Quantification of neomycin in rubella vaccine by off/on metal ion mediated photoluminescence from functionalized graphene quantum dots

The determination of neomycin sulfate was made using photoluminescent amino-functionalized graphene quantum dots (obtained from hydro-exfoliation of a mixture of citric acid and glutathione). From the several ions tested, Fe³⁺ was the best mediator to enable an off/on photoluminescence effect used for quantification. The mediation of Fe³⁺ was found to be crucial as it is responsible for the photoluminescence quenching effect, due to the interaction with quantum dots surface, also having large affinity towards neomycin that removes Fe³⁺ from the surface of GQDs, consequently, promoting restoration of the original nanomaterial photoluminescence. Such signal restoration was proportional to the neomycin sulfate concentration added. The linearized analytical response covered three orders of magnitude (10^-7 to 10^-5 mol L^-1). The proposed method is an alternative to those requiring labor-intensive procedures for chemical the derivatization of neomycin (due to the lack of chromophore groups in aminoglycosides). The method was successfully tested in the analysis of rubella vaccine containing trace residues of neomycin and in pharmaceutical compositions containing neomycin sulfate after solid phase extraction using an aminoglycoside imprinted polymer to improve selectivity in determinations.

A metal organic framework polymer monolithic column as a novel adsorbent for on-line solid phase extraction and determination of ursolic acid in Chinese herbal medicine

A metal organic framework (MOF)-polymer monolithic column was prepared by redox initiation using modified MOF and N-methylolacrylamide (NMA) as co-monomers. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement. It was used as a solid phase extraction (SPE) absorbent for the online enrichment of ursolic acid (UA) by high performance liquid chromatography. The adsorption amount of UA on the monolith was compared with that of silica gel-C18 adsorbent and the monolith without MOF material. The MOF-polymer monolithic column showed high selectivity and good permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 79.854× + 0.1939; the linear range was 0.001-0.9 mg/mL; the linear regression coefficient was 0.9993; the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 μg/mL and 0.57 μg/mL, respectively; the inter-day and intra-day accuracies were <6.44%; the recovery was in the range of 86.52-105.26%. The MOF-polymer monolithic column was successfully used as SPE column for enrichment and determination of UA in Chinese herbal medicine.

Using Magnetic Multiwalled Carbon Nanotubes as Modified QuEChERS Adsorbent for Simultaneous Determination of Multiple Mycotoxins in Grains by UPLC-MS/MS

The simultaneous detection of multiple mycotoxins is important due to the increased toxic effects of combined mycotoxins in grains. In this research, a combination of modified QuEChERS with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for simultaneous detection of 20 mycotoxins in grains. A series of different types of magnetic (Fe₃O₄) nanoparticles modified with multiwalled carbon nanotubes (Fe₃O₄-MWCNTs) were designed as modified QuEChERS adsorbents for facile and efficient purification and for target interferences removal in the matrices. When there is an external magnetic field, the proposed modified QuEChERS method uses a shorter pretreatment time compared with the traditional QuEChERS method, which makes it possible to conduct high-throughput analyses. To optimize the QuEChERS process, the extraction solvent and the type and amount of the Fe₃O₄-MWCNTs were investigated. Under optimal conditions, the method was validated and showed satisfactory linearity (r² ≥ 0.9965), good recovery (73.5-112.9%), good precision (1.3-12.7%), and excellent sensitivity (ranging from 0.0021 to 5.4457 ng g^-1), which indicates that this method can be used for detecting multiple mycotoxins in real samples.

Preparation of magnetic molecularly imprinted polymers for the rapid detection of diethylstilbestrol in milk samples

BACKGROUND

Diethylstilbestrol (DES) residues are harmful to human health because of their potential carcinogenic properties. Therefore, it is important to develop a fast and efficient pretreatment method to prevent their harmful effects on human health and the environment.

RESULTS

In this paper, two types of magnetic molecularly imprinted polymers (MMIPs) of DES were prepared by bulk polymerization and the sol-gel method, respectively. The synthetic materials were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. Adsorption capacities of the bulk and sol-gel MMIPs were investigated. A rapid detection method was developed using the two types of MMIPs as sorbents, coupled to high-performance liquid chromatography, for the determination of DES residues in milk samples. Under optimized conditions, the limit of detection (S/N = 3) of both methods for DES was 2.0 μg L^-1 ; and the linear response range to DES was 0.1-500 mg L^-1 . The milk samples were analyzed according to this method with good recoveries of 88.3-97.6 and 90.5-103.5% for the two types of MMIPs, respectively.

