Sensitive determination of ethosuximide in human fluids by electromembrane extraction coupled with high performance liquid chromatography ultraviolet spectroscopy

Ethosuximide (ETX) is a common antiepileptic drug in the first line of absence epilepsy. In this study, for the first time, an economical and efficient electro-membrane (EME) method for determination of ETX in a complex biological matrix using HPLC-UV has been developed. Factors affecting conventional EME were evaluated. 1-Octanol was immobilized in a polypropylene membrane and a voltage of 35 V was applied between two platinum electrodes for 15 min. The pH of acceptor and donor phases for ionization of ETX was adjusted to 13 and 11, respectively. Under optimal microextraction conditions, the enrichment factor was 21.02 and the linear range of ETX was 0.25 to 8.00 μg/mL with an acceptable R² ≥ 0.9986. Inter-day and intra-day precision and accuracy of the suggested method were calculated with RSD < 9.5% and relative error <7.0%, respectively. The mean relative recovery of ETX in the human saliva and plasma samples was 81.68% and 74.47, respectively; while limit of detection and quantification concentrations were 0.08 and 0.25 μg/mL, respectively. Furthermore, to evaluate the application of the method, plasma and saliva samples of volunteers administering a single dose of ETX were analyzed successfully by EME-HPLC-UV method.     

Stereo- and Regiochemical Effect of N,N-Dialkylamide Extractants on the Speciation of Pu Complexes

The relationship between extractant stereochemistry and their extraction performance has only poorly been established. In order to address a part of this concern, we investigated the Pu(IV) liquid-liquid extraction (LLE) by using the N,N-di-(2-ethylhexyl)butyramide (DEHBA), as well as those of its position isomers. DEHBA (ββ-isomer) and N-(2-ethylhexyl)-N-(oct-3-yl)butyramide (EHOBA or αβ-isomer) were synthesized as a mixture of stereoisomer or stereoenriched (R,S)- and (S,S)-diastereoisomers, and were all assessed for Pu^IV LLE. The results showed that both the position and the stereoisomerism of the aliphatic substituents affect Pu^IV complexation and extraction. We found that Pu extraction is lowered by factor 2 to 4 when the ethyl branching group is closer to the complexing site. UV-vis spectroscopy showed that this extraction decrease was affected by steric hindrance inducing a deprivation of Pu inner sphere complex. Effect of stereoisomerism is highlighted for branching closer to the complexing site (α-position). Enantiopure DEHBA stereoisomers provided similar Pu extraction, whereas a slight decrease could be noticed for the more cluttered stereoenriched (αβ)-isomers, which was also concomitant with a smaller population of inner sphere complex. In contrast, the stereoisomers mixture led to a strong decrease of Pu extraction because of an antagonistic association in the mixed complexes.     

Miniaturized matrix solid-phase dispersion and solid-phase clear-up combined with capillary electrophoresis for efficient determination of trace bioactive components in complicated sample matrix: Take Wubi Shanyao Pill as an example

Accurate quantitative analysis of trace analytes in a complicated matrix is a challenge in modern analytical chemistry. An appropriate analytical method is considered to be one of the most common gaps during the whole process. In this study, a green and efficient strategy based on miniaturized matrix solid-phase dispersion and solid-phase extraction combined with capillary electrophoresis was first proposed for extracting, purifying and determining target analytes from complicated matrix, using Wubi Shanyao Pill as an example. In detail, 60 mg of samples were dispersed on MCM-48 to obtain high yields of analytes, then the extract was purified with a solid-phase extraction cartridge. Finally, four analytes in the purified sample solution were determined by capillary electrophoresis. The parameters affecting the extraction efficiency of matrix solid-phase dispersion, purification efficiency of solid-phase extraction and separation effect of capillary electrophoresis were investigated. Under the optimized conditions, all analytes demonstrated satisfactory linearity (R²>0.9983). What's more, the superior green potential of the developed method for the determination of complex samples was confirmed by the Analytical GREEnness Metric Approach. The established method was successfully applied in the accurate determination of target analytes in Wubi Shanyao Pill and thus provided reliable, sensitive, and efficient strategy support for its quality control.     

