氘代同位素内标气相色谱-质谱法测定鱼贝类肌肉中β-雌二醇残留

建立了不同鱼贝类肌肉组织中以氘代同位素为内标测定β-雌二醇残留量的气相色谱/质谱(GC/MS)方法。样品中加入内标β-雌二醇-D2和乙酸钠缓冲溶液匀质后,用乙腈超声提取,经过正己烷脱脂,C18固相萃取柱净化和柱前三甲基硅烷化后,进行GC/MS分析。根据β-雌二醇和内标衍生物保留时间、主要特征离子及其相对丰度和平均质谱图定性;选择离子监测(SIM)模式下,根据β-雌二醇和内标衍生物定量离子质量色谱图的峰面积比值,内标标准曲线法定量。实验结果表明,在0.005~0.25mg/L范围内,衍生物定量离子峰面积比值与β-雌二醇浓度呈现良好线性关系,相关系数为0.9995;方法定量检出限为0.2μg/kg。当添加水平为0.2~5.0μg/kg时,回收率为68.5%~100.1%,相对标准偏差为4.8%~10.1%。通过对市场上7种鱼贝类的检测,进一步证明该法可实现对样品进行灵敏、准确的定性定量分析。     

气相色谱–串联质谱法快速测定茶叶中的蒽醌

建立气相色谱–串联质谱法(GC–MS–MS)快速测定茶叶中蒽醌的方法。样品中的蒽醌用色谱纯乙腈提取,经过涡旋1 min,超声20 min,离心、浓缩后用固相萃取柱(SPE)净化,以DB–5MS毛细管柱分离,以m/z 207.9,152为定性离子对、m/z 207.9,180为定量离子对,多反应检测模式下测定,外标法定量。蒽醌的质量浓度在1~500μg/L范围内与定量离子的峰面积呈良好的线性关系,相关系数为0.999 98,方法的检出限为1μg/kg。在10,20,50μg/kg加标水平下,样品加标回收率为92.85%~98.10%,测定结果的相对标准偏差为8.50%~11.05%(n=5)。该方法简单、快速,检出限低,准确度和精密度高,可用于茶叶中蒽醌的检测。     

吹扫捕集-气相色谱-质谱法测定土壤中乙酸乙酯和丙烯酸乙酯

建立吹扫捕集-气相色谱-质谱法测定土壤中乙酸乙酯和丙烯酸乙酯的方法。称量5 g土壤样品于40 mL吹扫瓶中,加入5 mL超纯水进行吹扫捕集提取,用DB-624毛细管色谱柱（60 m×250μm,1.4μm）分离,全扫描后进行谱库检索定性,内标法定量。乙酸乙酯和丙烯酸乙酯的质量浓度在5.0～200μg/L范围内与定量离子与内标定量离子色谱峰面积的比值线性关系良好,相关系数分别为0.999 6和0.999 2,检出限分别为1.2、1.4μg/kg。样品加标平均回收率分别为95.8%～108%,79.9%～98.0%,测定结果的相对标准偏差分别为1.92%～13.7%、2.05%～13.8%(n=6)。该方法可用于土壤中乙酸乙酯和丙烯酸乙酯的测定。     

气相色谱–质谱法测定白酒中的邻苯二甲酸酯类

采用气相色谱–质谱法对常见名贵白酒中的16种邻苯二甲酸酯类含量进行测定。将样品提取、净化后,经气相色谱–质谱联用仪进行分离测定。采用特征选择离子检测扫描(SIM),以色谱保留时间和色谱碎片的丰度比定性,以峰面积外标法定量。16种邻苯二甲酸酯类物质的含量与色谱峰面积在0~2.0μg/m L范围内线性良好,线性相关系数均在0.995以上,方法检出限为0.05 mg/L。16种邻苯二甲酸酯含量测定结果的相对标准偏差均小于10%(n=6),加标回收率为91.21%~105.22%。该方法样品前处理简单,灵敏度高,适用于同时定性及定量检测白酒中16种邻苯二甲酸酯。     

气相色谱–质谱法测定涂料中游离氨基甲酸乙酯

采用气相色谱–质谱法测定涂料中游离氨基甲酸乙酯的含量,对样品进行超声波萃取和高速离心静化处理后,选用选择离子和保留时间定性、外标法定量,色谱柱选择RTX–WAX极性色谱柱。游离氨基甲酸乙酯的质量浓度在0.1~10.0μg/m L范围内与色谱峰面积呈良好的线性,线性相关系数为0.999 9,检出限为0.04μg/m L。加标回收率在96.8%~100.5%之间,测定结果的相对标准偏差为2.0%~11.1%(n=6)。该方法样品预处理简单、重现性好、准确度高,适用于涂料中游离氨基甲酸乙酯的检测。     

