Solid-phase Extraction Separation Research Articles

Fabrication of magnetic hydrophilic imprinted polymers via two-step immobilization approach for targeted detecting bisphenol A

Molecularly imprinted polymer with water-compatibility for effective separation and enrichment of targeted trace pollutants from complicated matrix has captured extensive attention in terms of their high selectivity and matrix compatibility. This study focuses on modified β-cyclodextrin is used as a hydrophilic functional monomer to develop magnetic molecularly imprinted polymers (MMIPs). MMIPs were prepared using Fe3O4 nanoparticles as carriers and bisphenol A (BPA) as templates using a two-step fixation strategy and surface imprinting technology. The structural characteristic and binding properties of the prepared MMIPs were thoroughly studied. The MMIPs exhibited high crystallinity, high adsorption capacity, fast rebinding rate, remarkable selectivity and distinguish reusability. In addition, through magnetic solid-phase extraction separation technology and high-performance liquid chromatography ultraviolet quantitative detection technology, MMIPs are used for selective enrichment and detection of BPA in complex media such as environmental water and milk. This work provides a new route to construct the hydrophilic molecularly imprinted materials and a new sight on developing more effective sample pretreatment strategies for monitoring targeted pollution in complicated aqueous media.

3D printed microfluidic devices for integrated solid-phase extraction and microchip electrophoresis of preterm birth biomarkers

BackgroundPreterm birth (PTB) is a leading cause of neonatal mortality, such that the need for a rapid and accurate assessment for PTB risk is critical. Here, we developed a 3D printed microfluidic system that integrated solid-phase extraction (SPE) and microchip electrophoresis (μCE) of PTB biomarkers, enabling the combination of biomarker enrichment and labeling with μCE separation and fluorescence detection. ResultsReversed-phase SPE monoliths were photopolymerized in 3D printed devices. Microvalves in the device directed sample between the SPE monolith and the injection cross-channel in the serpentine μCE channel. Successful on-chip preconcentration, labeling and μCE separation of four PTB-related polypeptides were demonstrated in these integrated microfluidic devices. We further show the ability of these devices to handle complex sample matrices through the successful analysis of labeled PTB biomarkers spiked into maternal blood serum. The detection limit was 7 nM for the PTB biomarker, corticotropin releasing factor, in 3D printed SPE-μCE integrated devices. SignificanceThis work represents the first successful demonstration of integration of SPE and μCE separation of disease-linked biomarkers in 3D printed microfluidic devices. These studies open up promising possibilities for rapid bioanalysis of medically relevant analytes.

A new strategy for facile and rapid separation of astatine-211 from nitric acid medium

Developing fast and efficient separation avenues can promote either fundamental study or practical application of astatine-211(211At). This work presents a new solid-phase extraction (SPE) separation strategy based on functional resin for recovering 211At from the irradiated bismuth (Bi) target mildly and rapidly, without switching HNO3 medium into HCl system. Four functional resins containing acyl-resin, thioether, sulfonate- and sulfonate-groups had been prepared via Friedel-Crafts acylation and alkylation reactions successfully, and subsequently characterized by FTIR, EA, SEM etc. Acyl-resin from these functional materials have shown good retention towards 211At but low binding affinity to all possible metal impurities (Zn2+, Cu2+, Ga3+and Bi3+) in simulated separation experiments. Static batch sorption experiments indicate that the pseudo-second-order kinetic model is more suitable for describing the binding behavior of 211At on Acyl-resin. This reveals that chemisorption dominates the reaction between the target radionuclide and functional material. During several practical separations in medically-used scale, over 98.5 % of 211At can be well retained on SPE column with metal impurities removed in the process of loading target solution and removing non-target radionuclides. More importantly, 60.03 %∼79.05 % of 211At on the Acyl-resin SPE column is recoverable by NH2OH-NH3·H2O-CH3OH elution process, and over 60 % of the radioactivity distributes in volatile organic solvent (CH3OH). The whole SPE separation process can be completed within 20 min, giving 211At product with high radionuclidic purity (≥ 99 %), low metal impurities (Bi3+≤ 17.37 μg and Cu2+≤ 2.91 μg) and high radiolabeling availability. This work implies that acyl-groups can act as potential binding motifs not only for developing new 211At separation methods but also designing bifunctional conjugate agents for astatinated compounds based on coordination bonds.

