Surface Water Matrices Research Articles

Direct contact membrane distillation for surface water treatment and phenolic compounds retention: From bench to pilot scale

Membrane distillation has been applied in water treatment for micropollutant retention, such as phenols. Direct contact membrane distillation (DCMD) is the most studied configuration at the bench scale. Translating lab-scale results to large-scale experiments requires attention. In general, by combining both experiment's results, optimal settings, and process conditions can be better determined. Thus, the DCMD scaling up for water treatment and phenols retention was evaluated. As expected, permeate flux reduced considerably from bench to pilot scale (15.8 ± 0.8–2.9 ± 0.1 kg m−2 h−1) due to the inflow energy limitations, membrane compaction, and temperature polarization. Increasing the permeate recovery (50–70 %) did not affect the permeate flux and the compound's retained in both systems. The pilot system was validated with different surface water matrices (14.2, 92.5, and 162 NTU), proving the DCMD robustness. In all operational conditions, the permeate reached the water quality guideline required for human consumption demonstrating the technology consistency and reliability. A preliminary economic analysis, considering three different scenarios (distributed system for communities, mobile system, and polishing for conventional WTP), showed the DCMD as a relatively competitive technology for the application in drinking water polishing (US$ 0.50–0.19/m3).

Efficient removal of sulfamethoxazole by biomass phosphorus-derived Cu3P/biochar catalyst combined with persulfate

Sulfamethoxazole (SMX) is ubiquitous in environments with concentrations ranging from nano-gram per liter to milli-gram per liter in practice, especially in water matrices (surface water and wastewater), posing a grave threat to ecosystems for its antibacterial and persistent characteristics. Efficient SMX removal is critical for water purification. Herein, the nano and micron Cu3P particles are synthesized on biochar utilizing phytic acid (PA) doped rice brans. PA facilitates the transformation of Cu-containing precursors to Cu3P on biochar, promoting catalytic performance. Under the conditions of 0.15 g/L catalyst (6PA-Cu11), 3.0 mM persulfate (PS), and pH 7.00, sulfamethoxazole (SMX) at a concentration of 0.25, 0.50, 1.00, and 10.00 mg/L can be completely removed within 30, 60, and 180 min, respectively. Moreover, the combination of Cu3P/biochar and persulfate exhibits preferable catalytic performances for SMX removal in sodium humate solution and surface water matrices, demonstrating the broad applicability of such a catalytic system for water purification. Sulfate radical (SO4−•) and hydroxy radical (•OH) play vital roles in the oxidation of SMX, with 1O2 assisting in. Except for cuprous ion (≡Cu+), partially charged copper ions (≡Cuδ+) and phosphorus ions (≡Pγ−) in Cu3P, owning the electron-donating ability, are found to participate in the activation of PS or the reduction of high-valent copper ions depending on density functional theory (DFT) calculations. Biochar carrier enhances the catalytic role of copper ions in Cu3P and facilitates the recovery of active sites by improving the desorption of the activation product (SO42−) from the Cu3P surface. This research promotes the practicability of the Cu3P/biochar catalyst in the advanced oxidation process for refractory organic pollutant removal and deepens the perception of its catalytic mechanisms.

Phytic acid-modulated iron phosphide/biochar catalyst activates persulfate for rapid sulfamethoxazole removal: Synergy between iron phosphides and biochar

The efficient activation of persulfate (PS) is essential for rapidly degrading refractory organic pollutants in water. Traditional metal-based catalysts are limited by defects such as the metal ion redox cycle and secondary pollution, resulting in insufficient catalytic performances. In this research, highly active micron-sized iron phosphides (FeP and Fe2P) are in-situ synthesized on biochar, and the primary crystal phase can be switched by adjusting the phytic acid (PA) amount. Under the conditions of 0.15 g/L catalyst, 0.5 mM PS, and pH 7, sulfamethoxazole (SMX) at concentrations of 0.25, 0.50, 1.00, and 10.00 mg/L can be completely oxidized within 3, 5, 15, and 180 min, respectively. The leached ferric ion amount is below 0.020 mg/L. Meanwhile, ideal SMX abatements are achieved in sodium humate solution and surface water matrices, demonstrating the potential of this catalytic system for drinking water and wastewater treatment. Moreover, SO4-•, •OH, and 1O2 are crucial reactive oxygen species for SMX removal. Based on density functional theory (DFT) calculations, it is found that the partially charged Fe ion (≡Feδ+) is the pivotal site for PS activation and ≡Fe2+ regeneration. FeP and Fe2P are typically semi-metallic. Biochar can enhance the catalytic efficacies of FeP and Fe2P by shifting d-band centers (spin up and down) towards fermi level and reducing band gaps (spin down). Besides, biochar may donate electrons to iron phosphides when activating PS. The enhancement of FeP by biochar is more significant, which is why FeP/biochar is superior to Fe2P/biochar in PS activation.

