# Halogenation of Dissolved Organic Matter: A New Methodology To Quantify and Characterize Bromine and Iodine Incorporation

Mohamad Shalak, David Dumoulin, Pierre-Jean Superville, Justine Criquet

<figure><img src="image_1.png" /></figure>

## To cite this version:

Mohamad Shalak, David Dumoulin, Pierre-Jean Superville, Justine Criquet. Halogenation of Dissolved Organic Matter: A New Methodology To Quantify and Characterize Bromine and Iodine Incorporation. ACS ES&T Water, 2025, 10.1021/acsestwater.5c00751. hal-05288415

HAL Id: hal-05288415

https://lilloa.hal.science/hal-05288415v1

Submitted on 29 Sep 2025

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
1

Halogenation of dissolved organic matter: new methodology to quantify and characterize bromine and iodine incorporation

2

3

4

Mohamad Shalakª, David Dumoulinª, Pierre-Jean Supervilleª and Justine Criquetª,ᵇ,*

5

6

ª Univ. Lille, CNRS, UMR 8516 - LASIRE, Laboratory of Advanced Spectroscopy for Interactions, Reactivity and Environment, Lille F-59000, France

7

ᵇ Institut Universitaire de France

8

9

10

11

12

*Corresponding author : justine.criquet@univ-lille.fr

Université de Lille, Cité Scientifique Bâtiment C8

59655 Villeneuve d'Ascq - France

13

Abstract

14

15

16

17

18

19

20

21

22

23

24

25

26

During chlorination process, a major pathway of by-product formation is the incorporation of halogen to organic matter We developed a methodology based on the coupling of a size exclusion chromatography (LC-SEC) coupled to an elemental detector (ICP-MS) allowing the quantification of organic iodine and bromine bounded to organic matter large molecules (humic substances and building blocks or higher) down to 0.6 and 7.5 µg L⁻¹ for iodine and bromine respectively by direct injection of water sample without pretreatment. The application of this methodology showed that the incorporation of halogens to organic matter large molecules reaches a maximum while the total organic halogenation still increases. The concentration of halogenation sites is estimated to be 1.4 µmol per mg of carbon for the Suwannee River Natural Organic Matter corresponding to the possibility to incorporate into the complex structure either 50 or 110 of bromine and iodine respectively per mg of C. The organic bounded halogens have been found to not be stable to reducing agents; ascorbic acid and sulfite leads to a decrease up to 20% of the organic- bromine or iodine concentrations. Similarly, basic conditions degrade the structure.

27

**Keywords:** bromine, iodine, natural organic matter, oxidation, ICP-MS

28

29

Synopsis:

30

31

A novel methodology allows the quantification of bromine and iodine incorporation to complex organic molecules without any pre-treatment of the aqueous sample.

32

33

1. Introduction
Chlorine based chemicals are widely used to disinfect drinking- and waste-waters with hypochlorite solution ($ClO^{-}$, $Na^{+}$), the main chemical used worldwide. The reaction of the active oxidative species, hypochlorite ($ClO^{-}$) and hypochlorous acid ($HOCl$) with organic matter leads to the formation of chlorinated by-products. In presence of even small amounts of bromide or iodide, the corresponding hypohalous acid ($HOX$) and hypohalite ($XO^{-}$) are formed, followed by the formation of a mix of chlorinated/brominated and iodinated disinfection by-products (DBPs) $1-3$. These species can also be formed by using other oxidants such as ozone and monochloramine. While chloramination has been adopted in the past to avoid the formation of the regulated DBPs, i.e. chlorinated and brominated trihalomethanes as well as haloacetic acids, this oxidation process enhances the formation of iodinated disinfection by-products $4-6$. The brominated and iodinated oxidative species are more reactive towards organic compounds compared to chlorine, favouring the formation of brominated and iodinated disinfection by-products. Bromine has been found to be 3000 times more reactive towards phenolic structures compared to chlorine $7$ while iodine has an intermediate reactivity more impacted by the substituents in chemical structures $8$. The formation of DBPs and especially brominated and iodinated compounds is of concern due to their toxicity increasing in the order $Cl<Br<l^{9-12}$.

It has been shown that bromine and chlorine react with phenolic compounds and organic matter by electrophilic (aromatic) substitution and/or oxidation leading in the latter case to the release of halide ions in solution $^{13}$. In that study, a 20% molar bromine incorporation was determined for different organic matter extracts by the reaction of hypobromous acid ($HOBr$) with an excess of target compounds, but different oxidant/organic matter ratio and the release of halides in solutions that could result to a higher incorporation of halides into organic matter were not studied. The bromine incorporation factor (BIF), as the amount of bromine incorporated into DBPs, is a usual parameter calculated in literature and can vary from 10 to 30 % $^{14,15}$. Most of disinfection by-products formed are unknown and are estimated from the analysis of organic bonded halogens, with AOX (Adsorbable Organic Halogen) being used as an acceptable proxy. The individual DBPs analysed account for various proportion of the AOX formed in chlorination process (28-72%), this proportion being lower for chloramination process (13-27%) $^{16}$. However, this commonly used method to quantify AOX is time consuming, lacks accuracy, and does not provide information on the nature of the compounds analyzed. Moreover, depending on the method applied (column vs. batch adsorption), halogenated compounds present on activated carbon can only be partially recovered $^{17,18}$. Recently, researchers have used the difference between total halogen and halides concentrations to estimate organic halogen fractions $^{19-21}$. However, this methodology is not suitable when large amounts of halides are present compared to the organic fractions, especially for chlorine speciation.
Coupling of chromatographic methods with elemental tools such as ICP-MS (Inductively Coupled Plasma Mass Spectrometry) is increasingly common in laboratories, mainly for the application of trace metal speciation <sup>25-28,23</sup> and occasionally for halide speciation <sup>29-31</sup>. For example, ion chromatography coupled with ICP-MS provides a very sensitive method for bromide, iodide, bromate and iodate analysis below the µg L<sup>-1</sup> level <sup>31</sup>. This technique has also been applied with size exclusion chromatography (SEC) to perform iodine speciation, but it was limited to relatively high concentrations and only inorganic iodine was detected <sup>30</sup>. Organic-iodine was still determined from the difference with total iodine concentration from a second analysis.

The present study describes a methodology based on organic matter separation by size exclusion chromatography coupled with an ICP-MS as detector to investigate the incorporation of halides into organic matter complex matrices. The assessment of the halogenation of an extract of standardized natural organic matter and of natural water samples was studied in different conditions in order to characterize the formation of complex disinfection by-products but also to characterise the organic matter and its behaviour towards halogenation.

81

82

## 2. Material and Methods

83

84

### 2.1. Chemicals and reagents

Ultra-pure Milli-Q water (Millipore, 18.2 MΩ·cm at 25°C) was used to prepare the reagents and standards. An organic matter reference material (humic substance extracted from the Suwannee river, referred as SRNOM) from the International Humic Substances Society (IHSS) was used. Fresh organic matter solutions were prepared introducing around 5 mg of SRNOM-type humic substance into 100 mL of ultra-pure water. The pH of the mixture was first adjusted to approximately 10 by adding aliquots of a 2M sodium hydroxide solution to ensure the complete dissolution of the organic matter <sup>32</sup>. After complete dissolution of the organic matter, 1M sulfuric acid was added to adjust the pH of the solution to 8. No precipitation or turbidity was observed after pH adjustment to 8, confirming that the dissolved organic matter remained in solution. The organic carbon concentration of this solution was determined using a Total Organic Carbon (TOC) analyzer (Shimadzu, TOC VCSH) from a solution diluted by a factor of 10.

