QuEChERS-超高效液相色谱-串联质谱法同时测定牛奶和奶粉中13种磺胺类药物

建立并优化了同时测定牛奶和奶粉中13种磺胺类药物的Qu ECh ERS-超高效液相色谱-串联质谱的样品前处理及分析方法。样品中的磺胺类药物经乙腈提取和Qu Ech ERS净化粉(无水Mg SO4和C18吸附剂)净化,超高效液相色谱-串联质谱法测定,外标法定量。13种磺胺类药物在不同添加浓度下的回收率范围为81.2%~120.7%,相对标准偏差范围为2.4%~14%,方法检出限为0.03~0.1μg/kg。     

高效液相色谱光化学在线衍生技术在11种磺胺药物残留检测中的应用

建立了磺胺药物残留的高效液相色谱-光化学在线衍生-荧光检测方法,并应用于猪肉的检测。样品经过乙腈提取,色谱柱分离后,通过在线光化学衍生后,用荧光检测器进行直接检测。优化后的色谱条件:Eclipse Plus C18柱(250 mm×4.6 mm,5.0μm),流动相为均含0.2%甲酸的乙腈、甲醇和水梯度洗脱,检测激发波长为248 nm,发射波长为350和412 nm。各种磺胺在各自浓度范围内线性相关系数R2>0.999,回收率在85.7%~101.1%之间,RSD为1.9%~6.6%(n=6),各磺胺的检出限(S/N=3)为0.2~3.0μg/kg,定量限(S/N=10)为0.5~10.0μg/kg。     

多壁碳纳米管作为吸附剂的QuEChERS-气相色谱-四极杆飞行时间质谱快速筛查淡水产品中145种农药残留

建立了基于多壁碳纳米管(MWCNTs)的新型Qu ECh ERS前处理方法,结合气相色谱-高分辨飞行时间质谱对淡水产品中145种农药残留进行快速筛查。样品采用水和乙腈提取,以MWCNTs为净化吸附剂,用Qu ECh ERS方法处理后,采用气相色谱-四极杆飞行时间质谱(GC-QTOF/MS)检测,外标法定量。研究并优化了提取条件、吸附剂种类及用量、GC-QTOF/MS采集速率及质量提取窗口。在最佳实验条件下,145种农药在5~200μg/kg范围内线性关系良好(r20.98),10,20,100μg/kg 3个添加水平下的回收率为69.4%~114.2%,相对标准偏差(RSD,n=6)为2.2%~13.8%,定量下限为1.1~40.0μg/kg。与传统Qu ECh ERS方法相比,所建立的方法快速、准确,净化效果明显,可显著降低基质干扰。     

QuEChERS结合柱净化的超高效液相色谱-串联质谱法测定有机肥中46种抗生素

建立了超高效液相色谱-串联质谱(UPLC-MS/MS)同时测定有机肥中磺胺类、喹诺酮类、大环内酯类46种抗生素的分析方法。样品用乙腈-EDTA缓冲溶液(p H 10.0)提取,盐析后离心分层,乙腈层按Qu ECh ERS法,采用吸附剂净化;缓冲溶液层经HLB柱净化。ACQUITY UPLC BEH C18柱用作色谱分离,以2mmol/L甲酸铵水溶液(含0.1%甲酸)-甲醇为流动相进行梯度洗脱;电喷雾电离源正离子(ESI+)多反应监测(MRM)模式检测,基质外标法定量。46种抗生素在1~200μg/L范围内线性关系良好,相关系数(r2)为0.996 6~0.999 9。在25,100,400μg/kg加标浓度下,3类抗生素的回收率分别为67.8%~95.6%,65.6%~89.4%和66.6%~107.8%,相对标准偏差为0.4%~11.9%;方法检出限(S/N=3)为0.6~4.6μg/kg,定量下限(S/N=10)为2.1~15.4μg/kg。     

改良的QuEChERS样本前处理/高效液相色谱-串联质谱法检测猪肉中四环素类兽药的残留

采用Agilent公司的增强型脂质去除产品Bond Elut EMR-Lipid,建立了针对猪肉中四环素类药物残留的更快更高效的Qu ECh ERS样品前处理方法。样品经酸化乙腈提取,Bond Elut EMR-Lipid Qu ECh ERS净化后,采用HPLC-MS/MS检测,方法检出限可达5.0μg/kg;四环素、金霉素和强力霉素的回收率为75.6%~89.4%,土霉素的回收率为53.4%~61.0%,相对标准偏差均不大于7.7%。     

