兩段式脈衝安培法應用於自由氯感測

Abstract

本研究使用未經修飾之白金電極搭配最佳化的兩段式脈衝安培法，成功的開發一套適用於非流動系統中的自由氯濃度感測方法。透過參數最佳化的過程找出最佳的量測電位為1.05 V、還原電位為 -8.5 V、電位施加時間則為350 ms而訊號之積分時間則為50 ms。 兩段式脈衝安培法應用於自由氯感測相較於定電位量測法有較高的量測再現性，其相對標準差多小於1%（n = 6）。在以0.1 M NaCl溶液為背景之次氯酸溶液中，其感測之積分電量與自由氯濃度於25 ~ 1100 ppm間有良好的線性關係（R2 = 0.9908）。 在本研究中亦以此方法開發一台自由氯感測器，為對其準確度進行測試，分別以此感測器與市售自由氯量測儀量測（HI9734, Hanna）對以0.15 M氯化鈉電解製成的多種不同自由氯濃度之待測樣本進行量測，其結果顯示此感測器之量測結果與HI9734自由氯量測儀量測之結果有不錯的一致性（R2 = 0.9976），且每筆量測僅需3.5秒即可完成。此感測器適用於電解固定濃度氯化鈉溶液之無隔膜電解水機，可讓使用者即時了解電解水之產製情形。

Using unmodified / unpolished / no-pretreatment platinum as electrode, the two-step pulsed amperometric method was used for the quantitative determination of the concentration of free available chlorine (FAC) in a non-flow condition. Subject to the related experimental setup, the optimum operating conditions were determined. They are: detection potential (Edet) at 1.05 V, reduction potential (Ered) at -0.85 V, detection and reduction time both at 350 ms and the integrated duration is 50 ms before the switch of the period applying detection potential to the period applying reduction potential. Comparing with the traditional single step amperometic detection method, the method developed shows much better reproducibility, demonstrated by the R.S.D. at 1 % (n = 6). A linear relationship (R2 = 0.9908) between Integrated signals of electrons and FAC concentration was found within the range of 25 - 1100 ppm FAC concentration in 0.1 M NaCl solution with NaOCl as additive. An FAC sensing system was developed based on this study, then was compared with a commercially available FAC sensing equipment (HI9734, Hanna) which based on DPD colorimetric method. The results first show that both systems have good consistency (R2 = 0.9976). In addition, the system developed shows several advance features, such as much less measuring time required (3.5 seconds), easy to operate, wider FAC measuring range and operational risk-free sue to no chemical needed. One major drawback of the current system developed was that the calibration is needed for different salt concentration. This is the work still need to be done to make the system more flexible to use.