Ultrasound-assisted Dispersive Solid-phase Extraction Research Articles

Are volatile methylsiloxanes in downcycled tire microplastics? Levels and human exposure estimation in synthetic turf football fields

Downcycled rubber, derived from end-of-life tires (ELTs), is frequently applied as crumb rubber (CR) as infill of synthetic turf in sports facilities. This practice has been questioned in recent years as numerous studies have reported the presence of potentially hazardous chemicals in this material. CR particles fall into the category of microplastics (MPs), making them possible vectors for emerging micropollutants. A preliminary study where volatile methylsiloxanes (VMSs) were found in CR originated the hypothesis that VMSs are present in this material worldwide. Consequently, the present work evaluates for the first time the levels and trends of seven VMSs in CR from synthetic turf football fields, while attempting to identify the main sources and impacts of these chemicals. A total of 135 CR samples and 12 other of alternative materials were analyzed, employing an ultrasound-assisted dispersive solid-phase extraction followed by gas chromatography–mass spectrometry (GC–MS), and the presence of VMSs was confirmed in all samples, in total concentrations ranging from 1.60 to 5089 ng.g−1. The levels were higher in commercial CR (before field application), a reflection of the use of VMS-containing additives in tire production and/or the degradation of silicone polymers employed in vehicles. The VMSs generally decreased over time on the turf, as expected given their volatile nature and the wearing of the material. Finally, the human exposure doses to VMSs in CR (by dermal absorption and ingestion) for people in contact with synthetic turf in football fields were negligible (maximum total exposure of 20.5 ng.kgBW−1.year−1) in comparison with the European Chemicals Agency (ECHA) reference doses: 1.35 × 109 ng.kgBW−1.year−1 for D4 and 1.83 × 109 ng.kgBW−1.year−1 for D5. Nevertheless, more knowledge on exposure through inhalation and the combined effects of all substances is necessary to provide further corroboration. This work proved the presence of VMSs in CR from ELTs, another family of chemical of concern to take into account when studying MPs as vectors of other contaminants.

Ultrasound-assisted dispersive solid-phase extraction for the preconcentration of dyes in water samples

In this research, the magnesium ferrite/zinc oxide (MgFe2O4/ZnO) nanocomposite has been utilized as an effective adsorbent in the ultrasound-assisted dispersive solid-phase extraction (USA-DSPE) coupled to a spectrophotometric method for preconcentration of methylene blue (MB) and safranin O (SO) dyes. X-Ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM) analyses were performed to characterize and confirm the properties of the synthesized MgFe2O4/ZnO nanocomposite. Box-Behnken design (BBD) based on response surface methodology (RSM) was utilized to optimize the variables. The results of this research showed that the maximum extraction efficiency was obtained at pH = 7, eluent volume of 140 µL, adsorbent amount of 1.53 mg, and ultrasonic time of 8 min. After optimization by RSM and using the Quadratic model, the extraction efficiency for MB and SO was 98.60% and 97.23%, respectively. The analysis of variance (ANOVA) showed that the data obtained from the experiment were consistent with the predicted model. Under optimal conditions, the calibration curve was linear in the range of 5–1000 µg/L (coefficient of determination of 0.9884) for MB and 10–1100 µg/L (coefficient of determination of 0.9973) for SO. The limit of detections (LOD) of the proposed method for MB and SO were determined as 1.5 µg/L and 3 µg/L, respectively. The relative standard deviations (RSD, n = 5) for MB and SO were obtained as 1.1% and 2.1%, respectively. The results of adsorbent recovery revealed that MgFe2O4/ZnO nanocomposite could be used several times without a significant adsorbent efficiency loss. Furthermore, the findings of interference studies revealed that the presence of different ions does not cause substantial interference with the extraction of dyes. The environmental water samples analysis showed that the extraction efficiency for dyes was in the range of 93.74–99.11%.

