Applying Two-step Pulsed Amperometric Detection Method in FAC Sensing
Date Issued
2011
Date
2011
Author(s)
Chen, Hsiang-Han
Abstract
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.
Subjects
electrolyzed water
free available chlorine
two-step pulsed amperometric
platinum electrode
Type
thesis
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