离子交换净化-气相色谱法测定洋葱及洋葱调味汁中二嗪磷农药残留

依据二嗪磷农药结构的特点,建立了离子交换净化法测定洋葱及洋葱调味汁中二嗪磷农药残留的前处理方法。样品用乙酸乙酯涡旋振荡提取,提取液经浓缩复溶后过阳离子交换柱净化,所得净化液经浓缩定容后供气相色谱仪分析。采用火焰光度检测器测试,外标法定量。方法在最优条件下进行测试,二嗪磷的定量下限(S/N≥10)为0.01 mg/kg,在加标水平为0.01,0.05,0.10,0.20 mg/kg时,回收率为80.5%~91.2%,相对标准偏差为3.2%~9.6%。方法适用于洋葱及洋葱调味汁中二嗪磷农药残留的测定。     

气相色谱法测定穿心莲及其土壤中高效氟吡甲禾灵残留

建立了一种简单快速测定穿心莲及其土壤中高效氟吡甲禾灵残留的气相色谱-电子捕获检测(GC-ECD)方法。穿心莲及土壤样品用乙腈提取,土壤提取液直接浓缩至干;穿心莲提取液浓缩后经弗罗里硅土-活性炭(质量比4∶6)柱净化,乙酸乙酯淋洗后浓缩至近干,甲醇定容,GC-ECD检测。结果表明,高效氟吡甲禾灵的最小检出量为0.007ng,在穿心莲及土壤中的最低检测浓度为0.01mg/kg。穿心莲及土壤中高效氟吡甲禾灵的回收率在78.48%～106.50%之间,相对标准偏差(RSD)为1.39%～6.54%。     

气相色谱-火焰光度法测定土壤中有机磷农药残留

建立了气相色谱-火焰光度(GC-FPD)分析土壤中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷等9种有机磷农药残留量的方法。样品用丙酮-二氯甲烷(1:3)提取,浓缩、定容后用Hp-5MS(30m×0.25 mm×0.25μm)毛细管柱分离,FPD检测器检测。方法回收率在68.71%～110.39%之间;RSD在5.5%～11%之间;检出限在0.397～1.60μg/mL之间,方法可用于环境土壤样品中有机磷农药残留的测定。     

苹果与土壤中虱螨脲残留的超高效液相色谱快速分析方法研究

建立了简便、快速、灵敏的测定苹果和土壤中虱螨脲残留的超高效液相色谱分析方法。样品采用乙腈提取,提取液经盐析后无需净化,将上清液浓缩复溶,过膜后直接上机测试。试样采用BEH C18(50.0 mm×2.1 mm,1.7μm)色谱柱分离,甲醇-水(60∶40)为流动相等度洗脱后,紫外检测器检测,检测波长为255 nm。结果表明,虱螨脲在0.025~2.5 mg/L浓度范围内线性关系良好,相关系数为0.999 7。在0.05~0.5 mg/kg加标浓度范围内的平均回收率为84.5%~98.7%,相对标准偏差(RSD)为0.7%~6.1%,方法的检出限为0.01 mg/kg。     

超声波提取-气相色谱法测定土壤中21种酚类化合物

建立了超声波提取-气相色谱法同时测定土壤中21种酚类化合物的分析方法。用二氯甲烷和正己烷混合溶剂提取土壤中的酚类化合物,提取液经碱性水溶液分配净化,去除非酸性有机杂质,再酸化萃取酚类化合物,浓缩后采用气相色谱-氢火焰离子化检测器进行检测,外标法定量。以10 g土壤样品计,酚类化合物的检出限为0.01~0.06 mg/kg。实际样品添加回收试验的回收率为62.9%~111.4%,相对标准偏差为4.3%~24.0%(n=6),准确度和精密度均较好。结果表明:该法操作方便,净化效果好,可用于土壤中多种酚类化合物的测定。     

气相色谱法同时测定蔬菜中24种有机磷农药残留

建立了蔬菜中24种有机磷类农药残留气相色谱同时分析的方法。样品用含0.1%乙酸的乙腈提取,净化采用分散固相萃取的方式:在提取液中加入C18(ODS)、石墨炭黑、PSA等吸附剂粉末进行净化,采用DB-1701(30 m×0.32 mm×0.25μm)毛细管柱分离,FPD(P)检测。24种农药的质量分数在0.002~0.05 mg/kg时,回收率在80.1%~102.1%之间、RDS为1.4%~5.1%。各农药的检测限为:三硫磷、三唑磷为0.004 mg/kg、苯硫磷为0.01 mg/kg,其它21种为0.002 mg/kg。     

