Retracted: Rapid and effective sample cleanup based on graphene oxide-encapsulated core-shell magnetic microspheres for determination of fifteen trace environmental phenols in seafood by liquid chromatography-tandem mass spectrometry.

This article has been retracted at the request of the Editor after the corresponding author pointed the Editor to comments from an anonymous reader. The article reports electron micrographs of different preparations while showing identical images as used in previous publications by the same authors. The particles in Fig. 4C (SEM image of Fe3O4@SiO2) are identical to each other and the corresponding author confirmed that these have been copy-pasted. In addition, these particles have previously been communicated as different substances in Fig. 1B from Pan et al., J. Mater. Chem. A, 2015,3, 23042-23052 (DOI: 10.1039/C5TA05840F) and Fig. 3F from Pan et al., Anal. Methods, 2017,9, 5281-5292 (DOI: 10.1039/C7AY01444A). Furthermore, the curves in Fig. 7, especially the baseline, shows a remarkable similarity to Fig. 8 from Pan et al., J. Mater. Chem. A, 2015,3, 23042-23052 (DOI: 10.1039/C5TA05840F) and Fig. 5F from Pan et al., J. Mater. Chem. A, 2014,2, 15345-15356 (DOI: 10.1039/c4ta02600d). The manipulation of images and data in this way is a serious offense to the integrity of the scientific community and casts doubts on all the data, and accordingly also the conclusions based on that data, in this publication. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).

Understanding Mechanisms of Synergy between Acidification and Ultrasound Treatments for Activated Sludge Dewatering: From Bench to Pilot-Scale Investigation.

Enhancing activated sludge dewaterability is of scientific and engineering importance in the face of accelerated urbanization and stringent environmental regulations. In this study, we investigated the integration of acidification and ultrasound (A/US) treatment for improving sludge dewaterability at both bench- and pilot-scales. Our results showed that the A/US process exhibited significantly improved sludge dewatering performance, characterized by capillary suction time, cake moisture, and water/solid content of sludge cake. Synergistic dewatering mechanisms were elucidated with a suite of macro and spectroscopic evidence. Characterization of treated sludge revealed that US-induced thermal, mechanical shearing force, and radical oxidation effects disrupts floc cells and accelerates the decomposition of extracellular polymeric substances (EPS), releasing bound water into the bulk phase. In addition to enhancing hydrolysis of EPS, the acidic pH environment caused the protonation of functional groups on EPS, facilitating the reflocculation of US decomposed sludge for improved filterability. Our bench-scale and pilot-scale investigations provide a mechanistic basis for better understanding of the A/US process, and enable development of a viable and economical dewatering technology.

Rapid decolorization of dye Orange G by microwave enhanced Fenton-like reaction with delafossite-type CuFeO2.

Bimetallic oxide CuFeO2 as a new heterogeneous catalyst has shown much higher catalytic ability for activating peroxide than single-metal oxides. The present work demonstrated a synergistic microwave (MW) enhanced Fenton-like process with CuFeO2 for rapid decolorization of azo dye Orange G (OG). The MW irradiation dramatically enhanced the OG degradation efficiency, achieving 99.9% decolorization within 15min at pH5. The XRD analysis of reused CuFeO2, together with metal leaching tests, indicated merits of recycling for CuFeO2. The subsequent surface element analysis by XPS for fresh and used CuFeO2 showed a complex network for reactions between copper-iron redox pairs and surface hydroxyl groups, leading to a synergistic Fenton-like system accelerated by MW irradiation. In the CuFeO2 initiated Fenton-like reactions, several oxidant species (i.e., OH, O2-, electron hole, and FeIVO) responsible to the OG oxidation were identified by quenching experiments, showing the MW generated high temperature and "hot spots" enhanced the yield of OH by generation of electron-hole pairs. Further, the 26 detected degradation products confirmed the OH dominant oxidation of OG. This study shows that the MW-enhanced Fenton-like reaction using CuFeO2 has potential applications for rapid decolorization of dye effluent.

Planar graphene oxide-based magnetic ionic liquid nanomaterial for extraction of chlorophenols from environmental water samples coupled with liquid chromatography-tandem mass spectrometry.

