A magnetic imprinted polymer nano-adsorbent with embedded quantum dots and mesoporous carbon for the microextraction of triazine herbicides.

A magnetic molecularly imprinted polymer (MMIP) adsorbent incorporating amino-functionalized magnetite nanoparticles, nitrogen-doped graphene quantum dots and mesoporous carbon (MIP@MPC@N-GQDs@Fe3O4NH2) was fabricated to extract triazine herbicides from fruit juice. The embedded magnetite nanoparticles simplified the isolation of the adsorbent from the sample solution. The N-GQDs and MPC enhanced adsorption by affinity binding with triazines. The MIP layer provided highly specific recognition sites for the selective adsorption of three target triazines. The extracted triazines were determined by high-performance liquid chromatography (HPLC) coupled with diode-array detection (DAD). The developed method exhibited linearity from 1.5 to 100.0 µg L-1 with a detection limit of 0.5 µg L-1. Recoveries from spiked fruit juice samples were in the range of 80.1- 108.4 %, with a relative standard deviation of less than 6.0 %. The developed MMIP adsorbent demonstrated good selectivity, high extraction efficiency, ease of fabrication and use, and good stability.

A magnetic stir bar sorbent of metal organic frameworks, carbon foam decorated zinc oxide and cryogel to enrich and extract parabens and bisphenols from food samples.

A porous composite magnetic stir bar adsorbent was fabricated for the extraction and enrichment of parabens and bisphenols from selected beverage samples. The adsorbent comprised a metal organic framework, carbon foam decorated zinc oxide and magnetic nanoparticles embedded in polyvinyl alcohol cryogel. The porous composite stir bar adsorbent could adsorb parabens and bisphenols via hydrogen bonding, π-π and hydrophobic interactions. In the best conditions, linearity was good from 5.0 to 200.0 µg/L for methyl paraben, ethyl paraben and bisphenol A and from 10.0 to 200.0 µg/L for bisphenol B and butyl paraben. Limits of detection ranged from 1.5 to 3.0 µg/L. The developed composite stir bar was successfully applied to extract and determine parabens and bisphenols in fruit juice, beer and milk. Recoveries ranged from 89.5 to 99.5 % with RSDs lower than 6 %. The developed sorbent and new methodology were evaluated in terms of its green character with satisfactory results.

Fluorescent probe of quantum dots and zinc oxide in a highly selective polymer simultaneously determined florfenicol and sparfloxacin.

A nanocomposite fluorescent probe was fabricated for the simultaneous determination of florfenicol and sparfloxacin based on fluorescence quenching. The probe was synthesized by integrating nitrogen-doped graphene quantum dots (N-GQDs), cadmium telluride quantum dots (CdTe QDs) and zinc oxide nanoparticles (ZnO) into a molecularly imprinted polymer (MIP). The determination was based on the quenching of fluorescence emissions from N-GQDs by florfenicol, detected at 410 nm, and the quenching of fluorescence emissions from CdTe QDs by sparfloxacin, detected at 550 nm. The fluorescent probe was highly sensitive and specific with good linear relationships for florfenicol and sparfloxacin in the range  0.10 to 100.0 µg L-1. The limits of detection for florfenicol and sparfloxacin were 0.06 and 0.10 µg L-1, respectively. The fluorescent probe was used to determine florfenicol and sparfloxacin in food samples and the results agreed well with the results of chromatographic determination. Recoveries of spiked milk, egg and chicken samples reached 93.3-103.4% with good precision (RSD < 6%). The advantages of the nano-optosensor include high sensitivity and selectivity, simplicity, rapidity, convenience, good accuracy and precision.

A composite adsorbent of graphene quantum dots, mesoporous carbon, and molecularly imprinted polymer to extract nonsteroidal anti-inflammatory drugs in milk.

