Simple and Selective Determination of Free Chlorine in Aqueous Solutions by an Electrophilic Aromatic Substitution Reaction Followed by Liquid Chromatography Coupled with Mass Spectrometry

Simple and Selective Determination of Free Chlorine in Aqueous Solutions by an Electrophilic Aromatic Substitution Reaction Followed by Liquid Chromatography Coupled with Mass Spectrometry

We developed a selective technique to rapidly measure free chlorine, which is the sum of elemental chlorine (Cl<sub>2</sub>), hypochlorous acid (HOCl), and hypochlorite (OCl<sup>−</sup>) in water samples via an electrophilic aromatic substitution reaction hyphenated with liqu...

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Bibliographic Details
Main Authors: Avital Shifrovitch, Moran Madmon, Tamar Shamai Yamin, Avi Weissberg
Format: Article
Language:English
Published: MDPI AG 2024-12-01
Series:Organics
Subjects:
free chlorine
aqueous media
derivatization
electrophilic aromatic substitution
LC-ESI-MS/MS
Online Access:https://www.mdpi.com/2673-401X/5/4/32
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Summary:We developed a selective technique to rapidly measure free chlorine, which is the sum of elemental chlorine (Cl<sub>2</sub>), hypochlorous acid (HOCl), and hypochlorite (OCl<sup>−</sup>) in water samples via an electrophilic aromatic substitution reaction hyphenated with liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Sample preparation involved derivatization at 25 °C for 15 min with 3,4,5-trimethoxyphenylacetic acid (TMPAA) in an aqueous solution prior to analysis. Several parameters were evaluated to determine the optimized reaction and for the production of informative MS/MS spectrum of the derivatization product, 2-chloro-3,4,5-trimethoxyphenylacetic acid (Cl-TMPAA). The resulting Cl-TMPAA derivative displayed an informative ESI-MS/MS spectrum characterized by product ions at <i>m</i>/<i>z</i> 232.0142, 200.0245, and 185.0009 from the precursor ion at <i>m</i>/<i>z</i> 259.0379. The linear dynamic range of the method (0.1–10 µg/mL) was fitted to concentration levels relevant to forensic toxicology issues. Compared with other analytical techniques, this newly established LC-MS-based method demonstrated specificity, simplicity, and rapidity. This method enables the detection of free chlorine for forensic investigations in criminal cases.
ISSN:2673-401X

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