在线固相萃取-离子色谱法测定4种芳环磺酸盐中的硫酸根离子

建立一种在线固相萃取-离子色谱测定4种芳环磺酸盐中硫酸根离子含量的新方法。将自装填的多孔石墨化碳固相萃取柱应用于离子色谱系统,对样品进行在线前处理。样品经过多孔石墨化碳固相萃取柱基体消除后进入收集环,通过阀切换方式使待测硫酸根离子转入阴离子分析柱和检测系统。固相萃取流路用1.5 mmol/L碳酸钠以0.8 mL/min的流速对基体在线富集,进样量为20μL,分析柱为SH-AC-3(250 mm×4.0 mm)+SH-AG-3(50 mm×4.0 mm)色谱柱,柱温为35℃,在6 mmol/L碳酸钠-4 mmol/L碳酸氢钠条件下等度洗脱,流速为0.8 mL/min。结果表明:硫酸根离子在0.50~20.00 mg/L范围内呈良好的线性关系,线性相关系数为0.998 3,保留时间、峰高和峰面积的相对标准偏差均在0.28%~2.86%之间,方法检出限为0.010 6 mg/L,回收率为91.01%~109.3%,具有良好的线性关系和重复性。整个在线分析过程在25 min之内完成。该方法进样量少、快速、高效。     

全自动在线固相萃取-二维高效液相色谱与质谱联用测定辣椒油中苏丹红

建立了全自动在线固相萃取-二维高效液相色谱与质谱联用快速测定辣椒油中的苏丹红Ⅰ,Ⅱ,Ⅲ,Ⅳ的方法。样品经乙腈和二氯甲烷萃取后,在一维色谱柱(Acclaim PAⅡ,150 mm×3.0 mm×3μm)上分离出苏丹红,通过阀的分段切换,依次富集在SPE柱(Acclaim 120 C18,10 mm×4.6 mm×5μm)上,在线完成净化和萃取富集;再通过阀切换将它们转移至二维色谱流路,在Acclaim 120 C18色谱柱(100 mm×2.1 mm×2.2μm)上分离检测。一维色谱以水-乙腈-甲醇/四氢呋喃(1∶1,V/V)为流动相,进样体积20μL,0.6 mL/min流速梯度洗脱和紫外-可见检测器(λ=254 nm)监测分离状况;二维色谱以水-乙腈-甲酸/乙腈(1∶1000,V/V)为流动相,0.3 mL/min流速梯度洗脱,采用单四极质谱仪,选择离子方式检测。整个分析流程27 min即可完成。4种苏丹红的保留时间的相对标准偏差均小于0.1%,色谱峰面积的相对标准偏差均小于2%(n=7);在0.6～60μg/L范围内峰面积与进样质量浓度的线性相关系数均大于0.9958;加标回收率为50%～97%;方法检出限均小于0.2μg/L(S/N=3)。测定结果令人满意。     

固相萃取-气相色谱-质谱法测定地下水中多环芳烃

提出了固相萃取-气相色谱-质谱法测定地下水中16种多环芳烃的方法。样品经ENVIC18固相萃取柱富集,依次用丙酮5 mL和二氯甲烷10 mL将16种多环芳烃从固相萃取柱上洗脱,用K-D浓缩器浓缩后,供气相色谱-质谱仪测定。纯水或自来水经固相萃取处理后,再用于配制标准溶液并绘制标准曲线。16种多环芳烃的检出限(3S/N)均小于2.0 ng.L-1。用该法分析地下水样品,所得结果的相对标准偏差(n=7)小于14.0%,加标回收率在84.3%~112.3%之间。     

pH侬赖型脂肪酸辅助的分散液-液微萃取与高效液相色谱仪联用测定水样中3种多环芳烃

建立了pH依赖型脂肪酸辅助的分散液-液微萃取与高效液相色谱联用测定水中菲、芘、苊3种多环芳烃(PAHs)的新方法。对影响前处理方法的因素进行了考察,在55μL正庚酸、50μL 28%(质量分数)浓氨水、500μL 98%(质量分数)浓硫酸、离心时间3 min的萃取条件下,采用Diamonsil C_(18)柱(150 mm×4.6 mm,5μm)分离,乙腈-水等度洗脱的方式测定了自来水、井水和海水样品中的3种多环芳烃。结果显示,3种多环芳烃在20～500μg/L范围内具有良好的线性关系,相关系数不小于0.999 3,3种目标化合物的检出限为9.18～13.11μg/L。实际样品中3种多环芳烃在3个浓度水平的加标回收率为87.9%～110%,RSD均不大于3.0%。该方法将脂肪酸作为萃取剂,与HPLC联用实现了多环芳烃的富集与检测,为环境水样中多环芳烃的检测提供了新的前处理方法。方法简便、快速,实验过程仅需6 min即可实现水样中多环芳烃的定量测定。     

在线固相萃取-液相色谱法直接测定水中超痕量多环芳烃

建立了在线固相萃取-液相色谱直接测定水体中16种超痕量多环芳烃（PAHs）的方法。水样经高速离心后，加入适量甲醇，配制成40%（体积分数）甲醇水溶液，直接进样2 mL至在线固相萃取流路，进行萃取富集，再通过阀切换将洗脱的PAHs转移至分析流路进行分离检测。16种PAHs在各自范围内线性关系良好，相关系数均大于0.996；方法的检出限为0.14~12.50 ng/L，其中苯并[a]芘（B（a）P）的检出限为0.38 ng/L。实际水样在10、40和200 ng/L加标水平下的加标回收率为76.1%~134.9%，RSD为0.3%~16.6%。B（a）P在1 ng/L加标水平下的回收率为71.8%~92.7%，RSD为3.9%。结果表明，该方法操作简单，灵敏度高，溶剂消耗量少，可满足水样中PAHs，尤其是B（a）P的超痕量分析要求。     

