Marco Pazzi

Modelling the photochemical fate of ibuprofen in surface waters.

We show that the main photochemical processes involved in the phototransformation of anionic ibuprofen (IBP) in surface waters are the reaction with (•)OH, the direct photolysis and possibly the reaction with the triplet states of chromophoric dissolved organic matter ((3)CDOM). These conclusions were derived by use of a model of surface water photochemistry, which adopted measured parameters of photochemical reactivity as input data. The relevant parameters are the polychromatic UVB photolysis quantum yield (Φ(IBP) = 0.33 ± 0.05, μ±σ), the reaction rate constant with (•)OH (k(IBP,•OH)=(1.0 ± 0.3)⋅10(10) M(-1) s(-1)), the (1)O(2) rate constant (k(IBP,)( ¹O₂)= (6.0 ± 0.6)⋅10(4) M(-1) s(-1)), while the reaction with CO(3)(-•) can be neglected. We adopted anthraquinone-2-sulphonate (AQ2S) and riboflavin (Ri) as CDOM proxies and the reaction rate constants with the respective triplet states were k(IBP,3AQ2S)=(9.7 ± 0.2)⋅10(9) M(-1) s(-1) and k(IBP,3Ri) = 4.5⋅10(7) M(-1) s(-1). The reaction with (3)CDOM can be an important IBP sink if its rate constant is comparable to that of (3)AQ2S, while it is unimportant if the rate constant is similar to the (3)Ri* one. The photochemical pathways mainly lead to the transformation (oxidation and/or shortening) of the propanoic lateral chain of IBP, which appears to be significantly more reactive than the isobutyl one. Interestingly, none of the detected intermediates was produced by substitution on the aromatic ring.

Simultaneous determination of β2‐agonists in human urine by fast‐gas chromatography/mass spectrometry: method validation and clinical application

A fast screening protocol was developed and validated for the simultaneous determination of 15 beta(2)-agonists in human urine (bambuterol, cimbuterol, clenbuterol, fenoterol, formoterol, isoproterenol, mapenterol, metaproterenol, procaterol, ractopamine, ritodrine, salbutamol, salmeterol, terbutaline, tulobuterol). The overall sample processing includes deconjugation with enzyme hydrolysis, liquid-liquid extraction, followed by derivatization of the extract and detection of beta(2)-agonists trimethylsilyl-derivatives by fast-gas chromatography/electron impact-mass spectrometry (fast-GC/EI-MS). Sample extraction and derivatization were optimized with the purpose of improving recoveries and reaction yields for a variety of analytes with different structures simultaneously, while keeping the procedure simple and reliable. Validation parameters were determined for each analyte under investigation, including selectivity, linearity, intra- and inter-assay precision, extraction recoveries and signal to noise ratio (S/N) at the lowest calibration level. Fast-GC/MS sequences, based on the use of short columns, high carrier-gas velocity and fast temperature ramping, allow considerable reduction of the analysis time (7 min), while maintaining adequate chromatographic resolution. The overall GC cycle time was less than 9 min, allowing a processing rate of 6 samples/h. High MS-sampling rate, using a benchtop quadrupole mass analyzer, resulted in accurate peak shape definition under both scan and selected ion monitoring modes, and high sensitivity in the latter mode. The method was successfully tested on real samples arising from clinical treatments. Copyright (c) 2009 John Wiley & Sons, Ltd.

Study of dexamethasone urinary excretion profile in cattle by LC-MS/MS: comparison between therapeutic and growth-promoting administration.

Dexamethasone is a potent synthetic corticosteroid widely employed as a therapeutic agent in cattle. Besides this legal use, corticosteroids are also administered at low dosages as growth-promoters either alone or in combination with other steroids or with beta-agonists. For this reason, appropriate control plans are established to survey corticosteroid misuse, using liver or urine as biological matrices. Since few data are available about the kinetics of dexamethasone excretion in meat cattle, an experimental study was designed to assess the drug residue levels in urines following either a therapeutic (60 microg of dexamethasone sodium phosphate/kg b.w., for three consecutive days) or a growth-promoting schedule (0.7 or 1.4 mg of dexamethasone sodium phosphate per capita/day for 60 days). The urinary elimination of dexamethasone, which was predominantly excreted in the unmodified form, was determined by high-performance liquid chromatography/tandem mass spectrometry at different time intervals, i.e. during the treatments and after appropriate withdrawal times. Our findings confirm the high and rapid rate of dexamethasone urinary excretion irrespective of the nature of the treatment, and provide useful reference values that can be conveniently employed for forensic purposes.

Phototransformation of the sunlight filter benzophenone-3 (2-hydroxy-4-methoxybenzophenone) under conditions relevant to surface waters.

