Synthesis and phase separation of amine-functional temperature responsive copolymers based on poly(N-isopropylacrylamide)

Free radical copolymerizations of N-isopropyl acrylamide (NIPAM) and cationic N-(3-aminopropyl) methacrylamide hydrochloride (APMH) were investigated to prepare amine-functional temperature responsive copolymers. The reactivity ratios for NIPAM and APMH were evaluated in media of different ionic strength (r_NIPAM = 0.7 and r_APMH = 0.7-1.2). Phase separation behavior of the random copolymers with only 5 mol% of the APMH was found to be suppressed in pure water at temperatures up to 45 °C due to electrostatic repulsion among the cationic amine groups randomly distributed along the copolymer chain. Alternate sequential addition of PNIPAM/APMH mixtures and pure NIPAM was used to provide increased control of the location of APMH units along the chain. Consequently (close to) homo-PNIPAM block(s) were formed as evidenced by its characteristic phase transition at 33 °C. The influences of the monomer feeding time and feeding interval time to the APMH distribution were investigated to prepare copolymers with thermo-induced phase separation under physiologically relevant temperature and to determine the extent of conjugation to poly(ethylene oxide).     

NMR study of phase separation in D2O/ethanol solutions of poly(N-isopropylmethacrylamide) induced by solvent composition and temperature

¹H and ¹³C NMR spectroscopies were applied to investigate phase separation in solutions of poly(N-isopropylmethacrylamide) (PIPMAm) in D₂O/ethanol (EtOH) mixtures induced by solvent composition (cononsolvency) and temperature. Effects of EtOH content in D₂O/EtOH mixtures and temperature on the appearance and extent of the phase separation were characterized. Differences in mesoglobules formed during the phase separation induced by cononsolvency and temperature were found. For temperature-induced phase separation, ¹³C spin-spin relaxation times showed that besides the free EtOH expelled from the PIPMAm mesoglobules, there are also EtOH molecules bound in these mesoglobules. On the other hand, virtually no bound EtOH molecules were detected for mesoglobules formed as a consequence of the cononsolvency. For PIPMAm random copolymers containing negatively charged methacrylate units the phase separation induced by solvent composition was not observed.     

固相萃取-气相色谱-串联质谱法测定乳胶儿童用品中15种N-亚硝胺及其前体物的迁移量

建立了同时测定乳胶儿童用品中15种N-亚硝胺及其前体物迁移量的固相萃取-气相色谱-串联质谱(SPEGC-MS/MS)分析方法。以人工唾液作为迁移模拟物,以Chromabond Easy固相萃取柱(填料的主要成分是极性修饰的聚乙烯-二乙烯基苯共聚物)对迁移液中的N-亚硝胺分析物进行净化,采用HP-5 MS UI色谱柱分离,MS/MS在多反应监测模式下进行定性及定量分析。15种N-亚硝胺在5~2 000μg/L范围内呈良好的线性关系,相关系数均大于0.998;方法定量限(S/N=10)为0.625~12.50μg/kg,低于欧盟2 009/48/EC指令的限量要求。在低、中、高3个添加水平的回收率为53.8%~116.2%、52.7%~105.1%和49.5%~102.9%;日内精密度分别为1.3%~14.0%(n=6),日间精密度为1.6%~7.6%(n=4)。采用本方法对婴儿奶嘴样品和气球样品进行了测定,其中4件奶嘴和7件气球样品中检出亚硝胺及其前体物,奶嘴和气球中N-亚硝胺的总检出含量分别为0.049 9~0.126mg/kg和0.515~41.2 mg/kg;N-亚硝胺前体物总检出量分别为0.026 4~0.030 0 mg/kg和0.187~12.5mg/kg。     