Magnesium ferrite as a dispersive solid-phase extraction sorbent for the determination of organic pollutants using spectrophotometry

This study aimed to determine of malachite green (MG) and auramine O (AO) dyes in different environmental water samples. For this purpose, MG and AO dyes were pre-concentrated by ultrasound-assisted dispersive solid-phase extraction (UA-DSPE) and measured by spectrophotometry. Magnesium ferrite (MgFO) was applied as a magnetic adsorbent in the UA-DSPE-UV/Vis method. The effect of different parameters on the dye extraction efficiency, including pH of the solution, sorbent mass, sample volume, ultrasound frequencies, irradiation time, and type and volume of eluent, were investigated. In addition, response surface methodology (RSM) approach-based central composite design (CCD) was used to design and optimize parameters affecting the process. Analysis of variance (ANOVA) results based on high F-values, low p-values, coefficient of determination (R2 > 0.99), and adjusted-R2 (R2adj > 0.99) revealed that the quadratic model was the best model for defining the interaction of the studied variables. The calibration curve, the limit of detection (LOD), and relative standard deviation (RSD, n = 5) for MG and AO dyes were 1–800 ng mL−1 and 3–1200 ng mL−1, 0.33 ng mL−1 and 1 ng mL−1, and 3.2% and 2.8%, respectively. The effect of some external species (including cations and anions) on the determination of MG and AO dye was investigated. The results revealed that adding different ions does not significantly interfere with determining MG and AO dyes. The reusability of the MgFO adsorbent showed that it could be reused for up to 7 cycles, maintaining its high efficiency in the extraction of MG and AO dyes. Moreover, the proposed method was used for the extraction of MG and AO dyes from different water samples. The obtained extraction efficiency was in the range of 95.37–99.54%.

Effect of Storage Temperature and Time on Biogenic Amines in Canned Seafood.

Biogenic amines in canned seafood are associated with food quality and human health. In this study, a total of nine biogenic amines (histamine (HIS), phenylethylamine (PHE), tyramine (TYM), putrescine (PUT), cadaverine (CAD), tryptamine (TRY), spermine (SPM), spermidine (SPD), and octopamine (OCT)) were used as standards. The biogenic amines of five canned seafood species (canned mud carp, canned sardine, canned mantis shrimp, canned scallop, and canned oyster) were investigated every three months for 12 months at different storage temperatures (4, 10, 25, and 30 °C). The biogenic amine contents were determined by the ultrasound-assisted dispersive solid-phase extraction method combined with reversed-phase high-performance liquid chromatography-photodiode array detection (UADSPE-RPLC-PDA). These results showed a detection rate of 100, 60, and 40% for HIS, PHE, PUT, and TYM; CAD, SPM, and SPD; OCT in all the samples, respectively. The contents of histamine and tyramine exceeded the recommended maximum limits (50 and 100 mg kg−1) in the canned mud carp and canned scallop when stored at 30 °C, indicating their potential health risks (p < 0.05). This result also indicates that low temperatures could inhibit the BAs content of canned seafood during storage. Overall, storage temperature and time can be used as the primary means to monitor and control the quality and safety of canned seafood.

Ultrasound assisted dispersive solid-phase extraction coupled with high-performance liquid chromatography-diode array detector for determination of caffeine and carbamazepine in environmental samples using exfoliated graphite/chitosan hydrogel

Ultrasound assisted dispersive solid-phase extraction coupled with high-performance liquid chromatography-diode array detector for determination of caffeine and carbamazepine in environmental samples using exfoliated graphite/chitosan hydrogel

Ultrasound-assisted dispersive solid phase extraction for promoting enrichment of ng L−1 level Hg2+ on ionic liquid coated magnetic materials