Homochiral Porous Metal-Organic Polyhedra with Multiple Kinds of Vertices.

Metal-organic polyhedra featuring non-Archimedean/Platonic architectures with multiple kinds of vertices have aroused great attention for their fascinating structures and properties but are yet challenging to achieve. Here, we report a combinatorial strategy to make such nonclassic polyhedral cages by combining kinetically labile metal ions with non-planar organic linkers instead of the usual only inert metal centers and planar ligands. This facilitates the synthesis of an enantiopure twisted tetra(3-pyridyl)-based TADDOL (TADDOL = tetraaryl-1,3-dioxolane-4,5-dimethanol) ligand (L) capable of binding Ni(II) ions to produce a regular convex cage, Ni6L8, with two mixed metal/organic vertices and three rarely reported concave cages Ni14L8, Ni18L12, and Ni24L16 with three or four mixed vertices. Each of the cages has an amphiphilic cavity decorated with chiral dihydroxyl functionalities and packs into a three-dimensional structure. The enantioselective adsorption and separation performances of the cages are strongly dependent on their pore structure features. Particularly, Ni14L8 and Ni18L12 with wide openings can be solid adsorbents for the adsorptive and solid-phase extractive separation of a variety of racemic spirodiols with up to 98% ee, whereas Ni6L8 and Ni24L16 with smaller pore apertures cannot adsorb the racemates. The combination of single-crystal X-ray diffraction analysis of the host-guest adduct and GCMC simulation indicates that the enantiospecific recognition capabilities originate from the well-organized chiral inner sphere as well as multiple interactions within the chiral microenvironment. This work therefore provides an attractive strategy for the rational design of polyhedral cages, showing geometrically fascinating structures with properties different from those of classic assemblies.

Heterogeneous adsorbent based on CeZrO2 nanoparticles doped magnetic graphene oxide used for vortex assisted magnetic dispersive solid phase extraction of erythromycin in chicken

A simple, fast, and efficient method of vortex assisted magnetic dispersive solid phase extraction for separation and pre-concentration of erythromycin in chicken samples prior to high LC-UV determination has been developed. The novel heterogeneous CeZrO2 nanoparticles doped magnetic graphene oxide, for use as an efficient nanosorbent, was synthetised and applied for the adsorption of erythromycin. The synthetised nanosorbent was characterised using both Fourier-transform infra-red (FT-IR) and energy dispersive X-Ray (EDX) spectroscopy together with field emission scanning electron microscopy-EDX. To obtain the best extraction condition and maximum extraction efficiency of erythromycin, the effect of important parameters including pH, amount of sorbent, vortexing time, ionic strength, sample volume, and desorption conditions were investigated. At optimum conditions, a linear range of 0.25–300 µg kg−1, LOD (S/N = 3) of 0.079 µg kg−1, and LOQ (S/N = 10) of 0.270 µg kg−1 were obtained. The precision of the method was established as having an RSD (%) at 100 µg kg−1 of erythromycin for seven replicates of 2.6% and 3.2% for the intra-day and the inter-day, respectively. Recoveries over 94.0% confirmed a high capability of the proposed method for separation and determination of erythromycin residues in chicken being one of the most important animal products.

