Plasma Chemistry and Plasma Processing, Oct 4, 2023
This paper is dedicated to the memory of Dr. Ulrich Kogelschatz, who honored us with his respect ... more This paper is dedicated to the memory of Dr. Ulrich Kogelschatz, who honored us with his respect and friendship. Dr. Kogelschatz had extraordinary talents and a broad and deep scientific culture, which he generously shared with all who approached him. He is deeply missed.
Journal of the American Society for Mass Spectrometry, Apr 1, 2004
An extensive study was carried out on HSA and non-enzymatically glycated HSA by enzymatic digesti... more An extensive study was carried out on HSA and non-enzymatically glycated HSA by enzymatic digestion with trypsin and endoproteinase Lys-C, with the aim of identifying specific glycated peptides deriving from enzymatic digestion of glycated HSA. They may be considered, in pectore, as advanced glycation end products/peptides. These compounds, important at a systemic level in diabetic and nephropathic subjects, are produced by enzymatic digestion of in vivo glycated proteins: They are related to the pathological state of patients and have been invoked as responsible for tissue modifications. The digested mixtures obtained by the two enzymes were analyzed by MALDI/MS and LC/ESI/MS n , and clear cut differences were found. First of all, the digestion products of glycated HSA are generally less abundant than those observed in the case of unglycated HSA, accounting for the lower proclivity of the former to enzymatic digestion. MS/MS experiments on doubly charged ions, comparisons with a protein database, and molecular modeling to identify the lysine NH 2 groups most exposed to glycation, identified some glycated peptides in digestion mixtures obtained from both types of enzymatic digestion. Residues 233 K, 276 K, 378 K, 545 K, and 525 K seem to be privileged glycation sites, in agreement with the fractional solvent accessible surface values calculated by molecular modeling.
Superoxide is one of the reactive oxygen species (ROS) in non-thermal plasmas generated by electr... more Superoxide is one of the reactive oxygen species (ROS) in non-thermal plasmas generated by electrical discharges in air at room temperature and atmospheric pressure. One important application of such plasmas is the activation of advanced oxidation processes for air and water decontaminating treatments. When in contact with aqueous media, ROS and notably superoxide can react at the plasma/liquid interface or transfer and react into the liquid. While the detection of superoxide in plasma-treated water has been reported in the literature, to the best of our knowledge, quantitative determinations are lacking. We report here the determination of superoxide rate of formation and steady-state concentration in water subjected to air non-thermal plasma in a streamer discharge reactor used previously to treat various organic contaminants. After detecting the presence of superoxide by spin-trapping and electron paramagnetic resonance analyses, we applied superoxide-selective fluorescent probes to carry out quantitative determinations. The first probe tested, 3′,6′-bis(diphenylphosphinyl) fluorescein (PF-1), was not sufficiently soluble, but the second one, fluorescein-bis-[(N-methylpyridinium-3-yl)sulfonate iodide] (FMSI), was applied successfully. Under typical plasma operating conditions, the rate of superoxide formation and its steady-state concentration were (0.27 ± 0.15) μM s −1 and (0.007 ± 0.004) nM, respectively. The procedure outlined here can be usefully applied to detect and quantify superoxide in water treated by different plasma sources in various types of plasma reactors.
