高效液相色谱-电喷雾电离三级四极杆质谱测定鸡肉中氯霉素、甲砜霉素和氟甲砜霉素的残留量

建立了鸡肉中3种氯霉素类抗生素残留的高效液相色谱-电喷雾电离三级四极杆质谱(HPLC-ESI-MS-MS)测定法。该方法采用多反应监测(MRM)负离子模式,可一次对鸡肉中的氯霉素、甲砜霉素和氟甲砜霉素进行定性和定量。该方法仅需1 g样品,并省去固相萃取步骤,具有操作简便、有机试剂消耗量少、测定周期短等优点。方法的检出限为0.010 μg/kg,测定低限为0.100 μg/kg,线性范围为0.050~1.00 μg/L,加标回收率为69.0%~92.8%,相对标准偏差为6.3%~12.9%。     

超高效液相色谱法测定水产品中甲砜霉素和氟甲砜霉素残留

建立了一种同时测定水产品中甲砜霉素和氟甲砜霉素药物残留的超高效液相色谱(UPLC)方法。样品经乙酸乙酯提取,正己烷液-液分配除脂,过HLB固相萃取小柱,用3mL10%甲醇淋洗,5mL100%甲醇洗脱,洗脱液用氮气吹干,残渣用1mL10%乙腈水溶液定容。采用超高效液相色谱分离,二极管阵列检测器检测,外标法定量。甲砜霉素在0.05~2.0mg/L,氟甲砜霉素在0.025~1.0mg/L范围线性关系良好,相关系数分别为0.9996、0.9999;样品加标平均回收率分别为80.0%、95.8%;相对标准偏差分别为5.6%、11.2%,甲砜霉素、氟甲砜霉素检出限分别为10μg/kg、5μg/kg。     

高效液相色谱-线性离子阱三级质谱法检测花生中涕灭威及其代谢物涕灭威砜、涕灭威亚砜

建立了花生中涕灭威及其代谢物涕灭威砜、涕灭威亚砜的高效液相色谱-线性离子阱三级质谱分析方法。样品经环己烷饱和的乙腈提取,凝胶渗透色谱净化后,用高效液相色谱-线性离子阱三级质谱法对样品中的目标物进行定性确证和定量分析。在Capcell PAK CR色谱柱上以含5 mmol/L NH4Ac-HAc的乙腈为流动相进行梯度洗脱分离。采用电喷雾离子源正离子模式进行三级选择离子监测,以涕灭威-d3作为3个目标物的内标物。通过比较基质匹配曲线和纯溶剂标准曲线计算回收率评估基质效应。方法的线性范围为10～500 μg/L,检出限为4～5 μg/kg。涕灭威、涕灭威砜、涕灭威亚砜在3个加标水平(10、20、40 μg/kg)的回收率为81.5%～115%,相对标准偏差为6.35%～15.1%。应用该方法对花生样品进行了测定,结果令人满意。     

高效液相色谱-串联质谱法测定生姜中涕灭威及其代谢物的残留量

提出了高效液相色谱-串联质谱法测定生姜中涕灭威及其代谢物涕灭威亚砜、涕灭威砜的残留量。样品经乙腈均质提取,氨基固相萃取柱净化后,用YMC C₁₈色谱柱分离,采用电喷雾离子化正离子模式及多反应监测模式进行测定。涕灭威、涕灭威亚砜和涕灭威砜的测定下限（10S/N）均为1μg·kg^-1。在3个标准加入水平下进行了回收率和精密度试验,方法的回收率在64.1%～114%之间,测定值的相对标准偏差（n=6）在1.5%～4.9%之间。     

高效液相色谱-串联质谱法同时测定饲料中氯霉素、甲砜霉素与氟甲砜霉素残留量

建立了饲料中氯霉素(CAP)、甲砜霉素(TAP)、氟甲砜霉素(FF)3种抗生素残留量的高效液相色谱-串联质谱(HPLC-MS/MS)测定方法。样品经碱化乙酸乙酯提取,蒸发浓缩,提取物经正己烷脱脂,液-液分配净化后,采用电喷雾电离源(ESI)负离子多反应监测(MRM)模式检测,内标法定量。氯霉素、氟甲砜霉素和甲砜霉素的线性范围分别为0.2～10.0、0.2～10.0、1.0～50.0μg/L,相关系数(r2)不低于0.990 0;其检出限分别为0.1、0.1、0.5μg/kg,定量下限分别为0.3、0.3、1.5μg/kg。3种抗生素药物的平均回收率为77%～108%,相对标准偏差(RSD)不大于10.9%。     

生姜中涕灭威及涕灭威砜的GC分析方法研究

本文研究了气相色谱火焰光度检测器法(FPD)同时检测生姜中涕灭威及其代谢物涕灭威砜的分析方法。样品经乙腈提取,无水硫酸钠柱脱水,弗罗里硅土回相萃取柱净化后用火焰光度检测器硫滤光片进行检测。结果表明,当涕灭威和涕灭威砜添加水平在0.040、0.080和0.200 mg/kg时,样品的回收率范围分别为81.3%~103.8%和91.5%~104.7%,样品的标准偏差(RSD)范围分别为2.8%~4.8%和4.1%~5.5%。     