Advanced solid-phase extraction of tetravalent actinides using a novel hierarchically porous functionalized silica monolith

Separation of actinides is of great concern from the perspective of nuclear energy development and environmental issues, and the development of a highly efficient solid-phase extraction (SPE) process holds significant promise for actinide separation. However, the slow mass transfer kinetics in the currently available SPE separation media limited the throughput and efficiency, rendering the separation process more challenging. Hierarchically porous structures with well-organized and highly interconnected pore systems have been shown to provide efficient mass transfer and enhanced performance in nature. Herein, this paper reports the synthesis of a crack-free diglycolamic acid-functionalized silica monolith with hierarchical macro and meso porous structure for SPE. The hierarchically porous structures were retained upon mild modifications, which favored the convective mass transport and provided more binding sites, resulting in fast kinetics and high throughput. The separation ability was evaluated based on the separation and recovery of Th(IV) from a complex matrix. A superior Th(IV) separation performance (Kd > 2.6 × 104 mL/g) was achieved in the presence of alkaline earth metals, rare earth elements, and uranium within 1 min by batch sorption, and the maximum separation coefficients of Th(IV)/Ln(III) and Th(IV)/U(VI) exceed 1000 and 140, respectively. Particularly, the synthesized material allowed the separation of Th from monazite leachates with highly efficient recovery (> 96%) at a high flow rate (5 mL/min) by column study. Investigation of the binding mechanism revealed the formation of a stable coordination complex (Th(NO3)L3) via Th−O bonds. The material was also employed for the extraction of Pu(IV), and satisfactory sorption was achieved. Thus, this new functionalized material has potential application prospects for an improved actinide separation process.

Preparation of a Novel Resin Based Covalent Framework Material and Its Application in the Determination of Phenolic Endocrine Disruptors in Beverages by SPE-HPLC.

A new type of economical covalent organic framework material(COF), namely resin based covalent organic framework material, was prepared by combining resin and covalent organic framework material by hydrothermal synthesis, which was based on the preparation of traditional COF material(TpBD COF). The properties of the material and covalent organic framework material were compared in the way of characterization, and the possible reaction mechanism was analyzed. The solid phase extraction separation (SPE) ability of this material for four kinds of phenolic endocrine disrupting compounds (bisphenol F, bisphenol A, octylphenol and nonylphenol) in beverage samples was investigated. The results showed that the prepared COF materials had abundant internal channels, ordered structure, large specific surface area (TpBD COF: 814.6 m2/g and resin based COF: 623.9 m2/g) and good thermal stability (pyrolysis temperature was 443 °C and 437 °C, respectively). Solid phase extraction experiments demonstrated that the two COF materials as adsorbent of solid phase extraction column had ideal adsorption separation effect and good anti-interference ability, and had strong anti-interference ability. The SPE effect was superior to the traditional solid phase extraction column. The precision RSD of this method was less than 3%. This SPE method had high recovery and could be reused (carbonated beverage: 98.18–102.18% and beverage: 98.52–101.79%), In addition, the recovery of the material did not change significantly in the 50 cycles of solid phase extraction, indicating that the material had good stability and could be reused, which could meet the requirements for the detection and analysis of trace pollutants in environmental samples. The resin based COF material prepared in this study could reduce the cost of monomer uses and provide a possibility for its industrial production. At the same time, as an efficient SPE adsorbent, it also provided a new research scheme for the enrichment of trace phenolic endocrine disruptors in beverage samples.

Dithizone-functionalized C18 online solid-phase extraction-HPLC-ICP-MS for speciation of ultra-trace organic and inorganic mercury in cereals and environmental samples

