Solar light photodegradation of nicotine in the presence of aged polystyrene microplastics.

Limited information exists on the potential of aged microplastics to induce photodegradation of organic pollutants under sunlight irradiation. In this work, nicotine (NIC), a widespread emerging contaminant, was used as a model organic substrate to investigate this innovative degradation process. Polystyrene (PS) pellets were artificially aged and became rich in oxygenated moieties with their carbonyl index reaching 0.43 ± 0.04 after 4 d of aging. The degradation of NIC photosensitized by aged PS at different pH values was monitored for 6 h under simulated sunlight irradiation (650 W/m2). The maximum degradation rate was observed at pH = 11 (75 % NIC removal from a 10 mg L-1 solution containing 50 g L-1 aged PS pellets), suggesting that the unprotonated NIC is the most photoreactive form. Increasing the PS load from 50 to 200 g L-1 accelerated NIC degradation. The addition of 2.5 mg L-1 humic acids had a slight enhancement role (82 % NIC degradation), which confirms their effectiveness as photosensitizers. NIC photosensitization by aged PS was also studied in the presence of t-butanol (55 % NIC removal in solutions containing 100 mg L-1 t-butanol) and in anoxic conditions (NIC solution purged with N2; 95 % NIC removal), to gain insight into the respective roles of the potentially formed •OH and 1O2. The main photo-produced reactive species involved in NIC degradation likely were the triplet states of the PS beads (3PS*). Differently from most advanced oxidation processes, NIC's photodegradation by aged PS was not affected by increasing amount of chloride and we observed negligible differences between NIC degradation in ultra-pure water and seawater. The effectiveness of irradiated PS towards NIC photodegradation was also investigated in tap water and secondary wastewater. Overall, the possibility to decontaminate polluted water with waste-derived materials is interesting in the framework of circular economy.

Total and bioavailable polycyclic aromatic hydrocarbons in unused and operated heat-not-burn tobacco products and conventional cigarettes.

Tobacco product waste poses a global environmental issue, affecting urban and coastal areas alike. The present studies report, for the first time, the total and bioavailable polycyclic aromatic hydrocarbons (PAHs) concentrations in unused and operated heat-not-burn (HnBs) tobacco products. To enable direct comparisons, identical sets of studies were conducted using conventional cigarettes (CCs). Five low-molecular PAHs were determined in HnBs at total concentrations that were of the same order before and after operation (Σ5PAH = 47.37 ± 3.44 ng unit-1 and Σ5PAH = 69.36 ± 5.78 ng unit-1 in unused and used HnBs, respectively). The incomplete combustion of organics during smoking of CCs, yielded substantially higher amounts of PAHs with their sum (Σ10PAHs = 1449 ± 113 ng unit-1) being >20 times larger than those in HnBs. The tobacco and filter were the most contaminated parts in HnBs. In unused CCs, tobacco had the highest PAHs load and after smoking, the spent filter was the most contaminated part, containing ∼80% of the total amount of PAHs. Naphthalene was the most abundant PAH detected in all tobacco products. Despite the high total PAH concentrations found in smoked CCs, the sums of the bioavailable PAH concentrations were of the same order in all tested tobacco products (Σ5PAH = 61.38 ± 1.79 ng unit-1 in unused HnBs, Σ5PAH = 70.87 ± 7.67 ng unit-1 in used HnBs, Σ4PAH = 66.92 ± 5.95 ng unit-1 in unused CCs, and Σ6PAH = 47.94 ± 1.26 ng unit-1 in smoked CCs). This finding was related to smoking affecting PAHs' leachability from CCs and delaying their desorption from the solid matrix. Adjusting the pH, salt and humic acids content at environmentally relevant values did not affect PAHs leaching at 24 h of soaking. Finally, the leaching behavior of PAHs in natural waters (river water, rainwater, and seawater) was found similar to that in ultrapure water, experimentally verifying the ability of tobacco product waste to leach PAHs into the aquatic environment.

Sub-ambient temperature sampling of fish volatiles using vacuum-assisted headspace solid phase microextraction: Theoretical considerations and proof of concept.