A composite magnetic adsorbent was developed by embedding graphene quantum dots (GQDs), silica-modified magnetite (Fe3O4-SiO2), and mesoporous carbon (MPC) into a molecularly imprinted polymer (GQDs/Fe3O4-SiO2/MPC/MIP). The adsorbent was applied to extract nonsteroidal anti-inflammatory drugs (NSAIDs) in milk. The MIP was formed via a sol-gel copolymerization using flurbiprofen, diflunisal, and mefenamic acid as template molecules, 3-aminopropyltriethoxysilane as a monomer, and tetraethyl orthosilicate as a cross-linker. GQDs and MPC enhanced affinity binding between NSAIDs and the adsorbent through π-π stacking, hydrogen bonding, and hydrophobic interaction. The Fe3O4-SiO2 nanoparticles embedded in the composite adsorbent enabled its rapid isolation from the sample solution. The extracted NSAIDs were quantified by high-performance liquid chromatography and exhibited good linearity from 1.0 to 100.0 µg L-1 for flurbiprofen and 0.5 to 100.0 µg L-1 for diflunisal and mefenamic acid, respectively. The limits of detection ranged from 0.5 to 1.0 µg L-1. Recoveries of NSAIDs from spiked milk samples ranged from 81.4 to 93.7%, with RSDs below 7%. The reproducibility of the fabricated adsorbent was good and in the optimal conditions, the developed adsorbent could be used for up to six extraction-desorption cycles.

A hierarchical porous composite magnetic sorbent of reduced graphene oxide embedded in polyvinyl alcohol cryogel for solvent-assisted-solid phase extraction of polycyclic aromatic hydrocarbons.

A hierarchical porouscomposite magnetic sorbent was fabricated and applied to the dispersive solvent-assisted solid-phase extraction of five polycyclic aromatic hydrocarbons. A sorbent was first prepared by incorporating graphene oxide, calcium carbonate, and magnetite nanoparticles into a polyvinyl alcohol cryogel. The graphene oxide was converted to reduced graphene oxide using ascorbic acid and a hierarchical porous structure was produced by reacting hydrochloric acid with incorporated calcium carbonate to generate carbon dioxide bubbles which created a second network. Before extracting the target analytes, the extraction solvent was introduced into the hierarchical pore network of the sorbent. The extraction was based on the partition between the analytes and introduced extraction solvent and the adsorption of analytes on reduced graphene oxide.The extraction efficiency was enhanced through π-π and hydrophobic interactions between polycyclic aromatic hydrocarbons and reduced graphene oxide and extraction solvent. The extracted polycyclic aromatic hydrocarbons were determined by using high-performance liquid chromatography coupled with a fluorescence detector. The developed method was applied to extract polycyclic aromatic hydrocarbons in disposable diaper, coffee, and tea samples and recoveries from 84.5 to 99.4% were achieved with relative standard deviations below 7%. The developed sorbent exhibited good reproducibility and could be reused for 10 cycles.The developed sorbent exhibited good reproducibility and could be reused for 10 cycles.The developed sorbent exhibited good reproducibility and could be reused for 10 cycles.

In-syringe solid-phase extraction of polycyclic aromatic hydrocarbons using an iron-carboxylate metal-organic framework and hypercrosslinked polymer composite gelatin cryogel-modified cellulose acetate adsorbent.

Cellulose acetate fibers were modified with a gelatin cryogel adsorbent incorporating an iron-carboxylate metal-organic framework and hypercrosslinked polymer composite. The hybrid adsorption materials facilitated the adsorption ability toward polycyclic aromatic hydrocarbons and were entrapped into gelatin cryogel to be hierarchically coated on cellulose acetate fibers which helped to reduce the clogging problem of packed adsorbent. The composite adsorbent was employed as the solid phase of an in-syringe miniaturized solid-phase extraction system. The adsorbent was packed into the needle hub of a disposable syringe and used to extract and preconcentrate polycyclic aromatic hydrocarbons in water sample. The fabricated porous composite adsorbent was characterized and extraction conditions were optimized to achieve the best extraction performance. High-performance liquid chromatography was employed to separate and quantify extracted PAHs. The developed analysis method provided a linear range of 0.020-50 µg L-1 for phenanthrene and benzo(b)fluoranthene, 0.010-50 µg L-1 for pyrene, 0.0020-50 µg L-1 for benzo(a)anthracene, and 0.0050-50 µg L-1 for benzo(a)pyrene and dibenzo(a,h)anthracene. The limits of detection ranged from 0.5 to 5.0 ng L-1. Recoveries ranged from 89 to 98% with RSDs below 7%. The good stability of the adsorbent allowed up to 21 cycles of efficient extraction and desorption.

