Emerging Pollutants

M. Petrovic ∗, †, M. Farré^†, E. Eljarrat^†, M.S. Díaz-Cruz^† and D. Barceló^∗∗, ^∗Catalan Institute of Water Research (ICRA), Girona, Spain, ^†Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Spain, ^∗∗King Saud University, Riyadh, Saudi Arabia

Outline

14.1 Introduction

Impressive improvements in detection limits for organic contaminants, mostly due to the development of hyphenated chromatography–mass spectrometry (MS) techniques, have pushed the target concentrations from the microgram to the nanograms or picograms per liter range [1]. With the progresses in analytical instrumentation, extraction techniques have also become more simple, fast, and inexpensive, providing the enrichment of analytes of interest from complex environmental matrices [2]. All these improvements led to the detection of many harmful compounds at the levels at which they have a biological effect in the environment and several new or previously ignored or unrecognized contaminants have come under scrutiny.

Several groups of organic compounds have emerged as particularly relevant:

• Biotoxins, emerging toxins.

• Brominated flame retardants, new classes other than polybrominated diphenyl ethers.

• Disinfection by-products.

• Drugs of abuse and their metabolites.

• Hormones and other endocrine-disrupting compounds.

• Nanomaterials.

• Organophosphate flame retardants and plasticizers.

• Perfluorinated compounds.

• Pharmaceuticals and personal care products.

• Polar pesticides and their degradation–transformation products.

• Siloxanes.

• Surfactants and their metabolites.

All these compound classes are referred to as emerging contaminants, which does not necessarily mean “new substances,” that is, newly introduced chemicals and their degradation products, metabolites, or by-products but also refers to compounds, including naturally occurring compounds, with previously unrecognized adverse effects on ecosystems. The study of their occurrence, fate, and behavior in the environment has been the focus of attention by the scientific community during recent years and concern is raised regarding the risks posed by these emerging contaminants to humans.

This chapter attempts to survey the current state of the art in the application of modern LC–MS techniques to environmental analysis of emerging contaminants, which is a very broad, very active field. Consequently, a large number of papers are published every year and comprehensive coverage of all contaminant classes and trends is an impossible task. Therefore, we focus on recent trends in the application of LC–MS, including sample preparation, in the environmental analysis of several important classes of emerging contaminants, such as pharmaceuticals and personal care products, drugs of abuse, endocrine-disrupting compounds, perfluorinated compounds, brominated flame retardants, and nanoparticles.

14.2 General Trends

Currently, the main breakthrough in the analysis of emerging environmental contaminants is observed in the application of tandem and hybrid LC–MS techniques with several notable trends [3]:

• Shift toward high-throughput methods involving fast chromatography or on-line coupling of sample preparation.

• Shift toward multiresidue methods vs. compound–class-specific methods.

• Shift toward polar contaminants.

• Shift from parent compound analysis to the analysis of metabolites and transformation product.

14.2.1 Fast Chromatography

Among the different modern approaches to achieving fast separation without compromising resolution and separation efficiency, two approaches are frequently used in environmental analysis of emerging contaminants: liquid chromatography at ultra high pressures using sub-2-μm-particle packed columns (ultra high-pressure liquid chromatography, UHPLC) and chromatography using fused-core columns.

Rapid multiresidue screening of organic contaminants in environmental samples is one of the most promising fields of application of UHPLC technology. Recently, UHPLC–MS multiresidue methods were developed for the analysis of pharmaceuticals and steroid hormones in river and wastewater [4,5], pharmaceuticals and endocrine-disrupting compounds (EDCs) in sewage sludge and sediment [6], drugs of abuse in river and wastewater [7,8], UV filters in water [9,10], perfluorinated compounds in river water and fish [11], and polar pesticides in wastewater [12].

