Analysis of inorganic chloramines in water

Simultaneous separation and detection of monochloramine, nitrite, and nitrate by step-gradient mixed-mode ion chromatography: Translation from benchtop to portable ion chromatograph

BACKGROUND

Nitrite (NO2-) and nitrate (NO3-) can be produced in the distribution systems of chloraminated drinking water due to the nitrification of ammonia. The most applied inorganic chloramine for this purpose, namely monochloramine (NH2Cl), is also released into aquatic environments from water treatment plants' effluent and within industrial waste streams. Within the treatment process, the continuous monitoring of disinfectant levels is necessary to limit the harmful disinfectant by-product (DBP) formation. Currently, NH2Cl can interfere with nutrient analysis in water samples, and there are no analytical techniques available for the simultaneous analysis of NH2Cl, NO2-, and NO3-.

RESULTS

A green analytical method based on mixed-mode ion chromatography, specifically ion exchange and ion exclusion modes, was developed for the simultaneous separation and detection of NH2Cl, NO2-, and NO3-. The separation was achieved using a Dionex IonPac AG15 column guard column and a step gradient elution involving deionized water and 120.0 mM NaCl. The method was developed using a benchtop HPLC with a custom-made multi-wavelength UV absorbance detector with a 50-mm flow cell to enable the sensitive detection of NH2Cl, NO2-, and NO3- at 240 nm, 220 nm, and 215 nm, respectively. The developed method was then transferred to a portable ion chromatography (IC) system, the Aquamonitrix analyser. The total run time was less than 10 min for both systems. The benchtop HPLC method had a limit of detection (LOD) of 0.07 μg mL-1 as Cl2 for NH2Cl, 0.01 μg mL-1 for NO2-, and 0.03 μg mL-1 for NO3-. The LODs obtained using the portable Aquamonitrix analyser were found to be 0.36 μg mL-1 as Cl2, 0.02 μg mL-1, and 0.11 μg mL-1 for NH2Cl, NO2-, and NO3-, respectively. Excellent linearity (r ≥ 0.9999) was achieved using the portable analyser over the studied concentration ranges. The developed system was applied to the analysis of spiked municipal drinking water samples and showed excellent repeatability for the three analytes at three different concentration levels (RSD of triplicate recovery experiments ≤ 1.9 %). Moreover, the variation in retention time was negligible for the three target analytes with RSD ≤ 0.8 % over 12 runs.

SIGNIFICANCE

We are reporting the first ion chromatographic method for the simultaneous separation and detection of NH2Cl, NO2-, and NO3- in water samples. The monitoring of NH2Cl, NO2-, and NO3- is critical for the determination of disinfectant dosing, water quality, and nitrification status. The developed method can be applied using a benchtop HPLC or via the portable automated IC system to monitor for the three target compounds analysis in water treatment plants.

Formation of nitrogen-containing disinfection by-products during the chloramination treatment of an emerging pollutant

Chloramination was commonly used as disinfectant for killing pathogens in water. However, in this process, nitrogen-containing disinfection by-products (N-DBPs) would accidently form and subsequently rise toxicity. Here, we investigated acute toxicity variation and by-products formation during chloramination treatment on UV filter 2-hydroxy-4-methoxy-5-sulfonic acid benzophenone (BP-4). Under alkaline conditions, the acute toxicity of this system had significant increase. A total of 17 transformation products were tentatively identified, and for them, plausible transformation pathways were proposed. Noticeably, numerous aniline and nitrosobenzene analogs were detected, and the dramatic increase of acute toxicity in this system might be primarily attributed to the formation of benzoquinone and aniline analogs. Besides, bromophenol, iodophenol and iodobenzoquinone analogs exhibiting high toxicity were generated in the presence of bromine and iodide ions. This study indicates that chloramination treatment may significantly increase potential health risk, further management on disinfection system is reasonable.

