Environmental Applications of Electromembrane Extraction: A Review.

Electromembrane extraction (EME) is a miniaturized extraction technique that has been widely used in recent years for the analysis and removal of pollutants in the environment. It is based on electrokinetic migration across a supported liquid membrane (SLM) under the influence of an external electrical field between two aqueous compartments. Based on the features of the SLM and the electrical field, EME offers quick extraction, effective sample clean-up, and good selectivity, and limits the amount of organic solvent used per sample to a few microliters. In this paper, the basic devices (membrane materials and types of organic solvents) and influencing factors of EME are first introduced, and the applications of EME in the analysis and removal of environmental inorganic ions and organic pollutants are systematically reviewed. An outlook on the future development of EME for environmental applications is also given.

Just-in-Time Learning-Integrated Partial Least-Squares Strategy for Accurately Predicting 71 Chemical Constituents in Chinese Tobacco by Near-Infrared Spectroscopy.

Near-infrared spectroscopy has been widely used to characterize the chemical composition of tobacco because it is fast, economical, and nondestructive. However, few predictive models perform ideally when applied to large spectral libraries of tobacco and its various chemical indicators. In this study, the just-in-time learning-integrated partial least-squares (JIT-PLS) modeling strategy was applied for the first time to quantitatively analyze 71 chemical components in Chinese tobacco. Approximately 18000 tobacco samples from China were analyzed to find appropriately similar measurements and propose suitable and flexible similar subsets from the calibration for each test sample. In total, 879 representative aged tobacco leaf samples and 816 cigarette samples were used as external instances to evaluate the practical predicting ability of the proposed method. The most suitable similar subsets for each test sample could be selected by limiting the Euclidean distance and number of similar subsets to 0-3.0 × 10-9 and 10-300, respectively. The majority of the JIT-PLS models performed significantly better than traditional PLS models. Specifically, using JIT-PLS instead of traditional PLS models increased the R 2 values from 0.347-0.984 to 0.763-0.996, and from 0.179-0.981 to 0.506-0.989 for the prediction of 67 and 71 components in aged tobacco leaf and cigarette samples, respectively. Good prediction ability was demonstrated for routine chemical components, polyphenolic compounds, organic acids, and other compounds, with the mean ratios of prediction to deviation (RPDmean) being 7.74, 4.39, 4.05, and 5.48, respectively). The proposed methodology could simultaneously determine 67 major components in large and complicated tobacco spectral libraries with high precision and accuracy, which will assist tobacco and cigarette quality control in collecting as well as processing stages.

Electromembrane extraction of clenbuterol from swine urine for monitoring illegal use in livestock.

The illegal use of clenbuterol seriously endangers food safety and human health. Accurate monitoring of the illegal use of clenbuterol in livestock can efficiently prevent the clenbuterol residue pork products from entering the consumer market. Thus, in this study, a simple, rapid, and sensitive method for the determination of clenbuterol in swine urine was developed using electromembrane extraction combined with liquid chromatography-tandem mass spectrometry. It should be noted that the electromembrane extraction method presented many advantages of simple operation, fast mass transfer rate, good sample clean-up capability, and less organic solvent consumption. The effect of important factors on the extraction efficiency of clenbuterol was investigated. Under the optimal conditions, good linearity was achieved for clenbuterol over the range of 1-1000 ng/ml (linear correlation [R2 ] = 0.9996). The recoveries of clenbuterol in swine urine at three spiked levels ranged from 83.7% to 110.0% with relative standard deviation values lower than 9.7% (n = 4). The limits of detection and quantification for clenbuterol were 0.07 and 0.25 ng/ml, respectively. These results suggested that the proposed method has great potential for the extraction and determination of trace analyte in a complex sample matrix for monitoring illegal use in livestock.

Electromembrane extraction of nicotine in inhaled aerosols from tobacco cigarettes, electronic cigarettes, and heated tobacco products.

Heated tobacco products and electronic cigarettes are considered as alternatives to traditional tobacco cigarettes. However, it is crucial to monitor and compare the nicotine concentration in inhaled aerosols from these tobacco products, owing to the addictive nature and adverse effects of nicotine on human health. This study aimed to provide an electromembrane extraction (EME) combined liquid chromatography method to extract and determine nicotine in different inhaled aerosols. EME showed high extraction efficiency, selectivity, and sample clean-up capability. Under the optimal parameters, the linear range for nicotine was 0.1-200 mg L-1 (r2 > 0.9998), and the limit of detection was 0.02 mg L-1. Good precision was obtained with the intra- and inter-day relative standard deviations of 2.2 % and 2.8 %, respectively. Repeatability was satisfactory (<7.7 %), and recoveries ranged from 81.0 % to 112.8 %. Finally, this method has been successfully used for the determination and comparison of nicotine in aerosols from these three tobacco products.

