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This work describes a new method for the determination of organic compounds in solid samples based on the equilibrium desorption of the analytes in an aqueous phase followed by stir bar sorptive-dispersive microextraction (SBSDME). Sand samples, contaminated with UV filters due to bathing and recreational activities, were dispersed in an aqueous medium by using a coated stir bar with CoFe 2 O 4 @oleic acid magnetic nanoparticles. The UV filters were physically desorbed from the surface of the sand particles and rapidly adsorbed on the hydrophobic coating of the nanoparticles, which were retrieved by means of their magnetism after stopping the stirring. In this manner, both preconcentration of the analytes and clean-up were simultaneously accomplished without the requirement of any additional sample preparation steps. After extraction, the analytes were desorbed in ethanol and then analyzed by gas chromatography-mass spectrometry (GC–MS). The main variables involved in the extraction process (i.e., sorbent amount, extraction time, pH and ionic strength) were studied to provide the best extraction efficiencies and maximum enrichment factors. Under the selected conditions, the figures of merit of the proposed method were evaluated providing limits of detection in the low ng g −1 range, enrichment factors between 23 and 80, and relative standard deviations (RSD%) below 14% for all the target analytes. Matrix effects were observed in real costal sand samples and thus standard addition calibration was employed for quantification. The method was successfully applied to the analysis of UV filters in several coastal sand samples of different origin. This work expands the analytical potential of the novel SBSDME approach to the determination of organic compounds in solid matrices. [ABSTRACT FROM AUTHOR]

An analytical method for the determination of tetrahydrocannabinol (THC) at trace level in cosmetics is presented. As psychoactive compound, the presence of THC in consumer products should be avoided. However, it might be unintentionally present in cannabidiol-rich or hemp-based products by contamination or isomerization of cannabidiol. Due to the low concentrations expected, a sensitive and selective method is necessary for the analytical control of these products. In this sense, the presented method is based on stir bar sorptive dispersive microextraction (SBSDME) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this work, a magnetic composite made of CoFe 2 O 4 magnetic nanoparticles embedded in a commercial reverse-phase polymer (Strata™-X-RP) was employed as magnetic sorbent material taking advantage of its affinity to the target analyte. Under the optimized conditions, the method was validated and showed good analytical features in terms of linearity (at least up to 10 ng mL−1), limits of detection and quantification (2.2 and 7.2 ng g−1, respectively) and repeatability (RSD <10%). Moreover, relative recoveries between 99 and 109% were obtained, showing matrix effects were negligible using deuterated THC (THC-D 3) as surrogate. This new approach was successfully applied to ten commercially-available cosmetic samples of different matrices, thus showing it is suitable for the analytical control of THC in cosmetic products. The proposed methodology overcomes some of the drawbacks of the previous works with the same purpose, such as the higher limits of detection, time-consuming procedures, and consumption of large volumes of organic solvents. [Display omitted] • A sensitive analytical method for determining THC in cosmetics is presented. • The method makes use of stir bar sorptive dispersive microextraction (SBSDME). • CoFe 2 O 4 -Strata-X™-RP composite is used as magnetic sorbent material. • Trace levels of THC in the low ng g−1 range can be determined by this method. • The method uses less solvents and require shorter analysis time compared to others. [ABSTRACT FROM AUTHOR]

