Chemical Two-Photon Fluorescence

Analytical ChemistryDOI: 10.1021/acs.analchem.5b00131



Editorial Board

Publication date: 1 May 2015 Source:Journal of Chromatography B, Volume 989



Long-term analyses in automated electrophoretic analyzer in hydrodynamically closed separation system

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Andrea Vojs Staňová , Martina Hrenáková , Jozef Marák
Some potential problems that can occur during the analyses of complex samples by on-line combination of capillary isotachophoresis–capillary zone electrophoresis (cITP–CZE) in automated electrophoretic analyzer with the column-coupling configuration of the separation unit were studied in this work. The main focus was devoted on the reproducibility of important analytes’ parameters (migration time, peak height and peak area) and also on the stability studies of selected low and high molecular mass analytes of inorganic/organic origins (bromate, vitamins, proteins) present at low concentration levels in different kinds of matrices (mineral water, human urine).Such study was carried out for the first time for the electrophoretic analyzer operating in the hydrodynamically closed separation system provided with contact-less conductivity detectors and UV detector in CZE step. Hydrodynamic and electroosmotic flows of the buffer solutions were suppressed and therefore, only the electrophoretic transport of ions was significant. Obtained results showed the different stabilities of the analytes and samples depending on their origin. The focus in the long-term analyses should be paid on the storage of the samples and on the regular changing the contents of electrolyte vessels to keep the electrolyte composition and separation conditions as constant as possible.



Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): G.F. Koopmans , T. Hiemstra , I.C. Regelink , B. Molleman , R.N.J. Comans
Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV–vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10–90nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV–vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used.



Peak distortions arising from large-volume injections in supercritical fluid chromatography

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Yun Dai , Geng Li , Arvind Rajendran
Preparative separations in supercritical fluid chromatography (SFC) involve the injection of large volumes of the solute. In SFC, the mobile phase is typically high pressure CO2+modifier and the solute to be injected is usually dissolved in the modifier. Two-types of injection methods, modifier-stream and mixed-stream, are common in commercial preparative SFC systems. In modifier-stream injection, the injection is made in the modifier stream which is later mixed with the CO2 stream, while in the mixed-stream injection, the injection is made in a mixed CO2+modifier stream. In this work a systematic experimental and modelling study of the two techniques is reported using single-enantiomers of flurbiprofen on Chiralpak AD-H with CO2+methanol as the mobile phase. While modifier-stream injection shows non-distorted peaks, mixed-stream injection results in severe peak-distortion. By comparing the modelling and experimental results, it is shown that the modifier “plug” introduced in the mixed-stream injection is the primary cause of the peak distortions. The experimental results also point to the possible existence of viscous fingering which contributes to further peak distortion.



Evaluation of injection methods for fast, high peak capacity separations with low thermal mass gas chromatography

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Brian D. Fitz , Brandyn C. Mannion , Khang To , Trinh Hoac , Robert E. Synovec
Low thermal mass gas chromatography (LTM-GC) was evaluated for rapid, high peak capacity separations with three injection methods: liquid, headspace solid phase micro-extraction (HS-SPME), and direct vapor. An Agilent LTM equipped with a short microbore capillary column was operated at a column heating rate of 250°C/min to produce a 60s separation. Two sets of experiments were conducted in parallel to characterize the instrumental platform. First, the three injection methods were performed in conjunction with in-house built high-speed cryo-focusing injection (HSCFI) to cryogenically trap and re-inject the analytes onto the LTM-GC column in a narrower band. Next, the three injection methods were performed natively with LTM-GC. Using HSCFI, the peak capacity of a separation of 50nl of a 73 component liquid test mixture was 270, which was 23% higher than without HSCFI. Similar peak capacity gains were obtained when using the HSCFI with HS-SPME (25%), and even greater with vapor injection (56%). For the 100μl vapor sample injected without HSCFI, the preconcentration factor, defined as the ratio of the maximum concentration of the detected analyte peak relative to the analyte concentration injected with the syringe, was determined to be 11 for the earliest eluting peak (most volatile analyte). In contrast, the preconcentration factor for the earliest eluting peak using HSCFI was 103. Therefore, LTM-GC is demonstrated to natively provide in situ analyte trapping, although not to as great an extent as with HSCFI. We also report the use of LTM-GC applied with time-of-flight mass spectrometry (TOFMS) detection for rapid, high peak capacity separations from SPME sampled banana peel headspace.