CONCLUSIONS

The method described had high sensitivity and high selectivity, and could prove to be a new method for the rapid determination of DES residues in milk samples. © 2019 Society of Chemical Industry.

Evaluation system construction and factor impact analysis of silica-gel adsorption to extract phytosterol glycosides from soybean lecithin powder

BACKGROUND

Soybean lecithin powders are good sources of phytosterol glucosides (PGs) containing acyl-sterylglycosides (ASGs) and sterylglucosides (SGs), but PG extraction from soybean lecithin powder is difficult due to the solubilizing property of phospolipids. To comprehensively utilize soybean lecithin resources, an evaluation system construction and factor impact analysis of PG extraction by silica-gel adsorption was investigated in this article.

RESULTS

With high-performance liquid chromatography (HPLC) as the main experimental analysis method, software such as SIMICA and SPSS were applied to construct an evaluation system of PG extraction. Different from scores plot in SIMICA for distinguishing samples in chloroform from others, the loading plot and binary variant correlation analysis of all indicators in PG extraction were brought to confirm four evaluation indicators containing PG purity, ASG recovery, SG recovery and phospholipid recovery. In the factor impact analysis, four times elution from silica-gel sediment was enough to achieve a PG product with least reagent waste, while SPW in petroleum ether at 50 mg mL-1 with 1:3 silica-gel dosage (lecithin/silica-gel, w/w) was then determined as the optimum of single factors.

CONCLUSION

All studies in this article were of great significance, as they laid foundations for research of PG extraction procedure, as well as PG industrial production, facilitating the comprehensive utilization of lecithin resources. © 2019 Society of Chemical Industry.

Synthesis and Application of Novel Molecularly Imprinted Solid Phase Extraction Materials Based on Carbon Nanotubes for Determination of Carbofuran in Human Serum by High Performance Liquid Chromatography

Novel molecularly imprinted polymers (MIPs) based on multiwalled carbon nanotubes (MWNTs) were synthesized using carbofuran as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-liking agent, respectively. Characterization results showed that the carbofuran MIPs have been successfully grafted onto the surface of MWNTs as a thin layer with high stability. The results of adsorption dynamics indicated that the synthesized MWNT-MIPs displayed a biphase adsorption profile and good selective recognition to carbofuran with equilibrium adsorption of 106.2 mg/g. The MWNTs-MIPs synthesized were further applied as the adsorbent material of solid-phase extraction (SPE) for the pretreatment of carbofuran in human serum, analyzed using high performance liquid chromatograph (HPLC). The recoveries obtained ranged from 89.0 ± 4.8 to 93.6 ± 3.2, showing that the MWNTs-MIPs-SPE system developed have specific recognition toward carbofuran. Results above indicated that the proposed system filled with synthesized MWNTs-MIPs provided a fast and selective extraction of carbofuran in serum.

Simultaneous Determination of Acrylamide and 5-Hydroxymethylfurfural in Heat-Processed Foods Employing Enhanced Matrix Removal-Lipid as a New Dispersive Solid-Phase Extraction Sorbent Followed by Liquid Chromatography-Tandem Mass Spectrometry

The goal of this study was to develop a method for simultaneous determination of acrylamide (AA) and 5-hydroxymethylfurfural (5-HMF) in heat-processed foods by liquid chromatography-tandem mass spectrometry analysis. Several cleanup methods for the quick, easy, cheap, effective, rugged, and safe (QuEChERS) protocol were investigated and compared: (a) dispersive solid-phase extraction (d-SPE) with Enhanced Matrix Removal-Lipid (EMR-Lipid), (b) d-SPE with primary secondary amine, (c) without the cleanup step, and (d) cleanup with n-hexane. It is the first time that EMR-Lipid sorbent has been used as a d-SPE material to detect AA and 5-HMF in heat-processed foods, and among the four cleanup methods, the EMR-Lipid method provided the best cleanup of co-extracted matrix interferences and the highest extraction efficiency. Validation experiments were carried out for the method using EMR-Lipid as the d-SPE sorbent. Excellent linearity ( R² > 0.999) was achieved, and the limits of detection (LODs) of AA and 5-HMF were 2.5 and 12.5 μg/kg, respectively. The recoveries of AA and 5-HMF levels obtained were in the ranges of 87.3-103.3 and 83.2-104.3%, with precision [relative standard deviations (RSDs)] of 1.2-6.8 and 1.4-7.4% ( n = 3), respectively. The method is accurate and reliable and was successfully applied to analyze the AA and 5-HMF in eight categories of Chinese heat-processed foods.