Environmental risk assessment as a tool to identify potential hotspots of bacteria resistance worldwide

Pharmaceutical usage has led to the widespread detection of these compounds in aquatic ecosystems worldwide, raising concerns about the selective pressure they can exert on microbial communities. To aid in tackling this global emergency, we undertook an initial step in identifying potential hotspots of bacterial resistance arising from the occurrence of antibiotics in the environment. This was conducted by performing a risk assessment based on the measured environmental concentrations of selected antibiotics, acquired from an international pharmaceutical database, and the respective no-effect concentrations for bacterial resistance of such antibiotics. We identified untreated industrial and hospital sewage as the aquatic matrices of most concern. Regarding treated effluent from wastewater treatment plants, the antibiotic ciprofloxacin and Tunisia exhibit a high-risk quotient. For surface water matrices (rivers and streams), both ciprofloxacin and amoxicillin warrant attention and the countries with the highest risk medians were India, South Africa, and the United States of America. Our study provides an initial basis for highlighting the antibiotics, countries, and aquatic matrices that warrant more attention regarding bacterial resistance. This approach can be applied at national or regional scales for more detailed environmental evaluation and decision-making. Nonetheless, we encourage further investigations to confirm the occurrence of antibiotic-resistant bacteria and antibiotic-resistance genes in the potential hotspots identified in this study.

Combination of Zinc Oxide Photocatalysis with Membrane Filtration for Surface Water Disinfection.

Increase water usage has led to its deterioration. Pollutants are easily found in the aquatic environment and treatment techniques must keep improving to meet the current needs and future demands. Membranes are attractive for water treatment, but limitations like fouling and the highly concentrate produced affect their performance. Combining membrane filtration with photocatalysis provides the opportunity to integrate a self-cleaning step during membrane filtration. In this work, we studied two simple and efficient approaches to combine membrane filtration with zinc oxide nanoparticles (using the catalyst in suspension and immobilized) activated by light emitting diodes (LED) emitting light at 365 nm. Both systems were used to test the disinfection efficiency in real surface water, compared in terms of catalyst concentration in the permeate stream (below the limit of detection) and its recovery after filtration (higher that 74%). The system's capability to retain and inactivate target bacteria (total coliforms and E. coli) in the retentate stream was tested with samples of real surface water. The results obtained show that both configurations led to an improved performance in comparison to the membrane treatment alone with a higher retention of the bacteria (not detected in the permeate samples) and higher treatment of the retentate. For the modified membranes, different catalyst concentrations and thermal treatments were tested. The performance of all the processes was evaluated in terms of the level of treatment achieved and the permeate flux. All the modified membranes showed an efficient retention of the target bacteria from surface water, with higher performances than the unmodified membrane (96.2% for total coliforms and 94.9% for E. coli). Remarkable retention and treatment of the retentate was achieved using a membrane modified with a catalyst load of 125 mg subject during two hours to a thermal treatment of 300 °C. This modification has a performance comparable to the system with the same catalyst load in suspension. During operation, the permeate flux reduction is lower with the modified membranes which could lead to longer operation times without the need of further cleaning or replacement. The combined system, ceramic membranes modified with zinc oxide and UV-A LEDs proved to be effective to retain and disinfect water quality indicator bacteria present in real surface water matrices.

Hybrid nanomaterial-based indirect electrochemical sensing of glyphosate in surface water: a promising approach for environmental monitoring.