在线固相萃取/高效液相色谱法检测熏烤鱼及熏烤肉制品中的多环芳烃

基于在线净化富集技术,建立了熏烤鱼和熏烤肉制品中15种欧盟优控多环芳烃的在线固相萃取/高效液相色谱-紫外/荧光(Online-SPE/HPLC-UV/FLD)检测方法。对提取溶剂和流动相进行优化,样品采用乙腈-丙酮(6∶4)匀浆处理,超声提取后,在线固相萃取柱Chrom Spher Pi(80 mm×3 mm)净化富集,反相C18PAH专用柱(250 mm×4.6 mm i.d.,5μm)分离,水、乙腈和异丙醇梯度洗脱,紫外和荧光检测器检测。结果表明,15种多环芳烃在相应的浓度范围内线性良好(r20.999);检出限为0.03~8.33μg/kg;熏烤鱼的回收率为67.4%~107.2%,相对标准偏差(RSD)为0.2%~7.7%;熏烤肉的回收率为71.8%~110.5%,RSD为0.8%~8.9%。经FAPAS质控样品验证,所测化合物种类和浓度范围均满足要求。     

在线固相萃取-高效液相色谱法同时测定人尿液中7种多环芳烃代谢物

采用双三元液相色谱系统结合荧光检测器,建立了在线固相萃取-液相色谱法同时测定人尿液中7种多环芳烃代谢物的方法。目标化合物首先在Turboflow Cyclone固相萃取柱上在线富集浓缩,然后通过六通阀转移至Hypersil Green PAH色谱柱,以乙腈-水为流动相进行梯度洗脱分离,流速1.0 mL/min,柱温30℃,荧光检测器检测,分离周期为20 min。在优化的色谱条件下,5~2000 ng/L或50~20000 ng/L范围内,7种多环芳烃代谢物均呈良好的线性关系(r≥0.999),方法检出限为0.5~15 ng/L,加标回收率为80.7％~110.7％。应用本方法对吸烟和非吸烟人群尿液中7种多环芳烃代谢物的含量进行了测定,吸烟者尿液中的2-羟基萘、1-羟基萘、2-羟基菲、2-羟基芴、4-羟基菲、6-羟基显著高于非吸烟者。     

在线富集/高效液相色谱与电感耦合等离子体质谱联用测定玩具中超痕量可迁移六价铬

采用在线富集/高效液相色谱(HPLC)与电感耦合等离子体质谱(ICP-MS)联用技术,建立了玩具中超痕量可迁移六价铬的测定方法。以10 mmol/L硝酸铵为流动相,样品在Agilent BIO WAX NP5阴离子交换柱(4.6 mm×50 mm,5μm)中富集,再通过阀切换,以75 mmol/L硝酸铵将六价铬洗脱至Dionex AG7阴离子柱(4.0 mm×50 mm,10μm)中分离,最后经ICP-MS进行分析。优化得到在线富集时间为4 min,进样量为900μL,富集流速为0.4 mL/min,洗脱流速为0.6 mL/min。结果显示,六价铬在2～20 ng/L范围内线性良好,检出限为1.93 ng/L,相对标准偏差(RSD)为3.9%。与直接进样相比,浓缩因子约为8.1倍,富集效率约为90%。对欧盟玩具安全指令2009/48/EC规定的3类玩具材料在5、10 ng/L的浓度水平下进行加标回收,回收率为93.4%～111%。     

在线固相萃取-高效液相色谱法同时测定人尿液中的马钱子碱和士的宁

建立了全自动、快速的在线固相萃取-液相色谱技术用于测定人尿液中的马钱子碱和士的宁的方法。样品离心后直接进样,其中被测组分富集于Hyper Sep Retain MCX柱上,尿液中的大分子基质物质不被保留而排出,在线完成萃取和净化富集过程;再通过阀切换使待测物转移至分析流路,在Acclaim C_(18)色谱柱上分离检测。分析时间约13 min。在线固相萃取流路以0.1%H_3PO_4和乙腈为流动相,1 m L/min流速萃取和洗脱;分析流路以乙腈和0.02 mol/L KH_2PO_4为流动相,1 m L/min流速等度洗脱,检测波长为260 nm。马钱子碱在1.25×10~(-6)~2.5×10~(-4)mol/L浓度范围内相关系数r为0.9930,高、中、低浓度的平均回收率分别为85.7%,81.4%和80.9%;士的宁在2.9×10~(-6)~2.9×10~(-4)mol/L浓度范围内相关系数r为0.9993,高、中、低浓度的平均回收率分别为87.1%,82.4%和78.9%。本法可用于测定人尿液中的马钱子碱和士的宁含量。     

分散液液微萃取-气相色谱/质谱法测定水中多环芳烃

用分散液液微萃取-气相色谱/质谱法测定水样中的16种多环芳烃(PAHs)。通过实验确定最佳萃取条件为:20μL四氯化碳作萃取剂,1.0 mL乙腈作分散剂,超声萃取1 min。在优化条件下,多环芳烃的富集倍数达到216～511,方法在0.05～50μg/L范围内呈良好的线性关系,相关系数(R2)在0.9873～0.9983之间,检出限为0.0020～0.14μg/L。相对标准偏差(RSD)在3.82%～12.45%(n=6)之间。该方法成功用于实际水样中痕量多环芳烃的测定。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.