在分子筛外表面,从而限制了其活性发挥.Martínez-Franco课题组利用双模板一步法成功制备了Cu-SAPO-34催化剂,提高了分子筛中活性Cu离子数目.Peden课题组发现在NOx的NH_3-SCR反应中Cu-SAPO-34催化剂存在低温动力学限制.因此开发一种具有丰富介孔的多级孔Cu-SAPO-34催化剂势在必行.我们利用一步水热晶化法成功制备了一系列具有丰富介孔的Cu-SAPO-34催化剂.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、氮气吸附-脱附、X射线衍射(XRD)、~(27)Al核磁共振(Al-NMR)、紫外可见漫反射光谱(UV-Vis DRS)、电感耦合等离子体-原子发射光谱(ICP-AES)、X射线光电子能谱(XPS)、氢气程序升温还原(H2-TPR)和电子顺磁共振(EPR)等表征手段研究了Cu-SAPO-34多级孔催化剂的物理化学性质.XRD测试结果证实,H-Cu-SAPO-34催化剂具有典型的CHA结构.TEM和N2吸附-脱附测试结果表明,H-Cu-SAPO-34催化剂具有丰富的介孔结构.Al-NMR测试结果表明,多种配位的Al物种存在于H-Cu-SAPO-34中.UV-Vis DRS测试结果证实了孤立Cu~(2+)和高分散的CuO的存在,没有观察到(Cu-O-Cu)2+和CuAl2O4物种的存在.ICP-AES和XPS测试结果表明,H-Cu-SAPO-34催化剂具有相似的Cu含量,并且H-Cu-SAPO-34-20催化剂具有最高的Cu~(2+)含量.H2-TPR测试结果表明,H-Cu-SAPO-34-20催化剂具有最低的孤立Cu~(2+)还原温度以及最高的孤立Cu~(2+)含量.这可能有利于其NH3-SCR活性提高.同时H2-TPR还表明,H-Cu-SAPO-34催化剂中存在含量不等的孤立Cu+,并且孤立Cu~(2+)是NH3-SCR反应的主要活性中心.EPR测试结果进一步表明,位于SAPO-34椭球腔内(Site(I))的孤立Cu~(2+)是该反应的主要活性位.由NO的NH3-SCR反应测试结果来看,相比于普通的Cu/SAPO-34催化剂,具有丰富介孔结构的H-Cu-SAPO-34催化剂呈现出更高的低温催化活性,同时H-Cu-SAPO-34-20催化剂具有最高的低温NH3-SCR催化活性,这与其较高的活性Cu~(2+)含量以及较低的孤立Cu~(2+)还原温度密切相关.动力学测试结果表明,所合成的H-Cu-SAPO-34多级孔催化剂具有相似的活化能(Ea=98 kJ/mol),并且该值远大于普通CHA基SCR催化剂,这意味着介孔的存在确实大大降低了反应物分子在H-Cu-SAPO-34孔道内的扩散阻力,提高了反应物分子与活性位的接触概率,从而提高了其低温NH3-SCR催化性能.     

自甲醇制取烃类催化剂的研制 第三报 催化剂活性稳定性的研究

在研究分批合成的ZSM—5分子筛催化剂用于自甲醇制取烃类反应中的重复情况时,发现每批催化剂的初活性稳定性相差很大,追究其原因是在离子交换后,氢型分子筛的SiO_2/Al_2O_3比变化很大,这种变化和活性稳定性之间有密切关系。在离子交换过程中,脱铝量的大小取决于晶粒大小及孔道通畅情况,它可由分子筛原粉吸附环已烷的量来表征。只有吸附量高的分子筛,才有可能成为SiO_2/Al_2O_3比高的氢型分子筛。然而,对SiO_2/Al_2O_3比相同的氢型分子筛,以对环已烷吸附量高的原粉制备成的催化剂活性稳定性为佳。     

原位合成的Cu-SSZ-13催化剂：结晶时间对NH3-SCR性能的影响

通过一步法原位合成Cu-SSZ-13分子筛催化剂,考察了结晶反应时间对NH3选择性催化还原(NH3-SCR)催化性能的影响,利用H2程序升温还原(H2-TPR)、X射线衍射(XRD)、电子顺磁共振光谱(EPR)和X射线电子能谱(XPS)等分析手段表征催化剂。结果表明,结晶时间不同会影响到Cu-SSZ-13分子筛中活性Cu物种的含量和分布,结晶时间为4 d时Cu-SSZ-13分子筛的NH3-SCR催化性能最佳。高温水热条件下,Cu-SSZ-13分子筛中不稳定的Cu~(2+)A物种会发生迁移而形成相对稳定的Cu~(2+)B物种;Cu~(2+)物种发生团聚而造成分子筛结构破坏,部分Cu~(2+)物种也因分子筛骨架坍塌而被包埋,这是导致催化活性下降的主要原因。     

