Tetramethylbenzidine method for monitoring the free available chlorine and microbicidal activity of chlorite-based sanitizers under organic-matter-rich environments

Abstract

For practical applications of chlorine in food processing, monitoring of FAC is critical to validate disinfection efficacy. In this study we found that chlorite-based sanitizers acquired a pink colour upon contact with BSA or broiler carcasses. This pink colour interfered with FAC monitoring by methods that measure oxidized N,N-diethyl-p-phenylenediamine absorbance between 513-550 nm. Alternatively, FAC levels of chlorite-based sanitizers could be monitored using the absorbance of 3,3',5,5'-tetramethylbenzidine at 650 nm, which does not overlap with the acquired pink colour. These data provide valuable information for safety management of disinfection processes that use chlorite-based sanitizers.

Microbicidal effects of weakly acidified chlorous acid water against feline calicivirus and Clostridium difficile spores under protein-rich conditions

“…FAC levels of WACAW were calculated from standard curves generated with NaClO. The FAC levels of the test sanitizers after contact with organic substances were monitored by TMB method as previously described [27]. Combined chlorine level was calculated by subtracting FAC from TC.…”

“…HClO 2 -based sanitizers have been reported to be more stable than NaClO under organic-matter-rich conditions [24, 26, 27]. They contain various forms of chlorinated oxides such as HClO 2 , dissolved ClO 2 and ClO 2 - , and the former two are responsible for most of the microbicidal activity of WACAW.…”

3,3′,5,5′-tetramethylbenzidine as multi-colorimetric indicator of chlorine in water in line with health guideline values

“…Consequently, the reactions reported in Fig. 1 have been used for quantitative measurements of chlorine in water [21][22][23][24][25], under organic matter-rich conditions [26], or generated by myeloperoxidase of neutrophils [27][28][29], reaching an enhanced degree of automation and reduced reagent consumption and waste production [23]. All the species reported in Fig.1, obtained in water and other solvents, by enzymatic, chemical, or electrochemical oxidation, have been detected and characterized elsewhere by optical spectroscopy, electron spin resonance spectroscopy, and resonance Raman scattering spectroscopy [15,16,18,19,24,25].…”

“…Therefore, we have performed experiments stabilizing TMB solution at pH 4.5 with diphosphate salts (see Materials and method), thus preventing interference from redox-active ions like Fe(III) potentially present in water supply systems, as elsewhere demonstrated by extensive interference studies [21][22][23][24]. Differently from previously reported single-color intensity estimation with TMB (either yellow or blue) or DPD (magenta) [21][22][23][24][25][26]29], this method allows the naked-eye quantification of chlorine by multi-color changes of TMB solution. This approach for the first time proposes TMB as a universal indicator for the selected range of chlorine concentrations, from a minimum blue level for effective disinfection, through an optimal green level, up to the safe yellow guideline level corresponding to equimolar chlorine and TMB (see below).…”

Investigation of the Effective Concentration of Ozonated Water for Disinfection in the Presence of Protein Contaminants

“…We next examined the inhibitory effect of contaminants on the antimicrobial activity of OW. Among numerous contaminants, we selected BSA Wako Pure Chemical Industries, Ltd., Japan because it is commonly found as a contaminant when testing the efficacy of sanitizers Yamaoka et al, 2016 . The antibacterial activity of OW in the presence of BSA was measured using E. coli as a model of a gram-negative bacterium and S. aureus as a model of a gram-positive bacterium.…”