Chloramines as an important photochemical source of chlorine atoms in the urban atmosphere

Monochloramine, dichloramine and trichloramine (NH2Cl, NHCl2, NCl3) are measured in the ambient atmosphere, in downtown Toronto in summer (median 39, 15 and 2.8 ppt) and winter (median 11, 7.3 and 0.7 ppt). NCl3 and NHCl2 were also measured in summer (median 1.3 and 14 ppt) from a suburban Toronto location. Measurements at two locations demonstrate prevalence of chloramines in an urban atmosphere. At both sites, NCl3 exhibits a strong diel pattern with maximum values during the night, and photolytic loss with sunrise. At the downtown site, a strong positive correlation between NH2Cl and NHCl2 in the summer night indicates a common source, with daily average peak mixing ratios approaching 500 and 250 ppt, respectively. As a previously unidentified source of chlorine (Cl) atoms, we demonstrate that NCl3 photolysis contributes 49 to 82% of the total local summertime Cl production rate at different times during the day with an average noontime peak of 3.8 × 105 atoms/cm3/s, with smaller contributions from ClNO2 and Cl2. Photolysis of NH2Cl and NHCl2 may augment this Cl production rate. Our measurements also demonstrate a daytime enhancement of chloroacetone in both the summer and winter, demonstrating the importance of Cl photochemistry. The results suggest that chloramines are an important source of Cl atoms in urban areas, with potential impacts on the abundance of organic compounds, ozone, nitrogen oxides, and particulate matter. Future studies should explore the vertical gradients of chloramines and their contribution to Cl production throughout the boundary layer.

A Critical Review on Chemical Speciation of Chlorine-Produced Oxidants (CPOs) in Seawater. Part 2: Sampling, Sample Preparation and Non-Chromatographic and Mass Spectrometric-Based Methods

Chlorination of seawater forms a range of secondary oxidative species, collectively termed "chlorine-produced oxidants" (CPOs). These compounds do not have the same biocidal efficacy, the same fate and behavior in the marine environment, the same potential formation of chlorination by-products (CBPs), nor the same effects on marine organisms. Their chemical speciation is an important step toward an accurate assessment of the effectiveness of chlorination and the potential impacts of its releases, among others. The aim of this paper - which is the second of a trilogy dedicated to the chemical speciation of CPOs in seawater - is to cover all aspects related to CPOs analysis in seawater, from sampling to instrumental determination. First, it discusses the procedures involved in synthesis, storage, and standardization of analytical standards. Second, it deals with sampling and sample preparation, addressing all relevant issues related to these two key steps. Third, it provides a comprehensive and up-to-date overview of the colorimetric, titrimetric, and electrochemical methods used for CPOs determination and thoroughly discusses their advantages and limitations. Finally, this review ends with some recommendations for progress in the field of CPO analysis with the three aforementioned approaches. Chromatographic and mass spectrometric-based methods will be covered in the third and final article (Part III).

Insight into the formation of iodinated trihalomethanes during chlorination, monochloramination, and dichloramination of iodide-containing water

In this study, the formation of iodinated trihalomethanes (I-THMs) was systematically evaluated and compared for three treatment processes - (i) chlorination, (ii) monochloramine, and (iii) dichloramination - under different pH conditions. The results demonstrated that I-THM formation decreased in the order of monochloramination > dichloramination > chlorination in acidic and neutral pH. However, the generation of I-THMs increased in the dichloramination < chlorination < monochloramination order in alkaline condition. Specifically, the formation of I-THMs increased as pH increased from 5 to 9 during chlorination and monochloramination processes, while the maximum I-THM formation occurred at pH 7 during dichloramination. The discrepancy could be mainly related to the stability of the three chlor (am) ine disinfectants at different pH conditions. Moreover, in order to gain a thorough insight into the mechanisms of I-THM formation during dichloramination, further investigation was conducted on the influencing factors of DOC concentration and Br^-/I^- molar ratio. I-THM formation exhibited an increasing and then decreasing trend as the concentration of DOC increased from 1 to 7 mg-C/L, while the yield of I-THMs increased with increasing Br^-/I^- molar ratio from 5:0 to 5:10. During the three processes mentioned above, similar I-THM formation results were also obtained in real water, which indicates that the excessive generation of I-THMs should be paid special attention during the disinfection of iodide-containing water.

Elimination of Oxygen Interference in the Electrochemical Detection of Monochloramine, Using In Situ pH Control at Interdigitated Electrodes

Disinfection of water systems by chloramination is a method frequently used in North America as an alternative to chlorination. In such a case, monochloramine is used as the primary chlorine source for disinfection. Regular monitoring of the residual concentrations of this species is essential to ensure adequate disinfection. An amperometric sensor for monochloramine would provide fast, reagent-free analysis; however, the presence of dissolved oxygen in water complicates sensor development. In this work, we used in-situ pH control as a method to eliminate oxygen interference by conversion of monochloramine to dichloramine. Unlike monochloramine, the electrochemical reduction of dichloramine occurs outside the oxygen reduction potential window and is therefore not affected by the oxygen concentration. Potential sweep methods were used to investigate the conversion of monochloramine to dichloramine at pH 3. The pH control method was used to calibrate monochloramine concentrations between 1 and 10 ppm, with a detection limit of 0.03 ppm. Tests were carried out in high alkalinity samples, wherein it was found that the sensitivity of this method effectively remained unchanged. Monochloramine was also quantified in the presence of common interferents (copper, phosphate, and iron) which also had no significant impact on the analysis.