Glyphosate (GLY), a widely utilized pesticide, poses a significant threat to human health even at minute concentrations. In this study, we propose an innovative electrochemical sensor for the indirect detection of GLY in surface water samples. The sensor incorporates a nanohybrid material composed of multi-layer graphene decorated with gold nanoparticles (AuNPs), synthesized in a single-step electrochemical process. To ensure portability and on-site measurements, the sensor is developed on a screen-printed electrode, chosen for its integration and miniaturization capabilities. The proposed sensor demonstrates remarkable sensitivity and selectivity for GLY detection in surface water samples, with an exceptional limit of detection (LOD) of 0.03 parts per billion (ppb) in both buffer and surface water matrices. Moreover, it exhibits a remarkably high sensitivity of 0.15 μA ppb-1. This electrochemical sensor offers a promising approach for accurate GLY monitoring, addressing the urgent need for reliable pesticide detection in environmental samples. The proposed sensor showed high selectivity towards GLY, when analysed in the presence of other pesticides such as phosmet, chlorpyrifos and glufosinate-ammonium. The recovery percentages of GLY from spiked surface water samples were between 93.8 and 98.9%. The study's broader implications extend to revolutionizing the way environmental chemistry addresses pesticide contamination, water quality assessment, and sustainable management of environmental pollutants. By pushing the boundaries of detection capabilities and offering practical solutions, this research contributes to the advancement of knowledge and practices that are essential for preserving and protecting our environment.

Photo-Fenton Degradation of Ciprofloxacin by Novel Graphene Quantum Dots/α-FeOOH Nanocomposites for the Production of Safe Drinking Water from Surface Water

In the current work, novel graphene quantum dots (GQDs)-doped goethite (α-FeOOH) nanocomposites (GQDs/α-FeOOH) were prepared by following a feasible hydrolysis method and applied for ciprofloxacin (CIP) removal. Results showed that the CIP degradation efficiency was significant (93.73%, 0.0566 min−1) in the GQDs/α-FeOOH + H2O2 + Vis system using much lower amounts of H2O2 (0.50 mM), which is 3.9 times the α-FeOOH + H2O2 + Vis system. It was found that •OH, O2•−, and 1O2 were mainly responsible for CIP degradation in the GQDs/α-FeOOH photo-Fenton system. GQDs/α-FeOOH demonstrated broad-spectrum UV–vis-IR responsiveness in the degradation of ciprofloxacin as a function of the doping of GQDs. Additionally, GQDs/α-FeOOH showed outstanding durability (recyclability up to 3 cycles with a lower iron leaking amount, 0.020 mg L−1), a broad range of application pH, and a pretty acceptable catalytic efficacy in a variety of surface water matrices. Overall, GQDs/α-FeOOH have been shown to be an effective photocatalyst for the remediation of emerging contaminants via the workable exploitation of solar energy.

High H2O2 selectivity and enhanced Fe2+ regeneration toward an effective electro-Fenton process based on a self-doped porous biochar cathode

Cathode materials with high catalytic activity for H2O2 production and Fe2+ regeneration are essential to an efficient electro-Fenton process. Herein, we demonstrate a facile self-sacrificial template route to synthesize heteroatom-doped porous biochar. Owing to the created hierarchical porous structure and active defects, more generated oxygen functional groups (COOH/C–O–C) and modulated nitrogen dopants, the biochar cathode exhibits enhanced electrocatalytic activity. It achieves a high H2O2 selectivity (92%), facilitated Fe2+ regeneration, and an efficient H2O2 activation rate (82%). Various organic contaminants, including endocrine-disrupting chemicals, phenols, and antibiotics, can be effectively degraded with removal efficiencies of 98–100% within 15 min. The mineralization efficiencies achieve 83–100% with energy consumption of 0.87–1.07 kWh m−3. Moreover, the electro-Fenton system exhibits good stability and versatile applicability for organic pollutants remediation in different surface water matrices. This study offers valuable insights into the preparation of cost-effective cathode materials for an efficient electro-Fenton process.

