Solid-phase Extraction Material Research Articles

Preparation and Heavy Metal Ions Chelating Properties of Multifunctional Polymer-Grafted Silica Hybrid Materials

In this research work, novel hybrid materials based on multifunctional polymers and silica were developed and investigated in view of possible employment as sorbents for removal of heavy metal ions from water in presence of various ions. Organic-inorganic hybrid materials were prepared by covalent bonding of vinyl-terminated polyamidoamine (PAA) onto aminated silica particles. Two series of polyamidoamine-grafted silica, differing in the PAA chemical structure, were synthesized, and their heavy metal ions chelating properties were investigated. Column adsorption procedure for Cu, Zn, and Ni in aqueous solution was successfully established. Moreover, the adsorption behaviour of the materials was evaluated in different ionic strength solutions as well as in distilled and natural water. Organic-inorganic hybrid materials exhibited excellent chelating properties and selectivity for different metal ions. The hybrid columns showed exceptional eluting and regenerating property using diluted hydrochloric acid solution as eluent. In particular, the hybrid materials containing more carboxy groups possessed superior adsorption ability, reusability, and stability. The consecutive adsorption-desorption experiments exhibited that this material could be reused more than 20 cycles without almost any loss of adsorption capability. These new organic-inorganic sorbents appear very promising as an effective solid-phase extraction material for the selective preconcentration or removing of heavy metal ions from the environment.

Determination of carbonyls in ambient PM2.5 by coupling dummy template imprinting technology and high performance liquid chromatography

The determination of ambient carbonyls by the derivative method inevitably leads to the introduction of extra 2,4-dinitrophenylhydrazine (2,4-DNPH) into the sample solution. Traditional solid phase extraction (SPE) materials cannot remove this interference. To address this issue, a selective molecularly imprinted solid phase extraction (MISPE) column was prepared. With 2,4-dinitroaniline (2,4-DNAN) as the dummy template, MISPE could eliminate the excessive derivative agent (2,4-DNPH) in the air samples. Consequently, the sample could be concentrated effectively while the sensitivity increased greatly. By coupling MISPE and high performance liquid chromatography (HPLC), the developed method was used to study the concentration and source of 14 carbonyls of PM2.5 during spring in Guangzhou Higher Education Mega Center. Results showed that the total concentration of carbonyls increased with the level of air pollution. Particularly, the content of isovaleraldehyde increased sharply to account for 21% of the 14 total carbonyls in the haze days. Moreover, a high positive correlation between isovaleraldehyde and propionaldehyde was found either in normal days or haze days. From the correlation analysis, it was shown that anthropogenic emissions together with photochemical reaction had contributed to the abnormally high levels of carbonyls in ambient PM2.5 in the haze days. This aspect should be further investigated.

Application of a novel diol-based porous organic polymer to the determination of trace-level tetracyclines in water

A novel diol-based porous organic polymer (NTdiol-POP) was used as a new solid phase extraction material to improve extraction efficiency of trace tetracyclines in water before HPLC-MS/MS analysis.

Hollow porous dummy molecularly imprinted polymer as a sorbent of solid-phase extraction combined with accelerated solvent extraction for determination of eight bisphenols in plastic products