The UV filter benzophenone-3 (BP3) has UV photolysis quantum yield ΦBP3=(3.1±0.3)·10(-5) and the following second-order reaction rate constants: with (•)OH, k(BP3,(•)OH)=(2.0±0.4)·10(10) M(-1) s(-1); with the triplet states of chromophoric dissolved organic matter ((3)CDOM*), K(BP3,(3)CDOM*)=(1.1±0.1)·10(9) M(-1) s(-1); with (1)O2, k(BP3,(1)O2)=(2.0±0.1)·10(5) M(-1) s(-1), and with CO3(-•), k(BP3,CO3(-•))<5·10(7) M(-1) s(-1). These data allow the modelling of BP3 photochemical transformation, which helps filling the knowledge gap about the environmental persistence of this compound. Under typical surface-water conditions, direct photolysis and reactions with (•)OH and (3)CDOM* would be the main processes of BP3 phototransformation. Reaction with (•)OH would prevail at low DOC, direct photolysis at intermediate DOC (around 5 mg C L(-1)), and reaction with (3)CDOM* at high DOC. If the reaction rate constant with CO3(-•) is near the upper limit of experimental measures (5·10(7) M(-1) s(-1)), the CO3(-•) degradation process could be somewhat important for DOC<1 mg C L(-1). The predicted half-life time of BP3 in surface waters under summertime conditions would be of some weeks, and it would increase with increasing depth and DOC. BP3 transformation intermediates were detected upon reaction with (•)OH. Two methylated derivatives were tentatively identified, and they were probably produced by reaction between BP3 and fragments arising from photodegradation. The other intermediates were benzoic acid (maximum concentration ~10% of initial BP3) and benzaldehyde (1%).

The Formation and Self-Assembly of Long Prebiotic Oligomers Produced by the Condensation of Unactivated Amino Acids on Oxide Surfaces†

In situ IR and mass spectrometry evidence for the catalytic formation on SiO2 and TiO2 surfaces of glycine oligomers (poly-Gly) up to 16 units long by successive feeding with monomers from the vapor phase is presented. Parallel experiments carried out on hydroxyapatite resulted in the unreactive adsorption of Gly, thus indicating that the oligomerization was specifically catalyzed by the surfaces of SiO2 and TiO2 . Furthermore, the poly-Gly moved on the surface when contacted with H2 O vapor and formed self-assembled aggregates containing both helical and β-sheet-like structural motifs. These results indicate that polypeptides formed by the condensation of amino acids adsorbed on a mineral surface can evolve into structured supramolecular assemblies.

15-F2t isoprostane as biomarker of oxidative stress induced by tobacco smoke and occupational exposure to formaldehyde in workers of plastic laminates

BACKGROUND Formaldehyde (FA) is a suspected human carcinogen capable of inducing oxidative stress through different metabolic ways. FA may originate from tobacco smoke, several environmental sources, as well as occupational sources, like furnishing industries specialized in the production of pressed-wood and laminate products. OBJECT Our aim was to investigate the role of tobacco smoke and occupational exposure to air-FA in the induction of oxidative stress status by comparing FA-exposed with non-exposed subjects who smoked or did not. METHODS Enrollment of 105 subjects was made in an industry of plastic laminates, including both workers directly exposed to FA and non-exposed office personnel, as control group. 15-F(2t) isoprostane (15-F(2t) IsoP), detected by ELISA technique and urinary cotinine, detected by GC-MS, were used for evaluating oxidative stress and tobacco smoke exposure, respectively. Air-FA levels were detected by GC-MS. RESULTS FA concentrations were significantly higher in subjects occupationally exposed than the controls. Smoking habits and air-FA exposures independently induce the formation of 15-F(2t) IsoP and increase the oxidative stress level. CONCLUSIONS Our findings show, for the first time, that 15-F(2t) IsoP presents a dependency from both the smoking habit and air-FA exposures, and consequently, that these breathable pollutants could be considered as two important independent risk factors in increasing the oxidative stress in human beings.