Herein, we investigated the enrichment behavior of inorganic mercury (Hg2+) on magnetic adsorbent with different ultrasound (US) energy field input. The enrichment rate of 0.10 μg L−1 mercury is increased by 4.5 times after US instead of stirring as dispersion mode. The input of higher frequency and power ultrasound can accelerate the enrichment of magnetic ionic liquid adsorbent and reduce the Hg2+ residue, importantly, which has not been reported. The positive correlation between cavitation effect and acoustic frequency and power in imaging experiments documents that US parameters are the key factors affecting the magnetic solid phase extraction. In addition, in-situ desorption and detection of adsorbate and recovery of adsorbent can be realized by slurry vapor generation (SVG) technology. The recovery of Hg2+ in four cycles is more than 90%, which indicates that the structure and properties of the material are not affected by the application of US. Hence, the degradation of adsorption properties caused by agglomeration of magnetic materials can be improved by introducing dispersion methods such as US. At the same time, 95% enrichment efficiency and 0.01–1.0 μg L−1 linear calibration range corresponding to 150 mL sample documents that magnetic ionic liquid adsorbent combined with US and sensitive spectral detector can meet the needs of ng L−1 level Hg2+ analysis in natural water samples.

Synthesis and Characterization of Poly(pyrrole-1-carboxylic acid) for Preconcentration and Determination of Rare Earth Elements and Heavy Metals in Water Matrices.

Pyrrole was N-functionalized with solid carbon dioxide followed by chemical polymerization to create a new air-stable, granular, and water-insoluble sorbent, poly(pyrrole-1-carboxylic acid) (PPy-CO2). PPy-CO2 exhibited enhanced affinity for the sorption of metal ions compared to unfunctionalized PPy due to the incorporation of carboxylate functional groups directly onto the polymer backbone. As a freestanding sorbent material, immobilization to an additional solid support is not needed. Sorption, and therefore preconcentration, occurs simultaneously to achieve efficient removal and recovery of metal ions by a pH-dependent sorption-desorption mechanism. PPy-CO2 was evaluated on the analytical scale for the solid-phase extraction of a range of metal ions and found to efficiently preconcentrate rare earth elements (REEs), Th, and heavy metals (Cr, Fe, Cd, and Pb), which allowed quantitation by inductively coupled plasma mass spectrometry (ICP-MS). The impact of sorption parameters, such as solution pH, amount of sorbent, and sorption time, and the effect of desorption flow rate for recovery were investigated and optimized using ultrasound-assisted dispersive solid-phase extraction (UAD-SPE) with ICP-MS analysis. Maximum efficiency for sorption and recovery of most metal ions was achieved at a solution pH of 6.0, 10 mg of sorbent, a sorption time of 5 min, and desorption conditions of 1 mL of 2 M nitric acid applied at a flow rate of 0.25 mL min-1. Detection limits for REEs and Th ranged from 0.2-3.4 ng L-1 for REEs and Th and 0.9-5.7 ng L-1 for heavy metals. Linear ranges from 0.1-1000 μg L-1 for REEs and 0.1-500 μg L-1 for heavy metals and Th were also observed. PPy-CO2 successfully preconcentrated and facilitated the determination of the targeted metal ions in water matrices of varying complexity, including tap water, well water, river water, and produced water samples. These results indicate the potential application of PPy-CO2 for larger-scale recovery and removal of valuable or hazardous metal ions.

Multi-ion imprinted polymers (MIIPs) for simultaneous extraction and preconcentration of Sb(III), Te(IV), Pb(II) and Cd(II) ions from drinking water sources

Simultaneous extraction and preconcentration of several potentially toxic metal ions have received great attention because of their toxicological effects on aquatic life and human beings. Multi-ion imprinted polymers (MIIP) have proved to be promising adsorbents with excellent specific recognition performance than single-ion imprinted polymer. Therefore, in this study, the MIIP strategy was employed for simultaneous extraction and enrichment of Sb(III), Cd(II), Pb(II) and Te(IV) ions from drinking water sources. MIIPs was used as a sorbent material in ultrasound-assisted dispersive solid phase extraction combined with inductively coupled plasma optical emission spectrometry (UA-DSPE/ICP-OES). The experimental parameters that affect the extraction efficiency and recovery of Sb(III), Cd(II), Pb(II) and Te(IV) were investigated using response surface methodology. Under optimum conditions, the enhancement factors, linear range, limit of detection (LOD) and limit of quantification (LOQ) were 37.7–51.1, 0.04–100 µg L-1, 0.011–0.28 µg L-1, 0.037–093 µg L-1, respectively. The intra-day (n = 10) and inter-day (n = 5) precision expressed as relative standard deviations (%RSDs,) were 3% and 5%, respectively. The proposed UA-DSPE/ICP-OES method was applied for preconcentration and determination of the trace metal ions in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95% to 99.3%.

