连续流动分析仪测定水溶肥中氧化钾

用连续流动分析仪测定水溶肥中氧化钾含量,并与农业部规定的标准分析方法(NY/T1977—2010)结果进行比较,结果表明,样品溶液中氧化钾在0~400 mg/L范围内线性良好,相关系数r=0.999 5,与四苯硼酸钾重量法结果比对结果接近,绝对偏差小于0.23%,准确度高,加标回收率在98.2%~101%,重现性良好,10次重复测定相对标准偏差为0.22%,可用于水溶肥中氧化钾的分析测定。     

火焰原子吸收分光光度法测定五氧化二钒中铁及氧化钾、氧化钠含量

五氧化二钒样品用盐酸分解,在稀盐酸介质中,用原子吸收分光光度计分别于248.3,766.5,589.0 nm波长处,使用空气–乙炔火焰,测量五氧化二钒中铁及氧化钾、氧化钠含量。在最佳实验条件下,铁、氧化钾、氧化钠的质量浓度分别在0.05~0.20,0.05~0.80,0.20~1.0 mg/L范围内与吸光度线性关系良好,相关系数分别为0.998 6,0.994 3,0.994 2。方法检出限铁为6.7μg/L,氧化钾为1.0μg/L,氧化钠为1.4μg/L,加标回收率为95.9%~103.0%。铁、氧化钾、氧化钠测定结果的相对标准偏差分别为3.2%,4.2%,2.9%(n=6)。该方法适合五氧化二钒中铁及氧化钾、氧化钠的测定。     

火焰原子吸收光谱法测定长石中的钾和钠

建立火焰原子吸收光谱法测定长石中钾和钠的含量。样品采用硝酸–氢氟酸进行消解,用10 mL 5%的硝酸加热浸取后加水称量试液的质量,用火焰原子吸收分光光度仪进行测定。氧化钾和氧化钠的质量浓度在0.00～40.28μg/g范围内与吸光度呈良好的线性关系,相关系数为0.999 3～0.999 4,方法检出限为0.002 8～0.007 9μg/g。测定结果的相对标准偏差为0.78%～3.91%(n=6),测定值与标准值的相对误差为–1.70%～1.52%。该方法操作简单、快速,结果准确、可靠,满足地质样品的检测要求,适用于长石中钾和钠的测定。     

火焰原子吸收光谱法测定天然气转化催化剂中的氧化钾

建立火焰原子吸收光谱法测定天然气转化催化剂中氧化钾的分析方法。该方法将催化剂样品和助溶剂四硼酸锂熔融后再用盐酸溶解定容,采用火焰原子吸收光谱仪对样品溶液进行测定。在优化的实验条件下,钾离子的质量浓度在0.05~0.50 mg/L范围内与吸光度呈良好线性关系,相关系数为0.9995。钾的方法检出限为0.001 mg/L,定量限为0.01 mg/L,测定结果的相对标准偏差为2.6%~4.3%(n=6),样品加标回收率为97.8%~102.3%。与HG/T 3543-2014中的酸溶制样法相比,该方法能够将催化剂样品中的难溶钾盐溶出,分析结果准确度更高,可用于天然气转化催化剂中氧化钾含量的测定。     

石墨炉原子吸收法测定食品添加剂甲壳素中的镉和铅

采用程序控制温度,一次完成甲壳素样品的炭化和灰化,通过氢氟酸-硝酸消除灰分中硅的干扰,用石墨炉原子吸收法直接测定其中的镉和铅.镉的浓度在0～50 ng/mL范围内与吸光度呈良好的线性关系,相关系数r= 0.9990;铅的浓度在0～300 ng/mL范围内与吸光度呈良好的线性关系,相关系数r=0.9990 .镉的回收率为90.6%～102.0%,测定结果的相对标准偏差为4.37%(n=8);铅的回收率为91.3%～102.1%,测定结果的相对标准偏差为8.67%(n=8).     

