Vacuum-assisted headspace solid phase microextraction: Improved extraction of semivolatiles by non-equilibrium headspace sampling under reduced pressure conditions

A new headspace solid-phase microextraction (HSSPME) procedure carried out under vacuum conditions is proposed here where sample volumes commonly used in HSSPME (9 mL) were introduced into pre-evacuated commercially available large sampling chambers (1000 mL) prior to HSSPME sampling. The proposed procedure ensured reproducible conditions for HSSPME and excluded the possibility of analyte losses. A theoretical model was formulated demonstrating for the first time the pressure dependence of HSSPME sampling procedure under non equilibrium conditions. Although reduced pressure conditions during HSSPME sampling are not expected to increase the amount of analytes extracted at equilibrium, they greatly increase extraction rates compared to HSSPME under atmospheric pressure due to the enhancement of evaporation rates in the presence of an air-evacuated headspace. The effect is larger for semivolatiles whose evaporation rates are controlled by mass transfer resistance in the thin gas film adjacent to the sample/headspace interface. Parameters that affect HSSPME extraction were investigated under both vacuum and atmospheric conditions and the experimental data obtained were used to discuss and verify the theory. The use of an excessively large headspace volume was also considered. The applicability of Vac-HSSPME was assessed using chlorophenols as model compounds yielding linearities better than 0.9915 and detection limits in the low-ppt level. The repeatability was found to vary from 3.1 to 8.6%.     

Development of a solid phase dispersion-pressurized liquid extraction method for the analysis of suspected fragrance allergens in leave-on cosmetics

A new method based on solid phase dispersion-pressurized liquid extraction (PLE) followed by gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of 26 suspected fragrance allergens (all the regulated in the EU Cosmetics Directive amenable by GC, as well as pinene and methyleugenol) in cosmetic samples. The effects of the temperature, extraction time and solvent, and dispersing sorbent, affecting the whole proposed procedure, have been evaluated using a multifactor strategy. The optima conditions after the analysis of main and second order effects entailed the extraction at 120°C for 15 min, using hexane/acetone as solvent, and florisil as dispersing sorbent. The method performance has been studied, showing good linearity (R≥0.996) as well as good precision (RSD≤10%). Detection limits (S/N=3) ranged from 0.000001 to 0.0002% (w/w), values far below the established restrictions as regard labelling in the European Cosmetics Regulation. Reliability was demonstrated through the quantitative recoveries of all the studied compounds. The absence of matrix effects allowed quantification of the compounds by calibration with standard solutions. The analysis of 10 samples (several moisturizing and anti-wrinkle creams and lotions, hand creams, and sunscreen and after-sun creams), covering very different matrices, showed the presence of suspected allergens in all the analyzed samples; in fact, half of the samples contained an elevated number of them. Although the ubiquity of these compounds was demonstrated, labelling was in all cases in consonance with the European Cosmetics Regulation.     

Analysis of multi-class preservatives in leave-on and rinse-off cosmetics by matrix solid-phase dispersion

Matrix solid-phase extraction has been successfully applied for the determination of multi-class preservatives in a wide variety of cosmetic samples including rinse-off and leave-on products. After extraction, derivatization with acetic anhydride, and gas chromatography–mass spectrometry analysis were performed. Optimization studies were done on real non-spiked and spiked leave-on and rinse-off cosmetic samples. The selection of the most suitable extraction conditions was made using statistical tools such as ANOVA, as well as factorial experimental designs. The final optimized conditions were common for both groups of cosmetics and included the dispersion of the sample with Florisil (1:4), and the elution of the MSPD column with 5 mL of hexane/acetone (1:1). After derivatization, the extract was analyzed without any further clean-up or concentration step. Accuracy, precision, linearity and detection limits were evaluated to assess the performance of the proposed method. The recovery studies on leave-on and rinse-off cosmetics gave satisfactory values (>78% for all analytes in all the samples) with an average relative standard deviation value of 4.2%. The quantification limits were well below those set by the international cosmetic regulations, making this multi-component analytical method suitable for routine control. The analysis of a broad range of cosmetics including body milk, moisturizing creams, anti-stretch marks creams, hand creams, deodorant, shampoos, liquid soaps, makeup, sun milk, hand soaps, among others, demonstrated the high use of most of the target preservatives, especially butylated hydroxytoluene, methylparaben, propylparaben, and butylparaben.     

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 confirmed.     

Ice photolysis of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100): Laboratory investigations using solid phase microextraction

Here, we report for the first time a laboratory investigation into the photochemical degradation of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100) in ice solid samples using an artificial UV light source. Solid phase microextraction (SPME) was used as a sensitive extraction technique for monitoring trace amounts of the hydrophobic pollutant and its photoproducts. The results showed that ice photolysis kinetics for BDE-100 is similar to the one observed in the aqueous counterpart. The eight photoproducts identified consisted of brominated diphenyl ethers with lower bromine content and polybrominated dibenzofurans, suggesting two important photodegradation pathways for BDE-100 in ice solid samples: (i) stepwise reductive debromination and (ii) intramolecular elimination of HBr. Similarities in photochemical product arrays observed in the ice and water photolysis of BDE-100 were attributed to a similar mechanism for photochemical decomposition for both phases. Possible involvement of the water molecules in the reactions has been excluded by performing photolysis in D₂O ice solid and water samples. Taking advantage of the high preconcentration factor obtained with SPME at low temperatures, a SPME fiber cooled with liquid carbon dioxide down to 0 °C was used as a photoreaction support for BDE-100 allowing the identification of a greater number of photoproducts.     