Ionization of esters of carboxylic acids RCOOR (R = H, alkyl; R = alkyl) within the air plasma of... more Ionization of esters of carboxylic acids RCOOR (R = H, alkyl; R = alkyl) within the air plasma of the Atmospheric Pressure Chemical Ionization (APCI) source occurs largely via H + -transfer and, to a minor extent, via NO + association. The protonated ester MH + is normally observed as M 2 H + and as higher aggregates (M 3 H + , M 3 H + (H 2 O)) also at high source temperature. The behavior of M 2 H + upon collisional activation is consistent with the reported dissociation of proton-bound dimers to MH + species that, in turn, fragment according to the known paths of lowest energy. In addition, other important product ions form within the plasma, some in very high relative abundance, which are attributed to ion-molecule condensation reactions between neutral M and either MH + or M 2 H + resulting in the elimination of CO, R OH, alkene from the alkoxy moiety of the ester and HCOOH. A general scheme is proposed to account for the experimental observations, which suggest that the encounter complex formed between MH + and M or between M 2 H + and M may either collisionally relax to the protonated dimer or trimer, respectively, or react via covalent bond forming and cleaving steps to eliminate stable neutral molecules. The proposed scheme is supported by both the observed concentration dependence and the temperature dependence of the products relative abundances within the plasma. Such reactions can be the dominant process, as in the case of formate esters. A second significant ionization route involves addition of NO + to form M n NO + (n = 1, 2, 3). An additional product corresponding to [M 2 NO + -CO 2 ] is also observed with iso-and n-butyl formate esters.
Model prodrugs of resveratrol carrying protecting substituents at the hydroxyls have been synthes... more Model prodrugs of resveratrol carrying protecting substituents at the hydroxyls have been synthesised and tested. Resveratrol triacetate and resveratroltri-mPEG 1900 were formed by linking methyl groups or poly(ethylene glycol) chains, respectively, via carboxyester bonds. Resveratrol trimesylate, a molecule less susceptible to hydrolytic attack, was synthesised as well. This latter compound proved to be stable in vitro, while the carboxyester derivatives were slowly hydrolysed in solutions mimicking the gastric or intestinal environment, and rapidly converted to resveratrol in blood. In ex vivo permeation experiments with explanted intestinal segments, resveratrol and its triacetate derivative appeared in the basolateral compartment essentially as a mixture of Phase II metabolites. When the PEGylated derivative was provided on the apical side, unconjugated resveratrol accounted for about 50% of the compounds in the basolateral-side chamber. The same result was obtained by providing an equivalent physical mixture of resveratrol and PEG polymer, indicating that this behaviour is likely due to an adjuvating effect of PEG rather than to the covalent polymer conjugation. These observations suggest that the ester derivatives are rapidly hydrolysed at the intestinal surface or inside enterocytes, and are then processed as resveratrol. On the other hand, the mesylate was transported from the apical to the basolateral side without modification. It may thus be possible to enhance absorption and hinder metabolism of natural polyphenols by constructing pro-drugs incorporating bonds with appropriate resistance to enzymatic hydrolysis.
Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fie... more Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. A field trial was conducted from 2007 to 2009 in northeast Italy in order to evaluate the effectiveness of various types of vegetative filter strips to reduce spring-summer runoff of the herbicides mesotrione, metolachlor and terbuthylazine, widely used in maize, and to evaluate the effect of the rainfall characteristics on the runoff volume and concentration. Results show that without vegetative filter strip the herbicide load that reaches the surface water is about 5-6 g ha À1 year À1 for metolachlor and terbuthylazine (i.e. 0.5-0.9% of the applied rate), confirming that runoff from flat fields as in the Po Valley can have a minor effect on the water quality, and that most of the risk is posed by a few, or even just one extreme rainfall event with a return period of about 25-27 years, causing runoff with a maximum concentration of 64-77 lg L À1. Mesotrione instead showed rapid soil disappearance and was observed at a concentration of 1.0-3.8 lg L À1 only after one extreme (artificial) rainfall. Vegetative filter strips of any type are generally effective and can reduce herbicide runoff by 80-88%. Their effectiveness is steady even under severe rainfall conditions, and this supports their implementation in an environmental regulatory scheme at a catchment or regional scale.