Sodium hypochlorite was supplied by Honeywell (approximate concentration 15 % w/v). The exact concentration of hypochlorite ions (ClO<sup>-</sup>) in this solution was frequently determined by measuring its absorbance at 295 nm (ε<sub>295nm</sub> = 357 L M<sup>-1</sup> cm<sup>-1</sup>). HOBr solutions (0.1 M) were prepared from a

97

98
99 stoichiometric mix of sodium hypochlorite and potassium bromide (Fisher Scientific). The 100 concentrations of these solutions were determined at pH 11 measuring the absorbance of BrO⁻ at 329 101 nm (ε₃₂₉nm = 332 L M⁻¹·cm⁻¹) ³³. The hypoiodous acid HOI solutions were prepared through the 102 chloramination of iodide solutions. To produce chloramines, 134 mg of NH₄Cl was added to a 50 mL 103 flask to achieve a concentration of 25 mM. The required amount of hypochlorite was then added (1:1 104 stoichiometric concentration, ensuring completion of the reaction without additional ammonia in 105 solution) slowly with vigorous stirring to achieve a final solution concentration of 25 mM ³⁴,³⁵. The 106 concentration of monochloramine and the absence of detectable dichloramine were checked by 107 measuring the absorbances at 254 nm and 294 nm (εNH₂Cl, 254 nm = 369 M⁻¹ cm⁻¹; εNH₂Cl, 294 nm = 15 M⁻¹ cm⁻¹; εNHCl₂, 254 nm = 136 M⁻¹ cm⁻¹; εNHCl₂, 294 nm = 289 M⁻¹ cm⁻¹). To prepare a solution 108 containing 100 µM HOI, a KI solution was added to the chloramine solution in pH 8 phosphate buffer 109 (5 mM), ensuring rapid mixing. The concentration of HOI was monitored using the DPD (N,N-diethyl- 110 *p*-phenylenediamine) method ³⁶. Sodium diatrizoate 99% (Acros organics) and 4-bromophenylacetic 111 acid 99% (Alfa Aesar) were respectively used as iodine and bromine standards for organic halogen 112 analysis. 113

114 2.2. Instrumentation

115 Two High Pressure Liquid Chromatography (HPLC) systems were used for the analytical development. 116 A HPLC-UV system (1260 Infinity II, Agilent Technologies), equipped with a binary pump and a diode 117 array detector (DAD), was used to characterise organic matter separation by measuring its absorbance 118 at 254 nm. Detailed HPLC-UV operating conditions are presented in SI Table S.1. A HPLC (Bio-inert 1260 119 Infinity II, Agilent Technologies), equipped with a quaternary pump, was coupled to a single 120 quadrupole ICP-MS (7900, Agilent Technologies) for the analysis of inorganic and organic halogen 121 species. The same Agilent size exclusion column (SEC-3 µm, 100 Å, 7.8 x 300 mm) was used in both 122 cases using phosphate buffer solution (1 g L⁻¹) as mobile phase at 0.8 mL/min. The eluent was prepared 123 from 0.5 g L⁻¹ K₂HPO₄ and 0.5 g L⁻¹ KH₂PO₄ at pH = 6.6. Although phosphate buffer concentrations of up 124 to 3 g L⁻¹ are often used for organic matter separation ³⁷, the concentration was here limited to 1 g L⁻¹ 125 to prevent premature ICP-MS fouling leading to signal drifts. In addition, a Dionex IonPac AS16 ion 126 chromatography column (2 x 250 mm) was used for the speciation and quantification of inorganic 127 bromine and iodine on the IC-ICP-MS instrument, with gradient elution ranging from 10 to 20 mM 128 NaOH. The concentrations of inorganic iodine and bromine species were determined using iodide, 129 iodate and bromide standards prepared from 1 g L⁻¹ certified solutions (SCP SCIENCE) ³¹. The 130 chromatograms resulting from IC-ICP-MS are presented in Fig. S1. Additionally, the total 131 concentrations of halogens were determined by direct injection to single quadrupole ICP-MS (Agilent 132 7850) using aqueous tetramethylammonium hydroxide (TMAH, 0.1 % w/v) as solvent. All ICP-MS
measurements were carried out by monitoring the signal intensity at m/z 79, 81 and 127 ($^{79}$Br, $^{81}$Br and $^{127}$I, respectively). The measurements of bromine and iodine were performed in two separate runs because kinetic energy discrimination and He as collision gas were used to handle polyatomic interferences for bromine analysis. The instrumental conditions for SEC-ICP-MS and IC-ICP-MS are presented in SI Table S.2. Integration of the chromatographic peaks was performed using Origin software (OriginLab, Northampton, USA). For the natural water samples, when partial overlap between organic iodine and inorganic iodine species was observed, peak deconvolution was applied using Origin software to resolve the contribution of organic iodine. The deconvolution procedure consisted of a Gaussian fitting of overlapping peaks in the retention window of interest.

142

2.3. Sample treatment and determination of mass balance

144

Halogenation reactions of organic matter (SRNOM) were conducted using HOBr and HOI as oxidants at different doses. The SRNOM organic matter solutions at 5.3 mgC L⁻¹ were prepared by dilution of a stock solution in 5 mM phosphate buffer (pH 8). Subsequently, the samples were treated with small volumes of oxidants stock solution to achieve final concentrations of HOBr from 1 to 120 µM and HOI from 1 to 20 µM (HOI stock solution and therefore oxidant dose has been limited to avoid the degradation of HOI by disproportionation⁴). Most of halogenation tests were conducted 3 to 5 times to evaluate repeatability. Water samples were collected from the Blankaart reservoir in Belgium (Oct. 2023). Samples were filtered using a 0.45-micrometer polytetrafluoroethylene (PTFE) membrane filter and analyzed by TOC-meter to determine their dissolved organic carbon concentrations. Samples were then buffered at pH 8 by dilution with phosphate solution, resulting in a final concentration of 4.8 mgC L⁻¹ to mimic the halogenation conditions applied to organic matter extract. Halogenations were carried out using solutions of HOI and HOBr at increasing applied dose ranging from 1 to 20 µM. These oxidant doses represent a range from 0.07 to 0.38 mgCl₂/mgC equivalent demand, assuming complete oxidant consumption. The resulting background bromide and iodide concentration are 106 and 14 µg/L respectively.

In order to perform mass balances, the concentrations of the total amount of organic species of bromine and iodine were determined by the subtraction of the inorganic fraction from the total halogen concentration according to equation 1.

$$X_{\text{organic}} = X_{\text{total}} - X_{\text{inorganic}} \quad \text{(where X being Br or I) (Eq. 1)}$$

Where, Xtotal is the total molar concentration of Br or I determined by direct sample introduction in ICP-MS, Xinorganic the inorganic molar concentrations of bromine as bromide (no bromate formation
166 was observed) or iodine (sum of I⁻ + IO₃⁻) determined by ion chromatography coupled to ICP-MS
167 detector (IC-ICP-MS) and X organic the concentration of Br or I associated with an organic structure.