[Display omitted] • An analytical method to determine three regulated fragrance ingredients in cosmetics. • Analytes are extracted by using SBSDME and analyzed by GC–MS. • The magnetic CoFe 2 O 4 @p(DVB- co -NVP) copolymer is used as efficient sorbent material. • Cosmetics of different matrix can be analyzed by this method. • Trace levels of the analytes can be determined by this method. In this work, a magnetic composite made by cobalt ferrite (CoFe 2 O 4) magnetic nanoparticles entrapped into a poly(divinylbenzene- co - N -vinylpyrrolidone) copolymer is used to determine recently prohibited and restricted fragrances (i.e., Lilial, Lyral, and methyl- N -methylanthranilate) in cosmetics. This hydrophilic-lipophilic balance type material was characterized by magnetism measurements, scanning electron microscopy, nitrogen adsorption–desorption isotherms, and thermogravimetric analysis. The proposed method is based on stir bar sorptive dispersive microextraction (SBSDME) followed by gas chromatography coupled to mass spectrometry (GC–MS). The main quantitative parameters involved in the SBSDME were optimized by using a Box-Behnken design, whereas the desorption solvent was optimized by using a Simplex-Centroid design. Under the optimized conditions, good analytical features were obtained, showing good linearity (at least up to 200 ng mL−1), enrichment factors from 18 to 26, method limits of detection in the low µg/g range (0.01–0.1 µg g−1), and good intra- and inter-day repeatability (relative standard deviations below 10 %). Matrix effects were negligible as long as no more than 0.1 and 0.25 g of fat- and water-soluble samples, respectively, were weighed and diluted to 25 mL. Finally, the proposed method was successfully applied to three commercial cosmetic samples of different formulation, and quantitative relative recovery values (76–108 %) were obtained by external calibration. This work expands the analytical potential of SBSDME to the use of new magnetic polymer-based sorbents. In addition, it contributes to the availability of methods to ensure the safety of cosmetic products through quality control by means of a green methodology. [ABSTRACT FROM AUTHOR]

A new and sensitive analytical method based on the recently developed approach termed stir bar-sorptive dispersive microextraction (SBSDME) using a magnetic CoFe 2 O 4 @SiO 2 –nylon 6 composite as sorbent material is presented for the extraction of hydrophilic organic compounds. The simultaneous determination of four hydrophilic UV filters in environmental water samples has been chosen as a model analytical application due to the increasing awareness regarding the occurrence of sunscreen residuals in natural waters. The developed SBSDME approach combines the principles and benefits of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE) but allows for lower extraction time and easier post-extraction treatment. Moreover, most importantly, it enables the use of new magnetic materials that affords higher versatility and can be tailored to the needs of the analysis. The main experimental parameters involved in the SBSDME process (i.e. composite amount, extraction time, pH, ionic strength, desorption solvent and desorption time) were evaluated to provide the best enrichment factors. Under the optimized conditions, the method was successfully validated showing good linearity, enrichment factors between 105 and 145 depending on the analyte, limits of detection and quantification in the low ng mL −1 range (1.6–2.9 ng mL −1 and 5.4–9.6 ng mL −1 , respectively) and good intra- and inter-day repeatability (RSD < 13%). The developed method was applied to the analysis of water samples of different origin (sea, river and swimming pool). Relative recovery values ranged between 90 and 115%, thus showing that the matrices under consideration do not affect the extraction process. [ABSTRACT FROM AUTHOR]

In this work, a new approach that combines the advantages of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE), i.e. stir bar sorptive–dispersive microextraction (SBSDµE), is employed as enrichment and clean-up technique for the sensitive determination of eight lipophilic UV filters in water samples. The extraction is accomplished using a neodymium stir bar magnetically coated with oleic acid-coated cobalt ferrite magnetic nanoparticles (MNPs) as sorbent material, which are detached and dispersed into the solution at high stirring rate. When stirring is stopped, MNPs are magnetically retrieved onto the stir bar, which is subjected to thermal desorption (TD) to release the analytes into the gas chromatography–mass spectrometry (GC–MS) system. The SBSDµE approach allows for lower extraction time than SBSE and easier post-extraction treatment than DSPE, while TD allows for an effective and solvent-free injection of the entire quantity of desorbed analytes into GC–MS, and thus achieving a high sensitivity. The main parameters involved in TD, as well as the extraction time, were evaluated. Under the optimized conditions, the method was successfully validated showing good linearity, limits of detection and quantification in the low ng L −1 range and good intra- and inter-day repeatability (RSD<12%). This accurate and sensitive analytical method was applied to the determination of trace amounts of UV filters in three bathing water samples (river, sea and swimming pool) with satisfactory relative recovery values (80–116%). [ABSTRACT FROM AUTHOR]

