Magnetic solid-phase extraction based on a triethylenetetramine-functionalized magnetic graphene oxide composite for the detection of ten trace phenolic environmental estrogens in environmental water.

A novel triethylenetetramine-functionalized magnetic graphene oxide composite was prepared and used as a magnetic solid-phase extraction adsorbent for the fast detection of ten trace-level phenolic environmental estrogens in environmental water. The synthesized material was carefully characterized by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy to confirm the structure and components. The adsorption and desorption conditions of the adsorbent toward phenolic environmental estrogens were optimized in detailed to obtain the best extraction recovery and elution efficiency. Under the optimum conditions, the limits of detection of the method for ten phenolic environmental estrogens were in range of 0.15-1.5 ng/L, which was lower than the reported methods for phenolic environmental estrogens detection in literatures. This could be contributed to the unique structure and property of the as-prepared material. The developed method was successfully applied for the determination of environmental water samples with recoveries ranging from 88.5 to 105.6%.

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.

Multiple mycotoxins in commonly used edible oils: Occurrence and evaluation of potential health risks.

In this study, the contamination of 51 mycotoxins in 416 edible oils were determined by UPLC-MS/MS. Totally, twenty-four mycotoxins were detected and nearly half of the samples (46.9%, n = 195) were contaminated simultaneously with six to nine kinds of mycotoxins. The predominant mycotoxins and contamination characteristics varied depending on the type of oils. More specifically, four enniatins, alternariol monomethyl ether (AME) and zearalenone were the most frequent combination. Overall, peanut and sesame oils (10.7-11.7 mycotoxins on average) were found to be the most contaminated matrices whereas camellia and sunflower seed oils (1.8-2.7 species) were the opposite. Dietary exposure risks of mycotoxins were acceptable in most cases, however, the ingestion of aflatoxins (especially aflatoxin B1) through peanut and sesame oil (margin of exposure: 239.4-386.3 < 10000) exceeded the acceptable carcinogenic risk level. Meanwhile, the risks of cumulative ingestion through the food chain should be of great concern, especially sterigmatocystin, ochratoxin A, AME and zearalenone.

Determination of multiple bisphenol analogues and their metabolites in human serum by liquid chromatography tandem mass spectrometry.

To date, knowledge of internal human exposure to BPA and its analogues (particularly bisphenol S and bisphenol F, etc.) remains limited. In the present study, a method involving dispersive solid-phase extraction and LC/MS was proposed to investigate the contamination levels of 28 precursor bisphenols and 9 major metabolites in serum. The critical variables of preparation method were screened out by Plackett-Burman design and further optimized by central composite design. Left in optimal conditions, a total of 286 samples consisting of 153 males and 133 females were analyzed. The results showed that BPA dominated over all the cases with the highest positive rate (82.2% of all the surveyed people), and totally four metabolites (BPA ß-D-glucuronide, BPA monosulfate, BPA bis-(ß-D-glucuronide) and BPS monosulfate) were detectable. The occurrence of BPA bis-(ß-D-glucuronide) in serum is reported for the first time and its higher positive rate and contamination concentrations suggested that it may be a more important metabolite of BPA than others. Negligible potential risk of health effects to blood donors was observed, since the estimated exposure levels (mean 32.1 ng/kg bw/day, 95th 123.2 ng/kg bw/day) were well below far less than the temporary tolerable reference dose of BPA that recommended by the European Food Safety Authority (4 µg/kg bw/day by). The reference level of BPA for healthy population was determined to be 4.09 µg/L via the percentile method.

Investigation on the occurrence and contamination of multi-mycotoxin in chestnut and jujube (red date).

A rapid and efficient QuEChERS-based preparation method was established for the simultaneous determination of 43 mycotoxins in chestnut and jujube (Chinese date). The contaminants were extracted using acetonitrile and subjected to dispersive solid-phase extraction for further clean-up. Central composite design was conducted to overcome the limitations of conventional optimization methods, and assess the interaction effects between variables and reach the true optimal conditions. Quantitative analysis was performed on UHPLC-MS/MS with the aid of stable isotope internal standards and matrix-matched curves, whereas qualitative identification was carried out by using high-resolution MS based on exact masses and fragmentation patterns. In addition to the mycotoxins that are routinely monitored (like aflatoxins, ochratoxin A, etc.), this study also revealed a non-negligible contamination of zearalenone (56/170), beauvericin (52/170), enniatin B (43/170), and alternariol monomethyl ether (42/170) in chestnut and jujube, especially the chestnut flour.

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.

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.

Simultaneous determination of triptolide, tripdiolide and tripterine in human urine by high-performance liquid chromatography coupled with ion trap atmospheric-pressure chemical ionization mass spectrometry.