Several successful applications of fused-core columns for the analysis of emerging contaminants in environmental samples are described in the literature, including the analysis of pharmaceuticals and their metabolites in wastewater [13], personal care products (PCPs; antimicrobials, preservatives), benzotriazole UV stabilizers and organophosphorus compounds in fish tissue [14], sulphonamide antibiotics in fish [15], bisphenol A and its chlorinated metabolites in wastewater and drinking water [16], and drugs of abuse and metabolites in wastewater [17].

14.2.2 On-Line SPE–LC–MS Coupling

Over the past 10 years, there has been an increase in the use of automated instruments that integrate the extraction, purification, and detection steps. Several generic approaches have been developed for on-line sample extraction coupled to LC–MS using different extraction supports or sorbents, such as disposable solid–phase extraction (SPE) cartridges, restricted access materials (RAM), large-size particles, or monolithic materials [18]. The most often used automated commercial systems include Symbiosis and Prospekt-2 systems manufactured by Spark Holland, using disposable SPE cartridges. Recently, applications have been developed for the analysis of illicit drugs [19,20], multiclass pharmaceuticals [21,22], biocides and pesticides [23], pesticides [24], PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid) [25]. Another approach for automated and integrated extraction, preconcentration and cleanup is based on turbulent-flow chromatography (TFC), using large diameter particles and has shown great potential for on-line sample pretreatment, but applications in environmental analysis are still scarce [26].

14.2.3 Multiresidue Methods

Due to their comprehensive approach, multiresidue analytical methods have become preferred tools for tracking down different compound classes at low nanogram per liter levels. They allow determination of a large number of micropollutants in a single analysis, thus reducing its time and cost. In an ideal case, a multiclass–multiresidue analytical method for determination of trace organic pollutants in environmental matrices should fulfill several criteria, such as

1. Simultaneous extraction and preconcentration of all target analytes in a single step.

2. Limits of quantification (LOQs) low enough for each analyte.

3. Substance-specific detection.

4. Applicability to various matrices (e.g., natural water, drinking water, wastewater).

Some of the recent examples of multiresidue methods for emerging contaminants in environmental samples are a method for the analysis of 34 polar organic compounds (pharmaceutical compounds, pesticides and their degradation products, perfluorinated acids, and endocrine disrupting compounds) in river water [27]; a method for 46 basic, neutral, and acidic compounds, including selected iodinated contrast media, analgesics, anti-inflammatories, stimulants, beta blockers, antibiotics, lipid regulators, antihistamines, psychiatric drugs, herbicides, corrosion inhibitors, and the gastric acid-regulator pantoprazole [28]; a method for 60 pharmaceuticals and illicit drugs in suspended particulate matter [29]; a method for 65 stimulants, opiod and morphine derivatives, benzodiazepines, antidepressants, dissociative anaesthetics, drug precursors, human urine indicators, and their metabolites in wastewater and surface water [7]; a method for 70 high-priority pharmaceuticals (of the U.S. EPA) in water [30]; a method for 23 emerging pollutants belonging to personal care products (antimicrobials, preservatives), benzotriazole UV stabilizers, and organophosphorus compounds in fish using high-speed solvent extraction (HSSE), followed by silica gel cleanup and ultra fast liquid chromatography coupled with tandem mass spectrometry (UFLC–MS/MS) analysis [31].

However, it is important to mention that simultaneous analysis of multiclass compounds with quite different physicochemical characteristics often imposes compromises between the performance parameters and extraction, separation, and detection conditions acceptable for the majority of compounds but not optimal for all of them. Another potential pitfall of multiresidue determination methods is an enhanced matrix effect, particularly when studying complex samples, such as wastewater. In multiresidue methods, usually simple sample pretreatment is used to reduce the analysis time. This simplification of the sample cleanup step can result in dirty extracts with high coextractive substance content, which may lead to significant ion suppression (or enhancement) when using LC–MS/MS.