A novel microextraction technique combining the principles of stir bar sorptive extraction (SBSE) and dispersive micro-solid phase extraction (DμSPE) is presented. The main feature of the method is the use of a neodymium-core stirring bar physically coated with a hydrophobic magnetic nanosorbent. Depending on stirring speed, the magnetic sorbent either acts as a coating material to the stir bar, thus affording extraction alike SBSE, or as a dispersed nanosorbent medium for the collection and extraction of the target analytes, in close analogy to DμSPE. Once the stirring process is finished, the strong magnetic field of the stir bar prevails again and rapidly retrieves the dispersed MNPs. Alike SBSE, the stir bar is collected and the analytes are back-extracted by liquid desorption into an appropriate organic solvent, which is used for analysis. This enrichment technique is easy to prepare since it does not require special surface modification procedures, uses low volumes of non-toxic organic solvents and most importantly imbues SBSE with additional functionalities against a wide range of analytes (since nanosorbents with various coatings can be employed) while it affords additional merits to DμSPE in terms of extraction and post-extraction treatment. As proof-of-concept this new approach was applied to the determination of organic UV filters in seawater samples using oleic acid-coated cobalt ferrite (CoFe 2 O 4 @oleic acid) magnetic nanoparticles as sorbent material. The method showed good analytical features in terms of linearity, enrichment factors (11–148), limits of detection (low ng mL −1 ), intra- and inter-day repeatability (RSD < 11%) and relative recoveries (87–120%). [ABSTRACT FROM AUTHOR]

• A sensitive analytical method to determine PAHs in cosmetic samples is presented. • Trace levels of analytes can be determined by this method. • Analytes are extracted by using SBSDME and analyzed by GC-MS. • Small volumes of organic solvents and short analysis time are needed. • This work expands the potential of SBSDME to other analytes and sorbent phases. This work describes a sensitive and rapid analytical method for trace determination of polycyclic aromatic hydrocarbons (PAHs) in cosmetic samples. The proposed method is based on stir bar sorptive-dispersive microextraction (SBSDME). A magnetic composite made of CoFe 2 O 4 magnetic nanoparticles embedded into reduced graphene oxide sheets is used as sorbent phase. After the extraction, the target analytes are desorbed in toluene and then analyzed by gas chromatography-mass spectrometry (GC-MS). The main parameters involved in the extraction procedure (i.e., composite amount, extraction time and desorption time) were evaluated and optimized to provide the best extraction efficiency. The method was successfully validated under the selected conditions, showing a linear range of at least up to 125 ng mL−1, instrumental and method limits of detection from 0.02 to 2.50 ng mL−1 and from 0.15 to 24.22 ng g−1, respectively, and relative standard deviations (RSD) below 10 % for all the target analytes. Standard addition combined with internal standard calibration was employed for quantification. The proposed method was successfully applied to the analysis of ten PAHs in four cosmetic products of different matrix. Several analytes between 14 and 464 ng g−1 were found, some of them prohibited in cosmetic products. This work expands the analytical potential of SBSDME technique to other analytes and to the use of new sorbent phases, showing the great versatility of this approach depending on the characteristics of the analytes. [ABSTRACT FROM AUTHOR]

• Stir bar sorptive-dispersive microextraction (SBSDME) is used. • A magnetic nanoparticles–metal organic framework composite is employed as sorbent. • This sorbent allows a successfully enrichment of N -nitrosamines from cosmetics. • Trace levels of N -nitrosamines are determined in lipophilic and hydrophilic samples. A new analytical method based on the recently proposed stir bar sorptive-dispersive microextraction (SBSDME) technique has been developed to determine eight hazardous N -nitrosamines in cosmetic products. As previous step, a simple clean-up is carried out with hexane to remove those highly lipophilic compounds that disturb the SBSDME step. Subsequently, SBSDME is performed by using magnetic nanoparticles–metal organic framework composite, CoFe 2 O 4 /MIL-101(Fe), as sorbent to entrap the target analytes, which are later chemically desorbed and measured by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The experimental variables related to the SBSDME procedure were studied to achieve the highest analytical signal. Under the most favorable conditions, the proposed method was validated providing good linearity; enrichment factors up to 62 depending on the analyte; limits of detection from 3 to 13 µg kg−1; and good repeatability values (RSD < 17.0%). Finally, the method was successfully applied to cosmetic samples composed either of lipophilic or hydrophilic matrices. Quantitative relative recoveries (96–109%) were obtained by using standard addition calibration. The present work expands the applicability of the SBSDME technique, whereas its analytical features make it useful to carry out the quality control of cosmetic samples. [ABSTRACT FROM AUTHOR]