Solid-phase microextraction gas chromatography-mass spectrometry determination of fragrance allergens in baby bathwater

A method based on solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) has been optimized for the determination of fragrance allergens in water samples. This is the first study devoted to this family of cosmetic ingredients performed by SPME. The influence of parameters such as fibre coating, extraction and desorption temperatures, salting-out effect and sampling mode on the extraction efficiency has been studied by means of a mixed-level factorial design, which allowed the study of the main effects as well as two-factor interactions. Excluding desorption temperature, the other parameters were, in general, very important for the achievement of high response. The final procedure was based on headspace sampling at 100 °C, using polydimethylsiloxane/divinylbenzene fibres. The method showed good linearity and precision for all compounds, with detection limits ranging from 0.001 to 0.3 ng mL⁻¹. Reliability was demonstrated through the evaluation of the recoveries in different real water samples, including baby bathwater and swimming pool water. The absence of matrix effects allowed the use of external standard calibration to quantify the target compounds in the samples. The proposed procedure was applied to the determination of allergens in several real samples. All the target compounds were found in the samples, and, in some cases, at quite high concentrations. The presence and the levels of these chemicals in baby bathwater should be a matter of concern. Baby exposure to fragrance allergens and other cosmetic ingredients through the daily bath     

Analysis of regulated suspected allergens in waters

Fragrance suspected allergens including those regulated by the EU Directive 76/768/EEC have been determined in different types of waters using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The procedure was based on headspace sampling (HS-SPME) using polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers and has been optimized by an experimental design approach. The method performance has been studied showing good linearity (R ≥ 0.994) as well as good intra-day and inter-day precision (RSD ≤ 12%). Detection limits (S/N = 3) ranged from 0.001 to 0.3 ng mL⁻¹. Reliability was demonstrated through the quantitative recoveries of the compounds in real water samples, including baby bathwaters, swimming pool waters, and wastewaters. The absence of matrix effects allowed quantification of the compounds by external aqueous calibration. The analysis of 35 samples of different types of waters showed the presence of suspected allergens in all the analyzed samples. All targets were found in the samples, with the exception of methyl eugenol and amyl cinnamic alcohol. Highest concentrations of suspected allergens were present in baby bathwaters, containing from 5 to 15 of the compounds at concentrations ranging from few pg mL⁻¹ to several hundreds of ng mL⁻¹.     

Confirmation of the formation of dichlorodibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxin in the photodegradation of triclosan by photo-SPME

Photodegradation is a possible way to eliminate organic pollutants from the environment but, at the same time, can be a source of toxic byproducts. The photochemical conversion of triclosan, a common pollutant in continental waters, into dichlorodibenzo-p-dioxin (DCDD) has been confirmed in our preliminary experiments employing photo-SPME (photo-solid-phase microextraction) using 18-W UV irradiation at 254-nm wavelength. Under these conditions, triclosan is rapidly photodegraded (70% of triclosan was degraded in 2 min); the most important novel aspect of this work is the conversion of triclosan to DCDD directly on the polydimethylsiloxane coating of the SPME fiber. Moreover, this conversion is also confirmed in non-buffered aqueous photodegradation experiments using SPME as the extraction technique. In all the experiments of this study, analysis was carried out by gas chromatography–electronic impact mass spectrometry (GC–EI/MS).     

Expanding the Applications of the Ionic Liquids as GC Stationary Phases: Plasticizers and Synthetic Musks Fragrances

The exceptional properties of the ILs make them ideal for gas chromatography stationary phases. New stationary phases exhibiting good separation selectivity, high efficiency, and high thermal stability are in high demand. Recently, several gas chromatographic capillary columns containing IL stationary phases of various polarities have been introduced on the market. The aim of this work is to extend the applications of the ILs as GC column coatings. The effectiveness of five different commercial IL columns (SLB™-IL59, SLB™-IL76, SLB™-IL82, SLB™-IL100 and SLB™-IL111) for the analysis of two different families of emerging contaminants of environmental concern (plasticizers and synthetic musk fragrances) has been explored. The results obtained for these two families of compounds are compared with the ones obtained when using a (5 %-phenyl)-methylpolysiloxane column. For three of these IL columns, applications have not yet been described. Good resolution for the most of the studied emerging pollutants belonging to five different analytical groups (adipates, phthalates, macrocyclic musks, nitromusks and polycyclic musks) was achieved in all the IL columns.

     

Low temperature SPME device: A convenient and effective tool for investigating photodegradation of volatile analytes

Hexachlorobenzene (HCB), a model volatile compound, was exposed to UV irradiation (16 W, 254 nm) after being sorbed in an internally cooled or low temperature solid-phase microextraction (LT-SPME) fibre. Photolysis took place directly on the polydimethylsiloxane coating of the LT-SPME fibre, yielding an “in situ” generation of photoproducts. Maintaining the temperature of the cold fibre at 0 °C eliminated, for the first time, problems of analyte losses due to volatilisation, inherent to the conventional room temperature photo-SPME studies. During the present studies, nearly complete photoremoval of HCB could be achieved within 20 min of irradiation. Photoreduction through photodechlorination was shown to be the main decay pathway in which lesser chlorinated congeners were sequentially formed as intermediates. Accordingly, initial generation of pentachlorobenzene was followed in order from 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene and 1,3,5-trichlorobenzene. The present findings were in agreement with previously reported results. Overall, the use of the LT-SPME device as a photoreaction support not only eliminated analyte losses but also greatly facilitated photochemical investigations of volatile compounds in general.