Marco Vincenti

Photocatalytic and photolytic transformation of chloramben in aqueous solutions

The photocatalytic degradation of chloramben (3-amino-2,5-dichlorobenzoic acid) was investigated in aqueous solutions containing TiO2 suspensions under irradiation with simulated solar light. The primary degradation of the herbicide, the mineralisation of the organic carbon to CO2 and the formation of chloride ion from organic chlorine proved to be relatively fast, whereas the conversion of organic nitrogen into ammonium and nitrate ions took place only at delayed irradiation times. Photolytic degradation processes proved also to be active in the examined time interval, but they were far from producing complete mineralisation, leaving considerable amounts of residual organic products. Various aromatic intermediates that originated from chloramben during the photocatalytic treatment were detected and identified using GC-MS. Similarly, the main aromatic products arising from photolytic decomposition were also identified, and, in turn, they proved to undergo complete mineralisation upon addition of TiO2.

Simultaneous analysis of several synthetic cannabinoids, THC, CBD and CBN, in hair by ultra-high performance liquid chromatography tandem mass spectrometry. Method validation and application to real samples

A simple procedure for the quantitative detection of JWH-018, JWH-073, JWH 200, JWH-250, HU-210, Δ(9)-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) in hair has been developed and fully validated. After digestion with NaOH and liquid-liquid extraction, the separation was performed with an ultra-high performance liquid chromatography system coupled to a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The absence of matrix interferents, together with excellent repeatability of both retention times and relative abundances of diagnostic transitions, allowed the correct identification of all analytes tested. The method was linear in two different intervals at low and high concentration, with correlation coefficient values between 0.9933 and 0.9991. Quantitation limits ranged from 0.07 pg/mg for JWH-200 up to 18 pg/mg for CBD The present method for the determination of several cannabinoids in hair proved to be simple, fast, specific and sensitive. The method was successfully applied to the analysis of 179 real samples collected from proven consumers of Cannabis, among which 14 were found positive to at least one synthetic cannabinoid.

Sunlight Photodegradation of 2,4,5-Trichlorophenoxy-acetic Acid and 2,4,5-Trichlorophenol on TiO2. Identification of Intermediates and Degradation Pathway

The photocatalytic degradation of 2,4,5-trichlorophenoxyacetic acid and 2,4,5-trichlorophenol has been investigated in oxygenated aqueous suspensions of TiO2. Complete mineralization to CO2 and HC1 occurs with half-lives of 30–90 minutes. The effect of loading and thermal pre-treatment of the semi-conductor catalyst, as well as the influence of added chloride ions have been examined. In the degradation of the 2,4,5-trichlorophenoxyacetic acid, several intermediates were detected by gas-chromatographic/mass-spectrometric techniques. A scheme for the photodegradation is formulated.

Formation of Condensation Products in Advanced Oxidation Technologies: The Photocatalytic Degradation of Dichlorophenols on TiO2.

Photocatalytic treatment of dichlorophenols (DCPs) leads to the formation of condensation products. These products were identified as polyhydroxyPCBs. Depending on the initial DCP isomer, different extents and yields of polyhydroxyPCB formation (up to 1%) and different types of polyhydroxyPCBs were observed. The formation of dehalogenated hydroxyphenols and hydroxytrichlorobiphenyls in the presence of oxygen suggests that, in addition to oxidative pathways, reductive pathways are also operating. In contrast to direct photolysis by UV irradiation, no evidence of hydroxypolychlorodibenzo-p-dioxins or dibenzofurans was found. PolyhydroxyPCBs are destroyed in the same time window as the initial DCP. The similarities between this photocatalytic process and other advanced oxidation processes (AOP) based on . 0H radical chemistry are discussed.

Light-assisted 1,4-dioxane degradation

Abstract The oxidative degradation induced by light of 1,4dioxane been investigated in homogeneous solution in the presence of inorganic peroxides (either hydrogen peroxide or peroxydisulfate) and under heterogeneous photocatalytic conditions in the presence of titanium dioxide. The effect of photon energy spectral distribution, pH, O2 and scavengers has been examined. The degradation mechanism involves common intermediates. Ethylene glycol diformate was observed as the main intermediate. In the presence of UV light peroxydisulfate showed high degradation efficiency. A tentative chain radical oxidation mechanism is postulated. The distinctive features of heterogeneous photocatalytic treatment were the good efficiency under simulated solar spectrum and the absence of inhibition of the degradation rate by HCO3−. The presence of peroxydisulfate enhances the TiO2 photocatalytic degradation rate.

