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The buckling and postbuckling behaviors of functionally graded graphene platelets-reinforced composite (FG-GPLRC) circular plates are studied based on the classical nonlinear von Karman plate theory. The effective Young’s modulus of the composite is estimated using the modified Halpin–Tsai micromechanical model, and the effective Poisson’s ratio is estimated by the rule of mixtures. Governing equations of the problem are derived based on the Hamilton principle and the numerical solutions of critical loads and postbuckling deflection–load relationships are calculated using the shooting method. Different from the existing linear buckling analysis based on the Terriftz criterion, the study with considering the global deformation of the plates, we analyze the influencing factors of the critical buckling loads and postbuckling paths of the FG-GPLRC circular plates subjected to uniformly distributed radial pressure. The results show that the content, geometric parameters and distribution pattern of GPL have great influences on the critical buckling loads and the post-buckling bearing capacities of the circular FG-GPLRC plates.

SEM (A) and TEM (B) images of NTMCu-MOFs.

Cerebral circulation time (CCT) and collateral score (CS) are associated with functional outcomes in acute ischemic stroke (AIS) patients after endovascular treatment (EVT), and may be related to each other. We aim to determine the relationship between CS and CCT on functional outcomes.We retrospectively enrolled consecutive patients with anterior circulation large vessel occlusion (LVO) AIS who received EVT. CS and CCT were measured based on digital subtraction angiography (DSA). We defined CS 0-2 and 3-4 as poor and good collateral status, respectively, and used change of CCT (cCCT), which was defined as the change of stroke side CCT (sCCT) versus healthy side CCT (hCCT). Mediating analysis was used to evaluate the influence of cCCT on the association between CS and functional outcomes, and ROC curves were further used to explore the predictive ability of the interaction between cCCT and CS for functional outcomes.A total of 100 patients were enrolled in the final analysis. A higher cCCT (r = -0.239; p = 0.017) was associated with lower CS, and cCCT mediated the association of CS with functional outcome. Logistic regression analysis found that CS, cCCT and cCCT-CS interactions were independently associated with functional outcome, and cCCT-CS interaction has better predictive performance, with a higher area under curve value than CS or cCCT alone (0.79 vs. 0.75 or 0.75).To our knowledge, this study provides the first report of the association of collateral status with cCCT, and their interaction effect on functional outcome in AIS-LVO patients receiving EVT.

Endovascular treatment (EVT) is the best treatment for acute ischemic stroke with large vessel occlusion (LVO) and makes it possible to analyze the blood contents from the occluded vascular compartments. In this study, we attempted to evaluate regional changes in blood gas values and electrolytes in the occluded vessels, aiming to determine whether these changes can predict outcomes in LVO patients receiving EVT.We prospectively observed 45 consecutive ischemic stroke patients with LVO of the anterior circulation who underwent EVT. We collected the arterial blood proximal to the occlusion site before and after EVT, and the blood within the core of the occluded vascular compartment (distal to the thrombus) and evaluated the labs for blood gas values and electrolytes. Femoral samples were obtained under physiological flow conditions to represent systemic arterial blood.Compared with the femoral arterial blood samples, significant decreases in K+, Ca2+, HCO3-, BE, HCT, tHbc, and TCO2 levels were observed in the proximal luminal blood before EVT. Decreases in K+ and Ca2+ levels were also observed in the proximal luminal blood after EVT. Proximal/femoral ratio of pH and Na+ was associated with short-term clinical outcomes at 72 hours after EVT. A higher proximal/femoral Na+ ratio was associated with successful recanalization. Further analysis after propensity score matching showed significant changes in blood gas and electrolyte among different arterial locations in ICA and MCA LVO participants. Linear regression analyses indicated that the proximal/femoral ratio of pH, Na+, pCO2, HCO3, and TCO2 before EVT were associated with decrease in NIHSS score at 72 hours in ICA-LVO group.Obvious changes in several parameters of arterial blood gas and electrolyte from the ischemic vasculature occur during hyperacute stroke. Proximal/femoral pH and Na+ ratio before EVT may be associated with short-term clinical outcome, which deserve to be further investigated.