A multivariate Bayesian network analysis of water quality factors influencing trihalomethanes formation in drinking water distribution systems

Controlling disinfection by-products formation while ensuring effective drinking water disinfection is important for protecting public health. However, understanding and predicting disinfection by-product formation under a variety of conditions in drinking water distribution systems remains challenging as disinfection by-product formation is a multifactorial phenomenon. This study aimed to assess the application of Bayesian Network models to predict the concentration of trihalomethanes, the dominant halogenated disinfection by-product class, using various water quality parameters. Naïve Bayesian and semi-naïve Bayesian models were constructed from Sydney and South East Queensland datasets across 15 drinking water distribution systems in Australia. The targeted variable, total trihalomethanes concentration, was discretised into 3 bins (<0.1 mg L^-1, 0.1 - 0.2 mg L^-1 and >0.2 mg L^-1). The Bayesian network structures were built using water quality parameters including concentrations of individual and total trihalomethanes, disinfectant species (free chlorine, monochloramine, dichloramine, total chlorine), nitrogen species (free ammonia, total ammonia, nitrate, nitrite), and other physical/chemical parameters (temperature, pH, dissolved organic carbon, total dissolved solids, conductivity and turbidity). Seven performance parameters, including predictive accuracy and the rates of true and false positive and negative results, were used to assess the accuracy and precision of the Bayesian network models. After evaluating the model performance, the optimum models were selected to be Bayesian network augmented naïve models. These were observed to have the highest predictive accuracies for Sydney (78%) and South East Queensland (94%). Although disinfectant residuals are among the key variables that lead to trihalomethanes formation, potential concentrations of trihalomethanes in distribution systems can be more confidently predicted, in terms of probability associated with a wider range of water quality variables, using Bayesian networks. The modelling procedure developed in this work can now be applied to develop system-specific Bayesian network models for trihalomethanes prediction in other drinking water distribution systems.

Highly Antibacterial Efficacy of a Cotton Fabric Treated with Piperazinyl Schiff Base

Due to the structure of hierarchical aligned cellulose fibrils, cotton fabric used in clothing possesses excellent moisture and thermal managements. Such structure yet may retain metabolic excrements and sebum secretions discharged from the human skin, which reproduce microorganisms harmful for human health. However, incorporating the antimicrobial coating into the cotton fabric can sufficiently resist the microorganism growth. In this work, a water-soluble antibacterial coating named N-(4-(allyloxy) benzylidene)-2-(piperazin-1-yl) ethanamine (NABPE) was synthesized to produce a rechargeable and fast sterilization cotton fiber fabric (M-cotton/NABPE). M-cotton/NABPE exhibited a high effective antibacterial activity, and the inhibition ratios against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 94 % and 93 %, respectively. Chlorination was performed with sodium hypochlorite solution to form N-Cl bond on the M-cotton/NABPE fabrics, resulting in a high biocidal efficacy of up to 100 % via contact killing for a duration of 5 min. After 25 washing cycles, the antibacterial fabric still maintained an antibacterial rate of 91.95 % and 92.15 % against E. coli and S. aureus, respectively. Furthermore, the fabrics showed integrated properties of excellent UV stability, long-term stability, robust rechargeable biocidal activity (chlorine recharging >5000 ppm) and washing durability. This research provides fundamental insights into the synthesis of the NABPE and prolonged biocidal efficacy of the M-cotton/NABPE, and thereby pave a pathway to incorporate an economic and environmental-friendly antibacterial coating suitable for finishing cotton fabric.