离子色谱法同时测定蛋白胨中氯离子、硫酸根离子、碘离子

建立离子色谱法测定蛋白胨中氯离子、硫酸根离子、碘离子3种阴离子的含量。采用氢氧化钾淋洗液发生器产生的KOH溶液为流动相,进行梯度淋洗,流量为1.0 mL/min。氯离子、硫酸根离子的质量浓度分别在0.5～200μg/mL范围内与色谱峰面积呈良好的线性关系,碘离子的质量浓度在0.75～50μg/mL范围内与色谱峰面积呈良好的线性,线性相关系数均不小于0.999,检出限分别为0.003,0.01,0.22μg/mL。样品加标回收率为92.94%～96.59%,测定结果的相对标准偏差为2.42%～5.70%(n=9)。该方法灵敏、高效,可用于蛋白胨中氯离子、硫酸根离子、碘离子的快速准确测定。     

电感耦合等离子体发射光谱法测定化妆品中可溶性钡与镍

建立电感耦合等离子体发射光谱法测定化妆品中可溶性钡和可溶性镍含量的方法。以5%硝酸–2%氢氟酸混合溶液为提取剂,在(60±2)℃下连续震荡提取1 h,然后在(60±2)℃下放置1 h。化妆品中可溶性镍与可溶性钡的质量浓度在0.01～1.0 mg/L范围内与信号强度均呈良好的线性关系,线性相关系数分均为0.999 9,镍、钡的定量限均为0.25 mg/kg。在0.5,5.0,40 mg/kg添加水平下,可溶性镍的加标回收率为84.4%～112.7%,可溶性钡的加标回收率为96.7%～117.3%,测定结果的相对标准偏差为0.9%～4.8%(n=6)。该方法具简单、快速,测定结果准确稳定,可用于化妆品中可溶性钡和可溶性镍的测定。     

氢化物发生-原子荧光光谱法测定牡蛎中的镉

利用HNO3–HClO4混合酸消解样品,采用氢化物发生–原子荧光光谱法测定牡蛎中镉的含量。在优化的仪器工作条件下,镉的质量浓度在0.20～1.50μg/L范围内与荧光强度呈良好的线性关系,线性相关系数为0.9992,检出限为0.10μg/L,测定结果的相对标准偏差为4.48%(n=12),加标回收率为94.3%～106.1%。测定了标准物质贻贝GB 08571中镉的含量,测定结果与标准值一致。该方法可满足牡蛎中微量镉的分析测定。     

氧弹燃烧-离子色谱法测定电子产品连接线中的卤素

建立了氧弹燃烧法处理电子产品连接线,离子色谱测定样品中卤素的分析方法。选用TSK-gelSuperIC-AZ阴离子分析柱,以NaHCO3(7.5mmol/L)+Na2CO3(1.1mmol/L)为流动相等度洗脱,抑制电导检测。结果表明,该条件下F-浓度在0.02～2mg/L,Cl-和Br-浓度在0.05～5mg/L范围内峰面积与浓度的线性关系良好(r>0.999),实际样品中卤素回收率为90.52%～97.24%,样品测定结果相对标准偏差均为0.73%～2.01%(n=5)。应用氧弹燃烧-离子色谱法测定电子产品连接线中的卤素离子,方法简便、快捷,测定结果准确。     

气相色谱法测定固定污染源废气中6种丙烯酸酯

建立气相色谱法同时测定固定污染源中6种丙烯酸酯。采用气袋采样，直接进样，以气相色谱法同时测定固定污染源中6种丙烯酸酯。6种丙烯酸酯在0.5～20μmol/mol范围内与色谱峰面积的线性关系良好，相关系数均不小于0.998，方法检出限为0.5～2.0 mg/m³。对低、中、高三种浓度标准气体进行分析，测定结果的相对标准偏差(n=6)分别为1.8%～3.5%、3.1%～4.1%和1.9%～3.0%；相对误差(n=6)分别为-6.2%～5.5%、1.2%～8.2%和-6.0%～(-4.1%)，实际样品加标回收率为91.3%～125%。该方法适合于固定污染源废气中丙烯酸酯化合物的分析。     

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.