离子色谱法测定石膏中的三氧化硫

采用离子色谱法测定石膏中三氧化硫的含量。石膏样品溶解于水中,经超声提取,微孔滤膜过滤,IonPac AS11-HC阴离子交换色谱柱(4mm×250mm)分离,免试剂淋洗液梯度淋洗,电导检测器检测。硫酸盐的质量浓度在20.0~500.0mg·L-1之间与其峰面积呈线性关系。方法应用于石膏标准样品(GBW 03109,GBW 03111)的分析,测定值与认定值相符。加标回收率在80.6%~109%之间,测定值的相对标准偏差(n=6)在1.3%~6.8%之间。     

高频红外碳硫分析仪测定石膏矿中的三氧化硫

利用高频红外碳硫仪对石膏矿中三氧化硫含量的测定进行了研究,取得了较好的结果.方法检出限为0.003 0%.用石膏标准样品(GBW03109a,GBW03110)进行分析,测定值与认定值相符,测定值的相对标准偏差(n=9)在0.32%~0.81%之间.使用石膏标准样品(GBW03111)进行本法与国标硫酸钡重量法做比对试验,测定结果无显著性差异.加标回收率为96.4%~104.0%.     

电感耦合等离子体质谱法测定水产品中铬、铜、锌、砷、镉、铅的含量北大核心CSCD

取水产品样品0.500 0 g,加入硝酸5 mL、水2 mL、30%(质量分数)过氧化氢溶液1 mL,按微波消解程序进行消解,将消解液于100℃蒸发至1~2 mL,用水定容至25 mL。采用电感耦合等离子体质谱法测定上述溶液中铬、铜、锌、砷、镉、铅的含量。各元素测定值的相对标准偏差(n=6)在1.2%~5.9%之间,回收率在96.6%~102%之间。按上述方法分析标准物质GBW 10023、GBW 10024、GBW 10050,FAPAS质控基准物质TET012RM以及质控样品T07225QC,各元素测定值与认定值一致。     

电感耦合等离子体质谱法测定水产品中铬、铜、锌、砷、镉、铅的含量

取水产品样品0.500 0 g,加入硝酸5 mL、水2 mL、30%(质量分数)过氧化氢溶液1 mL,按微波消解程序进行消解,将消解液于100℃蒸发至1~2 mL,用水定容至25 mL。采用电感耦合等离子体质谱法测定上述溶液中铬、铜、锌、砷、镉、铅的含量。各元素测定值的相对标准偏差(n=6)在1.2%~5.9%之间,回收率在96.6%~102%之间。按上述方法分析标准物质GBW 10023、GBW 10024、GBW 10050,FAPAS质控基准物质TET012RM以及质控样品T07225QC,各元素测定值与认定值一致。     

自动电位滴定法标定硫酸铈溶液和测定硫酸亚铁片中铁含量

采用自动电位滴定法标定硫酸铈溶液,并进行硫酸亚铁片中铁含量的测定。自动电位滴定法以电位突跃监测终点,在45℃~50℃之间,以草酸钠溶液标定硫酸铈溶液,测定值的相对标准偏差(n=5)为0.070%。取硫酸亚铁片1片用0.01mol·L-1硫酸溶液30mL溶解,直接用硫酸铈溶液滴定测定铁含量。方法用于硫酸亚铁片样品分析,回收率为100%,测定值的相对标准偏差(n=5)在1.2%~2.6%之间。     

电感耦合等离子体原子发射光谱法测定铜电积液中锑、铋、钴、镍和砷的含量

样品(2.00mL)用盐酸10mL、硝酸3mL溶解后,蒸馏至2~3mL,加入100g·L-1酒石酸溶液2mL,用盐酸(5+95)溶液稀释定容至100mL。采用电感耦合等离子体原子发射光谱法测定样品溶液中锑、铋、钴、镍和砷的含量。选择锑、铋、钴、镍、砷元素的分析谱线分别为206.836,223.061,228.615,231.604,193.696nm。5种元素在一定的质量浓度范围内与其发射强度呈线性关系,方法的检出限(3s)在0.005~0.130mg·L-1之间。方法用于铜电积液分析,所得测定值与火焰原子吸收光谱法测定结果相符。加标回收率在95.8%~108%之间,测定值的相对标准偏差(n=11)在0.70%~6.4%之间。     

高效阴离子色谱分离-积分脉冲安培法测定地质样品中总碘

采用高效阴离子色谱分离-积分脉冲安培法测定地质样品中总碘的含量。采用碳酸钠-氧化锌烧结方法分解样品,烧结温度为700℃。以亚硫酸钠溶液作为还原剂,以氢氧化钠溶液为淋洗液,在IonPac AG11和IonPac AS11阴离子交换柱上分离。碘的质量分数在0.16~50μg·g-1范围内与其峰高呈线性关系,检出限(3s)为0.08μg·g-1。方法应用于国家标准物质的测定,测定值与认定值相符,测定值的相对标准偏差(n=12)在2.7%~7.3%之间。     

电感耦合等离子体发射光谱法测定磷石膏中的水溶性五氧化二磷

建立电感耦合等离子发射光谱法(ICP–OES)测定磷石膏中水溶性五氧化二磷含量的方法。用超声波快速提取磷石膏中的磷,在178.284 nm波长下,用CID固体检测器测定样品溶液的光谱强度。五氧化二磷的质量浓度在0.007~200 mg/L范围内与光谱强度线性关系良好,线性相关系数r=0.999 96,检出限为0.006 9 mg/L。样品加标回收率在98%~102%之间,测定结果的相对标准偏差为0.95%~1.11%(n=6),该方法的测定结果与国标法基本一致。该法简便、快速,适合磷石膏中水溶性五氧化二磷的测定。     

ICP–AES法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼的含量

建立电感耦合等离子体原子发射光谱(ICP–AES)法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼7种元素含量的方法。试样用盐酸与硝酸混合酸溶液溶解,采用溶解国家标准样品的方法制备校准曲线溶液,确定了元素最佳分析谱线。各元素的含量在其测试范围内与原子发射强度呈良好的线性关系,线性相关系数不小于0.999,7种元素的检出限在0.000 3%~0.003 0%之间。该方法应用于铬镍不锈钢标准样品的测定,测定值与认定值相符,测定值的相对标准偏差在0.12%~1.15%之间(n=8)。应用于铬镍不锈钢样品测定时,加标回收率在90%~110%之间。该方法操作简便、迅速,可满足日常铬镍不锈钢中多元素含量的检测需要。     

电感耦合等离子体质谱法测定砷滤饼中的铼

砷滤饼样品在硝酸-过氧化氢混合液中微波消解,采用电感耦合等离子体质谱法测定样品溶液中铼的含量。185 Re作为测量同位素,以~(193)Ir为内标物。铼的线性范围为50μg·L~(-1)以内,方法的检出限(3s)为0.037μg·L~(-1)。方法的加标回收率在96.0%~102%之间,测定值的相对标准偏差(n=11)在2.0%~3.8%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.