An optosensor based on a hybrid sensing probe of mesoporous carbon and quantum dots embedded in imprinted polymer for ultrasensitive detection of thiamphenicol in milk.

A hybrid fluorescent sensing probe was developed and used to quantitatively analyse thiamphenicol. The probe was constructed by entrapping mesoporous carbon and CdTe*CdS*ZnS quantum dots in molecularly imprinted polymer. The probe was characterized, and the construction and detection conditions were optimized. In the optimized conditions, the recognition sites of the nanoprobe were ultrasensitive and highly selective toward thiamphenicol. The quantitative analysis of thiamphenicol was based on the fluorescence quenching of the hybrid nanoprobe by thiamphenicol. Fluorescence emission was quenched linearly from 0.10 to 100 µg L-1 with a coefficient of determination (R2) of 0.9979. The limit of detection was 0.04 µg L-1. The accuracy of an optosensor based on the hybrid probe was evaluated by analyzing spiked milk samples. The results obtained were compared with the results of high-performance liquid chromatography (HPLC) analysis. The quantitative analysis of the spiked samples with the optosensor agreed well with HPLC analysis. Recoveries were in the range of 93.5 to 100.1 % with good precision (RSD < 5%). The accuracy, speed and convenience of the developed optosensor make it a powerful tool for the detection of thiamphenicol in milk.

A dumbbell-shaped stir bar made from poly(3,4-ethylenedioxythiophene)-coated porous cryogel incorporating metal organic frameworks for the extraction of synthetic phenolic antioxidants in foodstuffs.

A dumbbell-shaped stir bar adsorbent of MIL-101 entrapped in PVA cryogel coated with poly(3,4-ethylenedioxythiophene) was fabricated to extract synthetic phenolic antioxidants in foodstuffs. The interconnected porous of cryogel allowed the entrapment of MIL-101 and enhanced the surface areas of poly(3,4-ethylenedioxythiophene) coating which facilitated multiple adsorptions. The fabricated adsorbent was characterized and measured the adsorption capacities for synthetic phenolic antioxidants. Extraction efficiency was optimized by evaluating the effect of adsorbent compositions, extraction time, stirring speed, sample pH, desorption conditions, sample volume and ionic strength. The analysis of extracted synthetic phenolic antioxidants was carried out using high performance liquid chromatography. The developed analysis method provided a wide linear range of 0.20 - 200 µg kg-1 for butylated hydroxyanisole and 0.50 - 200 µg kg-1 for tert­butylhydroquinone and butylated hydroxytoluene. The limits of detection were between 0.05 and 0.15 µg kg-1. The developed stir bar adsorbent was utilized to extract these three synthetic phenolic antioxidants from juice, milk, infant formula and coffee creamer. Recoveries ranged from 87 to 101% with RSDs below 7%. The developed composite stir bar adsorbent was convenient to use, and good physical and chemical stability allowed efficient extraction for 12 extraction cycles.

A nanocomposite adsorbent of metallic copper, polypyrrole, halloysite nanotubes and magnetite nanoparticles for the extraction and enrichment of sulfonamides in milk.

A composite adsorbent composed of metallic copper (Cu), polypyrrole (PPy), halloysite nanotubes (HNTs) and magnetite nanoparticles (Fe3O4) was developed to extract and enrich sulfonamides by dispersive magnetic solid phase extraction. The composite could adsorb sulfonamides via hydrogen bonding and hydrophobic, π-π and π-electron-metal interactions. The extraction conditions were optimized and the developed composite adsorbent was characterized and provided a large surface area that enhanced extraction efficiency for sulfonamides. Coupled with high performance liquid chromatography, the adsorbent was used to quantitatively determine sulfonamides found in milk samples. The response of the developed method exhibited linearity from 5.0 to 150.0 µg kg-1 for sulfathiazole, and from 2.5 to 100.0 µg kg-1 for sulfamerazine, sulfamonomethoxine and sulfadimethoxine. Limits of detection were between 2.5 and 5.0 µg kg-1. Recoveries of sulfonamides in milk samples ranged from 83.0 to 99.2% with RSDs lower than 6%. The developed composite adsorbent showed good reproducibility and reusability.

A nanohybrid magnetic sensing probe for levofloxacin determination integrates porous graphene, selective polymer and graphene quantum dots.

