skip to main content

Title: Rapid, high-sensitivity analysis of oxyhalides by non-suppressed ion chromatography-electrospray ionization-mass spectrometry: application to ClO 4 − , ClO 3 − , ClO 2 − , and BrO 3 − quantification during sunlight/chlorine advanced oxidation
A rapid and sensitive method is described for measuring perchlorate (ClO 4 − ), chlorate (ClO 3 − ), chlorite (ClO 2 − ), bromate (BrO 3 − ), and iodate (IO 3 − ) ions in natural and treated waters using non-suppressed ion chromatography with electrospray ionization and tandem mass spectrometry (NS-IC-MS/MS). Major benefits of the NS-IC-MS/MS method include a short analysis time (12 minutes), low limits of quantification for BrO 3 − (0.10 μg L −1 ), ClO 4 − (0.06 μg L −1 ), ClO 3 − (0.80 μg L −1 ), and ClO 2 − (0.40 μg L −1 ), and compatibility with conventional LC-MS/MS instrumentation. Chromatographic separations were generally performed under isocratic conditions with a Thermo Scientific Dionex AS16 column, using a mobile phase of 20% 1 M aqueous methylamine and 80% acetonitrile. The isocratic method can also be optimized for IO 3 − analysis by including a gradient from the isocratic mobile phase to 100% 1 M aqueous methylamine. Four common anions (Cl − , Br − , SO 4 2− , and HCO 3 − /CO 3 2− ), a natural organic matter isolate (Suwannee River NOM), and several real water samples were tested to examine influences of natural water constituents on oxyhalide detection. Only ClO 2 − quantification was significantly affected – by elevated chloride concentrations (>2 mM) and NOM. The method was successfully applied to quantify oxyhalides in natural waters, chlorinated tap water, and waters subjected to advanced oxidation by sunlight-driven photolysis of free available chlorine (sunlight/FAC). Sunlight/FAC treatment of NOM-free waters containing 200 μg L −1 Br − resulted in formation of up to 263 ± 35 μg L −1 and 764 ± 54 μg L −1 ClO 3 − , and up to 20.1 ± 1.0 μg L −1 and 33.8 ± 1.0 μg L −1 BrO 3 − (at pH 6 and 8, respectively). NOM strongly inhibited ClO 3 − and BrO 3 − formation, likely by scavenging reactive oxygen or halogen species. As prior work shows that the greatest benefits in applying the sunlight/FAC process for purposes of improving disinfection of chlorine-resistant microorganisms are realized in waters with lower DOC levels and higher pH, it may therefore be desirable to limit potential applications to waters containing moderate DOC concentrations ( e.g. , ∼1–2 mg C L −1 ), low Br − concentrations ( e.g. , <50 μg L −1 ), and circumneutral to moderately alkaline pH ( e.g. , pH 7–8) to strike a balance between maximizing microbial inactivation while minimizing formation of oxyhalides and other disinfection byproducts.  more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Environmental Science: Water Research & Technology
Page Range / eLocation ID:
2580 to 2596
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Free chlorine and free bromine ( e.g. , HOCl and HOBr) are employed as disinfectants in a variety of aqueous systems, including drinking water, wastewater, ballast water, recreational waters, and cleaning products. Yet, the most widely used methods for quantifying free halogens, including those employing N , N -diethyl- p -phenylenediamine (DPD), cannot distinguish between HOCl and HOBr. Herein, we report methods for selectively quantifying free halogens in a variety of aqueous systems using 1,3,5-trimethoxybenzene (TMB). At near-neutral pH, TMB reacted on the order of seconds with HOCl, HOBr, and inorganic bromamines to yield halogenated products that were readily quantified by liquid chromatography or, following liquid–liquid extraction, gas chromatography-mass spectrometry (GC-MS). The chlorinated and brominated products of TMB were stable, and their molar concentrations were used to calculate the original concentrations of HOCl (method quantitation limit (MQL) by GC-MS = 15 nmol L −1 = 1.1 μg L −1 as Cl 2 ) and HOBr (MQL by GC-MS = 30 nmol L −1 = 2 μg L −1 as Cl 2 ), respectively. Moreover, TMB derivatization was efficacious for quantifying active halogenating agents in drinking water, pool water, chlorinated surface waters, and simulated spa waters treated with 1-bromo-3-chloro-5,5-dimethylhydantoin. TMB was also used to quantify bromide as a trace impurity in 20 nominally bromide-free reagents (following oxidation of bromide by HOCl to HOBr). Several possible interferents were tested, and iodide was identified as impeding accurate quantitation of HOCl and HOBr. Overall, compared to the DPD method, TMB can provide lower MQLs, larger linear ranges, and selectivity between HOCl and HOBr. 
    more » « less
  2. Disinfection is an essential process for both potable water and wastewater treatment plants. However, disinfection byproducts (DBPs) like trihalomethanes (THMs), haloacetonitriles (HANs), and nitrosamines (NOAs) are formed when organic matter precursors react with disinfectants such as chlorine, chloramine, and ozone. Formation of DBPs is strongly associated with the type of water source, type of disinfectant, and organic matter concentration, which can have seasonal variation. In this study, water samples were collected from 20 different intra-watershed locations, which included urban runoff (with and without the influence of unsheltered homeless populations), wastewater effluent discharges, and a large, terminal reservoir that serves as the local drinking water source. Samples were collected on dry and rainy days, which represent seasonal samples. DBP formation potential (FP) tests were conducted at consistent pH, contact time, and temperature. THMs, NOAs, and HANs were analyzed by gas chromatography-mass spectrometry (GC-MS). The FP tests performed on these water samples revealed that chlorine formed the highest THM concentrations, while THM concentrations were low for the ozone FP test as expected. Chloramine produced the greatest HAN concentrations, with dichloroacetonitrile representing the highest concentration. With respect to sample type, more DBPs were formed at the non-wastewater-impacted runoff sites as compared to the wastewater effluent discharge sites. With respect to TOC levels, rain event samples for all locations had higher TOC concentrations compared to dry sampling days. Similarly, rain event samples showed increased DBP formation; a significant amount of precursors for THMs was found in runoff waters that were influenced by wastewater effluent discharges and unsheltered homeless locations (concentration of total THMs for chlorine FP test was >200 μg/L). Therefore, urban runoff waters should be considered as potential sources of DBP precursors to drinking water source waters, and runoff water is prone to seasonal variation. 
    more » « less
  3. null (Ed.)
