During recent years matrix effects in liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) have quickly become a major concern in food analysis. The phenomenon of ion suppression can ...lead to errors in the quantification of the analytes of interest, as well as can affect detection capability, precision, and accuracy of the method. Sample dilution is an easy and effective method to reduce interfering compounds, and so, to diminish matrix effects. In this work, matrix effects of 53 pesticides in three different matrices (orange, tomato and leek) were evaluated. Several dilutions of the matrix were tested in order to study the evolution of signal suppression. Dilution of the extracts led to a reduction of the signal suppression in most of the cases. A dilution factor of 15 demonstrated to be enough to eliminate most of the matrix effects, opening the possibility to perform quantification with solvent based standards in the majority of the cases. In those cases where signal suppression could not be reduced, a possible solution would be to use stable isotope-labelled internal standards for quantification of the problematic pesticides.
The goal of this paper was to develop a modified photo-Fenton treatment able to degrade micro pollutants in municipal wastewater treatment plant (MWTP) effluents at a neutral pH with minimal iron and ...H2O2 concentrations. Complexation of Fe by ethylenediamine-N,N′-disuccinic acid (EDDS) leads to stabilization and solubilization of Fe at natural pH. Photo-Fenton experiments were performed in a pilot compound parabolic collector (CPC) solar plant. Samples were treated with solid phase extraction (SPE) and analyzed by HPLC-Qtrap-MS. The rapid degradation of contaminants within the first minutes of illumination and the low detrimental impact on degradation of bicarbonates present in the water suggested that radical species other than HO• are responsible for the efficiency of such photo-Fenton process. Disinfection of MWTP effluents by the same process showed promising results, although disinfection was not complete.
For the first time, the fungicide thiabendazole (TBZ) and its transformation products (TPs) were monitored under outdoor conditions, using natural sunlight (NSL) as a photon source, and the Magnetic ...Fraction of a low-grade titanium ore (MFTO) as an iron catalyst, in a raceway pond reactor. The TBZ degradation (TBZ
D
) was performed by two systems: solar photo-Fenton-like (MFTO-H
2
O
2
-NSL) and solar photo Fe/NaOCl (MFTO-NaOCl-NSL), both treatments were carried out using distilled water spiked with 1 mg/L TBZ under natural sunlight. The TPs were determined by a highly sensitive method based on liquid chromatography (LC) coupled to hybrid quadrupole time-of-flight mass spectrometry (QTOF-MS). The TBZ
D
results of four TPs were detected throughout the MFTO-NaOCl-NSL operation, and only two of them remained after t = 75 min. While, twelve TPs were formed during the TBZ
D
in the MFTO-H
2
O
2
-NSL system, and all reached stable concentrations after t = 180 min. That might be related with a faster degradation when NaOCl was used as an oxidant instead of H
2
O
2
. Thus, 80% of TBZ
D
was achieved at t = 40 and 240 min by the MFTO-NaOCl-NSL and MFTO-H
2
O
2
-NSL systems, respectively. Consequently, the pseudo-first-order kinetic constant of MFTO-NaOCl-NSL (0.059 min
−1
) was almost tenfold higher than the value obtained by MFTO-H
2
O
2
-NSL (0.006 min
−1
). The results obtained emphasize that the use of NaOCl as an alternative oxidant to H
2
O
2
, not only improves the reaction kinetics but also reduces the number of TPs at the end of the degradation process.
The sunlight/H2O2 process has recently been considered as a sustainable alternative option compared to other solar driven advanced oxidation processes (AOPs) in advanced treatment of municipal ...wastewater (WW) to be reused for crop irrigation. Accordingly, in this study sunlight/H2O2 was used as disinfection/oxidation treatment for urban WW treatment plant effluent in a compound parabolic collector photoreactor to assess subsequent cross-contamination of lettuce and soil by contaminants of emerging concern (CECs) (determined by QuEChERS extraction and LC-QqLIT-MS/MS analysis) and antibiotic resistant (AR) bacteria after irrigation with treated WW. Three CECs (carbamazepine (CBZ), flumequine (FLU), and thiabendazole (TBZ) at 100 μg L–1) and two AR bacterial strains (E. coli and E. faecalis, at 105 CFU mL–1) were spiked in real WW. A detection limit (DL) of 2 CFU mL–1 was reached after 120 min of solar exposure for AR E. coli, while AR E. faecalis was more resistant to the disinfection process (240 min to reach DL). CBZ and TBZ were poorly removed after 90 min (12% and 50%, respectively) compared to FLU (94%). Lettuce was irrigated with treated WW for 5 weeks. CBZ and TBZ were accumulated in soil up to 472 ng g–1 and 256 ng g–1 and up-taken by lettuce up to 109 and 18 ng g–1, respectively, when 90 min treated WW was used for irrigation; whereas no bacteria contamination was observed when the bacterial density in treated WW was below the DL. A proper treatment time (>90 min) should be guaranteed in order to avoid the transfer of pathogens from disinfected WW to irrigated crops and soil.