An accurate and selective method for the simultaneous determination of triptolide, tripdiolide and tripterine in human urine using hydrocortisone as an internal standard (IS) by high-performance liquid chromatography coupled with atmospheric-pressure chemical ionization mass spectrometry in negative ion mode has been developed. After triptolide, tripdiolide and tripterine in human urine were extracted with ethyl acetate and cleaned by solid-phase extraction with C(18) cartridges, a satisfactory separation was achieved on an XDB C(18) short column (30 x 2.1 mm i.d., 3 microm) using the mobile phase of acetic acid-ammonium acetate (5 mmol/L, pH = 4.5)-acetonitrile-methanol in gradient elution. Detection was operated by APCI in selected ion monitoring mode. The target ions m/z 359, m/z 375, m/z 449 and m/z 419 were selected for the quantification of triptolide, tripdiolide, tripterine and IS, respectively. The linear range was 1.0-100.0 ng mL(-1), and the limits of quantification in human urine were found to be 0.1-0.5 ng mL(-1) for the three compounds. The precisions (CV%) and accuracies were 6.6-12.9 and 85.1-97.0%, respectively. The developed method could be applied to the determination of triptolide, tripdiolide and tripterine in human urine for diagnosis of the intoxication and for forensic purposes.

Characterization and determination of chlorophacinone in plasma by ion chromatography coupled with ion trap electrospray ionization mass spectrometry.

Plasmatic chlorophacinone is commonly measured with liquid chromatographic assay, which convenient but lacks sensitivity and selectivity and usually requires ion pair reagents to reduce the chromatographic tailed peak. In this paper, a novel method using eluent generator reagent-free ion chromatography coupled with electrospray ionization ion trap mass spectrometric detection for the determination of chlorophacinone in plasma has been developed. 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 40.0 mmol/L KOH containing 10% (v/v) methanol as organic modifier. Quantification was performed by negative electrospray ionization in multiple reaction monitoring mode. The transition m/z 373 --> 201 was for the quantification ion; the transitions m/z 373 --> 172 and m/z 373 --> 145, as well as the isotope ions m/z 375 and m/z 203, were for the qualitative ions. All the method parameters were validated. It was confirmed that this method can be used in clinical diagnosis and forensic toxicology.

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.

Correction: Surface core-shell magnetic polymer modified graphene oxide-based material for 2,4,6-trichlorophenol removal.

[This corrects the article DOI: 10.1039/C4RA14150D.].

Contamination status of bisphenol A and its analogues (bisphenol S, F and B) in foodstuffs and the implications for dietary exposure on adult residents in Zhejiang Province.

An effective method has been developed for the simultaneous determination of four bisphenols (bisphenol A, S, F and B) in various foodstuffs. The contaminants were extracted by QuEChERS-based strategy and subjected to ion-exchange solid-phase extraction for further clean-up. The critical variables were screened by Plackett-Burman design and then optimized by central composite design. Under the optimized conditions, satisfactory accuracy (recoveries 76%-116%) and precision (RSDs < 12%) were achieved. The established method was then used to assess the contamination status of 379 real samples. Bisphenol A was demonstrated to be the predominant bisphenol with highest incidence (79.7%) and average concentration (14.3 µg/kg). The positive rates (mean concentration) of bisphenol S, F and B were 37.7% (1.6 µg/kg), 26.9% (1.4 µg/kg) and 0.0% (not detected), respectively. Finally, the daily dietary intakes of ∑4bisphenolsfor adult residents were estimated (55.9-76.1 ng/kg bw/day) according to the contamination concentrations and the daily recommended intakes.

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).

Analysis of indandione anticoagulant rodenticides in animal liver by eluent generator reagent free ion chromatography coupled with electrospray mass spectrometry.

A novel analytical method has been developed for simultaneous determination of four indandione anticoagulant rodenticides (diphacinone, chlorophacinone, pindone and valone) in animal liver tissues by eluent generator reagent free ion chromatography coupled with electrospray ionization mass spectrometry (RFIC-ESI-MS). After the rodenticides were extracted from homogenized animal liver tissues with methanol-acetonitrile (10/90, v/v), the extracts were subjected to a solid-phase extraction (SPE) process using Oasis HLB cartridges. The IC separation was carried out on an IonPac AS11 analytical column (250 mm x 4.0 mm) using 10% methanol in a gradient of KOH solution at a constant flow rate of 1.0 mL/min. The objective compounds were ionized by negative ion pneumatically assisted electrospray and detected in the selected ion monitoring (SIM) mode. Warfarin was applied as an internal standard (IS) for the compensation of the losses in the course of sample processing and the sensitivity drift of the detector, linear calibration functions were calculated for all analytes. The relative average recoveries of the objective compounds spiked in animal liver tissues were between 83.4 and 104.9%. The limits of quantification (LOQs) were 0.2-1.0 ng/g for them. Within-day and day-to-day relative standard deviations (RSDs) were less than 10.4 and 13.3%, respectively. It was confirmed that this method could be used in a toxicological analysis. The coupling of IC to MS provided a new analytical tool to the analysts faced with the requirement of separating and analyzing indandione rodenticides in animal livers.

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.

Hydrophilicity nano-titania coating modified magnetic graphene oxide for pass-through cleanup of fipronil and its metabolites in human blood.