Facile separation and enrichment of polychlorinated biphenyls (PCBs) in foods has been a constantly pursuing goal in food analytical chemistry. Here, a reusable ionic liquid functionalized magnetic graphene oxide nanocomposite (3D-IL@mGO), synthesized based on our previous study, was used as adsorbent for the preconcentration of PCBs in the magnetic dispersive solid phase extraction (Mag-dSPE) procedure. Comparing the proposed 3D-IL@mGO Mag-dSPE procedure with carboxylated multiwalled carbon nanotubes d-SPE method, the 3D-IL@mGO nanocomposite could be reused at least 16 times for the extraction of 11 PCBs from seafood samples without significant sacrifice of the extraction efficiency, which is more economical. Under the optimal conditions, a simple analytical method based on Mag-dSPE and gas chromatography-triple quadrupole mass spectrometry (GC–MS/MS) has been developed for the fast determination of 11 polychlorinated biphenyls (PCBs) in seafood. The LODs for 11 PCBs were in the range of 0.012 μg·kg−1–0.054 μg·kg−1. The recoveries were ranged from 80.0% to 112% with associated intra-day and inter-day relative standard deviations (RSDs) in the range of 2.7%-6.2% and 3.6%-7.3%, respectively. Furthermore, the proposed method was applied for the analysis of 11 PCBs in 240 seafood samples. The results showed that PCB 101, PCB 153 and PCB 204 were found in 18 seafood samples with concentrations ranged from 0.862 μg·kg−1 to 12.1 μg·kg−1. It is, therefore, concluded that the Mag-dSPE procedure combined with GC–MS/MS demonstrated the applicability for food-safety risk monitoring of PCBs in seafood samples.

A novel nano petal-shaped covalent organic frameworks modified magnetic polystyrene-divinylbenzene-glycidylmethacrylate (NP-COF@Mag-PS/DVB/GMA) microsphere has been synthesized. It is a perfect combination of high productivity of PS/DVB/GMA microspheres and excellent enrichment efficiency of COF particles, and the excellent properties of NP-COF@Mag-PS/DVB/GMA microspheres are characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). The sorbent can extract illicit drugs via the reverse-phase interactions provided by benzene ring on the polymer backbone and the hydrogen bonding interactions provided by functional group (-NH-) on the COF particles. Based on using NP-COF@Mag-PS/DVB/GMA as sorbents, an easiness-to-handle of magnetic dispersive solid phase extraction (Mag-dSPE) procedure is proposed for the simultaneous preconcentration of 12 illicit drugs from wastewater. The obtained results show high extraction efficiency of NP-COF@Mag-PS/DVB/GMA to illicit drugs with recoveries between 81.6 and 116%. Furthermore, a liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) method for the determination of 12 illicit drugs from wastewater at sub-ppt levels has been proposed and validated with the pretreatment of samples by Mag-dSPE. The limits of quantification (LOQs) for the 12 illicit drugs are between 0.40 and 4.90 ng/L. Validation results on linearity, specificity, trueness and precision, as well as on application to the analysis of 12 illicit drugs in ten real samples demonstrate the applicability to environment monitoring analysis.

A novel tetraethylenepentamine-modified graphene oxide/dispersive Fe3O4 magnetic composites (TEPA-MGO-dF) has been prepared through a simple and low-cost process using ultrasound-assisted hydrothermal method. The introduction of ultrasound in the reaction system is critical for reducing the occurrence of magnetic Fe3O4 nanoparticles aggregated together as well as GO sheets stacked layer by layer. Transmission electron microscopy analysis reveals that, with ultrasound, magnetic Fe3O4 nanoparticles own quasi-monodisperse size, and evenly bonded onto the surface of monodermic GO substrates. When used as adsorbents, TEPA-MGO-dF can high-efficiently remove allergenic disperse dyes from water with much higher adsorption capacities than tetraethylenepentamine-modified graphene oxide/aggregated Fe3O4 magnetic composites (TEPA-MGO-aF) prepared without ultrasound-assisted, indicating great potential for use in water treatment. The adsorption properties of TEPA-MGO-dF for the removal of allergenic disperse dyes in wastewater were deeply investigated. The results showed adsorption efficiency was highly pH dependent and adsorption mechanism of the dyes adsorption onto adsorbents could be related with two driving force, i.e., hydrogen bonding and π-π stacking interactions. Furthermore, various isotherms have been used to fit the adsorption data, which was effectively described by the Langmuir model with all R2 > 0.99, and the adsorption kinetic of dyes onto TEPA-MGO-dF can be predicted by the pseudo-second-order model.