Phototransformations of nitrogen containing organic compounds over irradiated semiconductor metal oxides: Nitrobenzene and Atrazine over TiO2 and ZnO

Abstract The photocatalytic behaviour of nitrobenzene and atrazine over titanium dioxide and zinc oxide has been compared. Whereas the final products are the same, the intermediate distribution depends on the semiconductor nature. Both nitrate and ammonium ions are formed; nitrite represents a noticeable product in the early part of nitrobenzene degradation.

Identification of photocatalytic degradation pathways of 2-Cl-s-triazine herbicides and detection of their decomposition intermediates

Abstract the photocatalytic degradation of three 2-chloro-s-triazine herbicides (simazine, propazine, atrazine) over TiO 2 particles under simulated solar light has been investigated. In the early steps, the degradation progresses through competitive reactions such as oxidation of the side alkyl chain and substitution of chlorine with hydroxyl groups, the last process occurring for less than 10% of degradation. Further oxidative processes give rise to the formation of dealkylated products. Several intermediates have been detected by GC-MS and comprehensive degradation schemes are proposed. The three herbicides, bearing different alkyl groups, exhibit relevant differences in the relative role of the competitive degradation pathways.

Photocatalytic degradation of naphthalene in aqueous TiO2 dispersions: Effect of nonionic surfactants

The decomposition of naphthalene in the presence of TiO2 dispersions irradiated with simulated solar light has been investigated in water and in aqueous Brij 35 solutions, used to wash soil samples containing the adsorbed pollutant. The monitoring of the reaction system performed during the treatment showed the formation of various aromatic intermediates, in turn degraded, which were identified using suitable analytical techniques. Fast and complete mineralization of naphthalene to CO2 was achieved when working in the absence of additives, whereas a neat inhibition of the degradation was observed in the presence of amphiphiles and other organic components coming from soil. Experimental conditions under which surfactant-containing washes can be treated were investigated and defined.

Photocatalytic mineralization of nitrogen-containing benzene derivatives

Abstract The photocatalytic mineralization of nitrobenzene, nitrosobenzene, phenylhydroxylamine, aniline and 4-nitrosophenol has been investigated in aerated conditions. In slightly acidic TiO 2 suspensions, all these compounds proved to undergo quantitative formation of carbon dioxide, whereas nitrogen is converted into nitrate and ammonium ions. The mechanism of ammonium ion release is suggested. Ammonium ions are not generated by reduction of nitrate or nitrite ions, but directly from partly oxidized and unstable intermediates, such as, for example, quinonemonoimine and aliphatic imines. Ammonium ions are formed from nitro- and nitroso-derivatives through reduction of the nitrogen-containing substituent. The reductive pathway prevents detachment of nitro- and nitroso-groups as either nitrate or nitrite ion from the organic moiety. Quite specularly, from phenylhydroxylamine, aniline and aminophenol, ammonium ions are released by means of a partially oxidative pathway. Thus, the temporal evolution of the [NO 3 - ]/[NH 4 + ] concentration ratio, besides other experimental conditions (pH, photon flux, reactant concentrations), depends largely on both the initial oxidation state of the nitrogen and the nature of the starting organic substrate (e.g. 4-nitrosophenol vs. nitrosobenzene).

Application of mass spectrometry to hair analysis for forensic toxicological investigations.

The increasing role of hair analysis in forensic toxicological investigations principally owes to recent improvements of mass spectrometric instrumentation. Research achievements during the last 6 years in this distinctive application area of analytical toxicology are reviewed. The earlier state of the art of hair analysis was comprehensively covered by a dedicated book (Kintz, 2007a. Analytical and practical aspects of drug testing in hair. Boca Raton: CRC Press and Taylor & Francis, 382 p) that represents key reference of the present overview. Whereas the traditional organization of analytical methods in forensic toxicology divided target substances into quite homogeneous groups of drugs, with similar structures and chemical properties, the current approach often takes advantage of the rapid expansion of multiclass and multiresidue analytical procedures; the latter is made possible by the fast operation and extreme sensitivity of modern mass spectrometers. This change in the strategy of toxicological analysis is reflected in the presentation of the recent literature material, which is mostly based on a fit-for-purpose logic. Thus, general screening of unknown substances is applied in diverse forensic contexts than drugs of abuse testing, and different instrumentation (triple quadrupoles, time-of-flight analyzers, linear and orbital traps) is utilized to optimally cope with the scope. Other key issues of modern toxicology, such as cost reduction and high sample throughput, are discussed with reference to procedural and instrumental alternatives.