168

169 2.4. Detection and quantification limits of the SEC-ICP-MS method

170

171 To determine the detection and quantification limits of the SEC-ICP-MS method for analyzing bromine
172 and iodine signals associated with organic matter, ten blank samples consisting of ultrapure water
173 from different batches were processed. Signal integrations were carried out in the same time window
174 as that in which halogenated organic matter is eluted. The average peak area of these ten blank
175 samples was then transformed into a concentration from the standardization curve. This concentration
176 from baseline integration was multiplied by 3 to determine the detection limits and by 9 for
177 quantification limits ³⁸. A second method was used to confirm these results where halogenation was
178 performed on SRNOM solutions treated with HOBr or HOI separately. The concentrations of
179 incorporated bromine and iodine were determined by analyzing the samples with SEC-ICP-MS. These
180 solutions were then diluted to achieve concentrations close to the limits determined by the previous
181 method. Each solution was analyzed in quadruplicate. An acceptable coefficient of variation of 15% for
182 the limit of detection, and 5% for the limit of quantification was considered. These values, set here
183 arbitrarily, reflect a good balance between sensitivity and precision. At the limit of detection, the signal
184 is close to the instrumental noise and a higher variability is expected. A variation of 15% or less ensures
185 that low-level signals are reliably detected while taking this uncertainty into account. At the limit of
186 quantification, the objective is to guarantee accurate and reproducible measurements. A stricter
187 threshold of 5% variation provides confidence in the consistency of the measured values. These
188 thresholds are even lower than the 20% sometimes used in trace-level inductively coupled plasma
189 mass spectrometry analyses to validate the reliability of results near method limits ³⁹,⁴⁰.

190

191 3. Results

192

193 3.1. Method development and characterization

194 Prepared aqueous extracts of Suwannee River NOM have been treated by pre-formed HOBr or HOI
195 solutions according to the protocols detailed in section 2.3. The analysis of dissolved organic matter
196 extract samples treated with HOBr using SEC-ICP-MS shows two chromatographic peaks (Fig. 1a). The
197 first peak observed at 7.5 minutes corresponds to the incorporation of bromine into the organic matter
198 (Br-Org). The elution time of organic matter is confirmed by comparing the retention times of the
organic standards obtained by HPLC-ICP-MS and HPLC-UV. The second peak (10.2 min) corresponds to the retention time of bromide ions (confirmed by bromide standard injection).

Considering the organic matter samples treated by HOI, three chromatographic peaks were obtained and identified (Fig. 1b). Peak 1 corresponds to organic matter containing iodine (I-Org) at a similar retention time to that of Br-Org. To determine the identity of the two remaining peaks, iodide and iodate standard solutions were injected; the results confirm that peak 2, with a retention time of 9.2 minutes, corresponds to the iodate ion, while peak 3, with a retention time of 10.5 minutes, corresponds to the smaller iodide ion. Despite the specific conditions applied for the selective formation of hypoiodous acid from the reaction between monochloramine and iodide, a substantial quantity of iodate ions was present in the HOI stock solution due to the disproportionation reaction of HOI⁴. The SEC column provides a quite good efficiency to separate organic and inorganic substances within a relatively short retention time and narrow peaks compared to the published methods for NOM characterization ³⁷,⁴¹. The 100 Å pore size is the smallest currently available which has been developed for the separation of small peptides and proteins.

<figure><img src="image_3.png" /><figcaption>Fig. 1: SEC-ICP-MS chromatograms obtained for the analysis of 5.3 mgC L⁻¹ SRNOM organic matter solutions halogenated by increasing doses of (a) HOBr, (b) HOI (phosphate buffer pH 8). Retention times corresponding to (a) 1: Org-Br; 2: bromide; (b) 1: Org-I; 2: iodate; 3: iodide.</figcaption></figure>

In order to quantify organic halogenated species, 4-bromophenylacetic acid and sodium diatrizoate were selected as standards for bromine and iodine signals, respectively. Several simple halogenated organic compounds, such as bromo- and iodo- phenols, were tested as standards, but were not eluted and were therefore not suitable as SEC columns has difficulty eluting hydrophobic compounds ⁴². Sodium diatrizoate showed a retention time of 10.5 min, while 4-bromophenylacetic acid was eluted at 15.5 min, the gaussian form of the peaks and their relatively low width demonstrate their suitability as standards (Fig. S2). Both gave linear responses with increasing concentrations up to 250 µg L⁻¹ halogen equivalent.
The limits of the method were first determined by the integration of 10 ultrapure water samples performed over different days. The best sensitivity was obtained for organic iodine with a limit of detection of 0.2 µg L⁻¹ and a quantification limit of 0.6 µg L⁻¹. In the case of bromine, the detection limit was 2.5 µg L⁻¹ and the quantification limit was 7.5 µg L⁻¹. Dilutions of samples obtained from halogenation of the SRNOM organic matter extract down to these detection and quantification limits were performed to further validate these values. The halogenated samples were analyzed in quadruplicate, and the percentage deviation between experimental and theoretical results was determined. A deviation below 15% and 5% have been obtained for detection and quantification limits respectively, thus validating the sensitivity parameters for organic bromine and iodine (Table S.3). Repeatability tests for halogenation were also conducted on various samples with different doses of HOI and HOBr. The results demonstrated excellent repeatability in terms of halogen incorporation protocol and analysis by SEC-ICP-MS, with relative standard deviations among replicates ranging from 2 to 4% (Table S.4) either from same or different tests on different days. The bromine results were obtained by monitoring the signal of the bromine isotope ⁷⁹Br. The integration of ⁸¹Br signal shows that standard deviation between both signals was less than 2%, reinforcing the reliability of the obtained data. The difference in sensitivity between iodine and bromine is mainly explained by their ionization potential (iodine = 10.45 eV, bromine = 11.81 eV) ⁴³,⁴⁴.

242

243

### 3.2. Application to a natural organic matter extract

After method validation, various halogenation tests were conducted on a standardized natural organic matter (SRNOM) using different doses of HOBr and HOI, ranging from 1 to 120 µM, in order to study the halogen incorporation and its evolution as a function of the oxidant/organic matter ratio. Criquet et al. (2015) demonstrated that the phenolic structures as well as natural organic matter react with HOBr either by electron transfer or by electrophilic (aromatic) substitution (EAS), EAS accounting for around 20% for most of organic matter extract tested ¹³. This result was obtained in presence of a large excess of organic structure compared to oxidant in order to characterize the first possible reactions. Here, we explore different oxidant/organic matter ratios to further characterize the reactivity of both HOBr and HOI and assess the possible halogenation sites.

Considering bromine, oxidant doses from 0.2 to 23 µmol HOBr per mgC (corresponding to concentrations from 1 to 120 µM of oxidant added to a 5.3 mgC L⁻¹ Suwannee River NOM solution) were applied. The quantity of incorporated bromine increases linearly at low oxidant doses up to approximately 2 µmol/mgC, then followed by a slower increase at higher doses (Fig. 2). No residual concentration of oxidant was noticed (by DPD analysis) for doses below 10 µmol/mgC. The carbon concentration corresponds to a maximum of 70 µM of aromatic structure equivalent (organic carbon

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258
concentration divided by the mass of 6 carbons for a benzenic ring) ensuring the total oxidant consumption for most of the conditions. The oxidant demand has been assessed to be around 17 µmol oxidant/mgC, (dose from which a residual oxidant is observed) corresponding to an equivalent of 1.2 to 1.3 mgCl₂/mgC consumption after 24h reaction time. The experimental procedure to obtain HOI stock solutions limits the possible range of oxidant concentration for iodine (Cf. section 2.3). However, on the oxidant range tested (up to 3.8 µmol oxidant/mgC) iodine shows an increase of incorporation similar to bromine (Fig. 2).