Sponge-nested polymer monoliths: Versatile materials for the solid-phase extraction of bisphenols

Polymer monoliths are promising materials for sample preparation due to their high porosity, pH stability, and simple preparation. The use of melamine formaldehyde foams has been reported as an effective support to prepare highly robust silica and polymer monoliths. Herein, divinylbenzene monoliths based on a 50:50 (%, w/w) crosslinker/porogen ratio have been nested within a melamine-formaldehyde sponge, resulting in monoliths with a surface area higher than 400 m²/g. The extraction performance of these monoliths was evaluated for the extraction of endocrine-disrupting bisphenols from aqueous solutions. We evaluated for the first time the versatility of sponge-nested polymer monoliths by comparing three different extraction modes (vortex mixing, magnetic stirring, and orbital shaking). Vortex mixing showed a comparable recovery of bisphenols (39%–81%) in a shorter extraction time (30 min, instead of 2 h). In addition, the robustness of the sponge-nested polymer monoliths was demonstrated for the first time by reshaping a larger monolithic cube (0.125 cm³) into four smaller pieces (4 × 0.03125 cm³) leading to a 16%–21% increase in extraction efficiency. This effect was attributed to an increase in the effective contact area with the sample, obtaining a higher analyte extraction capacity.     

固相萃取净化-离子色谱测定不同生长期新鲜烟叶中的7种无机阴离子

目的 为了研究不同生长期新鲜烟叶中无机阴离子的含量和变换规律,建立了一种固相萃取净化/离子色谱方法测定新鲜烟叶中的7种无机阴离子（F-,Cl-,Br-,NO2-,NO3-,SO42-,PO43-）。方法 样品经0.1 mol/L NaOH水溶液超声提取,萃取液经RP1.0cc固相萃取柱净化后,使用AS11-HC（4 mm×250 mm）色谱柱进行分离,以KOH为流动相,梯度洗脱。 结果 7种无机阴离子在0.10-5.0 μg/mL范围内具有较好的线性（r>0.996）,检出限在0.01-0.04 μg/mL之间,定量限在0.04-0.14 μg/mL之间,加标回收率为96.3%～102.1%,相对标准偏差（RSD%）在2.7%~4.8%之间。结论 方法前处理操作简单,7种无机阴离子分离好,检测灵敏准确,可用于不同生长时期新鲜烟叶样品中多种无机阴离子含量的检测分析。     

涡旋提取-改进BCR法测定土壤中重金属的化学形态

土壤中重金属的化学形态更能表明其迁移性和生物毒性。传统的重金属化学形态检测方法BCR法由于其提取时间长,影响检测效率。采用涡旋提取对传统BCR法进行方法优化,对土壤中Cu、Zn、Pb、Cd、Ni、Cr等6种重金属元素化学形态进行了实验分析。研究了涡旋转速、涡旋时间以及涡旋提取的方法精密度与准确度。结果表明,当涡旋转速为2500rpm,酸可交换态涡旋10min,可还原态涡旋10min,可氧化态涡旋5min时,涡旋提取效果良好。采用土壤标准物质对方法的适用性进行了验证,6种元素的检出限在0.4?32μg/kg,测定值均在标准值范围内,相对标准偏差在0.3%?5.5%之间。涡旋提取-改进BCR法分析速度快,灵敏度高,能满足同时测定土壤中多种金属元素化学形态的检测要求。     

Determination of 3-chloro-1,2-propanediol in biological samples by quick-easy-cheap-effective-rugged-and-safe extraction coupled with gas chromatography-mass spectrometry and its biodistribution in rats

3-Chloro-1,2-propanediol is a common food contaminant, but reports on its determination in biological tissues are lacking. In the present study, a method was developed to detect 3-chloro-1,2-propanediol contents in rat tissues by quick-easy-cheap-effective-rugged-and-safe extraction and gas chromatography-mass spectrometry analysis. Biological samples were extracted with ethyl acetate and purified with adsorbents. The optimized adsorbent for each sample was selected from 4–5 combinations of N-propylethylenediamine, octadecylsilane, graphitized carbon black, strong anion exchange, and florisil. Extracted 3-chloro-1,2-propanediol was derivatized with heptafluorobutyric anhydride and subjected to gas chromatography-mass spectrometry. This method had good linearity (correlation coefficients >0.99) in the range of 2–2000 ng/g for blood, kidney, liver, testis, and brain samples. The limits of detection were under 0.8 ng/g; the limits of quantification were 2 ng/g; the recovery rates were 85%–102%; and the matrix effects were 1.98%–7.67%. This method also had good precision. The dynamic changes in 3-chloro-1,2-propanediol in rats gavaged with 20 mg/kg b.w. for 24 h were detected using this method. The 3-chloro-1,2-propanediol content in each tissue sharply increased to a peak, rapidly decreased within 2 h, and stabilized at 12 h. 3-Chloro-1,2-propanediol persisted in the kidney, testis, and liver 24 h after gavage.     