Novel Bruton tyrosine kinase inhibitor acalabrutinib quantification by validated LC-MS/MS method: An application to pharmacokinetic study in Sprague Dawley rats

USFDA has approved a novel Bruton tyrosine kinase (BTK) inhibitor acalabrutinib (ACA) for the treatment of mantle cell lymphoma in adults. ACA is more potent and selective with fewer side effects compared to other Bruton tyrosine kinase inhibitors. In the current work a highly sensitive, selective and specific LC-MS/MS method for the estimation of acalabrutinib (ACA) in rat plasma was developed. Agilent Eclipse Plus C 8 column (50 mm × 4.6 mm, μm), with gradient elution using 10 mM ammonium formate and acetonitrile as mobile phase at a flow rate of 0.6 mL/min was used for the chromatographic separation. The ion transitions were quantified in positive mode with MRM transition of 466.1→372.3 for ACA and 236.8→194.0 for internal standard (IS). Solid phase extraction process was used as sample preparation approach. The method was validated according to USFDA bioanalytical guidelines. The method provided good linearity over the range of 0.2-199.14 ng/mL for ACA with short run time of 4 min. The method offers very high sensitivity (0.2 ng/mL) and was free from matrix interferences. The validated LC-MS/MS method was successfully applied for in vivo pharmacokinetic study in Sprague Dawley rats. The C_max of ACA was found to be 25.56 ng/mL reaching at time of 0.5 h. The developed analytical method can also be utilized for bioequivalence studies and/or for pharmacokinetic studies in clinics.

Novel nanofibers mat as an efficient, fast and reusable adsorbent for solid phase extraction of non-steroidal anti-inflammatory drugs in environmental water

Core-shell polyaniline/polyacrylonitrile nanofibers mat (PANI/Pan NFsM) was prepared for extraction of hydrophilic non-steroidal anti-inflammatory drugs (NSAIDs) in environmental water. Superior adsorption and desorption performance of PANI/Pan NFsM was confirmed by both static and dynamic adsorption/desorption experiments. These properties proved PANI/Pan NFsM was a potentially efficient and fast solid phase extraction (SPE) adsorbent for NSAIDs. Under the optimized conditions, only 3 mg of PANI/Pan NFsM could easily extract eight target analytes in 10 mL of water sample without any pre-treatment, and the analytes retained on NFsM could be easily eluted by 500 μL of 1% acetic acid methanol for direct UPLC-MS/MS analysis. In addition, each piece of PANI/Pan NFsM could be reused for at least 20 times without performance decline. Possible adsorption mechanisms were also proposed. Practical feasibility was validated through the actual sample analysis.

Simultaneous determination of FLZ and its metabolite (M1) in human plasma and urine by UHPLC-MS/MS: Application to a pharmacokinetic study

FLZ is a novel anti-Parkinson's disease candidate drug. The main active metabolite is FLZ O-dealkylation (M1) in preclinical studies. A reliable ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) quantitation method was developed for the simultaneous determination of FLZ and M1 with low limits of quantitation in human plasma (0.1 ng/mL) and urine (0.5 ng/mL). The plasma and urine samples were both purified by full-automatic solid phase extraction (SPE) method with ensured high extraction recovery and little matrix effect for both analytes, and then separated on a BEH C₁₈ column (2.1 × 50 mm, 1.7 μm). Detection and quantification were performed using an electrospray ionization (ESI) source in positive mode by multiple reaction monitoring (MRM). The precursor to product ion transitions were monitored at m/z 450.3⁺→313.2⁺ for FLZ, m/z 436.3⁺→299.1⁺ for M1, m/z 462.6⁺→142.0⁺ for [D₁₂]-FLZ (internal standard of FLZ) and m/z 447.2⁺→125.2⁺ for [D₁₁]-M1 (internal standard of M1), respectively. This method showed good linearity, accuracy, precision and stability in the range of 0.1-100 ng/mL in plasma and 0.5-500 ng/mL in urine of two analytes. Finally, the developed method was successfully applied to a pharmacokinetic research in Chinese healthy volunteers after oral administration of FLZ tablets.