多壁碳纳米管滤过型净化柱净化-超高效液相色谱/串联质谱法同时测定生姜中的涕灭威及其代谢物

建立了多壁碳纳米管滤过型净化柱净化-超高效液相色谱/串联质谱联用技术同时测定生姜中涕灭威及其代谢物的分析方法。生姜样品经乙腈提取后,用多壁碳纳米管滤过型净化柱进行2次反复抽提净化,净化液用氮气吹干,用乙腈-水（5：95,v/v）溶解,采用正离子多反应监测（MRM）模式进行分析,外标法定量。结果表明：涕灭威、涕灭威砜及涕灭威亚砜在0.5~200 μg/L浓度范围内呈线性,其相关系数（r²）均大于0.99;在2、20、200 μg/kg添加水平下,回收率为71.4%~89.8%,相对标准偏差范围为0.7%~13.2%;3种目标物的定量限为1.0~2.0 μg/kg。本方法操作简单,灵敏度、准确度和精密度均满足农药多残留检测技术的要求,适用于生姜中涕灭威及其代谢物残留的快速测定。     

高效液相色谱-串联质谱法同时测定水产品中氯霉素、甲砜霉素和氟甲砜霉素的残留量

建立了水产品中氯霉素、甲砜霉素和氟甲砜霉素药物残留量同时测定的高效液相色谱-串联质谱方法。以氘代氯霉素做内标,选择乙酸乙酯提取,HLB固相萃取柱净化,洗脱液氮气吹干,采用LC-MS/MS选择反应监测(SRM)负离子模式进行定性、定量分析。结果表明:氯霉素的检出限(LOD)为0.01μg/kg,甲砜霉素和氟甲砜霉素检出限(LOD)为0.03μg/kg,检测结果的相对标准偏差为3.3%～9.7%(n=6),加标回收率达到78.6%～110.5%。该方法在水产品中氯霉素、甲砜霉素和氟甲砜霉素药物的残留测定中具有很好的应用前景。     

液相色谱-串联质谱法研究涕灭威及其代谢物在白菜中的动态行为

采用液相色谱-串联质谱法(LC-MS/MS)研究了白菜中涕灭威及其代谢物的残留动态行为。按农民常用施药量(3000 g/hm²)将涕灭威沟施予田地后,定期取样检测,并建立其残留行为的数学模型。结果表明,用LC-MS/MS测定涕灭威及其代谢物,在0.005~0.2 mg/L范围内线性关系良好,平均回收率为78.9%~108.5%,相对标准偏差为2.03%~8.91%(n=8)。涕灭威在白菜中的浓度升高和降低的过程均符合一级动力学模型(c=0.020e^0.136t和c=0.65e^-0.059t),相关系数(r²)分别为0.888和0.979,半衰期为29.1天。代谢产物涕灭威砜和涕灭威亚砜在白菜中的浓度降低时同样符合一级动力学方程(c=23.4e^-0.044t和c=4.54e^-0.027t), r²分别为0.916和0.972。涕灭威、涕灭威砜和涕灭威亚砜在白菜中的含量要降到国内外限量要求0.01 mg/kg,分别需要70.7、226.6和176.3天。白菜生长周期为120天,收获时涕灭威砜和涕灭威亚砜含量仍超过国内外限量要求。因此,在本文施药量下,涕灭威不能使用。该数据为涕灭威的安全使用和农药残留动态行为研究提供了理论依据。     

高效液相色谱-电喷雾电离三级四极杆质谱检测动物源食品中氯霉素、甲砜霉素、氟苯尼考残留量

建立了动物源产品中氯霉素、甲砜霉素、氟苯尼考残留量的高效液相色谱-电喷雾电离三级四极杆质谱(LC-ESI-MS/MS)的方法。前处理方法包括添加同位素内标氯霉素-d5,碱化乙酸乙酯提取,C18小柱净化。该方法采用负离子,多反应监测氯霉素四对离子(321.0/151.9,321.0/256.6,321.0/194.2,321.0/175.4),甲砜霉素两对离子(354.1/185.0,354.1/290.0),氟苯尼考两对离子(356.0/335.9,356.0/185.1)和同位素内标氯霉素-d5(326.0/157.1)。该方法线性范围为0.1~1.6μg/kg;对不同基质样品的加标回收率为80%~112.5%;相对标准偏差小于11%;方法的测定低限为0.1μg/kg。     

Identification of Carbofuran And Methiocarb and their Transformation Products in Estuarine Waters by On-line Solid Phase Extraction Liquid Chromatography—Mass Spectrometry

Abstract

The degradation of the carbamate insecticides carbofuran and methiocarb in distilled and natural waters was determined. Degradation studies were carried out both under a xenon arc irradiation and natural sunlight at pesticide concentrations of 50–100 μg/L. 50–100 mL water sample were preconcentrated using automated online solid phase extraction (SPE) followed by liquid chromatography (LC), UV detection or post column fluorescence detection (EPA method 531.1 for carbamate insecticides). Structure identification was carried out by on-line SPE-LC-MS either with thermospray and/or high flow pneumatically assisted electrospray interfaces. Half-lives varying between 4–12.5 days for carbofuran and methiocarb were determined under natural sunlight exposure, being chemical hydrolysis the major degradation pathway. When using xenon arc lamp irradiation both pesticides degraded very rapidly with half-lives varying from 0.3–1.7 hours. The various degradation products identified were: methiocarb sulfoxide, 4-methylthio-3, 5-dimethylphenol, 3-hydroxy-7-carbofuranphenol and 2-hydroxy-3-(2-methylprop-1-enyl)-phenyl-N-methylcarbamate.     

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.     

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%).     

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.     

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.