Challenges and opportunities for on-line monitoring of chlorine-produced oxidants in seawater using portable membrane-introduction Fourier transform-ion cyclotron resonance mass spectrometry

The present study reports the first evaluation of a MIMS device equipped with a high-resolution Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS) for comprehensive speciation of chlorine-produced oxidants (CPO) in seawater. A total of 40 model compounds were studied: 4 inorganic haloamines (mono-, di-, and trichloramine and monobromamine), 22 organic N-haloamines, 12 N-haloamino acids, and 2 free oxidants (HOCl/ClO^- and HOBr/BrO^-). The main key factors influencing the analytes' introduction and their detection were optimized. Under optimized conditions, the rise and fall times of the MIMS signal ranged from 8 to 79 min and from 7 to 73 min, respectively, depending on the compound. Free oxidants and N-haloamino acids, which are ionic or too polar at seawater pH, hardly crossed the membrane, and MIMS analysis was thus unsuitable. Nevertheless, better enrichment and therefore better sensitivity were achieved with organic N-haloamines than with inorganic haloamines. The observed detection limits ranged from tens of μM to sub-μM levels. Oxidant decomposition occurred inside the MIMS device, at a higher rate for N-bromamines than for chlorinated analogues.Graphical abstract.

Inorganic chloramines: a critical review of the toxicological and epidemiological evidence as a basis for occupational exposure limit setting

Inorganic chloramines are not commercially available, but monochloramine is produced in situ for disinfection or for use in chemical synthesis. Inorganic chloramines are also formed when free chlorine reacts with nitrogen containing substances, e.g. ammonia and urea, present in chlorinated water sources. Occupational exposure may, therefore, occur in e.g. swimming pool facilities and the food processing industry. Monochloramine is soluble and stable in water and the dominating inorganic chloramine in chlorinated water sources. No clinical effects were seen in healthy volunteers given monochloramine in drinking water during 4 or 12 weeks in doses of 0.043 or 0.034 mg/kg bw/day, respectively. Limited data indicate that monochloramine is weakly mutagenic in vitro but not genotoxic in vivo. One drinking water study indicated equivocal evidence of carcinogenicity in female rats but not in male rats and mice. No reproductive or developmental effects were shown in rodents in the few studies located. Dichloramine is soluble but unstable in water. In the only study located, mild histological effects in kidneys, thyroid and gastric cardia were observed in rats administered dichloramine in drinking water for 13 weeks. Trichloramine is immiscible with water and evaporates easily from water into air. Therefore, the primary exposure route of concern in the occupational setting is inhalation. Occupational exposure to trichloramine has been demonstrated in indoor swimming pool facilities and in the food processing industry where chlorinated water is used for disinfection. Exposure-response relationships between airborne levels and self-reported ocular and upper airway irritation have been shown in several studies. Exposure to trichloramine may aggravate asthma symptoms in individuals with existing asthma. The risk of developing asthma following long-term exposure to trichloramine cannot be evaluated at present. No data on genotoxic, carcinogenic, reproductive or developmental effects were located. The toxicological data for mono- and dichloramine are insufficient to recommend health-based occupational exposure limits (OELs).As regard trichloramine, the critical effect is judged to be irritation observed in several studies on pool workers, starting at approximately 0.4 mg/m³ (stationary sampling). Based on these data, a health-based OEL of 0.1 mg/m³ (8-h time-weighted average) is recommended. This corresponds to 0.2 mg/m³ for stationary measurements in swimming pool facilities. No short-term exposure limit (STEL) is recommended.

Is It Possible to Measure Monobromamine Using Colorimetric Methods Based on the Berthelot Reaction, Like for Monochloramine?

Analytical methods based on the Berthelot reaction were recently adapted for determining monochloramine (MCA: NH2Cl) in freshwater. The specificity of the Berthelot reaction with regard to MCA is related to the need for two exchangeable hydrogen atoms to form indophenol blue. MCA can thus be distinguished from organic N-chloramines, which have only one exchangeable hydrogen atom. Monobromamine (MBA: NH2Br) may be formed during chlorination of seawater containing ammonium ions. Quantifying MBA is quite challenging and no method has been reported for its specific determination in seawater. As MBA also has two exchangeable hydrogen atoms, its reactivity might be analogous to that of MCA, but this hypothesis has never been investigated. The aim of this study was to examine the applicability of the so-called “indophenol method” for the determination of the MBA in freshwater and seawater samples. The reaction between MBA and Berthelot reagents was studied in both ultrapure water and artificial seawater. The reaction products were characterized by using gas chromatography coupled to mass spectrometry (GC–MS), Fourier transform-ion cyclotron resonance mass spectrometry (FT–ICR MS), and UV–vis spectroscopy. Results showed that colorimetric methods based on the Berthelot reaction were not suitable for measuring MBA in freshwater or seawater, since NH2Br reacts with alkaline phenol derivative via electrophilic substitution to form ortho- and para-brominated phenols instead of forming indophenol.

