REVIEW pubs.acs.org/ac
Water Analysis: Emerging Contaminants and Current Issues Susan D. Richardson*,† and Thomas A. Ternes‡ † ‡
National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States Federal Institute of Hydrology, Koblenz, D-56068 Germany
’ CONTENTS Background Major Analysis Trends Sampling and Extraction Trends Chromatography Trends Use of Nanomaterials in Analytical Methods Other Particularly Creative Methods Emerging Contaminants General Reviews New Regulations/Regulatory Methods New Proposed Regulation for Perchlorate in U.S. Drinking Water The New Contaminant Candidate List-3 (CCL-3) The Draft Third Unregulated Contaminants Monitoring Rule (UCMR-3) New Regulatory Methods for Drinking Water EPA Method 539: Hormones EPA Method 538: Pesticides, Quinoline, and Other Organic Contaminants EPA Method 524.3: Purgeable Organic Compounds EPA Method 1615: Enteroviruses and Noroviruses Sucralose and Other Artificial Sweeteners Antimony Nanomaterials PFOA, PFOS, and Other Perfluorinated Compounds Pharmaceuticals and Hormones Environmental Impacts of Pharmaceuticals Biological Transformation Products Elimination/Reaction During Oxidative Water Treatment Opiates and Other Drugs of Abuse Antidepressants Antiviral Drugs Glucocorticoids Antimycotics and Antibiotics Thyroid Hormones Drinking Water Analysis Beta-Blockers Multiresidue Methods New SPE Materials/Procedures New Derivatization Method Enantiomers r 2011 American Chemical Society
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Bioassays Drinking Water and Swimming Pool Disinfection By-Products Drinking Water DBPs Combining Chemistry with Toxicology Discovery of New DBPs New Methods Near Real-Time Methods Improved Method for Total Organic Chlorine and Bromine Alternative Disinfection Technologies Using Iodine, UV, and Other Treatments Nitrosamines Mechanisms of Formation DBPs of Pollutants New Swimming Pool Research Sunscreens/UV Filters Brominated Flame Retardants Benzotriazoles Dioxane Siloxanes Naphthenic Acids Musks Pesticide Transformation Products Perchlorate Algal Toxins Microorganisms Contaminants on the Horizon: Ionic Liquids Biographies Acknowledgment References
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’ BACKGROUND This biennial review covers developments in water analysis for emerging environmental contaminants over the period of 20092010. A few significant references that appeared between January and February 2011 are also included. Analytical Chemistry’s policy is to limit reviews to a maximum of 250 significant Special Issue: Fundamental and Applied Reviews in Analytical Chemistry Published: June 14, 2011 4614
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Analytical Chemistry Table 1. List of Acronyms APCI
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Table 1. Continued
atmospheric pressure chemical ionization
APPI
atmospheric pressure photoionization
BP-3
benzophenone-3
BSTFA
bis(trimethylsilyl)trifluoroacetamide
CCL DBPs
Contaminant Candidate List disinfection byproducts
E1
estrone
E2
17β-estradiol
E3
estriol
EE2
17R-ethinylestradiol
ECD
electron capture detection
EDCs
endocrine disrupting compounds
ELISA EPA
enzyme-linked immunosorbent assay Environmental Protection Agency
ESA
ethane sulfonic acid
ESI
electrospray ionization
FT
Fourier-transform
FTOHs
fluorinated telomer alcohols
GC
gas chromatography
HAAs
haloacetic acids
HXLPP IC
hypercrosslinked polymer resin ion chromatography
ICP
inductively coupled plasma
IR
infrared
LC
liquid chromatography
MALDI
matrix-assisted laser desorption ionization
4-MBC
4-methylbenzylidene camphor
MCL
maximum contaminant level
MIMS MRM
membrane introduction mass spectrometry multiple reaction monitoring
MS
mass spectrometry
MSTFA
N-methyl-N-trimethylsilyltrifluoroacetamide
MX
3-chloro-(4-dichloromethyl)-5-hydroxy-2(5H)-furanone
NCI
negative chemical ionization
NDMA
N-nitrosodimethylamine
NMR NOM
nuclear magnetic resonance natural organic matter
N-EtFOSAA
N-ethyl perfluorooctane sulfonamide acetate
OC
octocrylene
ODPABA
octyl-dimethyl-p-aminobenzoic acid
PCBs
polychlorinated biphenyls
PBDEs
polybrominated diphenyl ethers
PFCs
perfluorinated compounds
PFCAs
perfluorocarboxylic acids
PFDA
perfluorodecanoic acid
PFHxA
perfluorohexanoic acid
PFHpA
perfluoroheptanoic acid
PFNA
perfluorononanoic acid
PFOA
perfluorooctanoic acid
PFOS
perfluorooctane sulfonate
PFOSA
perfluorooctane sulfonamide
PFPrA
perfluoropropanoic acid
PFUnDA
perfluoroundecanoic acid
REACH
Registration, Evaluation, and Authorization of Chemicals
SPE
solid phase extraction
SPME
solid phase microextraction
THMs
trihalomethanes
TOF
time-of-flight
UCMR-3 UPLC
the third Unregulated Contaminants Monitoring Rule ultraperformance liquid chromatography
WWTP
wastewater treatment plant