Determination of ractopamine residue in animal derived foods using electromembrane extraction followed by liquid chromatography tandem mass spectrometry.

A simple, sensitive and accurate analysis method based on electromembrane extraction (EME) and liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed for the extraction and determination of ractopamine residue in animal derived foods for the first time. Several parameters that affecting the extraction efficiency of EME were optimized, including the type of supported liquid membrane (SLM), chemical composition of acceptor solution, extraction voltage and extraction time. Under the optimum conditions, the developed EME-LC-MS/MS method obtained a wide linear range (1-1000 ng/g), low limit of detection (0.07-0.11 ng/g), satisfactory recoveries of 80.3-108.8%, and high precision (5.5-7.9%). The developed method showed advantages of green, fast mass transfer rate, excellent clean-up ability, high accuracy and high sensitivity, which demonstrated its great potential for monitoring the illegal use of hazardous substances in foods.

Robust, comprehensive, sensitive analysis of flavour additives with carboxyl and hydroxyl groups in cigarette smoke combining silylation and gas chromatography-tandem mass spectrometry with an improved backflushing system.

Flavour additives with carboxyl and hydroxyl groups (FACHs), the key ingredients in characteristic flavours, are frequently detected in cigarette smoke. They are attracting increasing attention in regulating the flavour additives used in tobacco to curb youth tobacco use and prevent the use of additives that are harmful. In this study, a highly robust, sensitive, and precise method based on silylation and GC-MS/MS with an improved backflushing system was developed for the simultaneous analysis of 171 FACHs in cigarette smoke. Silylation has been shown to have advantages in terms of high selectivity and sensitivity to chemicals with carboxyl and hydroxyl groups, especially when combined with GC-MS/MS. The extraction and silylation conditions were optimised. Dichloromethane was used as the extraction agent. BSTFA in combination with 1% TMCS and 0.2% TMSI was selected as silylating agent for high silylation efficiency, particularly for hindered analytes. The method has been validated. The limit of detection (LOD) ranged from 0.6 to 332.3 ng/mL. 91.1% out of the analytes in QC samples had precisions lower than 10% during one month run. The improved backflushing system with a fused silica splitter was shown to be crucial in the excellent long-term robustness of the method. The developed method was used to determine flavour additives in 270 practical cigarette smoke samples with reliable results. A total of 154 FACHs were identified with wide-range levels among different cigarette brands.

Simultaneous analysis of multiple pesticide residues in tobacco by magnetic carbon composite-based QuEChERS method and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry.

Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid-phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh-performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2-200 µg/L. The limit of detection ranged from 0.14 to 2.67 µg/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 µg/kg were in the ranges of 80.8%-113.3% and 0.6%-16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process.

Selective extraction and determination of steroidal glycoalkaloids in potato tissues by electromembrane extraction combined with LC-MS/MS.

For the first time, electromembrane extraction (EME) combined LC-MS/MS was applied to extract and determine α-solanine and α-chaconine in different potato tissues using NPOE containing 20% (v/v) DEHP as supported liquid membrane (SLM). Under the optimal conditions, the proposed EME-LC-MS/MS method was evaluated using spiked fresh potato peel sample. The linear range for α-solanine and α-chaconine was 5-1000 ng mL-1 (R2 > 0.9991), with LOD and LOQ of 1.2-1.5 ng mL-1 and 4.1-5.2 ng mL-1, respectively. Repeatability for α-solanine and α-chaconine at three concentration levels was satisfactory (<4.9%), and recoveries ranged from 73% to 106%. Finally, the EME-LC-MS/MS method has been successfully employed to determine α-solanine and α-chaconine in sprouted potato peel and tuber samples, indicating that EME exhibited high selectivity and efficient sample clean-up capability. Consequently, EME showed great potential for extraction and purification of toxic and bioactive basic compounds from complex plant tissues.

Metal-Organic Gel-Modulated Synthesis of Hierarchically Porous Molecularly Imprinted Polymers for Efficient Removal of Sildenafil from Water.