The first result of complete mineralization of organic pollutants in water treatment by a plasmab... more The first result of complete mineralization of organic pollutants in water treatment by a plasmabased advanced oxidation process is reported. A dielectric barrier discharge reactor was used to study the effects of the pollutant initial concentration on the process rate and on the extent of mineralization. Using phenol as a model pollutant extensive product studies and carbon mass balance were performed with an integrated analytical approach. Notably, the concentrations of phenol and of its major oxidation intermediates were determined at different treatment times by 2 means of HPLC/UV-Vis and ion chromatography. In addition, the CO 2 released from the solution during the process and the residual total carbon in solution after the treatment were also determined by in line FT-IR analysis of the air flowing out of the reactor and by Total Carbon analysis of the liquid, respectively. Under fixed plasma conditions, both the process rate and the extent of mineralization increase as the pollutant initial concentration is decreased. Complete mineralization was achieved for 1•10-5 M phenol, a very encouraging result considering that much lower concentrations are typically found in polluted waters and that the lower the pollutant initial concentration the better the efficiency of plasma induced oxidation. Mineralization of phenol means that also all the intermediates formed during its oxidation are mineralized. Almost complete mineralization (95%) was also found in experiments with hydrochlorothiazide, a widespread diuretic pharmaceutical prominent in the list of emerging organic contaminants, demonstrating that plasma treatment is a promising approach for obtaining complete mineralization also of organic pollutants with complex chemical composition and structure.
Journal of the American Society for Mass Spectrometry, Jul 1, 2005
The ion chemistry of the title compounds, a nonafluorobutyl methyl ether and a hydrofluoropropane... more The ion chemistry of the title compounds, a nonafluorobutyl methyl ether and a hydrofluoropropane, is elucidated by a combination of studies using atmospheric pressure ionization mass spectrometry and triple quadrupole mass spectrometry. In the positive ion mode, the hydrofluoroether readily forms an [M Ϫ F] ϩ ion, attributable to hydronium ion induced dehydrofluorination, the product of which can be further hydrated to give a protonated hydrofluoroester. By contrast, the hydrofluoropropane does not react with the hydronium ion but rather gives hydrofluoroalkenylium cations via H atom and F atom abstraction by the dioxygen radical cation. In the negative ion mode, the fluorobutyl methyl ether undergoes dissociative electron capture with O 2 Ϫ• , O 2 Ϫ• (H 2 O), O 3 Ϫ• , and NO 2 Ϫ to generate the fluorobutoxy anion, which can dissociate by CF 2 AO loss to give the perfluorocarbanion when the precursor ions are internally excited. The hydrofluoropropane reacts readily with common atmospheric anions to form molecular complexes with F Ϫ , O 2 Ϫ• , and O 3 Ϫ• and the strongly H-bonded species, O 2 Ϫ• (HF) and F Ϫ (HF). Interestingly, isomeric pentafluoropropanes form in the reaction with O 2 Ϫ• , either O 2 Ϫ• (HF) or F Ϫ (HF), depending on the specific pattern of the fluoro substitution.
The aggregation behavior in nonpolar solvents of the octyl viologen (OV) salt with the hydrophobi... more The aggregation behavior in nonpolar solvents of the octyl viologen (OV) salt with the hydrophobic anion bis(trifluoromethanesulfonyl)amide (Tf2N-) has been investigated. 1H and 19F NMR, ESI-MS and DFT calculations suggest that large aggregates are formed in toluene, benzene and chloroform, where the salt is highly soluble. The lifetime of the aggregates is long enough to be detected as independent species by 1H and 19F NMR spectroscopy, together with the smaller neutral OV(Tf2N)2 cluster. This behavior is quite at variance with usual NMR detected equilibria where only average signals are generally observed. Large aggregates are also observed in ESI-MS spectra of toluene and chloroform solutions despite the well-known low-coordinating ability of Tf2N-. It is suggested that the structure of the large aggregates mimics the thermotropic smectic phase that this system exhibits near room temperature.