Assessment of comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry based methods for investigating 206 dioxin-like micropollutants in animal-derived food matrices

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Christelle Planche , Jérémy Ratel , Frédéric Mercier , Patrick Blinet , Laurent Debrauwer , Erwan Engel
This paper evaluates different multiresidue methods based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF/MS) to analyze dioxin-related micropollutants in complex food matrices. In a first step, the column sets Rtx-PCB/BPX-50 and Rtx-Dioxin2/BPX-50 were compared in terms of peak shape (width and symmetry) and resolution for the separation of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in solvent. A satisfactory separation of 206 dioxin-related micropollutants including the 17 toxic PCDD/Fs was achieved in 75min with the column set Rtx-Dioxin2/BPX-50. In a second time, the GC×GC-TOF/MS method was spread to the analysis of dioxin-related micropollutants in complex food matrices. An extraction procedure including accelerated solvent extraction (ASE), centrifugal evaporation and gel permeation chromatography (GPC) was optimized. Starting with meat as a model matrix, a micropollutant spiking method was then set up by comparing seven methods in terms of recoveries and reproducibility. The method combining immersion of the meat in a large volume of solvent containing micropollutants followed by homogenization by blender induced recoveries in the acceptable range of 70–130% and satisfactory standard deviations (≤10%) for most of the compounds studied. Limits of detection of the GC×GC-TOF/MS method ranged between 50 and 100pg/g of spiked fresh meat for PCBs and between 65 and 227pg/g for PCDD/Fs. Potential applications of this method are discussed.



Selective removal of carbon dioxide contained in the effluent from ion chromatography suppressors using a new non-vacuum device

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Hiroto Masunaga , Yuji Higo , Mizuo Ishii , Noboru Maruyama , Shigeo Yamazaki
In this paper, a new CO2 gas removal device optimized to selectively remove CO2 gas contained in the effluent from suppressors used in ion chromatography (IC) under non-vacuum conditions is described. This device consists of a closed vessel equipped with gas permeable tubing (GPT) and a CO2 adsorbent. During operation, the CO2 adsorbent adsorbs CO2 gas in the vessel, creating CO2 partial pressure difference between the inside of the GPT and the vessel. The CO2 gas contained in the effluent being pumped into the GPT is selectively removed from the effluent based on the diffusion of the CO2 associated with the CO2 partial pressure difference. The purpose of this study is to optimize the IC operating conditions with the aim of selectively removing HCO3 (CO32−) contained in the effluent and reducing the electrical conductivity of the effluent under non-vacuum conditions. The electrical conductivity of the effluent and the signal intensity of the water dip is decreased by approximately 25μS/cm (from 30 to 5μS/cm) and by approximately twentieth, respectively, using the optimized CO2 remover. In addition, the anion detection limit achieved in IC instruments with a CO2 remover is on the order of a few ppb.



A new anion-exchange/hydrophobic monolith as stationary phase for nano liquid chromatography of small organic molecules and inorganic anions

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Cemil Aydoğan
In this study, an anion-exchange/hydrophobic polymethacrylate-based stationary phase was prepared for nano-liquid chromatography of small organic molecules and inorganic anions. The stationary phase was synthesized by in situ polymerization of 3-chloro-2-hydroxypropylmethacrylate and ethylene dimethacrylate inside silanized 100μm i.d. fused silica capillary. The porogen mixture consisted of toluene and dodecanol. The pore size distrubution profiles of the resulting monolith were determined by mercury intrusion porosimetry and the morphology of the prepared monolith was investigated by scanning electron microscope. Good permeability, stability and column efficiency were observed on the monolithic column with nano flow. The produced monolithic column, which contains reactive chloro groups, was then modified by reaction with N,N-dimethyl-N-dodecylamine to obtain an anion-exchange/hydrophobic monolithic stationary phase. The functionalized monolith contained ionizable amine groups and hydrophobic groups that are useful of anion-exchange/hydrophobic mixed-mode chromatography. The final monolithic column performance with respect to anion-exchange and hydrophobic interactions was assesed by the separation of alkylbenzene derivatives, phenolic compounds and inorganic anions, respectively. Theoretical plate numbers up to 23,000 plates/m were successfully achieved in the separation of inorganic anions.



