涂料中甲醛的分光光度测定新方法

在FeCl3存在的盐酸介质中,甲醛与蛋白胨反应生成紫色化合物,最大吸收波长555 nm,甲醛浓度在1~25μg/10 mL范围内,吸光度与浓度成线性关系,线性相关系数r2=0.9997,检出限0.05μg/mL。用本法测定经活性炭脱色的水溶性涂料中的甲醛含量,回收率为96.46%~103.32%,相对标准偏差(n=6)为1.36%~2.09%。     

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%。     

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%。     

顶空固相微萃取-气质联用法检测尿液中的曲马多

建立尿液中曲马多的顶空固相微萃取气相色谱质谱联用(HS-SPME-GC/MS)分析方法。利用响应面法对顶空固相微萃取的条件进行优化,在优化的条件下,采用SKF为内标,在选择离子模式下,选取m/z 58(曲马多)和m/z 86(SKF)为定量离子,利用GC/MS对尿液中的曲马多进行定量分析。工作曲线线性范围超过0.05~1.0μg/mL(r2=0.9962)。检测限为0.011μg/mL(S/N=3),定量限为0.038μg/mL(S/N=10),用0.1μg/mL和0.75μg/mL曲马多标准液计算回收率分别在100.20%~109.65%和98.43%~103.82%之间,RSD为5.32%和9.13%(n=5)。建立的方法适用于尿液中曲马多。     

离子色谱法测定烟用纸张中甲醛和乙二醛

建立了离子色谱检测烟用纸张中甲醛和乙二醛含量的分析方法。样品中的甲醛和乙二醛在碱性条件下与过氧化氢反应生成甲酸根和草酸根,使用离子色谱法测定其含量。考察并优化了样品前处理和色谱分析条件。实验表明,甲酸根和草酸根线性关系良好,线性相关系数分别为0.9998和0.9999,检测限分别为8.0×10-6μg/mL和5.0×10-5μg/mL,甲醛的加标回收率在95.8%~98.4%之间,乙二醛的加标回收率在96.8%~102.5%之间。该方法简便易行,且不使用有机溶剂,可为烟用纸张中甲醛和乙二醛的检测提供一种新的参考。     

流动注射化学发光法测定氨苄西林的研究

氨苄西林在NaOH溶液中降解后,其产物可在酸性条件下与KMnO4发生化学发光反应,甲醛的存在可使发光强度增强。据此,采用流动注射技术,建立了一种测定氨苄西林的化学发光分析法。方法的检出限为9.1×10-9g/mL,相对标准偏差为1.8%(n=11,ρ=3.4×10-6g/mL),线性范围为4.0×10-8~2.0×10-5g/mL。利用该法测定了氨苄西林胶囊中的氨苄西林,其回收率在87%~106%。     

电感耦合等离子体原子发射光谱法(ICP-AES)测定富铼渣中的铼

建立了电感耦合等离子体原子发射光谱法测定富铼渣中铼含量的方法。对样品的酸密闭消解、碱熔解和测定铼的条件进行了研究。结果表明:于盐酸(10%)介质、227.525nm分析线处,铼测定浓度在0.20~50.00μg/mL线性良好;两种样品分解方法测得铼结果吻合,用于富铼渣样品中1.85%~3.66%铼含量的测定,检出限、相对标准偏差(RSD,n=22)和加标回收率分别为酸密闭消解法6.46×10-10μg/mL,0.69%~1.1%和99.95%~100.1%,碱熔解法6.49×10-10μg/mL,0.69%~1.1%和99.96%~100.3%。     

微波消解-端视ICP-AES测定茶叶中微量重金属元素

采用微波消解-端视等离子体原子发射光谱(ICP-AES)测定茶叶中微量重金属元素Pb、As、Cd、Cu、Fe,并对ICP-AES工作参数及条件进行了优化和选择。Pb、As、Cd、Cu、Fe的检出限分别为2.9×10-3μg/mL、5.2×10-3μg/mL、0.056×10-3μg/mL、0.55×10-3μg/mL、0.59×10-3μg/mL,线性范围为0~10000μg/L,相对标准偏差为1.7%~8.5%;回收率为90%~104%。该方法与国标法比较,结果无显著性差异。本法能用于茶叶测定。     

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。     

火焰原子吸收光谱法测定铼产品中的痕量钠

建立了火焰原子吸收光谱法测定高铼酸、高铼酸铵、铼粉中痕量钠的方法,对样品的预处理和测定钠的条件进行了研究。结果表明:水溶解法、硝酸溶解法或硝酸-硫酸溶解法溶解样品完全,测得钠的结果吻合;于选定条件下,钠的测定浓度在0.020 0~0.500 0μg/mL范围内线性良好;测定高铼酸、高铼酸铵和铼粉样品中0.27~0.47mg/L、0.000047%~0.00048%和0.000040%~0.00049%的钠含量,检出限、相对标准偏差(RSD,n=7)、加标回收率分别为高铼酸3×10-4μg/mL、6%~10%、98%~102%,高铼酸铵3×10-4μg/mL、8%~9%、96%~102%和铼粉3×10-4μg/mL、5%~9%、96%~103%。方法结果准确、分析快速、操作简便,应用于实际的样品分析,结果满意。     

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.     

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.     

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.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Studies of Photoionization of CF3 I by Femtosecond Time-resolved Mass Spectrometry

The multi-photon dissociative photoionization dynamics of CF3I has been studied with femtosecond two-color pump-probe time of flight mass spectra at a pump pulse of 265 nm and a probe pulse of 398 nm. The life constants of CF3I+ and its fragment ions CF3+ and I+ are obtained as (96±7), (198±130) and (167±6)fs, respectively. The multi-photon dynamics leading to these ions differ. CF3I+ corresponds to a (1+2′) transition with one-photon pump excitation to the A band of CF3I. CF3+ are mainly formed by a tow-photon probe excitation to the CF3+ with subsequent dissociation of parent ions. I+ are produced in (2+2′) combined with (1+1′+2′) process. The results provide information on the multi-photon pathways involved.