<figure><img src="image_4.png" /><figcaption>Fig. 2: Evolution of the quantity of halogen incorporated into the organic matter matrix in function of the oxidant dose. Suwannee River NOM 5.3 mgC L⁻¹, pH8, [HOX] from 1 to 120 µM. Error bars correspond to the variance of four independent repetitions.</figcaption></figure>

The resulting percentages of incorporation of bromine and iodine (quantity incorporated compared to the applied oxidant dose) varies depending on the dose of HOX introduced. As shown in Fig. S.3, the percentage of bromine and iodine incorporated on this organic matter continuously decreases as the dose of HOBr and HOI introduced increases; from around 30% for 0.2 µmol/mgC (1 µM) of oxidant down to 15% for an oxidant dose of 3.8 µmol/mgC (20 µM) and 6% for the highest HOBr dose tested (120 µmol equivalent to 22.6 µmol/mgC) (Fig. S.3). These results are in agreement with the study of
276 Criquet et al. (2015), which showed slightly more than 20% of incorporation for 1 µM of oxidant added 277 to a solution at 3.6 mgC L⁻¹ (0.3 µmol HOBr/mgC). The percentage decrease, together with the 278 existence of a maximal incorporation of halogen into the organic matter matrix, indicate that the sites 279 available for substitution are limited. The quantity of halogens possibly incorporated into the organic 280 matter structure could be assessed from the curve plateau (Fig. 2). The determined value of 1.4 µmol 281 halogenation sites/mgC corresponds to 50; 110 or 180 µg of chlorine, bromine or iodine respectively 282 per mg of C (with the reasonable assumption made here of equivalence between halogens). One 283 should note that this value does not take into account the halogenated small by-products possibly 284 formed from the breakdown of the molecule (discussed below).

285 These results demonstrate that the substitution and electron transfer processes are in competition 286 and that the proportion of each reaction is changing with the progress of the oxidation process. A 287 comparison between resorcinol (1,3-dihydroxybenzene), which reacts exclusively by substitution with 288 bromine, and catechol (1,2-dihydroxybenzene), which reacts by electron transfer to form 289 benzoquinone, supports the observed pattern for NOM. Indeed, both compounds, with similar pH 290 dependence (similar pKa), exhibit different apparent rate constants: k<sub>app</sub>(HOBr/catechol) = 2.7 10<sup>5</sup> M<sup>-1</sup> s<sup>-1</sup> and k<sub>app</sub> (HOBr/resorcinol) = 9.0 x10<sup>6</sup> M<sup>-1</sup> s<sup>-1</sup> at pH 7<sup>13</sup>. The higher rate constant of the substitution 291 reaction compared to electron transfer process is then the key parameter controlling the reactivity of 292 the halogenated oxidants towards organic matter. The substitution process while kinetically favorable 293 is limited by the number of sites available and decreases during the reaction of organic matter with 294 halogenated oxidant. From literature, the reactivity of HOI shows a higher dependence on the 295 structures of organic compounds compared to HOBr and the iodine reactivity is known to be lower due 296 to its polarizable character <sup>8</sup>. The similar results in terms of halogen incorporation between bromine 297 and iodine observed in our results demonstrate the low impact on the reaction pathways and their 298 proportion (Fig. 2). 299

300 An alternative methodology has been applied to assess the organic fractions of halogens. This method,
301 based on a mass balance, involves the determination of the concentration of inorganic halogens by IC-
302 ICP-MS 31 and the total concentration of halogens determined by ICP-MS without coupling. The
303 concentration of organic halogens can then be obtained by subtracting the sum of inorganic halogens
304 from the total halogen concentration. This is a usual methodology approaching the AOX method 45
305 suitable for bromine and iodine while the high concentration of chloride ion provides too much
306 uncertainties. The oxidant doses applied are below the oxidant demand of 17 µmol/mgC, therefore no
307 remaining HOBr nor HOI ahs to be considered in the mass balance.
<figure><img src="image_5.png" /></figure>

Fig. 3: Comparison of halogen incorporation on organic matter determined by SEC-ICP-MS and mass balance method (X-Org obtained by the difference between total concentrations and inorganic species): (a) bromine, (b): iodine for increasing oxidant dosage; Suwannee River NOM 5.3 mgC L⁻¹ [HOBr] from 1 to 50 µM; [HOI] from 1 to 20 µM. Error bars correspond to the variance of three independent repetitions.

Fig. 3 shows the results of the NOM fraction halogenated (determined by SEC-ICP-MS) and the total organic halogen determination (determined by mass balance method) on the same graph. Different patterns are observed depending on the methodology applied but also on the type of halogen. In the case of bromine, the mass balance method systematically gives a higher result compared to the brominated organic fraction determined by SEC-ICP-MS. The pattern is different for iodine for which the mass balance shows lower concentrations of I-Org at low oxidant dose, but this is reversed at high oxidant exposure (from 2 µM of HOI/mgC). We believe that the higher concentrations obtained by the mass balance method can be explained by the formation of small by-products such as, for example, the haloform reaction producing THMs by a C-C bond cleavage ⁴⁶,⁴⁷. The retention times of these low molecular weight by-products such as bromoform are similar to the inorganic halogenated species in SEC separation (Fig. S.4), which explains why no specific extra peak would be observed. Also, some compounds could have higher retention time due to hydrophobic interactions and/or being hidden in the background noise. The difference is increasing with the increase of oxidant dose as the production of small by-products is therefore increasing with the oxidant exposure. This would suggest that the break of organic matter into smaller by-products is delayed in the case of iodine. Iodoform is hardly found in real waters ⁴⁸, unlike bromoform, which could be in the first brominated THM present, even present in higher concentration than chloroform. A steric hindrance could be supposed which decreases the multiple iodination possibilities on the same moieties. For the highest oxidant doses, the halogenated fraction of complex organic matter represents around one third of the total halogenation for both bromine and iodine and seems to be constant (Fig. 3 and Fig. S.5). In addition, we also investigated the stability of organic bounded halogens. In fact, the poor stability of organic
335

336

halide under alkaline conditions (similar to NaOH eluant in ion chromatography) could partly explain the lower total organic iodine determination by the mass balance methodology (section 3.3).

337

### 3.3. Stability of halogenated humic substances

338

339

340

341

342

343

344

345

346

347

348

349

The stability of halogenated solutions in a basic medium and in the presence of reducing agents was studied. Organic matter aqueous samples were treated by HOBr or HOI in the same conditions as previously described. The sample stability towards NaOH or reductants such as ascorbic acid and sulfite was tested in triplicate and compared to a triplicate sample only receiving oxidant. A single oxidant dose (1 µM) has been applied to all samples. Hydroxide ions (e.g. NaOH) are commonly used as the mobile phase in ion chromatography. This analysis is widely used in literature to determine organic bromine and iodine by the difference between total (obtained from ICP-MS analysis) and inorganic species (ion-chromatography with conductivity or eventually ICP-MS detector) concentrations¹⁶,¹⁷,⁴⁵.

In the present case, IC-ICP-MS using a 10 to 20 mM NaOH gradient was used for the mass-balance method. Thus, sodium hydroxide at a concentration of 2M was added after the 24h-oxidant reaction time to reach the concentrations of 10 and 20 mM. Samples were analyzed by SEC-ICP-MS after 24 hours of contact time. The results are presented in Fig. 4.

350

351

352

353

354

355

356

357

358

359

360

Whatever the concentration, the introduction of NaOH leads to a substantial decrease in the concentration of iodine incorporated (I-Org) into the organic matter. The degradation of organic iodine ranges from 13 to 20 % when the dose of NaOH is increased from 10 to 20 mM. Furthermore, samples treated with NaOH exhibit a corresponding increase in iodide concentration. The analysis of the samples after 48h shows no further evolution. Considering bromine, the decrease of Br-Org is around 25% for both NaOH concentrations. These results demonstrate that the methodology of quantification of organic halogens by the difference of total and inorganic species is not suitable as the analytical procedure of inorganic species is detrimental to the stability of organic halogen fraction. These methods consequently underestimate the organic fraction. The time scale of organic matter degradation in contact of NaOH is certainly fast enough for the reaction to occur during the analysis. These results are in agreement with the work of Hua and Reckhow (2012)⁴⁹, which showed TOX
361

degradation in basic condition (pH around 12), however stronger for TOI compared to TOBr and TOCl.

