Evolution of dispersive liquid–liquid microextraction method

Dispersive liquid–liquid microextraction (DLLME) has become a very popular environmentally benign sample-preparation technique, because it is fast, inexpensive, easy to operate with a high enrichment factor and consumes low volume of organic solvent. DLLME is a modified solvent extraction method in which acceptor-to-donor phase ratio is greatly reduced compared with other methods. In this review, in order to encourage further development of DLLME, its combination with different analytical techniques such as gas chromatography (GC), high-performance liquid chromatography (HPLC), inductively coupled plasma-optical emission spectrometry (ICP-OES) and electrothermal atomic absorption spectrometry (ET AAS) will be discussed. Also, its applications in conjunction with different extraction techniques such as solid-phase extraction (SPE), solidification of floating organic drop (SFO) and supercritical fluid extraction (SFE) are summarized. This review focuses on the extra steps in sample preparation for application of DLLME in different matrixes such as food, biological fluids and solid samples. Further, the recent developments in DLLME are presented. DLLME does have some limitations, which will also be discussed in detail. Finally, an outlook on the future of the technique will be given.     

Molecularly imprinted polymer layer-coated silica nanoparticles toward dispersive solid-phase extraction of trace sulfonylurea herbicides from soil and crop samples

This paper reports the preparation of metsulfuron-methyl (MSM) imprinted polymer layer-coated silica nanoparticles toward analysis of trace sulfonylurea herbicides in complicated matrices. To induce the selective occurrence of surface polymerization, the polymerizable double bonds were first grafted at the surface of silica nanoparticles by the silylation. Afterwards, the MSM templates were imprinted into the polymer-coating layer through the interaction with functional monomers. The programmed heating led to the formation of uniform MSM-imprinted polymer layer with controllable thickness, and further improved the reproducibility of rebinding capacity. After removal of templates, recognition sites of MSM were exposed in the polymer layers. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio. There was also evidence indicating that the MSM-imprinted polymer nanoparticles compared with nonimprinted polymer nanoparticles had a higher selectivity and affinity to four structure-like sulfonylurea herbicides. Moreover, using the imprinted particles as dispersive solid-phase extraction (DSPE) materials, the recoveries of four sulfonylurea herbicides determined by high-performance liquid chromatography (HPLC) were 80.2-99.5%, 83.8-102.4%, 77.8-93.3%, and 73.8-110.8% in the spiked soil, rice, soybean, and corn samples, respectively. These results show the possibility that the highly selective separation and enrichment of trace sulfonylurea herbicides from soil and crop samples can be achieved by the molecular imprinting modification at the surface of silica nanoparticles.     

Technologies Employed in the Treatment of Water Contaminated with Glyphosate: A Review

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide with several commercial formulations that are used generally in agriculture for the control of various weeds. It is the most used pesticide in the world and comprises multiple constituents (coadjutants, salts, and others) that help to effectively reach the action’s mechanism in plants. Due to its extensive and inadequate use, this herbicide has been frequently detected in water, principally in surface and groundwater nearest to agricultural areas. Its presence in the aquatic environment poses chronic and remote hazards to human health and the environment. Therefore, it becomes necessary to develop treatment processes to remediate aquatic environments polluted with glyphosate, its metabolites, and/or coadjutants. This review is focused on conventional and non-conventional water treatment processes developed for water polluted with glyphosate herbicide; it describes the fundamental mechanism of water treatment processes and their applications are summarized. It addressed biological processes (bacterial and fungi degradation), physicochemical processes (adsorption, membrane filtration), advanced oxidation processes—AOPs (photocatalysis, electrochemical oxidation, photo-electrocatalysis, among others) and combined water treatment processes. Finally, the main operating parameters and the effectiveness of treatment processes are analyzed, ending with an analysis of the challenges in this field of research.     

离子液体-基质固相分散-超声雾化-固相萃取结合高效液相色谱法检测人参中三嗪类除草剂

采用固载1-甲基-3己基咪唑六氟磷酸([C6MIM][PF6])的硅胶作为基质固相分散剂,与超声雾化提取及C18固相萃取相结合,对人参提取物进行提取和净化;采用高效液相色谱法,建立了人参中5种三嗪类除草剂的检测方法.样品前处理的最优条件为:300 mg人参粉末与150 mg硅胶([C6MIM][PF6]含量2.0 mmol/g)研磨5 min,以20.0 mL去离子水(pH 7,含1.0％ NaCl)超声雾化提取10 min,再以5.0 mL乙腈洗脱萃取小柱(300 mg C18).实验结果表明,目标物的检出限为0.020～0.035 g/g,线性相关系数r2≥0.9992,实际样品加标回收率为78.2％～95.4％,相对标准偏差为3.5％ ～6.0％.本方法快速高效、净化效果好、提取率高,为中药中农药残留的检测提供了新的样品前处理方法.     

