气相色谱化学电离二级质谱法对玉米籽粒中三嗪类除草剂及其代谢物的测定

建立了玉米籽粒中三嗪类除草剂及其代谢物残留的气相色谱化学电离二级质谱(GC-CI MS/MS)分析方法.样品采用盐酸和乙腈混合溶液均质提取,石墨化碳黑(GCB)与中性氧化铝的混合固相萃取柱净化,GC-CI MS/MS基质外标法测定.三嗪类除草剂及代谢物在0.05(0.10) ～4.0 mg/L范围内线性良好,相关系数r在0.993 9以上(脱乙基莠去津溶剂标准曲线的r=0.989 4);在0.050、0.100 μg/g添加水平,平均添加回收率为72% ～108%,相对标准偏差为3.09% ～20.14%,满足进出口及残留监控测定的需要.     

固相萃取-高效液相色谱法同时检测大米中12种磺酰脲类除草剂的残留

建立了固相萃取前处理净化技术-高效液相色谱（HPLC）同时检测大米中12种磺酰脲类除草剂残留的方法。采用ENVITM-18(C18)硅胶柱和ENVI-Carb(GCB)石墨化碳柱对样品进行净化、萃取,采用C8柱,以乙腈和5 mmol/L 冰乙酸混合溶剂为流动相进行梯度洗脱,在240 nm下进行检测。12种磺酰脲类除草剂在0.01~0.50 μg/g添加范围内的回收率为72.2%~106.5%，相对标准偏差为0.6%~6.4%,检出限为0.01~0.02 μg/g。     

高效液相色谱法测定大豆中13种三嗪类除草剂多残留量

建立了同时检测大豆中13种三嗪类除草剂多残留量的反相高效液相色谱(RP-HPLC)方法。样品经乙腈提取,凝胶渗透色谱和中性氧化铝SPE柱净化,然后采用RP-HPLC-二极管阵列检测法测定,外标法定量。对样品前处理和色谱分离条件进行了研究和优化。13种三嗪类除草剂在0.06~5.0 mg/L范围内线性良好,相关系数为0.9998~0.9999。在0.02~1.0μg/g浓度范围内,平均加标回收率在71.9%~101.9%之间,相对标准偏差为2.3%~10.7%。方法简便、快速,净化效果较好,可同时满足进、出口大豆中多种除草剂残留量的检验工作需要。     

改进的QuEchERS-串联质谱法测定莴苣中的124种农药残留

通过比较d-SPE(PSA+GCB)、SPE(NH2-Carb柱)和SPE(GCB/PSA柱)3种前处理方法的净化效果及方法稳定性,选取了GCB/PSA柱固相萃取作为净化方法。样品经前处理后,采用大体积进样,气相色谱-串联质谱测定,内标法定量。124种农药在浓度为0.010～0.200 mg/kg范围内与峰面积呈线性关系,相关系数均大于0.9800,以10倍信噪比计算,定量限在0.1～19.0μg/kg之间。当农药在样品中添加水平为0.040 mg/kg时,124种农药平均回收率(n=5)为80.0～130.7%,RSD为1.1～2.0%。     

高效液相色谱-串联质谱法检测粮谷中三嗪类除草剂残留量

建立了同时检测粮谷中26种三嗪类除草剂残留量的高效液相色谱-串联质谱分析方法.样品经乙腈提取,Oasis MCX固相萃取柱净化,用液相色谱-串联质谱联用仪测定.方法线性范围为1～500 μg/L,26种三嗪类除草剂在此范围内线性良好,相关系数为0.9973～0.9999.在10～100 μg/kg浓度范围内,加标回收率在67.9%～102.3%之间,相对标准偏差为2.0%～9.1%.方法可同时满足进出口粮谷中多种三嗪类除草剂残留的检验需要.     

高效液相色谱串联质谱法对大米中26种三嗪类除草剂多残留的检测

建立了同时检测大米中26种三嗪类除草剂残留量的高效液相色谱串联质谱分析方法.样品经乙腈提取、Oasis HLB固相萃取柱净化,液质联用仪测定.26种三嗪类除草剂在10～1 000 μg/L范围内线性良好,相关系数为0.997 3～0.999 9.在10～100 μg/kg范围内,平均加标回收率为74%～100%,相对标准偏差为2.1%～8.8%.该方法可同时满足进出口大米中多种三嗪类除草剂残留的检验需要.     