Identifying water quality and environmental factors that influence indicator and pathogen decay in natural surface waters

Biphasic decay has been observed for indicators and pathogens in bench-scale and in-situ water experiments for decades, however, first-order decay kinetics continue to be applied to persistence data because of their simplicity and ease of application. Model uncertainty introduced by broadly applying first-order decay kinetics to persistence data may lead to erroneous decision making in the fields of water management and protection. As surface waters are exposed to highly variable environmental and water quality factors that influence microbial and viral persistence, it is expected that first-order decay kinetics are not representative of most of the persistence literature for indicators and pathogens in surface water matrices. This review compiled the methods and results of 61 studies that conducted experiments evaluating the persistence of fecal indicator bacteria (FIB), bacteriophages, pathogenic bacteria, viruses, and protozoa in natural surface water matrices. The goals of this review were trifold: (1) collate studies in the literature with data available for future persistence modeling, (2) present the current state of knowledge with regards to the environmental and water quality factors affecting persistence in natural surface waters, and (3) identify recurrent evidence for interactions between the frequently studied factors to inform future factor analyses. Comparing the methods and results across the 61 studies suggest potential interactions between sunlight and water type; sunlight and method of detection; predation and water type; predation and temperature; and water type and method of detection. The majority of the identified literature evaluated FIB or bacteria persistence; future experiments are needed that focus on protozoa, brackish or marine water types, and molecular-based methods of detection.

Towards harmonization of water quality management: A comparison of chemical drinking water and surface water quality standards around the globe

Water quality standards (WQS) set the legal definition for safe and desirable water. WQS impose regulatory concentration limits to act as a jurisdiction-specific legislative risk-management tool. Despite its importance in shaping a universal definition of safe, clean water, little information exists with respect to (dis)similarity of chemical WQS worldwide. Therefore, this paper compares chemical WQS for drinking and surface water matrices in eight jurisdictions representing a global geographic distribution: Australia, Brazil, Canada, China, the European Union, the region of Flanders in Belgium, the United States of America, and South Africa. The World Health Organization's list is used as a reference for drinking water standards. Sørensen–Dice indices (SDI) showed little qualitative similarity in the compounds that are regulated in drinking water (median SDI = 40%) and surface water (median SDI = 33%), indicating that the heterogeneity within a matrix is substantial at the level of the standard. Quantitative similarity for matching standards was higher than the qualitative per Kendall correlation (median = 0.73 and 0.58 for drinking water and surface water respectively), yet variance observed within standards remained inexplicably high for organic compounds. Variations in WQS were more pronounced for organic compounds. Most differences cannot be easily explained from a toxicological or risk-based point-of-view. Historical development, ease of measurement, and (toxicological) knowledge gaps on the risk of a vast number of organic compounds are theorized to be the drivers. Therefore, this study argues for a more tailored, risk-based approach in which standards incorporated into water safety plans are dynamically set for compounds that are persistent and could pose a risk for human health and/or aquatic ecosystems. Global variations in WQS should therefore not necessarily be avoided but rather globally harmonized with enough flexibility to ensure a global, up-to-date definition of safe and desirable water everywhere.

BDD electrochemical oxidation of neonicotinoid pesticides in natural surface waters. Operational, kinetic and energetic aspects

Neonicotinoids pesticides were introduced to the market in the 1990s to control various pests. Its accumulation in the environment supposes a severe problem that can affect human health. This study investigates the electrochemical degradation of four common neonicotinoid pesticides; thiamethoxam (TMX), imidacloprid (ICP), acetamiprid (ACP) and thiacloprid (TCP), in different natural surface waters by a boron-doped diamond anode (BDD). The most influencing variable was the current density (j), and to a lesser extent, the supporting electrolyte concentration (Ce). In optimal conditions (j = 34.14 mA cm−2 and Ce = 10.00 mM, using Na2SO4 as electrolyte) pesticide removals for TMX, ICP, ACP and TCP were 97.2, 96.9, 87.8 and 98.2 %, respectively. The obtained results with different support electrolytes (Na2SO4, NaCl, NaNO3 and HK2PO4) suggest that sulphate electrolyte was the optimum for TMX, ICP and ACP. However, for TCP, a total removal was achieved in less than 10 min using NaCl. It was also verified that the initial pH of the solution did not significantly influence the process in the range 3–9. All these results were rationalized in this paper. Finally, to evaluate the matrix influence, some experiments were carried out in different natural surface water matrices (river, reservoir and two different WWTP effluents). The factors influencing the process were the conductivity of the solution and the organic matter content. It was noticeable that the specific energy consumption (SEC) reduced by approximately 15 % for river water and WWTP effluent. High mineralization rates were obtained for all water matrices, with TOC removals ranging between 60 and 80 %.