A simple and efficient dithizone-functionalized solid-phase extraction (SPE) procedure, online coupled with high-performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry, was developed for the first time for enrichment and determination of ultra-trace mercury (Hg) species (inorganic divalent Hg (Hg(II)), methylmercury (CH3Hg(II)) and ethylmercury (C2H5Hg(II)) in cereals and environmental samples. In the proposed method, functionalization of the commercial C18 column with dithizone, enrichment, and elution of the above Hg species can be completed online with the developed SPE device. A simple solution of 2-mercaptoethanol (1% (V/V)) could be used as an eluent for both the SPE and HPLC separation of Hg species, significantly simplifying the method and instrumentation. The online SPE method was optimized by varying dithizone dose, 2-mercaptoethanol concentration, and sample volume. In addition, the effect of pH, coexisting interfering ions, and salt effect on the enrichment was also discussed. Under the optimized conditions, the detection limits of Hg species for 5 mL water sample were 0.15 ng/L for Hg(II), 0.07 ng/L for CH3Hg(II), and 0.04 ng/L for C2H5Hg(II) with recoveries in the range of 85%–100%. The developed dithizone-functionalized C18 SPE column can be reused after a single functionalization, which significantly simplifies the enrichment step. Moreover, the stability of Hg species enriched on the SPE column demonstrated its suitability for field sampling of Hg species for later laboratory analysis. This environment-friendly method offers a robust tool to detect ultra-trace Hg species in cereals and environmental samples.

A new method for the simultaneous determination of urinary NNAL and cotinine concentrations using HILIC-MS/MS coupled with PRiME HLB SPE

Urinary cotinine and NNAL are the biomarkers of tobacco smoke exposure and tobacco specific nitrosamines (TSNAs), respectively. A new method for the simultaneous analysis of them by hydrophilic interaction liquid chromatography tandem mass (HILIC-MS/MS) combined with PRiME HLB solid phase extraction (SPE) was developed. The sample matrix was removed effectively with PRiME HLB SPE and HILIC separation. The linearities were good in a range of 5.00-3.00 × 103 ng/L for NNAL and 0.200-4.00 × 102 μg/L for cotinine. The method detection limit of NNAL (0.0580 ng/L) was better than that in other literatures, and 0.0240 μg/L for cotinine. Recoveries were 91.6-110% and 88.7-113% with relative standard deviations of 3.78-9.12% and 0.120-1.15% for NNAL and cotinine, respectively. 29 urine samples were detected by the established method. The contents of NNAL and cotinine were 0.590-66.7 ng/g·Cr and 2.86-1.34 × 103 μg/g·Cr, respectively. Moreover, the results showed that urinary NNAL and cotinine were significantly positive correlation, even in passive smokers.

Topological Strain-Induced Regioselective Linker Elimination in a Chiral Zr(IV)-Based Metal-Organic Framework

Summary Zr-carboxylate metal-organic frameworks (MOFs) are structurally robust materials, in part due to their strong coordination bonds. The regioselective Zr–O bond cleavage and formation between 3D architectures are thus challenging and are heretofore unexplored. In this work, by introducing highly flexible 18-crown-6-ether functionalities into a homochiral Zr-MOF, we report an unprecedented topology transition in which a 4,10-connected framework undergoes a rapid solid-state transition into a thermodynamically more stable 4,8-connected analog by a regioselective-linker-elimination under ambient conditions. The transition process was unambiguously unraveled by single-crystal and powder X-ray diffraction studies, and we proposed a possible transition mechanism based on various control experiments and theoretical calculations. The excellent chemical stability and substantially expanded porosity and pore apertures endowed the transformed chiral MOF with an exceptional capacity for the enantioadsorptive and solid-phase extractive separation of the racemic drug molecule of lansoprazole with 98% ee and 93% ee, respectively.

Characterization of organosulfur compounds in asphalt cement samples by ESI(+)FT-ICR MS and 13C NMR spectroscopy

Herein, it is presented a methodology for the characterization of organosulfur compounds in asphalt cement (AC) samples employing solid-phase extraction (SPE) associated with methylation reactions and positive-ion mode electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI(+)FT-ICR MS) and carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. Three AC samples were submitted to an SPE separation, and the fractions obtained the original AC samples, and their maltenes were methylated and analyzed using the ESI(+)FT-ICR MS. The ESI(+)FT-ICR MS ionized the sulfur fractions much better than the original samples, detecting organosulfur compounds with a broader average molecular mass distribution (Mw). Several types of sulfur compounds were detected, such as sulfides, disulfides, thiophenes, and dibenzothiophenes. Besides, the ESI(+)FT-ICR data were compared with the 13C NMR (from model molecules analyses) and ESI(+)-Orbitrap MS. The organosulfur chemical profile was correlated to the physical properties of AC samples. It was verified that the samples with higher aromatic-character were less susceptible to aging test, while the one with more saturated-character presented more significant variation in their physical properties after the aging test.

