Restricted Access Media Research Articles

Restricted-Access Media Column Switching Online Solid-Phase Extraction UHPLC-MS/MS for the Determination of Seven Type B Trichothecenes in Whole-Grain Preprocessed Foods and Human Exposure Risk Assessment.

With increasing health awareness and the accelerating pace of life, whole-grain prepared foods have gained popularity due to their health benefits and convenience. However, the potential risk of type B trichothecene toxins has also increased, and these mycotoxins in such foods are rarely regulated. In this study, a quantitative method combining a single-valve dual-column automatic online solid-phase extraction system with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed for the first time using restricted-access media columns. This method can simultaneously determine trace residues of seven type B trichothecenes within 15 min. The method is convenient, sensitive (limit of detection and quantification of 0.05-0.6 μg/kg and 0.15-2 μg/kg, respectively), accurate (recovery rates of 90.3%-106.6%, relative standard deviation < 4.3%), and robust (>1000 times). The established method was applied to 160 prepared food samples of eight categories sold in China. At least one toxin was detected in 70% of the samples. Whole-wheat dumpling wrappers had the highest contamination rate (95%) and the highest total content of type B trichothecenes in a single sample (2077.3 μg/kg). Exposure risk assessment indicated that the contamination of whole-grain prepared foods has been underestimated. The total health risk index of whole-wheat dumpling wrappers, which are susceptible to deoxynivalenol, reached 136.41%, posing a significant threat to human health. Effective measures urgently need to be taken to control this risk.

Evaluation of restricted access media for the purification of cell culture-derived Orf viruses.

Recently, multimodal chromatography using restricted access media (RAM) for the purification of nanoparticles, such as viruses has regained increasing attention. These chromatography resins combine size exclusion on the particle shell and adsorptive interaction within the core. Accordingly, smaller process-related impurities, for example, DNA and proteins, can be retained, while larger product viruses can pass unhindered. We evaluated a range of currently available RAM, differing in the shells' pore cut-off and the core chemistry, for the purification of a cell culture-derived clarified model virus, namely the Orf virus (ORFV). We examined impurity depletion and product recovery as relevant criteria for the evaluation of column performance, as well as scale-up robustness and regeneration potential for evaluating a multiple use application. The results indicate that some columns, for example, the Capto Core, enable both a high DNA and protein removal, while others, for example, the Monomix Core 60 (MC60), are more suitable for DNA depletion. Furthermore, column regeneration is facilitated by using columns with larger shell pores (5000vs. 700kDa) and weaker binding interactions (anion exchange vs. multimodal). According to these findings, the choice of RAM resins should be selected according to the respective feed sample composition and the planned number of application cycles.

Comparison of nanofibers, microfibers, nano/microfiber graphene doped composites, molecularly imprinted polymers, and restricted access materials for on-line extraction and chromatographic determination of citrinin, zearalenone, and ochratoxin A in plant-based milk beverages

Several advanced sorbents for on-line extraction followed by chromatographic determination of citrinin, zearalenone, and ochratoxin A in a complex matrix of plant-based beverages from oat and rice milk have been compared. Twelve types of the fibrous sorbents, including polyethylene and polypropylene microfibers, polycaprolactone microfibers/polyvinylidene difluoride nanofibers composite, poly(3-hydroxybutyrate) microfibers, poly(3-hydroxybutyrate) microfibers/polypropylene microfibers composite, polycaprolactone nanofibers, polycaprolactone nanofibers doped with 7.7, 20.2, and 30.7% graphene, polyacrylonitrile nanofibers, polyurethane nanofibers, and polyamide 6 nanofibers were compared in terms of extraction recovery and cleanup efficiency with both the commercial restricted access media sorbent RP-18 ADS (RAM) and molecularly imprinted polymers (MIP). The MIP sorbent was a mixture prepared from commercial Affinimip selective for ochratoxin A and zearalenone, and home-made MIP for citrinin (1:1:1). The polymer fibers and the MIP mixture were filled in a cartridge similar in size to the commercial RAM column and the clean-up step as well as the subsequent chromatographic separation were optimized. The HPLC separation of mycotoxins was carried out using Kinetex Biphenyl (150 × 4.6 mm, core–shell particle size 5 µm) analytical column followed by fluorescence detection. The excitation and emission wavelengths were set at 335/497 nm for citrinin and ochratoxin A, and 270/458 nm for zearalenone, respectively. The mobile phase used for the gradient elution of the mycotoxins consisted of 0.5% aqueous formic acid and acetonitrile. The zearalenone contaminations found in plant-based beverages ranged from 9.5 to 14.6 μg L−1 and were within the tolerable limit defined by the European Union.