A new bench-top reactor employing a streamer discharge in air was developed and tested for potent... more A new bench-top reactor employing a streamer discharge in air was developed and tested for potential use in an advanced oxidation stage in water treatment processes. The complex heterogeneous system and the ensuing chemical processes were characterized using an integrated approach to map the morphology of the plasma/gas/liquid interface, identify the plasma short-lived excited species, determine the oxidants in solution and monitor the organic pollutants degradation. Three model pollutants were used in these experiments, Rhodamine B, phenol and Metolachlor. The first two are common standards used to evaluate the performance of advanced oxidation processes. Metolachlor is a widely used herbicide listed among the most important recalcitrant emerging organic pollutants. Energy efficiency, kinetics and products of our tests show a good performance of the reactor. Specifically, mineralization appears feasible also in the case of metolachlor.
Abstract Verapamil, a drug widely used to treat cardiovascular disorders and an important water p... more Abstract Verapamil, a drug widely used to treat cardiovascular disorders and an important water pollutant, has been subjected for the first time to advanced oxidation by air non-thermal plasma (NTP) in a previously described DBD reactor. Product analysis was performed to assess the extent of mineralization to CO 2 , quantified by FT-IR analysis, and to detect and identify oxidation intermediates by LC/ESI-MS/MS. Many intermediates form and their time profile was monitored during the treatment. Thorough mass spectrometric analysis and comparison with literature data on the oxidation of the functional groups of verapamil by the reactive species present in the air plasma allowed us to identify most of the intermediates formed by non-thermal plasma activation. The majority of the identified compounds can be attributed to reactions of verapamil with ozone, one of the major oxidizing species in our DBD reactor. A few intermediates, though, appear to form following direct attack by hydroxyl radicals, whereas there is no evidence of any byproduct attributable to reaction with reactive nitrogen species. When treated at low initial concentration verapamil is almost completely mineralized (98%), as determined by total carbon analysis.
Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes, May 29, 2018
Herbicides play an important role in the crops production, but their use may result in residues w... more Herbicides play an important role in the crops production, but their use may result in residues with undesirable effects on the environment. The determination of the herbicide dissipation rate in agricultural soil is an important issue for monitoring their environmental fate. As soil composition is one of the factors affecting herbicide persistence, this study aimed to evaluate the dissipation of three herbicides, terbuthylazine (TERB), metolachlor (METO) and mesotrione (MESO) in soils with contrasting texture. The field trial was conducted at the Padua University Experimental Farm (45.3 • N, 12.0 • E) in the Po Valley, northeast Italy in 2012. The persistence of three herbicides has been studied in three diverse soil textures (clay, sand and loam soil) at two different depths (0-5 and 5-15 cm). A randomized complete block design was used for this experiment with six plots (2 m × 2 m) for each of 3 treatments. TERB, METO and MESO were applied in May on maize as a formulated product (Lumax ®) with hand-held field plot sprayer at a dose of 3.5 L/ha. Soil organic carbon content was the highest in clay texture (1.10%) followed by loam soil (0.67%) and sandy soil (0.24%). The soil was sampled with a soil auger before herbicides treatment, and soon after treatment soil samples were taken to assess initial concentration, then at increasing times from spraying to evaluate field dissipation kinetics (t50). The dissipation of the herbicides in the treated plots was followed for nearly 2 months after their application. The herbicides were analysed by liquid chromatography-mass spectrometry. The dissipation of TERB, METO and MESO could be described by a pseudo first order kinetics. Within the herbicides, TERB showed the highest t50, followed by METO and MESO. Considering the tested soil, the highest t50 value was found for clay soil texture for TERB and METO, whereas for MESO there was no difference among different soils. Significant differences were found within the 2 soil depths for TERB and MESO only in sandy soil, for METO only in loam soil. In detail, considering the average of both depths, TERB and METO degraded slowly in clay soil (22 days and 16 days respectively) followed by loam soil (14 days and 7 days) and sandy soil (12 days and 5 days). On the other hand, MESO did not show significant differences (ranging from about 4 days in clay soil to 5 days in loam soil). These results suggest that soil texture have a large influence on the dissipation of TERB and METO, whereas no influence was observed on MESO.