Effects of substitution groups of glutamide-derived molecular gels on molecular shape recognition

Publication date: 1 May 2015 Source:Journal of Chromatography A, Volume 1392 Author(s): Hiroki Noguchi , Tiraporn Charoenraks , Makoto Takafuji , Hirotaka Ihara We have reported that self-assembling glutamide lipid-grafted porous s…



Design of a coil satellite centrifuge and its performance on counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives with polar organic–aqueous two-phase solvent systems

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Kazufusa Shinomiya , Koji Tokura , Emiru Kimura , Midori Takai , Naoki Harikai , Kazunori Yoshida , Kazuhiro Yanagidaira , Yoichiro Ito
A new high-speed counter-current chromatograph, named coil satellite centrifuge (CSC), was designed and fabricated in our laboratory. The CSC apparatus produces the satellite motion such that the coiled column simultaneously rotates around the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3). In order to achieve this triplicate rotary motion without twisting of the flow tube, the rotation of each axis was determined by the following formula: ω1=ω2+ω3. This relation enabled to lay out the flow tube without twisting by the simultaneous rotation of three axes. The flow tube was introduced from the bottom side of the apparatus into the sun axis of the first rotary frame reaching the upper side of the planet axis and connected to the column in the satellite axis. The performance of the apparatus was examined on separation of 4-methylumbelliferyl (MU) sugar derivatives as test samples with organic–aqueous two-phase solvent systems composed of ethyl acetate/1-butanol/water (3:2:5, v/v) for lower phase mobile and (1:4:5, v/v) for upper phase mobile. With lower phase mobile, five 4-MU sugar derivatives including β-d-cellobioside (Cel), β-d-glucopyranoside, α-d-mannopyranoside, β-d-fucopyranoside and α-l-fucopyranoside (α-l-Fuc) were separated with the combined rotation around each axis at counterclockwise (CCW) (ω1) – CCW (ω2) – CCW (ω3) by the flow tube distribution. With upper phase mobile, three 4-MU sugar derivatives including α-l-Fuc, β-d-galactopyranoside and Cel were separated with the combined rotation around each axis at clockwise (CW) (ω1) – CW (ω2) – CW (ω3) by the flow tube distribution. A series of experiments on peak resolution and stationary phase retention revealed that better partition efficiencies were obtained at the flow rate of 0.5mL/min (column 1) and 0.8mL/min (column 2) for lower phase mobile and 0.2mL/min (column 1) and 0.4mL/min (column 2) for upper phase mobile when using the left-handed multilayer coil (total capacity: 57.0mL for column 1 and 75.0mL for column 2) under the rotation speeds of approximately ω1=300rpm, ω2=150rpm and ω3=150rpm.



Editorial Board

Publication date: 1 May 2015 Source:Journal of Chromatography A, Volume 1392



Separation of parent homopolymers from poly(ethylene oxide) and polystyrene-based block copolymers by liquid chromatography under limiting conditions of desorption – 1. Determination of the suitable molar mass range and optimization of chromatographic conditions

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Marion Rollet , Bérengère Pelletier , Anaïs Altounian , Dusan Berek , Sébastien Maria , Trang N.T. Phan , Didier Gigmes
We studied molar mass limits for the LC LCD separation of parent polystyrene (PS) and poly(ethylene oxide) (PEO) homopolymers from PEO/PS based block copolymers and we identified optimized chromatographic conditions. Time delays between barriers and sample injections were 0–2–3′10. Eluent was composed of dimethylformamide (DMF) 40wt.% and 1-chlorobutane (CLB) 60wt.%; Barrier 1 (B1), which retained block copolymer, was composed of 100wt.% CLB and Barrier 2 (B2), which retained PEO, was a mixture of DMF and CLB, which proportions were adjusted to studied block copolymers. With B2 composed of DMF 23wt.% and CLB 77wt.%, we obtained successful separation of PS23K-b-PEO35K-b-PS23K (56.5wt.% of PS, the subscripts indicate the molar mass in kgmol−1 of each polymer part in the block copolymer) from its parent homopolymers. With B2 adjusted to DMF 30wt.% and CLB 70wt.%, PS2.3K-b-PEO3.1K (42.6wt.% of PS) was also efficiently separated from its parent homopolymers.



Fabrication of enzyme-immobilized halloysite nanotubes for affinity enrichment of lipase inhibitors from complex mixtures

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Haibo Wang , Xiaoping Zhao , Shufang Wang , Shan Tao , Ni Ai , Yi Wang
Lipase is the key enzyme for catalyzing triglyceride hydrolysis in vivo, and lipase inhibitors have been used in the management of obesity. We present the first report on the use of lipase-adsorbed halloysite nanotubes as an efficient medium for the selective enrichment of lipase inhibitors from natural products. A simple and rapid approach was proposed to fabricate lipase-adsorbed nanotubes through electrostatic interaction. Results showed that more than 85% lipase was adsorbed into nanotubes in 90min, and approximately 80% of the catalytic activity was maintained compared with free lipase. The specificity and reproducibility of the proposed approach were validated by screening a known lipase inhibitor (i.e., orlistat) from a mixture that contains active and inactive compounds. Moreover, we applied this approach with high performance liquid chromatography–mass spectrometry technique to screen lipase inhibitors from the Magnoliae cortex extract, a medicinal plant used for treating obesity. Two novel biphenyl-type natural lipase inhibitors magnotriol A and magnaldehyde B were identified, and their IC50 values were determined as 213.03 and 96.96μM, respectively. The ligand–enzyme interactions of magnaldehyde B were further investigated by molecular docking. Our findings proved that enzyme-adsorbed nanotube could be used as a feasible and selective affinity medium for the rapid screening of enzyme inhibitors from complex mixtures.