The extraction of volatiles from perishable food at a sub-ambient temperature using headspace solid-phase microextraction (HS-SPME) has not been considered in the past due to the corresponding loss in sensitivity. We propose HS-SPME sampling under vacuum (Vac-HS-SPME) to compensate problems of sensitivity loss and achieve substantial improvement in extraction efficiencies whilst sampling at temperatures as low as 5 °C. The approach was applied to fish samples, representing a highly vulnerable perishable food sample. The theoretical considerations explaining the performance of Vac-HS-SPME at sub-ambient temperatures are discussed and related to the increase in gas diffusivities when sampling under vacuum. A comparative study between Vac- and regular HS-SPME for the extraction of 18 compounds from salmon was carried out at different temperatures (5, 30 and 40 °C) and sampling times (10-60 min). For the majority of the compounds, Vac-HS-SPME at 5 °C yielded similar or superior extraction efficiencies than regular HS-SPME even when sampling at 40 °C. However, four compounds were better extracted at 1 atm presumably due to the intensification of competitive adsorption of analytes on the SPME fiber under vacuum or the partial losses of more volatile analytes during air-evacuation in the presence of the frozen samples. Sub-ambient temperature sampling (5 °C) combined with Vac-HS-SPME was also applied to monitor the changes in the 18 compounds present in salmon, redfish, and cod refrigerated for up to five days. The results were compared to those obtained with regular HS-SPME at 40 °C. Overall, Vac-HS-SPME sampling at 5 °C represents a new and powerful approach for the analysis of volatiles in refrigerated foods, and has a great potential for future studies in quality control and freshness assessment.

Quantification of trace transformation products of rocket fuel unsymmetrical dimethylhydrazine in sand using vacuum-assisted headspace solid-phase microextraction.

Quantification of unsymmetrical dimethylhydrazine transformation products in solid samples is an important stage in monitoring of environmental pollution caused by heavy rockets launches. The new method for simultaneous quantification of unsymmetrical dimethylhydrazine transformation products in sand samples using vacuum-assisted headspace solid-phase microextraction without addition of water followed by gas chromatography-mass spectrometry is proposed. Decreasing air evacuation time from 120 to 20 s at 23 °C resulted in increased responses of analytes by 25-46% and allowed obtaining similar responses as after evacuation at -30 °C. The best combination of responses of analytes and their relative standard deviations (RSDs) was achieved after air evacuation of a sample (m = 1.00 g) for 20 s at 23 °C, incubation for 30 min at 40 °C, and 30-min extraction at 40 °C by Carboxen/polydimethylsiloxane (Car/PDMS) fiber. The method was validated in terms of linearity (R2=0.9912-0.9938), limits of detection (0.035 to 3.6 ng g-1), limits of quantification (0.12-12 ng g-1), recovery (84-97% with RSDs 1-11%), repeatability (RSDs 3-9%), and reproducibility (RSDs 7-11%). It has a number of major advantages over existing methods based on headspace solid-phase microextraction-lower detection limits, better accuracy and precision at similar or lower cost of sample preparation. The developed method was successfully applied for studying losses of analytes from open vials with model sand spiked with unsymmetrical dimethylhydrazine transformation products. It can be recommended for analysis of trace concentrations of unsymmetrical dimethylhydrazine transformation products when studying their transformation, migration and distribution in contaminated sand.

Vacuum-assisted headspace thin-film microextraction: Theoretical formulation and method optimization for the extraction of polycyclic aromatic hydrocarbons from water samples.