A nanohybrid magnetic fluorescent sensing probe was designed and fabricated for ultrasensitive and selective determination of levofloxacin. The probe integrated porous graphene (PGr), magnetite (Fe3O4) nanoparticles and graphene quantum dots (GQDs) into selective molecularly imprinted polymer (MIP). The developed probe was sensitive, selective, and its binding ability enriched levofloxacin in complex samples. The fabrication strategy was evaluated to achieve the best performance and the synthesized sensing probe was characterized. In the best condition, the fluorescence emission of the probe was quenched linearly from 0.10 to 25.0 µg L-1 of levofloxacin and the limit of detection was 0.03 µg L-1. The quenching of fluorescence was not affected by the analog compounds ciprofloxacin, lomefloxacin, marbofloxacin and sarafloxacin. The imprinting factor of the developed nanohybrid sensing probe was 4.26. The developed probe was utilized to detect levofloxacin in milk and recoveries between 91.8 % and 100.5 % were achieved with RSDs <6.5 %. Analysis with the optosensor provided the same results as HPLC analysis but the optosensor was more sensitive, less expensive, simpler and more rapid.

Nanohybrid magnetic composite optosensing probes for the enrichment and ultra-trace detection of mafenide and sulfisoxazole.

Nanohybrid magnetic optosensing probes were designed and fabricated to enrich and detect ultra-trace levels of mafenide and sulfisoxazole simultaneously. The probes combined the high affinity of MIL-101 and the sensitivity of graphene quantum dots (GQDs) and cadmium telluride quantum dots (CdTe QDs) with the selectivity and rapid separation provided by a magnetic molecularly imprinted polymer (MMIP). Since the MIL101-MMIP-GQD and MIL101-MMIP-CdTe QD probes produced high fluorescence emission intensities at 435 and 572 nm, respectively, mafenide and sulfisoxazole could be simultaneously detected. Quantitative analysis was based on fluorescence quenching produced by binding between target molecules and imprinted recognition cavities. In the optimal experimental condition, emission intensity was quenched linearly with increasing analyte concentration from 0.10 to 25.0 µg L-1. Limit of detection was 0.10 µg L-1 for mafenide and sulfisoxazole. The developed optosensor was applied to detect ultra-trace amounts of mafenide and sulfisoxazole in bovine milk. Recoveries of mafenide and sulfisoxazole in spiked bovine milk ranged from 80.4 to 97.9% with RSDs <5% and the analysis results agreed well with HPLC analysis. The proposed probes provided excellent sensitivity, selectivity, ease and convenience of use.

Nano-optosensor based on titanium dioxide and graphene quantum dots composited with specific polymer for cefazolin detection.

An optosensor using nanocomposite probes was fabricated for the detection of trace cefazolin. The nanoprobes utilized the high affinity of titanium dioxide, the good optical properties of graphene quantum dots and the good selectivity of molecularly imprinted polymer. The integration of these materials produced a rapid, highly sensitive optosensor with excellent selectivity for cefazolin detection. The fluorescence intensity of the nanocomposite probes was quenched when cefazolin re-bound with the imprinted recognition cavities of the nanoprobes. The fabricated nanoprobe exhibited a good linearity for cefazolin from 0.10 to 10.0 µg L-1 with a limit of detection of 0.10 µg L-1. The imprinting factor of the nanoprobe was 10.6 and selectivity for cefazolin was not affected by the analogue structures of cephalexin, cefatriaxone, cephradine, cefaperazone and ceftazidime. This nano-optosensor probe successfully detected cefazolin in milk and recoveries were between 85.0 and 97.4 % with RSDs less than 5.0 %. The results of analysis with nano-optosensor were in good agreement with HPLC analysis. The fabrication strategy of the nanocomposite probe can be modified for the measurement of other toxic compounds.

Solvent-assisted dispersive liquid-solid phase extraction of organophosphorus pesticides using a polypyrrole thin film-coated porous composite magnetic sorbent prior to their determination with GC-MS/MS.