A planar graphene oxide-based magnetic ionic liquid nanomaterial (PGO-MILN) was synthesized. The prepared PGO-MILN was characterized by transmission electronmicroscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The results of adsorption experiments showed that the PGO-MILN had great adsorption capacity for 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on the adsorption experimental data, a sensitive magnetic method for determination of the five CPs in environmental water samples was developed by an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of main MSPE parameters including the solution pH, extraction time, desorption time, and volume of desorption solution on the extraction efficiencies had been investigated in detail. The recoveries ranged from 85.3 to 99.3% with correlation coefficients (r) higher than 0.9994 and the linear ranges were between 10 and 500ngL(-1). The limits of detection (LODs) and limits of quantification (LOQs) of the five CPs ranged from 0.2 to 2.6ngL(-1) and 0.6 to 8.7ngL(-1), respectively. The intra- and inter- day relative standard deviations (RSDs) were in the range from 0.6% to 7.4% and from 0.7% to 8.4%, respectively. It was confirmed that the PGO-MILN was a kind of highly effective MSPE materials used for enrichment of trace CPs in the environmental water.

Rapid and effective sample cleanup based on graphene oxide-encapsulated core-shell magnetic microspheres for determination of fifteen trace environmental phenols in seafood by liquid chromatography-tandem mass spectrometry.

In this study, graphene oxide-encapsulated core-shell magnetic microspheres (GOE-CS-MM) were fabricated by a self-assemble approach between positive charged poly(diallyldimethylammonium) chloride (PDDA)-modified Fe3O4@SiO2 and negative charged GO sheets via electrostatic interaction. The as-prepared GOE-CS-MM was carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer analysis (VSM), and X-ray photoelectron spectroscopy (XPS), and was used as a cleanup adsorbent in magnetic solid-phase extraction (MSPE) for determination of 15 trace-level environmental phenols in seafood coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS). The obtained results showed that the GOE-CS-MM exhibited excellent cleanup efficiency and could availably reduce the matrix effect. The cleanup mechanisms were investigated and referred to π-π stacking interaction and hydrogen bond between GOE-CS-MM and impurities in the extracts. Moreover, the extraction and cleanup conditions of GOE-CS-MM toward phenols were optimized in detail. Under the optimized conditions, the limits of detection (LODs) were found to be 0.003-0.06 µg kg(-1), and satisfactory recovery values of 84.8-103.1% were obtained for the tested seafood samples. It was confirmed that the developed method is simple, fast, sensitive, and accurate for the determination of 15 trace environmental phenols in seafood samples.

Rapid analysis of six trace trichlorophenols in seawater by magnetic micro-solid-phase extraction and liquid chromatography with tandem mass spectrometry.

A new facile, rapid, inexpensive, and sensitive method for the analysis of six trace trichlorophenols in seawater samples was developed by magnetic micro-solid-phase extraction coupled to liquid chromatography with tandem mass spectrometry. Core-shell covalently functionalized ferroferric oxide coated with aminated silicon dioxide and decorated with multiwalled carbon nanotubes was applied as an adsorbent to perform the extraction process. The effect of factors including solution pH, contact time, adsorbent amount, and ionic strength were investigated in detail. The obtained results revealed that the proposed adsorbent was a highly effective and low-cost magnetic micro-solid-phase extraction material for the enrichment of 2,3,4-trichlorophenol, 2,3,5-trichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, and 3,4,5-trichlorophenol from seawater. Under the optimized conditions, the recoveries ranged from 88.0 to 99.5% at the three spiking levels, the limits of detection and the limits of quantification were 0.002 and 0.007 µg/L for the six trichlorophenols, respectively. The intra- and interday relative standard deviations were 2.0-6.7 and 4.5-8.9%, respectively. The calibration curves showed a good linearity in the range of 0.02-5.0 µg/L. The routine run analyses showed that the developed method was fast, simple, accurate, solvent-saving and high resolution, and it was suitable for the determination of trace trichlorophenols in seawater.

Double-sided magnetic molecularly imprinted polymer modified graphene oxide for highly efficient enrichment and fast detection of trace-level microcystins from large-volume water samples combined with liquid chromatography-tandem mass spectrometry.

