Analysis of disinfection by-products in drinking water by LC–MS and related MS techniques

Characterization of halogenated organic compounds by the Fourier transform ion cyclotron resonance mass spectrometry: A critical review

Halogenated organic compounds (HOCs), widely present in various environments, are generally formed by natural processes (e.g., photochemical halogenation) and anthropogenic activities (e.g., water disinfection and anthropogenic discharge of HOCs), posing health and environmental risks. Therefore, in-depth knowledge of the molecular composition, transformation, and fate of HOCs is crucial to regulate and reduce their formation. Because of the extremely complex nature of HOCs and their precursors, the molecular composition of HOCs remains largely unknown. The Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the most powerful resolution and mass accuracy for the simultaneous molecular-level characterization of HOCs and their precursors. However, there is still a paucity of reviews regarding the comprehensive characterization of HOCs by FT-ICR MS. Based on the FT-ICR MS, the formation mechanism, sample pretreatment, and analysis methods were summarized for two typical HOCs classes, namely halogenated disinfection byproducts and per- and polyfluoroalkyl substances in this review. Moreover, we have highlighted data analysis methods and some typical applications of HOCs using FT-ICR MS and proposed suggestions for current issues. This review will deepen our understanding of the chemical characterization of HOCs and their formation mechanisms and transformation at the molecular level in aquatic systems, facilitating the application of the state-of-the-art FT-ICR MS in environmental and geochemical research.

Identification of chloramination disinfection by-products from phenylalanine in tap drinking water

Phenylalanine (Phe) is widely present in natural water and serves as a precursor of disinfection by-products (DBPs). We reported the identification of chloramination DBPs from Phe in drinking water using ultra-high performance liquid chromatography (UHPLC) coupled with complementary high-resolution quadrupole time-of-flight (QTOF) and triple quadrupole (tQ) tandem mass spectrometry (MS/MS). In the chloraminated Phe water solution, sixteen new DBPs in a total of seventeen were identified based on their accurate mass, MS/MS spectra and ³⁵Cl/³⁷Cl isotopic patterns. Three of these DBPs were verified as benzamide, phenylacetamide, and p-hydroxyphenylacetamide with their standards, while the others were chlorinated derivatives of Phe, hydrazone, amidine, amide and peroxide, in which the unique structures of these DBPs were rarely reported. Their stability and formation process were investigated as well. Furthermore, a method consisting of solid phase extraction (SPE) and UHPLC-MS/MS using dynamic multiple reaction monitoring (dMRM) was developed to investigate these DBPs in authentic waters. Phe, benzamide, phenylacetamide, and N-Cl-2-phenylacetimidamide were detected in chlorinated tap water. Compared with the other identified DBPs, these three DBPs were exceptionally stable and could be formed in wide formation conditions. Our work not only provided ideas for the identification of new chloramination DBPs, but also demonstrated that some DBPs usually generated in the chloramination disinfection process could also be found in the chlorinated drinking water.

Chlorination of benzothiazoles and benzotriazoles and transformation products identification by LC-HR-MS/MS

The fate of four benzotriazoles [1-H-benzotriazole (1-H-BTRi), tolyltriazole (TTRi), xylyltriazole (XTRi) and 1-hydroxy-benzotriazole (1-OH-BTRi)] and three benzothiazoles [benzothiazole (BTH), 2-hydroxy-benzothiazole (2-OH-BTH) and 2-amino-benzothiazole (2-amino-BTH)], during chlorination batch experiments was investigated. In the first step, their degradation under different experimental conditions (applied molar ratio of NaOCl and the target contaminant (m.r.), reaction's contact time, pH value of the reaction's solution and the influence of total suspended solids (TSS) presence) was investigated and their removal kinetics parameters (k_obs and t_1/2) were determined. In the second step, LC-QTOFMS/MS was used for the detection and identification of transformation products (TPs) formed during chlorination, through the application of suspect and non-target screening approaches. Four and five TPs of XTRi and 2-amino-BTH, respectively, were detected and tentatively identified, while 1-H-BTRi was proven to be formed by the chlorination of 1-OH-BTRi. Moreover, since the identified TPs were also detected in spiked wastewater samples, after lab-scale chlorination experiments, toxicity assessment was carried out by ECOSAR calculations for the environmental relevance of their occurrence. The proposed chlorinated TPs were proven to be more toxic than their parent compounds.