A novel hydrophilicity nano-titania coating modified magnetic graphene oxide (HTC-Mag-GO) has been synthesized. It has been evaluated in PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure for human blood prior to analysis of fipronil and its metabolites, i.e., fipronil sulphone, fipronil sulphide and fipronil desulfinyl by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Compared with the Oasis PRiME HLB cartridge, HTC-Mag-GO is much more effective for the removal of matrix effect. Furthermore, it is beneficial to protect the chromatographic column and ESI source by the HTC-Mag-GO PRiME pass-through cleanup procedure, resulting from the much cleaner blood samples. Under the optimum conditions, the results show higher cleanup efficiency of HTC-Mag-GO with recoveries in the range of 92.4%-108%. Especially, the HTC-Mag-GO is also evaluated for reuse (20 times) without much sacrifice of the cleanup efficiency. The limits of quantification (LOQs) for fipronil, fipronil sulphone, fipronil sulphide and fipronil desulfinyl are 8.9 ng/L, 7.2 ng/L, 8.0 ng/L and 42 ng/L, respectively. The developed method has also been successfully applied to monitoring fipronil and its metabolites in 120 blood samples, and fipronil sulphone is detected in six samples with concentrations in the range of 12.1 ng/L-106 ng/L. Further, the well validation results and the application to analysis of fipronil and its metabolites in real samples demonstrate the applicability to toxico kinetic studies and clinical studies.

Determination of perchlorate from tea leaves using quaternary ammonium modified magnetic carboxyl-carbon nanotubes followed by liquid chromatography-tandem quadrupole mass spectrometry.

The novel quaternary ammonium modified magnetic carboxyl-carbon nanotubes (QA-Mag-CCNTs) have been synthesised and characterized. QA-Mag-CCNTs were applied in magnetic dispersive solid phase extraction (Mag-dSPE) for preconcentration of perchlorate from tea leaves prior to liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) analysis. The Mag-dSPE procedure for preconcentration of perchlorate succeed in overcoming the flaw (containing target analyte randomly) of commercially available SPE cartridge. Under optimal conditions, the results showed higher extraction efficiency of QA-Mag-CCNTs, with recoveries between 85.2% and 107%. And the satisfactory precision with inter-day and intra-day RSD values were lower than 8.0%. Furthermore, QA-Mag-CCNTs were evaluated for reuse up to 20 times. The limit of quantification (LOQ) for perchlorate was 8.21 ng kg-1. The developed method was successfully applied in tea leaves for food-safety risk monitoring in Zhejiang province, China. The results showed the concentrations of perchlorate in 229 out of 240 collected samples were in the range of 0.082-988 µg kg-1. It was confirmed that QA-Mag-CCNTs were highly effective materials used for preconcentration of perchlorate.

Determination of five 4-hydroxycoumarin rodenticides in animal liver tissues by ion chromatography with fluorescence detection.

A novel analytical method is proposed for rapid simultaneous determination of five 4-hydroxycoumarin rodenticides in animal liver tissues by eluent generator reagent free ion chromatography (RFIC) with fluorescence detection. Rodenticides were initially extracted from homogenized animal liver tissues with ethyl acetate and the extracts subjected to a solid-phase extraction process using Oasis HLB cartridges. The IC separation was carried out on an IonPac AS11 analytical column (250 mm x 4.0 mm) using gradient KOH containing 10% acetonitrile as organic modifier at a constant flow rate of 1.0 mL/min. The analytes were detected by fluorescence at an excitation wavelength of 270 nm and an emission wavelength of 380 nm. The average recoveries of the objective compounds spiked in animal liver tissues were between 81% and 98%. The limits of quantification (LOQs) were 0.004-0.010 mg/kg for them. Within-day and day-to-day relative standard deviations (RSD) were less than 8.5% and 9.7%, respectively. It was confirmed that this method could be used in a toxicological analysis.

Simultaneous determination of five Alternaria toxins in cereals using QuEChERS-based methodology.

Two analytical approaches, including ultra-high performance liquid chromatograph linked with photo-diode array/fluorescence detector, and ultra-high performance liquid chromatography-tandem mass spectrometry, have been proposed for simultaneous determination of five Alternaria toxins in cereals, which both based on QuEChERS strategy. After QuEChERS extraction and salting out, the collected supernatant was subjected to an extra dispersive liquid-liquid microextraction step prior to quantitative analysis. Response surface methodology based on central composite design was employed to optimize the micro-extraction conditions. During photo-diode array/fluorescence detector method validation, satisfactory analytical characteristics, in terms of selectivity, recovery (72.7%-109.1%), precision (inter-day RSDs <9.6%), sensitivity (limits of quantification ranged from 2.1µgkg-1 to 120.0µgkg-1) and linearity (R2 all higher than 0.9984), were achieved. Mass spectrometry method was employed as a certified method for accuracy. The two methodologies were successfully applied to 71 samples including three different matrices and the quantitative results were compared. As the result of non-parametric test shown, the established two analytical approach exhibited comparable quantitative accuracy to each other.

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.