Impact of solvent type,solvent-water concentration,and number of stages on the extraction of coumarin mixture from tamanu (Calophyllum inophyllum) oil and its antioxidant activity

Natural products have been receiving the spotlight from the people of developing and developed countries in recent years due to rising health care expenses and global financial crises. These natural products are the resources for bioactive compounds used in the drug development process. Tamanu seed oil is used for traditional remedies and cosmetic ingredients. The dried seed produces an oil with a yield of 50–75 %. Previous works reported that the seed oil comprised coumarins, one of the eminent groups of phenolics. Coumarins have anticancer, antimicrobial, anti-inflammatory, anticoagulant, antiviral, wound healing properties, and anti-HIV effects. Extraction is often referred to as the sample preparation method as its essential to purify bioactive compounds. In this work, coumarin mixture from tamanu oil was extracted by batchwise multi stages extraction. The effects of solvent used (methanol and ethanol), solvent–water concentration, and the number of stages were studied. The optimal conditions for the extraction of the coumarin mixture were 90 % ethanol and eight stages of extraction, which contributed to 50.73 ± 0.16 % of purity and 92.95 ± 3.76 % of recovery. Also, these conditions removed up to 66 % free fatty acids (FFA) and 100 % triglycerides (TG). It was found that the DPPH inhibition at 400 ppm shows that 90 % ethanol has the highest inhibition (57.72 ± 2.70 %) with an IC₅₀ value of 305 ppm. Moreover, various compounds like pyrrole-2 carboxylate, epicrinamidine, cholestane, and hydroxysclerodin trimethyl ether were also detected in the polar fraction of tamanu oil.     

Facile synthesis of spherical covalent organic frameworks for enrichment and quantification of aryl organophosphate esters in mouse serum and tissues

Here, an imine-linked-based spherical covalent organic framework (COF) was prepared at room temperature. The as-synthesized spherical COF served as an adsorbent in dispersive solid-phase extraction (dSPE), by its virtue of great surface area (1542.68 m²/g), regular distribution of pore size (2.95 nm), and excellent stability. Therefore, a simple and high-efficiency dispersive solid phase extraction method based on a spherical COF coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established to determine aryl organophosphate esters in biological samples. This approach displayed favorable linearity in the range of 10.0–1000.0 ng/L (r > 0.9989), a high signal enhancement factor (58.8–181.8 folds) with low limits of detection (0.3–3.3 ng/L). Moreover, it could effectively eliminate complex matrix interference to accurately extract seven aryl organophosphate esters from mouse serum and tissue samples with spiked recoveries of 82.0%–117.4%. The as-synthesized spherical COF has been successfully applied in sample preparation. The dSPE-HPLC-MS/MS method based on a spherical COF has potential application to study the pollutants' metabolism in vivo.     

Extraction and isolation of diphenylheptanes and flavonoids from Alpinia officinarum Hance using supercritical fluid extraction followed by supercritical fluid chromatography

In this paper, an off-line combination method of supercritical fluid extraction and supercritical fluid chromatography was developed for the selective extraction and isolation of diphenylheptanes and flavonoids from Alpinia officinarum Hance. The enrichment of target components was successfully achieved using supercritical fluid extraction with the following conditions (8% ethanol as co-solvent at 45°C and 30 MPa for 30 min). Taking full advantage of the complementarity of supercritical fluid chromatography stationary phases, a two-step preparative supercritical fluid chromatography strategy was constructed. The extract was firstly divided into seven fractions on a Diol column (250 × 20 mm internal diameter, 10 μm) within 8 min by gradient elution increasing from 5% to 20% modifier (methanol) at 55 ml/min and 15 MPa. Then the seven fractions were separated by using a 1-AA or a DEA column (250 × 19 mm internal diameter, 5 μm) at 50 ml/min and 13.5 MPa. This two-step strategy showed superior separation ability for structural analogs. As a result, seven compounds, including four diphenylheptanes and three flavonoids with high purity, were successfully obtained. The developed method is also helpful for the extraction and isolation of other structural analogs of traditional Chinese medicines.