Spoilt for choice: A critical review on the chemical and biological assessment of current wastewater treatment technologies

The knowledge we have gained in recent years on the presence and effects of compounds discharged by wastewater treatment plants (WWTPs) brings us to a point where we must question the appropriateness of current water quality evaluation methodologies. An increasing number of anthropogenic chemicals is detected in treated wastewater and there is increasing evidence of adverse environmental effects related to WWTP discharges. It has thus become clear that new strategies are needed to assess overall quality of conventional and advanced treated wastewaters. There is an urgent need for multidisciplinary approaches combining expertise from engineering, analytical and environmental chemistry, (eco)toxicology, and microbiology. This review summarizes the current approaches used to assess treated wastewater quality from the chemical and ecotoxicological perspective. Discussed chemical approaches include target, non-target and suspect analysis, sum parameters, identification and monitoring of transformation products, computational modeling as well as effect directed analysis and toxicity identification evaluation. The discussed ecotoxicological methodologies encompass in vitro testing (cytotoxicity, genotoxicity, mutagenicity, endocrine disruption, adaptive stress response activation, toxicogenomics) and in vivo tests (single and multi species, biomonitoring). We critically discuss the benefits and limitations of the different methodologies reviewed. Additionally, we provide an overview of the current state of research regarding the chemical and ecotoxicological evaluation of conventional as well as the most widely used advanced wastewater treatment technologies, i.e., ozonation, advanced oxidation processes, chlorination, activated carbon, and membrane filtration. In particular, possible directions for future research activities in this area are provided.

Simultaneous determination of three chloroacetic acids, three herbicides, and 12 anions in water by ion chromatography

An ion chromatography method was developed for the simultaneous detection of three soluble herbicides (glyphosate, bentazone and picloram), three chlorine disinfection byproducts (monochloroacetic acid, dichloroacetic acid and trichloroacetic acid) and 12 anions in water (Cl(-), Br(-), SO4(2-), CO3(2-), ClO3(-), ClO4(-), BrO3(-), PO4(3-), NO2(-), NO3(-), CH3COO(-) and COO(-)). High linearity (r(2) > 0.996) was observed for all target analytes for each respective concentration range. The limit of detection and limit of quantitation were between 0.21-0.85 and 0.06-25.46 μg/L, respectively. However, the interference effect of Cl(-), NO3(-) , SO4 (2-) and CO3(2-) on some target analytes must be considered during the analysis. Sample pre-treatment by a hydrogen column (H-column) required to reduce the negative effect of CO3(2-). Additionally, sample pre-treatment by a sliver-hydrogen column (Ag-H-column) is required when Cl(-) > 100 mg/L and SO4(2-) < 50 mg/L, and pre-treatment by both a barium column (Ba-column) and an H-column is required when Cl(-) > 100 mg/L and SO4(2-) > 50 mg/L. When Cl(-) > 100 mg/L, SO4(2-) > 50 mg/L and CO3(2-) > 20 mg/L, the sample pre-treatment by either an Ag-H-Ba-column or an Ag-H-column and Ba-column is required to minimize interference.

