Stir Bar Sorptive Dispersive Microextraction Research Articles

Coupling Miniaturized Stir Bar Sorptive Dispersive Microextraction to Needle-Based Electrospray Ionization Emitters for Mass Spectrometry: Determination of Tetrahydrocannabinol in Human Saliva as a Proof of Concept.

Direct coupling of sample preparation with mass spectrometry (MS) can speed up analysis, enabling faster decision-making. In such combinations, where the analysis time is mainly defined by the extraction procedure, magnetic dispersive solid-phase extraction emerges as a relevant technique because of its rapid workflow. The dispersion and retrieval of the magnetic sorbent are typically uncoupled stages, thus reducing the potential simplicity. Stir bar sorptive dispersive microextraction (SBSDME) is a novel technique that integrates both stages into a single device. Its miniaturization (mSBSDME) makes it more portable and compatible with low-availability samples. This article reports the direct combination of mSBSDME and MS using a needle-based electrospray ionization (NESI) emitter as the interface. This combination is applied to determine tetrahydrocannabinol in saliva samples, a relevant societal problem if the global consumption rates of cannabis are considered. The coupling requires only the transference of the magnet (containing the sorbent and the isolated analyte) from the mSBSDME to the hub of a hypodermic needle, where the online elution occurs. The application of 5 kV on the needle forms an electrospray on its tip, transferring the ionized analyte to the MS inlet. The excellent performance of mSBSDME-NESI-MS/MS relies on the sensitivity (limits of detection as low as 2.25 ng mL-1), the precision (relative standard deviation lower than 15%), and the accuracy (relative recoveries ranged from 87 to 127%) obtained. According to the results, the mSBSDME-NESI-MS/MS technique promises faster and more efficient chemical analysis in MS-based applications.

A miniaturized stir bar sorptive dispersive microextraction method for the determination of bisphenols in follicular fluid using a magnetic covalent organic framework

BackgroundBisphenols, particularly bisphenol A (BPA), are the primary monomers used as additives in the manufacturing of many consumer products. The exposure to these compounds is related to endocrine-disrupting and reproductive effects, among others. For this reason, the development of analytical methods for their determination in biological matrixes is needed to monitor the population exposure to these compounds. Their quantification at ovarian level (i.e., follicular fluid) is interesting for the assessment of the bisphenol content to draw conclusions about infertility problems. However, the background does not meet all requirements by focusing mainly on BPA. ResultsIn this work, a miniaturized stir bar sorptive dispersive microextraction (mSBSDME) approach has been developed for the determination of BPA and eight analogues in follicular fluid. In the proposed method, the sample is previously cleaned-up using a zirconia-based solid-phase extraction cartridge, removing proteins and phospholipids, and then subjected to the mSBSDME for the preconcentration of the analytes. For this purpose, a magnetic covalent organic framework was used as sorbent. A Plackett-Burman design was applied to select the significant variables affecting the mSBSDME. Afterwards, the only significant variable (i.e., sorbent amount) was optimized. Under the optimized conditions, the proposed method was properly validated, and satisfactory analytical parameters in terms of linearity (up to 50 ng mL−1), enrichment factors (8.5–14.3), limits of detection in the low ng mL−1 range, and precision (relative standard deviations below 11.5 %) were obtained. Finally, the method was successfully applied to five samples, detecting BPA and other two analogues. SignificanceThis method expands the potential applicability of the mSBSDME to other low-availability complex matrixes, which would otherwise be difficult to analyze. Moreover, it offers a valuable tool for monitoring the female population's exposure to bisphenols with the final aim of evaluating if infertility problems of women might be associated to the exposure to these highly endocrine disrupting compounds.

Covalent organic framework in situ grown on Fe3O4 hollow microspheres for stir bar sorptive-dispersive microextraction of triazole pesticides.

Based on covalent organic framework (COF) 1,3,5-tris-(4-formylphenyl)benzene-benzidine (TFPB-BD) in situ grown on Fe3O4 hollow microspheres and combined with gas chromatography-flame thermionic detector, a rapid and simple stir bar sorptive-dispersive microextraction method was developed for the determination of five triazole pesticides (paclobutrazol, hexaconazole, flusilazole, propiconazole, and tebuconazole). The synthesized TFPB-BD/Fe3O4 microspheres were characterized by transmission electron microscope, vibrating sample magnetometer, and thermogravimetric analysis, which showed that the material has strong magnetism and higher load capacity of COF. Under optimal conditions, the extraction equilibrium could be achieved within 9min with detection limits of 0.17-1.48μg L-1 (S/N = 3) and a linear range of 5-1000μg L-1. The developed method was applied to the determination of trace triazole pesticides in apples, pears, and cabbages with recoveries from 81 to 117%.