In this study, a highly selective and binding hollow porous dummy molecularly imprinted polymer (HPDMIP) was prepared for the separation and determination of bisphenols (BPs) in plastic products using bisphenol AF (BPAF) as dummy template, 4-vinylpyridine as the functional monomer, and MCM-48 as sacrificial support. HPDMIP was characterized by FT-IR spectroscopy, scanning electron microscope, nitrogen adsorption experiment and thermo-gravimetric analysis. Adsorption and selectivity experiments revealed that HPDMIP had a superior adsorption capacity and fast binding kinetics for recognizing BPs. Therefore, a perfect method using HPDMIP as a sorbent material for solid-phase extraction (SPE) was developed, which achieved specific adsorption and enrichment of trace BPs in complex samples. In addition, accelerated solvent extraction (ASE) along with SPE were used as pretreatment method for extracting and concentrating the BPs, and the BPs were determined based on UHPLC–MS/MS. The conditions of ASE and SPE were thoroughly investigated and optimized. Meanwhile, in the ASE proceeding, a Box-Behnken design was applied. Under the optimal conditions, each target analyte had a good linearity between 0.1 and 50 μg·L−1 with regression coefficients in the range of 0.9967–0.9995. Limits of detection and quantification varied from 0.02 to 0.6 μg·L−1 and 0.05 to 2 μg·L−1, respectively. The spiking recoveries between 50.8 and 138.31% for samples spiked at different concentration levels were achieved. The developed method eliminated the effect of template leakage on quantitative analysis and could be applied to extraction and analysis of BPs in different samples with satisfactory results, which provided a useful tool for further studying the BPs in complex samples.

Green construction of Fe3O4@GC submicrocubes for highly sensitive magnetic dispersive solid-phase extraction of five phthalate esters in beverages and plastic bottles.

A well-designed core-shelled Fe3O4@graphitic carbon (Fe3O4@GC) submicrocube was in situ constructed in a simple, relatively green and eco-friendly ways basing on one-step pyrolysis of low-cost waste napkins-coated Fe2O3 submicrocubes. The Fe3O4@GC submicrocubes showed unique architectures where in situ generated thin graphitic carbon layer wrapped on the surface of Fe3O4, resulting in excellent affinity to five phthalate esters (PAEs), good reusability and rapid magnetic separation, therefore were employed as magnetic dispersive solid-phase extraction material combined with HPLC to simultaneously detect five trace PAEs in beverages and plastic bottles. Under optimized conditions, recoveries (80.0%-112.8%), precision (RSDs ≤ 8.8%), and limits of detection (LODs) for beverages (0.09-0.28 μg L-1) and plastic bottles (0.01-0.03 μg g-1) were obtained. This work not only establishes an effective method for simultaneous determination of five PAEs, but also opens up a new strategy to design/construct magnetic graphitic carbon-encapsulated core-shell materials using low-cost/recyclable napkins as carbon source.

Recent Developments in Selective Materials for Solid Phase Extraction

The success of any analytical method depends largely on the sample preparation technique which is usually employed for the extraction and pre-concentration of the target analyte from a sample matrix. In this context, solid-phase extraction has been greatly explored by various researchers in many scientific fields including environmental analysis of pollutants, as well as analysis of food and biological samples. One of the solid-phase extraction drawbacks observed over the years is its inability to selectively extract the target analytes from the sample matrix, which could have a consequence of prolonging the analysis times and have negative effect on the analytical data. In this paper, recent trends starting from the work published in 2014–2018 in selective solid-phase extraction are critically reviewed while interesting studies prior to 2014 are mentioned. Solid-phase extraction sorbents that have been revealed in greater extent in literature to offer better selectivity are molecularly imprinted polymers and nano sorbents. Other sorbents reviewed in this work include composite materials which are sometimes designed for improving the adsorption capacity as well as selectivity. Mixed-mode ion-exchange polymers categorized as class selective sorbents have also been reviewed and recent applications are cited. Moreover, a broad discussion on miniaturization, new inventions and future of selective solid-phase extraction utilizing different sorbents in various sample matrices is outlined.

Determination of ultratrace tellurium in water by hydride generation atomic absorption spectrometry using online separation and pre-concentration with nano-TiO2 microcolumn

Silica gel loaded with nano-TiO2 was used as solid phase extraction materials to prepare a microcolumn for the online enrichment of trace tellurium in water and then determined by hydride generation atomic absorption spectrometry (HG-AAS). The effect of pH and the flow rate of sample on the extraction efficiency, NaOH concentration on the elution efficiency and other factors influencing hydride generation efficiency of tellurium were carefully investigated. Under the optimized experimental conditions, the sensitivity and the limit of detection (LOD) of this method were 0.009 L/μg and 0.04 μg L−1, respectively, which were 1000 and 850 times better than those obtained by the traditional flame atomic absorption spectrometry (FAAS); and the LOD for tellurium was improved by 45 times in this work, when compared with that by hydride generation-atomic absorption spectrometry (HG-AAS) without any separation and pre-concentration. This method was found to be interference-free of transitional metal ions, probably because of the surface of the nano-TiO2 was positively charged under acidic conditions, and it does not adsorb their cations. This method was successfully applied to the determination of tellurium in water samples.