Biotransformation of pregabalin in surface water matrices and the occurrence of transformation products in the aquatic environment - comparison to the structurally related gabapentin

The biodegradability of the anticonvulsant pregabalin (PGB) was studied in laboratory incubation experiments in contact with water/sediment systems under different redox conditions. PGB was degraded by biological processes under aerobic conditions reaching half-lives of 8 to 10 d, while inactivated and anaerobic control experiments revealed no significant decrease of PGB concentrations. Within experiments spiked with elevated PGB concentrations, 12 TPs were formed and tentative chemical structures could be proposed by accurate masses and fragmentation pathways detected via measurements with high resolution mass spectrometry (LC-QToF-MS). Four of the proposed TPs were finally confirmed either by authentic reference standards (PGB-Lactam, ISA, TP 157-A (II)) or a self-synthesized standard (NA-PGB). PGB-Lactam was identified as the quantitatively most relevant TP formed via intramolecular cyclization under aerobic conditions, reaching up to 33% of the initial PGB concentration. Incubation experiments spiked with PGB-Lactam revealed three times higher half-lives compared to the parent compound, indicating that PGB-Lactam is more stable than PGB. A comparison with results gained from water/sediment incubation experiments with the structurally related compound gabapentin (GBP) revealed, that the transformation behaviour can be mainly extrapolated to PGB. Most of the observed transformation reactions found for PGB were comparable to the ones found for GBP. The TPs PGB-Lactam and NA-PGB as well as three GBP TPs (GBP-Lactam, NA-GBP and CCHA) have been detected in German wastewater treatment plants (WWTPs) effluents and the river Rhine including some of its tributaries such as Main, Neckar, Moselle and Aare. Moreover, GBP and PGB as well as some of their TPs were detected in German bank filtrates and finished drinking waters up to 260 ng L-1. For that reason these compounds should be monitored in drinking water in the future.

Matrix Effects on the Degradation of Gemfibrozil, Hydrochlorothiazide, and Naproxen by Heterogeneous Photocatalysis

The degradation of a pharmaceutical mixture (gemfibrozil, hydrochlorothiazide and naproxen) by TiO2/UV-A in different aqueous matrices was evaluated. The matrix components affected the operational conditions, rate constants, and removal efficiency of the pharmaceuticals, as well as toxicity. For sewage treatment plant effluent, a TiO2 concentration three-fold higher (450 mg L−1) and an irradiation time 1.5-3 times longer were required to reach the same efficiency of degradation as the pharmaceuticals in deionized water and surface water matrices. An improvement in the rate constants and the removal efficiency of the pharmaceuticals was achieved by adding 6 mg L−1 of H2O2 and 150 mg L−1 of TiO2 in deionized water and surface water, but not in the sewage treatment plant effluent, due to the coupling of 450 mg L−1 of TiO2 and 50-200 mg L−1 of H2O2. Overall, TiO2/UV-A efficiently degraded all compounds, but an additional step is needed for the removal of residual toxicity.

Development of complementary CE-MS methods for speciation analysis of pyrithione-based antifouling agents.

In the recent decade, metal pyrithione complexes have become important biocides for antifouling purposes in shipping. The analysis of metal pyrithione complexes and their degradation products/species in environmental samples is challenging because they exhibit fast UV degradation, transmetalation, and ligand substitution and are known to be prone to spontaneous species transformation within a chromatographic system. The environmental properties of the pyrithione species, e.g., toxicity to target and non-target organisms, are differing strongly, and it is therefore inevitable to identify as well as quantify all species separately. To cope with the separation of metal pyrithione species with minimum species transformation during analysis, a capillary electrophoresis (CE)-based method was developed. The hyphenation of CE with selective electrospray ionization- and inductively coupled plasma-mass spectrometry (ESI-, ICP-MS) provided complementary molecular and elemental information for the identification and quantification of pyrithione species. To study speciation of pyrithiones, a leaching experiment of several commercial antifouling paints containing zinc pyrithione in ultrapure and river water was conducted. Only the two species pyrithione (HPT) and dipyrithione ((PT)2) were found in the leaching media, in concentrations between 0.086 and 2.4μM (HPT) and between 0.062 and 0.59μM ((PT)2), depending on the paint and leaching medium. The limits of detection were 20nM (HPT) and 10nM ((PT)2). The results show that complementary CE-MS is a suitable tool for mechanistical studies concerning species transformation (e.g., degradation) and the identification of target species of metal pyrithione complexes in real surface water matrices, laying the ground for future environmental studies. Graphical abstract Hyphenation of CE with ESI- and ICP-MS provided complementary molecular and elemental information. Metal pyrithione species released from commercial antifouling paints could be identified and quantified in ultrapure and river water matrices.