A porous composite magnetic sorbent was developed and used as a solid phase for the solvent-assisted preconcentration of organophosphorus pesticides. The hierarchical porous composite sorbent was composed of polypyrrole thin film coated on the surface of porous alginate beads with embedded magnetite nanoparticles. The pores in the alginate hydrogel beads were produced by carbon dioxide bubbles from the reaction of incorporated calcium carbonate with hydrochloric acid. The porous network was filled with dichloromethane to assist extraction. The fabricated porous composite sorbent was characterized and sorbent fabrication and extraction conditions were optimized to obtain the best extraction performance. The developed sorbent was coupled with GC-MS/MS to determine organophosphorus pesticides in fruit juices and vegetable. Under optimized condition, the developed method provided good linear range of 0.03-200 µg L-1 for dichlorvos, malathion, and fenthion, and 0.075-200 µg L-1 for mevinphos, dimethoate, and parathion methyl, respectively. Limits of detection were in the range 0.010 to 0.025 µg L-1. This method exhibited good relative recoveries in the range 84 to 99% and RSDs lower than 8%. The good stability of the sorbent enabled up to eight cycles of reuse.Graphical abstract.

A nanocomposite probe of graphene quantum dots and magnetite nanoparticles embedded in a selective polymer for the enrichment and detection of ceftazidime.

Graphene quantum dots and magnetite nanoparticles were embedded in molecularly imprinted polymer (GQDs@Fe3O4/MIP) to develop a magnetic nanocomposite fluorescent probe that could enrich and detect trace ceftazidime in milk in conjunction with an optosensor. Graphene quantum dots enhanced the sensitivity of the optosensor and the specificity of the molecularly imprinted polymer reinforced the selectivity of the nanocomposite probe. The incorporated magnetite nanoparticles increased enrichment of the target analyte so that a smaller volume of detecting solution could be used. The developed probe was characterized and the preparation procedure and detection conditions were optimized. In the optimum conditions, linearity was in the range of 0.10-10.0 µg L-1 and the limit of detection was 0.05 µg L-1. The developed system was utilized to detect ceftazidime in milk samples. Recoveries were in the range of 90.7-99.2% with RSD below 6% and the obtained results agreed well those obtained with chromatographic technique. However, the developed optosensor exhibited better sensitivity, was faster and easier to operate and can be modified for the enrichment and detection of other target analytes in various sample matrices.

Solid-phase extraction based on MIL-101 adsorbent followed by gas chromatography tandem mass spectrometry for the analysis of multiclass organic UV filters in water.

A metal organic framework material MIL-101 was developed as an effective solid-phase extraction adsorbent for the extraction of eleven UV filters compounds. The MIL-101 adsorbent was packed into a polypropylene cartridge and connected at the outlet tip with the Visiprep™ vacuum manifolds allowing process up to 12-port SPE samples, simultaneously. The extracted UV filters were quantified by gas chromatography-tandem mass spectrometry. Several parameters affecting the extraction efficiency of the target analytes, i.e. desorption conditions, sample pH, the addition of salt and sample volume were optimized by ANOVA analysis followed by a multifactorial design. The sample breakthrough volume of the developed method was also evaluated. The SPE-GC-MS/MS method was validated in terms of linearity (R2 ≥ 0.9973), accuracy (with satisfactory recovery from 82% to 105%), precision (relative standard deviation of less than 10%) and limits of detection ranging from 1.0 to 11.7 ng L-1. The validated method was successfully applied for the extraction and quantification of the target UV filters in different types of water samples, including lake, river, seawater and swimming pool waters. The most often found UV filters were octocrylene, 4-methylbencylidene camphor and homosalate that also came out with the highest concentrations, up to 4000 ng L-1, particularly in swimming pool waters.

Development of doubly porous composite adsorbent for the extraction of fluoroquinolones from food samples.

A doubly porous microcomposite polyaniline/graphene oxide/octadecyl-bonded silica magnetite (PANI/GOx/C18-SiO2-Fe3O4) alginate adsorbent was developed and employed to extract fluoroquinolones. The Fe3O4 facilitated rapid and convenient for the separation of the adsorbent from sample solutions. The double porosity of the alginate hydrogel enhanced the surface area of the polyaniline coating. The developed method exhibited good linearity of 0.0010-50 µg L-1 for danofloxacin; 0.0050-50 µg L-1 for norfloxacin, ciprofloxacin and enrofloxacin; and 0.010-50 µg L-1 for sarafloxacin and difloxacin. The limits of detection were between 0.001 and 0.010 µg L-1 with RSD below 9.0%. The PANI/GOx/C18-SiO2-Fe3O4 adsorbent was utilized to extract fluoroquinolones from honey, milk and egg samples and satisfactory extraction recoveries were achieved ranged from 80 to 98%. The developed adsorbent has good stability which can be reused up to 7 times, is simple to prepare and convenient to use for the extraction fluoroquinolones.