362

We here show that the high molecular weight by-products are not stable in basic conditions.

363

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

364

<caption>Fig. 4: Influence of NaOH and reductants on recovery of halogenated organic matter complex fraction. Addition of NaOH or reducing agents: ascorbic acid or sulfite (10 times excess) to Suwannee river NOM extract previously treated by 1µM HOBr (a) or HOI (b). Error bars correspond to the variance of four independent repetitions.</caption>

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

Considering reducing agents, sulfite and ascorbic acid are usually used to quench chlorine excess during sampling of chlorinated drinking water. It is then important to also check the stability of halogenated fractions in the presence of such reactants. To investigate the effect of reducing agents on both iodine- and bromine-halogenated organic matter, three sets of halogenation experiments were conducted using HOI and HOBr as oxidizing solutions in a similar protocol as presented for NaOH. After 24 hours, ascorbic acid and sulfite were added into triplicates of oxidized samples with a 10 times excess compared to applied initial dosage of oxidant (no remaining residual as the applied dose of 1 µM is below the oxidant demand and sufficient reaction time) (Fig. 4) and were compared to the samples not receiving extra reagents. The concentrations of these reducing agents typically applied in water treatment are between 4 and 42 µM for sulfite and between 5.7 and 28.4 µM for ascorbic acid <sup>50</sup> or at least ten times the oxidant residual.

380

381

382

383

384

385

386

The obtained results indicate a degradation of the organic bound iodine when reducing agents are added. Concerning iodine, 10 and 20% decreases are observed with the addition of ascorbic acid and sulfite 10 µM, respectively. By contrast, organic-bromine signal showed a higher decrease with ascorbic acid (8%) compared to around only 4% with sulfite, close to the repeatability of the methodology) but overall lower than for iodine. Therefore, reducing agents seem to have a stronger influence on the stability of the carbon-iodine bond in organic matter compared to the carbon-bromine one. This difference could be due to the weaker C-I bond compared to C-Br due to the
increasing size from Br to I and thus the increase in Pauli repulsion (repulsive occupied orbital interactions). Indeed, the resulting C-halogen bond is then longer for the larger halogen corresponding to a decrease in homolytic bond dissociation energies (80.9 to 71.2 kcal mol⁻¹ respectively for C-Br and C-I)⁵¹. Ascorbic acid is an overall better quenching agent when considering the analysis of both brominated and iodinated by-products, this reagent is also the best option recommended for quenching of samples to be analyzed for individual organic DBPs⁵².

393

394 3.4. Application to a natural water

De Blankaart reservoir was sampled in this study as its waters are used as the main resource of drinking water for 200,000 inhabitants (30,000 m³/day). Sample had been diluted by 2 with the phosphate buffer to mimic the conditions used with NOM extract. A final DOC concentration of 4.8 mgC L⁻¹ and a dose of oxidant ranging from 1 to 20 µM corresponding to 0.2 to 4.1 µmol/mgC was applied. Halogenation of this natural water sample was performed using HOBr and HOI as oxidizing solutions, separately. After 24 hours of reaction time, the samples were analyzed by SEC-ICP-MS, and the results are presented in Fig. 5.

<figure><img src="image_8.png" /></figure>

402

<caption>Fig. 5: SEC-ICP-MS chromatograms obtained for the analysis of surface-water (DOC = 4.8 mgC L⁻¹) halogenated by: (a) HOBr, (b) HOI from 1 to 20 µM. Later improvement of iodine peak resolution has been obtained with the addition of a precolumn (Fig. 6). Retention times corresponding to (a) 1: Org-Br; 2: bromide; (b) 1: Org-I; 2: iodate; 3 iodide.</caption>

403

404 405 406

In the case of HOBr halogenation, two main peaks were observed (Fig. 5a). The first peak corresponds to the bromine incorporated onto the complex organic matter, while the second peak is attributed to mainly inorganic bromide. The first peak shows different fractions of organic matter distributed by size. The partial separation is also shown on the UV chromatogram at 254 nm (Fig. S.6) and is typical of complex natural sample organic matter fractionation analyzed by such SEC column ³¹. Within this

407

408

409

410

411
time period between 7 and 10 minutes, humic acids and building blocks (3.5 mgC L⁻¹) and low molecular weights (0.68 mgC L⁻¹) are eluted (Retention times determined by SEC-UV with the same column and conditions of elution and carbon concentrations determined by SEC-OCD, with the method characterized in Laforce et al., 2024). These fractions exhibit the same pattern of halogenation, the broad peaks increasing simultaneously with increasing oxidant dose. No halogenation of biopolymers (0.79 mgC L⁻¹) could be observed. Similarly to NOM extract, halogenation of the natural samples by HOI resulted in the generation of an extra chromatographic peak corresponding to the retention time of iodate. The resolution of the organic matter peaks is therefore poorer than Br-halogenation. The quantification of organic iodine in the natural water samples is therefore associated with a higher uncertainty, due to the possible interference with inorganic iodine species. Although deconvolution was applied to separate overlapping peaks, a partial contribution of iodide or iodate to the organic iodine signal cannot be entirely excluded. Signal deconvolution could help to integrate these peaks but another option would be in coupling several SEC columns ⁴¹. An improvement of peak resolution between organic iodine and the second peak has been further obtained by the addition of a pre-column SEC-5 (5 µm, 100 Å, 7.8 x 50 mm) allowing the complete return of the signal to baseline between those two peaks even for high concentration of inorganic iodine (Fig. 6).
<figure><img src="image_9.png" /><figcaption>Fig. 6: SEC-ICP-MS chromatogram obtained for the analysis of surface-water halogenated by 5 µM of HOI. The better resolution compared to Fig. 5 is obtained by an additional precolumn Agilent SEC-5 (5 µm, 100 Å, 7.8 x 50 mm) with no change in the condition of elution (same flow and eluant preparation).</figcaption></figure>

In Retention times corresponding to (a) 1: Org-Br; 2: bromide; (b) 1: Org-I; 2: iodate; 3 iodide. **** **Error!**

**Source du renvoi introuvable.**, bromide and iodide peaks are clearly mixed with other products as they are much larger and shoulders peaks can be observed. As previously mentioned the small halogenated DBPs are suspected to elute with a retention times similar to the ones of inorganic species (e.g. bromoform retention presented in Fig. S.4). In the present case, unknown small brominated and iodinated organic structures are certainly formed and show up from the retention time of bromide and iodide and beyond. The additional precolumn does not increase significantly the time of analysis.

From the different oxidant doses applied on the natural water, a lower incorporation of halogens is observed compared to the organic matter Suwannee River extract and the difference is increasing with the applied dose (Fig. S.7). No lag phase in halogenation due to the consumption of oxidants by inorganic substances such as reduced iron⁵⁴ is observed. Therefore, intrinsic differences of organic matters could explain the observed difference. The SUVA value of this water (2.89 L mgC⁻¹ m⁻¹) is effectively lower than the one of Suwannee river NOM (3.71 mgC⁻¹ m⁻¹) leading to less aromatic structure susceptible to substitution reactions and by-product formation⁵⁵. However, traces of
446

ammonia leading to the formation of haloamines could also be suspected to reduce the halogenation
process in this water.