负载型CuO—ZnO／γ—Al2O3催化剂抗硫中毒性能的研究

采用XPS、TPR法证明浸渍法制备的CuO-ZnO/Al_2O_3催化剂中的CuO、ZnO和γ-Al_2O_3之间存在强相互作用,Cu量≤7.0wt%,Zn量≤11Wt%时,CuO和ZnO以单分子层分散在γ-Al_2O_3上.催化剂表面Cu和Zn实际含量的比值远小于配制时的比值(Cu/Zn=2),表明ZnO比CuO优先分布在表面.因ZnO比CuO更易和S作用生成ZnS,ZnO在表面的大量存在减少了Cu被S中毒的机率;另外CuO单层分散在Al_2O_3上,还原后生成的Cu~0,由于γ-Al_2O_3的拉电子作用使其处于缺电子状态(CU~(?+)),加上催化剂表面可能有部分CuO和Al_2O_3形成尖晶石,使一部分Cu以Cu~(n+)存在,Cu~((?)+)或Cu~(n+)对S的吸附弱.以上两个原因使负载型铜催化剂具有良好的抗硫中毒性能.     

NH_4~+交换度对CuY催化剂上甲醇氧化羰基化反应性能的影响（英文）

碳酸二甲酯(DMC)是一种应用极其广泛的绿色化工产品,其中经济、绿色的甲醇氧化羰基化合成DMC工艺极具工业前景,而Y分子筛负载铜(CuY)是有效催化剂之一.众所周知,CuY催化剂上的Cu~(+)是催化活性中心.Cu~(+)催化活性中心的引入方式用两种:(1)CuCl直接与HY分子筛固相离子交换;(2)Cu~(2+)与NaY分子筛溶液离子交换,然后Cu~(2+)自还原生成活性中心Cu~(+).在无溶剂条件下制备CuY催化剂时,载体HY分子筛中的可交换位H+量是决定催化剂CuY氧化羰基化催化性能的关键因素.文献通过以不同硅铝比的HY分子筛为载体制备的催化剂CuY,研究铜离子可交换位H+量对氧化羰基化的影响,然而,硅铝比的不同也直接影响了分子筛骨架的组成、Si–O–Al的键角、甚至影响了Al~(3+)的分散度,这些因素都直接影响了CuY催化剂活性.因此,研究NaNH_4Y分子筛载体中的可交换位(NH_4~+)的量与CuY催化剂活性间的关系具有非常重要的意义.本文将NaY分子筛与不同浓度的NH_4NO_3溶液进行离子交换,制得具有不同NH+4交换度的NaNH_4Y分子筛,以其为载体,以具有易升华、易分解性质的乙酰丙酮铜Cu(acac)2为铜源,在无溶剂条件下,高温热处理二者固相混合物,NaNH_4Y分子筛中的NH_4~+与Cu(acac)_2中的Cu~(2+)发生了离子交换,Cu~(2+)进一步发生自还原生成活性中心Cu~(+),成功地制备了完全无氯的CuY催化剂,应用于催化常压甲醇氧化羰基化合成DMC过程,研究NaNH_4Y分子筛中的铜离子可交换位NH_4~+与催化剂CuY催化性能间的关系.通过各种表征及对CuY催化剂在甲醇氧化羰基化过程中催化活性分析发现,Y分子筛经过NH_4NO_3溶液离子交换及催化剂的制备过程,其八面沸石结构和孔道保持良好.以未经过离子交换的NaY负载的CuY催化剂上的铜物种完全以CuO形式存在,且没有催化活性.随着NH_4~+交换度增加,CuY催化剂表面CuO含量逐渐降低,而活性中心Cu~(+)含量逐渐增加,且其催化活性也随之增加.当NH_4~+交换度趋于极限值时,CuY催化剂中Cu~(+)含量达最大,其催化活性也达最佳,DMC的时空收率和选择性分别为267.3mg/(g·h)和68.5%,甲醇转化率为6.9%.因此,无溶剂条件下,以NaNH_4Y分子筛为载体,Cu(acac)_2为铜源,制备完全无氯CuY催化剂时,NH_4~+是形成Cu~(+)活性中心的必须条件,且NH_4~+交换度直接影响催化剂CuY的催化活性.     