高效液相色谱法测定鱼肉中残留磺胺类药物

建立了鱼肉中5种磺胺类药物的高效液相色谱测定方法。样品经二氯甲烷提取,正己烷脱脂后经固相萃取柱净化等预处理。用Cloversil C18色谱柱,流动相为乙酸+甲醇+水(1+10+89)进行梯度洗脱,在紫外检测波长265 nm处,检出限可达0.1μg.kg-1,线性范围为0~500μg.L-1,相关系数大于0.999 3,样品加标回收率在78.6%~87.6%之间,测定结果的RSD在3.42%~9.03%之间。     

SPE和QuEChERS前处理方法结合LC-Q-TOF/MS检测苹果和番茄中282种农药残留对比研究

利用液相色谱-四极杆/飞行时间质谱(LC-Q-TOF/MS)对比研究了固相萃取(SPE)和Qu ECh ERS两种前处理方法在282种农药残留检测上的效果。以苹果和番茄为基质,分别从基质效应、回收率、重复性、线性关系、检出限和定量限等方面进行了考察与比较。SPE法和Qu ECh ERS法在苹果中呈现出弱基质效应的农药占比分别为87.2%和57.1%,在番茄中为65.6%和42.2%。与SPE相比,Qu ECh ERS法干扰物较多,基质效应较强;在5.0μg/kg添加水平下(n=5),SPE和Qu ECh ERS在苹果中平均回收率在70%~120%的农药占比分别为99.3%和86.9%,在番茄中为92.9%和87.9%;在5.0μg/kg添加水平下(n=5),SPE和Qu ECh ERS在苹果中重复性相对标准偏差(RSD)20%(n=5)农药占比分别为98.9%和86.5%,在番茄中为92.9%和87.6%;SPE和Qu ECh ERS两种方法在苹果中定量限≤10μg/kg的农药占比为100.0%和96.1%,在番茄中为100.0%和98.9%。两种前处理方法均能与高分辨质谱技术相结合并应用于果蔬农药残留的日常检测中,其中SPE净化效果较优,定量更为准确,但步骤稍显繁琐费时,而Qu ECh ERS方法简单快速,故在检测时可根据不同需要进行选择。     

改进的QuEChERS方法结合气相色谱串联质谱检测韭菜中的多种农药残留

采用改进的Qu ECh ERS方法结合气相色谱串联质谱(GC-MS/MS)检测韭菜中的多种农药残留。样品经含1%乙酸的乙腈匀质提取,采用分散固相萃取剂净化,在GC-MS/MS多反应监测(MRM)模式下进行测定。对Qu ECh ERS方法的提取和净化条件进行了优化。在优化条件下,44种农药残留在10~500μg/kg范围内呈良好线性关系,相关系数的平方(R~2)在0.9971~0.9999之间。在10μg/kg和100μg/kg添加水平下,44种农药的平均回收率为91.5%~119.6%,日内日间相对标准偏差小于14.1%。将所建立的方法用于实际样品的分析中,取得了较好的效果。     

QuEChERS-超高效液相色谱-串联质谱法测定荨麻提取物中17种氨基甲酸酯类农药残留量

采用Qu ECh ERS-超高液相色谱-串联质谱技术,建立了荨麻提取物中17种常见的氨基甲酸酯类农药残留量的检测方法。样品用含1%甲酸的乙腈提取,Qu ECh ERS法净化,电喷雾正离子(ESI+)模式电离,多反应监测模式检测,基质匹配标准曲线法定量。17种氨基甲酸酯农药在2.5~50μg/L线性关系良好,相关系数均大于0.9920,加标浓度为10,20,50μg/kg,平均回收率在65.3%~119.2%,相对标准偏差(RSD)均低于11%,检出限在0.12~1.7μg/kg。方法适用于荨麻等植物提取物中氨基甲酸酯类农药残留量的测定。     

柱前衍生-高效液相色谱法测定茶叶中的黄曲霉毒素B1

应用柱前衍生-高效液相色谱法测定茶叶中黄曲霉毒素B1的含量。样品采用乙腈(85+15)溶液提取,滤液用MycoSepTM226柱净化,加入正己烷和三氟乙酸衍生,经C18色谱柱分离,荧光检测器检测。黄曲霉毒素B1的质量浓度在0.20~10.0μg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)为0.1μg·kg-1。在0.5,1.0,5.0μg·L-1等3个浓度水平进行加标回收试验,回收率在91.9%~102%之间,测定值的相对标准偏差(n=6)在1.5%~6.9%之间。     

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.     

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.     

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.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

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.