The thin films used in headspace thin-film microextraction (HS-TFME) enable higher sensitivity and superior extraction rates compared to other microextraction approaches, largely due to their greater surface area-to-volume ratio and extraction-phase volume. Nonetheless, analytes exhibiting a low affinity for the headspace and/or large partitioning between the extraction phase and headspace will still require more time to reach equilibrium. In this paper, we detail the development of a new method, termed as vacuum-assisted HS-TFME (Vac-HS-TFME), and we demonstrate how its use of vacuum conditions can accelerate the extraction kinetics of analytes with long equilibration times. The pressure-dependence of the extraction process was formulated and related to improvements in gas-phase diffusivity when lowering the total pressure. Four low-molecular-weight polycyclic aromatic hydrocarbons (PAHs) were used to experimentally verify the improvements in extraction efficiencies enabled by Vac-HS-TFME (vs. HS-TFME). To this end, the effects of temperature and extraction time on Vac-HS-TFME were investigated, with the results being compared to those obtained via regular HS-TFME. Furthermore, the use of a high-capacity sorbent in TFME allowed the positive effects of temperature and vacuum conditions to be combined successfully. Extraction-time profiles constructed at 30 and 50 °C revealed substantial acceleration in the overall extraction kinetics when sampling under vacuum conditions. At 50 °C, all of the analytes extracted via Vac-HS-TFME reached equilibrium within 45 min, whereas only two reached this state under atmospheric pressure. Vac-HS-TFME's analytical performance was evaluated under optimized conditions, and the results were compared to those obtained with regular HS-TFME. The findings revealed that for the two lighter PAHs, the performance of the two methods was similar since they were extracted close or at equilibrium. However, the calibration models for the two heavier PAHs tested here were linear over a wider concentration range (50-10000 ng L-1) when using Vac-HS-TFME, had superior intra-day repeatability (7.4% and 6.7% vs. 11% and 9.3% with regular HS-TFME), and the limits of detection were lower compared to regular HS-TFME (15 and 11 ng L-1 compared to 136 to 100 ng L-1 with regular HS-TFME). Finally, the analysis of spiked wastewater effluent samples showed that the matrix did not affect extraction. The proposed Vac-HS-TFME approach combines the advantages of low-pressure sampling and high-capacity sorbent, and has a great potential for future applications in food, flavour, environmental, and biological analyses.

UVC-induced degradation of cilastatin in natural water and treated wastewater.

This work reports for the first time the UVC photodegradation of cilastatin, a renal dehydropeptidase inhibitor co-adminstered with the imipenem antibiotic. Initially, solutions of cilastatin at varying concentrations were prepared in ultra-pure water and the direct photolysis of cilastatin was monitored under 254-nm irradiation. Degradation was slower at higher initial cilastatin concentrations, due to absorption saturation. Of the different eluting photoproducts, only one was tentatively identified as oxidized cilastatin bearing a sulfoxide group. UV-254 photolysis occurred faster at lower pH values, because the protonated forms of the molecule (H3A+, H2A) have both higher absorption coefficients and higher photolysis quantum yields than the non-protonated ones (HA-, A2-). The direct photolysis of cilastatin does not involve •OH, as excluded by experiments in which t-butanol was added as •OH scavenger, whereas the presence of humic acids inhibited photolysis due to competition for radiation absorption. The same explanation partially accounts for the observation that the photolysis kinetics of cilastatin was slower in tap water, river water and treated wastewater samples compared to ultra-pure water. Moreover, the direct photolysis quantum yield was also lower in water matrices compared to ultra-pure water. Similar findings reported for triclosan and the herbicide 2-methyl-4-chlorophenoxyacetic acid in previous studies might suggest that the water matrix components could carry out either physical quenching of cilastatin's excited states or back-reduction to cilastatin of the partially oxidized degradation intermediates. Overall, the present results demonstrate that UVC irradiation is a fast and efficient process for the degradation of cilastatin in natural water and treated wastewater.

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.

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

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.

The effect of vacuum: an emerging experimental parameter to consider during headspace microextraction sampling.

The effect of vacuum is an emerging experimental parameter to consider during optimization of a variety of headspace microextraction methodologies. The positive effect of vacuum was initially demonstrated for headspace solid-phase microextraction and was recently expanded to single-drop microextraction and higher capacity sorbents i.e. stir bar sorptive extraction. In all cases, sampling under vacuum greatly accelerated the extraction kinetics of analytes exhibiting long equilibration times under atmospheric pressure. At the same time, the extraction of analytes that reached equilibrium fast was not affected. In all optimized methods, extraction times were greatly reduced and/or sampling temperatures were lower to those reported with the standard methodology under atmospheric pressure. This work succinctly overviews the effect of vacuum on the different headspace microextraction technologies reported so far. The fundamental concepts describing the pressure dependence of each methodology are pulled together and presented in a simplified manner. The latest findings on the combined effects of vacuum and several selected experimental parameters typically examined during method optimization are then presented and the practical aspects of past outcomes are highlighted. The discussion also includes the air-evacuation step and the analysis of complex matrices. This article is intended for readers who are either new to the field of vacuum headspace microextraction sampling or its use and want to exploit this powerful approach. Graphical abstract.