Bioinspired Polydopamine/Polyzwitterion Coatings for Underwater Anti-Oil and -Freezing Surfaces

Zwitterionic polymers are continually suggested as promising alternatives to tune the surface/interface properties of materials in many fields because of their unique molecular structures. Tremendous efforts have been devoted to immobilizing zwitterionic polymers (polyzwitterions, PZIs) on the material surfaces. However, these efforts usually suffer from cumbersome and time-consuming procedures. Herein we report a one-step strategy to facilely achieve the bioinspired polydopamine/polyzwitterion (PDA/PZI) coatings on various substrates. It requires only 30 min to form PDA/PZI coatings by mixing oxidant, dopamine, and zwitterionic monomers, including carboxybetaine methacrylate (CBMA), sulfobetaine methacrylate (SBMA), and 2-methacryloxyethyl phosphorylcholine (MPC). These bioinspired coatings display multifunctional properties such as underwater antioil-adhesion and antifreezing thanks to their high hydrophilicity and underwater superoleophobicity. The coatings even show the antiadhesion property for crude oil with high viscosity. Therefore, the PDA/PZI-coated meshes are efficient for separating both light oil and crude oil from oil/water mixtures. All these results demonstrate that the one-step strategy is a facile approach to design and exploit the bioinspired PDA/PZI coatings for diverse applications.

Dispersive Solid-Phase Extraction of Polyphenols from Juice and Smoothie Samples Using Hybrid Mesostructured Silica Followed by Ultra-high-Performance Liquid Chromatography-Ion-Trap Tandem Mass Spectrometry

A wormhole-like mesostructured silica was synthesized and modified with octadecylsilane (C18) groups. The resulting hybrid material (HMS-C18) was characterized and evaluated as sorbent for simultaneous extraction of 20 polyphenols from mixed fruit-vegetable juices and smoothies by dispersive solid-phase extraction (dSPE). The samples were first subjected to solvent extraction followed by dSPE procedure. The extraction step was optimized and combined with a reversed-phase ultra-high-performance liquid chromatography method coupled to ion-trap tandem mass spectrometry (UHPLC-IT-MS/MS), which was also optimized. HMS-C18 showed high potential to extract and purify the target analytes, being more effective than commercial C18 amorphous silica. The proposed method was validated for both samples, obtaining average recoveries from 57% to 99% with relative standard deviations lower than 9%. Its applicability in the analysis of commercial mixed fruit-vegetable juices and smoothies revealed mainly contents of rutin, 4-hydroxybenzoic acid, chlorogenic acid, epicatechin, caffeic acid, and naringin in the samples analyzed.

Restricted Access Volatile Supramolecular Solvents for Single-Step Extraction/Cleanup of Benzimidazole Anthelmintic Drugs in Milk Prior to LC-MS/MS

In this work, a restricted access volatile supramolecular solvent (RAM-VOL-SUPRAS) directly synthesized in milk is proposed for the first time for the simultaneous extraction and cleanup of benzimidazole anthelmintic drugs in milk meant for human consumption. The RAM-VOL-SUPRAS was formed by the self-assembly and coacervation of hexanol in tetrahydrofuran induced by the water content in milk. Benzimidazoles legislated by the European Union were quantitatively extracted (80-110%), and proteins were precipitated by the action of THF and the amphiphile; extraction of carbohydrates was avoided by a size exclusion mechanism, and lipids were removed during hexanol evaporation. The analytical methodology was fully validated according to Commission Decision 2002/657/EC. Method detection limits from 0.03 to 0.14 μg L^-1 were well below the maximum residue limits legislated in milk for these drugs, with interday precisions at maximum residue levels below 13%. This novel methodology guarantees a rapid and reliable tool for daily and routine laboratory analyses in the field of food quality control.