Molecularly imprinted polymers (MIPs) with high specific recognition capability are promising in environmental remediation. However, traditional MIPs usually show poor specific binding affinity toward templates in pure aqueous medium, thus greatly limiting their practical applications in wastewater treatment. Herein, we proposed a facile and versatile method to synthesize a water-compatible hierarchically porous MIP (HP-MIP), in which a metal-organic gel (MOG) was formed by in situ assembly and acted as a removable structural modulator. Remarkably, the integration of the MOG modulator and template imprinting defects significantly improved the specific template binding affinity of HP-MIP in water. The adsorption behavior of HP-MIP fitted well with the heterogeneous Freundlich isotherm, suggesting that HP-MIP possessed greater site heterogeneity to sildenafil than HP-NIP, which confirmed the efficiency of HP-MIP for the removal of sildenafil from water. This approach provides an important pathway to prepare water-compatible porous MIP for efficient removal of highly toxic organic pollutants from wastewater.

Efficient degradation of organic pollutants by low-level Co2+ catalyzed homogeneous activation of peroxymonosulfate.

Dissolved cobalt ions (Co2+) are an excellent catalyst for activating peroxymonosulfate (PMS) to generate SO4- for the degradation of organic pollutants, but fairly high level of Co2+ is generally required, which may cause secondary pollution due to its toxicity. Herein, we demonstrate a novel strategy for this catalytic oxidation treatment in which the required Co2+ addition is very small, being much less than the emission limit of 17 µmol L-1. This new strategy is based on the much enhanced catalytic effect by the addition of small organic acids (SOAs). In a typical case, all the added diclofenac (30 µmol L-1) was degraded in 20 min by using 2 µmol L-1 Co2+, 0.15 mmol L-1 PMS and 0.5 mmol L-1 acetate with a degradation rate constant of 0.482 min-1, which was about 10 times higher than that (0.048 min-1) of equivalent Co2+-PMS system without acetate. The formation of SO4- was greatly enhanced by introducing acetate, and this novel system is universal for enhanced degradation of various organic pollutants. Similarly, formate, propionate, and butyrate also exhibited enhancing effects on the catalytic ability of Co2+. The enhancement mechanism of SOAs on catalytic activation of PMS by low-level Co2+ was also proposed.

Shengfu Oil Enhances the Healing of Full-Thickness Scalded Skin Accompanying the Differential Regulation of ß-Catenin, Dlk1, and COX-2.

Shengfu oil is a traditional Chinese medicine formula containing 16 ingredients, including Scutellariae radix, Olibanum, and Rehmanniae radix. In this study, we aimed to enhance the wound healing of rabbit full-thickness scalded skin by Shengfu oil and to elucidate its regulatory effects on ß-catenin, Dlk1, and COX-2. We found that Shengfu oil exhibited significant anti-inflammatory, analgesic, and antimicrobial activities. The structure of wound tissues in Shengfu oil group was intact, including regenerated cutaneous appendages, indicating better healing capability of Shengfu oil compared to the controls. The protein expression of ß-catenin, Dlk1, and COX-2 in wound tissues were investigated by immunohistochemistry staining and were further quantitated with the use of multispectral imaging analysis. The protein expression of ß-catenin and Dlk1 in the Shengfu oil group was higher than that in the sesame oil group in early wound repair, accompanied by the lower expression of COX-2; the protein expression of ß-catenin decreased in the middle of wound healing; the protein expression of ß-catenin and Dlk1 increased at the end of wound healing. These results strongly suggest that Shengfu oil can enhance wound healing by regulating the expression of ß-catenin, Dlk1, and COX-2 due to its excellent anti-inflammatory, analgesic, and antimicrobial activities.

Electroacupuncture Treatment Alleviates Central Poststroke Pain by Inhibiting Brain Neuronal Apoptosis and Aberrant Astrocyte Activation.

