微波消解-电感耦合等离子体发射光谱法同时测定燃料油及润滑油中9种微量金属元素

本文建立了测定燃料油和润滑油样品中Al、Ba、Ca、Cu、Fe、Mg、Mn、Pb、Zn 9种微量金属元素的微波消解-电感耦合等离子体发射光谱法(ICP-OES)。实验探讨了油样的微波消解及ICP-OES测定条件。优化条件下方法加标回收率为93%~102%,相对标准偏差(RSD)3%(n=7)。该方法准确、灵敏,适用于燃料油和润滑油中微量金属元素的分析测定。     

微波消解-ICP-OES法测定汽车涂料中8种重金属

建立微波消解-电感耦合等离子体发射光谱(ICP-OES)测定汽车涂料中Pb,Cr,Se,Ba,Sb,As,Cd,Hg含量的方法。以HNO_3-H_2O_2(体积比为4∶1)混合酸消解样品,各元素分析谱线:Pb 220.353 nm,Cr 267.716 nm,Se196.090 nm,Ba 233.527 nm,Sb 217.581 nm,As 189.042 nm,Cd 228.802 nm,Hg 184.950 nm。8种元素测定结果的相对标准偏差为2.02%~12.94%(n=6);对白色、蓝色、红色汽车漆样品进行加标回收试验,Pb,Cr,Se,Ba,As,Cd,Hg,的加标回收率为81.26%~99.79%,Sb的回收率为62.43%~87.61%。该方法快速、简便,精密度、准确度较高,可用于汽车涂料中重金属含量的监控。     

微波消解-石墨炉原子吸收光谱法测定污水厂污泥和进、出水中的镉、铅

建立了微波消解–石墨炉原子吸收光谱法测定污水处理厂进出水和污泥中重金属Cd,Pb的方法。分别向污水样品中加入5.0 mL硝酸,污泥样品中加入4.0 mL硝酸和2.0 mL双氧水,放入微波消解炉中进行消解。消解好的样品用1%NH_4H_2PO_4作为基体改进剂,在0.5%HNO_3介质中采用塞曼扣除背景,石墨炉程序升温方式进行Cd,Pb的原子化,用石墨炉原子吸收光谱法测定Cd,Pb的含量。Cd,Pb的质量浓度分别在0~2.00μg/L,0~40.0μg/L范围内与其吸收峰高呈良好的线性关系,线性相关系数分别为0.999 1,0.999 6。Cd,Pb检出限分别为0.104 9,0.394 5μg/L,测定结果的相对标准偏差分别为1.34%~3.61%,2.12%~2.80%(n=11),加标回收率分别为98.2%~102.6%,94.0%~100.4%。该方法简单,高效,结果准确度高,重现性好,适用于污水处理厂的进出水和污泥中重金属铅和镉的检测。     

微波消解-石墨炉原子吸收光谱法测定鱼肉和河蚌中的重金属

建立微波消解样品,石墨炉原子吸收光谱法测定鱼肉和河蚌中重金属Pb,Cd,Cr,Cu,Ni含量的方法。优化了石墨炉原子吸收光谱法测定条件,在最佳实验条件下,选用磷酸二氢铵作为Pb,Cd,Cr,Cu的基体改进剂,抗坏血酸作为Ni的基体改进剂。Pb,Cd,Cr,Cu,Ni的检出限分别为0.05,0.01,0.05,0.05,0.07μg/g,实际样品测定结果的相对标准偏差为6.3%~14.5%(n=6),加标回收率为84.5%~113.0%。测定了牡蛎标准参考样,测定值在标准值可接受范围内。该方法检出限低、准确度高,适用于鱼类、河蚌样品中重金属含量的分析。     

A Facile and Cost‐effective Electroanalytical Strategy for the Quantification of Deoxyguanosine and Deoxyadenosine in Oligonucleotides Using Screen‐printed Graphite Electrodes