A comprehensive study on the leaching of metals from heated tobacco sticks and cigarettes in water and natural waters.

The leaching behavior of Al, Cr, Ni, Cu, Zn, As, Se, Cd, Ba, Hg and Pb in water from two types of heat-not-burn tobacco sticks is presented here, and compared to that from conventional cigarettes. The total concentration of each metal in solid tobacco products was initially determined. Concentrations in used and unused tobacco sticks were similar and generally, lower than those in unused conventional cigarettes. Studies on the contribution of paper, filter and tobacco revealed that tobacco was the major source of metal contamination. Smoking conventional cigarettes reduced the total metal concentrations since a substantial amount of metals was retained in the ash; a post-consumption waste that is difficult to collect. Batch leaching tests were performed to determine dissolved concentrations as a function of time. With the exceptions of As and (in most cases) Hg that were not detected, metals were released at varying rates. At 24 h of soaking the percentage of metals leached ranged from 0.2-43%. The contribution of paper, filter and tobacco to the dissolved concentrations at 24 h of leaching was investigated and in almost all cases tobacco was the major source of metal contamination. The dissolved concentrations from ash were low as metals were strongly bound. Varying the pH, ionic strength and humic acids content at environmentally relevant values did not affect leaching of metals at 24 h of soaking. The use of river water, rain water and seawater as leachants was also not found to alter dissolved concentrations at 24 h compared to ultrapure water. The results presented here suggest that the consequences of improper disposal of tobacco products in the environment are two-sided and that next to the generation of plastic litter, discarded tobacco products can also act as point sources of metal contamination. Public education campaigns focusing on the environmental impact and best disposal practices are urgently needed.

A multifaceted investigation on the effect of vacuum on the headspace solid-phase microextraction of extra-virgin olive oil.

Headspace solid-phase microextraction (HS-SPME) is an easy, effective, and selective technique for the extraction of volatiles and semi-volatiles compounds. For the latter, longer equilibration times are needed, which are typically shortened by applying agitation or heating the sample. A less explored way to improve the extraction kinetics of analytes with a low-affinity for the headspace is to sample under vacuum conditions. The methodology that evolved from this approach was termed "vacuum-assisted HS-SPME" (Vac-HS-SPME) and was mainly used for water- and solid-based samples. The aim of this work was to investigate the effect of vacuum when dealing with non-aqueous liquid samples. For this purpose, the volatile profile of extra virgin olive oil was analyzed using a divinylbenzene/carboxen/polydimethylsiloxane fiber followed by gas chromatography-mass spectrometry. The effects of extraction temperature and sampling time were investigated using traditional one-variable at a time approach and a two-variable central component design for both Vac-HS-SPME and regular HS-SPME. The results showed an important enhancement in the extraction of semi-volatile compounds when using Vac-HS-SPME, and improved the information gained for the olive oil aroma fingerprint. A theoretical formulation of the underlying process was proposed, providing new insights into the SPME extraction theory. Lowering the sampling pressure effectively reduced gas-sided limitations and accelerated extraction kinetics. However, for viscous samples such as olive oils, the liquid-phase resistance played an important role and delayed extraction. Overall, applying heating (i.e. reducing the viscosity of the oily sample and increasing headspace concentrations) next to reducing the total pressure in the headspace is the best analytical HS-SPME strategy for obtaining fast a rich volatile profile from the oily samples.

Vacuum-assisted headspace sorptive extraction: Theoretical considerations and proof-of-concept extraction of polycyclic aromatic hydrocarbons from water samples.