Ultrasound-assisted dispersive solid-phase extraction combined with reversed-phase high-performance liquid chromatography-photodiode array detection for the determination of nine biogenic amines in canned seafood

This work describes an ultrasound-assisted dispersive solid-phase extraction method combined with reversed-phase high-performance liquid chromatography-photodiode array detection (UADSPE-RPLC-PDA) for the determination of nine common biogenic amines (BAs) in canned seafood. The pretreatment extraction solvent, ultrasonic treatment duration, and derivatization conditions were optimized. The method was validated on the basis of the limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy and successfully applied to analyze four canned fish, two canned shrimp and four canned shellfish samples. LODs of 0.08–0.25 mg kg−1 were achieved, and the correlation coefficient of determination was 0.9994–0.9997. The method had high precision and accuracy, with relative standard deviations (RSDs) and recoveries of 0.44 to 6.83% and 72.57 to 99.74%, respectively, suggesting the effectiveness of ultrasound-assisted extraction at increasing the solubility of the target analytes in the solvent system and the feasibility of UADSPE-RPLC-PDA for determining trace BAs in canned seafood.

Rapid ultrasound-assisted microextraction of atorvastatin in the sample of blood plasma by nickel metal organic modified with alumina nanoparticles.

In the present work, nickel-1,4-benzenedioxyacetic acid was synthesized as a rod-like metal organic material and then modified with alumina nanoparticles to synthesize nickel metal organic modified-Al2 O3 nanoparticles. The material was found as an efficient sorbent for the enrichment of atorvastatin in human blood plasma. After the extraction of the sample of plasma by ultrasound-assisted dispersive solid phase extraction, high performance liquid chromatography-ultraviolet was used to determine the quantitatively pre-concentrated interest analyte. The conditions for optimum extraction were achieved by the optimization of the volume of eluent, dosage of the sorbent, and time of sonication. Solution pH of 7.0, 250 μL of ethanol, 45mg of the sorbent, and 10min of sonication time were the conditions for extracting the atorvastatin maximum recovery of higher than 97.0%. By using desirability function for the optimization of the process, the present method showed a response that was linear ranging from 0.2 to 800ng/mL with regression coefficient of 0.999 in the plasma of human blood with a satisfactory detection limit of 0.05ng/mL, while the precision of interday for the current method was found to be<5%. It can be concluded that dispersive solid phase extraction method is effective for the extraction of atorvastatin from human plasma samples (97.4-102%) due to its easy operation, simplicity, repeatability, and reliability.

Ultrasound-assisted dispersive-filter extraction coupled with high-performance liquid chromatography: A rapid miniaturized method for the determination of phenylurea pesticides in vegetables and fruits