14.3 Target Analysis of Specific Contaminant Groups Using LC–MS

14.3.1 Brominated Flame Retardants

Flame retardant (FR) compounds are a structurally diverse group of chemicals added to or reacted with polymers, and they are used in plastics, textiles, electronic circuitry, and other materials to reduce the risk of fire. One of these groups of compounds is brominated FRs (BFRs), some of which are ubiquitous, and many of which have been detected in biota, sediments, air, water, marine mammals, and even human milk.

Brominated flame retardants have typically been analyzed using gas chromatography (GC)–MS but the high injection port temperatures required to transfer the analytes to the GC column can result in degradation of some desired compounds. This could occur in the case of highly polybrominated diphenyl ethers (PBDEs) and other BFRs (e.g., hexabromocyclododecane, HBCD). Moreover, in the case of tetrabromobisphenol A (TBBPA) or PBDE metabolites, a derivatization step is needed, giving more possibilities for error, because derivatization is not always reproducible and quantitative. LC–MS/MS appears to be the methodology of choice to analyze TBBPA, HBCD diastereoisomers, and HBCD enantiomers because no derivatization is needed and isomeric separation is obtained [32]. Also important is the recent development of methods to identify metabolites of PBDEs and HBCD by LC–MS/MS, thereby avoiding the problems of derivatization with diazomethane.

LC–MS/MS appears to be the method of choice for TBBPA analysis because no derivatization of the phenolic group is required [33–35]. To obtain a good chromatographic separation of TBBPA, it is important to take into account its great dependence on the mobile phase composition. Chu, Haffner, and Letcher [34] found that, using methanol as the mobile phase, the response of the target compound was about one third greater than when using acetonitrile. The most suitable LC–MS interface for TBBPA analysis is electrospray ionization (ESI) operating in the negative ion mode. Tollbäck, Crescenzi, and Dyremark [36] reported limits of detection (LODs) 30–40 times lower than with atmospheric pressure photoionization (APCI). In terms of sensitivity, LC–ESI–MS can be competitive with published GC–EI (electron ionization)–MS techniques with LODs in the ppt range [37].

To obtain HBCD diastereoisomer-specific data, it is essential to use LC, since, using GC, the diastereoisomers interconvert at temperatures above 160°C. Therefore, LC–MS/MS using ESI or APCI are versatile tools for the isomer-specific determination of trace levels of HBCDs, monitoring the specific transitions m/z 640.6 to m/z 78.9 and 80.9. An example of separation using permethylated β-cyclodextrin column is shown in Figure 14.1.

FIGURE 14.1 Enantiomeric HBCD separation by LC-ESI-MS/MS for a standard solution, using a Nucleodex β-PM (200 mm × 4.0 mm, 5 μm) chiral column.

LC–MS/MS is also used to analyze metabolites and transformation products of BFRs. Abdallah et al. [38] describe HBCD transformation-product detection in dust samples by LC–MS/MS analysis. These products were identified as four pentabromocyclododecene (PBCDe) isomers and two congeners of tetrabromocyclododecadienes (TBCDe). Brandsma et al. [39] studied the presence of hydroxylated metabolites of HBCD in three wildlife species and rats exposed to HBCD for 28 days. Four types of metabolites were found using LC–MS/MS, the monohydroxy metabolites of TBCDe, PBCDe, and HBCD and a dihydroxy-HBCD. The analysis of OH-PBDE metabolites by LC–MS seems interesting. However, these metabolites are poorly ionized by LC–ESI–MS, so they are not easily detected at low levels [40]. In 2007, Mas et al. [41] proposed the analysis of eight underivatized OH-PBDEs (OH-di- to OH-tetra-) by negative ion-spray ionization (ISP) –MS/MS. This method was shown to be efficient, robust, sensitive, and selective with LOQs at the high pg/g dry weight level.