Fractionation and molecular characterization of natural organic matter (NOM) by solid-phase extraction followed by FT-ICR MS and ion mobility MS

Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been widely used for the characterization of dissolved organic matter (DOM) extracted by solid-phase extraction (SPE) from various environmental waters. It is known that common SPE generally has a relatively low recovery and the non-polar and weakly polar components are less likely to be ionized due to ionization discrimination. However, the molecular selectivity during SPE is not clear so far. In this study, the Suwannee River natural organic matter (SRNOM) was fractionated by multi-step SPE with different solvents and the fractions were characterized by negative ESI FT-ICR MS and trapped ion mobility spectrometry-mass spectrometry (IMS-MS). The sequential solvent elution increased the extraction recovery of DOM in water by SPE and enabled the characterization of a weakly polar component, which cannot be detected in common SPE separation. The weakly polar component accounts for 5.7% in TOC for the SRNOM, which has complex but different molecular composition with methanol- and/or water-eluted fractions. Lipid-like compounds were enriched in this fraction. Compared with the polar molecules directly eluted by one-step SPE from the SRNOM, the weakly polar fractions exhibit larger molecular size. The results are helpful for understanding of the molecular composition of SRNOM, as well as other environmental waters. In addition, the study demonstrates that the combination of FT-ICR MS and IMS-MS has potential to characterize the chemical composition of a complex mixture, like DOM, to a new depth. Graphical abstract.

Isolation and characterization of hydrophilic dissolved organic matter in waters by ion exchange solid phase extraction followed by high resolution mass spectrometry

Dissolved organic matter (DOM) is a complex substance occurring in marine and freshwater environments. DOM has many functions that modify physical, chemical and biological processes in ecological systems. Solid-phase extraction (SPE) is widely used for the separation of DOM. However, a part of strongly hydrophilic compounds are lost using classical SPE separation. In this article, the strong hydrophilic components, which cannot be extracted by the hydrophobic reverse phase SPE, were further extracted in a natural organic matter sample by ion exchange SPE cartridges to obtain hydrophilic acid (HIA), hydrophilic neutral (HIN), and hydrophilic base (HIB) fractions. The extracts were characterized by three-dimensional excitation–emission matrix fluorescence spectroscopy and negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results revealed that the hydrophilic components were significantly different from the hydrophobic components in molecular composition. Hydrophilic components were identified as tryptophan-like and tyrosine-like compounds by three-dimensional fluorescence spectra. The HIA fraction contains mainly tannic acid-like compounds with high O/C ratio; the HIB fraction contains mainly amide-like compounds; and the HIN fraction contains mainly lignin and lipids.

Comprehensive Characterization of Petroleum Acids by Distillation, Solid Phase Extraction Separation, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Crude acids or petroleum acids are considered to be one of the prime contributors to corrosion, emulsion, and fouling issues across upstream, downstream, and chemical operations. Thus, the composition of crude acids has been extensively studied in the last several decades. To achieve molecular level characterization, mass spectrometry is typically applied. However, one of the challenges in mass spectrometry characterization is that the dynamic range of the technique can severely limit the compositions observed. Here, we employ multiple separations before analyzing crude oil acid fractions to overcome this limitation. First, a whole crude (WC) oil was distilled into boiling point fractions including vacuum gas oil (VGO) and vacuum residue (VR). Acids were then collectively isolated from the VGO and VR fractions as well as the starting WC using a solid phase extraction (SPE) method. Isolated acids were also further separated by molecular weight (MW) using a similar SPE technique. The acid fractions were the...