The development of electroanalytical methods for the detection and quantification of nucleotides in DNA offers vital implications in assessing the degree of oxidation or epigenetic modification in DNA. Unfortunately, the electrochemical response of oligonucleotides is strongly influenced by the size, composition and nucleic base sequence. In this article, an optimized analytical procedure for the enzymatically breakdown of the oligonucleotides to their corresponding nucleotides for the evaluation of the electrochemical response through the use of square wave voltammetry (SWV) is presented. Enzymatic digestion of oligonucleotides has been optimized in terms of buffer composition, digestion time, strategy for stopping the enzymatic reaction and filtration requirement for enzyme removal, and then compared to an established protocol. Under the optimized protocol SWV response of a number of untreated and enzymatically digested six‐mer oligonucleotides, namely 5′‐GGGGGG‐3′, 5′‐AAAAAA‐3′, 5′‐CGCGCG‐3′ and 5′‐AAACGC‐3′ have been analysed, providing a higher sensitivity for the determination of guanosine and adenosine monophosphate species under digestion conditions with a more facile and cost effective procedure. The novel strategy for the enzymatically treated oligonucleotides in combination with the SWV response provides a proof of principle for feasible applications in the diagnosis of methylated guanosine in DNA as a potential biomarker due to its relation with cancer.     

CuI-catalyzed domino reactions for the synthesis of benzoxazine-fused isoquinolines under microwave irradiation

A small library of benzoxazine-fused isoquinolines has been synthesized under microwave irradiation (MW) via CuI-catalyzed domino reactions of o-alkynyl aldehydes and amines having embedded nucleophiles. This strategy offers a operationally simple, environmentally acceptable route to synthesize benzoxazine-fused isoquinolines in moderate to good yields. All new compounds were characterized by ¹H NMR, ¹³C NMR, infrared, and high-resolution mass spectrometry techniques.     

Sustainable Diels–Alder syntheses in imidazolium ionic liquids

An effective and simple protocol for the Diels–Alder reactions catalyzed and mediated by ionic liquid in conjunction with Lewis acid was studied. Diels–Alder adduct of the reaction of 1,4-benzoquinone with isoprene and 2,3-dimethyl-1,3-butadiene was obtained in good to excellent yields within the time span of 5.00–4.00 min under microwave irradiation. Due to the excellent activity of 2,3-dimethyl-1,3-butadiene as a diene, its efficiency was further analyzed by performing against four different dienophiles under various reaction conditions. The ionic liquid, 3-methyl-1-octyl-imidazolium tetrachloroaluminate mixed with Lewis acids, could be recycled and reused for consecutive cycles. The recovered ionic liquid in conjunction with Lewis acid displayed almost similar activity without any significant loss. This system is an essential upgrade and related to the reactions consuming common organic solvents at high temperatures and longer duration. Diels–Alder reactions under solventless conditions have also been investigated for the aforesaid reactions.     

Efficient and rapid synthesis of phenolic analogs of 4-phenylbutanoic acid using microwave-assisted Michael addition as a key reaction

The addition of phenols to acrylonitrile in the presence of aqueous benzyltrimethylammonium hydroxide or tetramethylammonium hydroxide under microwave irradiation yielded the corresponding Michael adducts. The obtained adducts were easily transformed to phenolic analogs of 4-phenylbutanoic acids via the hydrolysis of nitrile groups.     

Microwave-assisted synthesis of dialkyl ω-azidoalkylphosphonates

An efficient and reproducible microwave-assisted synthesis of dialkyl ω-azidoalkylphosphonates via nucleophilic substitution of the appropriate dialkyl ω-bromoalkylphosphonates by sodium azide in water or dimethylformamide (DMF) as solvent has been developed. This process has been optimized for batch reactors. The target, structurally diverse dialkyl ω-azidoalkylphosphonates with different steric hindrance around the phosphonato groups and containing unbranched side carbon chains of different lengths (n?=?2–6), has been obtained in moderate to high yields (39–87%).