14.3.2 Drugs of Abuse

Almost all the published methods to determine the drugs of abuse in water include a sample preparation based on either off-line SPE using Oasis HLB, Strata-X, Oasis MCX, or Strata-XC sorbents [42,43] or on-line SPE coupled directly to LC–MS [19,20]. Reversed-phase LC is the most used chromatographic technique for drugs of abuse [44], but recently, some methods were reported using hydrophilic interaction liquid chromatography (HILIC) [19,45]. Some studies have also been reported with a new particle column based on Fused-Core™ technology which has been developed to provide similar high speed and high efficiency as sub-2-μm particles but at half the back pressure. For example, Fontanals, Marcι, and Borrull [19] successfully used on-line SPE–HILIC–MS with a Fused-Core particle column to achieve a rapid and sensitive (low ng/l) analytical method for polar drugs in water, while Pedrouzo et al. [17] developed a method based on SPE–LC–MS/MS for the simultaneous analysis of six drugs and four metabolites in water using Ascentis Express C18. As already mentioned, UHPLC is being increasingly used in environmental analysis [7,8,42], because it offers advantages over conventional LC, such as improved separation efficiency and faster separations.

14.3.3 Hormones and Other Endocrine-Disrupting Compounds

The number of analytical methods described in the literature for the determination of endocrine-disrupting compounds (EDCs), such as natural and synthetic hormones (estrogens and progestogens), alkylphenolic compounds, and bisphenol A, has grown considerably. Because of the very low environmental levels (especially of hormones) and the complexity of some matrices, very efficient extraction–purification methods, in addition to selective and sensitive analytical techniques, are required. Due to its sensitivity and selectivity and because of its suitability for identification purposes in nontarget analysis, LC–MS/MS, preceded by SPE, is the method of choice for EDCs. For natural and synthetic hormones, which require especially sensitive detection, several on-line SPE–LC–MS/MS methods were developed [46–48], generally yielding LODs in the sub-ng/l range. Because of their low estrogenic potency, estrogen conjugates and progestogens have received comparatively less attention than estrogens. Liu et al. [49] used off-line SPE ultrasonic extraction and silica gel cartridge cleanup followed by rapid-resolution (RR) LC–MS/MS for the analysis of 28 steroids including 4 estrogens, 14 androgens, 5 progestagens, and 5 glucocorticoids in surface water, wastewater, and sludge samples. Several LC–MS/MS based methods were developed for the simultaneous analysis of EDCs belonging to different compound classes (hormones, nonylphenol, BPA, phthalates, etc.) in mixtures with pharmaceutical and other emerging contaminants, such as in the method for the simultaneous analysis of free and conjugated estrogens and antibiotics in runoff water and soil [50]; a method for the analysis of steroid hormones, pharmaceuticals and hormone-like personal care products (parabens, triclosan) in sewage sludge [6]; method for human pharmaceuticals and synthetic hormones in wastewater and river water [4,51].

14.3.4 Nanomaterials

In spite of the dynamic growth of manufacturing and use of nanomaterials (NMs), there are still very few analytical methods for their quantification in environmental matrices. Most quantitative procedures for NMs in environmental samples are devoted to carbon based NMs. For the quantification of fullerenes at low concentration, LC combined with MS [52], TOF MS, and TOF/TOF is mostly used [53]. To date, no measurements of the exposure or accumulation have been made in wild aquatic organisms, and few works have developed methods for the analysis of complex biological samples. Xia, Monteiro-Riviere, and Riviere [54] reported a trace analytical method for fullerenes from a sample containing a large amount of proteins. After the optimization of a liquid–liquid extraction LC method, a limit of detection of 0.34 μg/l was achieved. In another work, quantitative liquid–liquid extraction followed LC–MS was reported for the determination of fullerenes in water samples with a limit of detection of 0.4 μg/l [55]. The method was applied to determine the uptake of C60 by embryonic zebra fish. Recently, the same group presented a new analytical method for the analysis of aqueous fullerene C60 aggregates by asymmetric FFF with size determination by dynamic light scattering and quantification by LC–APPI–MS [56]. A method based on ultrasonic extraction followed by LC–MS/MS was developed for the quantification of fullerenes absorbed to suspended material in wastewater by Farré et al. [57], and this has given the first evidence of fullerenes in real environmental samples. In this case, the sensitivity was adequate (0.2–1 ng/l) for the analysis of real environmental samples. Recently, a group evaluated the occurrence of aerosol bound fullerenes in the Mediterranean Sea atmosphere [58].