改性Cu-Mn/SAPO-34催化剂在SCR脱硝反应中的特性研究

采用浸渍法制备了系列铜锰复合氧化物分子筛催化剂(Cu-Mn/SAPO-34),在固定床反应器上考察不同Cu/Mn质量比对分子筛催化剂选择催化还原NO的影响,利用XRD、NH_3-TPD、H_2-TPR、XPS等手段对催化剂进行了表征分析。结果表明,双金属改性的Cu-Mn/SAPO-34催化剂在NH_3-SCR反应中表现出较为优异的催化活性,具有较宽的活性温度窗口。当Cu/Mn质量比为1∶4时,催化剂具有最宽的活性温度窗口,NO_x转化率在250℃已达到85.39%,在300-400℃转化率均达到96%以上,450℃时仍能达到90%。铜和锰物种高度分散于催化剂表面,未改变SAPO-34的晶体结构,且构成协同作用。Cu-Mn共同负载促进了Cu~(2+)向Cu~+的转变,增加了高价态Mn~(4+)和Mn~(3+)的比例,有利于提高低温活性,促进催化反应的进行。Cu-Mn/SAPO-34/1∶4具备丰富的酸性位、良好的氧化还原性能和抗SO_2/H_2O性能,该配比有助于催化剂的催化活性和稳定性的提高。     

TPAOH处理制备的微介孔催化剂物化性质与噻吩烷基化性能研究

采用不同浓度的TPAOH溶液处理不同SiO_2/Al_2O_3物质的量比的HZSM-5分子筛,制备了微孔-介孔多级孔HZSM-5催化剂。结果表明,采用不同浓度的TPAOH溶液处理不同SiO_2/Al_2O_3物质的量比的HZSM-5分子筛能够脱出HZSM-5分子筛的骨架硅而产生介孔,介孔孔径随TPAOH溶液浓度和SiO_2/Al_2O_3物质的量比的增大而增大;TPAOH溶液处理能够调变HZSM-5催化剂的酸性。采用不同浓度的TPAOH溶液处理SiO_2/Al_2O_3物质的量比分别为50、80和150的HZSM-5分子筛,其中,SiO_2/Al_2O_3物质的量比为50的HZSM-5弱中酸酸强度、相对酸量、B酸和L酸含量明显高于SiO_2/Al_2O_3物质的量比为80和150的HZSM-5分子筛。经不同浓度的TPAOH溶液处理后SiO_2/Al_2O_3物质的量比为50的HZSM-5催化剂具有最佳的噻吩烷基化反应性能。     

柴油机尾气中的碱性无机污染物引起Cu-SAPO-18脱硝催化剂的化学失活

选择性催化还原NO_x (NH_3-SCR)已是柴油机尾气处理系统中有效的NO_x减排技术.铜基分子筛催化剂作为潜在的NH_3-SCR催化剂已被广泛研究,其中具有AEI结构的Cu-SAPO-18分子筛表现出优异的脱硝活性和水热稳定性,成为柴油机尾气后处理系统潜在的替代品.然而在实际的后处理应用中,生物柴油污染物、发动机润滑剂和燃料添加剂中的一些无机组分(K, Na, S, P, Ca和Mg等)可逐渐聚集在催化剂表面,导致催化剂孔道堵塞和活性位点丢失,最终导致SCR催化剂失活.由于碱金属和碱土金属在柴油衍生物中含量较高,因而其对SCR催化剂的影响引起了人们更多的关注.本文采用浸渍法制备了掺杂不同含量碱性无机污染物(K, Na, Ca和Mg)的Cu-SAPO-18催化剂,以阐明这些污染物对Cu-SAPO-18结构、酸性位点和铜物种的影响.XRD和氮吸附实验结果表明,低含量污染物的掺入造成催化剂孔道堵塞和比表面积下降,而高含量污染物引入导致催化剂部分结构被破坏,其中高含量Na的引入造成催化剂结构破坏最为严重.H_2-TPR和EPR结果表明,污染物引入Cu-SAPO-18后,催化剂的Cu~(2+)数目减少,这是由于Cu~(2+)被K~+, Na~+, Ca~(2+)和Mg~(2+)取代造成的.被取代的Cu~(2+)由于无法位于离子交换位点上会在煅烧过程中转变成CuO和CuAl_2O_4, CuO的产生会造成催化剂孔道堵塞甚至部分骨架结构坍塌.另外,NH_3-TPD结果表明,与新鲜催化剂相比,被污染的Cu-SAPO-18催化剂总酸性位点减少,这是由于H~+和Cu~(2+)被K~+, Na~+, Ca~(2+)和Mg~(2+)取代造成Br?nsted酸和Lewis酸减少造成的.催化剂比表面积的降低、Cu~(2+)数目以及酸含量的减少最终造成催化剂失活,且催化剂失活程度随无机污染物含量的增加而增大.但不同无机组分造成催化剂的失活程度不同,其中K, Na, Ca和Mg造成Cu-SAPO-18催化剂失活程度为K Na Ca Mg.此外, K, Na, Ca和Mg造成Cu-SAPO-18催化剂比表面积、Cu~(2+)含量以及酸含量的减少程度分别为Na K Ca Mg, Na K Mg Ca和K Na Ca Mg.其中酸含量下降程度与催化剂失活程度一致,表明在某种程度上,酸含量对催化剂NH_3-SCR活性的影响高于催化剂结构和Cu~(2+)对活性的影响.最后,我们还通过NH3-SCR动力学测试研究了K, Na, Ca和Mg对Cu-SAPO-18催化NH_3-SCR反应机理的影响,结果显示新鲜催化剂和被污染催化剂具有相近的活化能,表明无机污染物对Cu-SAPO-18催化NH3-SCR反应机理没有影响.     