Biotransformation of gabapentin in surface water matrices under different redox conditions and the occurrence of one major TP in the aquatic environment

Laboratory-scale incubation experiments in water/sediment systems were conducted to test the transformation behavior of the anticonvulsant gabapentin (GBP) under different environmental conditions (aerobic, anaerobic, with abiotic controls). GBP was transformed by biological processes as it was eliminated quickly under aerobic conditions (dissipation time 50% of initial concentration (DT50): 2–7 days) whereas no decrease was observed under anaerobic conditions. Measurements via high resolution mass spectrometry (LC-Orbitrap-MS) revealed eight biological transformation products (TPs). Three of them were identified with reference standards (GBP-Lactam, TP186, TP213), while for the other five TPs tentative structures were proposed from information by MS2/MS3 experiments. Furthermore, the quantitatively most relevant TP GBP-Lactam was formed via intramolecular amidation (up to 18% of initial GBP concentration). Incubation experiments with GBP-Lactam revealed a higher stability against biotic degradation (DT50: 12 days) in contrast to GBP, while it was stable under anaerobic and abiotic conditions. Besides GBP, GBP-Lactam was detected in surface water in the μg L−1 range. Finally, GBP and GBP-Lactam were found in potable water with concentrations up to 0.64 and 0.07 μg L−1, respectively. According to the elevated environmental persistence of GBP-Lactam compared to GBP and its presumed enhanced toxicity, we recommend to involve GBP-Lactam into monitoring programs.

Elucidating the Stimulatory and Inhibitory Effects of Dissolved Organic Matter from Poultry Litter on Photodegradation of Antibiotics.

This study examined the photolytic fate of the chlortetracycline (CTC), ciprofloxacin (CIP), roxarsone (ROX), and sulfamethoxazole (SMX) antibiotics in agriculturally relevant matrices. The observed photodegradation kinetics for antibiotics in solutions containing dissolved organic matter (DOM) from three poultry litter extracts was modeled to identify contributions from direct and indirect photolysis. Suwannee River natural organic matter (SRN) was used as a surrogate DOM standard. Poultry litter-derived DOM generated lower concentrations of reactive species compared to SRN. Direct photolysis was the dominant transformation mechanism for CIP, whereas CTC, ROX, and SMX were sensitized by 3DOM* and 1O2. The impacts of agricultural DOM on photodegradation of antibiotics were identified in terms of pseudo-first-order rate constants for formation of reactive species and second-order rate constants for reaction of reactive species with DOM. Solutions containing poultry litter-derived DOM generated similar levels of 3DOM* and 1O2, enhancing degradation of CTC, ROX, and SMX. The reactivity of SMX was markedly different in solutions containing poultry litter DOM compared to solutions with SRN, indicating that the photolytic fate of select antibiotics varies for agricultural and surface water matrices. As the majority of antibiotics are consumed by animals, these findings provide new insight into agriculturally relevant transformation mechanisms and kinetics.

Determination of phenol compounds in surface water matrices by bar adsorptive microextraction-high performance liquid chromatography-diode array detection.

Bar adsorptive microextraction combined with liquid desorption followed by high performance liquid chromatography with diode array detection (BAµE-LD/HPLC-DAD) is proposed for the determination of trace levels of five phenol compounds (3-nitrophenol, 4-nitrophenol, bisphenol-A, 4-n-octylphenol and 4-n-nonylphenol) in surface water matrices. By using a polystyrene-divinylbenzene copolymer (PS-DVB) sorbent phase, high selectivity and efficiency is achieved even against polydimethylsiloxane through stir bar sorptive extraction. Assays performed by BAµE(PS-DVB)-LD/HPLC-DAD on 25 mL water samples spiked at the 10.0 µg/L levels yielded recoveries over 88.0% ± 5.7% for all five analytes, under optimized experimental conditions. The analytical performance showed good precision (RSD < 15%), detection limits of 0.25 µg/L and linear dynamic ranges (1.0–25.0 μg/L) with determination coefficient higher than 0.9904. By using the standard addition method, the application of the present method to surface water matrices allowed very good performances at the trace level. The proposed methodology proved to be a suitable alternative to monitor phenol compounds in surface water matrices, showing to be easy to implement, reliable, sensitive and requiring a low sample volume.