14.3.5 Perfluorinated Compounds

Perfluorinated compounds (PFCs) constitute a large group of compounds characterized by a fully fluorinated hydrophobic linear carbon chain attached to one or more hydrophilic head groups. PFCs repel both water and oil and are therefore ideal chemicals for surface treatments. These compounds have been used for many industrial applications, including stain repellents (such as Teflon), textile, paints, waxes, polishes, electronics, adhesives, and food packaging [59].

In recent years a significant effort has been devoted to the detection of PFCs in environmental samples and biota, and several reviews have been published [60]. One of the major problems encountered in PFCs analysis is cross-contamination during the analytical process [61]. The major source of contamination of PFCs in laboratories is contact with laboratory materials made of or containing fluoropolymers, such as polytetrafluoroethylene or perfluoroalkoxy compounds [61]. On the other hand, different causes of losses have been identified associated with adsorption to sample containers, such as glass [62], or polymeric containers, such as polypropylene (PP), and high-density ethylene (HDPE) container surfaces. Biodegradation and biotransformations also should be prevented. Whereas good results were obtained for samples stored in a freezer or using combinations of solvents, like acetonitrile, and freezing [63] among others.

For the extraction of complex matrices, such as food, procedures based on ion-pair extraction using a tetrabutylammonium (TBA) hydroxide solution are widely employed [64,65]. However, this method has some disadvantages, such as (a) coextraction of lipids and other matrix constituents and (b) the wide variety of recoveries observed, which are related to the matrix effects mentioned previously. Liquid–solid extraction (LSE) is also applied to the analysis of biota and food samples [66]. During recent years, KOH digestion, to release covalently-bound fluoride ions followed by extraction using solid-phase extraction has been used. This method was initially reported by Yamashita et al. [67] and later applied in different studies [68]. For liquid samples, analysis protocols based on filtration followed by SPE are widely used.

For quantitative aspects, LC is the separation technique of choice. LC separation of PFCs has been carried out mainly with C18 and C8 columns. Taniyasu et al. [69] explored the chromatographic properties and separation of short-chain PFAs on RP C18 and ion-exchange columns. The results suggest that RP columns are not suitable for the analysis of short-chain PFAs, and ion-exchange columns are a suitable alternative, and have superior retention properties for more hydrophilic substances.

ESI operating in the negative ion mode has been the interface most widely used for the analysis of anionic PFCs. In addition, ESI has been optimized for the determination of neutral compounds, such as the sulfonamides PFOSA, Et-PFOSA, and t-Bu-PFOS. The use of atmospheric pressure photoionization was explored by Takino, Daishima, and Nakahara [70]. The authors found the main advantage of this technology to be the absence of matrix effects, but the limits of detection were considerably higher than those obtained by LC–ESI–MS/MS.

LC–MS/MS performed using triple quadrupole (QqQ) combined with multiple reaction monitoring (MRM) is one of the more widely applied detectors as well as one of the better-suited detectors for quantification of PFCs. Nowadays, the performance of ion trap (IT) and TOF also are considered suitable for trace quantification of PFCs. Berger and Haukas present a comparison between IT, QqQ, and time-of-flight (TOF) instruments [71]. Tandem mass spectrometry showed excellent specificity, as the matrix background is eliminated by the instrument. Applying TOF–MS gives an estimation of the amount of matrix left in the extract, which could impair the ionization performance, and the high mass resolution of the TOF–MS instrument offers excellent specificity for PFC identification after a crude sample injection.