Measuring Human Lipid Metabolism Using Deuterium Labeling: In Vivo and In Vitro Protocols

Stable isotopes are powerful tools for tracing the metabolic fate of molecules in the human body. In this chapter, we focus on the use of deuterium (²H), a stable isotope of hydrogen, in the study of human lipid metabolism within the liver in vivo in humans and in vitro using hepatocyte cellular models. The measurement of de novo lipogenesis (DNL) will be focussed on, as the synthesis of fatty acids, specifically palmitate, has been gathering momentum as being implicated in cellular dysfunction, which may be involved in the development of non-alcoholic fatty liver disease (NAFLD). Therefore, this chapter focusses specifically on the use of ²H₂O (heavy water) to measure hepatic DNL.

Microfluidic-based solid phase extraction of cell free DNA

Cell-free DNA (cfDNA) is a liquid biopsy marker that can carry signatures (i.e., mutations) associated with certain pathological conditions. Therefore, the extraction of cfDNA from a variety of clinical samples can be an effective and minimally invasive source of markers for disease detection and subsequent management. In the oncological diseases, circulating tumor DNA (ctDNA), a cfDNA sub-class, can carry clinically actionable mutations and coupled with next generation sequencing or other mutation detection methods provide a venue for effective in vitro diagnostics. However, cfDNA mutational analyses require high quality inputs. This necessitates extraction platforms that provide high recovery over the entire ctDNA size range (50 → 150 bp) with minimal interferences (i.e., co-extraction of genomic DNA), and high reproducibility with a simple workflow. Herein, we present a novel microfluidic solid-phase extraction device (μSPE) consisting of a plastic chip that is activated with UV/O3 to generate surface-confined carboxylic acid functionalities for the μSPE of cfDNA. The μSPE uses an immobilization buffer (IB) consisting of polyethylene glycol and salts that induce cfDNA condensation onto the activated plastic microfluidic surface. The μSPE consists of an array of micropillars to increase extraction bed load (scalable to loads >700 ng of cfDNA) and can be produced at low-cost using replication-based techniques. The entire μSPE can be fabricated in a single molding step negating the need for adding additional extraction supports to the device simplifying production and keeping device and assay cost low. The μSPE allowed for recoveries >90% of model cfDNA fragments across a range of sizes (100-700 bp) and even the ability to extract efficiently short cfDNA fragments (50 bp, >70%). In addition, the composition of the IB allowed for reducing the interference of co-extracted genomic DNA. We demonstrated the clinical utility of the μSPE by quantifying the levels of cfDNA in healthy donors and patients with non-small-cell lung and colorectal cancers. μSPE extracted cfDNA from plasma samples was also subjected to a ligase detection reaction (LDR) for determining the presence of mutations in the KRAS gene for colorectal and non-small cell lung cancer patients.

Rapid monitoring of plant growth regulators in bean sprouts via automated on-line polymeric monolith solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

An automated on-line solid-phase extraction (SPE) following liquid chromatography tandem mass spectrometry was established for the fast determination of plant growth regulator residues in soybean sprout and mung bean sprout. The crude extracted specimens were directly purified on a poly (2-(dimethylamino) ethyl methacrylate-co-ethylene dimethacrylate) monolithic column which was well-defined as the on-line SPE adsorbent. Under the optimized conditions, the developed method gave the linear range of 0.3-50 ng/mL for gibberellin and 2,4-dichlorophenoxyacetic acid, 0.2-50 ng/mL for 4-chlorophenoxyacetic acid, and 0.5-50 ng/mL for 1-naphthaleneacetic acid (r ≥ 0.998). The detection limits (S/N = 3) ranged from 1.0 to 2.5 μg/kg and the recoveries for spiked soybean sprout samples were in the range of 75.0-93.3%. Besides, the total time for one analysis was 16 min. The reusability of the monolith was up to 600 extractions. The proposed process facilitated fully automated SPE and accurate determination in one step with rapidity, simplicity, and reliability. Graphical abstract ᅟ.