Molecular characteristics and differences of effluent organic matter from parallel activated sludge and integrated fixed-film activated sludge (IFAS) processes

A direct comparison between parallel activated sludge and integrated fixed-film activated sludge (IFAS) processes was performed in this study because both treatments received the same primary effluent, although differences may still remain due to different return flow rates. Modern ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was applied to characterize the complexity of effluent organic matter (EfOM) and to evaluate both processes in their abilities to change the EfOM molecular composition. At different stages during the two processes a direct comparison of the performance and changes in molecular composition of the IFAS with those of the activated sludge was undertaken. Large differences in the molecular composition between both processes were only apparent in the early stage of the aeration cells and the first cell of the IFAS possibly due to the higher flow rate and a delay in aerobic bacterial degradation. Despite the double flow rate (0.263 m(3) s(-1)) in the IFAS reactors compared to the activated sludge, by the end of the treatment the EfOM composition of both processes were undistinguishable from each other. However, a much more complex EfOM was generated in both processes, suggesting that bacteria are responsible for an increase in molecular diversity in the effluent.

Evaluation on the generative mechanism and biological toxicity of microcystin-LR disinfection by-products formed by chlorination

To control the environmental risk of microcystin-LR disinfection by-products (MCLR-DBPs), we evaluated their generative mechanisms and biological toxicity by mass spectrometry technology and protein phosphatase inhibition assay. Subject to chlorination, MCLR was totally transformed within 45 min and generated 5 types of MCLR-DBPs with the chemical formulas of C34H54N10O12, C49H76N10O14Cl2, C49H77N10O15Cl, C49H75N10O13Cl, and C49H76N10O14. Isomers for each MCLR-DBP type were identified and separated (products 1-9), indicating that the conjugated diene in Adda residue was a major target site of disinfection. Though, subsequent toxicity test showed the toxicity of MCLR-DBPs on protein phosphatase 1 decreased with the extending of disinfection by and large, these DBPs still possessed certain biological toxicity (especially for product 5). Combined with quantitative analysis, we thought the secondary pollution of MCLR-DBPs in drinking water also deserved further attention. This study offers valid technique support for MCLR-DBPs identification, contributes to a comprehensive cognition on their hazard, and thus has great significance to prevent and control the environmental risk induced by microcystins and their DBPs.

Optimized chromatographic conditions for separation of halogenated acetic acids by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry

Emerging halogenated acetic acids (HAAs), especially mixed halogenated acids such as chlorobromo-, chloroiodo- and bromoiodo-acetic acids, are unregulated disinfection by-products in drinking water. Because these compounds are hydrophilic and strongly acidic, they are difficult to detect at trace levels using approved analytical methods. In the present study, 13 HAAs were effectively separated on three ultra-performance liquid chromatography columns. The effects of changing in the aqueous mobile phase, acidic solutions and cationic volatile ion pair reagents were investigated. The samples were pretreated by filtration, and extraction, while derivatization and concentration procedures were not required. The limits of quantitation for regulated HAAs were between 0.5 μg/L and 1.7 μg/L and for unregulated HAAs were 1.2 and 5.8 μg/L, especially for the iodinated acetic acids were 1.5 and 2.1 μg/L. The method was applied to two finished water samples collected in China (Shanghai and Xuzhou) from water treatment plants that use chlorine for disinfection. Multiple unregulated HAAs were found in the two samples, but iodoacids were only detected in the water sample from Shanghai, which could be attributed to the characteristics of the source water. The presence of unregulated HAAs, especially mixed bromo- and iodoacetic acids, in the finished water samples could affect human health, and this warrants further investigation.

Evidence of soluble microbial products accelerating chloramine decay in nitrifying bulk water samples

The discovery of a microbially derived soluble product that accelerates chloramine decay is described. Nitrifying bacteria are believed to be wholly responsible for rapid chloramine loss in drinking water systems. However, a recent investigation showed that an unidentified soluble agent significantly accelerated chloramine decay. The agent was suspected to be either natural organic matter (NOM) or soluble microbial products (SMPs). A laboratory scale reactor was fed chloraminated reverse osmosis (RO) treated water to eliminate the interference from NOM. Once nitrification had set in, experiments were conducted on the reactor and feed waters to determine the identity of the component. The study showed the presence of SMPs released by microbes in severely nitrified waters. Further experiments proved that the SMPs significantly accelerated chloramine decay, probably through catalytic reaction. Moreover, application of common protein denaturing techniques stopped the reaction implying that the compound responsible was likely to be a protein. This significant finding will pave the way for better control of chloramine in the distribution systems.