references and to mainly focus on new trends. Even with a more narrow focus, only a small fraction of the quality research publications could be discussed. As a result, as with the previous review on Water Analysis in 2009,1 this review will not be comprehensive but will highlight emerging contaminant groups and discuss representative papers. I write a similar review article on Environmental Mass Spectrometry, which also focuses on emerging contaminants.2 That review article is somewhat different from this one, in that it focuses on mass spectrometry methods and applications and includes measurements of air, soil/ sediments, and biological samples, in addition to water. This Review on Water Analysis focuses only on water measurements and applications but includes other methodologies besides mass spectrometry. I am excited to have Thomas Ternes join me this year (as in 2005) to cover the section on Pharmaceuticals and Hormones. Because Thomas is an international leader in this area, this Review will be much better with his contribution. We welcome any comments you have on this Review (richardson.
[email protected]). Numerous abstracts were consulted before choosing the best representative ones to present here. Abstract searches were carried out using Web of Science, and in many cases, full articles were obtained. A table of acronyms is provided (Table 1) as a quick reference to the acronyms of analytical techniques and other terms discussed in this Review. A table of useful Websites is also provided (Table 2). Major Analysis Trends. One of the hottest trends is the use of high resolution mass spectrometry (MS) with liquid chromatography (LC) to identify unknown contaminants or to provide further selectivity for known analytes. Full scan and high resolution mass spectrometry have been used with gas chromatography (GC) in a similar fashion for decades, enabling the identification of many environmental contaminants. With recent instrumental development for LC/mass spectrometers, especially time-offlight (TOF), this full scan and high resolution/accurate mass benefit is now being utilized both for target analytes and also for identifying nontarget analytes that are highly polar, nonvolatile, or of high molecular weight and are not amenable to GC. As a result, within a single analytical run, both target and nontarget analytes can be analyzed or identified. In comparison to triple quadrupole mass spectrometers, which operate at unit resolution and generally in the selected reaction monitoring (SRM) or multiple reaction monitoring (MRM) modes for specific target analytes, TOF-mass spectrometers are capable of acquiring fullscan mass spectra at high resolution for all analytes without loss in sensitivity. Because most TOF mass spectrometers have a resolution of at least 10 000 at full-width-half-maximum (fwhm) peak height, isotopic patterns are evident and empirical formulas and chemical structures can be proposed for unknowns or confirmed for target analytes. This also makes it possible to use mass spectral libraries and enable the data file to be reinterrogated months later to find additional unknown contaminants. 4615
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Analytical Chemistry In addition to TOF-mass spectrometers, linear ion trap-Fourier transform (FT)-Orbitrap mass spectrometers are also now being used for similar high resolution-full scan applications. Examples of the use of high resolution-MS in this Review include the identification of pharmaceutical and pesticide transformation products and naphthenic acids. Researchers are also increasingly using isotopically labeled standards (deuterated or 13C-labeled) to allow more accurate quantification in a variety of sample matrixes (especially for wastewater samples, where matrix effects and ion suppression can be substantial). Atmospheric pressure photoionization (APPI) is also increasingly being used with LC/MS because it provides improved ionization for more nonpolar compounds, such as nanomaterials (e.g., fullerenes), polybrominated diphenyl ethers (PBDEs), and naphthenic acids discussed in this Review. Finally, nuclear magnetic resonance (NMR) spectroscopy is increasing in use, as it can provide detailed structural information to confirm tentative structures proposed by LC/MS/MS. In this regard, it is increasingly used to confirm structures of pharmaceutical transformation products. Because NMR is not as sensitive as MS, preparative LC is often used to collect enough material in fractions to enable the analysis of unknowns in complex environmental mixtures. Sampling and Extraction Trends. Solid phase extraction (SPE) remains the most popular means of extraction and concentration, and a new SPE device called Bag extraction was reported during the last 2 years. This bag-SPE consists of polystyrenedivinylbenzene enclosed in a woven polyester fabric, which can be immersed in water samples for solid phase extraction. Measured concentrations of pharmaceuticals have been shown to be comparable for bag-SPE vs Oasis HLB extraction. Benefits include the ease of handling, unattended water extraction, and that no filtration is needed. In addition, new SPE sorbents are available, including Oasis MCX and hypercrosslinked polymer