An ionic liquid functionalized graphene adsorbent with multiple adsorption mechanisms for pipette-tip solid-phase extraction of auxins in soybean sprouts

A new ionic liquid functionalized graphene-pipette-tip solid-phase extraction method coupled with high-performance liquid chromatography was established for the simultaneous extraction and determination of three auxins in soybean sprouts. The graphene adsorbent, with multiple adsorption mechanisms, was first synthesized by functional modification of pentafluorobenzyl imidazolium bromide ionic liquid through thiol-ene click chemistry. The ionic liquid was applied to prevent the aggregation of graphene; it also imbued graphene with the ability for π-π interactions, ionic exchange, electrostatic interactions, as well as hydrogen bonding (which is stronger than the interaction between water and analytes), by augmenting the adsorption mechanisms between the adsorbent and analytes. Under optimized conditions, linearity was achieved in the ranges 0.03-5.00 µg/g for indole-3-acetic acid and 1-naphthaleneacetic acid and 0.09-5.00 µg/g for 2,4-dichlorophenoxyacetic acid, with a detection limit of 0.004-0.026 µg/g; this adsorbent has been successfully applied for the determination of auxins in soybean sprouts.

Residue investigation of some phenylureas and tebuthiuron herbicides in vegetables by ultra-performance liquid chromatography coupled with integrated selective accelerated solvent extraction-clean up in situ

BACKGROUND

Some trace amounts of urea herbicide residues can be transferred to humans via the food chain, thereby being potentially harmful to human health. The development of a robust analytical methodology for effective sample preparation and simultaneous determination of herbicide residues in vegetable samples is required for achieving food safety.

RESULTS

The diuron-molecularly imprinted polymers (MIPs) synthesized have excellent affinity and high selectivity to phenylureas (monolinuron, isoproturon, diuron and linuron) and tebuthiuron. A novel automated procedure with better selectivity for vegetable sample treatment was developed by integrated matrix solid-phase dispersion-accelerated solvent extraction clean-up in situ. Five herbicides can be baseline separated with runtime down to 5 min by ultra-performance liquid chromatography, and good linearity was obtained with a correlation coefficient (r) of 0.9999. The limit of quantification of the method was in the range of 0.8-2.3 µg kg^-1 . Diuron residue in cherry tomato sample was found to be 40 µg kg^-1 .

CONCLUSION

The developed method has satisfactory selectivity, good linearity, high sensitivity and accuracy as well as speediness, and can ensure rapid selective extraction and sensitive multi-residue analysis at low microgram per kilogram levels of the herbicides in vegetable food. © 2018 Society of Chemical Industry.

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.

Selective detection of chloramphenicol based on molecularly imprinted solid-phase extraction in seawater from Jiaozhou Bay, China

This study highlights an efficient sample pre-treatment method for preconcentration and detection of chloramphenicol in marine water using molecularly imprinted solid-phase extraction (MISPE). Chloramphenicol molecularly imprinted microspheres were prepared and evaluated on the base of morphology, capacity and selectivity. The imprinted microspheres exhibited specific recognition and high retention capability to chloramphenicol and were applied as special solid-phase extraction adsorbents. An off-line MISPE protocol has been optimized and a creative analytical method coupled to HPLC-DAD was successfully developed for the cleanup and determination of chloramphenicol in seawater samples. Method performance was satisfactory with recoveries ranging from 81 to 90% and relative standard deviation (RSD) was <4.93% (n = 3). Accuracy of the method was assessed at three spiking concentration levels and the limit of detection was 5 ng L^-1. Finally, five seawater samples from Jiaozhou Bay of China were determined and the results showed that there was no chloramphenicol detected.

Trace Level Analysis of Sarin and VX in Food Using Normal Phase Silica Gel and Ultra-Performance Liquid Chromatography-Time-of-Flight Mass Spectrometry (UPLC-TOF-MS)

Ultra-Performance Liquid Chromatography/electrospray ionization mass spectrometry was used for the trace level determination of isopropyl methylphosphonofluoridate (Sarin, GB) and ( O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) after extraction from various foods. A method utilizing normal phase silica gel was developed for the sample preparation and extraction of VX and GB from food. The extraction efficiencies of the normal phase silica gel method for VX was compared to those of other commercial solid phase extraction media and was found to be comparable. Sarin was found to be incompatible with both the mixed mode cation exchange (MCX) sorbents and QuEChERS methods that are commercially available but was successful with the normal phase silica gel method. The linear range of quantitation for VX was 0.1-330 ng/mL and for GB was 20-1200 ng/mL. The average recoveries of VX and GB from the various food matrices along with the corresponding relative standard deviations (RSDs) are reported.