Determination of non-liposomal and liposomal doxorubicin in plasma by LC-MS/MS coupled with an effective solid phase extraction: In comparison with ultrafiltration technique and application to a pharmacokinetic study.

Liposomal formulation of doxorubicin has been widely applied in clinic for treatment of various cancers. The separation and measurement of free drug (drug which is not entrapped in liposomes) and liposomal drug in the plasma after injection of liposomal doxorubicin is of prime importance due to toxicity and activity concerns. In this study, a rapid and convenient method was developed to isolate and determine the non-liposomal and liposomal drugs in plasma. Plasma samples were prepared by solid phase extraction (SPE) using Oasis HLB cartridges. Liposomal doxorubicin (L-DOX) was collected in the aqueous eluate with its internal standard (IS), metformin; and non-liposomal doxorubicin (NL-DOX) and its isotope labelling IS were eluted from the cartridge by methanol containing 0.5% formic acid. After SPE separation, L-DOX and NL-DOX were subsequently quantified by a validated sensitive LC-MS/MS method individually. The calibration curves were found to be linear for L-DOX in the range of 0.156-40.0μg/mL and for NL-DOX in the range of 3.13-200ng/mL. The extraction recovery was about 97% for L-DOX and about 65% for NL-DOX. This method was further applied to investigate the pharmacokinetics of doxorubicin in Beagle dogs after an intravenous dose of 1.0mg/kg Doxil®. After injection of Doxil®, L-DOX was the predominant component circulating in plasma, whose amount was about 1000-fold higher than that of NL-DOX. The analytical method might be helpful in pharmacokinetics and toxicity assessment of liposomal formulation.

Automated microfluidic devices integrating solid-phase extraction, fluorescent labeling, and microchip electrophoresis for preterm birth biomarker analysis.

We have developed multichannel integrated microfluidic devices for automated preconcentration, labeling, purification, and separation of preterm birth (PTB) biomarkers. We fabricated multilayer poly(dimethylsiloxane)-cyclic olefin copolymer (PDMS-COC) devices that perform solid-phase extraction (SPE) and microchip electrophoresis (μCE) for automated PTB biomarker analysis. The PDMS control layer had a peristaltic pump and pneumatic valves for flow control, while the PDMS fluidic layer had five input reservoirs connected to microchannels and a μCE system. The COC layers had a reversed-phase octyl methacrylate porous polymer monolith for SPE and fluorescent labeling of PTB biomarkers. We determined μCE conditions for two PTB biomarkers, ferritin (Fer) and corticotropin-releasing factor (CRF). We used these integrated microfluidic devices to preconcentrate and purify off-chip-labeled Fer and CRF in an automated fashion. Finally, we performed a fully automated on-chip analysis of unlabeled PTB biomarkers, involving SPE, labeling, and μCE separation with 1h total analysis time. These integrated systems have strong potential to be combined with upstream immunoaffinity extraction, offering a compact sample-to-answer biomarker analysis platform. Graphical abstract Pressure-actuated integrated microfluidic devices have been developed for automated solid-phase extraction, fluorescent labeling, and microchip electrophoresis of preterm birth biomarkers.

Fast arsenic speciation in water by on-site solid phase extraction and high-resolution continuum source graphite furnace atomic absorption spectrometry

A method of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS), combined with on-site separation/solid phase extraction (SPE) has been developed for the speciation of inorganic As (iAs) in geothermal and drinking water samples. The HR-CS-GFAAS calibration curves were linear up to 200μg/L As, but using second order polynomial fitting, accurate calibration could be performed up to 500μg/L. It has been demonstrated that sample pH should not be higher than 8 for an accurate speciation of As(V) with a recovery of ≈95%. Geothermal water had fairly high salt content (≈2200mg/L) due to the presence of chlorides and sulfates at mg/L levels. Therefore, a two-fold dilution of these types of samples before SPE is recommended, especially, for total As determinations, when the As concentration is as high as 400μg/L. For drinking water, sampled from public wells with records of As concentrations higher than the 10μg/L in the past, the reduction of As contamination below the WHO's health limit value could be observed. However, the electrical conductivity was close to 2500μS/cm, i.e., the guideline limit for drinking water, which was due to their higher chloride content. The proposed fit-for-purpose SPE-HR-CS-GFAAS method could be a candidate for screening drinking water quality.

