Enrichment Factors of Perfluoroalkyl Oxoanions at the Air/Water Interface

The refractory, water-bound perfluoro-n-alkyl carboxylate F(CF_2)_nCO_2^− and sulfonate F(CF_2)_nSO_3^− surfactant anions reach remote locations by mechanisms that are not well understood. Here we report experiments in which the relative concentrations of these anions on the surface of microdroplets produced by nebulizing their aqueous solutions are measured via electrospray ionization mass spectrometry. Enrichment factors f (relative to Br^−: f(Br^−) ≡ 1) increase with n, asymptotically reaching f[F(CF_2)_nSO_3^−] ~2f[F(CF_2)_nCO_2^−] ~200 f(Br^−) values above n ~ 8. The larger f values for F(CF_2)_nSO_3^− over their F(CF_2)_nCO_2^− congeners are consistent with a closer approach of the bulkier, less hydrated −SO_3^− headgroup to the air/water interface. A hyperbolic, rather than the predicted linear log f[F(CF_2)_nCO_2^−] vs n dependence suggests the onset of conformational restrictions to interfacial enrichment above n ~4. Marine aerosols produced from contaminated ocean surface waters are therefore expected to be highly enriched in F(CF_2)_nCO_2^−/F(CF_2)_nSO_3^− species

Rapid determination of octanol–water partition coefficient using vortex-assisted liquid–liquid microextraction

Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high-performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol–water partitioning coefficients (Kow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium conditions between the octanolic and aqueous phases. Upon equilibration, separation was achieved using centrifugation and the octanolic microdrop was collected and analyzed in a HPLC system. Six model compounds with log Kow values ranging between ∼0.5 and 3.5 were used during the present investigations. The proposed method produced log Kow values that were consistent with previously published values and the recorded uncertainty was well within the acceptable log unit range. Overall, the key features of the proposed Kow determination procedure comprised speed, reliability, simplicity, low cost and minimal solvent consumption.EP is grateful to the Region of Crete (Perifereia Kritis) for funding. Financial support from the Spanish Government (Project CTQ2011-23968) is also acknowledged. I.P.R. also thanks “Caja de Ahorros del Mediterraneo (CAM)” for his predoctoral grant and financial support

Acid dissociation versus molecular association of perfluoroalkyl oxoacids: environmental implications

Perfluorooctanoate (PFO) and perfluorooctanesulfonate (PFOS) surfactant anions, once released, may rapidly reach remote regions. This phenomenon is puzzling because the water-bound anions of strong F-alkyl acids should be largely transported by slow oceanic currents. Herein, we investigate whether these hydrophobic F-alkyl oxoanions would behave anomalously under environmental conditions, as suggested elsewhere. Negative electrospray ionization mass spectra of micromolar aqueous PFO or PFOS solutions from pH 1.0 to 6.0 show (1) m/z ) 499 (PFOS) signals that are independent of pH and (2) m/z ) 413 (PFO) and 369 (PFO - CO_2) signals, plus m/z ) 213 (C_3F_7CO_2 -) and 169 (C_3F_7 -) signals at higher collision energies, and, below pH ~ 4, m/z ) 827 signals from a remarkably stable (PFO)_2H- cluster that increase with decreasing pH. Since the sum of the m/z ) 369, 413, and 827 signal intensities is independent of pH, that is, effectively encompasses all major species, we infer that pK_a(PFOSA) < 1.0 and pK_a(PFOA) < 1.0. We also derive K_2 ≤ 4 × 10^7 M^(-2) for the clustering equilibrium 2PFO + H^+ ⇌ (PFO)_2H. Thus, although (PFO)_2H is held together by an exceptionally strong homonuclear covalent hydrogen bond, neither PFOS nor PFO will associate or protonate significantly at environmentally relevant subnanomolar concentrations above pH ~ 1

UV-254 degradation of nicotine in natural waters and leachates produced from cigarette butts and heat-not-burn tobacco products.

Summarization: Nicotine is an important emerging contaminant widely detected in water resources. The main nicotine sources are human excretions from users and leaching from discarded tobacco product waste, which represents the most commonly littered item in urban areas and coasts. In this study, the UV254 photolytical fate of nicotine in natural water and leachates produced from conventional cigarettes (CCs) and the new generation heat-not-burn (HnBs) tobacco products is examined for the first time. The effect of UV254 irradiation on nicotine depletion in ultrapure water was initially studied. The reaction was pseudo first-order with respect to nicotine concentration at low concentrations and shifted to lower order at higher concentrations, an effect associated to absorption saturation. Although nicotine removal was fast, only 9.5% of the total organic carbon was removed after irradiation due to the formation of by-products. The chemical structures of six photo-products were derived by means of liquid and gas chromatography coupled to mass spectrometry. The photodegradation kinetics was found to depend on pH and faster kinetics were recorded when the monoprotonated form of nicotine was dominant (pH = 5–8). The presence of humic acids was found to slightly delay kinetics as they competed with nicotine for lamp irradiance, whereas the presence of salt had no effect on the direct photolysis of nicotine. Direct photolysis studies were also performed using natural waters. Compared to ultra-pure water, photodegradation was found to proceed slightly slower in river water, in similar kinetics in seawater, and relatively faster in rain water. The later was assumed to be due to the lower pH compared to the rest of the natural water tested. Leachates from used HnBs and smoked CCs were also submitted to UV254 irradiation and direct photolysis was found to proceed fast despite the high complexity of these matrices. Nonetheless, the total organic carbon in the system remained the same after irradiation due to the abundance of organics and photo-products formed. We take advantage of the present investigations and report the leaching behavior of nicotine from HnBs and CCs. Among others, we found that in HnBs ~70% of the total and bioavailable nicotine content remains in the tobacco sticks after operation and this percentage drops to 15% in CCs due to the reduction in mass after smoking. This finding demonstrated the importance of properly disposing tobacco product waste to prevent nicotine leaching in water bodies. Presented on: Environmental Researc