The use of a thick sorbent coating in headspace sorptive extraction (HSSE) increases the amount of analytes extracted at equilibrium as well as the time needed to reach it. In this work we propose HSSE sampling under vacuum conditions to reduce equilibration times. A theoretical model is presented that describes the pressure dependence of the so-called vacuum-assisted HSSE (Vac-HSSE) method, and predicts the reduction in equilibration times when lowering the sampling pressure. We take advantage of the theoretical formulation to reach some general conclusions for HSSE on the relationship between the physical characteristics of the stir bar, uptake rates and equilibration times. The theoretical predictions were experimentally verified using water solutions spiked with naphthalene, acenaphthene and fluoranthene as model compounds. The effects of sampling temperature and extraction time under vacuum and regular pressure conditions were thoroughly investigated. The positive combined effect of heating the sample under low sampling pressure pointed that high humidity did not affect the performance of the extraction phase; an effect commonly recorded in headspace solid-phase microextraction. The extraction time profiles built at 25 and 55 °C visualized the substantial improvement in extraction kinetics with Vac-HSSE compared to the regular HSSE method. The results on naphthalene (assumed to evaporate relatively fast from the water sample) provided evidence that at 1 atm gas-sided resistance limited analyte uptake by the stir-bar and that this limitation could be effectively reduced by adopting the vacuum sampling approach. The accelerations of acenaphthene and fluoranthene suggested that gas-phase constraints limited both the evaporation and analyte uptake processes. Independent method optimization of HSSE under each pressure condition yielded a shorter sampling time for Vac-HSSE compared to the regular HSSE procedure (30 min vs. 60 min respectively). The analytical performances of the two optimized methods were evaluated and it was concluded that Vac-HSSE was performing similar (naphthalene and acenaphthene) or better (fluoranthene) than regular HSSE in half the sampling time needed.

Vacuum-assisted headspace single-drop microextraction: Eliminating interfacial gas-phase limitations.

Gas-phase limitations have been neglected in headspace single-drop microextraction (HS-SDME) and rate control has been assumed to primarily reside in the liquid water and/or organic phases, but not in the headspace. Herein we demonstrate the presence of interfacial gas constraints and propose using reduced headspace pressures to remove them. To describe the pressure dependence of HS-SDME, the system was decoupled into two interfacial steps: (i) the evaporation step (water-headspace interface) formulated using the two-film theory and (ii) the analyte uptake by the microdrop (headspace-microdrop interface) formulated using the resistance model. Naphthalene, acenaphthene, and pyrene were chosen as model analytes for their large Henry's law solubility constants in n-octanol (HOA > 103 M atm-1), and their low to moderate Henry's law volatility constants in water as a solvent (KH). We have found that extraction times were significantly shortened for all analytes by sampling at pressures well below the 1 atm used in the standard HS-SDME procedure. The acceleration of naphthalene extraction, whose facile evaporation into the headspace had been assumed to be practically pressure independent, highlighted the role of mass transfer through the interfacial gas layer on the organic solvent drop. The larger accelerations observed for acenaphthene and (especially) pyrene upon reducing the sampling pressure, suggested that gas-sided constraints were important during both the evaporation and uptake steps. Model calculations incorporating mass transfers at the headspace-microdrop interface confirmed that gas-phase resistance is largely eliminated (>96%) when reducing the sampling pressure from 1 to 0.04 atm, an effect that is nearly independent of analyte molecular mass. The relative importance of the two interfacial steps and their gas- and liquid-phase limitations are discussed, next to the use of KH and HOA to predict the positive effect of vacuum on HS-SDME.

UV-induced transformation of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone in water and treated wastewater.

In this work, we investigate the photolysis behavior of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (DDBQ), the only dibrominated benzoquinone detected in treated water so far. DDBQ solutions prepared in ultra-pure water were exposed to UV radiation centered at 254 nm (UV254), and the photolysis of the parent compound was monitored together with by-product formation. The DDBQ pseudo-first order photolysis rate constants decreased when increasing the initial DDBQ concentration, and this behavior was caused by saturation of absorption. The photodegradation kinetics was found not to depend on pH and 1-butanol addition, but was affected by humic acids and components that occur in both natural waters and treated wastewater. For the first time with this class of compounds, photolysis studies were also performed using natural and treated wastewater matrices, where photodegradation was always found to proceed significantly slower than in ultra-pure water. The implications for the radiation dose that is required to reach a given treatment target are discussed, and a numerical approach by which to foresee the extent of degradation inhibition is provided that should be taken into account when planning the UV254 treatment of DDBQ. The phototransformation of DDBQ yielded hydroxyderivatives, most likely via a debromination-hydroxylation pathway. In-silico toxicity screening suggested that the transformation of DDBQ into the detected hydroxyderivatives would not eliminate toxicity. Although the monohydroxylated derivative underwent relatively fast transformation, the dihydroxylated compound was found to accumulate during irradiation. As a compromise, the irradiation conditions that produce over 90% degradation of DDBQ in the studied samples, and at the same time keep by-product formation low are discussed.