Restricted access medium magnetic molecularly imprinted polymers: Validation of their suitability as an effective quantitation tool against phthalates in food products packaged in plastic

A highly effective approach has been established for the selective identification and isolation for a list of phthalates (PTHs: e.g., dimethyl phthalate, dipropyl phthalate, dibutyl phthalate, benzyl butyl phthalate, and dioctyl phthalate) based on restricted access medium magnetic molecularly imprinted polymer (RAM-MMIP). The RAM-MMIP has been synthesized by a surface imprinting method using: (i) Fe3O4@SiO2 as the support material, (ii) diethyl phthalate and dicyclohexyl phthalate as dual dummy templates, and (iii) (3-glycidyloxypropyl)trimethoxysilane as the silane coupling agent to impart hydrophilic properties to the polymer. The adsorption kinetic and isotherm studies confirm the good match of experimental results with the Langmuir and pseudo-second order model. The RAM-MMIP exhibits great selectivity toward PTHs and recyclability for up to seven cycles. It has been applied for the extraction of PTHs from foods packaged in plastic (bottled water, juice, and milk samples) via magnetic solid phase extraction coupled with gas chromatography/mass spectrometry (recovery: 88.53–121.57 % (RSD% = 1.30–5.15 %) and LOD (0.01–0.03 ng/mL)). The overall results of this study suggest that the RAM-MMIP is a highly recommendable option for efficient extraction and quantitation of PTHs.

Nanoporous Ethylenediamine-Functionalized Metal–Organic Framework MIL-101 for the Removal of Proteins and Antipsychotic Drugs from Serum Samples

The development of functional materials for efficient protein removal and antipsychotic drug extraction in biological samples is attracting great interest. In this study, a nanoscale ethylenediamine-functionalized chromium-based metal–organic framework (MOF) (MIL-101-ED) was designed, synthesized, and applied for the one-step removal of proteins and the extraction of antipsychotic drugs in serum samples. The introduction of ethylenediamine in the MIL-101 nanoparticle (NP), in which amino and carbon chains can enhance the hydrogen-bond interaction and π–π interaction between functionalized MOFs and antipsychotic drugs, i.e., risperidone, etc. The antipsychotic drugs were ionized and amino groups were protonated at pH = 3, due to electrostatic interaction, and the negatively charged drugs were adsorbed on the surface or even entered the pores of MOFs. The adsorption efficiencies of the six kinds of drugs ranged from 80.1 to 101.4%. Owing to the exclusion action, proteins were excluded from MIL-101-ED and the exclusion rate ranged from 91.9 to 94.0%. Furthermore, MIL-101-ED can be easily regenerated and reused four times without a significant reduction in the protein exclusion rate and adsorption capacity. Coupled with high-performance liquid chromatography–diode array detection (HPLC–DAD) strategy, the application of MIL-101-ED for extracting the antipsychotic drugs and their metabolites in serum samples was developed. The recoveries of antipsychotic drugs and their metabolites in serum ranged from 83.2 to 110.8%, and the related detection limits were all <5.55 ng mL–1. Compared to the traditional extraction methods, the pretreatment steps of MIL-101-ED have the advantages of easy operation and reducing the environmental pollution. Here, we propose that MIL-101-ED, as a kind of restricted access media nanophase material, can be applied to extract antipsychotic drugs in serum samples.

Comparing adsorption performance of microfibers and nanofibers with commercial molecularly imprinted polymers and restricted access media for extraction of bisphenols from milk coupled with liquid chromatography

Advanced solid phase extraction (SPE) fibrous sorbents including polyethylene, polypropylene poly (hydroxybutyrate), and polyamide 6 nanofibers, polycaprolactone microfibers/nanofibers, polycaprolactone microfibers/polyvinylidene difluoride nanofibers, and poly (hydroxybutyrate) microfibers/polypropylene microfibers composites, as well as commercial molecularly imprinted polymers and restricted access media sorbent were compared in terms of bisphenols extraction from milk and their clean-up efficiency. Three on-line SPE-HPLC methods were completely validated for the extraction and detection of bisphenols A, AF, C, A diglycidyl ether, and F diglycidyl ether in bovine milk. Polycaprolactone composite nanofibers compared favorably to restricted access media, enabled excellent clean-up of bisphenols from the proteinaceous matrix, and yielded recoveries 98.0–124.5% and 93.0–115.0%, respectively, with RSD less than 10%. Total analysis time including on-line SPE step lasted only 12 min, which represents a significant reduction in time compared with previously reported as well as official European Union and AOAC methods defined for the determination of bisphenols in various matrices.