447

448

449

## 4. Conclusion

450

A methodology for the analysis of halogenated organic matter has been developed to quantify the bromination and iodination of dissolved organic carbon in water samples without sample preparation.

451

452

An initial linear incorporation of bromine and iodine into organic matter is observed for increasing oxidant dose (up to around 2 µmol oxidant/mgC) followed by a reduced yield of incorporation reaching a plateau. A similar behavior is noticed for bromine and iodine. Although not demonstrated in this study, the simultaneous quantification of Cl, Br and I may be feasible, however, as the ionization potential of chlorine (12.97 eV) is higher than the one of bromine (11.81 eV) and iodine (10.45 eV), the sensitivity could be limited for drinking water treatment application, but could be useful in (industrial) waste water monitoring. A high sensitivity for all halogens could however be foreseen with solid phase extraction prior to analysis⁵⁶.

453

454

455

456

457

458

459

460

While also giving partial information on inorganic halogenated species as possibly mixed with small organic halogenated substances, this methodology provides unique information on organic matter halogenation complementary to AOX analysis. It is also complementary to HR-MS recent procedures to target halogenated organic matter as halogens are identified through their isotopic patterns and iodine is therefore not included in those studies⁵⁶,⁵⁷. This quantitative analytical method is also more sensitive, and less labor intensive than HR-MS studies as these require a pre-treatment and a concentration step before analysis and extensive data processing.

461

462

463

464

465

466

467

This method could be very useful to better quantify and characterize the unknown disinfection by-products, without the major actual major drawback of the different existing analytical procedures i.e. the partial recovery of the organic matter after the adsorption step in sample preparation. Further applications on diverse organic matters and natural water samples could be imagined in order to better understand the formation of complex halogenated by-product as well as a methodology of organic matter characterization to better understand the reactive pathways, moieties and the formation and destruction of halogenated bounds. Different type of organic matter chromatographic separation could also be applied.

468

469

470

471

472

473

474

475

## Supporting Information

476

Supplemental information made of 4 Tables and 7 figures is available free of charge via the internet at <a href='http://pubs.acs.org.xn--ivg/'>http://pubs.acs.org.</a>

477

478

479

## Declaration of Competing Interest
480
481

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

482

Acknowledgment

483
484
485
486
487
488

Authors acknowledge the French National Research Agency (ANR) - NOMIC project [ANR-21-CE04-0003-01], the University of Lille and the "Institut Universitaire de France" for fundings. The Region Hauts-de-France is acknowledged through the founding of the CPER ECRIN. ICP analyses were performed on the platform of Chevreul Institut (FR2638 CNRS - University of Lille). Karlien Dejaeger, Vincent Carlucci and Véronique Alaimo and deWatergroep are acknowledged for assistance in sampling and analysis.

489

490

491

References

492
493
494
495

(1) Plewa, M. J.; Wagner, E. D.; Richardson, S. D.; Thruston, A. D.; Woo, Y.-T.; McKague, A. B. Chemical and Biological Characterization of Newly Discovered Iodoacid Drinking Water Disinfection Byproducts. *Environmental Science & Technology* **2004**, *38* (18), 4713–4722. https://doi.org/10.1021/es049971v.

496
497
498
499

(2) Krasner, S. W.; Weinberg, H. S.; Richardson, S. D.; Pastor, S. J.; Chinn, R.; Sclimenti, M. J.; Onstad, G. D.; Thruston, A. D. Occurrence of a New Generation of Disinfection Byproducts. *Environmental Science & Technology* **2006**, *40* (23), 7175–7185. https://doi.org/10.1021/es060353j.

500
501
502
503

(3) Allard, S.; Tan, J.; Joll, C. A.; von Gunten, U. Mechanistic Study on the Formation of Cl-/Br-/I-Trihalomethanes during Chlorination/Chloramination Combined with a Theoretical Cytotoxicity Evaluation. *Environmental Science & Technology* **2015**, *49* (18), 11105–11114. https://doi.org/10.1021/acs.est.5b02624.

504
505
506

(4) Bichsel, Y.; von Gunten, U. Formation of Iodo-Trihalomethanes during Disinfection and Oxidation of Iodide-Containing Waters. *Environmental Science & Technology* **2000**, *34* (13), 2784–2791. https://doi.org/10.1021/es9914590.

507
508
509

(5) Hansson, R. C.; Henderson, M. J.; Jack, P.; Taylor, R. D. Iodoform Taste Complaints in Chloramination. *Water Research* **1987**, *21* (10), 1265–1271. https://doi.org/10.1016/0043-1354(87)90179-5.

510
511
512
513

(6) Liu, S.; Li, Z.; Dong, H.; Goodman, B. A.; Qiang, Z. Formation of Iodo-Trihalomethanes, Iodo-Acetic Acids, and Iodo-Acetamides during Chloramination of Iodide-Containing Waters: Factors Influencing Formation and Reaction Pathways. *Journal of Hazardous Materials* **2017**, *321*, 28–36. https://doi.org/10.1016/j.jhazmat.2016.08.071.

514
515
516
517

(7) Heeb, M. B.; Criquet, J.; Zimmermann-Steffens, S. G.; von Gunten, U. Oxidative Treatment of Bromide-Containing Waters: Formation of Bromine and Its Reactions with Inorganic and Organic Compounds — A Critical Review. *Water Research* **2014**, *48*, 15–42. https://doi.org/10.1016/j.watres.2013.08.030.

518
519
520

(8) MacKeown, H.; von Gunten, U.; Criquet, J. Iodide Sources in the Aquatic Environment and Its Fate during Oxidative Water Treatment – A Critical Review. *Water Research* **2022**, *217*, 118417. https://doi.org/10.1016/j.watres.2022.118417.

521
522
523

(9) Krasner, S. W. Halogenated DBPs and Emerging Issues. In *Disinfection By-Products and Human Health*; Nieuwenhuijsen, M. J., Ed.; Cambridge University Press: Cambridge, U.K., **2012**; pp 59–71.

524
525

(10) Neale, P. A.; Antony, A.; Bartkow, M. E.; Farré, M. J.; Heitz, A.; Kristiana, I.; Tang, J. Y. M.; Escher, B. I. Bioanalytical Assessment of the Formation of Disinfection Byproducts in a Drinking
526

Water Treatment Plant. *Environmental Science and Technology* **2012**, *46* (18), 10317–10325.

527

https://doi.org/10.1021/es302126t.

528

(11) Wagner, E. D.; Plewa, M. J. CHO Cell Cytotoxicity and Genotoxicity Analyses of Disinfection By-

529

Products: An Updated Review. *Journal of Environmental Sciences* **2017**, *58*, 64–76.

530

https://doi.org/10.1016/j.jes.2017.04.021.

531

(12) Dong, H.; Qiang, Z.; Richardson, S. D. Formation of Iodinated Disinfection Byproducts (I-DBPs) in

532

Drinking Water: Emerging Concerns and Current Issues. *Accounts of Chemical Research* **2019**,

533

52 (4), 896–905. https://doi.org/10.1021/acs.accounts.8b00641.

534

(13) Criquet, J.; Rodriguez, E. M.; Allard, S.; Wellauer, S.; Salhi, E.; Joll, C. A.; von Gunten, U. Reaction

535

of Bromine and Chlorine with Phenolic Compounds and Natural Organic Matter Extracts –

536

Electrophilic Aromatic Substitution and Oxidation. *Water Research* **2015**, *85*, 476–486.

537

https://doi.org/10.1016/j.watres.2015.08.051.