    This study assessed the disinfection byproduct (DBP) risks of algal impacted surface waters and the effects of peracetic acid (PAA) pre-oxidation on DBP risks. Authentic samples from three eutrophic lakes were collected over a 13-week period during the algal bloom season. The formation of 11 DBPs (four trihalomethanes, four haloacetonitriles, two haloketones, and trichloronitromethane) in these samples was assessed under uniform formation conditions (UFC) approximating drinking water disinfection. Trihalomethanes formed in the greatest abundance (90–370 μg L −1 ), followed by haloacetonitriles (6.5–87 μg L −1 ), haloketones (0.4–11.4 μg L −1 ), and trichloronitromethane (0.3–9.7 μg L −1 ). Total chlorophyll, a common indicator of algal activity, was not found to correlate with DBP yields. On the other hand, the yields of trichloronitromethane and haloacetonitriles correlated with nitrite/nitrate concentrations and DON concentrations in the samples, respectively. PAA pre-oxidation reduced the formation of trihalomethanes in the subsequent UFC tests in 80% of the samples, but promoted the formation of haloacetonitriles and trichloronitromethane in 70% and 50% of the samples, respectively. Analyses of DOC, DON, SUVA, and fluorescence excitation–emission matrices suggest that PAA pre-oxidation can alter the DBP precursors of a sample through the release of high haloacetonitrile/trichloronitromethane-yielding organic matter from algal cells and the oxidative transformation of existing and newly released dissolved organic matter. The results of this study, obtained from authentic surface water samples, suggest that mixed organic matter dynamics is an important consideration for the DBP risks of algal-impacted waters. 
    more » « less
  4. Chlorinated and brominated forms of salicylic acid (SA) have recently been identified as a new class of disinfection byproducts (DBPs) in drinking water. Herein, we report the inherent reactivity of several aqueous halogenating agents toward hydrogen salicylate, the predominant species of salicylic acid under environmental conditions. Using synthetic waters, halogenation rates associated with the formation of 3-chloro, 5-chloro, 3-bromo, and 5-bromosalicylate were measured as a function of pH, [Cl − ], [Br − ], free chlorine dose, and the initial concentration of SA. Halogenating-agent specific second-order rate constants were determined and decrease in the order: BrCl > BrOCl > Br 2 > Br 2 O > Cl 2 > Cl 2 O > HOBr > HOCl. Chloride is capable of enhancing rates of bromination and chlorination, ostensibly by promoting the formation of BrCl and Cl 2 , both of which are several orders of magnitude more inherently reactive than HOBr and HOCl, respectively. Kinetic data also support the participation of salicyloyl hypochlorite as a chlorination intermediate capable of influencing chlorination rates at pH >8. Experiments in which buffer concentrations were varied indicate that phosphate buffers can enhance rates of SA bromination but not chlorination; carbonate and borate buffers did not appreciably influence rates of bromination or chlorination. Under conditions representative of chlorinated drinking water, rates of SA bromination will generally exceed rates of SA chlorination. The results discussed herein demonstrate the importance of considering halogenating agents beyond HOBr and HOCl when developing kinetic models to describe and predict halogenation rates and selectivity in waters containing free chlorine. 
    more » « less
  5. Exposure to lead, a toxic heavy metal, in drinking water is a worldwide problem. Lead leaching from lead service lines, the main contamination source, and other plumbing materials is controlled by the plumbosolvency of water. Square wave anodic stripping voltammetry (SWASV) has been greatly explored as a rapid and portable technique for the detection of trace Pb 2+ ions in drinking water. However, the impact of water quality parameters (WQP) on the SWASV technique is not well understood. Herein, SWASV was employed to detect 10 μg L −1 Pb 2+ and determine trends in the stripping peak changes in simulated water samples while individually varying the pH, conductivity, alkalinity, free chlorine, temperature, and copper levels. The pH and conductivity were controlled using the buffer 3-( N -morpholino)propanesulfonic acid (MOPS), and NaNO 3 , respectively and kept at pH = 7.0 and conductivity = 500 μS cm −1 when exploring other WQPs. The working electrode, a gold-nanoparticle-modified carbon nanotube fiber cross-section (AuNP-CNT f -CS) electrode provided sufficiently sharp and prominent peaks for 10 μg L −1 Pb 2+ detection as well as good reproducibility, with a relative error of 5.9% in simulated water. We found that conductivity, and temperature had a proportional relationship to the peak height, and pH, alkalinity, free chlorine, and copper had an inverse relationship. In addition, increasing the copper concentration caused broadening and shifting of the Pb 2+ stripping peak. At extremely low conductivities (<100 μS cm −1 ), the voltammograms became difficult to interpret owing to the formation of inverted and distorted peaks. These trends were then also observed within a local drinking water sample in order to validate the results. 
    more » « less