Sonochemical degradation of triclosan in water and wastewater

The sonochemical degradation of 5 μg l−1 triclosan, a priority micro-pollutant, in various environmental samples (seawater, urban runoff and influent domestic wastewater) as well as in model solutions (pure and saline water) was investigated. Experiments were conducted with a horn-type sonicator operating at 80 kHz frequency and a nominal applied power of 135 W, while solid-phase microextraction coupled with gas chromatography–electron capture detector (SPME/GC–ECD) was employed to monitor triclosan degradation. The latter followed pseudo-first order kinetics with the rate constant being (min−1): 0.2284 for seawater > 0.1051 for 3.5% NaCl in deionised water > 0.0597 for centrifuged urban runoff ∼ 0.0523 for untreated urban runoff > 0.0272 for deionised water > 0.0063 for wastewater influent. SPME/GC–ECD and SPME coupled with gas chromatography–mass spectrometry (SPME/GC–MS) were also used to check for the formation of chlorinated and other toxic by-products; at the conditions in question, the presence of such compounds was not confirmedL.S.-P. and R.B. acknowledge the regional government Junta de Galicia for their doctoral and travel grantsS

REAL-TIME WATER QUALITY MONITORING OF AN ARTIFICIAL LAKE USING A PORTABLE, AFFORDABLE, SIMPLE, ARDUINO-BASED OPEN SOURCE SENSOR

Water quality assessment is vital to identify existing problems and any changes that emerge in water sources over a period of time. Conventional water quality monitoring systems remain to be limited to on-site sample collection and further analysis in environmental laboratories. The progress in Arduino-based low-cost and open-source hardware has paved the way for the development of low-cost, portable, and on-site measuring platforms. In this work, we have assembled an Arduino-based open-source water testing platform out of commercially available sensors and controllers. The water testing system was powered by a 9 V battery and had the capability of measuring water turbidity, acidity, and temperature on-site in real-time. The calibration and validation studies were carried out to assess the measurement capabilities of turbidity and pH sensors in the lab using calibration samples and UV-Vis-NIR absorption spectroscopy. The water quality platform was tested in an artificial lake that is located at Sabanci University Campus (Istanbul, Turkey), which serves as a reservoir for treated wastewaters and rainwater. Untreated wastewater samples were collected from the wastewater treatment station of the university for comparison. The measurements performed on several locations along the coast of the artificial lake were also validated in the laboratory. The water testing platform showed significant potential for miniaturization and portability of such analytical platforms for on-site environmental monitoring

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - a review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed

Vacuum-Assisted HSSPME for food analysis

peer reviewe

Enhancement of biodegradability of industrial wastewaters by chemical oxidation pre-treatment.

Summarization: Chemical oxidation technologies are often employed for the treatment of complex industrial effluents that are not amenable to conventional biological methods. The role of chemical oxidation depends on the treatment objectives andmay vary from partial remediation to complete mineralization. In the case of partial treatment, chemical oxidation aims at the selective removal of the more bioresistant fractions and their conversion to readily biodegradable intermediates that can subsequently be treated biologically. Coupling chemical pre-oxidation with biological post-treatment is conceptually beneficial as it can lead to increased overall treatment efficiencies compared with the efficiency of each individual stage. This paper reviews recent developments and highlights some important aspects that need to be addressed when considering such integrated schemes.Παρουσιάστηκε στο: Journal of Chemical Technology and Biotechnolog

A comprehensive study on the effect of vacuum of targeted volatile compounds on HSSPME in a complex matrix: A softer efficient method to profile olive oil aromas

Headspace Solid-phase microextraction (HSSPME) is an easy, effective and selective technique for the analysis of volatiles and semi-volatiles compounds. Nevertheless, frequently a long time is requested to reach the equilibrium condition to maximize the extraction efficiency, thus pre equilibrium conditions are preferred as a compromise in term of throughput and sensitivity. Sampling under vacuum demonstrated an increasing extraction kinetics of analytes with a low affinity for the headspace without amplifying the temperature and thus preserving sensitive compounds. In this work Vacuum-SPME has been investigated for the first time for the analysis of a fat matrix, namely olive oil and deodorized oil with added standards, for understanding behavior of volatiles under vacuum. Gas chromatography coupled to a single quadrupole mass spectrometry was used for the final determination. A three variables (k= 3; temperature, extraction time and sample mass) inscribed rotatable central composite experimental design was used to optimize the sampling conditions. First analyses shown confirming effect of vacuum. Then, the work was oriented on lower temperature and extraction times conditions in order to highlight the gain of extraction rates in softer conditions, especially for semi- and lower volatiles. A series of compounds, covering the entire range of volatility and a wide chemical structure, were selected from olive oil to compare atmospheric and under vacuum conditions while another series were chosen in the same way to be added in deodorized oil. Advance analyses results made it possible to highlight patterns and thus to give explanation different observe phenomena concordant with theory