1.1 本试验方法包括测定4-羧基苯甲醛（4-CBA）和 p -甲苯甲酸( p -通过毛细管电泳（CE）正常电压模式和紫外检测，在精对苯二甲酸（PTA）中。它适用于5至400 mg/kg的4-CBA和 p -TOL分别为10至400 mg/kg。 1.2 在使用该方法确定测试结果是否符合适用规范时，应根据修约方法对结果进行修约 E29年 . 1.3 以国际单位制表示的数值应视为标准值。 本标准不包括其他计量单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 4-CBA和 p -用于生产聚酯的PTA中的TOL是不可取的，因为它们会减慢聚合过程；由于热不稳定性，4-CBA也使聚合物着色。 5.2 确定4-CBA和 p -通常需要PTA制造过程中剩余的TOL。本试验方法适用于制定规范，并用作生产或使用这些产品的内部质量控制。 5.3 本试验方法旨在替代HPLC法测定4- CBA和 p -PTA中的TOL。CE的主要优点是速度快、简单、减少试剂消耗和操作成本。

1.1 This test method covers the determination of 4-carboxybenzaldehyde (4-CBA) and p -toluic acid ( p -TOL) in purified terephthalic acid (PTA) by capillary electrophoresis (CE) with normal voltage mode and UV detection. It is applicable for 4-CBA from 5 to 400 mg/kg and for p -TOL from 10 to 400 mg/kg, respectively. 1.2 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off in accordance with the rounding-off method of Practice E29 . 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 The presence of 4-CBA and p -TOL in PTA used for the production of polyester is undesirable because they can slow down the polymerization process; and 4-CBA is also imparting coloration to the polymer due to thermal instability. 5.2 Determining the amount of 4-CBA and p -TOL remaining from the manufacture of PTA is often required. This test method is suitable for setting specifications and for use as an internal quality control where these products are produced or used. 5.3 This test method is intended as an alternative to the HPLC method for determination of 4-CBA and p -TOL in PTA. The major benefits of CE are speed, simplicity, reduced reagent consumption and operating costs.