During 2017–2018 Los Alamos National Laboratory, Lawrence Livermore National Laboratory and the China Institute of Atomic Energy collaborated in an interlaboratory 231Pa/235U radiochronometry exercise. The laboratories used different analytical methods to obtain a consensus model purification date for CRM U010 of December 28, 1958 ± 198 days and for CRM U850 of May 20, 1958 ± 363 days. These results agree with previously reported model dates using the 230Th/234U radiochronometer as well as the production histories of these materials. The concordance of interlaboratory data confirms the ability of laboratories to make reproducible radiochronometry measurements using distinct analytical approaches.

A rapid and sensitive method based on PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the simultaneous determination of 12 illicit drugs in human plasma was developed and validated. The clover-shaped nano-titania functionalized covalent organic frameworks (CSTF-COFs) has been evaluated in the PRiME pass-through cleanup procedure to remove blood phospholipids from plasma samples. Ion suppression effects can be dramatically reduced by CSTF-COFs based PRiME pass-through cleanup procedure. Under the optimal conditions, the results showed satisfactory recoveries between 85.8% and 109%. Acceptable precision and accuracy were also obtained with RSD values less than 15.0% and RE values below 13.3%. The limits of detections (LODs) of 12 illicit drugs were in the range of 0.018-0.360 µg/L. Furthermore, the PRiME CSTF-COFs cartridge could be conveniently regenerated and reused for 40-50 cycles. The proposed method was applied to real plasma samples from suspected drug abusers, which was proved to be reliable and robust for drug screening in clinical and forensic toxicology.

An analytical method for the detection of glucose in human exhaled breath by non-invasive condensation collection coupled with ion chromatography was developed. A self-designed exhaled breath condensation device was constructed, through which human exhaled breath was condensed and collected. And the glucose in collected human exhaled breath condensate (EBC) was analyzed by ion chromatography with a pulsed amperometric instrument. The standard EBC collection method was established, and the key factors such as cooling temperature and sampling flow rate during condensation collection were investigated deeply, and a good linear correlation between blood glucose levels and exhaled breath glucose levels was obtained. The intra-day precision was 3.37%, and the inter-day precision was 3.83%. Furthermore, EBC from healthy people and diabetic patients was collected in fasting state and after meal. We found the breath glucose level in healthy volunteers was 0.11-2.34 ng/L and that in diabetic patients was 0.23-135.92 ng/L. In after meal samples, the breath glucose level is 10-100 times higher than that of healthy subjects, which offering the prospect of a non-invasive approach to the monitoring of diabetes.

Developing different model age determination methods of uranium sample could get more information on insight into source and suspected use in nuclear forensic investigation. A procedure for the determination of model age of uranium sample using 231Pa/235U radiochronometer was reported. The 233Pa spike used in the procedure of 231Pa–235U model age determination was separated from in-house 237Np stock solution by using two TRU resin columns and three silica gel columns and calibrated by CRM U100. Model ages of CRM U010 and IRMM-1000b were presented. The model age of IRMM-1000b using 231Pa/235U radiochronometer were older than the literature reported results by 230Th/234U radiochronometer by amounts exceeded the expanded uncertainty.

A novel ionic liquid coupled with nano-titania coated modified magnetic GO composites (IL-Ti-Mag-GO) has been synthesized. It has been evaluated in an on-line pass-through cleanup procedure for human plasma prior to the analysis of aconitum alkaloids, i.e., mesaconitine, hypaconitine and aconitine, by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Under optimum conditions, the level of matrix effects can be dramatically reduced by the IL-Ti-Mag-GO on-line pass-through cleanup procedure, with satisfactory recoveries ranging from 81.2% to 108%. The trueness and precision of the developed method were satisfactory, with relative errors (REs) less than 19% and within- and between-run RSDs less than 7.0%. The limits of detection (LODs) and limits of quantification (LOQs) for aconitum alkaloids were in the range of 0.01–0.028 μg L−1 and 0.034–0.092 μg L−1, respectively. The developed analytical method has been successfully applied to the analysis of mesaconitine, hypaconitine and aconitine in two cases of suspected aconite poisoning, and the concentration of aconitine and hypaconitine in one sample was determined to be 0.076 μg L−1 and 0.069 μg L−1, respectively. The results demonstrate the applicability of the developed analytical method to clinical studies.