Application of stabilized hypobromite for controlling membrane fouling and N-nitrosodimethylamine formation

Chloramination is a conventional and successful pre-disinfection approach to control biological fouling for reverse osmosis (RO) treatment in water reuse. This study aimed to evaluate the possibility of using a new disinfectant-stabilized hypobromite-in controlling membrane fouling and the formation of a particular carcinogenic disinfection byproduct (DBP)-N-nitrosodimethylamine (NDMA). Our accelerated chemical exposure tests showed that the new disinfectant reduced the permeability of a polyamide RO membrane permeability from 6.7 to 4.1 L/m²hbar; however, its treatment impact was equivalent to that of chloramine. The disinfection efficacy of stabilized hypobromite was greater than that of chloramine when evaluated with intact bacterial counts, which suggests its potential for mitigating membrane biofouling. Additional pilot-scale tests using synthetic wastewater demonstrated that pre-disinfection with the use of stabilized hypobromite inhibits membrane fouling. Among 13 halogenated DBPs evaluated, the formation of bromoform by stabilized hypobromite was higher than that by chloramine at a high dose of 10 mg/L, thus suggesting the need for optimizing chemical doses for achieving sufficient biofouling mitigation. NDMA formation upon stabilized hypobromite treatment in two different types of actual treated wastewaters was found to be negligible and considerably lower than that by chloramine treatment. In addition, NDMA formation potential by stabilized hypobromite was 2-5 orders of magnitude lower than that by chloramine. Our findings suggest the potential of using stabilized hypobromite for controlling NDMA formation and biofouling, which are the keys to successful potable water reuse.

Development of an automated system for the analysis of inorganic chloramines in swimming pools via multi-syringe chromatography and photometric detection with ABTS

Inorganic chloramines are disinfection by-products resulting from the unwanted reaction between chlorine used as disinfectant in swimming pools and nitrogenous compounds brought by bathers. This parameter (total chloramines or combined chlorine) is currently measured on site by a colorimetric method that does not allow to measure only inorganic chloramines. In this paper, a multi-syringe chromatography system combined with a post column derivatization is applied for the first time for the specific detection of the three individual inorganic chloramines (monochloramine, dichloramine and trichloramine). These latter ones are separated using a low-pressure monolithic C18 column, and separately detected after a post-column reaction with the chromogenic reagent ABTS (2,2'-azino-bis-(3-ethyl-benzothiazoline)-6-sulfonic acid-diammonium salt). Development of two ABTS reagents provides discrimination of chlorine and monochloramine that are not separated on the column. Optimization of the experimental conditions enables determination of inorganic chloramines with very good detection limits (around 10 μg eq.Cl₂ L^-1) without interferences from other chlorinated compounds such as organic chloramines or free available chlorine. The validation of the whole procedure has been successfully applied to real swimming pools samples.

Tracking Monochloramine Decomposition in MIMS Analysis

Membrane-introduction mass spectrometry (MIMS) has been presented as one of the promising approaches for online and real-time analysis of monochloramine (NH₂Cl) in diverse matrices such as air, human breath, and aqueous matrices. Selective pervaporation of NH₂Cl through the introduction membrane overcomes the need for sample preparation steps. However, both the selectivity and sensitivity of MIMS can be affected by isobaric interferences, as reported by several researchers. High-resolution mass spectrometry helps to overcome those interferences. Recent miniaturization of Fourier transform—ion cyclotron resonance—mass spectrometry (FT-ICR MS) technology coupled to the membrane-introduction system provides a potent tool for in field analysis of monochloramine in environmental matrices. Monochloramine analysis by MIMS based FT-ICR MS system demonstrated decomposition into ammonia. To further clarify the origin of this decomposition, headspace analyses after bypassing the membrane were undertaken and showed that monochloramine decomposition was not exclusively related to interactions within the membrane. Adsorption inside the MIMS device, followed by surface-catalyzed decomposition, was suggested as a plausible additional mechanism of monochloramine decomposition to ammonia.