Transformation of phenazone-type drugs during chlorination

Chlorination is one of the most popular disinfection steps for water treatment in Europe. However, chlorine can react with pharmaceuticals and other micropollutants leading to either their elimination or by-products being formed. These by-products are frequently not identified and therefore the consequences of chlorination can be underestimated. In this work, the degradation of two analgesics and antipyretics, phenazone (antipyrine) and propyphenazone, during chlorination was investigated by liquid chromatography-mass spectrometry (LC-MS). A quadrupole-time-of-flight (Q-TOF) system was used to follow the time course of the pharmaceuticals, and also used in the identification of the by-products. The degradation kinetics was investigated at different concentrations of chlorine (1-10 mg/L), bromide (0-100 μg/L) and sample pH (5.7-8.3) by means of a Box-Behnken experimental design. Depending on these factors, half-lives were in the ranges: 0.9-295 s for phenazone and 0.4-173 s for propyphenazone. Also, it was observed that chlorine concentration was a significant factor for propyphenazone, resulting in increased degradation rate as it is increased. The transformation path of these drugs consisted mainly of halogenations, hydroxylations and dealkylations. After several days of reaction two derivatives remained stable for phenazone: chloro-hydroxy-phenazone and N-demethyl-chloro-hydroxy-phenazone and two for propyphenazone: N-demethyl-hydroxy-propyphenazone and N-demethyl-chloro-hydroxy-propyphenazone. Moreover, experiments conducted with real water matrices, tap and surface water, showed that reaction, and formation of by-products, can take place both at the emission source point (household) and during drinking water production.

Identification of Halohydrins as Potential Disinfection By-Products in Treated Drinking Water

In 2001, two potential disinfection by-products (DBPs) were tentatively identified as 1-aminoxy-1-chlorobutan-2-ol (DBP-A) and its bromo analogue (DBP-B) (Taguchi 2001). Subsequently it became clear, by consulting an updated version of the NIST database, that their mass spectra are close to those of the halohydrins 4-chloro-2-methylbutan-2-ol and 3-bromo-2-methylbutan-2-ol. To establish the structures of these DBPs, additional mass spectrometric experiments, including Fourier transform ion cyclotron resonance (FTICR), were performed on treated drinking water samples and authentic halohydrin standards. It appears that DBP-A is 3-chloro-2-methylbutan-2-ol and that DBP-B is its bromo analogue. DBP-B has been detected in ozonated waters containing bromide. Our study also shows that these DBPs can be laboratory artefacts, generated by the reaction of residual chlorine in the sample with 2-methyl-2-butene, the stabilizer in the CH2Cl2 used for extraction. This was shown by experiments using CH2Cl2 stabilized with deuterium labelled 2-methyl-2-butene. Quenching any residual chlorine in the drinking water sample with sodium thiosulfate minimizes the formation of these artefacts.

Screening of N-nitrosamines in tap and swimming pool waters using fast gas chromatography

N-Nitrosamines (NAms) are suspected human carcinogens that have been identified as drinking water and wastewater pollutants. In this work, a sensitive screening/confirmation method was proposed for the determination of the most toxic NAms that can be found in water samples (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, N-nitrosomorpholine, N-nitrosopiperidine, and N-nitrosopyrrolidine). A sample volume of 250 mL was first preconcentrated in an automatic SPE unit and then the extract was concentrated to a final volume of 10 microL (providing a preconcentration factor of 25,000). Aliquots of the extract were subjected to a rapid screening process (1.6 min) by using a short capillary polar column (1.5 m length) and GC with nitrogen-phosphorous detection. In this way, the high number of samples to be tested routinely in a water laboratory is simplified due to a reduction in the analysis time. Thus, the screening method acts as a filter that indicates whether target analytes are present, above or below the cut-off level (3.8 or 10.4 ng/L), giving no false negatives at concentrations below the guide values for NAms in drinking water established by different countries. Positive samples (tap and swimming pool waters) were then confirmed by GC-MS detection.