Recent Developments of Stir Bar Sorptive Extraction for Food Applications: Extension to Polar Solutes

Stir bar sorptive extraction (SBSE) is a miniaturized and solvent-less sample preparation method for extraction and concentration of organic compounds from aqueous samples. The method is based on sorptive extraction, whereby the solutes are extracted into a polymer, such as polydimethylsiloxane (PDMS), coated on a stir bar. Using an apolar PDMS coating, SBSE provides high recoveries for apolar solutes; however, SBSE recoveries for polar solutes are low. Although several more polar coatings for SBSE were developed, these extraction phases are mostly not compatible with thermal desorption (TD) and/or have inferior performance characteristics related to robustness, bleeding, stability, etc. compared to PDMS. In this perspective, two recently introduced SBSE approaches are described that can be used to extend the applicability of a PDMS coating to more polar solutes: (1) SBSE with freeze concentration [ice concentration linked with extractive stirrer (ICECLES)], which is based on the concentration of analytes by gradually reducing the phase ratio (sample/extraction phase), and (2) SBSE using a solvent-swollen PDMS [solvent-assisted SBSE (SA-SBSE)], which is based on a combination of polarity modification and volume increase by PDMS phase swelling using certain types of solvents while maintaining the original characteristics of the PDMS phase.

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.

Effective Enrichment and Detection of Trace Polycyclic Aromatic Hydrocarbons in Food Samples based on Magnetic Covalent Organic Framework Hybrid Microspheres

The present study reported a facile, sensitive, and efficient method for enrichment and determination of trace polycyclic aromatic hydrocarbons (PAHs) in food samples by employing new core-shell nanostructure magnetic covalent organic framework hybrid microspheres (Fe₃O₄@COF-(TpBD)) as the sorbent followed by HPLC-DAD. Under mild synthetic conditions, the Fe₃O₄@COF-(TpBD) were prepared with the retention of colloidal nanosize, larger specific surface area, higher porosity, uniform morphology, and supermagnetism. The as-prepared materials showed an excellent adsorption ability for PAHs, and the enrichment efficiency of the Fe₃O₄@COF-(TpBD) could reach 99.95%. The obtained materials also had fast adsorption kinetics and realized adsorption equilibrium within 12 min. The eluent was further analyzed by HPLC-DAD, and good linearity was observed in the range of 1-100 ng/mL with the linear correlation being above 0.9990. The limits of detection (S/N = 3) and limits of quantitation (S/N = 10) for 15 PAHs were in the range of 0.83-11.7 ng/L and 2.76-39.0 ng/L, respectively. For the application, the obtained materials were employed for the enrichment of trace PAHs in food samples and exhibited superior enrichment capacity and excellent applicability.

Synthesis and application of selective adsorbent for pirimicarb pesticides in aqueous media using allyl-β-cyclodextrin based binary functional monomers

BACKGROUND

Binary functional monomers, allyl-β-cyclodextrin (allyl-β-CD) and methacrylic acid (MAA) or allyl-β-CD and acrylonitrile (AN), were exploited in a fabrication of molecularly imprinted polymers (MIPs) for selective recognition and large enrichment of pirimicarb from aqueous media.

RESULTS

Special attention was paid to the computational simulation of the imprinting molecular and functional monomers. The morphological characteristics of MIPs made of allyl-β-CD and MAA (M-MAA) were characterised by scanning electron microscopy. The effect of binding capacity of MAA-linked allyl-β-CD MIPs (M-MAA) demonstrated higher efficiency than that of AN-linked allyl-β-CD MIPs (M-AN) when tested in binding specificity. Finally, M-MAA was chosen to run through molecularly imprinted solid-phase extraction (MISPE) to analyse the spiked fresh leafy vegetables of pirimicarb.

CONCLUSION

The present proposed technique is a promising tool for the preparation of the receptors which could recognise pirimicarb pesticide in aqueous media. © 2017 Society of Chemical Industry.