A scalable, integrated downstream process for production of a recombinant measles virus-vectored vaccine

Purification of very large and complex, enveloped viruses, such as measles virus is very challenging, it must be performed in a closed system because the final product cannot be sterile filtered and often loss of virus titer and poor product purity has been observed. We developed a purification process where the clarified and endonuclease treated culture supernatant is loaded on a restricted access chromatography medium where small impurities are bound and the virus is collected in the flow-through, which is then concentrated, and buffer exchanged by ultra/diafiltration. Up to 98.5% of host cell proteins could be captured by direct loading of clarified and endonuclease treated cell culture supernatant. Reproducible process performance and scalability of the chromatography step were demonstrated from small to pilot scale, including loading volumes from 50 mL up to 9 L. A 10-fold virus concentration was achieved by the ultrafiltration using a 100 kDa flat-sheet membrane. The order of individual process steps had a large impact on the virus infectivity and total process yields. The developed process maintained virus infectivity and is twice as fast as the traditional process train, where concentration is performed before loading on the chromatography column. Capturing impurities by the restricted access medium makes it a platform purification process with a high flexibility, which can be easily and quickly adapted to other vectors based on the measles virus vector platform.

Preparation and performance analysis of monodisperse glycidyl methacrylate modified restricted access media‐imprinted materials

Using monodisperse poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) as the matrix, and pefloxacin template molecules, a novel restricted-access medium molecularly imprinted polymers with Bovine serum albumin crosslinked on its surface was prepared through reversible addition-fragmentation chain-transfer polymerization. Then, the obtained material was employed in dispersive solid-phase extraction to analyze the fluoroquinolones in untreated egg samples by high-performance liquid chromatography-ultraviolet detection. Adsorption performance revealed a good binding amount (40.72mg/g), fast binding kinetics (25min), satisfactory selectivity, and good ability to eliminate matrix interference. The reusability experiments indicated the materials have good reusable performance after repetition. Under the optimized conditions, restricted access media-molecularly imprinted polymers-dispersive solid-phase extraction was combined with high-performance liquid chromatography-ultraviolet to enrich fluoroquinolones in untreated eggs, good limit of detection (1.31-3.15 μg/L) and high recovery (89.5-96.8%) were obtained. The results showed that the prepared restricted-access material is promising for the direct detection of antibiotics in complex samples.

Polycaprolactone Composite Micro/Nanofibrous Material as an Alternative to Restricted Access Media for Direct Extraction and Separation of Non-Steroidal Anti-Inflammatory Drugs from Human Serum Using Column-Switching Chromatography.

Application of the poly-ɛ-caprolactone composite sorbent consisting of the micro- and nanometer fibers for the on-line extraction of non-steroidal anti-inflammatory drugs from a biological matrix has been introduced. A 100 μL human serum sample spiked with ketoprofen, naproxen, sodium diclofenac, and indomethacin was directly injected in the extraction cartridge filled with the poly-ɛ-caprolactone composite sorbent. This cartridge was coupled with a chromatographic instrument via a six-port switching valve allowing the analyte extraction and separation within a single analytical run. The 1.5 min long extraction step isolated the analytes from the proteinaceous matrix was followed by their 13 min HPLC separation using Ascentis Express RP-Amide (100 × 4.6 mm, 5 µm) column. The recovery of all analytes from human serum tested at three concentration levels ranged from 70.1% to 118.7%. The matrix calibrations were carried out in the range 50 to 20,000 ng mL−1 with correlation coefficients exceeding 0.996. The detection limit was 15 ng mL−1, and the limit of quantification corresponded to 50 ng mL−1. The developed method was validated and successfully applied for the sodium diclofenac determination in real patient serum. Our study confirmed the ability of the poly-ɛ-caprolactone composite sorbent to remove the proteins from the biological matrix, thus serving as an alternative to the application of restricted-access media.