Formaldehyde and tobacco smoke as alkylating agents: The formation of N-methylenvaline in pathologists and in plastic laminate workers

OBJECTIVE Aim of this study was to investigate the relationships between the concentration of formaldehyde in air and the alkylation of hemoglobin to form a terminal N-methylenvaline residue in three occupationally exposed groups: a) technicians of pathology wards, b) workers of the plastic laminates industry, and c) a control group. All subjects recruited in this study were also tested on their smoking habits. METHODS Formaldehyde adsorbed on passive air samplers was quantified by HPLC with UV detection (360 nm), cotinine was quantified by GC-MS. Terminal hemoglobin N-methylenvaline was determined by treating globine under reducing conditions with pentafluorophenyl isothiocyanate to yield a derivative, subsequently detected by GC-MS. One-way analysis of variance was performed to compare among the three groups the biomarkers considered in this study. RESULTS For air-FA and N-methylenvaline a difference between the three groups was detected (p < 0.0001) and a significant higher concentration in the two professionally exposed groups was proved. Mean values for FA (μg/m(3)): group a) 188.6, group b) 210.1, and group c) 41.4; mean values for N-methylenvaline (nmol/g of globin): group a) 377.9, group b) 342.8, and group c) 144.8. Conversely, the comparison between the two professionally exposed groups, a) vs b), does not show any significant difference highlighting similar exposition to FA and, consequently, similar biological response. Tobacco smoke proves to have a minor impact on the formation of N-methylenvaline molecular adduct. CONCLUSIONS A positive correlation was demonstrated between professional exposition to air-formaldehyde and hemoglobin alkylation to form N-methylenvaline molecular adduct in two occupationally exposed groups of subjects considered in the present study. In comparison with occupational exposition, tobacco smoke proved to have a minor impact on the formation of N-methylenvaline molecular adduct.

Assessing the phototransformation of diclofenac, clofibric acid and naproxen in surface waters: Model predictions and comparison with field data

Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC) and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper is to provide an overview of the prevailing photochemical processes, which these compounds undergo in the different conditions found in freshwater environments. The modelled photochemical half-life times of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and depth) and on the season. The model indicates that direct photolysis is the dominant degradation pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range, CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the •OH radical and with the triplet states of chromophoric dissolved organic matter (3CDOM*). The CLO intermediates arising from these processes and detected in this study (hydroquinone and 4-chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for humans. Hydroquinone is formed with only ∼5% yield upon CLO triplet-sensitised transformation, but it is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ∼50% upon triplet sensitisation and ∼10% by ·OH reaction. The comparison of model predictions with field data from a previous study yielded a very good agreement in the case of DIC and, when using 4-carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum yield approaches or even falls below the lower range of literature values.

Urban air and tobacco smoke as conditions that increase the risk of oxidative stress and respiratory response in youth

BACKGROUND Air pollution and tobacco smoke can induce negative effects on the human health and often leads to the formation of oxidative stress. OBJECTIVE The purpose of this study was to clarify the role of the urbanization degree and of passive exposure to tobacco smoke in the formation of oxidative stress. Thus, a group of non-smoking adolescents was recruited among those who live and attend school in areas with three different population densities. To each subject a spot of urine was collected to quantify 15-F2t isoprostane as a marker of oxidative stress and cotinine as a marker of passive exposure to tobacco smoke. Furthermore, respiratory functionality was also measured. RESULTS Multiple linear regression analysis results showed a direct correlation (p<0.0001) of 15-F2t isoprostane with both the urbanization and passive smoke. Lung function parameters proved significantly lower for the subjects living in the most populous city of Torino. CONCLUSION This remarks the negative effect that urbanization has on the respiratory conditions. Lastly, lung functionality presented a low inverse correlation with 15-F2t isoprostane, suggesting an independent mechanism than that of the urban factor.

Oxidative stress in adolescent passive smokers living in urban and rural environments

Purpose of this study was to study the oxidative stress status through the urinary 15-F(2t)-isoprostane (15-F(2t)-isoP) among a group of 168 adolescents, differently exposed to passive tobacco smoke. Subjects were enrolled, with written informed consent, between two populations of students living and attending school in two areas with different levels of urbanization in Piedmont Region, North-Western Italy. A general linear model (GLM) analysis was performed to evaluate the role of air pollution, dependent from selected degree of urbanization and of passive exposure to tobacco smoke, quantified through cotinine, in the synthesis of 15-F(2t)-isoP, measured with ELISA technique. Formaldehyde (FA) concentration in air was also evaluated as a primary confounding factor in oxidative stress but no significant differences between the two sites were found. Conversely, direct relationship between oxidative stress status and residence of adolescents was found: oxidative stress level was 31% higher for adolescents living in Chivasso (urban site) than for those living in Casalborgone (countryside area). Furthermore, also passive tobacco smoke exposure proved to play another important direct role in the distribution of 15-F(2t)-isoP levels (p<0.0001). Lastly, an inversely proportional relationship was found between the age of adolescents and 15-F(2t)-isoP (p<0.0001). Finally, the detection of such a sensitive biological response as a consequence of limited differences of environmental pollution and exposure to tobacco smoke passively breathed could provide new and useful knowledge for the appraisal of preventive strategies, particularly for young subjects.