无有机胺体系中高硅ZSM-5沸石的一步合成

在无有机胺模板剂和不加晶种体系中,采用较低晶化温度(130℃),在水热体系中一步合成了形貌均一的板块状高硅ZSM-5沸石(n_(SiO_2)/n_(Al_2O_390)。系统地考察了合成体系中原料的物质的量之比对合成ZSM-5沸石的影响。通过X射线衍射(XRD),傅里叶红外光谱(FT-IR),扫描电镜(SEM),低温氮气吸附/脱附和固体核磁共振(~(29)Si MAS NMR)等技术手段对合成的ZSM-5沸石进行了物化表征。结果表明,当原料的物质的量之比n_(C_2H_5OH)/n_(SiO_2)=2.8、n_(Na_2O)/n_(SiO_2)=0.14和n_(SiO_2)/n_(Al_2O_3)=150时,可合成具有高结晶度的ZSM-5纯相沸石。比表面积和微孔孔容分别为409 m~2·g~(-1)和0.14 cm~3·g~(-1),其骨架n_(SiO_2)/n_(Al_2O_3)达到96.4。     

NH3-SCR反应过程中NH3和NOx在Cu/SAPO-34分子筛催化剂上的吸附特性和作用

通过离子交换法制得Cu/SAPO-34菱沸石分子筛催化剂,同时研究了NH3和NOx(NO和NO2)在该催化剂上的吸附位、吸附强度、吸附量和吸附速率,得到了不同反应气氛在Cu/SAPO-34上的吸附性能及其在NH3选择性催化还原(NH3-SCR)反应中的作用.研究采用瞬态实验、程序升温脱附(TPD)和漫反射傅里叶变换红外光谱(DRIFTS)等方法进行表征实验.瞬态实验结果表明NH3是吸附性气体.程序升温脱附实验和红外漫反射实验结果表明NH3可以吸附在布朗斯特和路易斯酸性位上形成不同的NH3物种,它们显示不同的SCR活性.NH3在Cu2+上的吸附速率最快,且键强最强.NOx可以氧化并以硝酸盐/亚硝酸盐的形式吸附在CU物种上.最后,本文讨论了NH3选择性催化还原反应过程中在Cu物种上的中间物种并推测反应机理.     

Simultaneous determination of phenolic acids and flavonoids in rice using solid-phase extraction and RP-HPLC with photodiode array detection

An analytical method based on an optimized solid-phase extraction procedure and followed by high-performance liquid chromatography (HPLC) separation with diode array detection was developed and validated for the simultaneous determination of phenolic acids (gallic, protocatechuic, 4-hydroxy-benzoic, vanillic, caffeic, syringic, p-coumaric, ferulic, sinapic, and cinnamic acids), flavanols (catechin and epicatechin), flavonols (myricetin, quercetin, kaempferol, quercetin-3-O-glucoside, hyperoside, and rutin), flavones (luteolin and apigenin) and flavanones (naringenin and hesperidin) in rice flour (Oryza sativa L.). Chromatographic separation was carried out on a PerfectSil Target ODS-3 (250 mm × 4.6 mm, 3 μm) column at temperature 25°C using a mobile phase, consisting of 0.5% (v/v) acetic acid in water, methanol, and acetonitrile at a flow rate 1 mL min(-1) , under gradient elution conditions. Application of optimum extraction conditions, elaborated on both Lichrolut C(18) and Oasis HLB cartridges, have led to extraction of phenolic acids and flavonoids from rice flour with mean recoveries 84.3-113.0%. The developed method was validated in terms of linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 5) and inter-day precision (n = 4) revealed relative standard deviation (RSD) <13%. The optimized method was successfully applied to the analysis of phenolic acids and flavonoids in pigmented (red and black rice) and non-pigmented rice (brown rice) samples.     