Identification of organic xenobiotics in urban aquatic environments using time-of-flight mass spectrometry

Qualitative non-target and post-target analysis methods using gas chromatography–time-of-flight mass spectrometry were applied for analysing neutral and acidic organic xenobiotics in urban and suburban water samples. Ten water samples representing wastewater, stormwater and surface water matrices were collected and concentrated using solid phase extraction. Compound identification was performed using a spectral deconvolution program, accurate mass measurements and comparisons with library spectra. The non-target and post-target analyses identified 36 and 18 compounds, respectively. The identification of 10 compounds was afterwards confirmed with standard compounds. Organophosphate esters were the most abundant compound group detected. The combination of non-target and post-target analyses proved a useful tool in the tentative identification of xenobiotics in water samples. Post-target analysis can complement non-target analysis results at low analyte concentrations. Results showed that several organic xenobiotics originate in urban areas and accumulate in the environment. The wastewater sample produced the highest number of identified compounds, but most of these compounds were also found in stormwater samples from the city centre. Nearly all the compounds present in wastewater were additionally detected in the surface water sample taken 3km downstream from the wastewater effluent discharge point. Only a few xenobiotics were otherwise detected in the surface water samples.

Development of a quantitative high-performance thin-layer chromatographic method for sucralose in sewage effluent, surface water, and drinking water

Sucralose, a persistent chlorinated substance used as sweetener, can already be found in waste water, and various countries focused on the release of sucralose into the aquatic environment. A quantitative high-performance thin-layer chromatography (HPTLC) method, which is orthogonal to existing methods, was developed to analyze sucralose in water. After sample preparation, separation of up to 17 samples was performed in parallel on a HPTLC plate silica gel 60 F 254 with a mixture of isopropyl acetate, methanol and water (15:3:1, v/v/v) within 15 min. Due to the weak native UV absorption of sucralose (≤200 nm), various post-chromatographic derivatization reactions were compared to selectively detect sucralose in effluent and surface water matrices. Thereby p-aminobenzoic acid reagent was discovered as a new derivatization reagent for sucralose. Compared to the latter and to β-naphthol, derivatization with aniline diphenylamine o-phosphoric acid reagent was slightly preferred and densitometry was performed by absorbance measurement at 400 nm. The limit of quantification (LOQ) of sucralose in drinking and surface water was calculated to be 100 ng/L for a given recovery rate of 80% and the extraction of a 0.5 L water sample. The sucralose content determined in four water samples obtained during an interlaboratory trial in 2008 was in good agreement to the mean laboratory values of that trial. According to the t-test, which compares the results with the target value, the means obtained by HPTLC were not significantly different from the respective means of six laboratories, analyzed by HPLC–MS/MS or HPLC–TOF-MS with the use of mostly isotopically labeled standards. The good accuracy and high sample throughput capacity proved HPTLC as a well suited method regarding quantification of sucralose in various aqueous matrices.

Validation of an enzyme-linked immunosorbent assay (ELISA) for the determination of 4-nonylphenol and octylphenol in surface water samples by LC-ESI-MS

4-Nonylphenol (NP) and octylphenol (OP) were measured by direct ELISA in both laboratory-fortified and surface water samples collected monthly from 10 rivers. In this procedure, samples were concentrated by solid phase extraction (SPE) using Lichrolut RP-18 sorbent with good recoveries obtained for both LC–MS and ELISA, giving a low level of detection (LOD) at the range of low μg L −1 and good reproducibility. Analysis of 40 surface water samples demonstrated that the ELISA may be a useful screening tool for the determination of the alkylphenols in surface water matrices. The concentration of NP and OP in surface waters ranged from 0.11 to 6.58 μg L −1. A good correlation of results obtained by ELISA and LC–MS within the concentration range of 0.08–6.86 μg L −1 was found in the river samples [ R 2 = 0.924, n = 39]. The influence of various factors on assay determination was also discussed.