Determination of monochloramine dissipation kinetics in various surface water qualities under relevant environmental conditions - Consequences regarding environmental risk assessment

A total 190 experiments were performed to study the dissipation kinetics of monochloramine (NH₂Cl, CAS no 10599-90-3) in surface water samples from six rivers (Loire, Rhône, Meuse, Garonne, Seine and Moselle) and an artificial reservoir (Mirgenbach), all located in France. Experiments were conducted in an open reactor, under relevant controlled environmental conditions. The impact of various parameters such as initial NH₂Cl concentration, temperature, pH, presence of sediments, sampling site and collection period was investigated. It was found that NH₂Cl dissipated rapidly without any lag phase, and that decay follows an apparent first-order kinetics (r² > 0.99). Presence of sediment greatly accelerated decay. Half-lives were generally <1 h in river water in presence of natural sediment, but of several hours without sediment. The impact of pH was low for the normal river water pH range. However, increase in temperature significantly accelerated decay. The combination of high initial NH₂Cl concentrations and elevated temperatures generally gives half-lives similar to those obtained at lower temperatures and lower concentrations. Short half-lives (0.06 to 1.50 h) were found in all the surface waters examined, regardless of geographic location of sampling site or collection period, indicating no temporal or site-specific effects on NH₂Cl dissipation. Decay was slightly faster at lower initial concentrations, which supports extrapolation of half-lives measured in this study to a wide range of environmental concentrations. It can thus be assumed that NH₂Cl degradation in river and reservoir waters is mainly determined by presence of sediments and temperature.

Electrogeneration of inorganic chloramines on boron-doped diamond anodes during electrochemical oxidation of ammonium chloride, urea and synthetic urine matrix

Ubiquitous presence of chloride in water effluents may result in the unavoidable electrogeneration of active chlorine species when considering the application of electrochemical advanced oxidation processes as water treatment technologies. However, less attention has been drawn to the subsequent generation of other combined chlorine species such as chloramines. In this work, the electrogeneration of chloramines has been assessed in different water matrices containing NHCl₄, urea or synthetic urine. The yield of chloramines has been followed in-situ by differential electrochemistry mass spectroscopy (DEMS) during electrochemical advanced oxidation process with boron-doped diamond (BDD) anodes. Furthermore, the influence of several variables such as chloride concentration, pH or organics concentration on the different distribution of inorganic monochloramine, dichloramine and trichloramine released as products has been considered.

Disinfectant residual stability leading to disinfectant decay and by-product formation in drinking water distribution systems: A systematic review

Secondary disinfectants, such as chlorine and chloramine, have been widely applied to minimise microbial risks in drinking water during distribution. Key challenges have included the maintenance of stable concentrations of disinfectant residuals and the control of disinfection by-products that may form as a consequence of residual decay processes. Many factors may influence disinfectant residual stability and the consequential formation of by-products. Thus predictions of disinfectant stability and by-product formation are multifactorial problems, complete with numerous complications of parameter co-dependence and feedback amplification of some key parameters. The aim of this review was to derive an understanding of how disinfectant residual stability in drinking water distribution systems is impacted by various influencing factors such as water quality and operational parameters. Factors known to influence disinfectant stability and by-product formation were critically reviewed. A systematic review method was applied to identify 1809 journal articles published in the two decades from January 1998 to December 2017. From the initial screening, 161 papers were selected for detailed assessment. Important factors were identified to include temperature, water age, piping material, corrosion products, pH, hydraulic condition, disinfectant residual type and dosage and microbial activity. Microbial activity is a particularly complex parameter on which to base predictions since many factors are known to influence the degree and nature of such activity. These include temperature, water age, piping material, corrosion products, nutrients, natural organic matter, hydraulic condition and disinfectant residual type and dosage. Disinfectant types and dosages were found to be among the most important factors. Many knowledge gaps and research needs still remain, including the need for a more complete understanding of the factors that influence the production of nitrogenous disinfection by-products.

The Henry's constant of monochloramine

Monochloramine is a secondary disinfectant used in drinking water and is also formed in chlorinated wastewater. While known to hydrolyze over time and react with dissolved organic matter, its partitioning between the aqueous and gas phase has not been extensively studied. Preliminary experiments demonstrated that monochloramine concentrations in solutions open to the atmosphere or actively aerated decreased more rapidly than in sealed solutions, indicating significant losses to the atmosphere. For example, a monochloramine solution open to the atmosphere yielded a loss rate constant of 0.08 d^-1, a value twice that for sealed samples without headspace (0.04 d^-1) where loss occurs exclusively as a result of hydrolysis. A solution aerated at 10 mL s^-1 had a loss rate constant nearly 10× greater than that for hydrolysis alone (0.35 d^-1). To better understand partitioning of monochloramine to the gas phase and potential for volatilization, the dimensionless Henry's law constants of monochloramine (K_H) were determined using an equilibrium headspace technique at five different temperatures (11, 16, 21, 27, and 32 °C). The resulting values ranged from 8 × 10^-3 to 4 × 10^-2, indicating a semi-volatile compound, and were found to be consistent with quantitative structure activity relationship predictions. At 20 °C, monochloramine exhibits a dimensionless Henry's constant of about 1.7 × 10^-2 which is 35 times greater than ammonia but comparable to the Henry's constant of inorganic semi-volatile compounds such sulfur dioxide. The Henry's constant values for monochloramine suggests that volatilization could be a relevant loss process in open systems such as rivers receiving chlorinated wastewater effluent, swimming pools and cooling towers.