Two parameter approach –a new technique has been devised and tested to identify and distinguish Pu–bearing particles from U-bearing particles. This technique can be used to select rare and microscopic Pu-bearing particles from environmental samples, such as in soil, water, air (aerosol) and swipe samples from the wall of buildings and surfaces of machines in nuclear factories. Some amount of Pu and U standard reference materials were respectively added to cellulose nitrate (CN) solution and dropped some quantity of the solution on mica plates and dried to from CN sheets. CR-39 track detectors were used to record tracks of α particles emitted from the Pu or U particles in CN sheets. After etching of CR-39 plates, α track stars were developed and can be seen under optical microscope. Tracks shapes of α particles in the stars were investigated. We found that at certain interval of etching time, the tip part of α tracks of Pu was very sharp, but the tip part of α tracks of U was blunted with spherical tips. The ratio Rt/Ro of the diameter (Rt) of tip point to the diameter (Ro) of the round track in center area of star is a superior parameter to identify Pu from U particles. The Rt/Ro measurements should be carried at a certain distance from the center point. The two parameter approach has been using in nuclear safeguards and nuclear forensics to analyze isotopic compositions and age of Pu samples.

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.

Ming Lei,1 Guang-Yuan Yu,2 Yong-Gang Zhao,3 Ji-Ping Wang,1 Su-Yun Feng1 1Center of Hair Transplantation, Department of Burn and Plastic Surgery, The Fourth Medical Center of the General Hospital of PLA, Beijing, People’s Republic of China; 2Department of Dermatology, The Fourth Medical Center of the General Hospital of PLA, Beijing, People’s Republic of China; 3First Department of Surgery, Beijing Armed Police Corps Hospital, Beijing, People’s Republic of ChinaCorrespondence: Ji-Ping WangCenter of Hair Transplantation, Department of Burn and Plastic Surgery, The Fourth Medical Center of the General Hospital of PLA, No. 51 of Fucheng Road, Haidian District, Beijing, 100048, People’s Republic of ChinaTel +86 10-66867304Email wangjp693587@163.comObjective: This study aims to establish the concept of invalid extraction rates in follicular unit extraction and evaluate its clinical value.Methods: The present study involved 30 patients with alopecia. Three young surgeons (nominated A, B, and C) each performed follicular unit extraction on a randomly selected portion of the donor site of each patient for ten minutes. The outcomes were separately recorded and calculated, and converted to an invalid extraction rate for each surgeon using the formula, “invalid extraction rate = 1 − successfully extracted follicular units/actually extracted units × 100%.”Results: The follicular unit invalid extraction efficiency of each surgeon gradually declined. The average efficiency level of surgeon B was evaluated as excellent, while the levels of surgeons A and C were evaluated as good.Conclusion: With experience, surgeons can speed up the process of follicular unit extraction and gradually increase performance quality through both extraction speed and success rate.Keywords: follicular unit extraction, operating level, evaluation

The determination of uranium isotope ratios in uranium particle is an essential technique in the analysis of environmental samples for nuclear safeguards. At present, mass spectrometry has been widely used to measure isotope ratios of uranium particles. We developed a new analytical method for measuring minor isotope ratios of individual uranium particles directly. The technique includes single particle identification by energy dispersive X-ray spectrometer (EDX), transfer by scanning electron microscope (SEM) combined with micromanipulator and isotope ratios analysis with accelerator mass spectrometry (AMS). The minor isotope ratios of individual uranium particles with four isotopic abundances and different sizes from certified reference materials were measured by AMS. The results show that the relative error (RE, i.e., the deviation of measured value from the certified value) of 234 U/235 U and 234 U/236 U isotope ratios was 9.0% and 19.3%, respectively, and the relative standard deviation (RSD) was within 9.9% and 16%, respectively. The minimum particle determined was about 2 μm. The method was found to be an alternative analytical means for nuclear safeguards.