resin (HXLPP) that are being used to capture a broader range of analytes within a single extraction. Solventless extraction techniques, such as solid phase microextraction (SPME), single-drop microextraction (SDME), stir bar sorptive extraction, and hollow-fiber membrane microextraction, also continue to be used in many applications. Polar organic chemical integrative samplers (POCIS) are also popular. These POCIS extraction devices have membranes that allow polar contaminants to be passively extracted from water and wastewater and can allow higher concentration factors and a more integrated sampling (vs spot sampling) over time. The use of molecularly imprinted polymers (MIPs) for selective extraction of environmental contaminants has also continued to grow. MIPs are synthetic polymers made with specific recognition sites that are complementary in shape, size, and functional group to the analyte of interest. The recognition sites mimic the binding sites of antibodies and enzymes. Because they are highly specific to the target analytes of interest, MIPs can be used to extract and isolate them from other matrix components in a complex mixture. MIPs have now been synthesized for a number of emerging contaminants, including pharmaceuticals, pesticides, pesticide metabolites, endocrine disrupting compounds (EDCs), and algal toxins. Examples are cited in this Review for pharmaceuticals. Chromatography Trends. The fastest growing chromatography trend continues to be the use of ultraperformance liquid chromatography (UPLC). UPLC is a recently developed LC technique that uses small diameter particles (typically 1.7 μm) in the stationary phase and short columns, which allow higher pressures and, ultimately, narrower LC peaks (510 s wide). In
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addition to providing narrow peaks and improved chromatographic separations, UPLC dramatically shortens analysis times, often to 10 min or less. Another significant chromatography trend is the use of two-dimensional GC (GCGC). GCGC enables enhanced separations of complex mixtures through greater chromatographic peak capacity and allows homologous series of compounds to be easily identified. It also enables the detection of trace contaminants that would not have been identified through traditional GC. TOF-MS is often used as the detector for GCGC because of its rapid acquisition capability. Examples of the use of GCGC in this Review include the measurement of benzotriazoles, benzothiazoles, and benzosulfonamides. Use of Nanomaterials in Analytical Methods. In addition to nanomaterials being a class of emerging contaminant, they are also being applied in creative ways to aid in the measurement of other emerging contaminants. For example, carbon nanohorns were used in electrochemical immunosensors to enable the rapid detection of microcystin-LR (an algal toxin) in water. Gold nanoparticle labeling was also used with ICP-MS in a new method to measure E. coli O157:H7 in water. This method took advantage of the signal amplification property of gold nanoparticles, monoclonal antibody recognition, and the high sensitivity of ICP-MS. Other Particularly Creative Methods. In addition to the creative use of nanomaterials mentioned above, the last 2 years has seen other particularly creative methods worthy of mention. One such method involved a new microsensor array imprinted onto ordinary compact discs (CDs) to measure microcystins in water. Immunoreactions were detected with a DVD drive, which displayed the readouts in minutes. This method was simple, sensitive, and rapid and could be used in a high-throughput capacity for field use. Another creative method for UV filters involved the use of direct analysis in real-time (DART)-MS to directly analyze the surface of a polydimethylsiloxane-coated stir bar previously used to extract the UV filters from water. While stir-bar sorptive extraction is commonly used in many environmental applications, the direct analysis of analytes sorbed onto these stir bars is a new, creative application that makes the method much more simple and rapid and still allows low ng/L detection limits. Emerging Contaminants. This year, there is one new contaminant class added as a “contaminant on the horizon” to watch: ionic liquids. Ionic liquids are organic salts with a low melting point (400 μg/L in this WWTP effluent, indicating that formulation facilities are a potential source for environmental pharmaceutical contamination. Vazquez-Roig et al. developed an analytical method using SPE and LC/MS/MS for the determination of 14 drugs of abuse and their metabolites (e.g., cannabinoids, amphetamine-like compounds, opiates, and cocainics).103 The best recoveries were obtained using Oasis HLB (200 mg), after comparing seven different SPE materials. Limits of quantification of 600 samples of drinking water, surface, water, and groundwaters were measured in the Rhine and Ruhr region of the North Rhine River (Germany); approximately 65% of