Microcystins (MCs), a group of cyclic heptapeptide heaptoxins and tumor promoters, are generated by cyanobacteria occurring in surface waters, such as eutrophic lakes, rivers, and reservoirs. In this present study, a novel double-sided magnetic molecularly imprinted polymer modified graphene oxide (DS-MMIP@GO) based magnetic solid-phase extraction (MSPE) method was developed for fast, effective and selective enrichment, and recognition of trace MCs in environmental water samples combined with high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The synthesized novel DS-MMIP@GO was used as the adsorbents in this work and was carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectra. The adsorption and desorption conditions of DS-MMIP@GO toward MCs were optimized in detail to obtain the highest binding capacity, selectivity, and release efficiency. Under the optimum conditions, the enrichment factors of the method for eight target MCs were found to be 2000. The limits of quantitation (LOQs) of the method for eight MCs were in range of 0.1-2.0ngL(-1). The double-sided MMIP modified structure provided DS-MMIP@GO with abundant adsorption sites and permitted it to exhibit excellent enrichment and selectivity toward trace-level MCs. The proposed method was successfully applied for the analysis of environmental water samples with recoveries ranging from 84.1 to 98.2%. Compared to conventional methods for MCs detection reported in literatures, the one developed in this work based on DS-MMIP@GO and LC-MS/MS showed much faster, more sensitive, and more convenient.

Decolorization of azo dye Orange G by aluminum powder enhanced by ultrasonic irradiation.

In this work, the decolorization of azo dye Orange G (OG) in aqueous solution by aluminum powder enhanced by ultrasonic irradiation (AlP-UI) was investigated. The effects of various operating operational parameters such as the initial pH, initial OG concentration, AlP dosage, ultrasound power and added hydrogen peroxide (H2O2) concentration were studied. The results showed that the decolorization rate was enhanced when the aqueous OG was irradiated simultaneously by ultrasound in the AlP-acid systems. The decolorization rate decreased with the increase of both initial pH values of 2.0-4.0 and OG initial concentrations of 10-80mg/L, increased with the ultrasound power enhancing from 500 to 900W. An optimum value was reached at 2.0g/L of the AlP dosage in the range of 0.5-2.5g/L. The decolorization rate enhanced significantly by the addition of hydrogen peroxide in the range of 10-100mM to AlP-UI system reached an optimum value of 0.1491min(-1). The decolorization of OG appears to involve primarily oxidative steps, the cleavage of NN bond, which were verificated by the intermediate products of OG under the optimal tested degradation system, aniline and 1-amino-2-naphthol-6,8-disulfonate detected by the LC-MS.

Amine-functional magnetic polymer modified graphene oxide as magnetic solid-phase extraction materials combined with liquid chromatography-tandem mass spectrometry for chlorophenols analysis in environmental water.

A novel planar-structure amine-functional magnetic polymer modified graphene oxide nanocomposite (NH2-MP@GO) was synthesized. The properties were characterized by transmission electron microscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The obtained adsorption results showed that the NH2-MP@GO had great adsorptive ability toward five chlorophenols (CPs), including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on these, an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the preconcentration and determination of the five CPs in environmental water samples was developed. Various experimental parameters that could affect the extraction efficiencies had been investigated in detail. Under the optimum conditions, the enrichment factors of the method for the target CPs were found to be 1000. The proposed method was successfully applied for the analysis of environmental water samples with recoveries ranging from 86.4 to 99.8% with correlation coefficients (R) higher than 0.9994. Good linearities were obtained ranging from 10 to 500ng/L for 2-CP, 5 to 500ng/L for 2,4-DCP, 2 to 500ng/L for 2,4,6-TeCP and 2,3,4,6-TeCP, and 1 to 500ng/L for PCP, respectively. The limits of quantitation for the five CPs were 0.6-9.2ng/L. It was confirmed that the planar-structure NH2-MP@GO was a kind of highly effective MSPE materials used for the trace CPs analyses.

Novel amphiphilic polymeric ionic liquid-solid phase micro-extraction membrane for the preconcentration of aniline as degradation product of azo dye Orange G under sonication by liquid chromatography-tandem mass spectrometry.

A novel amphiphilic polymeric ionic liquid membrane containing a hydrophilic bromide anion and a hydrophobic carbonyl group was synthesized in dimethylformamide (DMF) systems using the ionic liquid 1-butyl-3-vinylimidazolium bromide (BVImBr) and the methylmethacrylate (MMA) as monomers. The prepared amphiphilic ploy-methylmethacrylate-1-butyl-3-vinylimidazolium bromide (MMA-BVImBr) was characterized by a scanning electron microscope and an infrared spectrum instrument. The results of solid-phase micro-extraction membrane (SPMM) experiments showed that the adsorption capacity of membrane was about 0.76µgµg(-1) for aniline. Based on this, a sensitive method for the determination of trace aniline, as a degradation product of azo dye Orange G under sonication, was developed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The calibration curve showed a good linearity ranging from 0.5 to 10.0µgL(-1) with a correlation coefficient value of 0.9998. The limit of quantification was 0.5µgL(-1). The recoveries ranged from 90.6% to 96.1%. The intra- and inter-day relative standard deviations were less than 8.3% and 10.9%. The developed SPMM-LC-MS/MS method was used successfully for preconcentration of trace aniline produced during the sonication of Orange G solution.