Preparation of Imazethapyr Surface Molecularly Imprinted Polymers for Its Selective Recognition of Imazethapyr in Soil Samples.

A novel strategy based on imazethapyr (IM) molecular-imprinting polymers (MIPs) grafted onto the surface of chloromethylation polystyrene resin via surface-initiated atom transfer radical polymerization (SI-ATRP) for specific recognition and sensitive determination of trace imazethapyr in soil samples was developed. The SI-ATRP was performed by using methanol-water (4 : 1, v/v) as the solvent, acrylamide as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the cross-linker, imazethapyr as the template, and CuBr/2,2′-bipyridine as the catalyst. The resulting MIPs were characterized by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Then, the binding selectivity, adsorption capacity, and reusability of the MIPs were evaluated. The results indicated that the prepared MIPs exhibited specific recognition and high selectivity for imazethapyr. The MIPs were further used as solid-phase extraction (SPE) materials coupled with high-performance liquid chromatography (HPLC) for selective extraction and detection of trace imazethapyr from soil samples. The results showed that good linearity was observed in the range of 0.10–5.00 μg/mL, with a correlation coefficient of 0.9995. The limit of detection (LOD) of this method was 15 ng/g, and the extraction recoveries of imazethapyr from real samples were in the range of 91.1–97.5%, which proved applicable for analysis of trace imazethapyr in soils. This work proposed a sensitive, rapid, and convenient approach for determination of trace imazethapyr in soil samples.

Extraction Properties of New Polymeric Sorbents Applied to Wine.

Polymeric sorbents are frequently used in wine, either as solid phase extraction materials for isolation of analytes or as sorptive materials for removal of undesirable compounds (amelioration). Six new polymeric sorbents were produced thermally or in a microwave from various ratios of methacrylic acid, acrylic acid, and 4-vinylbenzoic acid as hydrophilic monomers, together with ethylene glycol dimethacrylate as cross-linker, using different porogen solvents. The relationship between physicochemical properties (pore size, surface area, and polarity) of the sorbents and their sorption properties for compounds in wine was investigated and compared to four commercially available sorbents. With some similarities to their commercial counterparts depending on hydrophobic and hydrophilic characteristics, the six new sorbents showed specificity toward different groups of compounds (e.g., volatiles and phenolics) and could be applied for targeted purposes. The results provide insight into the selection and utilization of new polymeric materials for extraction of components from wine.

Preparation and application of a restricted access material with hybrid poly(glycerol mono-methacrylate) and cross-linked bovine serum albumin as hydrophilic out layers for directly on-line high performance liquid chromatography analysis of enrofloxacin and gatifloxacin in milk samples

A novel restricted access material (RAM) was prepared through combination of hydrophilic polymer poly(glycerol mono-methacrylate) and cross-linking bovine serum albumin (BSA) for direct biological analysis. In the material preparation, the poly(styrene-co-divinylbenzene) and poly(glycerol mono-methacrylate) were grafted on silica successively by atom transfer radical polymerization. Then the BSA was adsorbed on the material and cross-linked through an in-column process. The BSA recoveries of the resulted RAM were higher than 99.3%. Small molecules such as alkylbenzene and quinolone antibiotics could be retained with a reversed phase mechanism. The column packed with RAM had good long term stability and could last at least five months without significantly changed in its efficiencies. An on-line SPE/HPLC method for the analysis of enrofloxacin and gatifloxacin in milk samples was established by using the resulted RAM as the solid-phase extraction material. The detection and quantitation limits of two antibiotics were 8.22 and 27.4 ng mL−1, respectively. In the method validation, least recovery 88.5% with relative standard deviation of less than 3.9% was obtained. It demonstrated that the method is reliable and the material can be used for the direct analysis of veterinary drug residues in biological samples.