the samples contained measurable levels, up to 63 μg/L. While most analytical methods developed utilize sophisticated MS methods, two simpler ones were created recently for measuring pesticides and their metabolites. For example, Sanchez-Bayo published a new LC/electrochemical (EC) detection method to measure amitrole, glyphosate, and its aminomethylphosphonic acid metabolite in environmental waters.218 Passive samplers were used for concentration, and detection limits of 0.03 to 0.3 μg/L were achieved. Dispersive liquidliquid microextraction (DLLME) was used with LC-UV detection in another method by Zhou et al. for measuring dichlorodiphenyltrichloroethane (DDT) and its metabolites in environmental waters.219 Detection limits ranged from 0.32 to 0.51 μg/L. Occurrence and fate studies continue to be conducted for pesticides and their metabolites. In the pan-European survey mentioned earlier by Loos et al., pesticide transformation products were included and were among the most frequently detected and highest concentration of the many analytes measured in European groundwaters.125 For example, desethylatrazine and desethylterbutylazine were found in 55 and 49% of the samples, up to 487 and 266 ng/L, respectively. Occurrence and
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degradation of N-chloridazon was the focus of a study by Buttiglieri et al., who measured >500 samples of groundwater, surface water, and wastewaters using SPE and GC/MS and LC/ MS/MS.220 N-Chloridazon was measured up to 0.89 μg/L, and its degradation product, desphenyl-chloridazon (DPC), was found at much higher levels, up to 7.4 μg/L. Methylated-DPC, another degradation product, was also detected in surface waters. In separate aerobic degradation tests, N-chloridazon was completed converted to DPC, which was stable up to 98 days. Chiron et al. measured pesticides and their transformation products in southern France.221 MCPA [(4-chloro-2-methylphenoxy)acetic acid] was found to transform by photolysis according to the following sequence: MCPA f 4-chloro-2-methylphenol (CMP) f 4-chloro-2-methyl-6-nitrophenol (CMNP). CMNP was more environmentally persistent than the parent compound. While nitration of chlorophenols typically reduces their acute toxicity, there is concern over the genotoxic effects of nitro compounds. Irradiation experiments suggested that the photonitration of CMP to CMNP involved nitrogen dioxide, generated from the photolysis of nitrate and photooxidation of nitrite by OH radical. Fe(III) is also believed to play a role. Finally, Wang et al. identified hydrolysis products of dyfonate, an organophosphorus insecticide, in simulated water treatment using UV and GC/MS detection.222 Two hydrolysis products were identified: thiophenol and phenyl disulfide.
’ PERCHLORATE Perchlorate became an important environmental issue following its discovery in a number of water supplies in the western United States. It has since been found in environmental waters across the United States and in other parts of the world at μg/L levels, as well as in fresh produce, foods, wines, and beverages from many countries, including those in Europe and the Far East. Perchlorate has also been found in biological samples, and it can be transported by pregnant mothers to their developing baby across the placental barrier. Perchlorate is increasingly being found in environmental waters following fireworks displays. As a result, it is now recognized as a worldwide environmental issue, rather than only being limited to the United States. Ammonium perchlorate has been used in solid propellants used for rockets, missiles, and fireworks, as well as highway flares. There is also potential contamination from fertilizers (e.g., Chilean nitrate, where perchlorate co-occurs naturally), and new work has revealed other natural sources of perchlorate. In addition, perchlorate can be a contaminant in sodium hypochlorite (liquid bleach) that is used in drinking water treatment. Perchlorate is an anion that is very water-soluble and environmentally stable. It can accumulate in plants (including lettuce, wheat, and alfalfa), which can contribute to exposure in humans and animals. In addition, perchlorate is not removed by conventional water treatment processes, so human exposure could also come through drinking water. Health concerns arise from perchlorate’s ability to displace iodide in the thyroid gland, which can affect metabolism, growth, and development. Due to these concerns and due to the proportion of the U.S. population exposed to it, the U.S. EPA has now decided to regulate perchlorate under the Safe Drinking Water Act (http:// water.epa.gov/drink/contaminants/unregulated/perchlorate. cfm). The regulation is currently being developed, and there is not a proposed MCL as of yet. (See earlier section on New Regulations/Regulatory Methods for further details.) 4640