Colorimetric sensors for the rapid detection of numerous analytes have been widely applied in many fields such as biomedicine, food industry and environmental science due to their highly sensitive and selective response, easy operation and visual identification by naked eyes. In this review, the recent progress of the colorimetric sensors based on the magnetic nanomaterials with unique nanozymes-like catalytic activity (magnetic nanozyme) and their colorimetric sensing applications are presented. Emerging magnetic nanozyme-based colorimetric sensors, such as metal oxide/sulfides-based, metal-based, carbon-based, and aptamer-conjugated magnetic nanomaterials, offer many desirable features for target analytes detection. And due to the unique nanoscale physical-chemical properties, magnetic nanozymes have been used to mimic the catalytic activity of natural enzymes such as peroxidases, oxidases and catalases. This review also highlights the catalytic mechanisms of enzyme-like reactions, and promising colorimetric sensing system for the detection of chemical compounds like H2O2, pesticide, ascorbic acid, dopamine, tetracyclines, perfluorooctane sulfonate, phenolic compounds, heavy metal ion and sulfite have been deeply discussed. In addition, the remaining challenges and future directions in utilizing magnetic nanozyme for colorimetric sensors are addressed.

The growing use of non-steroidal anti-inflammatory drugs (NSAIDs) has seriously affected human health and ecosystems, as a result, the World Health Organization (WHO) has regarded them as emerging contaminants. NSAID’s polar nature and trace amount present in wastewater make their extraction and determination challenging in modern analytical science. Therefore, regarding the need, we herein report a rapid, sensitive and selective in-syringe solid-phase extraction (SPE) method coupled with ultrahigh performance liquid chromatography and UV detector for the determination of seven NSAIDs in environmental water samples. Specifically, the NSAIDs in water samples were directly extracted by using synthesized porous covalent organic framework functionalized poly (styrene-divinyl benzene-glycidylmethacrylate) composite (COF@PS-GMA) without further cleanup procedures. The adsorption of NSAIDs on COF@PS-GMA sorbent was investigated by using adsorption isotherms and kinetic studies. Various parameters, including amount of sorbent, pH of the samples, the volume of desorption solvent, and desorption time that were involved in in-syringe SPE were optimized. Under the optimized conditions, good linearity was observed at 0.005–5.0 μg mL−1 with method quantification limits (LOQs) estimated between 0.54–2.74 μg L−1. The recoveries of the seven NSAIDs at the level of 0.5, 5.0 and 20.0 μg L−1 were ranging from 84.3% to 99.6%.

In this study, three batches of nano-titania functionalized covalent organic frameworks were acquired depending on different solvothermal reaction stages (24 h, 48 h and 72 h), which were named as single roll-up shaped nano-titania functionalized COFs (SSTF-COFs), double roll-up shaped nano-titania functionalized COFs (DSTF-COFs) and clover-shaped nano-titania functionalized covalent organic framework (CSTF-COFs), respectively. After comparing their extraction performances, the more efficient and stable CSTF-COFs were selected as sorbent for the dispersive solid phase extraction (dSPE) of eight target N-nitrosamines in drinking water, followed by the determination with liquid chromatography-tandem quadrupole mass spectrometry (LC–MS/MS). Owing to the introduction of hydroxy groups, CSTF-COFs showed high extraction efficiency for N-nitrosamines with a wide range of polarities through hydrogen bonding interaction, hydrophobic interaction and hydrophilic interaction. Under optimum conditions, the developed method provided relatively low limits of detection (0.13–2.45 ng/L) and satisfactory recoveries (88.6–105.5%), with relative standard deviations (RSDs) less than 8.3%. Therefore, with the assistance of CSTF-COFs, trace levels of N-nitrosamines were quantitatively and sensitively determined in 31 out of 460 bottled drinking water samples in a sensitive and convenient way.

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.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously found in the environment and have been proved to be prospectively associated with the risk of cancer. In this study, a simple method based on pipette-tip solid phase extraction (PT-SPE) and gas chromatography-mass spectrometry (GC–MS) has been firstly developed for the determination of 16 PAHs in human whole blood. Three-dimensional ionic liquid-ferrite functionalized graphene oxide nanocomposite (3D-IL-Fe3O4-GO) was used as sorbent in PT-SPE. Compared with conventional SPE method, the PT-SPE method was solvent-saving (1.0 mL), reusable (at least 10 times) and required less blood sample (200 μL). Affecting parameters on extraction efficiency were investigated and optimized. Under the optimized conditions, a good linearity was obtained and the recoveries of 16 PAHs at three spiked levels ranged from 85.0% to 115%. The limits of quantification (LOQs) were in the range of 0.007-0.013 μg/L. Furthermore, the developed method was successfully applied to the analysis of 16 PAHs in 14 human blood samples. The results showed that the predominant PAHs in human whole blood was low-molecular-weight PAHs, with the rank order phenanthrene (PHE)> naphthalene (NAP)> fluorene (FLU)> fluoranthene (FLT)> pyrene (PYR). Because of its simplicity, accuracy and reliability, the PT-SPE method combined with GC–MS demonstrated the applicability for clinical analysis and provided more information for PAHs exposure studies.

