The majority of water utilities currently employ the in-lab tests of the grabbed samples to determine the free chlorine (FC) residual levels. Under certain circumstances, such approaches are inadequate to timely and accurately reflect the dynamically changed FC residual levels, leading to inappropriate dosages. This work reports a uniquely configured membrane-based colorimetric flow-injection system (MCFIS) capable of accurately and reliably online monitoring drinking water FC residual levels in a rapid (1−5 min per measurement) fashion. The embedded gas-permeable membrane makes MCFIS an interference-free FC monitoring system. The developed pre-calibration strategy avoids the need for on-going calibration. The accuracy of the conventional analytical principles is almost exclusively determined by the absolute analytical signal value of one measurement data point, and any errors from such a single-data point measurement will be directly transferred to the result, which induces uncertainties, hence, poor accuracy and reliability. Differing distinctively from such conventional analytical principles, MCFIS quantifies chlorine concentration based on N, N-diethyl-p-phenylenediamine – Cl₂ colorimetric reaction-controlled membrane transport process that enables the determination of gaseous chlorine concentration according to multiple measurement data points to greatly enhance the accuracy and reliability. The inherent analytical features of this slope-based signal quantification principle, interference-free and on-going calibration-free empower MCFIS with an enormous superiority over other systems for online FC monitoring applications.

当前，大多数自来水公司都对所抓取的样品进行实验室测试，以确定游离氯（FC）的残留水平。在某些情况下，此类方法不足以及时准确地反映动态变化的FC残留水平，从而导致剂量不合适。这项工作报告了一种独特配置的基于膜的比色流动注射系统（MCFIS），该系统能够以快速（每次测量1-5分钟）的方式准确，可靠地在线监测饮用水中的FC残留量。嵌入式的透气膜使MCFIS成为无干扰的FC监控系统。制定的预校准策略避免了正在进行的校准。常规分析原理的准确性几乎完全由一个测量数据点的绝对分析信号值确定，并且来自这种单数据点测量的任何误差都将直接转移到结果中，从而导致不确定性，因此准确性较差和可靠性。与此类常规分析原理截然不同，MCFIS基于N，N-二乙基对苯二胺– Cl定量氯浓度₂比色反应控制的膜传输过程，能够根据多个测量数据点确定气态氯浓度，大大提高了准确性和可靠性。这种基于斜率的信号量化原理的固有分析功能，无干扰和持续进行的无校准功能使MCFIS相对于在线FC监控应用的其他系统具有巨大的优势。