Determination of four pyridine alkaloids from Tripterygium wilfordii Hook. f. in human plasma by high-performance liquid chromatography coupled with mass spectrometry.

A novel liquid chromatography-atmospheric-pressure chemical ionization-mass spectrometry (LC-APCI/MS) method was developed and validated for the simultaneous determination of four sesquiterpene pyridine alkaloids (wilfortrine, wilfordine, wilforgine and wilforine) in human plasma. The chromatographic separation was performed on a Shim-pack XR-ODS column using an ammonium acetate buffer solution-acetonitrile in a gradient program. The detection was achieved by an ion trap mass spectrometry in the positive selected ion monitoring (SIM) mode. The method utilized acetonitrile as protein precipitation solvent and followed by solid-phase extraction (SPE). Calibration curves were linear for the four alkaloids over the range of 0.5-100.0 µg/L with the limits of quantification of 0.5 µg/L, while the method exhibited the recovery of 86.5-98.6%, intra- and inter-day RSDs of less than 8.2% and 12.8%, respectively. Methodology was validated in line with the EU requirements (Commission Decision 2002/657/EC). Results of incurred samples demonstrated excellent reproducibility. To our knowledge, this is the first analytical method for simultaneous determination of the four sesquiterpene pyridine alkaloids in plasma. The method was applicable to clinical pharmaceutical research of alkaloids in rheumatoid arthritis volunteer patients after oral administrations.

Simultaneous measurement of indandione-type rodenticides in human serum by liquid chromatography-electrospray ionization- tandem mass spectrometry.

Measurement of indandione rodenticides is important in the diagnosis and treatment of accidental rodenticide ingestion. Current assays lack effective measurements for simultaneous analysis of the indandiones, especially the isomers. The intent of this study was to establish a novel and selective method for the simultaneous determination of indandione-type rodenticides (diphacinone, chlorophacinone, valone, and pindone) in human serum by liquid chromatography-electrospray ionization-tandem mass spectrometry. After addition of internal standard, the sample was extracted with 10% methanol in acetonitrile and cleaned by solid-phase extraction (SPE). The analytes were separated on a C(18) rapid column and infused into an ion trap mass spectrometer in the negative electrospray ionization mode. The multiple-reaction monitoring ion pairs were m/z 339 --> 167, m/z 373 --> 201, m/z 229 --> 145, m/z 229 --> 172, and m/z 307 --> 161 for diphacinone, chlorophacinone, valone, pindone, and IS, respectively. Recoveries were between 81.5 and 94.6%, and the limits of quantification were 0.2 to 0.5 ng/mL. Intra- and interday RSDs were less than 7.9 and 11.5%, respectively. The assay was linear in the range of 0.5-100.0 ng/mL with coefficients of determination (r(2) > 0.99) for all analytes. The proposed method enables the unambiguous confirmation and quantification of the indandiones in both clinical and forensic specimens.

Ion chromatography tandem mass spectrometry for simultaneous confirmation and determination of indandione rodenticides in serum.

This paper describes a simple method for the simultaneous determination and confirmation of the indandione rodenticides in serum. After samples were extracted with 10% (v/v) methanol in acetonitrile and cleaned by solid-phase extraction, chromatographic separation was performed on an IonPac AS11 analytical column (250 x 4.0 mm) using gradient KOH eluent with 10% (v/v) methanol as organic modifier. Confirmation was depended on the extensive fragmentation of the indandione molecule under MS/MS conditions which provides sufficient structural information. Quantification was performed by negative electrospray ionization in multiple reaction monitoring mode. All the method parameters were validated. It was confirmed that this method could be used in clinical diagnosis and forensic toxicology.

Rapid identification and determination of the rodenticide valone in serum by high-performance liquid chromatography-tandem mass spectrometry.