Changes in the proteome of extracellular vesicles shed by rat liver after subtoxic exposure to acetaminophen

To identify changes in extracellular vesicles (EVs) secreted by the liver following drug-induced liver injury (DILI), rats were treated with a subtoxic dose (500 mg/kg) of the analgesic drug, acetaminophen (APAP). EVs were collected by liver perfusion of sham and APAP-treated rats. Changes in EVs morphology were examined by transmission electron microscopic analysis of negatively stained vesicles. Results from morphometric analysis of EVs revealed striking differences in their size and distribution. Proteome composition of EVs collected by liver perfusion was determined by mass spectrometry using methods of sample preparation that enabled better detection of both highly hydrophobic proteins and proteins with complex post-translational modifications. The collection of EVs after liver perfusion is an approach that enables the isolation of EVs shed not only by isolated hepatocytes, but also by the entire complement of hepatic cells. EVs derived after DILI had a lower content of alpha-1-macroglobulin, ferritin, and members of cytochrome 450 family. Fibronectin, aminopeptidase N, metalloreductase STEAP4, integrin beta, and members of the annexin family were detected only in APAP-treated samples of EVs. These results show that the present approach can provide valuable insights into the response of the liver following drug-induced liver injury.     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of Nox by ammonia 2. TPD test of commercial V/W/Ti, V/Al, Pd/V/Al catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of commercial binary V/Al and ternary Pd/V/Al, V(0.65 wt.%) /W(6.73 wt.%) /Ti and V(1.8 wt.%) /W(7.3 wt.%) /Ti de-NO_x catalysts has been investigated by temperature-programmed desorption (TPD) method. The ability of the commercial catalysts to adsorb ammonia in the most stable surface species was shown to correlate well with their suppression of the NH₃ oxidation.     

乙酸镍吡啶配合物催化的分子氧氧化反应研究

Ni(OAc)2结合吡啶和叔丁基过氧化氢(TBHP)实现了苄基C-H与苄基醇类化合物在温和条件下(80～90℃,O21 atm)的选择性催化分子氧氧化反应.研究了过氧化物添加剂,配体,溶剂和温度的影响,得到了优化的反应条件.在苄基C-H的氧化中显示了很高的酮/醇选择性.用ESR法进行了Ni(III)的检测,证实了反应机理.竞争实验说明羰基化合物的生成不是因为醇继续氧化.酮可被解释为过氧化氢中间体受金属催化分解的产物.     

乳腺癌代谢物组模式特征发现方法及HPLC/M S/M S分析

提出一种基于单独最优特征组合和BP神经网络的代谢物组模式特征发现方法,并用其寻找到尿样中与乳腺癌最为相关的4种核苷,组成一组特异性检测参数.经HPLC/MS/MS联用法鉴定,它们是乳清酸核苷、1-甲酰化腺苷、S-腺苷-L-蛋氨酸及N²-甲酰化鸟苷.将这4种核苷作为输入变量,用BP神经分类网络建立乳腺癌诊断模型.留一法交叉验证和独立验证结果表明,该模型预测准确率达到90%以上.     

Elucidation of the absolute configuration of rhizopine by chiral supercritical fluid chromatography and vibrational circular dichroism

The absolute configuration of rhizopine, an opine‐like natural product present in nitrogen‐fixing nodules of alfalfa infected by rhizobia, is elucidated using a combination of state‐of‐the‐art analytical and semi‐preparative supercritical fluid chromatography and vibrational circular dichroism spectroscopy. A synthetic peracetylated racemate was fractionated into its enantiomers and subjected to absolute configuration analysis revealing that natural rhizopine exists as a single enantiomer. The stereochemistry of non‐derivatized natural rhizopine corresponds to (1R,2S,3R,4R,5S,6R)‐4‐amino‐6‐methoxycyclohexane‐1,2,3,5‐tetraol.     