固相萃取净化及超高效液相色谱-串联质谱法测定橡胶制品中的13种N-亚硝胺

建立了固相萃取(SPE)净化、超高效液相色谱-串联质谱(UHPLC-MS/MS)测定橡胶制品中13种N-亚硝胺的方法。样品于密闭萃取瓶中于60 ℃下用甲醇超声萃取30 min,C₁₈固相萃取小柱对萃取液进行净化,经C₁₈色谱柱分离,最后用电喷雾正离子(ESI⁺)和多重反应监测模式(MRM)对13种N-亚硝胺进行定性、定量测定。实验中对样品前处理、色谱分离条件和质谱检测条件进行了优化。在优化的实验条件下,橡胶样品中添加N-亚硝基二甲胺(NDMA)与N-亚硝基-二乙基胺(NDEA)为500 μg/kg、其他组分均为50 μg/kg时,各组分的相对标准偏差(RSD,n=7)小于10%;在实际样品中的加标回收率为70.7%~117.0%;方法的检出限(LOD,以10倍标准偏差计)为0.5~500 μg/kg。方法可应用于橡胶制品中13种N-亚硝胺的测定。     

固相萃取-超高效液相色谱-电喷雾串联质谱法同时检测尿样中的麻黄碱和N-甲基麻黄碱

建立了固相萃取-超高效液相色谱-电喷雾串联质谱(SPE-UPLC-ESI MS/MS)联用方法,定量测定尿样中的麻黄碱和N-甲基麻黄碱。样品经Oasis MCX柱提取、纯化和富集后,采用电喷雾(ESI)离子源电离,正离子多反应监测(MRM)模式质谱进行定性和定量分析。麻黄碱和N-甲基麻黄碱在0.0250~2.50 μg/L质量浓度范围内线性关系良好,线性相关系数分别为0.9998和0.9992,提取回收率高于80%,提取效率的RSD小于5.0%,检出限均达到0.01 μg/L,可大大延长尿样检材中麻黄碱和N-甲基麻黄碱的检测周期。结果表明,该方法快速、准确,为尿液中痕量麻黄碱和N-甲基麻黄碱的分析提供了灵敏的分析方法。     

Thermodynamic and spectroscopic study of the interaction of Cu(II), Ni(II), Zn(II) and Ca(II) ions with 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide,a pseudo-mimic of human serum albumin

The protonation equilibria of 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide ([H₂(556)–N]) and the complexation of this ligand with Cu(II) Ca(II), Zn(II) and Ni(II) have been studied by glass electrode potentiometry and UV–visible spectrophotometry. From pH ∼2.00–11.00, five models for Cu(II) with the following complexes; MLH, ML, MLH₋₁, MLH₋₂ and MLH₋₃ were generated and observed to describe the experimental data equally well as far as the statistical criteria were concerned. The MLH₋₂ complex predominates at physiological pH in all five models, while the MLH₋₁ complex species exists only at low concentration in two models. The coordination in the MLH₋₂ complex suggested the involvement of one amino, two deprotonated peptides and one pyridyl nitrogen atoms. Molecular mechanics (MM) calculations confirmed the MLH₋₂ complex as the most stable species. Speciation calculations, using a blood plasma model, predicted that the Cu(II)–[H₂(556)–N] complex is able to mobilize Cu(II). Octanol/water partition of CuLH₋₂ showed that 30% of the complex went into the octanol phase, hence promoting percutaneous absorption of copper. The complex is a poor mimic of native copper–zinc superoxide dismutase.     

Partitioning behaviour of organic compounds between ionic liquids and supercritical fluids

Applications and prospects of two-phase, tuneable solvent systems composed of ionic liquids (ILs) and supercritical fluids with an emphasis on supercritical carbon dioxide (scCO(2)) are reviewed. The IL-scCO(2) biphasic systems have increasingly been used in diverse fields of chemistry and technology, and some examples of these applications are mentioned here. Rational design of such applications can obviously benefit from pertinent data on phase equilibria including the partition coefficients of the prospective products and reactants between the two phases. Therefore, a reliable technique to measure the limiting partition coefficients would be of value. Here, the pros and cons of supercritical fluid chromatography in this respect are discussed. An overview of methods for predictive thermodynamic modelling of binary (IL-scCO(2)) and ternary (solute-IL-scCO(2)) systems is also included.