Electroacupuncture (EA) is reported to effectively relieve the central poststroke pain (CPSP). However, the underlying mechanism remains unclear. The present study investigated the detailed mechanisms of action of EA treatment at different frequencies for CPSP. A CPSP model was established with a single collagenase injection to the left ventral posterolateral nucleus of the thalamus. The EA-treated groups then received EA treatment at frequency of 2, 2/15, or 15 Hz for 30 min daily for five days. The pain-related behavioral responses, neuronal apoptosis, glial activation, and the expression of pain signal transmission-related factors (ß-catenin, COX-2, and NK-1R) were assessed using behavioral tests, Nissl staining, TUNEL staining, and immunohistochemical staining, respectively. The low-frequency EA treatment significantly (1) reduced brain tissue damage and hematoma sizes and (2) inhibited neuronal apoptosis, thereby exerting abirritative effects. Meanwhile, the high-frequency EA treatment induced a greater inhibition of the aberrant astrocyte activation, accompanied by the downregulation of the expressions of COX-2, ß-catenin, and subsequently NK-1R, thereby alleviating inflammation and producing strong analgesic effects. Together, these findings suggest that CPSP is closely related to pathological changes of the neocortex and hippocampus. EA treatments at different frequencies may exert abirritative effects by inhibiting brain neuronal apoptosis and aberrant astrocyte activation in the brain.

Mouse hepatic neoplasm formation induced by trace level and low frequency exposure to diethylnitrosamine through ß-catenin signaling pathway.

It has been reported that massive levels or/and high frequency exposure of diethylnitrosamine could induce hepatic neoplasm. However, it would be more interesting to figure out the hepatotoxic effects of diethylnitrosamine exposure at trace level and low frequency, which could be more common in our daily life. We found that both the mRNA and protein expression levels of ß-catenin were aberrant in all liver tissues, accompanied by inflammation, steatosis, fibrosis and hepatic neoplasm after 10-week exposure of diethylnitrosamine (dissolved in sesame oil, 0.16 mmol per kg body weight) to mice. In addition, gradual increase in the mRNA expression of several pivotal risk factors (TNF-α, COX-2, PPAR-γ, AP-2, Smad-2, TGF-ß1, and C-myc), as well as their protein expression levels, were associated with the aberrant expression or/and nucleus localization of ß-catenin. Altogether, our results show that long-term diethylnitrosamine exposure at trace amounts and low frequency can also induce hepatotoxicity (including inflammation, steatosis and fibrosis) and consequently aberrant activation of ß-catenin which in turn plays an important role in the initiation and promotion of liver tumors.

[Efficient oxidative degradation of tetrabromobisphenol A by silver bismuth oxide].

Silver bismuth oxide(BSO) was prepared by a simple ion exchange-coprecipitation method with AgNO3 and NaBiO, .2H2O as raw materials, and then used to oxidatively degrade tetrabromobisphenol A(TBBPA). Effects of the molar ratio of Ag/Bi during BSO preparation and the BSO dosage on the degradation of TBBPA were investigated. The results showed that under the optimized conditions (i.e., the Ag/Bi molar ratio of 1:1, BSO dosage of 1 g x L(-1), 40 mg x L(-1) of TBBPA was completely degraded and the removal of total organic carbon achieved more than 80% within 7 min. The degradation intermediates of TBBPA were identified by ion chromatography, gas chromatograph-mass spectrometer and X-ray photoelectron spectroscopy. The degradation pathway of TBBPA included the debromination, the cleavage of tert-butyl group and the open epoxidation of benzene ring. Based on a quenching study of NaN3, singlet oxygen was proved to play a dominant role in the TBBPA degradation.

Determination of perfluorinated carboxylic acids in water using liquid chromatography coupled to a corona-charged aerosol detector.

Perfluorocarboxylic acids (PFCAs) are persistent pollutants being widely detected in the environment. In order to quantitatively determine PFCAs, a simple and rapid method for the simultaneous determination of five PFCAs was developed by coupling high performance liquid chromatographic (HPLC) separation and corona-charged aerosol detector (CAD). The PFCAs were separated on a Symmerry(®) C8 analytical column (150mm×3.9mm) under isocratic conditions with a mobile phase consisting of 5mM ammonium acetate (pH4.9±0.2) and methanol (30:70 (v/v)) at the flow rate 1mL min(-1). Ammonium acetate as ion pairing agent was added to the mobile phase for better separation and peak shapes. The elaborated method was validated for linearity, precision and accuracy. The detection limits ranged from 1.5 to 4.4µg L(-1) for PFCAs with C atoms of C4 to C8, which were decreased further to 75 to 220ng L(-1) after 20-fold preconcentration. The method was confirmed to have good precision with relative standard deviation of 0.9%-4.2% for intraday measurements and 0.9%-4.1% for interday measurements. The optimized method was applied to analyze practical wastewater samples with satisfactory results.