Room temperature and sensitive determination of haloanisoles in wine using vacuum-assisted headspace solid-phase microextraction.

Headspace solid-phase microextraction (HSSPME) is a widespread technique used to extract trace amounts of haloanisoles from wine samples. A major challenge to overcome is the high ethanol content in wines that affects the solubilities of haloanisoles and reduces their headspace abundance. To overcome this obstacle and meet sensitivity requirements, reported HSSPME procedures typically suggest heating the wine samples and/or sampling for extended times. The present work proposes the use of vacuum-assisted HSSPME (Vac-HSSPME) to accelerate the extraction kinetics whilst sampling at room temperature. Although ethanol affected the physico-chemical properties of the target analytes, these changes were not sufficient to prevent the positive effect of vacuum on HSSPME sampling. To demonstrate the benefits of adopting the vacuum approach, Vac-HSSPME and regular HSSPME methods were independently optimized and the results were compared at all times. The effect of ethanol under each pressure condition was also discussed. Under the optimum conditions found, Vac-HSSPME sampling for 30 min at room temperature at 25 °C yielded lower detection limits (0.13 to 0.19 ng L-1) than those obtained with regular HSSPME sampling for 30 min at 55 °C (0.26 to 0.76 ng L-1). The proposed Vac-HSSPME method was successfully applied to quantify haloanisoles in bottled red wines and a discussion on the effect of wine volatiles was included. The standard addition method was used to minimize matrix effects. The increase in total pressure due to the presence of ethanol and other volatile wine components did not reduce the positive effect of vacuum on HSSPME. Nonetheless, in accordance to past HSSPME methods, the limits of detection and quantification were affected due to the noise level increase and analyte interaction with matrix. The proposed Vac-HSSPME procedure was applied to twelve bottled red wines and one sample was found positive on 2,4,6-trichloronanisole.

Plastic pellets, meso- and microplastics on the coastline of Northern Crete: Distribution and organic pollution.

Plastic pollution in the marine environment is one of the foremost environmental problems of our time, as it affects wildlife and human health both directly and indirectly through the effects of contaminants carried by microplastics. This study investigates the temporal and spatial distribution of plastic pellets and fragments in sandy beaches along the coastline of Northern Crete, during 2013. Their densities varied throughout the year in each beach, with highest densities during the summer and towards the upper parts of the beaches. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) sorbed on microplastics sampled from nine sandy beaches of Northern Crete was quantified using Gas chromatography - Ion Trap Mass Spectrometry (GC-ITMS). PAHs concentrations ranged from non-detectable levels to 1592 ng/g and fluctuated between sampling periods. Based on the observed patterns of meso- and microplastics distribution, practical guidelines are proposed to minimize the entrance of microplastics into the seawater wherefrom they are exceptionally difficult to collect, if mitigation actions are to be applied.

Determination of transformation products of unsymmetrical dimethylhydrazine in water using vacuum-assisted headspace solid-phase microextraction.

A new, sensitive and simple method based on vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) followed by gas chromatography-mass-spectrometry (GC-MS), is proposed for the quantification of rocket fuel unsymmetrical dimethylhydrazine (UDMH) transformation products in water samples. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. For these analytes and within shorter sampling times, Vac-HSSPME yielded detection limits (0.5-100 ng L-1) 3-10 times lower than those reported for regular HSSPME. Vac-HSSPME sampling for 30 min at 50 °C yielded the best combination of analyte responses and their standard deviations (<15%). 1-Formyl-2,2-dimethylhydrazine and formamide were discarded because of the poor precision and accuracy when using Vac-HSSPME. The recoveries for the rest of the analytes ranged between 80 and 119%. The modified Mininert valve and Thermogreen septum could be used for automated extraction as it ensured stable analyte signals even after long waiting times (>24 h). Finally, multiple Vac-HSSME proved to be an efficient tool for controlling the matrix effect and quantifying UDMH transformation products.