Plasma Chemistry and Plasma Processing, Oct 4, 2023
This paper is dedicated to the memory of Dr. Ulrich Kogelschatz, who honored us with his respect ... more This paper is dedicated to the memory of Dr. Ulrich Kogelschatz, who honored us with his respect and friendship. Dr. Kogelschatz had extraordinary talents and a broad and deep scientific culture, which he generously shared with all who approached him. He is deeply missed.
Journal of the American Society for Mass Spectrometry, Apr 1, 2004
An extensive study was carried out on HSA and non-enzymatically glycated HSA by enzymatic digesti... more An extensive study was carried out on HSA and non-enzymatically glycated HSA by enzymatic digestion with trypsin and endoproteinase Lys-C, with the aim of identifying specific glycated peptides deriving from enzymatic digestion of glycated HSA. They may be considered, in pectore, as advanced glycation end products/peptides. These compounds, important at a systemic level in diabetic and nephropathic subjects, are produced by enzymatic digestion of in vivo glycated proteins: They are related to the pathological state of patients and have been invoked as responsible for tissue modifications. The digested mixtures obtained by the two enzymes were analyzed by MALDI/MS and LC/ESI/MS n , and clear cut differences were found. First of all, the digestion products of glycated HSA are generally less abundant than those observed in the case of unglycated HSA, accounting for the lower proclivity of the former to enzymatic digestion. MS/MS experiments on doubly charged ions, comparisons with a protein database, and molecular modeling to identify the lysine NH 2 groups most exposed to glycation, identified some glycated peptides in digestion mixtures obtained from both types of enzymatic digestion. Residues 233 K, 276 K, 378 K, 545 K, and 525 K seem to be privileged glycation sites, in agreement with the fractional solvent accessible surface values calculated by molecular modeling.
Superoxide is one of the reactive oxygen species (ROS) in non-thermal plasmas generated by electr... more Superoxide is one of the reactive oxygen species (ROS) in non-thermal plasmas generated by electrical discharges in air at room temperature and atmospheric pressure. One important application of such plasmas is the activation of advanced oxidation processes for air and water decontaminating treatments. When in contact with aqueous media, ROS and notably superoxide can react at the plasma/liquid interface or transfer and react into the liquid. While the detection of superoxide in plasma-treated water has been reported in the literature, to the best of our knowledge, quantitative determinations are lacking. We report here the determination of superoxide rate of formation and steady-state concentration in water subjected to air non-thermal plasma in a streamer discharge reactor used previously to treat various organic contaminants. After detecting the presence of superoxide by spin-trapping and electron paramagnetic resonance analyses, we applied superoxide-selective fluorescent probes to carry out quantitative determinations. The first probe tested, 3′,6′-bis(diphenylphosphinyl) fluorescein (PF-1), was not sufficiently soluble, but the second one, fluorescein-bis-[(N-methylpyridinium-3-yl)sulfonate iodide] (FMSI), was applied successfully. Under typical plasma operating conditions, the rate of superoxide formation and its steady-state concentration were (0.27 ± 0.15) μM s −1 and (0.007 ± 0.004) nM, respectively. The procedure outlined here can be usefully applied to detect and quantify superoxide in water treated by different plasma sources in various types of plasma reactors.