A nanosorbent consisting of a magnetic molecularly imprinted polymer and graphene oxide for multi-residue analysis of cephalosporins.

A nanosorbent composed of magnetite nanoparticles, graphene oxide and a molecularly imprinted polymer (Fe3O4@SiO2-NH2/GOx/MIP) was synthesized and applied to simultaneous extraction of cephalexin, cefazolin and cefoperazone from milk. The use of magnetite nanoparticles enables fast extraction by using an external magnet. The use of graphene oxide increases extraction affinity, and the MIP improves selectivity. Extraction efficiency was optimized by investigating the effects of the template-to-monomer and cross-linker ratios, the desorption condition, extraction time, salting-out effect, stirring rate, sample volume and amount of adsorbent. The cephalosporins were quantified by using HPLC. Under optimum condition, the linear range of the method extends from 2.5 to 100 µg L-1 for cephalexin and cefazolin, and from 5.0 to 100 µg L-1 for cefoperazone. The limits of detection are 2.5 µg L-1 for cephalexin and cefazolin, and 5 µg L-1 for cefoperazone. The adsorbent was applied to the extraction of cephalosporins from milk, with recoveries in a range from 80.2 to 111.7% and with RSDs of <8.5%. Graphical abstractSchematic representation of a nanocomposite adsorbent consisting of magnetic molecularly imprinted polymer and graphene oxide (GOx). Integrating of magnetite nanoparticles, GOx and high specificity of MIP, the method exhibited a rapid, high extraction efficiency, good selectivity for multi-residue analysis of cephalosporins.

A nanocomposite probe of polydopamine/molecularly imprinted polymer/quantum dots for trace sarafloxacin detection in chicken meat.

A nanooptosensor based on the fluorescence quenching of a composite probe was fabricated for the detection of sarafloxacin. The components of the nanocomposite fluorescent probe were a high affinity material of polydopamine polymer (PDA), a selective material of molecularly imprinted polymer (MIP), and optically sensitive quantum dots (QDs). The developed nanocomposite fluorescent probe exhibited excellent selectivity and sensitivity for sarafloxacin. The molecularly imprinted polymer had an imprinting factor (IF) of 8.18 and produced a probe that quenched fluorescence more effectively than a non-imprinted polymer (NIP) probe. The emission intensity of the MIP probe was linearly quenched by sarafloxacin over a range of 0.10 to 15.0 µg L-1 with a determination coefficient (R2) of 0.9966. The developed nanooptosensor had a limit of detection of 0.05 µg L-1. The optosensor detected sarafloxacin in chicken meat samples with recoveries ranging from 82.8 to 99.1% with an RSD below 3%. The found concentrations in spiked samples were compared well with recoveries obtained by HPLC method of detection. This developed nanooptosensor is simple to operate and cost-effective and the analytical procedure is rapid. Graphical abstract.

A nanocomposite fluorescent probe of polyaniline, graphene oxide and quantum dots incorporated into highly selective polymer for lomefloxacin detection.

A nanocomposite fluorescent probe based on fluorescence quenching was fabricated and utilized for the detection of lomefloxacin. The fabricated probe integrated the high sensitivity of quantum dots, the excellent selectivity of molecularly imprinted polymer and the high adsorption affinity of graphene oxide and polyaniline. The probe exhibited good sensitivity, high specificity, and rapidity for lomefloxacin monitoring. Fluorescence emission was reduced linearly by lomefloxacin from 0.10 to 50.0 µg L-1 and the probe exhibited a low limit of detection of 0.07 µg L-1. The nanooptosensor successfully detected lomefloxacin in milk, chicken meat and egg samples. Recoveries were obtained in the range of 81.5-99.6% and the RSDs were below 7%. The results of this method agreed well with results of HPLC but provided higher sensitivity. This easily fabricated nanocomposite probe could be developed into a highly sensitive and selective optosensor to detect other organic compounds in various complex samples.