Magnetic phenolic resin core-shell structure derived carbon microspheres for ultrafast magnetic solid-phase extraction of triazine herbicides

In this study, monodisperse magnetic carbon microspheres were successfully synthesized through the carbonization of phenolic resin encapsulated Fe₃O₄ core-shell structures. The magnetic carbon microspheres showed high performance in ultrafast extraction and separation of trace triazine herbicides from environmental water samples. Under optimized conditions, both the adsorption and desorption processes could be achieved in 2 min, and the maximum adsorption capacity for simazine and prometryn were 387.6 and 448.5 μg/g. Coupled with high-performance liquid chromatography-ultraviolet detection technology, the detection limit of triazine herbicides was in the range of 0.30–0.41 ng/mL. The mean recoveries ranged from 81.44 to 91.03% with relative standard deviations lower than 7.47%. The excellent magnetic solid-phase extraction performance indicates that magnetic carbon microspheres are promising candidate adsorbents for the fast analysis of environmental contaminants.     

Fe3O4@MOF-808磁性固相萃取结合高效液相色谱法测定大米中3种二苯醚类除草剂

利用溶剂热法构筑了Fe₃O₄@MOF-808吸附剂,将其用于大米中除草醚(NIT)、乙氧氟草醚(OXY)和甲羧除草醚(BIF)3种二苯醚类除草剂的富集,结合高效液相色谱法,建立了大米中该类除草剂的分析方法。研究通过傅里叶变换红外光谱、X射线衍射仪、扫描电子显微镜以及振动样品磁强计对构筑的磁性吸附剂的结构、表面形貌及磁强度进行表征。表征结果显示,球形的Fe₃O₄纳米颗粒与八面体形貌的MOF-808成功复合,Fe₃O₄@MOF-808饱和磁化强度可达40.35 emu/g,可以满足磁性固相萃取的需求;对吸附剂用于大米中3种二苯醚类除草剂富集的磁性固相萃取条件(吸附剂用量、吸附时间、洗脱溶剂种类以及洗脱体积)进行了优化。优化结果显示,25 mg吸附剂在6 min内即可达到对目标物的完全吸附,洗脱溶剂采用0.5 mL×2的甲醇。在最优的磁性固相萃取条件下,结合高效液相色谱-紫外检测法,建立了大米中3种二苯醚类除草剂的分析方法。方法在2~300 μg/L范围内线性关系良好(r > 0.998), NIT、OXY、BIF的检出限和定量限依次为0.6、0.6、0.4 μg/kg和2.0、2.0、1.5 μg/kg,在5、10和20 μg/kg 3个加标水平下的回收率为87.3%~96.7%,相对标准偏差不超过10.8%,且富集因子在25~29之间。将所建方法用于大米中NIT、OXY、BIF的分析,各样品均未检出这3种二苯醚类除草剂。该方法具有操作简单、快速、准确的特点,适用于大米样品中除草剂的残留分析。     

Function of Tetrapyrroles,Regulation of Tetrapyrrole Metabolism and Methods for Analyses of Tetrapyrroles

Tetrapyrroles are essential cofactors and pigments. Photosynthetic organisms share the use of the highest diversity of tetrapyrrole end products. This report intends to call readers’ attention to the recent achievements in research on tetrapyrrole biosynthesis and the current hot topics in tetrapyrrole biosynthesis, including posttranslational control mechanisms and intracellular signaling between the nucleus and the two organelles, plastids and mitochondria. Moreover, the functions of tetrapyrroles in the photosynthetic organisms and valuable information about the current analytical techniques to determine steady state levels of tetrapyrrole intermediates from cyanobacteria, green algae and plant will be surveyed.     

QuEChERS-气相色谱-质谱法测定土壤中6种酰胺类除草剂残留

建立了QuEChERS-气相色谱-质谱同时测定土壤中乙草胺(acetochlor)、甲草胺(alachlor)、异丙甲草胺(metolachlor)、吡草胺(metazachlor)、丁草胺(butachlor)和丙草胺(pretilachlor)6种酰胺类除草剂的分析方法。土壤中残留的酰胺类除草剂用10 mL去离子水、10 mL乙腈和4 g NaCl提取,用N-丙基乙二胺(PSA)、C18、石墨化炭黑(GCB)和无水硫酸镁(MgSO4)净化,然后用气相色谱-质谱联用法测定。采用HP-5MS弱极性石英毛细管柱进行气相色谱分离,在电子轰击电离(EI)源模式下以选择离子监测(SIM)扫描模式检测。结果表明,6种酰胺类除草剂在0.01~1.00 mg/L范围内呈良好线性关系,相关系数(r)为0.999 6~1.000 0。在加标水平为0.025、0.10和0.50 mg/kg时,6种酰胺类除草剂的平均回收率为92.0%~108%,相对标准偏差为1.64%~8.25%(n=3)。方法的检出限为0.002~0.006 mg/kg,定量限为0.005~0.02 mg/kg。同常用的气相色谱-电子捕获检测(GC-ECD)法比较,该法可提高抗干扰能力,使6种酰胺类除草剂得到较好分离。方法所使用的有机溶剂种类和用量少,操作简单、快速,具有应用价值。     