Ionization of esters of carboxylic acids RCOOR (R = H, alkyl; R = alkyl) within the air plasma of... more Ionization of esters of carboxylic acids RCOOR (R = H, alkyl; R = alkyl) within the air plasma of the Atmospheric Pressure Chemical Ionization (APCI) source occurs largely via H + -transfer and, to a minor extent, via NO + association. The protonated ester MH + is normally observed as M 2 H + and as higher aggregates (M 3 H + , M 3 H + (H 2 O)) also at high source temperature. The behavior of M 2 H + upon collisional activation is consistent with the reported dissociation of proton-bound dimers to MH + species that, in turn, fragment according to the known paths of lowest energy. In addition, other important product ions form within the plasma, some in very high relative abundance, which are attributed to ion-molecule condensation reactions between neutral M and either MH + or M 2 H + resulting in the elimination of CO, R OH, alkene from the alkoxy moiety of the ester and HCOOH. A general scheme is proposed to account for the experimental observations, which suggest that the encounter complex formed between MH + and M or between M 2 H + and M may either collisionally relax to the protonated dimer or trimer, respectively, or react via covalent bond forming and cleaving steps to eliminate stable neutral molecules. The proposed scheme is supported by both the observed concentration dependence and the temperature dependence of the products relative abundances within the plasma. Such reactions can be the dominant process, as in the case of formate esters. A second significant ionization route involves addition of NO + to form M n NO + (n = 1, 2, 3). An additional product corresponding to [M 2 NO + -CO 2 ] is also observed with iso-and n-butyl formate esters.
Model prodrugs of resveratrol carrying protecting substituents at the hydroxyls have been synthes... more Model prodrugs of resveratrol carrying protecting substituents at the hydroxyls have been synthesised and tested. Resveratrol triacetate and resveratroltri-mPEG 1900 were formed by linking methyl groups or poly(ethylene glycol) chains, respectively, via carboxyester bonds. Resveratrol trimesylate, a molecule less susceptible to hydrolytic attack, was synthesised as well. This latter compound proved to be stable in vitro, while the carboxyester derivatives were slowly hydrolysed in solutions mimicking the gastric or intestinal environment, and rapidly converted to resveratrol in blood. In ex vivo permeation experiments with explanted intestinal segments, resveratrol and its triacetate derivative appeared in the basolateral compartment essentially as a mixture of Phase II metabolites. When the PEGylated derivative was provided on the apical side, unconjugated resveratrol accounted for about 50% of the compounds in the basolateral-side chamber. The same result was obtained by providing an equivalent physical mixture of resveratrol and PEG polymer, indicating that this behaviour is likely due to an adjuvating effect of PEG rather than to the covalent polymer conjugation. These observations suggest that the ester derivatives are rapidly hydrolysed at the intestinal surface or inside enterocytes, and are then processed as resveratrol. On the other hand, the mesylate was transported from the apical to the basolateral side without modification. It may thus be possible to enhance absorption and hinder metabolism of natural polyphenols by constructing pro-drugs incorporating bonds with appropriate resistance to enzymatic hydrolysis.
Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fie... more Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. A field trial was conducted from 2007 to 2009 in northeast Italy in order to evaluate the effectiveness of various types of vegetative filter strips to reduce spring-summer runoff of the herbicides mesotrione, metolachlor and terbuthylazine, widely used in maize, and to evaluate the effect of the rainfall characteristics on the runoff volume and concentration. Results show that without vegetative filter strip the herbicide load that reaches the surface water is about 5-6 g ha À1 year À1 for metolachlor and terbuthylazine (i.e. 0.5-0.9% of the applied rate), confirming that runoff from flat fields as in the Po Valley can have a minor effect on the water quality, and that most of the risk is posed by a few, or even just one extreme rainfall event with a return period of about 25-27 years, causing runoff with a maximum concentration of 64-77 lg L À1. Mesotrione instead showed rapid soil disappearance and was observed at a concentration of 1.0-3.8 lg L À1 only after one extreme (artificial) rainfall. Vegetative filter strips of any type are generally effective and can reduce herbicide runoff by 80-88%. Their effectiveness is steady even under severe rainfall conditions, and this supports their implementation in an environmental regulatory scheme at a catchment or regional scale.