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Analytical Chemistry Perchlorate was previously on the U.S. EPA’s CCL (CCL-1 and CCL-2 and is now on the CCL-3; http://water.epa.gov/scitech/ drinkingwater/dws/ccl/ccl3.cfm). Perchlorate was also included in the first UCMR (http://water.epa.gov/lawsregs/rulesregs/ sdwa/ucmr/data.cfm). The U.S. EPA established a reference dose of 0.0007 mg/kg/day, which translates to a drinking water equivalent level (DWEL) of 24.5 μg/L.1 Prior to this national decision to regulate, California had already issued a state regulation of 6 μg/L (in 2007) (www.cdph.ca.gov/certlic/drinkingwater/Pages/Perchlorate.aspx), and several states had issued advisory levels, ranging from 1 to 18 μg/L (www.epa.gov/ fedfac/documents/perchlorate_links.htm#state_adv). There are several EPA Methods for measuring perchlorate in water, including EPA Method 314.2 (2-dimensional IC with suppressed conductivity detection), EPA Method 331 (LC/ESI-MS/MS), and EPA Method 332 (IC/ESI-MS/MS) (www.epa.gov/safewater/methods/analyticalmethods_ogwdw.html; www.epa.gov/ nerlcwww/ordmeth.htm). Parker reviewed the occurrence of perchlorate in the environment and provided evidence of widespread natural occurrence.223 Furdui and Tomassini published a fascinating study of trends and sources of perchlorate in Arctic snow.224 Samples from the Devon Island ice cap in Canada were used to calculate the annual input of atmospherically formed perchlorate. Ice cores were dated between 1996 and 2005, and IC/ESI-MS/MS was used for measurement. Concentrations varied between 1 and 18 ng/L and were correlated with total ozone levels from this area. Data suggested that perchlorate from the Arctic snow was formed in the atmosphere by two different mechanisms: (1) Stratospheric chlorine radicals reacted with ozone year-round, producing concentrations of perchlorate correlated with the total ozone level; (2) During the summer months, perchlorate was likely formed in the troposphere. Interestingly, a deep ice core sample revealed that perchlorate was present in precipitation at similar concentrations more than 2000 years ago. The total estimated amount that reached the Arctic in 2005 was 4186 t. Jackson et al. evaluated the isotopic composition of natural perchlorate indigenous to the southwestern U.S. to understand its origins.225 Stable isotope ratios were measured for perchlorate (δ18O, Δ17O, δ37Cl) and associated nitrate in groundwater from the southern High Plains of Texas and New Mexico and the Middle Rio Grande Basin in New Mexico, unsaturated subsoil in the southern High Plains, and nitrate-rich deposits near Death Valley, California. Results showed that natural perchlorate in the southwestern U.S. has a wide range of isotopic compositions that are distinct from those reported previously from the Atacama Desert of Chile, as well as for synthetic perchlorate. Results from Death Valley samples indicated partial atmospheric formation via reaction with ozone. In contract, perchlorate isotope ratios from western Texas and New Mexico indicated that they were affected by postdepositional oxygen isotope exchange. This study provides important new information on the possibility of divergent perchlorate formation mechanisms and isotopic exchange in biologically active environments. Rao investigated perchlorate formation by ozone oxidation of aqueous chlorine/oxy-chlorine species (Cl, OCl, ClO2, ClO3, and ClO2).226 Higher reaction rates were observed for higher oxidation states of chlorine, except for ClO3, which did not react with ozone. The slow rate of perchlorate production from Cl suggested minimal potential for perchlorate formation in drinking water or wastewater systems that use ozone for treatment. A potential formation pathway for perchlorate from
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Cl was proposed, which involved ClO2 and higher oxy-chlorine radicals and intermediates (e.g., Cl2O6) in its formation. Recent studies have addressed perchlorate occurrence in drinking water. For example, Brandhuber et al. compiled data from the first UCMR, as well as from state surveys carried out in Arizona, California, Massachusetts, and Texas.227 Perchlorate was detected in 26 states, including ∼5% of the large public drinking water systems (serving >10 000 people each). Due to perchlorate contamination, many potable water systems have been taken off-line (estimated at 50 mgd). When detected, perchlorate was generally present at 90% amplification efficiency for tap and river water samples. This technique is important because E. coli O157:H7 easily becomes VBNC under environmental stresses (including disinfection) and escapes detection by current methods. An earlier paper by Liu previously demonstrated how E. coli O157:H7 could enter a VBNC state following chloramination in tap water but could resuscitate themselves back into an infective form.248 As a result, it is important to be able to detect these VBNC forms that can remain a potential health risk.
’ CONTAMINANTS ON THE HORIZON: IONIC LIQUIDS Ionic liquids are organic salts with a low melting point (