分散固相萃取-气相色谱法测定对虾中12种有机磷农药残留

建立了分散固相萃取-气相色谱测定对虾中12种有机磷农药残留的分析方法。样品经V(冰乙酸):V(乙腈)=1:99溶液提取,采用乙二胺-N-丙基硅烷(PSA)、C18与石墨炭黑(GCB)为吸附剂进行分散固相萃取净化。以DB-17毛细管色谱柱分离,GC-FPD(P)检测。方法在0.01~0.50μg/mL范围内线性关系良好,相关系数(r2)均不低于0.9971,12种有机磷农药的方法检出限均为0.01 mg/kg。在0.01~0.10 mg/kg的添加水平下,平均加标回收率为80.7%~101.2%,相对标准偏差为3.7%~7.6%。     

3种方法测定植物源性农产品中霉灵残留量

建立了测定大豆、糙米、黄瓜、甜菜等6种植物源性农产品中(噁)霉灵残留的气相色谱-火焰光度法(GC-FPD)、气相色谱-氮磷检测法(GC-NPD)和液相色谱-串联质谱法(LC-MS/MS).GC-FPD法采用丙酮-正己烷提取样品,O,O-二甲基硫代磷酰氯衍生,GC-FPD分析,外标法定量;GC-NPD法采用丙酮-正己烷提取样品,十八烷基键合硅胶(C18)净化,GC-NPD分析,外标法定量;LC-MS/MS法,样品采用乙腈提取,石墨化碳黑(GCB)净化,LC-MS/MS分析,基质匹配外标法定量.结果表明,(噁)霉灵的响应值与其浓度间呈良好的线性关系,3种方法的相关系数均大于0.998.在3个加标浓度下,GC-FPD法中(噁)霉灵的日间平均回收率为82%~96%,日间相对标准偏差(RSD)为3.4%~12.1%,方法的定量下限为0.25 mg/kg (甜菜为0.05 mg/kg);GC-NPD法的日间平均回收率为81%~103%,日间RSD为4.1%~14.3%,定量下限为0.25 mg/kg (甜菜为0.05 mg/kg);LC-MS/MS法的日间平均回收率为74%~110%,日间RSD为2.5%~10.7%,定量下限为0.05 mg/kg.3种方法均具有良好的准确性和稳定性,可满足(噁)霉灵残留分析的要求.     

气相色谱法测定大豆中24种有机磷农药的残留量

提出了用气相色谱-火焰光度检测器(GC-FPD)测定大豆中24种有机磷农药残留量的方法。采用乙腈匀质提取大豆试样中残留的有机磷农药,提取液依次经C18固相萃取柱、活性炭固相萃取柱和硅胶固相萃取柱净化。淋出液用DB-1701石英毛细管柱进行分离,GC-FPD检测,外标法定量。方法的检出限在0.005~0.010 mg.kg-1之间。所测24种农药的标准加入回收率在60.7%~115.6%之间,相对标准偏差(n=6)为1.7%~11.1%。     

3种方法测定植物源性农产品中噁霉灵残留量

建立了测定大豆、糙米、黄瓜、甜菜等6种植物源性农产品中噁霉灵残留的气相色谱-火焰光度法(GC-FPD)、气相色谱-氮磷检测法(GC-NPD)和液相色谱-串联质谱法(LC-MS/MS)。GC-FPD法采用丙酮-正己烷提取样品,O,O-二甲基硫代磷酰氯衍生,GC-FPD分析,外标法定量;GC-NPD法采用丙酮-正己烷提取样品,十八烷基键合硅胶(C18)净化,GC-NPD分析,外标法定量;LC-MS/MS法,样品采用乙腈提取,石墨化碳黑(GCB)净化,LC-MS/MS分析,基质匹配外标法定量。结果表明,噁霉灵的响应值与其浓度间呈良好的线性关系,3种方法的相关系数均大于0.998。在3个加标浓度下,GC-FPD法中噁霉灵的日间平均回收率为82%~96%,日间相对标准偏差(RSD)为3.4%~12.1%,方法的定量下限为0.25 mg/kg(甜菜为0.05 mg/kg);GC-NPD法的日间平均回收率为81%~103%,日间RSD为4.1%~14.3%,定量下限为0.25 mg/kg(甜菜为0.05 mg/kg);LC-MS/MS法的日间平均回收率为74%~110%,日间RSD为2.5%~10.7%,定量下限为0.05 mg/kg。3种方法均具有良好的准确性和稳定性,可满足噁霉灵残留分析的要求。     

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%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.