Valone is a chronic anticoagulant rodenticide that has come into wide use in China. Current literature lacks analytical methods for the determination of valone. In this paper, a sensitive and selective assay was established for the identification and quantification of valone in serum by liquid chromatography-tandem mass spectrometry. After addition of the internal standard, warfarin, serum samples were extracted with 10% methanol in acetonitrile and cleaned using Oasis HLB solid-phase extraction (SPE) cartridges. The compounds were separated on an Agilent SB C18 column with a mobile phase of methanol/acetic acid-ammonium acetate (5 mmol/L, pH 6.3) (75:25, v/v). Detection was performed by electrospray ionization ion trap mass spectrometry in the negative multiple reaction monitoring mode. The transition ions of m/z 229 --> 145 and m/z 307 --> 161 were selected for quantification of valone and the internal standard, respectively. The overall extraction efficiency was between 81.1% and 91.1%. The limit of quantification was 0.5 ng/mL. Regression analysis of the calibration data revealed good correlation (r(2) > 0.99) for valone. Intra- and interday precisions for quality-control samples were less than 7.8% and 12.8%, respectively. This method combines a rapid SPE procedure with an extremely fast chromatographic analysis, which is especially advantageous or clinical laboratories.

An assay for identification and determination of toxic rodenticide valone in serum by ion chromatography-electrospray ionization tandem mass spectrometry with ion trap detector.

Valone has a chronic and toxic anticoagulant rodenticide that has widely used in China and has resulted in some accidental and intentional intoxication in recent years. The literature reported so far lacks sensitive and selective method for the confirmation of valone. The purpose of this study was to establish a novel assay for the identification and quantification of valone in serum by ion chromatography-electrospray ionization tandem mass spectrometry (IC-MS/MS). After serum sample was extracted with methanol/acetonitrile (10:90, v/v) and cleaned by Oasis HLB solid-phase extraction cartridge, chromatographic separation was performed on an Ionpac AS11 column with an eluent of methanol/30 mmol/L KOH (10:90, v/v). The overall extraction efficiency was >81.0%, and the limit of quantification was 0.5 ng/mL for valone. Regression analysis of the calibration data revealed good correlation (r(2)>0.99) for valone. Intra- and inter-day precisions for quality-control samples were less than 8.0 and 13.7%, respectively. The proposed method enables the identification and quantification of valone in both clinical and forensic specimens.

Development and validation of a liquid chromatography coupled with atmospheric-pressure chemical ionization ion trap mass spectrometric method for the simultaneous determination of triptolide, tripdiolide, and tripterine in human serum.

A sensitive method has been developed and validated for the simultaneous determination of triptolide, tripdiolide, and tripterine in human serum using hydrocortisone as an internal standard (IS). After triptolide, tripdiolide, and tripterine in human serum were extracted with ethyl acetate, the extracts were separated on an XDB C(18) column (30 mm x 2.1-mm i.d., 3 microm) using a mobile phase of acetic acid/ammonium acetate (5 mmol/L, pH 4.5)/acetonitrile/methanol in gradient elution. Detection was performed by high-performance liquid chromatography coupled with atmospheric-pressure chemical ionization ion trap mass spectrometry in negative multiple reaction monitoring mode. The transition ions m/z 359 --> 340, m/z 375 --> 357, m/z 449 --> 405, and m/z 419 --> 329 were selected for the quantification of triptolide, tripdiolide, tripterine, and IS, respectively. The linear range was 1.0-100.0 ng/mL, the absolute recoveries were between 78.3 and 89.2%, the relative recoveries were between 88.1 and 94.6%, and the limits of quantification in human serum were 0.5-1.0 ng/mL for the three target compounds. The intra- and interday relative standard deviations were less than 11.9% and 13.0%, respectively. This method was found to effectively and simultaneously determine trace triptolide, tripdiolide, and tripterine in human serum and can be suitable for clinical and toxicological studies.

Improvement of leaching process of Geniposide with ultrasound.

The effect of ultrasound on the leaching process, in which Geniposide is leached from the Gardenia fruit by deionized water at 20 degrees C, was investigated. The phase equilibrium and the dynamics were measured at static, stirring, and ultrasonically assisted conditions, respectively. The experimental results show that the extraction yield of Geniposide with ultrasound at 0.1533 W cm(-2), is increased by 16.5%, in comparison with that without ultrasound when the ratio of the solvent volume to the fruit weight is 40 ml/g. A model for mass transfer, based on the intraparticle diffusion and the external mass transfer, was developed. And the dynamic curves calculated by the model are in a good agreement with the experimental data. The external mass transfer coefficient k(f)/R and intraparticle diffusion coefficient D(e)/R2 were obtained by fitting of the experiment data. The external mass transfer coefficient with ultrasound at 0.1533 W cm(-2) is 1.63 times higher than that in static process, and the intraparticle diffusion coefficient with ultrasound at 0.1533 W cm(-2) is 3.25 times higher than that in static process.