538

(14) Tan, J.; Allard, S.; Gruchlik, Y.; McDonald, S.; Joll, C. A.; Heitz, A. Impact of Bromide on Halogen

539

Incorporation into Organic Moieties in Chlorinated Drinking Water Treatment and Distribution

540

Systems. *Science of The Total Environment* **2016**, *541*, 1572–1580.

541

https://doi.org/10.1016/j.scitotenv.2015.10.043.

542

(15) Hong, H.; Yan, X.; Song, X.; Qin, Y.; Sun, H.; Lin, H.; Chen, J.; Liang, Y. Bromine Incorporation into

543

Five DBP Classes upon Chlorination of Water with Extremely Low SUVA Values. *Science of The

544

Total Environment **2017**, *590–591*, 720–728. https://doi.org/10.1016/j.scitotenv.2017.03.032.

545

(16) Kinani, A.; Kinani, S.; Richard, B.; Lorthioy, M.; Bouchonnet, S. Formation and Determination of

546

Organohalogen By-Products in Water – Part I. Discussing the Parameters Influencing the

547

Formation of Organohalogen by-Products and the Relevance of Estimating Their Concentration

548

Using the AOX (Adsorbable Organic Halide) Method. *TrAC Trends in Analytical Chemistry* **2016**,

549

85, 273–280. https://doi.org/10.1016/j.trac.2016.06.008.

550

(17) Chen, B.; Bu, Y.; Yang, J.; Nian, W.; Hao, S. Methods for Total Organic Halogen (TOX) Analysis in

551

Water: Past, Present, and Future. *Chemical Engineering Journal* **2020**, *399*, 125675.

552

https://doi.org/10.1016/j.cej.2020.125675.

553

(18) Kristiana, I.; McDonald, S.; Joll, C. A. The Forest or the Trees: A Critical Review on the Analysis of

554

Total Organic Halogen (TOX) in Drinking Waters and Its Utility as a Water Quality Parameter.

555

*Environmental Science: Water Research & Technology* **2020**, *6* (9), 2313–2330.

556

https://doi.org/10.1039/D0EW00300J.

557

(19) Han, J.; Zhang, X.; Jiang, J.; Li, W. How Much of the Total Organic Halogen and Developmental

558

Toxicity of Chlorinated Drinking Water Might Be Attributed to Aromatic Halogenated DBPs?

559

*Environmental Science and Technology* **2021**, *55* (9), 5906–5916.

560

https://doi.org/10.1021/acs.est.0c08565.

561

(20) Jing, W.; Wang, Y.; Guo, X.; Huang, M.; Wang, X.; Zhou, R.; Huang, Z.; Li, J. Total Organic

562

Halogen (TOX) Analysis in Waters: A Short Review. *Emerging Contaminants* **2023**, *9* (1), 19–27.

563

https://doi.org/10.1080/26395940.2023.2203350.

564

(21) Sharma, N.; Zeng, C.; Eaton, A.; Karanfil, T.; Ghosh, A.; Westerhoff, P. Co-Occurrence of Bromine

565

and Iodine Species in US Drinking Water Sources That Can Impact Disinfection Byproduct

566

Formation. *Environ. Sci. Technol.* **2023**, *57* (47), 18563–18574.

567

https://doi.org/10.1021/acs.est.2c06044.

568

(22) Morita, Y.; Kobayashi, T.; Kuroiwa, T.; Narukawa, T. Study on Simultaneous Speciation of

569

Arsenic and Antimony by HPLC–ICP-MS. *Talanta* **2007**, *73* (1), 81–86.

570

https://doi.org/10.1016/j.talanta.2007.03.005.

571

(23) Marcinkowska, M.; Barałkiewicz, D. Multielemental Speciation Analysis by Advanced

572

Hyphenated Technique – HPLC/ICP-MS: A Review. *Talanta* **2016**, *161*, 177–204.

573

https://doi.org/10.1016/j.talanta.2016.08.034.

574

(24) Hernandez, F.; Jitaru, P.; Cormant, F.; Noël, L.; Guérin, T. Development and Application of a

575

Method for Cr(III) Determination in Dairy Products by HPLC–ICP-MS. *Food Chemistry* **2018**, *240*,

576

183–188. https://doi.org/10.1016/j.foodchem.2017.07.110.
577 (25) Michalski, R.; Jabłonska, M.; Szopa, S.; Łyko, A. Application of Ion Chromatography with ICP-MS or MS Detection to the Determination of Selected Halides and Metal/Metalloids Species.

578 *Critical Reviews in Analytical Chemistry* **2011**, *41* (2), 133–150.

579 https://doi.org/10.1080/10408347.2011.559438.

581 (26) van Wyk, P.-H. Novel Methods of Chemical Speciation of Pt(IV/II) Complexes in Acid Halide-Rich Solutions by Ion-Pair RP-HPLC Coupled to ICP-OES/MS in Conjunction with 195Pt NMR. PhD Thesis, Stellenbosch University, Stellenbosch, South Africa, **2013**.

584 http://hdl.handle.net/10019.1/80099.

585 (27) Gorny, J.; Dumoulin, D.; Lesven, L.; Noiriel, C.; Madé, B.; Billon, G. Development and Application of a HPIC-ICP-MS Method for the Redox Arsenic Speciation in River Sediment Pore Waters.

587 *Journal of Analytical Atomic Spectrometry* **2015**, *30* (7), 1562–1570.

588 https://doi.org/10.1039/C5JA00095E.
589 (28) Delafiori, J.; Ring, G.; Furey, A. Clinical Applications of HPLC-ICP-MS Element Speciation: A Review. *Talanta* **2016**, *153*, 306–331. https://doi.org/10.1016/j.talanta.2016.02.035.

591 (29) Yang, H.; Liu, W.; Li, B.; Zhang, H.; Liu, X.; Chen, D. Speciation Analysis for Iodine in Groundwater Using High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS). *Geostandards and Geoanalytical Research* **2007**, *31* (4), 345–351. https://doi.org/10.1111/j.1751-908X.2007.00132.x.

595 (30) Liu, W.; Yang, H.; Li, B.; Xu, S. Determination of Bromine and Iodine Speciation in Drinking Water Using High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry. *Geostandards and Geoanalytical Research* **2011**, *35* (1), 69–74.

598 https://doi.org/10.1111/j.1751-908X.2010.00033.x.

599 (31) MacKeown, H.; Adusei Gyamfi, J.; Schoutteten, K. V. K. M.; Dumoulin, D.; Verdick, L.; Ouddane, B.; Criquet, J. Formation and Removal of Disinfection By-Products in a Full Scale Drinking Water Treatment Plant. *Science of the Total Environment* **2020**, *704*.

602 https://doi.org/10.1016/j.scitotenv.2019.135280.

603 (32) Moens, C.; Smolders, E. Suwannee River Natural Organic Matter Concentrations Affect the Size and Phosphate Uptake of Colloids Formed by Iron Oxidation. *Geochimica et Cosmochimica Acta* **2021**, *312*, 375–391. https://doi.org/10.1016/j.gca.2021.07.028.

606 (33) Hussain, A.; Trudell, P.; Repta, A. J. Quantitative Spectrophotometric Methods for Determination of Sodium Hypochlorite in Aqueous Solutions. *Journal of Pharmaceutical Sciences* **1970**, *59* (8), 1168–1170. https://doi.org/10.1002/jps.2600590824.

609 (34) Gleason, J. M.; McKay, G.; Ishida, K. P.; Mezyk, S. P. Temperature Dependence of Hydroxyl Radical Reactions with Chloramine Species in Aqueous Solution. *Chemosphere* **2017**, *187*, 123–129. https://doi.org/10.1016/j.chemosphere.2017.08.053.