Study of the degradation process of ofloxacin with free chlorine by using ESI-LCMSMS: Kinetic study, by-products formation pathways and fragmentation mechanisms

This study was conducted to gain a better understanding of the fate of fluoroquinolone antibacterial ofloxacin (OFX) which is the free available chlorine (FAC) in order to determine its effect during water chlorination process. The Direct reactions of FAC with OFX were quite rapid. A half-life of 7.7 s was measured under pseudo-first order conditions in the presence of an excess of total chlorine ([FAC]₀ = 13 μM and [OFX]₀ = 0.55 μM at pH 7.2 and 20 °C in buffered reagent water. Free chlorine reactions rates were of first-order type in both substrate and oxidant with specific second-order rate constants of 6.8 × 10³ M^-1 s^-1. No induced back reactions or other interference by using thiosulfate to stop the chlorination reaction was shown. The seven products of the reaction were determined by using the LC/MS/MS analysis. Structures were investigated due to the explication of transitions obtained at different CID energies by LC-ESI-MS/MS. Pathways of the formations of these by-products were presented in this study and pathways of the fragmentations of pseudo molecular ions of the structures proposed were presented in supplementary files.

Chloramines in a pilot-scale water distribution system: Transformation of 17β-estradiol and formation of disinfection byproducts

The degradation and transformation products of 17β-estradiol (E2) by chloramines in a pilot-scale water distribution system (WDS) were investigated using varying conditions including multiple mass ratios of chlorine to nitrogen (Cl/N), changing concentrations of chloramines, and different pH and pipe materials. The degradation of E2 was complete in ≤9 h in both deionized water (DW) and in the WDS under studied conditions. When the degradation rate of E2 was compared in WDS and DW, the degradation rate was appreciably greater in the WDS than in the DW at Cl/N mass ratios of 3, 4 and 6. However, at Cl/N mass ratios of 8 and 9, degradation was faster in the DW than in the WDS. The degradation rate of E2 was greatly affected by the initial total chloramine concentration, and the degradation of E2 in DW was consistent with second-order kinetics. The degradation rate of E2 in both the DW and the WDS increased with increasing pH. The order of degradation rate of E2in different pipes was: ductile iron loop (loop A) > polyethylene (PE) loop (loop B)> stainless steel loop (loop C). Ten specific degradation products of E2, produced by chloramination, were identified. Most of the degradation products of E2 chloramination were stable for more than 10 h. The degradation pathways of E2 in the WDS are proposed and briefly discussed. The concentrations of trihalomethanes (THMs), haloacetic acids (HAAs), and halogenated nitromethane (HNMs) during the degradation E2 in WDS were also determined.

N-Halamine-Containing Electrospun Fibers Kill Bacteria via a Contact/Release Co-Determined Antibacterial Pathway

N-Halamine-based antibacterial materials play a significant role in controlling microbial contamination, but their practical applications are limited because of their complicated synthetic process and indistinct antibacterial actions. In this study, novel antibacterial N-halamine-containing polymer fibers were synthesized via an one-step electrospinning of N-halamine-containing polymers without any additives. By adjusting the concentration of precursor and the molecular weight of polymers, the morphology and size of the as-spun N-halamine-containing fibers can be regulated. The as-spun fibers showed antibacterial activity against both Gram-positive and Gram-negative bacteria. After an antibacterial assessment using different biochemical techniques, a combined mechanism of contact/release co-determined killing action was evidenced for the as-spun N-halamine-containing fibers. With the aid of contact action and/or release action, this combined mechanism can allow N-halamines to attack bacteria, making the as-spun fibers wide in the application of antibacterial fields, whatever it is in dry or wet environment. Also, a recycle antibacterial test demonstrated that the as-spun fibers can still offer antibacterial property after five recycle experiments.