Selective Removal of Florfenicol from Fetal Bovine Serum by Restricted Access Media–Magnetic Molecularly Imprinted Polymers

Selective Removal of Florfenicol from Fetal Bovine Serum by Restricted Access Media–Magnetic Molecularly Imprinted Polymers

On-line solid-phase extraction of pharmaceutical compounds from wastewater treatment plant samples using restricted access media in column-switching liquid chromatography-tandem mass spectrometry

An on-line solid phase extraction using a lab-made restricted access media (RAM) was developed as sample preparation procedure for determination of the pharmaceutical compounds caffeine (CAF), carbamazepine (CBZ), norfloxacin (NOR), ciprofloxacin (CIP), fluoxetine (FLX) and venlafaxine in wastewater treatment plant samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS). This method is suitable for use in routine of analysis, avoiding cross-contamination and requiring only a small sample volume (50 µL), with minimal handling.The method was validated according to international guidelines. The chromatographic efficiency was evaluated using peak resolution and asymmetry parameters. Carryover was also evaluated, in order to ensure reliability of the analysis and the ability to reuse the cartridge. Satisfactory linearity (r2 > 0.99) was obtained for all the compounds. The intra- and inter-day precision values were lower than 5.79 and 14.1%, respectively. The limits of detection ranged from 0.01 to 3 µg L−1 and the limits of quantification were from 0.1 to 5 µg L−1. The method was applied to 20 environmental wastewater samples, with caffeine being the most widely detected compound, at the highest concentration of 392 µg L−1, while other compounds were detected in fewer samples at lower concentrations (up to 9.60 µg L−1). The lab-made modification is a cheaper option for on-line sample preparation, compared to commercially available on-line SPE cartridges and RAM columns. Moreover, a high-throughput procedure was achieved, with an analysis time of 16 min including sample preparation and chromatographic separation. The same RAM column was applied over 200 injections including method optimization, validation and application in wastewater samples without loss of analytical response.

The role of pKa, log P of analytes, and protein matrix in solid-phase extraction using native and coated nanofibrous and microfibrous polymers prepared via meltblowing and combined meltblowing/electrospinning technologies

Effect of physicochemical properties including dissociation constant (pKa) and partition coefficient (log P) of the compounds on their extraction efficiency in sample preparation using fibrous polymer sorbents has been demonstrated. Poly-ε-caprolactone as meltblown/electrospun composite fibers, and polypropylene, polyethylene, poly(3-hydroxybutyrate), poly(lactic acid), and polyamide 6 in the meltblown fiber format were used as sorbents in solid-phase extraction. In addition, the polycaprolactone fibers were coated with dopamine, dopamine combined with heparin, and tannin, respectively, to modify their extraction properties. These fibers that were not yet used for extractions and the unique combination of sorbents and analytes significantly extends the scope of nanofibrous extraction. The extraction efficiency was determined using model pharmaceuticals including acetylsalicylic acid, moxonidine, metoprolol, propranolol, propafenone, diltiazem, atorvastatin, and amiodarone. These model compounds displayed the widest differences in both pKa and log P values. The extraction efficiency of some of the fibers reached 96.64%. Coating of polycaprolactone fibers with dopamine significantly improved extraction efficiency of slightly retained metoprolol while moxonidine was not retained on any sorbent. The fibrous sorbents were also tested for extraction of pharmaceuticals in bovine serum albumin and human serum, respectively, to demonstrate their capability to extract them from a complex protein-containing matrix. The clean-up efficiency of our fibers was compared with that of a commercial restricted access media (RAM) C-18 alkyl-diol silica column. Our technique is in accordance with the requirements of modern sample preparation techniques.

Preparation of monodisperse, restricted-access, media-molecularly imprinted polymers using bi-functional monomers for solid-phase extraction of sarafloxacin from complex samples

Monodisperse restricted-access media bi-functional monomers with molecularly imprinted polymers (RAM-MIPs) were constructed using surface-initiated atom transfer radical polymerization. They were used as solid-phase extraction (SPE) adsorbents to enrich sarafloxacin (SAR) residues from egg samples, and influences on their performance were investigated. Optimum synthesis of RAM-MIPs was achieved by combining a bi-functional monomer (4-vinylpyridine-co-methacrylic acid, 1:3) with an 8:1:32:8 ratio of a template molecule, cross-linker, and restricted-access functional monomer. The SAR imprinting factor of RAM-MIPs was 6.05 and the selectivity coefficient between SAR and other fluoroquinolones was 1.86–2.64. Compared with traditional MIPs, the RAM-MIPs showed better SAR enrichment and selectivity during extraction of a complex protein-containing solution. Empty SPE cartridges were filled with RAM-MIP microspheres as SPE adsorbents. The limit of quantitation for SAR was 4.23 ng g−1 (signal-to-noise ratio = 10) and the mean SAR recovery from spiked egg samples was 94.0–101.3%. Intra-day and inter-day relative standard deviations were 1.1–9% and 1.5–3.3%, respectively.

