Fe3O4-grafted nitrogen-doped graphene (Fe3O4/N-G) nanomaterials were synthesized by chemical co-precipitation method, and its adsorption properties were discussed preliminarily.It was demonstrated that the adsorption of parachlormetaxylenol on Fe3O4/N-G was not limited to uniform monolayer adsorption and the adsorption kinetic followed the pseudo-second-order kinetic mode.Then, an ultrasound-assisted magnetic solid-phase extraction with Fe3O4/N-G as the magnetic adsorbent has been developed for the determination of four compounds including triclosan, chloroxylenol, hexachlorobenzene and 2,2′,4,4′,5,5′-hexachlorobiphenyl in environmental water samples, in combination with gas chromatography coupled to tandem mass spectrometry.Several factors related to extraction efficiencies, such as the amount of adsorbent, extraction time, sample pH and desorption conditions were investigated.The proposed preparation procedure was as follows: 6.0 mg of Fe3O4/N-G was dispersed into 100 mL of water sample under ultrasound.After 15 s, the Fe3O4/N-G carrying four compounds was separated from the water sample by an external magnetic field.Then, the targets were eluted from Fe3O4/N-G with 3 mL of ethanol and 2 mL of dichloromethane, sequentially.Finally, the eluent was dried under a mild stream of nitrogen and reconstituted with methanol and dichloromethane (1∶1, V/V) for the subsequent GC-MS/MS analysis.Under the optimized condition, an excellent linearity was observed in the range of 0.1-10 ng/L for the four compounds, with the correlation coefficients ranging from 0.9983 to 0.9999.The limits of detections (S/N=3) ranged from 0.05 to 0.6 ng/L and the limits of quantity (S/N=10) ranged from 0.2 to 2.4 ng/L.The mean recoveries at three spiked levels ranged from 68.2% to 99.6%.The relative standard deviations (RSDs) of intraday and interday were in the range of 3.3%-6.9% and 3.4%-9.4% (n=6), respectively.The proposed method was demonstrated to be simple and feasible for the trace analysis of antimicrobial agents and organochlorine contaminants in environmental water samples.

Objective To investigate the relationship between low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (LHR) and asymptomatic carotid plaques and their stability in high-risk stroke population.Methods Between December 2012 and April 2015,a total of 39 944 permanent resident population ≥40 years were used as subjects of the survey from 11 rural communities in Haitou Town,Banzhuang Town and Tashan Town,Ganyu District,and 9 urban communities in Xinpu District and Haizhou District,Lianyungang City using epidemiological survey method of cluster sampling.Excluding those who took lipid-lowering drugs within 3 months and had a history of stroke or transient ischemic attack,6 592 people at high risk of stroke were finally screened out.Ultrasound was used to detect carotid plaques.The subjects were divided into plaque-free group and plaque group.The latter was further divided into stable plaque group and unstable plaque group.Multivariate logistic regression analysis was used to evaluate the independent risk factor for carotid plaques and their stability.The odds ratio (OR) and 95％ confidence interval (CI) were calculated.Receiver Operating Characteristic (ROC) curve was used to evaluate the prediction efficiency of LHR on carotid plaques.Results Multivariate logistic regression analysis showed that low-density lipoprotein cholesterol (LDL-C) was an independent risk factor for carotid plaques,while high-density lipoprotein cholesterol (HDL-C) was an independent protection factor of carotid plaques.Using the lowest quintile (Q1) of LHR as a reference,carotid plaque risk increased significantly with the increasing LHR (Q2:OR 1.448,95％ CI 1.082-1.937,P =0.013;Q3:OR 2.414,95％ CI 1.754-3.322,P＜0.001;Q4:OR 2.939,95％ CI 1.945-4.441,P＜0.001;Q5:OR 4.884,95％ CI 3.143-7.115,P＜0.001).ROC curve analysis showed that the area under the curve (AUC) of LHR predicting carotid plaques was 0.795 (95％ CI 0.792-0.807;P＜ 0.001),and the optimal cut-off value was 3.00 (sensitivity 68.37％,specificity 75.65％).LHR ≥3.92 (LHR in the Q4 and Q5 subgroups) was an independent risk factor for unstable carotid plaques (OR 2.915,95％ CI 2.104-4.040;P＜0.001).The AUC of the LHR predicting unstable carotid plaques was 0.658 (95％ CI 0.633-0.684;P＜0.001).Conclusions LHR was an independent predictor of carotid plaques in high-risk stroke patients.It had higher predictive value for carotid plaques,and its conversion threshold for promoting plaque formation was 3.00.When LHR was ≥3.92,there was a significant increase in the risk of unstable carotid plaques.