离子色谱法同时测定不同时段酸雨中17种离子

应用离子色谱法同时测定不同时段酸雨中17种离子的含量。样品经离心沉淀后,经0.45μm滤膜过滤,滤液供离子色谱分析。阴离子分离时用Shodex SI-52 4E阴离子色谱柱,并用3.6mmol·L-1碳酸钠-0.6 mmol·L-1碳酸氢钠缓冲溶液作为淋洗液;阳离子分离时用TSKGEL阳离子色谱柱,并用2mmol·L-1硝酸溶液作为淋洗液,采用电导检测器进行检测。17种离子均在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限(3S/N)在1.4~18.7μg·L-1之间。回收率在95.0%~105%之间,测定值的相对标准偏差(n=6)在1.7%~7.2%之间。     

离子色谱法测定葡萄酒中的山梨酸和苯甲酸的含量

采用离子色谱法快速测定葡萄酒中的山梨酸和苯甲酸的含量。样品经超纯水稀释20倍,用聚酰胺粉末吸附提取溶液中的色素,净化液在IonPac AS11-HC阴离子色谱柱上分离,以30mmol·L~(-1)氢氧化钾溶液为淋洗液,采用抑制电导检测器检测,外标法定量。山梨酸和苯甲酸的质量浓度均在0.5~50 mg·L~(-1)范围内与峰面积呈线性关系,方法的检出限(3S/N)在1.4~1.7mg·L~(-1)之间。加标回收率在97.7%~104%之间,测定值的相对标准偏差(n=6)在2.4%~3.4%之间。     

离子色谱法测定食品中氯酸根含量

提出了离子色谱法测定食品中氯酸根含量的方法。食品样品采用水超声萃取15min,取部分萃取液加入亚铁氰化钾和乙酸锌溶液,离心,取上清液调节其酸度至pH 11~12,经IonPac AG19保护柱及Dionex IonPac AS19分离柱分离,以不同浓度的氢氧化钾溶液为淋洗液,采用抑制电导检测器检测。氯酸根的质量浓度在0.01~20.0mg·L-1范围内与其峰面积值之间呈线性关系,检出限(3S/N)为0.04mg·kg-1。方法用于青瓜和虾仁样品的分析,加标回收率在84.7%~93.4%之间,测定值的相对标准偏差(n=6)小于5%。     

固相萃取分离-离子色谱法测定化肥中三聚氰胺的含量

采用固相萃取分离-离子色谱法测定化肥中三聚氰胺的含量。化肥样品经10g·L-1三氯乙酸溶液振荡超声提取,离心后,萃取液经阳离子交换固相萃取柱净化。经净化的溶液经IonPac NG1保护柱及Dionex IonPac AS18分离柱分离,以含3mmol·L-1甲基磺酸的乙腈-水(15+85)混合液为淋洗液进行淋洗,所得提取液采用抑制电导检测器进行离子色谱分析。三聚氰胺的质量浓度在5.00~2 000mg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)为0.3mg·kg-1。加标回收率在89.7%~97.8%之间,测定值的相对标准偏差(n=6)在1.9%~4.5%之间。     

离子色谱法测定聚合物材料中铬(Ⅵ)含量

采用离子色谱法测定聚合物材料中的铬(Ⅵ)含量。取粒径小于250μm的聚合物样品用0.5mol·L-1氢氧化钠溶液提取3h。分取适量提取液经过滤及RP柱净化后,通过IonPac AG19保护柱及DIONEX IonPac AS19阴离子分离柱分离,先后用25mmol·L-1和50mmol·L-1的氢氧化钠溶液淋洗分离柱,采用抑制电导检测器检测。铬(Ⅵ)的质量浓度在0.10~10.0mg·L-1范围内与其峰面积呈线性关系,检出限(3s/k)为7mg·kg-1。对聚氯乙烯(PVC)样品连续测定8次,测定值的相对标准偏差为9.2%。用标准加入法进行方法的回收试验,测得回收率在95.2%~105%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。     

超声辅助分散液液微萃取-柱切换离子色谱法测定食用油中胆碱的含量

移取食用油样品5.00mL,加入3mol·L~(-1) HCl溶液100μL,在60℃下进行水解反应100min,将水解后的样品溶液在80℃水浴中进行超声辅助分散液液微萃取6min,乳浊液形成后以10 000转·min~(-1)转速离心10min,弃去上层油相,吸取下层水相,用0.45μm滤膜过滤,然后进行柱切换离子色谱分析,以Dionex IonPac CS12A阳离子交换色谱柱(250mm×4mm)及Dionex IonPac CG12A阳离子保护柱(50mm×4mm)为分离柱,以12mmol·L~(-1)甲烷磺酸溶液作为淋洗液,抑制型电导检测器检测。大豆油、花生油和亚麻籽油中胆碱的质量浓度均在0.02～2.50mg·L~(-1)内与对应的峰面积呈线性关系,检出限(3S/N)在1.58～1.99μg·L~(-1)之间。方法用于测定大豆油、花生油和亚麻籽油中的胆碱,测定值的日内和日间相对标准偏差(n=5)均小于7.0%,加标回收率在72.0%～98.0%之间。     

离子色谱法测定烟气脱硫石膏中半水亚硫酸钙的含量

用离子色谱法测定了烟气脱硫石膏中亚硫酸根的含量,并以此换算成半水亚硫酸钙的质量分数。半水亚硫酸钙在盐酸和氯化亚锡溶液中转化为二氧化硫,二氧化硫被吸收液吸收。吸收液经0.22μm的滤膜过滤后,分取25μL进样,经AS9-HC型分离柱和AG9-HC型保护柱分离,以8mmol·L-1碳酸钠-2mmol·L-1碳酸氢钠溶液为流动相进行淋洗,采用电导检测器进行检测。亚硫酸盐的质量浓度在1.00~100mg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)为0.05mg·L-1。以烟气脱硫石膏样品为基体进行加标回收试验,所得回收率为97.4%和101%,测定值的相对标准偏差(n=6)在0.35%~1.4%之间。     

离子色谱法测定磷酸锂中微量的杂质元素

对离子色谱法测定磷酸锂中钾、钙、镁杂质离子的方法进行研究。采用DX-80型离子色谱仪,分离柱为Ion Pac CS12A-5μm阳离子分离柱,用2×10-2mol.L-1甲基磺酸溶液为淋洗液,流速为2 mL.min-1,测定了磷酸锂中各钾、钙、镁杂质离子的含量,相关系数分别为0.9996,0.9993,0.9994,相对标准偏差小于3%,样品回收率为98.1%~100.3%。     

离子色谱法-光度检测天然水中铬(Ⅵ)

应用离子色谱法测定了天然水中六价铬,给出了试验装置及分析流程的图解。水样经0.22μm滤膜过滤后分取500μL进样,经保护柱(IonPac AG7)及分离柱(IonPac AS7)分离,由流量为0.25 mL.min-1的淋洗液(300 mmol.L-1硫酸铵和120 mmol.L-1氨水的混合溶液)洗脱。洗脱液与以流量为0.15 mL.min-1二苯羰酰二肼显色液在混合器中混合后,在反应圈中显色,在540 nm波长处作光度检测。线性范围在0.02~50μg.L-1之间,检出限(3S/N)为0.010μg.L-1。对一水样作了12次测定,测定结果的相对标准偏差为1.22%。     

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.