气相色谱–质谱联用法测定空气中的丙烯腈

建立测定空气中丙烯腈的气相色谱–质谱联用方法。用活性炭管采集样品,以体积分数为2%的丙酮二硫化碳溶液解吸,利用气相色谱–质谱法以选择离子扫描方式采集数据并进行分析,以色谱峰面积外标法定量。丙烯腈的质量浓度在0~100μg/m L范围内与色谱峰面积线性关系良好,线性相关系数(r~2)为0.999 0。丙烯腈检出限为1.2μg/m L,最低检出质量浓度为0.16 mg/m~3(以采样体积7.5 L计),平均加标回收率为97.0%~99.3%,测定结果的相对标准偏差为3.0%~4.2%(n=6)。该方法定性、定量准确,精密度、灵敏度高,可用于空气中丙烯腈的常规检测。     

液相色谱-串联质谱法测定苹果中水胺硫磷

建立苹果中水胺硫磷残留的液相色谱-串联质谱检测方法。样品以乙腈提取,采用电喷雾正离子源(ESI~+)和多重反应监测(MRM)模式测定,基质匹配标准曲线定量。结果表明:苹果基质中,水胺硫磷色谱峰面积响应值与其质量浓度呈良好线性关系(r~2=0.999),方法的线性范围为0.3~100μg/L,检出限为0.15μg/L,定量限为0.5μg/L。在5,50,100μg/kg添加水平下,水胺硫磷回收率为77.3%~95.2%,测定结果的相对标准偏差为5.7%~8.9%(n=6)。方法精密度和准确度满足残留限量监测要求。     

超高效液相色谱–串联质谱法测定饮用水中微囊藻毒素

建立饮用水中微囊藻毒素(MC–RR,MC–LR)的超高效液相色谱–串联质谱检测方法。样品经PVDF针式过滤头过滤后直接进样,采用喷雾正离子源(ESI~+)和多重反应监测模式(MRM)测定。MC–RR的质量浓度在0.02~10.00μg/L范围内与色谱峰面积呈良好的线性,线性相关系数r~2=0.998 9,检出限为0.096μg/L,测定结果的相对标准偏差为6.6%~9.1%(n=7),加标回收率为99.0%~103.0%。MC–LR的质量浓度在0.1~20μg/L范围内与色谱峰面积呈良好的线性,线性相关系数r~2=0.999 2,检出限为0.188μg/L,测定结果的相对标准偏差为4.3%~10.0%(n=7),加标回收率为93.0%~114.0%。该方法灵敏度高、重现性好,可用于饮用水中微囊藻毒素的检测。     

四通道色谱分离仪净化/气相色谱-质谱法测定烟叶中的多环芳烃

建立了同时检测新鲜烟叶中16种多环芳烃(PAHs)的四通道色谱分离仪净化/气相色谱-质谱(GC-MS)分析方法。样品经二氯甲烷索氏提取,四通道色谱分离仪净化,GC-MS选择离子监测模式(SIM)测定和外标法定量,重点考察了新鲜烟叶提取液的分离净化条件。结果表明:16种PAHs类化合物在10~1 000μg/kg范围内定量离子的峰面积与质量浓度呈较好的线性关系(r0.99)。仪器检出限(LOD)为0.35~1.75μg/kg,方法检出限(MDLs)为1.01~2.87μg/kg。在10,50,200μg/kg 3个浓度水平下的加标回收率为81.0%~107.8%,相对标准偏差(RSD,n=6)为2.7%~8.0%。该方法简便、快捷、可操作性强、应用范围广,适合于烟草等作物中PAHs类化合物的分析检测。     

吹扫捕集–气相色谱质谱联用法测定地表水中6种氯苯类化合物

建立吹扫捕集–气相色谱质谱联用法测定地表水中6种氯苯类化合物的方法。在水样中加入过饱和硫酸钠溶液提高吹扫捕集效率,通过吹扫捕集富集水样中的6种氯苯类化合物,解吸后用气相色谱–质谱联用法同时测定,内标法定量。6种氯苯类化合物在0~60μg/L范围内与定量离子色谱峰面积线性关系良好,线性相关系数为0.999 0~0.999 5,检出限为0.01~0.02μg/L,测定结果的相对标准偏差为1.74%~3.83%(n=6),加标回收率为92.8%~97.9%。该方法操作简便,准确度高,重现性好,能够满足地表水中6种氯苯类化合物的同时测定。     

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.     

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.     

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.     

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.