Paternal genetic structure of Kyrgyz ethnic group in China revealed by high-resolution Y-chromosome STRs and SNPs

Kyrgyz ethnic group is one of the nomads in China, with the majority in Xinjiang and a small part of them living in Heilongjiang province. Historically, they have went through five migrations westward due to the wars. The name “Kyrgyz” means 40 tribes, originating from the primary groups of Kyrgyz. However, it is a largely understudied population, especially from the Y chromosome. In this study, we used a previously validated high-resolution Y-chromosome single nucleotide polymorphisms (Y-SNPs) and short tandem repeats (Y-STRs) system to study Kyrgyz ethnic group. A total of 314 male samples of Kyrgyz ethnic group were genotyped by 173 Y-SNPs and 27 Y-STRs. After data analysis, the results unveiled that Kyrgyz ethnic group was a population with high percentage of both haplogroup C2a1a3a1d∼-F10091 (91/134) and R1a1a1b2a2-Z2124 (109/134), which has never been reported. This implied that Kyrgyz ethnic group might have gone through bottleneck effects twice, with these two main lineages left. Mismatch analysis indicated that the biggest mismatch number in haplogroup C2a1a3a1d∼-F10091 was 10, while that of haplogroup R1a1a1b2a2-Z2124 was 20. This huge difference reflected the different substructure in two lineages, suggesting that haplogroup C2a1a3a1d∼-F10091 might have the least admixture compared to the other two lineages. After admixture modelling with other datasets, the conclusion could be drawn that Kyrgyz ethnic group had great genetic affinity with Punjabi from Lahore, Pakistan, which supported that Kyrgyz ethnic group in China was close to central Asian.     

Analysis of alendronate in human urine and plasma by magnetic solid-phase extraction and capillary electrophoresis with fluorescence detection

A simple, rapid and sensitive CE-fluorescence (FL) detection method for the analysis of alendronate (ALEN), a bisphosphonate drug, has been developed. Using a buffer solution of 20 mM sodium phosphate (pH 10.0) and a voltage of 24 kV, separation of ALEN in a 55-cm length (35-cm effective length) capillary was achieved in 5 min. FL detection of ALEN was performed via pre-column derivatization with 2,3-naphthalene dicarbox-yaldehyde (NDA). Linear correlation (r=0.9981, n=6) between FL intensity and analyte concentration was obtained in the range of 7-200 ng/mL ALEN. The developed CE-FL method was applied to the analysis of ALEN in human urine and plasma samples. In order to eliminate the interfering matrix components, SPE using magnetic Fe(3) O(4) @Al(2) O(3) nanoparticles as solid sorbents was employed to clean the biological fluids before CE-FL analysis. The linear ranges of ALEN in urine and plasma were 5-100 ng/mL (r = 0.9982, n = 7) and 5-70 ng/mL (r = 0.9954, n = 7), respectively. The LOD and LOQ in both urine and plasma samples were 1.5 and 5 ng/mL ALEN, respectively. Total analysis time including sample pre-treatment and CE separation was less than 1.5 h.     

Simultaneous liquid-liquid extraction of dibenzyl disulfide, 2,6-di-tert-butyl-p-cresol, and 1,2,3-benzotriazole from power transformer oil prior to GC and HPLC determination

2,6-Di-tert-butyl-p-cresol (DBPC), dibenzyl disulfide (DBDS), and 1,2,3-benzotriazole (BTA) are additives that may be found concomitantly in the oil matrix of power transformer. DBPC and DBDS act as antioxidants while, BTA is a corrosion inhibitor that protects copper conductors inside the transformer unit from corrosion. A powerful analytical method is, therefore, required to determine these additives at trace levels in the transformer oil. This work describes a unique single liquid-liquid extraction pretreatment step prior to the determination of the components by gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. The optimum volume ratio used in the pretreatment step was determined as 5:2:5 for mineral oil/n-hexane/acetonitrile, respectively. Relatively, the method is simple and quick with a minimal use of solvents. Analytical results indicate that the method is relatively sensitive, accurate, and precise for each of the three components in fresh and used mineral oil. The calibration curves for the three components demonstrate a significant increase in sensitivities. Detection limits found were, 100 mg L(-1) (0.01% w/v), 0.80 mg L(-1) , and 2.04 mg L(-1) for DBPC, DBDS, and BTA, respectively. The Student's t values determined at 95% confidence level indicate that there is no significant difference between the experimental means obtained by this method and the standard method for each component.