The photochemical transformation of sulfamethoxazole (SMX) was investigated in different water matrices: distilled water (DW), distilled water
+
nitrate (10 and 20
mg
L
−1) and seawater (SW) to ...evaluate its persistence, toxicity and degradation pathway. A solar simulator Suntest CPS+ was used for the irradiation experiments. Identification of transformation products was performed in DW by liquid chromatography-time of flight-mass spectrometry (LC–TOF–MS). Acute toxicity of irradiated solutions was monitored by
Vibrio fischeri and
Daphnia magna bioassays in DW. Differences in the degradation rates were observed between DW and SW, being slower in SW. Presence of nitrate (indirect photolysis) in distilled water did not affect SMX degradation rate. No dissolved organic carbon (DOC) removal was observed in any case, thus indicating the formation of abundant transformation products (TPs). Analysis by LC–TOF–MS allowed the identification of up to nine transformation products during photolysis in DW. Only three of them had been previously reported in the literature, detected with other techniques. The cleavage of the sulfonamide bond and the photoisomerization by rearrangement of the isoxazole ring represent the main pathways, at the time that generate the most abundant and persistent intermediates. The acute toxicity of SMX solution varied according to test organisms.
Daphnia magna was the most sensitive showing an increase from 60% to 100% immobilization after 30
h of irradiation when depletion of SMX was achieved, thus indicating the higher toxicity of the phototransformation products generated.
The use of reclaimed wastewater (RWW) for the irrigation of crops may result in the continuous exposure of the agricultural environment to antibiotics, antibiotic resistant bacteria (ARB) and ...antibiotic resistance genes (ARGs). In recent years, certain evidence indicate that antibiotics and resistance genes may become disseminated in agricultural soils as a result of the amendment with manure and biosolids and irrigation with RWW. Antibiotic residues and other contaminants may undergo sorption/desorption and transformation processes (both biotic and abiotic), and have the potential to affect the soil microbiota. Antibiotics found in the soil pore water (bioavailable fraction) as a result of RWW irrigation may be taken up by crop plants, bioaccumulate within plant tissues and subsequently enter the food webs; potentially resulting in detrimental public health implications. It can be also hypothesized that ARGs can spread among soil and plant-associated bacteria, a fact that may have serious human health implications. The majority of studies dealing with these environmental and social challenges related with the use of RWW for irrigation were conducted under laboratory or using, somehow, controlled conditions. This critical review discusses the state of the art on the fate of antibiotics, ARB and ARGs in agricultural environment where RWW is applied for irrigation. The implications associated with the uptake of antibiotics by plants (uptake mechanisms) and the potential risks to public health are highlighted. Additionally, knowledge gaps as well as challenges and opportunities are addressed, with the aim of boosting future research towards an enhanced understanding of the fate and implications of these contaminants of emerging concern in the agricultural environment. These are key issues in a world where the increasing water scarcity and the continuous appeal of circular economy demand answers for a long-term safe use of RWW for irrigation.
•The fate of antibiotics, ARB&ARGs in reclaimed WW-irrigated sites is discussed.•Antibiotic may undergo sorption/desorption and transformation processes in soil.•Antibiotics may be taken up and bioaccumulated within reclaimed WW-irrigated plants.•ARGs spread in reclaimed WW-irrigated sites may pose serious human health effects.•Antibiotics may exert phytotoxic effects to reclaimed WW-irrigated plants.