The metal–organic framework PCN-250 for the extraction of endocrine disrupting compounds in human urine by stir bar sorptive dispersive microextraction

An analytical method based on stir bar sorptive dispersive microextraction (SBSDME), followed by liquid chromatography coupled to tandem mass spectrometry detection (LC-MS/MS), has been satisfactorily developed for the determination of twelve endocrine disrupting compounds (EDCs), bisphenols and benzophenones, in urine samples. The PCN-250(Fe2Mn) metal–organic framework (MOF) has been used as effective sorbent in the method, while later involving cobalt ferrite (CoFe2O4) magnetic nanoparticles to speed up the magnetic retrieval, without the need of preparing any complex composite. The extraction capacity of the PCN-250(Fe2Mn) and its compatibility with the CoFe2O4 magnetic nanoparticles were compared with other conventional MOFs (i.e., MIL-101(Fe)–NH2, CIM-80(Al), and UiO-66(Zr)) in order to select the most adequate sorbent. The quantitative parameters affecting the SBSDME process (i.e., sorbent amount, extraction and desorption times, and ionic strength) were optimized by using a Box-Behnken experimental design. Under the optimized conditions, the proposed method was properly validated, showing good linearity (at least up to 20 μg L−1), enrichment factors ranging from 9 to 125, limits of detection in the ng/L range (1.5 – 53 ng L−1), and good intra- and inter- day precision (relative standard deviations below 15 %). Matrix effects were observed for the direct urine analysis, but they were negligible when a 1:5 (v/v) dilution with ultrapure water was performed. Finally, the method was successfully applied to human urine samples from three volunteers, obtaining quantitative relative recoveries (82 – 118 %). This work exploits, for the first time, the high potential that PCN-250(Fe2Mn) exhibits when it is used as sorbent for microextraction purposes.

New challenges in sample preparation: Miniaturized stir bar sorptive dispersive microextraction as a high-throughput and feasible approach for low-availability sample preparation

The miniaturization of stir bar sorptive dispersive microextraction (mSBSDME) for the analysis of low-availability samples is presented. This new methodology is based on the principles of stir bar sorptive dispersive microextraction, but the amount of sorbent and, most importantly, the amount of sample are considerably reduced to a tiny amount and a few microliters, respectively. Thus, affordable 400-μL flat-base glass inserts and minute bar-shape neodymium magnets (3 mm length x 2 mm diameter) were used as extraction devices hold by a specifically designed multiextraction assembly, which comprises a high-rate stirring plate and a 3D-printed support to treat 15 samples simultaneously. This new approach allows a fast, affordable, portable, and high-throughput analysis of low-volume samples, expanding the potential of the technique. The same extraction device is used along the different stages, thus avoiding transfers, which reduces sample handling. Besides, the reduction in the sample, sorbent and organic solvent amounts allows a considerable decrease of the waste generation, and thus pursues a green sample preparation for bioanalysis. As a proof-of-concept of this new methodology, cortisone and cortisol were determined in human saliva using a composite material made of a reversed phase polymer (Strata™-X-RP) and CoFe2O4 magnetic nanoparticles. Liquid chromatography coupled to tandem mass spectrometry was used to measure both analytes obtaining good analytical features in terms of linearity (R2 > 0.997), method limits of detection and quantification (22.6 and 75.5 ng L−1 for cortisone, and 19.3 and 64.3 ng L−1 for cortisol, respectively), repeatability (RSD ≤11%) and relative recoveries (78–134%).

Entrapment of magnetic nanoparticles into poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer for the determination of prohibited and restricted fragrance ingredients in cosmetic products

In this work, a magnetic composite made by cobalt ferrite (CoFe2O4) 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.

Trace determination of tetrahydrocannabinol (THC) in cosmetic products by stir bar sorptive dispersive microextraction followed by liquid chromatography-tandem mass spectrometry

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 CoFe2O4 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-D3) 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.