高效液相色谱-串联质谱法测定婴幼儿米粉中29种三嗪类除草剂残留

采用改良的QuEChERS方法结合高效液相色谱-串联质谱(HPLC-MS/MS)法建立了婴幼儿米粉中同时测定29种三嗪类除草剂残留量的分析方法。米粉样品经6 mL水浸润后,用乙腈:乙酸乙酯(1:1,V/V)提取,N-丙基乙二胺(PSA)和无水MgSO_4净化,经ZORBAX Eclipse XDB-C_(18)色谱柱分离,采用正离子模式扫描,多反应监测(MRM)模式检测,外标法定量。结果表明29种三嗪类除草剂线性关系良好,相关系数R~2大于0.999,方法的检出限为0.01～0.51μg/kg,定量限在0.04～1.70μg/kg之间。3个加标水平下的平均回收率在71.1%～111.4%之间,相对标准偏差(RSDs) 0.9%～8.8%。该方法适用于婴幼儿米粉中29种三嗪类除草剂残留的同时快速检测。     

复合分子印迹固相萃取-HPLC-MS/MS法测定植物源性食品中多种农药残留

建立了复合分子印迹固相萃取(CMISPE)-高效液相色谱-三重四级杆串联质谱(HPLC-MS/MS)同时检测多种植物源性食品中20种三嗪类和磺酰脲类除草剂残留的分析方法。样品经乙腈提取后,利用液液萃取及复合分子印迹固相萃取小柱净化。液相色谱以乙腈和1%甲酸溶液作为流动相梯度洗脱,C8色谱柱分离,在多反应监测(MRM)正离子电喷雾扫描模式下进行HPLC-MS/MS分析。结果表明:20种除草剂在0.5~20 ng/m L范围内线性关系良好,相关系数均在0.99以上。对玉米样品进行3个水平的加标回收试验(5,10,20μg/kg),20种目标化合物的回收率在62.7%~117.4%之间,相对标准偏差(n=6)为1.7%~13.9%。检出限(S/N≥3)均小于0.63μg/kg,定量限(S/N≥10)均小于2.1μg/kg。方法适用于植物源性食品中20种三嗪类及磺酰脲类农药残留的检测。     

快速基质分散净化-超快速液相色谱-串联质谱法同时测定玉米中22种三嗪类除草剂残留

建立了玉米中扑灭津、莠去津、敌草净、特丁通等22种三嗪类除草剂多残留的分析方法。样品以乙腈为提取剂,经高速匀浆方法提取并浓缩后,以增强型脂质去除净化剂(EMR-Lipid)净化,除去了样品中的脂质,有效地降低了样品中的复杂基质所带来的背景干扰,净化液再经增强型脂质去除萃取剂(EMR-Polish)盐析萃取,以 Kinetex XB-C18柱为分离柱,用乙腈和0.1%甲酸溶液进行梯度洗脱,电喷雾正离子(ESI+)多反应模式监测,超快度液相色谱-串联质谱(UFLC-MS/ MS)测定,基质匹配标准曲线法定量。加标水平为5,10和20μg/ kg 时,22种农药的回收率为72%~105%,相对标准偏差小于15%。22种农药的检出限为0.16~1.8μg/ kg,在1.0~50μg/ L 范围内线性关系良好(r>0.993)。本方法具有快速、准确、灵敏度高等优点,能够准确测定玉米中22种三嗪类除草剂的残留量。     

多壁碳纳米管固相萃取/超高效液相色谱-串联质谱测定茶油中12种氨基甲酸酯类农药

建立了多壁碳纳米管(MWCNTs)为吸附剂的固相萃取净化/超高效液相色谱-串联质谱(UPLC-MS/MS)检测茶油中12种氨基甲酸酯类农药残留的快速分析方法。样品经乙腈超声提取,MWCNTs固相萃取小柱净化,以乙腈进行洗脱,旋蒸浓缩后以0.1%乙酸-乙腈(5∶5,体积比)定容,采用UPLC-MS/MS多反应监测模式(MRM)测定,外标法定量。考察了提取方式、吸附材料类型、洗脱溶剂用量等因素对目标物萃取效率的影响。在优化实验条件下,MWCNTs固相萃取小柱对茶油样品的净化效果理想。12种氨基甲酸酯类农药在0.005～0.1μg/mL范围内线性关系良好,相关系数(r)均不小于0.998 88;在0.01、0.025、0.05 mg/kg加标水平下,12种目标物的平均回收率为78.3%～116%,相对标准偏差为2.6%～12%,方法的定量下限为0.2～3.0μg/kg。     

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%).     

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.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.     

Copper-catalyzed multicomponent reactions of 2-iodoanilines,benzylamines, and elemental sulfur toward 2-arylbenzothiazoles

A relatively cheap copper salt-catalyzed, three-component approach providing 2-arylbenzothiazoles in good to excellent yields from readily available 2-iodoanilines, benzylamines, and sulfur powder is reported. This methodology allows preparation of various classes of 2-arylbenzothiazoles and provides a general, reliable approach.