Analysis of Perfluorinated Compounds in Environmental Water Using Decyl-perfluorinated Magnetic Mesoporous Microspheres as Magnetic Solid-Phase Extraction Materials and Microwave-Assisted Derivatization Followed by Gas Chromatography-mass Spectrometry.

In this work, a new method was developed for perfluorinated compounds (PFCs) analysis in water samples based on decyl-perfluorinated magnetic mesoporous nanocomposites microspheres-assisted extraction and microwave-assisted derivatization followed by gas chromatography-mass spectrometry analysis. The decyl-perfluorinated magnetic mesoporous nanocomposites have several advantages such as fast separation ability, good dispersibility in water sample and high selective preconcentration of PFCs. Various parameters, including eluting solvent and volume, the amounts of absorbents, extraction time and elution time, the microwave-assisted derivatization conditions were optimized. Validation studies showed that this method has good linearity (r2 > 0.9970), satisfactory precision (RSD < 7.8%) and high recovery (93-107%). The limits of detection were found to be 0.055-0.086 μg/L and the limits of quantification be 0.18-0.28 μg/L, respectively. The results indicated that the proposed method has advantages of convenience, good sensitivity and high efficiency. The method has been applied successfully to analyze perfluorinated organic acids in real water samples.

Graphene oxide aggregate-assisted LDI-MS for the direct analysis of triacylglycerol in complex biological samples

Knowledge of blood triacylglycerol (TAG) species is essential to clarify the physiological functions of individual TAG molecules and also to develop potential biomarkers for related diseases. Commonly, lipid samples prepared by organic liquid-liquid extraction contain complex components, thus cannot be directly characterized by mass spectrometry (MS) and often require an additional purification step. Here, we described a laser desorption ionization - mass spectrometry (LDI-MS) method that utilized aggregated graphene oxide (AGO) as both lipid extractant and MS matrix (AGOLDI-MS), to characterize and quantify plasma TAG species without the use of harmful solvent or complex separation step. We first designed and synthesized the AGO material with a multi-layered sheet structure, which could efficiently break up the structure of lipoproteins, and extract plasma TAGs as solid-phase extraction material. Furthermore, in AGOLDI-MS procedure, the AGO could directly act as matrix and selectively produce the MS signals of TAGs without the interferences of phospholipids, which was hardly achieved by using the routine LDI-MS method based on liquid-liquid extraction and small molecular matrix. We confirmed the suitability of AGOLDI-MS as characterization and quantitative tool for TAG species through studying the analysis performances in TAG standards and real plasma samples. To establish potential utility of our method, we characterized 42 human plasmas from healthy and hyperlipemic donators, indicating that the AGOLDI-MS could not only generate comparable quantitative results of total TAGs to current clinical technology, but also monitor the changes of TAG species between different sample groups. This approach could further characterize the compositions of the fatty acid moieties in even low abundant TAGs by the assistance of tandem MS-MS. This concise, specific, and high-throughput approach will facilitate the rapid and precise characterizations of plasma TAGs, and make the MS approach for TAGs more adaptable for clinical uses.

Cationic amine-bridged periodic mesoporous organosilica materials for off-line solid-phase extraction of phenoxy acid herbicides from water samples prior to their simultaneous enantiomeric determination by capillary electrophoresis