Stir bar sorptive-dispersive microextraction by a poly(methacrylic acid-co-ethylene glycol dimethacrylate)-based magnetic sorbent for the determination of tricyclic antidepressants and their main active metabolites in human urine

A poly(methacrylic acid-co-ethylene glycol dimethacrylate)-based magnetic sorbent was used for the rapid and sensitive determination of tricyclic antidepressants and their main active metabolites in human urine. This material was characterized by magnetism measurements, zeta potential, scanning electron microscopy, nitrogen adsorption–desorption isotherms, and thermogravimetric analysis. The proposed analytical method is based on stir bar sorptive-dispersive microextraction (SBSDME) followed by liquid chromatography–tandem mass spectrometry. The main parameters involved in the extraction step were optimized by using the response surface methodology as a multivariate optimization method, whereas a univariate approach was employed to study the desorption parameters. Under the optimized conditions, the proposed method was properly validated showing good linearity (at least up to 50 ng mL−1) and enrichment factors (13–22), limits of detection and quantification in the low ng L−1 range (1.4–7.0 ng L−1), and good intra- and inter-day repeatability (relative standard deviations below 15%). Matrix effects were observed for the direct analysis of urine samples, but they were negligible when a 1:1 v/v dilution with deionized water was performed. Finally, the method was successfully applied to human urine samples from three volunteers, one of them consuming a prescribed drug for depression that tested positive for clomipramine and its main active metabolite. Quantitative relative recoveries (80–113%) were obtained by external calibration. The present work expands the applicability of the SBSDME to new analytes and new types of magnetic sorbents.Graphical abstract

MIL-101(Fe)-derived magnetic porous carbon as sorbent for stir bar sorptive-dispersive microextraction of sulfonamides.

Using MIL-101(Fe) as the source of carbon and Fe, a magnetic porous carbon (MPC) material with Fe3C nanoparticles encapsulated in porous carbon was prepared through one-pot pyrolysis under N2 atmosphere. With MPC as adsorption material, a stir bar sorptive-dispersive microextraction (SBSDME) method was proposed to extract and preconcentrate sulfonamides (SAs) prior to HPLC-DAD determination. To investigate their extraction ability, different MPC materials were prepared under different carbonization temperatures (600, 700, 800, 900, and 1000°C). The material prepared under 900°C (MPC-900) exhibited the highest extraction ability for SAs. The as-prepared MPC materials were also characterized by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, zeta potential, and other techniques. The main parameters that affect extraction were systematically studied. Under optimal conditions, favorable linearity (R2≥0.9938) and detection limits (0.02-0.04ngmL-1) of sulfonamides were obtained. The average recoveries for spiked milk and lake water samples ranged from 76.9 to 109% and from 75.4 to 118% with RSDs of 3.10-9.63% and 1.71-11.3%, respectively. Sulfameter and sulfisoxazole were detected in milk sample. Sulfisoxazole was detected in the lake water sample. The MPC-900 material demonstrated excellent reusability. It can be reused 24 times with peak areas having no obvious decline. The method can be applied to extract ultra-trace compounds in complex sample matrices. Schematic presentation of a stir bar sorptive-dispersive microextraction (SBSDME) by using magnetic porous carbon (MPC) composites as sorbent combined with high-performance liquid chromatography for sensitive analysis of sulfonamides in milk and lake water samples.

Polydopamine-coated magnetic nanoparticles for the determination of nitro musks in environmental water samples by stir bar sorptive-dispersive microextraction

Magnetic-based microextraction approaches have gained popularity in recent years due to the magnetic properties of the extraction phases allowing to handle them easier and more efficiently. This work describes a magnetic-based analytical method for the determination of the family of nitro musks in environmental water samples. These compounds have been of great concern due to their environmental impacts and potential health effects. The method is based on stir bar sorptive-dispersive microextraction (SBSDME) as extraction approach, prior to thermal desorption coupled to gas chromatography-mass spectrometry analysis (TD-GC-MS). For this purpose, polydopamine-coated cobalt ferrite magnetic nanoparticles (CoFe2O4@PDA) were used as extraction material. The main parameters involved in the extraction procedure (i.e., sorbent amount, extraction time and ionic strength) as well as in the thermal desorption step (i.e., temperature and desorption time) were evaluated in order to obtain the highest sensitivity. Under the selected conditions, the method showed good linearity, limits of detection and quantification in the low ng L−1 range, intra- and inter-day repeatability with RSD <15%, and high enrichment factors (178–640). Finally, the method was applied to four environmental water samples of different origin. Relative recovery values ranging from 91 to 120% highlighted that the matrices under consideration do not affect the extraction process. This work constitutes the first time in which nitro musks compounds were selectively extracted by taking advantage the high potential that magnetic-based microextraction techniques offer, specially SBSDME.