Surface molecularly imprinted silica for selective solid-phase extraction of biochanin A, daidzein and genistein from urine samples

Publication date: 1 May 2015
Source:Journal of Chromatography A, Volume 1392
Author(s): Anna M. Chrzanowska , Anna Poliwoda , Piotr P. Wieczorek
Selective molecularly imprinted silica polymer (SiO2MIP) for extraction of biochanin A, daidzein and genistein was synthesized using the surface molecular imprinting technique with the silica gel as a support. Biochanin A (BCA) was used as a template, 3-aminopropyltriethoxysilane (APTES) as a functional monomer, and tetraethoxysilicane (TEOS) as a cross-linker. Non-imprinted polymer with the sol–gel process (SiO2NIP) was also prepared for comparison. The synthesized polymers were characterized by Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and a standard Brunauer-Emett-Teller (BET) and Barret–Joyner–Halenda (BJH) analysis. The obtained results indicated the structural differences between imprinted and non-imprinted polymers. Finally, the SiO2MIP and SiO2NIP were adopted as the adsorbents of solid phase extraction for isolation and preconcentration of biochanin A and its structural analogues–daidzein and genistein from aqueous and urine samples. The performance analysis revealed that SiO2MIP displayed better affinity to the three investigated isoflavones compared with SiO2NIP. The recoveries of spiked samples for studied analytes ranged from 65.7% to 102.6% for molecularly imprinted silica polymer and 8.9–16.0% for non-imprinted sorbents.



An LC-MS/MS method for determination of calceorioside B with cardiomyocyte protective activity in rat plasma and application to a pharmacokinetic study

A simple, sensitive and rapid liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of calceorioside B (CLB) in rat plasma. Detection was performed on a Thermo Scientific Hypersil Gold chromatography column using isocratic elution with a mobile phase of methanol–5 m m ammonium acetate–formic acid (70:30:0.1, v/v/v). Mass spectrometry was performed in selection reaction monitoring mode using a positive electrospray ionization interface. Good linearity was found for CLB in plasma in the linear range of 1.00–500 ng/mL (r > 0.9960). The validated method was successfully applied to the pharmacokinetic study of CLB in rats. Copyright © 2015 John Wiley & Sons, Ltd.



Affordable and rapid HPTLC method for the simultaneous analysis of artemisinin and its metabolite artemisinic acid in Artemisia annua L.

Artemisinin (AN) and artemisinic acid (AA), valuable phyto-pharmaceutical molecules, are well known anti-malarials, but their activities against diseases like cancer, schistosomiasis, HIV, hepatitis-B and leishmaniasis are also being reported. For the simultaneous estimation of AN and AA in the callus and leaf extracts of A. annua L. plants, we embarked upon a simple, rapid, selective, reliable and fairly economical high performance thin layer chromatography (HPTLC) method. Experimental conditions such as band size, chamber saturation time, migration of solvent front and slit width were critically studied and the optimum conditions were selected. The separations were achieved using toluene–ethyl acetate, 9:1 (v/v) as mobile phase on pre-coated silica gel plates, G 60F254. Good resolution was achieved with Rf values of 0.35 ± 0.02 and 0.26 ± 0.02 at 536 nm for AN and 626 nm for AA, respectively, in absorption–reflectance mode. The method displayed a linear relationship with r2 value 0.992 and 0.994 for AN and AA, respectively, in the concentration range of 300–1500 ng for AN and 200–1000 ng for AA. The method was validated for specificity by obtaining in-situ UV overlay spectra and sensitivity by estimating limit of detection (30 ng for AN and 15 ng for AA) and limit of quantitation (80 ng for AN and 45 ng for AA) values. The accuracy was checked by the recovery studies conducted at three different levels with the known concentrations and the average percentage recovery was 101.99% for AN and 103.84% for AA. The precision was analyzed by interday and intraday precision and was 1.09 and 1.00% RSD for AN and 1.22 and 6.05% RSD for AA. The analysis of statistical data substantiates that this HPTLC method can be used for the simultaneous estimation of AN and AA in biological samples. Copyright © 2015 John Wiley & Sons, Ltd.