14.3.6 Pharmaceuticals

The need to monitor pharmaceutical residues in the environment resulted in numerous analytical methods developed for their determination and the determination of their metabolites. Today, multiresidue analytical methods have become preferred tools for tracking down different therapeutic categories, and the pharmaceuticals more frequently included in such multiresidue methods are analgesics and anti-inflammatory drugs, antibiotics, lipid regulators, psychiatric drugs, and ß blockers. These drugs have very high consumption worldwide and are the most ubiquitous in both surface and wastewaters. SPE followed by LC coupled to tandem MS (QqQ) is the usual method of choice for quantitative determinations. Table 14.1 gives several examples of current methods used to simultaneously analyze pharmaceuticals belonging to different therapeutical classes. Furthermore, in the last few years, state-of-the-art analytical methodologies using hybrid MS detection systems, such as QqTOF, QqLIT, linear ion trap–Fourier transform–ion-cyclotron resonance (LIT–FT–ICR) and LTQ Orbitrap [3] have been applied to the analysis of pharmaceuticals in environmental and wastewaters. Schriks et al. [72] used LC–high resolution Orbitrap MS/MS to identify and quantify various glucocorticoids in wastewaters in the Netherlands. Figure 14.2 shows the high resolution MS spectra and low resolution product ion spectra for a selection of five glucocorticoids. Herrera-Rivera at al. [73] used an Orbitrap to study the influence of natural organic matter on the screening of pharmaceuticals in water, while in another study, an Orbitrap was used for the high-throughput identification of microbial transformation products of pharmaceuticals [74].

TABLE 14-1

Overview of Most Representative LC-MS Methods for Quantitative Determination of Pharmaceuticals in Aqueous and Solid Environmental Samples

FIGURE 14.2 High-resolution full scan MS spectra (A−E) and low resolution MS product ion spectra (A′−E′) for a selection of 5 glucocorticoid standards. Reprinted with permission from [72]. Copyright © 2010 American Chemical Society

14.3.7 Sunscreen Agents

Sunscreen agents, also known as UV filters, are used extensively in personal care products and also are present in a wide variety of industrial goods, such as textiles, paints, and plastics to prevent photodegradation of polymers and pigments [75]. However, recent concern has risen due to their potential for endocrine disruption and developmental toxicity [76,77].

A number of LC–MS/MS based methods have been developed for their trace analysis in environmental samples. For water analysis, LC–ESI–MS/MS is the technique of choice; however, in recent studies, UHPLC separation and APCI ionization has become increasingly popular. Pedrouzo et al. [78] developed a new UHPLC–MS/MS method using solventless stir-bar sorptive extraction to investigate four UV filters, dihydroxy methoxybenzophenone (DHMB), benzophenone-3 (BP-3), octocrylene (OC), and ethylhexyl dimethyl-aminobenzoate (OD-PABA) in surface water and wastewater. Detection limits of 2.5 ng/l and 10 ng/l, respectively, were achieved. Recently, Wick, Fink, and Ternes combined LC–ESI–MS/MS and LC–APCI–MS/MS after SPE extraction for the determination of five UV filters in wastewater and surface water [79]. Quantification limits achieved ranged from 0.5 to 5 ng/l and 2.5 to 50 ng/l in surface water and wastewater, respectively. An innovative method, more simple and rapid, based on the direct analysis of the surface of a polydimethylsiloxane-coated stir bar previously used to extract the UV filters from water was developed by Haunschmidt et al. [80]. With this direct analysis in real time (DART) –MS method, seven UV filters were determined in different environmental waters with detection limits below 40 ng/l in all cases.