Fundamentals and applications of stir bar sorptive dispersive microextraction: A tutorial review

Current trends in sample preparation focus on the miniaturization of the process resulting in what is known as microextraction techniques. Among them stir bar sorptive dispersive microextraction (SBSDME) is one of the most recent techniques. It was presented a few years ago as a hybrid microextraction technique that combines the principles of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE). This novel technique introduces, into the sample solution, a bar-shaped magnet coated with a magnetic (nano)material, which is maintained on the surface by magnetism. Once stirring starts, the competitive action between magnetism and rotational force is exploited. At low rotational speed the (nano)material is retained on the magnet reminding SBSE, whereas at high sufficiently rotational speed the rotational force surpasses magnetism so that the magnetic (nano)material is dispersed into the sample solution as in DSPE. Upon halting rotation, the magnetic field prevails again and attracts the magnetic (nano)material containing the analytes back on the surface of the stirring bar. Finally, the extracted analytes are chemically or thermally desorbed before their measurement with the appropriate analytical instrument. When compared separately to SBSE and DSPE procedures, SBSDME affords, in a single approach, advantages such as lower extraction times than SBSE and easier extraction and post-extraction treatment than DSPE. The main purpose of this tutorial review is to describe the fundamentals and the experimental variables involved in this technique, as well as to compile and critically discuss the published papers concerning analytical methods based on the use of the SBSDME approach, analyzing its evolution and future prospects.

Evolution and current advances in sorbent-based microextraction configurations

This review overviews the main developments achieved in analytical sample preparation regarding the use of solid sorbents as extractants in different sorbent-based miniaturized, micro-scale and microextraction methods. Two main groups are proposed for the classification of the current approaches, based on their operational mode: micro-solid-phase extraction (µ-SPE) and solid-phase microextraction (SPME), while describing their respective main sub-modes: static- and dispersive-µ-SPE, and SPME with fibers and in tube SPME. Furthermore, other important sorbent-based microscale approaches (e.g., stir bar sorptive extraction, stir cake sorptive extraction, stir bar sorptive-dispersive microextraction, and thin film microextraction, among others) are also considered.

Sonodecoration of magnetic phosphonated-functionalized sporopollenin as a novel green nanocomposite for stir bar sorptive dispersive microextraction of melamine in milk and milk-based food products

The novel green magnetic phosphonated-functionalized sporopollenin nanocomposite (MPSP-nanocomposite) was synthetized and used for stir bar sorptive dispersive microextraction (SBSDME) of melamine in milk and milk-based food products. TEM, SEM-EDX, FT-IR, VSM techniques were applied for characterization of MPSP-nanocomposite. The influential parameters including pH, extraction time, stirring rate, elution solvent type and volume, sample volume, desorption time, and ionic strength were studied and at optimum conditions, the linear range of 1–500 (µg L−1), the LOD (S/N = 3) of 0.30 (µg L−1), and the LOQ (S/N = 10) of 0.95 (µg L−1) were achieved. The intra-day precision values (RSD (%), n = 7) of 3.5% for the melamine concentration of 25 (µg L−1). The relative recoveries of 95.8% to 99.6% were acquired for the real samples which confirmed that the proposed method could be successfully utilized in complex matrixes with high matrix effects.

Reduced graphene oxide-based magnetic composite for trace determination of polycyclic aromatic hydrocarbons in cosmetics by stir bar sorptive dispersive microextraction

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 CoFe2O4 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.

Decoration of Fe3O4@SiO2@ZnO as a high performance nanosorbent on a stir bar microextraction device for preconcentration and determination of cadmium in real water samples

In this work, a novel, fast and simple method that so called stir bar sorptive–dispersive microextraction (SBSDµE) applied for preconcentration and determination of trace amounts of Cd (II) ions in real water samples. For this purpose, Fe3O4@SiO2@ZnO core–shell microspheres were coated on a neodymium stir bar magnetically, and dispersed in the sample solution at high stirring rate, while adsorbing Cadmium target ions. The effective factors on extraction of Cd (II) (pH, stirring rate, salt effect and extraction time) were investigated and optimized using response surface methodology (RSM) as a powerful statistical technique. Under the optimal conditions, linear dynamic range (LDR) of SBSDµE method was 1–150 ng mL−1, the intra-day and inter-day relative standard deviations (RSD%) at 80 ng mL−1 concentration level were 3.7% and 8.4% (n = 5), respectively. The limit of detection (LOD) was 0.37 ng mL−1 and the limit of quantification (LOQ) was 1.23 ng mL−1. The proposed microextraction analytical method was successfully used for determination of ultra trace amounts of cadmium in some real water samples.

Stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles-metal organic framework composite: Determination of N-nitrosamines in cosmetic products

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, CoFe2O4/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.

