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首页> 外文期刊>Journal of Applied Polymer Science >A reinvestigation of a colorimetric method aimed at quantifying minute amounts of carboxylic acids present in polystyrene and poly(n-alkyl methacrylate)s
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A reinvestigation of a colorimetric method aimed at quantifying minute amounts of carboxylic acids present in polystyrene and poly(n-alkyl methacrylate)s

机译：测量法测量聚苯乙烯和聚（N-烷基丙烯酸正烷基酯）的微量羧酸的比较方法

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A reinvestigation of a method (Christoff, M.; Yamaki, S. B.; de Oliveira, M. G.; Atvars, T. D. Z. J. Appl. Polym. Sci. 2004, 92, 830-838) aimed at quantitatively determining trace amounts of residual carboxylic acid functional groups in polymethacrylates and polystyrene has been carried out. The original technique was based on the monitoring of an absorption band in the UV-visible region (610 nm) that appears after known amounts of polymer are added to a benzene solution containing the basic form of the Nile Blue A dye. It is shown here that the assumption upon which the methodology is based, that is, the occurrence of a 1:1 stoichiometric and complete proton transfer of the carboxylic acid to the dye, is invalid and yields greatly underestimated values for the COOH contents, possibly by 2-3 orders of magnitude. In addition, temperature strongly influences the equilibrium constant for the acid-base reaction. Lastly, preparation and storage of the analytical solution was found to be problematic, supporting earlier claims that hydrolysis of Nile Blue A base does occur when preparing the benzene solution and/or over storage, yielding Nile Red dye whose absorption in the visible part of the spectrum significantly overlaps. Based on the above results, further use of this technique, at least in its quantitative version, should be discouraged. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44931.
机译：一种方法（Christoff，M。; Yamaki，SB; De Oliveira，Mg; atvars，Tdzj Appl。Polym.SCI。2004,92,830-838）定量确定痕量的残留羧酸官能团。已经进行了聚甲基丙烯酸酯和聚苯乙烯。原始技术基于对UV可见区域（610nm）中的吸收带的监测，该吸收带在将已知量的聚合物加入到含有尼罗蓝色染料的基本形式的苯溶液中出现的。这里示出了方法基于的假设，即，将羧酸的1：1化化学计量和完全质子转移到染料中，是无效的，并且可能产生大量低估的CoOH含量的值达到2-3级数量级。此外，温度强烈影响酸碱反应的平衡常数。最后，发现分析溶液的制备和储存是有问题的，支持前面要求尼罗·蓝的水解在制备苯溶液和/或过度储存时会出现碱液，产生尼罗红染料，其在可见部分中的吸收光谱显着重叠。基于上述结果，应不鼓励进一步使用该技术，至少在其定量版本中，应不再核断。 （c）2017 Wiley期刊，Inc.J.Phill。聚合物。 SCI。 2017,134,44931。

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