Two novel materials based on periodic mesoporous organosilica (PMO) with cationic amine-bridged ligands, (styrylmethyl)bis(triethoxysilylpropyl)ammonium chloride (PMO-STPA) and bis(3-triethoxysilylpropyl)amine (PMO-TEPA), were synthesized in this work to obtain materials with reverse-phase/strong anionic exchange mixed-mode or strong anionic exchange retention mechanism, respectively. The resulting materials were comprehensively characterized and showed functionalization with cationic amine-bridged ligands, and values of surface areas characteristic of mesoporous materials (higher than 100m2/g). These materials were evaluated for the off-line solid-phase extraction (SPE) of a mixture of six phenoxy acid herbicides (fenoprop, mecoprop, dichlorprop, 2-(4-chlorophenoxy)propionic acid (4-CPPA), 2-(3-chlorophenoxy)propionic acid (3-CPPA), 2-phenoxypropionic acid (2-PPA)) from water samples previous to their analysis by CE with diode-array detection using a dual chiral selector system (20mM of heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD) and 7mM of (2-hydroxypropyl)-β-CD (HP-β-CD) dissolved in 50mM phosphate buffer, pH 7.0) which enabled the simultaneous enantiomeric separation of the six phenoxy acid herbicides in 11min. SPE parameters were optimized and recoveries obtained for PMO-STPA and PMO-TEPA sorbents were compared. Under the optimized conditions, it was demonstrated that using 100mg of PMO-STPA sorbent, a maximum preconcentration factor (PF) of 1500 was achieved with 750mL of standard solution, allowing recoveries between 75.5 and 112.2%, with good repeatability (RSD=1.9–8.7%, n=6). Analytical characteristics of the method were evaluated in terms of precision, linearity and accuracy with method quantitation limits (MQL) between 0.4 and 14.3μg/L. The developed method was applied to the analysis of river samples and effluents from wastewater treatment plants, with recoveries ranging from 78.3 to 107.5%.

Determination of Ten Macrolide Drugs in Environmental Water Using Molecularly Imprinted Solid-Phase Extraction Coupled with Liquid Chromatography-Tandem Mass Spectrometry.

With the extensive application of antibiotics in livestock, their contamination of the aquatic environment has received more attention. Molecularly imprinted polymer (MIP), as an eco-friendly and durable solid-phase extraction material, has shown great potential for the separation and enrichment of antibiotics in water. This study aims at developing a practical and economical method based on molecularly imprinted solid phase extraction (MISPE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for simultaneously detecting ten macrolide drugs in different sources of water samples. The MIP was synthesized by bulk polymerization using tylosin as the template and methacrylic acid as the functional monomer. The MIP exhibited a favorable load-bearing capacity for water (>90 mL), which is more than triple that of non-molecularly imprinted polymers (NIP). The mean recoveries of macrolides at four spiked concentration levels (limit of quantification, 40, 100, and 400 ng/L) were 62.6–100.9%, with intra-day and inter-day relative standard deviations below 12.6%. The limit of detection and limit of quantification were 1.0–15.0 ng/L and 3.0–40.0 ng/L, respectively. Finally, the proposed method was successfully applied to the analysis of real water samples.

Preparation and characterization of dummy-template molecularly imprinted polymers as potential sorbents for the recognition of selected polybrominated diphenyl ethers

The main aim of this work was to conduct the preliminary/basic research concerning the preparation process of a new dummy molecularly imprinted polymer (DMIP) materials. Developed DMIPs were proposed as a sorption material in solid-phase extraction (SPE) technique for recognition of selected low mass polybrominated diphenyl ethers (PBDEs) – PBDE-47 and PBDE-99. Four new DMIPs were synthesized employing bulky polymerization technique by application of structural analogue of low mass PBDEs - 4,4′-Dihydroxydiphenyl ether, as a dummy template. The DMIPs and corresponding non-imprinted polymers were prepared using different functional monomers: methacrylic acid; methyl methacrylate and different porogen agents: acetonitrile and tetrahydrofuran. The polymerization reaction was thermally initiated with 1,1′-azobis (cyclohexanecarbonitryle). Ethylene glycol dimethacrylate was applied as a cross-linker. To optimize geometries and to calculate energies of the respective template-monomer complexes, the computational molecular modeling method was employed. The particles morphology and physicochemical characteristics of developed DMIPs and their equivalent NIPs were performed using nitrogen sorption porosimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy. The sorption capacities of prepared DMIPs and corresponding NIPs were studied using standard binding test. The adsorption capability studies give a possibility to assess the imprinting factor (IF) values, which were in the range from 1.1 to 4.0, depending on the DMIP type. The recovery values of PBDE-47 and PBDE-99 from prepared organic solutions were in the range from 43 to 92%, depending on the studied DMIP. Performed basic laboratory studies give a possibility to select the optimal DMIP material which might be applied in the environmental samples preparation process as a potential sorbent for the recognition of low mass PBDEs.