Due to the excessive use of pesticides, which presents a threat to public health, large quantities of vegetables and fruits need to be analyzed. Herein, a rapid, low-cost, miniaturized ultrasound-assisted dispersive-filter extraction (UADFE), coupled with high-performance liquid chromatography (HPLC) was developed for the first time to determine phenylurea pesticides in vegetables and fruits. The UADFE method achieved rapid extraction through ultrasound-assisted dispersive solid-phase extraction (DSPE) mode, rapid separation through filter solid-phase extraction (FSPE) mode, and rapid elution through quickly switching between DSPE and FSPE mode. After optimization of extraction parameters of UADFE, there was only 2.0 mg adsorbent dosage, 1.0 mL sample volume, and 8–10 min operation time, which significantly reduced the adsorbent dosage and operation time, and was superior to common sample preparation methods (solid-phase extraction, DSPE, etc.). Under the optimized condition, the UADFE-HPLC method showed good linearity (0.0100–2.50 μg/g, r ≥ 0.9995), accuracy (86.6–116.9%), precision (5.3–7.1%), and sensitivity (LOQs: 3.35–4.17 ng/g). Applying these advantages, the proposed method was found to be successful in determining phenylurea pesticides in various vegetables and fruits, demonstrating its ability to ensure food safety and assess potential risks of vegetables and fruits.

A novel approach for fast and simple determination pyrrolizidine alkaloids in herbs by ultrasound-assisted dispersive solid phase extraction method coupled to liquid chromatography–tandem mass spectrometry

Pyrrolizidine alkaloids (PAs) are secondary plant metabolites witch can contaminate food, especially herbs. Due to the fact that alkaloids have a strong adverse effect on human health, it is necessary to use sensitive and selective detection methods. In present study a modified method based on LC–MS/MS was developed and validated for the simultaneous determination of thirty pyrrolizidine alkaloids and their corresponding N-oxides (PANOs) in herbs samples. Sample extraction was based on ultrasound-assisted dispersive solid phase extraction and clean-up using graphene. Method validation showed that the proposed method hold good recoveries (61–128 %) for PAs/PANOs with RSD <15 %. Limits of quantification has been set at 1 μg kg−1 level for all targeted alkaloids. The optimized method yielded a small matrix effect (-20–20 %) for most PAs/PANOs. The uncertainty associated with the analytical method was not higher than 38 %. The method is operationally simple, time-saving, and can be applied to the analysis of real herb samples.

A mesoporous nanosorbent composed of silica, graphene, and palladium (II) for ultrasound-assisted dispersive solid-phase extraction of organophosphorus pesticides prior to their quantitation by ion mobility spectrometry.

A new ultrasonic-assisted dispersive solid-phase extraction method using mesoporous nanosorbent composed of silica, graphene, and palladium (II) (M S/G@-SH@Pd (II)), coupled with corona discharge ion mobility spectrometry, was developed for trace determination of organophosphorus pesticides. Initially, the M S/G@-SH@Pd (II) nanosorbent was synthesized and characterized. Then, the nanosorbent was used for the sorption and extraction of organophosphorus pesticides. Under the optimized conditions (pH = 7.0, 15 mgof sorbent, 3 minextraction time, ethanol asdesorption agent, 3 mincentrifuge time), the proposed technique provided good linearity (R2 > 0.994), repeatability (RSD < 4.6%), low limits of detection (0.15-0.30ngmL-1), excellent preconcentration factor (PF = 472-478), and high recoveries (93-94%). Themethod was applied tothe determination of organophosphorus pesticides in real water samples. The sorbent was reused in 5 cycles without any considerable loss of activity. Graphical abstract Schematic presentation of design and synthesis of mesoporous nanosorbent composed of silica, graphene, and palladium (II) for ultrasound-assisted dispersive solid-phase extraction of organophosphorus pesticides prior to their quantitation by ion mobility spectrometry.

Ultrasound assisted dispersive solid phase extraction of triazole fungicides by using an N-heterocyclic carbene copper complex supported on ionic liquid-modified graphene oxide as a sorbent.