Several methods have been developed for the analysis of sludge and sediment samples. For sewage sludge, PLE combining extraction and cleanup in a single step, followed by UHPLC–ESI–MS/MS was used by Nieto et al. [81] to measure four UV filters with limits of detection below 8 μg/kg dry weight. Using this method, OD-PABA and BP-3 were detected for the first time in sewage sludge. Gago-Ferrero, Díaz-Cruz, and Barcelo [82] employed a similar method to determine eight UV filters and degradation products in sewage sludge. The determination was fast and sensitive, affording limits of detection lower than 19 ng/g dry weight. Good recovery rates, especially given the high complexity of the sludge matrix (between 70% and 102% were afforded. Rodil, Schrader, and Moeder [83] described a method based on LC–APPI–MS/MS for the determination of 11 UV filters in sludge with limits of detection in the range 0.3–25 ng/g. With this method, UV filters were found at levels ranging from 1.4 to 2479 ng/g, and seven of them were detected for the first time. In sediments, existing data on UV filters is scarce. The extraction methods used were based on solid–liquid extraction of the freeze dried sediments with different organic solvents, and analyses were performed by gas chromatography–mass spectrometry, with separation times longer than 60 min and requiring a derivatization step for the most polar compounds. Based on LC, Gago-Ferrero, Díaz-Cruz, and Barcelo [84] created a fast, selective and sensitive multiresidue analytical method involving the concentration and purification in a single step by placing aluminum oxide as cleanup sorbent in the PLE extraction cell. PLE extraction and purification in connection with UHPLC enabled all compounds to be separated in less than 9 min and with a total chromatographic analysis time of 18 min. This method significantly decreased the overall time of analysis as compared to those of previously developed methods. Quantitative recoveries (>80%), satisfactory precision (RSD, 5–15%), and low limits of detection (0.5–15 ng/g dry weight) were achieved. By using this method, UV filters could be detected in 95% of the sediment samples analyzed. Results revealed a widespread presence of OC, reaching concentrations up to 2400 ng/g dry weight, the highest reported so far. OD-PABA and BP-3 were also frequently detected (60–65%) but at lower concentrations (4.4–27 ng/g dry weight).

14.4 Conclusions

The application of advanced tandem and hybrid LC–MS instruments in the field of environmental analysis has allowed the determination of a broader range of compounds and, thus, permitted more comprehensive assessment of environmental contaminants. However, one of the drawbacks of current analytical methods is that the majority of them focus on only parent target compounds and rarely include metabolites and transformation products, which sometimes can be more toxic and persistent than the original compounds. Moreover, identification of reaction pathways and identification of transformation products is of crucial importance in understanding the fate or organic contaminants in the environment. On the other hand, the high complexity of environmental samples sometimes requires the application of high resolution techniques to provide additional structure information needed for unequivocal identification of contaminants and confirmation of positive findings. The introduction of Orbitrap, TOF, QqTOF, and QqLIT instruments, which allow the simultaneous determination of both parent and transformation products within a single analytical run, overcomes this drawback and provides a higher degree of certainty in compound identification. In comparison to triple quadrupole mass spectrometers, which operate at unit resolution and generally in the SRM mode for specific target analytes, TOF, QqTOF, and Orbitrap mass spectrometers are capable of acquiring full-scan mass spectra at high resolution for all analytes without loss in sensitivity. Since these instruments have high resolution (at least 10,000 and higher) at full-width–half-maximum (fwhm) peak height, isotopic patterns are evident and chemical structures can be proposed for unknowns or confirmed for target analytes [3].

Therefore, a gradual shift from parent compound analysis to the analysis of metabolites and transformation product is expected. But the question is whether chemical analysis of specific compounds is sufficient to assess contaminants present in the environment. The main drawback of the conventional approach is target compound monitoring, which is often insufficient to assess the environmental relevance of emerging contaminants. The real challenge is to decide on the significance of the chemical data, and the discussion of the risks posed is still open. General screening for unknown substances is time consuming and expensive and is often shattered by problems, such as lack of standards and mass spectral libraries. Therefore, effect-related analysis, focused on relevant compounds, nowadays, seems to be more appropriate to assess and study environmental contamination problems.

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