Magnetic cellulose nanoparticles as sorbents for stir bar-sorptive dispersive microextraction of polychlorinated biphenyls in juice samples

Magnetic cellulose nanoparticles (MCNPs) were used for the first time as sorbents for stir bar-sorptive dispersive microextraction (SBSDME). The main experimental parameters involved in the SBSDME process that affect extraction (i.e. amount of MCNPs, ionic strength, pH, extraction and back-extraction time) were investigated. The method was applied to the determination of nine polychlorinated biphenyls (PCBs) in fruit juice samples by gas chromatography–mass spectrometry (GC-MS). Under the optimized conditions, a good linearity was obtained in a concentration range of 10–1000 ng mL−1 with determination coefficients over 0.9945. Limits of detection and quantification for all target PCBs were in the range 2.1–54 ng L−1 and 7.0–180 ng L−1, respectively. Intra-day precision ranged from 1.7% to 8.8% and inter-day precision from 3.4% to 9.3% RSD. The enrichment factors of the analytes were from 74.6 to 98.2. The MCNPs can be reused up to 5 times. The method was applied to commercial orange and pineapple juices (n = 5), where concentrations were below the limits of detection. Recoveries from 70.4 to 108.0% were obtained by applying the method for the analysis of spiked fruit juice samples at 1 and 2 ng mL−1 concentration levels. The use of cellulose makes this approach environmentally friendly and the magnetism of the resulting sorbent in conjunction with SBSDME provides ease of handling and saving of time.

A novel stir bar sorptive-dispersive microextraction in combination with magnetically modified graphene for isolation of seven pesticides from water samples

A new sample preparation technique: stir bar sorptive-dispersive microextraction (SBSDμE) with magnetically modified graphene (G-Fe3O4) as the sorbent was applied to isolation of multiclass seven pesticides (boscalid, chlorpyrifos, deltamethrin, dimethenamid-P, dimoxystrobin, metazachlor and tebuconazol) from spiked water samples. Selected experimental parameters were studied, and the optimized extraction conditions were as follows: 20 mg of the sorbent, sample pH 6, adsorption time - 12 min, addition of 1 g NaCl and 4.5 mL of acetone as the desorbing solvent. At the optimized conditions the developed extraction method was compared with magnetic solid phase extraction (MSPE). Extractions were performed in four replicates at three concentration levels of the pesticides. The average extraction yields of all the pesticides for the SBSDμE and MSPE methods were 20–75% (RSD 1–12%) and 22–82% (RSD 2–13%), respectively. Compared with the MSPE method the proposed SBSDμE approach is more quick and convenient in collecting of the sorbent, as well as more effective in mixing of larger volume samples.

Stir bar sorptive-dispersive microextraction for trace determination of triphenyl and diphenyl phosphate in urine of nail polish users

This work describes a new analytical method useful for monitoring the human exposure to the endocrine-disrupting plasticizer triphenyl phosphate (TPP) via nail polish use. The method allows trace determination of this parent compound and its main metabolite, namely diphenyl phosphate (DPP), in urine samples of nail polish users. The method is based on a novel microextraction technique termed stir bar sorptive-dispersive microextraction (SBSDME) using a magnetic composite made of CoFe2O4 magnetic nanoparticles embedded into a mixed-mode weak anion exchange polymer (Strata™-X-AW), followed by liquid chromatography-tandem mass spectrometry (LC–MS/MS). The main parameters involved in the extraction procedure were evaluated and optimized. Under the optimized conditions, the method was successfully validated showing good linearity (at least up to 100 ng mL−1) and enrichment factors (17 and 30), limits of detection and quantification in the low ng L−1 range (1.9–17.1 ng L−1 and 6.3–57.1 ng L−1, respectively) and good intra- and inter-day precision (RSD < 8%). Excellent recoveries (81–112 %) were achieved by using matrix-matched calibration for quantification. Finally, the method was applied to the determination of both the parent compound and the metabolite in human urine samples from volunteers who applied themselves a nail polish containing TPP. Detectable amounts of the parent compound were found just in the first urination, whereas quantifiable amounts of DPP were found in the low ng mL−1 range even 24 h after application of the nail polish, thus suggesting a rapid biotransformation and a low excretion, and showing DPP as excellent biomarker of human exposure to TPP. This work expands the analytical potential of the novel SBSDME, and the proposed methodology contributes to the study of the absorption/excretion levels of endocrine disruptors present in cosmetic products.

Expanding the application of stir bar sorptive-dispersive microextraction approach to solid matrices: Determination of ultraviolet filters in coastal sand samples

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 CoFe2O4@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.