In this work, the activated persulfate oxidation of ciprofloxacin (CIP) using a low-grade titanium ore under sunlight or simulated sunlight were conducted to analyze the CIP degradation efficiency ...and to identify the transformation products (TPs) generated during oxidation under both types of irradiation sources by using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). All advance oxidation process experiments were performed in a 2700-mL raceway reactor at a pH value of ~ 6.5 and an initial CIP concentration of 1 mg/L, during 90 min of reaction time. The control experiments carried out under simulated sunlight achieved a 97.7 ± 0.6% degradation efficiency, using 385 W/m
2
of irradiation with an average temperature increase of 11.7 ± 0.6 °C. While, the experiments under sunlight reached a 91.2 ± 1.3% degradation efficiency, under an average irradiation value of 19.2 ± 0.3 W/m
2
in October–November 2019 at hours between 11:00 am and 3:00 pm with an average temperature increase of 1.4 ± 0.8 °C. Mass spectrometry results indicated that 14 of the 108 possible TPs reported in the literature were detected. The calculated exact mass, measured accurate mass, and its characteristic diagnostic fragment ions were listed, and two new TPs were tentative identified. The TP generation analysis showed that some specific compounds were detected in different time intervals with kinetic variations depending on the irradiation used. Consequently, two CIP degradation pathways were proposed, since the type of irradiation determines the CIP degradation mechanism.
Graphical abstract
In this work, the photocatalytic degradation of the antibiotic sulfamethoxazole (SMX) by solar photo-Fenton at pilot plant scale was evaluated in distilled water (DW) and in seawater (SW). ...Degradation and mineralization of SMX were strongly hindered in SW compared to DW. The influence of H
2O
2 and iron concentration on the efficiency of the photocatalytic process was evaluated. An increase in iron concentration from 2.6 to 10.4
mg
L
−1 showed only a slight improvement in SMX degradation and mineralization. However, an increase in H
2O
2 concentration up to 120
mg
L
−1 during photo-Fenton in DW decreased SMX solution toxicity from 85% to 20%, according to results of
Daphnia magna bioassays. The same behaviour was not observed after photo-Fenton treatment in SW. Despite 45% mineralization in SW, toxicity increased from 16% to 86% as shown by
Vibrio fischeri bioassays, which suggests that the intermediates generated in SW are different from those in DW. A SMX degradation pathway during the photo-Fenton treatment in DW is proposed.
Direct photolysis and solar TiO
2 photocatalysis of Trimethoprim (TMP) in different water matrices (demineralised and simulated seawater) have been studied. Direct photolysis yielded a similar, slow ...TMP degradation rate in both water matrices, and the formation of very stable photo-transformation products. Dissolved organic carbon decreased slightly after prolonged irradiation. The main intermediate identified was a ketone derivative (trimethoxybenzoylpyrimidine), which was proved to be a photosensitizer of TMP degradation. During TiO
2 photocatalysis, TMP was completely eliminated in both water matrices at a similar rate, however, the mineralization rate was appreciably reduced in seawater, which can be explained by the presence of inorganic species acting as hydroxyl radical scavengers, and directly affecting photocatalytic efficiency. Identification of intermediates showed differences between the two processes but hydroxylation, demethylation and cleavage of the original drug molecule were observed in both.
► We propose the systematic identification of transformation products of contaminants. ► The unique features of TOF, high sensitivity and accurate mass, are used for this purpose. ► The fragmentation ...pathways of parent species are used to predict transformation products. ► An accurate mass database including fragment ions is employed. ► Benefits and pitfalls of the proposed strategy are evaluated.
In this article, a systematic approach is proposed to assist and simplify the identification of transformation products (TPs) of organic contaminants. This approach is based on the use of characteristic fragmentation undergone by organic contaminants during MS/MS fragmentation events, and the relationship and consistency with the transformations experimented by these chemicals in the environment or during water treatment processes. With this in mind, a database containing accurate-mass information of 147 compounds and their main fragments generated by CID MS/MS fragmentation experiments was created using an LC–QTOF-MS/MS system. The developed database was applied to the identification of tentative TPs and related unexpected compounds in eight wastewater effluent samples. The approach comprises basically three stages: (a) automatic screening, (b) identification of possible TPs and (c) confirmation by MS/MS analysis. Parameters related to the search of compounds in the database have been optimized and their dependence with the exhaustiveness of the study evaluated. Eight degradation products, from the pharmaceuticals acetaminophen, amoxicillin, carbamazepine, erythromycin and azithromycin and from the pesticide diazinon, were identified with a high grade of accuracy. Three of them were confirmed by analysis of the corresponding analytical standards.
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