Determination of sulfonamides in milk by capillary electrophoresis with PEG@MoS2 as a dispersive solid-phase extraction sorbent.

A synthetic polyethylene glycol-molybdenum disulfide (PEG@MoS2) composite was prepared using a simple method, and the application of this material in dispersive solid-phase extraction (DSPE) was investigated for the enrichment of eight sulfonamides (SAs) in milk samples. The composite was characterized by energy dispersive spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller measurements. The results showed that the MoS2 synthesized in the presence of PEG has the advantage of a larger surface area and that the adsorption effect of this MoS2 was enhanced. After extraction, the eight SAs were separated by capillary zone electrophoresis with a good linear relationship (R2 > 0.9902) in the range of 0.3–30 µg ml−1 and good precision (between 0.32% and 9.83%). Additionally, good recoveries (between 60.52% and 110.91%) were obtained for the SAs in the milk samples. The developed PEG@MoS2-based DSPE method could be applied for the enrichment of SAs in real milk samples.

Polymeric Sorbent with Controlled Surface Polarity: An Alternate for Solid-Phase Extraction of Nerve Agents and Their Markers from Organic Matrix.

Extraction and identification of lethal nerve agents and their markers in complex organic background have a prime importance from the forensic and verification viewpoint of the Chemical Weapons Convention (CWC). Liquid-liquid extraction with acetonitrile and commercially available solid phase silica cartridges are extensively used for this purpose. Silica cartridges exhibit limited applicability for relatively polar analytes, and acetonitrile extraction shows limited efficacy toward relatively nonpolar analytes. The present study describes the synthesis of polymeric sorbents with tunable surface polarity, their application as a solid-phase extraction (SPE) material against nerve agents and their polar as well as nonpolar markers from nonpolar organic matrices. In comparison with the acetonitrile extraction and commercial silica cartridges, the new sorbent showed better extraction efficiency toward analytes of varying polarity. The extraction parameters were optimized for the proposed method, which included ethyl acetate as an extraction solvent and n-hexane as a washing solvent. Under optimized conditions, method linearity ranged from 0.10 to 10 μg mL-1 ( r2 = 0.9327-0.9988) for organophosphorus esters and 0.05-20 μg mL-1 ( r2 = 0.9976-0.9991) for nerve agents. Limits of detection (S:N = 3:1) in the SIM mode were found in the range of 0.03-0.075 μg mL-1 for organophosphorus esters and 0.015-0.025 μg mL-1 for nerve agents. Limits of quantification (S:N = 10:1) were found in the range of 0.100-0.25 μg mL-1 for organophosphorus esters and 0.05-0.100 μg mL-1 for nerve agents in the SIM mode. The recoveries of the nerve agents and their markers ranged from 90.0 to 98.0% and 75.0 to 95.0% respectively. The repeatability and reproducibility (with relative standard deviations (RSDs) %) for organophosphorus esters were found in the range of 1.35-8.61% and 2.30-9.25% respectively. For nerve agents, the repeatability range from 1.00 to 7.75% and reproducibility were found in the range of 2.17-6.90%.