预衍生化-气相色谱-质谱法测定水中酸性除草剂

向水样中逐滴加硫酸(1+2)调节至pH<2,用二氯甲烷先后提取3次。合并的提取液用无水酸性硫酸钠脱水,并蒸缩至约1 mL后用吹氮法蒸干。加入丙酮溶解残渣后,在催化剂碳酸钾存在下用五氟苄基溴进行衍生化,溶于正己烷中的衍生产物用极性硅胶柱进行纯化。先用甲苯-正己烷(1+6)混合溶剂淋洗净化柱以除去衍生产物中的干扰副产物,然后用甲苯-正己烷(9+1)从净化柱上将目标化合物洗脱,所得洗脱液经浓缩并加入八氟联苯作内标后供气相色谱-质谱分析。气相色谱中用HP-5MS毛细管色谱柱进行分离,质谱分析中用负化学离子源及选择离子扫描(SIM)。此方法对测定的14种酸性除草剂的检出限(3S/N)均小于10 ng.L-1。对所述14种除草剂做了回收试验,结果在66.0%~117.0%之间,测定7次的相对标准偏差均小于9%。     

Performance comparison of dispersive solid‐phase extraction and multiplug filtration cleanup methods for the determination of tefuryltrione in plant and environmental samples using UHPLC–MS/MS

The detection frequencies of tefuryltrione, a new type of 4‐hydroxyphenyl‐pyruvate dioxygenase inhibitor herbicide, are rarely reported, probably because of the paucity of analytical methods. Herein, an effective and sensitive analytical method has been developed to detect tefuryltrione in vegetables (tomato and cucumber), cereals (rice and corn), soil, and water by ultra high performance liquid chromatography coupled with tandem mass spectrometry. Comparisons of the performances of dispersive solid‐phase extraction and multiplug filtration cleanup methods were carried out for tefuryltrione in complex matrices. Extraction solvents and purification sorbents were further optimized for dispersive solid‐phase extraction. Tefuryltrione was analyzed with electrospray ionization in the positive mode within 2.0 min. Mean recoveries for tefuryltrione were 75.4–108.9% with relative standard deviations less than 11.0% at three fortification levels (10, 100, 500 μg/kg) in the sample matrixes. Limits of quantification ranged from 0.70 to 5.12 μg/kg, and an excellent linearity (R ² ≥ 0.9902) was obtained for tefuryltrione at concentrations of 5–1000 μg/L. The results showed that the developed dispersive solid‐phase extraction method could serve as an effective, sensitive, and robust method for routine monitoring of tefuryltrione residue in plants and environmental samples.     

The influence of mercury(II) on the extraction efficiency of herbicides from water

In this work, the effect of Hg(II) on the extraction efficiency of triazine and phenylurea herbicides from water samples was tested. The results showed that in the presence of Hg(II), the recoveries of the s-triazine herbicides (except hexazinon) from styrene divinylbenzene (SDVB) cartridges were significantly reduced using acetonitrile as the elution solvent, whereas acidified methanol quantitatively eluted all the herbicides. Consequently, the loss in the recoveries was not due to degradation of the compounds but rather due to irreversible adsorption onto the resin. The adsorption is probably due to ternary complex formation between the compounds, Hg(II) and the polymeric resin. The chemical structure and the basicity of the compounds affected their interaction with Hg(II). When using octadecyl (C18) cartridges, only atraton was affected. Mercury did not affect the liquid–liquid extraction of the herbicides. The findings suggest that acidic methanol is a suitable elution solvent of s-triazines from mercury-loaded water samples.     

Design,synthesis and evaluation of novel cis-p-menthane type Schiff base compounds as effective herbicides

p-Menthane type monoterpene derivatives were identified as bio-based compounds with high herbicidal activities. In order to search novel p-menthane type monoterpene derivatives in good performance, a series of novel cis-p-menthane type Schiff base derivatives were designed and synthesized. All target products were easily available novel compounds and characterized by FT-IR, ¹H NMR, ¹³C NMR and ESI⁺- MS. Their pre-emergence herbicidal activities against annual ryegrass were evaluated. The bioassays indicated that most of the target compounds displayed excellent herbicidal activities in pre-emergence treatment.     

分子印迹磁固相萃取/气相色谱法分析环境水样中5种酰胺类除草剂残留

以丁草胺为假模板分子,丙烯酰胺为功能单体,利用四氧化三铁磁性纳米微球成功制备了具有特异性识别能力的磁性分子印迹聚合物。采用透射电子显微镜、红外光谱和振动样品磁强计对印迹聚合物进行表征,结果显示,分子印迹聚合物成功包裹在四氧化三铁表面。印迹聚合物对5种酰胺类除草剂均有特异性识别作用。以磁性分子印迹聚合物为基础,建立了酰胺类除草剂的气相色谱检测方法。方法学验证表明该方法具有良好的回收率(85.0%~99.5%)和精密度(RSD为2.8%~5.0%,n=5),线性范围为0.1~500μg·L~(-1),检出限为0.02~0.05μg·L~(-1)。该方法能够应用于农田灌溉用水等环境水样的测定。