Synthesis of Molecularly Imprinted Polymers by Two-Step Swelling and Polymerization.

Synthesis of a molecularly imprinted polymer (MIP) by two-step swelling and polymerization is described. Monodisperse, spherical MIP particles, whose diameters are ca. 5-9μm, are prepared using a polystyrene particle as a shape template and dibutyl phthalate as an activating solvent. The obtained MIPs are suitable for separation media in liquid chromatography or solid-phase extraction media. Procedures for synthesis of MIPs and restricted access media (RAM)-MIP, packing of MIPs and RAM-MIPs, and application of MIPs and RAM-MIPs for selective separation and extraction of a target compound(s) are described.

Theoretical performance of multiple size-exclusion chromatography columns connected in series

The fundamental relationships are derived for the retention, peak width, and peak capacity of non-retained polymers eluting from multiple standard size-exclusion chromatography (SEC) columns connected in series. The standard SEC columns may have different dimensions and are packed with particles having distinct average particle diameters (APDs) and average mesopore sizes (AMSs). The performances (peak capacity, local resolution power, and sensitivity) of three standard SEC columns connected in series (called a tri-SEC column) packed with bridged-ethylene-hybrid (BEH) fully porous particles (FPPs) having three different APDs (1.7, 2.5, and 3.5 μm) and AMSs (200, 450, and 900 Å, respectively) are calculated as a function of the applied flow rate and size of polystyrene standards. Irrespective of the APD and AMS, the present investigation assumes isomorphological materials relative to the mesopore space of the three different BEH particles. The advantage of a 15 cm long tri-SEC column over a single reference SEC column (APD=3.5 μm, AMS=900 Å), which generates the same back pressure and separation window as those of the tri-SEC column, is expected at flow rates larger than the optimum flow rate generating the maximum peak capacity. The calculations predict a significant relative increase of the peak capacity (from +25% to +85%), resolution of small molecules (from +75% to +225%), and of the detection limit of intermediate size (from +15% to +70%) and largest polymers (from +25 to +110%). This is explained by 1) the exclusion of the largest polymers from the internal volume of the particles having the smallest mesopores (restricted access media) and 2) the minimum dispersion along the columns packed with the smallest particle sizes in the tri-SEC column. The main benefit of multi-SEC columns is to easily adjust the desired pore size distribution by properly selecting the lengths of each individual SEC column. The user can then control the pore size distribution for any specific separation problem. A potential application is theoretically demonstrated for the fast purification of monoclonal antibodies from metabolites, host cell proteins, aggregated forms, and from virus-like particles.

Development of an analytical method to quantify pharmaceuticals in fish tissues by liquid chromatography-tandem mass spectrometry detection and application to environmental samples

A sensitive multiresidue method was developed to quantify 35 pharmaceuticals and 28 metabolites/transformation products (TPs) in fish liver, fish fillet and fish plasma via LC-MS/MS. The method was designed to cover a broad range of substance polarities. This objective was realized by using non-discriminating sample clean-ups including separation technique based on size exclusion, namely restricted access media (RAM) chromatography. This universal clean-up allows for an easy integration of further organic micropollutants into the analytical method. Limits of quantification (LOQ) ranged from 0.05 to 5.5 ng/mL in fish plasma, from 0.1 to 19 ng/g d.w. (dry weight) in fish fillet and from 0.46 to 48 ng/g d.w. in fish liver. The method was applied for the analysis of fillets and livers of breams from the rivers Rhine and Saar, the Teltow Canal as well as carps kept in fish monitoring ponds fed by effluent from municipal wastewater treatment plants. This allowed for the first detection of 17 analytes including 10 metabolites/TPs such as gabapentin lactam and norlidocaine in fish tissues. These results highlight the importance of including metabolites and transformation products of pharmaceuticals in fish monitoring campaigns and further investigating their potential effects.

