酒类中微量甲醛的快速测定新方法

在FeCl3存在条件下,甲醛与自制蛋白液显色剂能生成紫色化合物,藉此可以定量测定微量甲醛。方法线性范围为1~10μg/10mL,线性相关系数r2=0.996,检出限为0.05μg/mL。用该法测定经活性炭脱色的啤酒和白酒中的甲醛含量,回收率为96.46%~103.32%,相对标准偏差为1.36%~2.09%(n=6)。     

水发食品中痕量甲醛的测定

为建立催化动力学荧光法测定痕量甲醛的新方法,基于在酸性介质中,甲醛催化KBrO3氧化藏红T的褪色反应,使其荧光猝灭的原理,将反应体系在沸水浴中加热8 min,流水冷却3min,采用动力学荧光法测定痕量甲醛。结果表明,甲醛在0.02~0.14μg/mL范围内与△F值呈良好的线性关系,线性方程为△F=-1.642 8+274.12C(μg/mL),r=0.996 9,检出限为0.011μg/mL。该法简便,快速,常见共存物质干扰小,可用于水发食品及其它食品中甲醛含量的测定,加标回收率为84.63%~94.93%。     

干灰化-氢化物原子荧光法测定肉制品中痕量锡

采用干灰化-氢化物原子荧光光谱法测定肉制品中的痕量锡。结果表明:在0.025~0.40μg/mL范围内,锡浓度与荧光值之间具有良好的线性关系(r=0.9997)。本法测定结果的相对标准偏差(RSD)为7.1%~8.9%,回收率为93%~97%,检出限为0.056μg/kg。     

柱前衍生-高效液相色谱法测定蔬菜中甲醛含量

建立了蔬菜中甲醛含量的高效液相色谱分析方法。样品用水提取、2,4-二硝基苯肼衍生及二氯甲烷萃取、浓缩后,采用Waters Sunfire C18色谱柱(250×4.6 mm,5μm)分离,流动相为乙腈-水(1∶1,V/V),在355nm波长处紫外检测。甲醛在0.1~2.0μg/mL浓度范围内呈线性关系,相关系数0.9989,方法检出限为1.0 mg/kg,在2~10mg/kg添加浓度范围内,甲醛平均回收率为78.1%~114.2%,相对标准偏差在0.8%~9.5%之间。     

比久农药中游离偏二甲肼的高效液相色谱快速测定

建立了用甲醛衍生测定农药比久样品中微量的偏二甲肼的方法。采用甲醛与偏二甲肼柱前衍生,在室温、中性溶液中反应10 min,生成确定量的有较强紫外吸收的偏二甲腙,不须富集可直接用HPLC法测定偏二甲肼。研究了甲醛与偏二甲肼的反应条件及产物的光谱特征,测得衍生物的最大吸收波长λmax=237 nm和表观摩尔吸光系数ε=3.6×103(L.mol-1.cm-1),选定ZorbaxODS色谱柱,V(磷酸盐缓冲溶液,pH 7)∶V(甲醇)=94∶6为流动相,检测波长为237 nm。结果表明:在0.56~960μg/mL范围内回归方程为:A=0.4677ρ-0.2790,R2=0.9998,检出限为1.3μg/g,回收率为97.5%~103.4%,相对标准偏差为0.9%~1.8%。     

ICP-AES法测定硼硅酸盐玻璃中的常量及微量元素

应用电感耦合等离子体原子发射光谱(ICP-AES)法,对硼硅酸盐玻璃中的常量元素Si、Ca、Al、B及微量元素Fe、Ti、Mg进行测定。在优化的工作条件下,各元素的检出限:SiO20.026μg/mL,Ca0.0002μg/mL,Al0.028μg/mL,B0.005μg/mL,Mg0.0002μg/mL,Fe0.006μg/mL,Ti0.005μg/mL。样品测定结果的相对标准偏差(n=6)在0.02%~1.47%之间,加入标准溶液的回收率为93.0%~103.2%。采用该方法对硼硅酸盐玻璃标准样品进行测定,测定值与标准值一致。     

静态顶空GC-MS法测定化妆品中的甲醛

建立了化妆品中甲醛的快速检测方法.采用自动顶空GC-MS法,优化顶空条件,选用叔丁醇作为内标,甲醛浓度在5.6～560μg/g范围内,线性良好(r=0.9995).甲醛的最低检出浓度为0.6μg/g,回收率90.23%～108.79%,RSD在4.3%～9.4%之间.     

1,3-环己二酮-甲醛作为荧光衍生试剂荧光分光光度法测定氨苄西林钠

建立了用1,3-环己二酮-甲醛作为荧光衍生试剂测定氨苄西林钠的方法。氨苄西林钠与1,3-环己二酮-甲醛反应生成一种强荧光物质。其最大激发波长是336 nm,最大发射波长是420 nm。氨苄西林钠浓度在0.01~0.6μg/mL范围内与相对荧光强度呈线性关系,线性方程为ρ=0.0007931F-0.06133,线性相关系数为0.9998,相对标准偏差为1.8%,检出限为10 ng/mL,回收率为97.0%~105.9%。考察了pH、温度、放置时间、干扰离子等对测定的影响。此法可用于注射液中氨苄西林钠的测定。     

毛细管气相色谱法测定鞋和箱包用胶粘剂中正己烷的含量

采用丙酮作为溶剂,选用19091N-213型毛细管色谱柱(30 m×0.32 mm i.d.,0.5μm)和氢火焰离子化检测器,以毛细管气相色谱法测定鞋和箱包用胶粘剂中正己烷含量。正己烷的浓度在0~1 000μg/mL与色谱峰面积成线性关系,线性回归方程为A=127 107c 383.26,相关系数r=0.999 1,检出限为0.003μg/mL,用该方法对胶粘剂样品进行测定,测定结果的相对标准偏差为2.8%~4.5%(n=5),加标回收率为96.4%~107.8%。     

农药苯噻草胺合成体系的高效液相色谱分析

建立了以α-羟基-N-甲基乙酰苯胺(HMA)和α-氯代苯并噻唑(CBT)为原料合成农药苯噻草胺的高效液相色谱分析方法,对原料和产物分别进行了定量。研究方法显示:在10.0~200.0、2.0~200.0和5.0~500.0(μg/mL)浓度范围内3种化合物的峰面积与进样量具有良好的线性关系,相关系数分别为r1=0.99992、r2=0.99999和r3=0.99999;方法在3个添加水平考察的平均加标回收率在85.0%~106.0%、88.0%~106.0%和90.0%~103.0%之间;相对标准偏差(RSD)分别为0.96%~0.63%、0.80%~0.47%和0.61%~0.20%;最低检出限LOD=0.02、0.01和0.005(μg/mL)。     

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.     

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.