功能化离子液体/离子液体分散液-液微萃取测定水中苯氧羧酸类除草剂

建立了功能化离子液体/离子液体分散液-液微萃取(FIL/IL-DLLME)测定水中4种苯氧羧酸类除草剂的农药残留分析方法.离子液体[C4MIMBF4]有助于难溶于水的[C6HyMIMTf2N]在水相中形成液滴.离子对[LiWf2N]的引入有利于提高功能离子液体对分析物的提取效率,对影响萃取效率的重要因素进行选择和优化,最佳条件为:100 μL[C6HyMIMTf2N])作为提取剂,100 μL[C4MIMBF4]作为分散剂,在30℃下超声5 min,[LiTf2N]浓度为5％和样品溶液的pH=2.在最佳优化条件下,5～500 μg/L范围内线性良好,相关系数为0.9953 ～0.9996;对自来水、河水、田间水进行浓度为10和20 μg/L添加回收实验,回收率为70.2％～107.5％,相对标准偏差RSD＜10％,检出限为0.05 ～0.2 μg/L,得到满意的结果,说明本方法对于实际样本的检测具有可行性.     

Self‐assembled magnetic nanoparticle supported zeolitic imidazolate framework‐8: An efficient adsorbent for the enrichment of triazine herbicides from fruit,vegetables, and water

Zeolitic imidazolate frameworks have positive surface charges and high adsorption capabilities. In this work, zeolitic imidazolate frameworks‐8 and negatively charged magnetic nanoparticles were self‐assembled by electrostatic attraction under sonication. The extraction performance of the synthesized hybrid material was evaluated by using it as a magnetic adsorbent for the enrichment of triazine herbicides in various sample matrices prior to analysis using ultrafast liquid chromatography. The main parameters, that is, extraction time, adsorbent dosage, salt concentration, and desorption conditions, were evaluated. Under the optimum conditions, good linear responses from 2.5 to 200 ng/mL for atrazine (simazine) and 1 to 200 ng/mL for prometryn (ametryn), with correlation coefficients (R ²) higher than 0.9992 were obtained. The detection limits of the method (S/N = 3) were 0.18–0.72 ng/mL. The proposed method was successfully used to determine triazine herbicides in six samples, namely, apple, pear, strawberry, pakchoi, lettuce, and water. The amounts of simazine in all the fruit and vegetable samples were 10.8–25.2 ng/mL. The recoveries of all the analytes were 88.0–101.9%, with relative standard deviations of less than 8.8%.     

Combination of ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the determination of triazine herbicides in water samples

A temperature-controlled ionic liquid dispersive liquid-phase microextraction in combination with high performance liquid chromatography was developed for the enrichment and determination of triazine herbicides such as cyanazine,simazine,and atrazine in water samples.1-Octyl-3-methylimidazolium hexafluorophosphate([C8MIM][PF6]) was selected as the extraction solvent.Several experimental parameters were optimized.Under the optimal conditions,the linear range for cyanazine was in the concentration range of 0.5–80 mg/L and the linear range for simazine and atrazine was in the range of1.0–100 mg/L.The limit of detection(LOD,S/N = 3) was in the ranges of 0.05–0.06 mg/L,and the intra day and inter day precision(RSDs,n = 6) was in the ranges of 3.2%–6.6% and 4.8%–8.9%,respectively.Four real water samples were analyzed with the developed method,and the experimental results showed that the spiked recoveries were satisfactory.All these exhibited that the developed method was a valuable tool for monitoring such pollutants.     

Novel solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods for the rapid analysis of triazine herbicides in real waters

Novel, fast, selective, eco‐friendly and reproducible solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods were developed and validated for the analysis of triazine herbicides (atrazine and secbumeton) in stream and lake waters. The retention times of atrazine and secbumeton were 7.48 and 8.51 min. The solid‐phase membrane tip extraction was carried out in semiautomated dynamic mode on multiwall carbon nanotubes enclosed in a cone‐shaped polypropylene membrane cartridge. Acetone and methanol were found as the best preconditioning and desorption solvents, respectively. The extraction and desorption times for these herbicides were 15.0 and 10.0 min, respectively. The percentage recoveries of atrazine and secbumeton were 88.0 and 99.0%. The linearity range was 0.50–80.0 μg/L (r² > 0.994), with detection limits (<0.47 μg/L, S/N = 3) and good reproducibility (<8.0%). The ease of operation, eco‐friendly nature, and low cost of solid‐phase membrane tip extraction made these methods novel. The Solid‐phase membrane tip extraction method was optimized by considering the effect of extraction time, desorbing solvents and time.