On-line sample preparation for multiclass vitamin, hormone, and mycotoxin determination in chicken egg yolk using LC-MS/MS

Hen egg yolk from chicken eggs were examined for their mycotoxin, hormone, and fat-soluble vitamin content. A method was developed for multi-class analysis of egg yolk using a dilute/precipitate, centrifuge, and shoot process coupled with on-line sample clean-up using restricted access media with LC-MS/MS. Matrix effects were evaluated and a standard addition protocol with internal standards was chosen for analyte quantitation. With some minor exceptions, the method displayed good linearity (R2 > 0.99), with appropriate limits of detection (0.05–10 ng/g) and limits of quantitation (0.15–30 ng/g) for the analytes tested. Overall, it was discovered there was some variation between the different types of eggs tested in these experiments, especially with regard to their fat-soluble vitamin contents. Low-level mycotoxins were detected in most of the eggs tested. The challenges associated with developing a multi-class compound determination from a single analytical run were elucidated.

Poly-ε-caprolactone Nanofibrous Polymers: A Simple Alternative to Restricted Access Media for Extraction of Small Molecules from Biological Matrixes.

Poly-ε-caprolactone nanofibrous polymer has been used as an alternative to restricted access media for extraction of protein-containing biological samples and direct transfer in the chromatographic system. Three commercial cartridges differing in length and internal diameter have been manually packed with the composite material prepared from poly-ε-caprolactone nanofibers coated on poly-ε-caprolactone microfibrous scaffold and connected to the column-switching chromatographic system. Bovine milk and human serum (25 μL) spiked with a mixture of methyl-, ethyl-, propyl-, and butylparaben in a concentration range of 1-100 μg mL-1 were online extracted using the cartridge-containing fibers. Then, 5 and 20% (v/v) aqueous methanol was applied as the washing mobile phase. While the ballast protein macromolecules were quantitatively eluted from the nano/microfibrous composite sorbent, the parabens were retained. After the mobile phase was switched to a stronger one, these compounds were then eluted from the extraction sorbent, directed in the analytical column, and finally separated. An extraction efficiency of 86-101% for all parabens achieved using the optimum-sized cartridge and a repeatability of the extraction procedure of 0.06-1.95% RSD were obtained.

BIOANALYTICAL METHOD BY COLUMN-SWITCHING WITH DIRECT INJECTION OF HUMAN PLASMA FOR DETERMINATION OF SULPHONYLUREAS

Sulphonylureas are widely used in the treatment of Diabetes mellitus, one of the main causes of death in human population. Their determination is essential in pharmacological research and in the development of new drugs. Generally, determination of sulphonylureas in biological matrices is performed using conventional sample preparation techniques, which frequently leads to an increase of analysis time and errors. In this context, a bioanalytical method for the simultaneous determination of sulphonylureas by direct injection of human plasma was developed and optimized. An automated column-switching high performance liquid chromatographic system with a restricted access media (RAM) column coupled to a fused-core column was employed. At the first dimension, a RAM column with mobile phase of ultrapure water pH 6.0 at a flow-rate of 1.0 mL min-1 was used. The valve switching time was 3 minutes. At the second dimension, a C18 guard-column coupled to a C18 fused core column with mobile phase of acetonitrile and 10 mM phosphate buffer pH 3.0 (54:46 v/v) at a flow-rate of 0.8 mL min-1 were employed. The column switching system was performed in backflush configuration with an analyte elution time of 1 minute. Flufenamic acid was used as the internal standard. The mean plasma protein exclusion percentage by the RAM-column was 104.5%. The developed and optimized method showed to be fast and simple, allowing the direct injection of biological sample into the chromatographic system and the simultaneous determination of three sulphonylureas in only 12 minutes, including the sample treatment, separation and detection.

Preparation of restricted access media molecularly imprinted polymers for efficient separation and enrichment ofloxacin in bovine serum samples.

We prepared ofloxacin restricted access media molecularly imprinted polymers using surface-initiated atom transfer radical polymerization on the surface of brominated silica gel using ofloxacin as a template molecule, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a crosslinking agent. We then characterized and studied the surface morphology and adsorption properties of the polymer. Experimental results show that saturation is reached within 25min, and that the saturated adsorption capacity was 80.67mg/g and the imprinting factor was 1.94. Our findings also showed that the polymer surface had good hydrophilicity and an excellent protein exclusion rate, which was 98.49%. The restricted access media molecularly imprinted polymers were then successfully applied to the enrichment and separation of ofloxacin in bovine serum. When combined with high-performance liquid chromatography, and the average recovery of ofloxacin was 95.6%, and the relative standard deviation was in the range of 2.47-3.38%. In a word, the restricted access media molecularly imprinted polymers is a method that involves a simple preparation procedure that results in excellent performance, which is a great improvement in the speed of detection of antibiotics. These qualities are what bestow upon this method its great potential for broad application.