612 (35) Chehab, R. Développement de Systèmes Automatisés Pour l’Analyse Des Chloramines Inorganiques et Des Trihalométhanes Dans Les Eaux. PhD Thesis, Aix-Marseille Université, Marseille, France, 2019. https://theses.fr/2019AIXM0497.

615 (36) Rodier, J.; Legube, B.; Merlet, N. *L'analyse de l'eau - 10e éd.*; Dunod, **2016**.

616 (37) Huber, S. A.; Balz, A.; Abert, M.; Pronk, W. Characterisation of Aquatic Humic and Non-Humic Matter with Size-Exclusion Chromatography – Organic Carbon Detection – Organic Nitrogen Detection (LC-OCD-OND). *Water Research* **2011**, *45* (2), 879–885.

619 https://doi.org/10.1016/j.watres.2010.09.023.

620 (38) International Organization for Standardization (ISO). *ISO/TS 13530:2009(fr)*, *Qualité de l'eau — Lignes directrices pour le contrôle de qualité analytique pour l'analyse chimique et physicochimique de l'eau*. https://www.iso.org/obp/ui/fr/#iso:std:iso:ts:13530:ed-1:v1:fr (accessed 2024-12-02).

624 (39) Johnson-Davis, K. L.; Farnsworth, C.; Law, C.; Parker, R. Method Validation for a Multi-Element Panel in Serum by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). *Clinical Biochemistry* **2020**, *82*, 90–98. https://doi.org/10.1016/j.clinbiochem.2020.05.002.

627 (40) Upadhyay, K.; Viramgami, A.; Balachandar, R.; Sheth, A.; Sivaperumal, P. Development and Validation of an ICP-MS Method and Its Application in Assessing Heavy Metals in Whole Blood
629 Samples among Occupationally Exposed Lead Smelting Plant Workers. *Journal of Biological Inorganic Chemistry* **2024**, 29 (7-8), 763-771. https://doi.org/10.1007/s00775-024-02077-7.

630 (41) Valenti-Quiroga, M.; Daunis-i-Estadella, P.; Emiliano, P.; Valero, F.; Martin, M. J. NOM Fractionation by HPSEC-DAD-OCD for Predicting Trihalomethane Disinfection by-Product Formation Potential in Full-Scale Drinking Water Treatment Plants. *Water Research* **2022**, 227, 119314. https://doi.org/10.1016/j.watres.2022.119314.

631 (42) Jiang, X.; van der Horst, A.; van Steenbergen, M. J.; Akeroyd, N.; van Nostrum, C. F.; Schoenmakers, P. J.; Hennink, W. E. Molar-Mass Characterization of Cationic Polymers for Gene Delivery by Aqueous Size-Exclusion Chromatography. *Pharm Res* **2006**, 23 (3), 595-603. https://doi.org/10.1007/s11095-006-9574-4.

632 (43) *Persistent Lines of Neutral Iodine* (11). https://physics.nist.gov/PhysRefData/Handbook/Tables/iodinetable3.htm (accessed 2025-08-31).

633 (44) *Atomic Data for Bromine* (Br). https://physics.nist.gov/PhysRefData/Handbook/Tables/brominetable1.htm (accessed 2025-08-31).

634 (45) Xu, R.; Xie, Y.; Tian, J.; Chen, L. Adsorbable Organic Halogens in Contaminated Water Environment: A Review of Sources and Removal Technologies. *Journal of Cleaner Production* **2021**, 283, 124645. https://doi.org/10.1016/j.jclepro.2020.124645.

635 (46) Dickenson, E. R. V.; Summers, R. S.; Croué, J.-P.; Gallard, H. Haloacetic Acid and Trihalomethane Formation from the Chlorination and Bromination of Aliphatic β-Dicarbonyl Acid Model Compounds. *Environmental Science & Technology* **2008**, 42 (9), 3226-3233. https://doi.org/10.1021/es0711866.

636 (47) Rowett, A. C.; Heard, D. M.; Koria, P.; Dean, A. C.; Sweeting, S. G.; Lennox, A. J. J. 200 Years of The Haloform Reaction: Methods and Applications. *Chemistry* **2024**, 30 (71), e202403045. https://doi.org/10.1002/chem.202403045.

637 (48) DeMarini, D. M.; Warren, S. H.; Smith, W. J.; Richardson, S. D.; Liberatore, H. K. Inability of GSTT1 to Activate Iodinated Halomethanes to Mutagens in Salmonella. *Environmental and Molecular Mutagenesis* **2021**, 62 (3), 168-176. https://doi.org/10.1002/em.22423.

638 (49) Hua, G.; Reckhow, D. A. Effect of Alkaline pH on the Stability of Halogenated DBPs. *Journal AWWA* **2012**, 104 (2). https://doi.org/10.5942/jawwa.2012.104.0025.

639 (50) Moore, N.; Ebrahimi, S.; Zhu, Y.; Wang, C.; Hofmann, R.; Andrews, S. A Comparison of Sodium Sulfite, Ammonium Chloride, and Ascorbic Acid for Quenching Chlorine Prior to Disinfection Byproduct Analysis. *Water Supply* **2021**, 21 (5), 2313-2323. https://doi.org/10.2166/ws.2021.059.

640 (51) Blokker, E.; Sun, X.; Poater, J.; van der Schuur, J. M.; Hamlin, T. A.; Bickelhaupt, F. M. The Chemical Bond: When Atom Size Instead of Electronegativity Difference Determines Trend in Bond Strength. *Chemistry - A European Journal* **2021**, 27 (63), 15616-15622. https://doi.org/10.1002/chem.202103544.

641 (52) Kristiana, I.; Lethorn, A.; Joll, C.; Heitz, A. To Add or Not to Add: The Use of Quenching Agents for the Analysis of Disinfection by-Products in Water Samples. *Water Research* **2014**, 59, 90-98. https://doi.org/10.1016/j.watres.2014.04.006.

642 (53) Laforce, E.; Dejaeger, K.; Vanoppen, M.; Cornelissen, E.; De Clercq, J.; Vermeir, P. Thorough Validation of Optimized Size Exclusion Chromatography-Total Organic Carbon Analysis for Natural Organic Matter in Fresh Waters. *Molecules* **2024**, 29 (9), 2075. https://doi.org/10.3390/molecules29092075.

643 (54) Deborde, M.; von Gunten, U. Reactions of Chlorine with Inorganic and Organic Compounds during Water Treatment—Kinetics and Mechanisms: A Critical Review. *Water Research* **2008**, 42 (1), 13-51. https://doi.org/10.1016/j.watres.2007.07.025.

644 (55) Lee, S.; Park, J. Comparison of Molecular Characteristics between Commercialized and Regional Natural Organic Matters. *Environmental Engineering Research* **2024**, 29 (2). https://doi.org/10.4491/eer.2023.190.
681

(56) Gao, Y.; Wang, W.; He, C.; Fang, Z.; Zhang, Y.; Shi, Q. Fractionation and Molecular

682

Characterization of Natural Organic Matter (NOM) by Solid-Phase Extraction Followed by FT-ICR

683

MS and Ion Mobility MS. *Anal Bioanal Chem* **2019**, *411* (24), 6343–6352.

684

https://doi.org/10.1007/s00216-019-01943-7.

685

(57) He, C.; Zhang, Y.; Li, Y.; Zhuo, X.; Li, Y.; Zhang, C.; Shi, Q. In-House Standard Method for

686

Molecular Characterization of Dissolved Organic Matter by FT-ICR Mass Spectrometry. ACS

687

*Omega* **2020**, *5* (20), 11730–11736. https://doi.org/10.1021/acsomega.0c01055.

688