Vacuum-assisted headspace solid-phase microextraction: A tutorial review.

Headspace solid-phase microextraction (HSSPME) sampling under vacuum conditions is a new and effective approach to accelerate the extraction kinetics of analytes with a low affinity for the headspace. Vacuum-assisted HSSPME (Vac-HSSPME) evolved from this approach and the resulting methods were always found to yield high extraction efficiencies and very good sensitivities within short sampling times and at mild temperatures. Vac-HSSPME preserves the simplicity of regular HSSPME and the only extra step required is that of air-evacuating the sample container before or after introducing the sample. Moreover, fast implementation of the technique is possible when using the latest, simplified and easy to construct sample container that can hold constant low-pressure conditions for extended sampling times. The main objective of the current tutorial is to provide a general strategy that can be applied towards the development of new Vac-HSSPME methods. The most important outcomes of past theoretical investigations are highlighted and a simple criterion for predicting the effect of vacuum on HSSPME sampling of water or water-containing samples is outlined. This theoretical discussion is then used as a background to elucidate the combined effects of low sampling pressure and several other experimental parameters on HSSPME sampling. Specific implications unique to Vac-HSSPME are also discussed, providing practical tips and a troubleshooting guide to new users. The great benefits of adopting the Vac-HSSPME approach are further demonstrated by reviewing all past applications reporting the quantitative and/or qualitative determination of compounds with a low tendency to escape to the headspace in a variety of samples. Vacuum is a new experimental parameter to control and exploit during HSSPME method optimization. The potential applications of Vac-HSSPME in areas like food, environmental and biological analysis are numerous and still remain to be explored.

Vacuum-assisted headspace-solid phase microextraction for determining volatile free fatty acids and phenols. Investigations on the effect of pressure on competitive adsorption phenomena in a multicomponent system.

This work proposes a new vacuum headspace solid-phase microextraction (Vac-HSSPME) method combined to gas chromatography-flame ionization detection for the determination of free fatty acids (FFAs) and phenols. All target analytes of the multicomponent solution were volatiles but their low Henry's Law constants rendered them amenable to Vac-HSSPME. The ability of a new and easy to construct Vac-HSSPME sampler to maintain low-pressure conditions for extended sampling times was concurrently demonstrated. Vac-HSSPME and regular HSSPME methods were independently optimized and the results were compared at all times. The performances of four commercial SPME fibers and two polymeric ionic liquid (PIL)-based SPME fibers were evaluated and the best overall results were obtained with the adsorbent-type CAR/PDMS fiber. For the concentrations used here, competitive displacement became more intense for the smaller and more volatile analytes of the multi-component solution when lowering the sampling pressure. The extraction time profiles showed that Vac-HSSPME had a dramatic positive effect on extraction kinetics. The local maxima of adsorbed analytes recorded with Vac-HSSPME occurred faster, but were always lower than that with regular HSSPME due to the faster analyte-loading from the multicomponent solution. Increasing the sampling temperature during Vac-HSSPME reduced the extraction efficiency of smaller analytes due to the enhancement in water molecule collisions with the fiber. This effect was not recorded for the larger phenolic compounds. Based on the optimum values selected, Vac-HSSPME required a shorter extraction time and milder sampling conditions than regular HSSPME: 20 min and 35 °C for Vac-HSSPME versus 40 min and 45 °C for regular HSSPME. The performance of the optimized Vac-HSSPME and regular HSSPME procedures were assessed and Vac-HSSPME method proved to be more sensitive, with lower limits of detection (from 0.14 to 13 µg L-1), and better intra-day precision (relative standard deviations values < 10% at the lowest spiked level) than regular HSSPME for almost all target analytes. The proposed Vac-HSSPME method was successfully applied to quantify FFAs and phenols in milk and milk derivatives samples.