Core–shell indium (III) sulfide@metal-organic framework nanocomposite as an adsorbent for the dispersive solid-phase extraction of nitro-polycyclic aromatic hydrocarbons

A core–shell discoid shaped indium (III) sulfide@metal-organic framework (MIL-125(Ti)) nanocomposite was synthesized by a solvothermal method and explored as an adsorbent material for dispersive solid-phase extraction (d-SPE). The as-synthesized sorbent was characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, powder X-ray diffraction, N2 adsorption–desorption analysis, and Fourier transform infrared spectroscopy. The extraction performance was evaluated by the d-SPE of 16 nitro-polycyclic aromatic hydrocarbons (NPAHs) from water samples. The analysis was carried out by gas chromatography (GC) coupled with triple quadruple mass spectrometer in negative chemical ionization (NCI) mode. The selected ion monitoring (SIM) was used in the quantification of the target NPAHs. Extraction factors affecting the d-SPE, including the ionic strength, extraction temperature, and extraction time were optimized by the response surface methodology. The developed d-SPE method showed good linear correlations from 10 to 1000 ng L−1 (r > 0.99), low detection limits (2.9–83.0 ng L−1), satisfactory repeatability (relative standard deviation of <10%, n = 6), and acceptable recoveries (71.3%–112.2%) for water samples. The developed method was used for the food and environmental sample analysis. The results demonstrated that the method could be used for sample preparation of trace NPAHs in real samples.

3D hollow porous CdFe2O4 microspheres as viable materials for magnetic solid-phase extraction of azo colorants.

3D magnetic hollow porous CdFe2O4 microspheres (3D MHPS-CdFe2O4) were prepared by aone-step andtemplate-free hydrothermal method. The material was applied for magnetic solid phase extraction of three azo colorants (Acid Red, Congo Red, Sunset Yellow). Compared to conventionalCdFe2O4 nanoparticles, the new 3D material exhibits superior extraction capability because of its unique hollow porous structure, high specific surface area, and the strong interaction between 3D microspheres and the colorants. A magnetic solid phase extraction (MPSE) combined with HPLC was established for simultaneous detection of the three azo colorants in food samples. Under optimum conditions, the detection limits are 0.54-1.00 ng mL-1, and good recoveries of 87.0-100.7% were obtained with spiked samples, with relative standard deviation of ≤ 3.8%. The combination of using the new 3D material and MPSE-HPLC results in an efficient, sensitive and inexpensive method for simultaneous determination of such colorants. Graphical abstract Schematic of the preparation of 3D magnetic hollow porous CdFe2O4 microspheres as solid phase extractant for simultaneous trace detection of three azo colorants in real samples.

Pipette-tip solid-phase extraction using polypyrrole as efficient adsorbent for extraction of avermectins and milbemycins in milk.

In this work, we developed a HPLC method for the multidetermination of avermectins (AVM) (abamectin-ABA 1b and ABA 1a, eprinomectin-EPR, and ivermectin-IVM) and milbemycins (moxidectin-MOX) in milk samples using polypyrrole (PPy) as adsorbent material in pipette-tip solid-phase extraction (PT-PPy-SPE). PPy was characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction and the data agreed with the literature. The sample preparation included the clean-up of the milk by protein precipitation (PP) with acetonitrile and extraction of the analytes by PT-PPy-SPE. The chromatographic method was developed in reverse phase and isocratic mode with flow rate at 1.2mLmin-1 and ultraviolet detection at 250nm. The mobile phase composition was acetonitrile:methanol:water (55:25:20, v/v/v). The studied parameters and the optimized conditions for the sample preparation were washing solvent (300μL water), volume and type of eluent (500μL methanol), volume and pH of sample (1mL and pH 10), amount of adsorbent material (50mg PPy), and without addition of salt (NaCl). The method was linear over the concentration range from 20 to 3000ngmL-1 with coefficients of correlation (r) ≥ 0.99 for all analytes and recoveries around 100%. The method developed and validated was used for the analyses of real milk samples from cow treated with Ivomec® (IVM 3.5%), in which were found 21.51 ± 2.94ngmL-1 of IVM. Finally, the results proved that PT-PPy-SPE coupled to HPLC-UV was economical, simple, and easy-to-perform technique. Graphical abstract Pipette-tip solid phase extraction using polypirrole as adsorbent material for determination of avermectins and milbemycins in milk.