An ultrasound-assisted method is described for dispersive solid phase extraction of trace levels of triazole fungicides. A sorbent was prepared from an N-heterocyclic carbene copper complex that was supported on ionic liquid-modified graphene oxide. The sorbent was characterized by scanning electron microscopy, transmission electron microscopy, Raman and FT-IR spectroscopy, energy-dispersive X-ray spectroscopy and elemental mapping. The capability of sorption and extraction is mainly based on complexation with Cu (I) ions. The variables affecting extraction were optimized. Following desorption with ethanol, the fungicides were quantified by corona discharge ion mobility spectrometry. Under optimized conditions (solution pH value: 7.0; amount of sorbent: 10mg; extraction time: 3min; desorption agent: ethanol), the technique provides good linearity (>0.994), repeatability (RSD < 4.1%), low limits of detection (0.18ng.mL-1), excellent preconcentration factors (468-476) and high recoveries from spiked environmental water samples (92-94%). The sorbent can be reused over five cycles without significant loss of its activity. Graphical abstract Schematic presentation of design and synthesis of the N-heterocyclic carbene copper complex supported on ionic liquid-modified graphene oxide as a sorbent for triazole fungicides and its application in ultrasound-assisted dispersive solid phase extraction with ion mobility spectrometric detection.

Ultrasound-assisted dispersive solid phase extraction based on Fe3O4/reduced graphene oxide nanocomposites for the determination of 4-tert octylphenol and atrazine by gas chromatography–mass spectrometry

A magnetic Fe3O4/reduced graphene oxide composite was synthesized by a one-step chemical coprecipitation method and characterized by different methods. The synthesized magnetic composite was used as magnetic sorbent in dispersive solid phase extraction process for preconcentration of 4-tert octylphenol and atrazine. The experimental variables in dispersive solid phase extraction were optimized based on two strategies: one-factor-at-a-time for mixing type and buffer pH; Box Behnken design for sorbent amount, mixing period, eluent volume and buffer volume. Analysis of variance study for proposed model resulted to high determination coefficient (R2) of 0.957 and adjusted-R2 of 0.929 indicating a good adjustment of regression model with observed values. Under the optimum extraction conditions, the determination of analytes was carried out by a gas chromatography–mass spectrometry system. The limits of detection and quantification values under the optimum conditions were found to be 1.23 and 4.10 ng mL−1 for 4-tert octylphenol and 6.81 and 22.71 ng mL−1 for atrazine, respectively. The low relative standard deviation (≤ 6.2%) indicated good repeatability and satisfactory percent recovery values (96.3–112.6%) demonstrated the applicability of proposed method to tap water, river water and waste water samples.

Determination of polybrominated diphenyl ethers (PBDEs) in dust samples collected in air conditioning filters of different usage – method development

This study presents the results of studies aimed at the development of an analytical procedure for separation, identification, and determination of PBDEs compounds in dust samples collected from automotive cabin air filters and samples collected from filters installed as part of the air purification system in academic facilities. Ultrasound-assisted dispersive solid phase extraction (UA-dSPE) was found to perform better in terms of extract purification than the conventional SPE technique. GC-EIMS was used for final determination of analytes.The concentrations of PBDEs in car filters ranged from < LOD to 688 ng/g while from < LOD to 247 ng/g in dust from air conditioning filters. BDE-47 and BDE-100 were reported the dominating congeners. The estimated exposure to PBDEs via ingestion of dust from car filters varied from 0.00022 to 0.012 ng/day in toddlers and from 0.000036 to 0.0029 ng/day in adults; dust from air conditioning filters: from 0.017 to 0.25 ng/day in toddlers and from 0.0029 to 0.042 ng/day.In addition, an attempt was made at extracting PBDEs from a dust samples using the matrix solid-phase dispersion (MSPD) technique as a promising alternative to conventional SPE separations.

Hydrophilic Multitemplate Molecularly Imprinted Biopolymers Based on a Green Synthesis Strategy for Determination of B-Family Vitamins.