A novel double layer pipette tip magnetic dispersive solid phase extraction (DPT-MSPE) based on polyamidoamine-functionalized magnetic carbon nanotubes (PAMAM@Mag-CNTs) was developed for the purification of fifteen toxic alkaloids in meat dishes and vegetable dishes. PAMAM@Mag-CNTs were synthesized through direct reaction between the carboxy group on the surface of the Mag-CNTs and the peripheral amino group of the polyamidoamine (PAMAM) dendrimers. The magnetism of PAMAM@Mag-CNTs simplified the post-processing during preparation of the sorbent, and reinforced the interaction between the sorbents and the analytes during the cleanup procedure. An ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) coupled with DPT-MSPE method has been developed to determine fifteen alkaloids in meat dishes and vegetable dishes. Under the optimal conditions, satisfactory recoveries, i.e., 83.4–125% for meat dishes and 84.2–122% for vegetable dishes, were obtained due to the high cleanup efficiency of the DPT-MSPE. Furthermore, the method, which displays good linearity (r ≥ 0.9991), acceptable precision (RSD < 8%), and low limits of quantification (0.054–1.058 ng g−1), has been successfully applied to several food samples, and it was confirmed that PAMAM@Mag-CNTs DPT-MSPE was a highly effective extraction method for alkaloids in cooked food samples.

A simple and effective method based on the PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure followed by ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry (UHPLC-MS/MS) was developed for analyzing fipronil and its metabolites in seafoods. Matrix effects in seafoods were effectively improved. Validation results demonstrated that this method was suitable for monitoring fipronil residues in seafoods.

N-Nitrosamines (NAs) are potent carcinogens and have been found in food products. Herein we report a simple tandem liquid-phase extraction (TLPE) method coupled with high-performance liquid chromatography (HPLC) for the determination of trace N-nitrosamines (NAs) in food products. The TLPE method is based upon the tandem implementation of pressurized hot water extraction (PHWE) and dispersive liquid–liquid microextraction (DLLME). The target analytes were first extracted with pressurized hot water, and then concentrated into an organic phase (n-octanol) in the DLLME procedure. The TLPE-HPLC system allowed the analytes to be extracted, concentrated and analyzed in a single step with minimal manipulation of the sample preparation, with an overall analysis time of 25 min. The optimized method showed good linearity (r2 ≥ 0.981) and satisfactory recoveries (74–117%) with good repeatability of the extractions (RSDs below 12.8%, n = 5). The limits of detection (LODs) for all nitrosamines in salted duck eggs were in the range of 0.08–0.55 μg kg−1.

Correction for ‘In situ controllable synthesis of graphene oxide-based ternary magnetic molecularly imprinted polymer hybrid for efficient enrichment and detection of eight microcystins’ by Sheng-Dong Pan et al., J. Mater. Chem. A, 2015, 3, 23042–23052.

In 2014 the United States Department of Energy and the China Institute of Atomic Energy collaborated in a study measuring the model ages of uranium certified reference materials. Lawrence Livermore National Laboratory (LLNL) and Los Alamos National Laboratory (LANL), and the Chinese Institute of Atomic Energy (CIAE) determined 230Th–234U model ages for uranium certified reference materials U010 and U850. The aim of this work was to collaborate with CIAE and compare methods for measuring the age of bulk uranium materials using the 230Th–234U radiochronometer. Accurate results for age-dating depend on the accurate calibration of the tracer materials (e.g., 229Th and 233U) used for the isotope dilution mass spectrometry (IDMS) analyses. To facilitate inter-comparison of results, samples of a 230Th standard reference material were distributed to each laboratory for 229Th tracer inter-calibration. The resulting 230Th–234U model ages from this collaboration for U010 ranged from March 1956 to January 1959, which agree with the known material production date of June 5th, 1958. The determined model ages for U850 were from December 1955 to October 1957, which agree with the material production date of December 31, 1957. All three laboratories used independent methods to determine model ages for uranium standards that agree with known production ages and with previously reported results.