UHPLC-MS method for determination of gambogic acid and application to bioavailability, pharmacokinetics, excretion and tissue distribution in rats

A sensitive ultrahigh performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method was developed for determination of gambogic acid (GA) in rat plasma, urine, bile and main tissues. GA was separated on an Agilent Zorbax XDB–C18 column (50 × 2.1 mm, 1.8 µm) with gradient mobile phase at the flow rate of 0.2 mL/min. The detection was performed by negative electrospray ionization with multiple reaction monitoring mode. The calibration curves of GA were linear between 1.0 and 1000 ng/mL in rat plasma and bile and between 1.0 and 500 ng/mL in urine and tissues. The lowest limit of quantification for all matrices was 1.0 ng/mL. Both accuracy and precision of the assay were satisfactory. This validated method was firstly applied to bioavailability (BA), pharmacokinetics, excretion and tissue distribution in rats. The BAs of GA (40 and 80 mg/kg) in rats were 0.25 and 0.32%, respectively. GA was distributed extensively in rats after oral administration and exhibited the highest level in liver. GA reached the cumulative excretion amount of 25.3 ± 1.7 µg in bile and 0.275 ± 0.08 µg in urine after i.g. 80 mg/kg to rats at 24 h. The present results would be helpful for further clinical use of GA as a potential anticancer drug. Copyright © 2015 John Wiley & Sons, Ltd.



HPLC with fluorescence detection assay of perampanel, a novel AMPA receptor antagonist, in human plasma for clinical pharmacokinetic studies

Perampanel (Fycompa®), a novel α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, is registered for the adjunctive treatment of patients (aged ≥12 years) with refractory partial-onset seizures. To support therapeutic drug monitoring, a simple high-performance liquid chromatography (HPLC) assay with fluorescence detection was developed to determine perampanel concentrations in human plasma and validated to support clinical trials. Human plasma samples (1.0 mL) were processed by liquid extraction using diethyl ether, followed by chromatographic separation on a YMC Pack Pro C18 column (150 × 4.6 mm i.d., 5 µm) with isocratic elution of acetonitrile–water–acetic acid–sodium acetate (840:560:3:1.8, v/v/v/w) at a flow rate of 1.0 mL/min. Column eluent was monitored at excitation and emission wavelengths of 290 and 430 nm, respectively. The assay was linear (range 1.0–500 ng/mL) and this could be extended to 25 µg/mL by 50-fold dilution integrity. No endogenous peaks were detected in the elution of analytes in drug-free blank human plasma from six individuals and no interference was observed with co-medications tested. Intra- and inter-batch reproducibility studies demonstrated accuracy and precision within the acceptance criteria of bioanalytical guidelines. Validation data demonstrated that our assay is simple, selective, reproducible and suitable for therapeutic drug monitoring of perampanel. Copyright © 2015 John Wiley & Sons, Ltd.



Magnetic graphene oxide modified with choline chloride-based deep eutectic solvent for the solid-phase extraction of protein

Publication date: Available online 31 March 2015
Source:Analytica Chimica Acta
Author(s): Yanhua Huang , Yuzhi Wang , Qi Pan , Ying Wang , Xueqin Ding , Kaijia Xu , Na Li , Qian Wen
Four kinds of green deep eutectic solvents (DESs) based on choline chloride (ChCl) have been synthesized and coated on the surface of magnetic graphene oxide (Fe3O4@GO) to form Fe3O4@GO-DES for the magnetic solid-phase extraction of protein. X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were employed to characterize Fe3O4@GO-DES, and the results indicated the successful preparation of Fe3O4@GO-DES. The UV–vis spectrophotometer was used to measure the concentration of protein after extraction. Single factor experiments proved that the extraction amount was influenced by the types of DESs, solution temperature, solution ionic strength, extraction time, protein concentration and the amount of Fe3O4@GO-DES. Comparison of Fe3O4@GO and Fe3O4@GO-DES were carried out by extracting bovine serum albumin, ovalbumin, bovine hemoglobin and lysozyme. The experimental results showed that the proposed Fe3O4@GO-DES performs better than Fe3O4@GO in the extraction of acidic protein. Desorption of protein was carried out by eluting the solid extractant with 0.005mol/LNa2HPO4 contained 1mol/LNaCl. The obtained elution efficiency was about 90.9%. Attributed to the convenient magnetic separation, the solid extractant could be easily recycled.

Graphical abstract

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