The first result of complete mineralization of organic pollutants in water treatment by a plasmab... more The first result of complete mineralization of organic pollutants in water treatment by a plasmabased advanced oxidation process is reported. A dielectric barrier discharge reactor was used to study the effects of the pollutant initial concentration on the process rate and on the extent of mineralization. Using phenol as a model pollutant extensive product studies and carbon mass balance were performed with an integrated analytical approach. Notably, the concentrations of phenol and of its major oxidation intermediates were determined at different treatment times by 2 means of HPLC/UV-Vis and ion chromatography. In addition, the CO 2 released from the solution during the process and the residual total carbon in solution after the treatment were also determined by in line FT-IR analysis of the air flowing out of the reactor and by Total Carbon analysis of the liquid, respectively. Under fixed plasma conditions, both the process rate and the extent of mineralization increase as the pollutant initial concentration is decreased. Complete mineralization was achieved for 1•10-5 M phenol, a very encouraging result considering that much lower concentrations are typically found in polluted waters and that the lower the pollutant initial concentration the better the efficiency of plasma induced oxidation. Mineralization of phenol means that also all the intermediates formed during its oxidation are mineralized. Almost complete mineralization (95%) was also found in experiments with hydrochlorothiazide, a widespread diuretic pharmaceutical prominent in the list of emerging organic contaminants, demonstrating that plasma treatment is a promising approach for obtaining complete mineralization also of organic pollutants with complex chemical composition and structure.
Journal of the American Society for Mass Spectrometry, Jul 1, 2005
The ion chemistry of the title compounds, a nonafluorobutyl methyl ether and a hydrofluoropropane... more The ion chemistry of the title compounds, a nonafluorobutyl methyl ether and a hydrofluoropropane, is elucidated by a combination of studies using atmospheric pressure ionization mass spectrometry and triple quadrupole mass spectrometry. In the positive ion mode, the hydrofluoroether readily forms an [M Ϫ F] ϩ ion, attributable to hydronium ion induced dehydrofluorination, the product of which can be further hydrated to give a protonated hydrofluoroester. By contrast, the hydrofluoropropane does not react with the hydronium ion but rather gives hydrofluoroalkenylium cations via H atom and F atom abstraction by the dioxygen radical cation. In the negative ion mode, the fluorobutyl methyl ether undergoes dissociative electron capture with O 2 Ϫ• , O 2 Ϫ• (H 2 O), O 3 Ϫ• , and NO 2 Ϫ to generate the fluorobutoxy anion, which can dissociate by CF 2 AO loss to give the perfluorocarbanion when the precursor ions are internally excited. The hydrofluoropropane reacts readily with common atmospheric anions to form molecular complexes with F Ϫ , O 2 Ϫ• , and O 3 Ϫ• and the strongly H-bonded species, O 2 Ϫ• (HF) and F Ϫ (HF). Interestingly, isomeric pentafluoropropanes form in the reaction with O 2 Ϫ• , either O 2 Ϫ• (HF) or F Ϫ (HF), depending on the specific pattern of the fluoro substitution.
The aggregation behavior in nonpolar solvents of the octyl viologen (OV) salt with the hydrophobi... more The aggregation behavior in nonpolar solvents of the octyl viologen (OV) salt with the hydrophobic anion bis(trifluoromethanesulfonyl)amide (Tf2N-) has been investigated. 1H and 19F NMR, ESI-MS and DFT calculations suggest that large aggregates are formed in toluene, benzene and chloroform, where the salt is highly soluble. The lifetime of the aggregates is long enough to be detected as independent species by 1H and 19F NMR spectroscopy, together with the smaller neutral OV(Tf2N)2 cluster. This behavior is quite at variance with usual NMR detected equilibria where only average signals are generally observed. Large aggregates are also observed in ESI-MS spectra of toluene and chloroform solutions despite the well-known low-coordinating ability of Tf2N-. It is suggested that the structure of the large aggregates mimics the thermotropic smectic phase that this system exhibits near room temperature.