Selective and trace determination of monochloramine in river water by chemical derivatization and liquid chromatography/tandem mass spectrometry analysis

Monochloramine (MCA) may enter the aquatic environment through three main sources: wastewater treatment plant effluents, industrial effluents and thermal power plant wastes. Up to date, there are no available data about the concentration levels of this chemical in river water due to lack of appropriate analytical methods. Therefore, sensitive and selective analytical methods for monochloramine analysis in river water are required to evaluate its environmental fate and its effects on aquatic ecosystems. Thus, in this study we describe a highly specific and sensitive method for monochloramine determination in river water. This method combines chemical derivatization of monochloramine into indophenol followed by liquid chromatography coupled to electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS) analysis. Two precursor-to-product ion transitions were monitored (200→127 and 200→154) in positive ionisation mode, fulfilling the criteria of selectivity, in accordance with the European Legislation requirements (decision 2002/657/EC). Ion structures and fragmentation mechanisms have been proposed to explain the selected transitions. Linearity range, accuracy and precision of the method have been assessed according to the French method validation standard NF T90-210. Detecting the derivatized monochloramine (indophenol) in Multiple Reaction Monitoring (MRM) mode provided a limit of quantification of 40 ng L(-1) equivalent monochloramine. Applied to Loire river water (France), the developed method occasionally detected monochloramine at concentrations less than 300 ng L(-1), which could be explained by punctual discharges of water containing active chlorine upstream of the sampling point. Indeed, it is widely reported in the literature that the addition of chlorine to water containing ammonia (e.g., wastewater effluents and river water) may result in the instantaneous formation of monochloramine. The proposed method is a powerful tool that can be used in environmental research (e.g., assessment of environmental fate and generating of ecotoxicological data) as well as in research studies concerning the evaluation of water disinfection efficiency; but it is not currently appropriate for routine use in industrial applications given the complexity of the procedure, the instability of indophenol and the use of certain toxic reagents.

Comparison of a novel extraction-based colorimetric (ABTS) method with membrane introduction mass spectrometry (MIMS): trichloramine dynamics in pool water

Trichloramine is a hazardous disinfection by-product, which is present in chlorinated swimming pools. Although it is primarily taken up by inhalation, the concentration in pool water is important to monitor pool water quality and to assess trichloramine mitigation strategies. To date, scarce data is available on trichloramine concentration in pool water due to the lack of a suitable and easily applicable analytical method. This study presents a novel low cost, colorimetric method which is easy to operate and suitable for on-site measurements of trichloramine concentrations ≥0.05 μM (≥0.01 mg L(-1) as Cl2). The analytical method (termed "extraction-based ABTS method") consists of, (i) trichloramine stripping from pool water samples, (ii) passing it through a solid phase filter, composed of silica gel impregnated with sulfamic acid to eliminate interferences and (iii) trichloramine reaction with the indicator 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to produce the coloured ABTS(•-) radical, which is measured at λ = 405 nm to determine the trichloramine concentration in the pool water sample. A comparison of the extraction-based ABTS method with membrane introduction mass spectrometry (MIMS) for 28 pool samples revealed a good correlation of the two methods. The trichloramine concentration in pool samples is correlated to HOCl, which is the most important factor for its formation. Other parameters such as combined chlorine and pH play a minor role while no correlation between trichloramine and the urea or the TOC concentration was observed. On-site measurements with MIMS in a wading pool over 6 days with a time resolution of 1 h confirmed that trichloramine concentrations strongly responded to changes in free chlorine concentrations. A diurnal measurement of trichloramine with a time resolution of 20 min revealed that trichloramine concentrations reacted quickly and sensitively to the bather load and that urea is probably not the main precursor for its formation.

Environmental mass spectrometry

Environmental mass spectrometry is an important branch of science because it provides many of the data that underlie policy decisions that can directly influence the health of people and ecosystems. Environmental mass spectrometry is currently undergoing rapid development. Among the most relevant directions are a significant broadening of the lists of formally targeted compounds; a parallel interest in nontarget chemicals; an increase in the reliability of analyses involving accurate mass measurements, tandem mass spectrometry, and isotopically labeled standards; and a shift toward faster high-throughput analysis, with minimal sample preparation, involving various approaches, including ambient ionization techniques and miniature instruments. A real revolution in analytical chemistry could be triggered with the appearance of robust, simple, and sensitive portable mass spectrometers that can utilize ambient ionization techniques. If the cost of such instruments is reduced to a reasonable level, mass spectrometers could become valuable household devices.