On-cartridge derivatisation using a calixarene solid-phase extraction sorbent for facile, sensitive and fast determination of formaldehyde in beer

This work demonstrates the successful application of an on-cartridge derivatisation procedure for facile, fast and sensitive determination of formaldehyde in beer by HPLC-UV. The derivatisation and solid-phase extraction (SPE) were integrated into a novel calixarene SPE sorbent: tetraazacalix[2]arene[2]triazine bonded silica gel. Specifically, 2,4-dinitrophenylhydrazine was adsorbed onto the sorbent in advance, based on the charge-transfer interaction between the macrocyclic molecule and nitrobenzenes. The method was optimised and validated: under the optimal conditions of derivatisation, SPE and HPLC separation, good linearity was obtained in the range of 0.080–3.2μgmL−1 with a correlation coefficient of 0.9939, the limit of detection was 3.0ngmL−1 (S/N=3), the limit of quantification was 10ngmL−1 (S/N=10), and the recovery level using this method was desirable at 75–84%. The developed method was successfully applied to determine formaldehyde content in real beer samples; the results were in the range of 0.11–1.1μgmL−1.

Determination of Underivatized Glyphosate Residues in Plant-Derived Food with Low Matrix Effect by Solid Phase Extraction-Liquid Chromatography-Tandem Mass Spectrometry

A method was developed for the determination of glyphosate residues in plant-derived food using a two-step solid phase extraction (SPE) combined with mixed-mode liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted with water. Then, the extracting solution was pretreated by a C18 cartridge to remove protein and weak-polar interferences and further directly extracted using a strong anion exchange (SAX) cartridge to remove neutral and basic substances. The obtained glyphosate residues from the SPE were separated on a hydrophilic interaction/weak anion-exchange (HILIC/WAX) column and detected by mass spectrometry with negative electrospray ionization (ESI-) in multiple reaction monitoring (MRM) mode. This approach was evaluated by five different kinds of plant-derived food (soybean, corn, carrot, apple, and spicy cabbage) matrices in terms of matrix effect and recovery. Results showed that two-step SPE and mixed-mode chromatography separation provided the method with a very low matrix effect, and the spiked recoveries of glyphosate were satisfied in the range of 83.1 to 100.8 % at three spiked levels. The limit of quantification (LOQ) and detection (LOD) of the method in different matrices were 0.016–0.026 and 0.005–0.008 mg kg−1, respectively. The procedure was validated and showed good accuracy and precision over a large linear range of 0.02–10 mg kg−1.

SERS-active sorbent based on aluminum oxide loaded with silver nanoparticles

Abstract The article describes development and application of new SERS-active sorbents for combination of surface-enhanced Raman spectroscopy (SERS) with solid-phase extraction (SPE). These sorbents are based on aluminum oxide powder loaded with silver nanoparticles (AgNP) and have been used for analyte pre-concentration with further direct detection on sorbent surface by SERS. Proposed sorbent synthesis is very easy and inexpensive while embedding of previously prepared non-aggregated or artificially aggregated AgNP to alumina matrix allows tuning optical properties and increasing Raman spectra enhancement. Surface modification of the sorbent via polyelectrolyte molecules was carried out as well in order to regulate surface charge and sorption properties. Thus, described approach can be further applied for analysis of multicomponent mixtures via SPE separation with further SERS detection.