Determination of bromate in water samples using post column derivatization method with triiodide

This paper describes the application of the method of post-column derivatization with triiodide and UV detection at 352 nm for the determination of bromate in drinking water, mineral water and swimming pool water samples. Optimized analytical conditions were further validated in terms of accuracy, precision, linearity, limit of detection and limit of quantification. The method detection limit was at the level of 0.4 μg/L, and the spiked recovery for bromate was in the range of 92% - 104%. The method did not need a special sample treatment and was successfully applied to the analysis of bromate at the required value that is below 2.5 μg/L.

Trace determination of nine haloacetic acids in drinking water by liquid chromatography-electrospray tandem mass spectrometry

A simple, fast and sensitive liquid chromatography-electrospray tandem mass spectrometry method was established for trace levels of nine haloacetic acids (HAAs) in drinking water. Water samples were removed of residual chlorine by adding L-ascorbic acid, and directly injected after filtered by 0.22 microm membrane. Nine HAAs were separated by liquid chromatography in 7.5 min, and the limits of detection were generally between 0.16 and 0.99 microg/L except for chlorodibromoacetic acid (1.44 microg/L) and tribromoacetic acid (8.87 microg/L). The mean recoveries of nine target compounds in spiked drinking water samples were 80.1-108%, and no apparent signal suppression was observed. Finally, this method was applied to determine HAAs in the tap water samples collected from five waterworks in Shandong, China. Nine HAAs except for monochloroacetic acid, monobromoacetic acid, dibromochloroacetic acid and tribromoacetic acid were detected, and the total concentrations were 7.79-36.5 microg/L. The determination results well met the first stage of the Disinfectants/Disinfection By-Products (D/DBP) Rules established by U.S.EPA and Guidelines for Drinking-water Quality of WHO.

Alveolar air and urine analyses as biomarkers of exposure to trihalomethanes in an indoor swimming pool

The exposure of workers and swimmers at an indoor swimming pool to trihalomethanes (THMs) as a consequence of water chlorination was evaluated by analyzing alveolar air and urine samples. Environmental monitoring of THMs in water and ambient air was also performed in order to assess the possible correlation between environmental and biological samples. The sampling was done concurrently, taking the urine and alveolar air samples before and after the work shift for 15 workers and the swimming activity for 12 swimmers. A high THM uptake was observed in alveolar air and urine of subjects exposed, with chloroform being the most abundant THM. Mean chloroform levels in alveolar air and urine before exposure were 4 microg/ m3 and 475 ng/L, respectively. After 2 h of exposure, concentration increases of ca. 8 times in alveolar air and 2 times in urine were observed in workers. After 1 h swimming, the increases found in swimmers were ca. 20 and 3 times in alveolar air and urine, respectively. High increases have also been observed in bromodichloromethane levels. We have obtained excellent correlations between the chloroform concentrations found in the swimming pool ambient air/alveolar air, and between the urine/ alveolar air of the participants after exposure (r > 0.9). In conclusion, alveolar air provides better response sensitivity and shorter reaction time to external exposure than urine, being therefore the most sensitive biomarker.