A new bench-top reactor employing a streamer discharge in air was developed and tested for potent... more A new bench-top reactor employing a streamer discharge in air was developed and tested for potential use in an advanced oxidation stage in water treatment processes. The complex heterogeneous system and the ensuing chemical processes were characterized using an integrated approach to map the morphology of the plasma/gas/liquid interface, identify the plasma short-lived excited species, determine the oxidants in solution and monitor the organic pollutants degradation. Three model pollutants were used in these experiments, Rhodamine B, phenol and Metolachlor. The first two are common standards used to evaluate the performance of advanced oxidation processes. Metolachlor is a widely used herbicide listed among the most important recalcitrant emerging organic pollutants. Energy efficiency, kinetics and products of our tests show a good performance of the reactor. Specifically, mineralization appears feasible also in the case of metolachlor.
Abstract Verapamil, a drug widely used to treat cardiovascular disorders and an important water p... more Abstract Verapamil, a drug widely used to treat cardiovascular disorders and an important water pollutant, has been subjected for the first time to advanced oxidation by air non-thermal plasma (NTP) in a previously described DBD reactor. Product analysis was performed to assess the extent of mineralization to CO 2 , quantified by FT-IR analysis, and to detect and identify oxidation intermediates by LC/ESI-MS/MS. Many intermediates form and their time profile was monitored during the treatment. Thorough mass spectrometric analysis and comparison with literature data on the oxidation of the functional groups of verapamil by the reactive species present in the air plasma allowed us to identify most of the intermediates formed by non-thermal plasma activation. The majority of the identified compounds can be attributed to reactions of verapamil with ozone, one of the major oxidizing species in our DBD reactor. A few intermediates, though, appear to form following direct attack by hydroxyl radicals, whereas there is no evidence of any byproduct attributable to reaction with reactive nitrogen species. When treated at low initial concentration verapamil is almost completely mineralized (98%), as determined by total carbon analysis.
Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes, May 29, 2018
Herbicides play an important role in the crops production, but their use may result in residues w... more Herbicides play an important role in the crops production, but their use may result in residues with undesirable effects on the environment. The determination of the herbicide dissipation rate in agricultural soil is an important issue for monitoring their environmental fate. As soil composition is one of the factors affecting herbicide persistence, this study aimed to evaluate the dissipation of three herbicides, terbuthylazine (TERB), metolachlor (METO) and mesotrione (MESO) in soils with contrasting texture. The field trial was conducted at the Padua University Experimental Farm (45.3 • N, 12.0 • E) in the Po Valley, northeast Italy in 2012. The persistence of three herbicides has been studied in three diverse soil textures (clay, sand and loam soil) at two different depths (0-5 and 5-15 cm). A randomized complete block design was used for this experiment with six plots (2 m × 2 m) for each of 3 treatments. TERB, METO and MESO were applied in May on maize as a formulated product (Lumax ®) with hand-held field plot sprayer at a dose of 3.5 L/ha. Soil organic carbon content was the highest in clay texture (1.10%) followed by loam soil (0.67%) and sandy soil (0.24%). The soil was sampled with a soil auger before herbicides treatment, and soon after treatment soil samples were taken to assess initial concentration, then at increasing times from spraying to evaluate field dissipation kinetics (t50). The dissipation of the herbicides in the treated plots was followed for nearly 2 months after their application. The herbicides were analysed by liquid chromatography-mass spectrometry. The dissipation of TERB, METO and MESO could be described by a pseudo first order kinetics. Within the herbicides, TERB showed the highest t50, followed by METO and MESO. Considering the tested soil, the highest t50 value was found for clay soil texture for TERB and METO, whereas for MESO there was no difference among different soils. Significant differences were found within the 2 soil depths for TERB and MESO only in sandy soil, for METO only in loam soil. In detail, considering the average of both depths, TERB and METO degraded slowly in clay soil (22 days and 16 days respectively) followed by loam soil (14 days and 7 days) and sandy soil (12 days and 5 days). On the other hand, MESO did not show significant differences (ranging from about 4 days in clay soil to 5 days in loam soil). These results suggest that soil texture have a large influence on the dissipation of TERB and METO, whereas no influence was observed on MESO.
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