A novel green synthesis strategy was proposed for preparation of multitemplate molecularly imprinted biopolymers (mt-MIBP) in aqueous media with less consumption of organic solvents, which were subsequently used as sorbents of ultrasound-assisted dispersive solid-phase extraction (d-SPE) for simultaneous recognition and efficient separation of B-family vitamins in juice samples, followed by high performance liquid chromatography (HPLC) determination. The obtained mt-MIBP was fully characterized by SEM, FT-IR, TEM, and BET. It offered high binding capacity, good selectivity, and fast dynamics toward all the templates. Involved parameters in the d-SPE efficiency such as mt-MIBP mass, sonication time, and eluting/washing solvents' types and volumes were concurrently investigated by central composite design with rapidity and reliability. Under the optimum conditions, the developed mt-MIBP-d-SPE-HPLC method exhibited wide linear range, low limits of detection and quantification (LOQs) within 1.2-5.5 μg L-1 and 4.0-18.4 μg L-1, respectively, and appropriate repeatability (relative standard deviation values below 4.2%, n = 4). The high selectivity of this method makes it suitable for successful monitoring of vitamins in juice samples with satisfactory recoveries of 75.8-92.7%, 81.1-92.5%, and 84.7-93.8% for vitamins riboflavin (B2), nicotinamide (B3), and pyridoxine (B6), respectively. The present study implied highly promising perspectives of water-compatible eco-friendly mt-MIBP for highly effective multiresidue analysis in complicated matrixes.

Ultrasound-assisted dispersive solid phase extraction of cadmium(II) and lead(II) using a hybrid nanoadsorbent composed of graphene and the zeolite clinoptilolite

We describe a hybrid nanoadsorbent prepared by depositing graphene on the zeolite clinoptilolite by chemical vapor deposition. The resulting sorbent is well suited for the preconcentration of lead(II) and cadmium(II) by ultrasound-assisted dispersive micro solid–phase extraction. An extraction unit has been designed and manufactured that facilitates handling of small sample volumes. The effects of sample pH, amount of sorbent, concentration and volume of elution and time of ultrasonic bath were investigated. The nanoadsorbent was characterized by scanning electron microscopy, X-ray diffraction and energy dispersive X-ray microanalysis, all of which revealed the high surface area of the graphene sheets on the clinoptilolite. The extraction recoveries when using the new nanoadsorbent are 97 % (as opposed to a mere 10 % in case of clinoptilolite only). It is assumed that the graphene sheets located around the porous structure of clinoptilolite are acting as a barrier against macromolecules potentially existing in the sample matrices. The method was applied to the determination of lead and cadmium in water and human serum samples by electrothermal atomic absorption spectrometry. The detection limits were as low as 70 and 4 ng L−1 for Pb(II) and Cd(II), respectively. The accuracy of the method was underpinned by correct analysis of a standard reference material (SRM: 203105 Seronorm Trace Elements Serum L-2). New nanoadsorbent, graphene/ clinoptilolite hybrid, was prepared which is suitable for separating and preconcentrating the metal ions from biological samples. In the propose method, the synthesized G/CL nanoadsorbent was used in ultrasound- assisted dispersive micro solid phase extraction method with applying the new designed extraction unit.

Determination of Aflatoxin M1 in Milk Powder by Ultrasonic-Assisted Extraction and Dispersive Solid-Phase Clean-up.

This work describes the application of ultrasound-assisted dispersive solid-phase extraction (UA-DSPE) as a sample preparation approach for aflatoxin M1 (AFM1) and also its subsequent determination by HPLC-fluorescence detection. A Box-Behnken design in combination with response surface methodology was implemented to determine the variables affecting the extraction procedure. The effects of different variables, including type and quantity of clean-up phase, ultrasonication time, ultrasonication temperature, nature and volume of the leaching solvent, were investigated in the optimization study. Primary secondary amine (PSA) and acetonitrile were selected as the clean-up phase and the leaching solvent, respectively. The obtained optimized values were 30 mg of PSA, 10 min ultrasonication time, 32°C ultrasonication temperature and 10 mL of acetonitrile. Under the optimal conditions, the limit of detection and limit of quantification were 0.0012 and 0.0045 µg kg(-1), respectively. The recoveries of the UA-DSPE procedure ranged from 80 to 92%, with relative standard deviations lower than 10% in all cases. Eventually, this method was successfully applied to the extraction of AFM1 in milk powder samples.