Drowning in disinfection byproducts? Assessing swimming pool water

Disinfection is mandatory for swimming pools: public pools are usually disinfected by gaseous chlorine or sodium hypochlorite and cartridge filters; home pools typically use stabilized chlorine. These methods produce a variety of disinfection byproducts (DBPs), such as trihalomethanes (THMs), which are regulated carcinogenic DBPs in drinking water that have been detected in the blood and breath of swimmers and of nonswimmers at indoor pools. Also produced are halogenated acetic acids (HAAs) and haloketones, which irritate the eyes, skin, and mucous membranes; trichloramine, which is linked with swimming-pool-associated asthma; and halogenated derivatives of UV sun screens, some of which show endocrine effects. Precursors of DBPs include human body substances, chemicals used in cosmetics and sun screens, and natural organic matter. Analytical research has focused also on the identification of an additional portion of unknown DBPs using gas chromatography (GC)/mass spectrometry (MS) and liquid chromatography (LC)/MS/MS with derivatization. Children swimmers have an increased risk of developing asthma and infections of the respiratory tract and ear. A 1.6-2.0-fold increased risk for bladder cancer has been associated with swimming or showering/bathing with chlorinated water. Bladder cancer risk from THM exposure (all routes combined) was greatest among those with the GSTT1-1 gene. This suggests a mechanism involving distribution of THMs to the bladder by dermal/inhalation exposure and activation there by GSTT1-1 to mutagens. DBPs may be reduced by engineering and behavioral means, such as applying new oxidation and filtration methods, reducing bromide and iodide in the source water, increasing air circulation in indoor pools, and assuring the cleanliness of swimmers. The positive health effects gained by swimming can be increased by reducing the potential adverse health risks.

Structural Identification of Highly Polar Nontarget Contaminants in Drinking Water by ESI-FAIMS-Q-TOF-MS

Drinking water is a complex mixture that contains thousands of naturally occurring and anthropogenic contaminants. Liquid chromatography-mass spectrometry (LC-MS) methods have gained a tremendous popularity in monitoring nonvolatile, highly polar, and thermally labile components in drinking water. It is well recognized, however, that there are difficulties or limitations of LC-MS methods associated with (1) significant resources (time and effort) involved in sample preparation (preconcentration, fractionation, separation), (2) low screening capacity for target contaminants, and (3) insufficient capabilities for structural identification (elucidation) of nontarget contaminants. Consequently, LC-MS methods are mainly used for the detection of target contaminants (compounds identified in drinking water before), seldom for the structural identification of abundant nontarget pollutants (unidentified pollutants in drinking water), and almost never for the structural identification of nontarget components at a trace level. The paper presents a new method of electrospray ionization high field asymmetric waveform ion mobility spectrometry mass spectrometry (ESI-FAIMS-MS), which can detect a large number of water pollutants in a quick and convenient fashion without preconcentration, fractionation, derivatization, or column separation. Most importantly, the method provides structural identification of nontarget contaminants including species present in drinking water at a sub-parts-per-billion concentration level. The identification of previously unknown contaminants was based on mass measurements of investigated ions and their fragments in mass and tandem mass spectrometry. Elemental compositions of these ions, determined by mass measurements, were used to link dissociation patterns of investigated species with their chemical structures. Characterization of nontarget contaminants of chlorine-treated drinking water by ESI-FAIMS-MS has revealed many previously unknown disinfection byproducts. The most intriguing compound, from a group of highly polar hydroxycarboxylic acids discovered in the study, was the most abundant component of drinking water, glycolic acid. Glycolic acid (toxic to kidneys and associated with a moderate maternal toxicity) has never been considered as a drinking water contaminant, despite the fact that it is present in drinking water at a higher concentration (high ppm) than concentrations of highly polar water pollutants that had attracted most attention in the past. The process of structural elucidation of discovered pollutants, including ultratrace contaminants representing a variety of carboxylic acids, will be presented in detail. The structural identification of highly polar contaminants in drinking water presented in the paper is rarely reported in the literature. The key experimental feature of the ESI-FAIMS-MS method is FAIMS separation, which significantly improves the identification capabilities of mass spectrometry.