Erratum to: Microchimica ActaDOI: 10.1007/s00604-017-2373-2The original version of this article unfortunately contained a mistake in the Acknowledgements section. Given in this article is the correct acknowledgement statement.

•Fe3O4/CS/GA/α-Glu coupled with CE was developed for screening enzyme inhibitors.•Fe3O4/CS/GA/α-Glu was prepared by using CS as modifier and GA as cross linker.•The dispersity of Fe3O4 nanoparticles was improved by solvothermal method.•α-Glucosidase inhibitors were screened from 18 TCMs in this study.As the close correlation between α-glucosidase inhibitors and the treatment of diabetes, in combination with capillary electrophoresis (CE), a method was developed to screen α-glucosidase inhibitors from traditional Chinese medicines (TCMs) by immobilizing α-glucosidase on magnetic nanoparticles. Such a magnetic immobilization would be beneficial for enzyme reusability, stability and separation. In this work, Fe3O4 nanoparticles were synthesized by solvothermal method. And the prepared nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), size and zeta potential analysis. With the modification of chitosan (CS) and glutaraldehyde (GA), α-glucosidase was successfully immobilized on the magnetic nanoparticles. The pH and temperature endurance, storage stability and reusability of the immobilized α-glucosidase were studied and compared with those of the free one. With the magnetic immobilized α-glucosidase, the Michaelis-Menten constant (Km) was calculated to be 0.85 mM, and the inhibition constant (Ki) and half-maximal inhibitory concentration (IC50) for acarbose were determined to be 7.37 and 13.69 μM, respectively. Finally, the developed method was applied to screen α-glucosidase inhibitors from 18 TCMs.Highly dispersed magnetic nanoparticles were synthesized by solvothermal method and α-glucosidase was immobilized on the magnetic nanoparticles with the modification of chitosan and glutaraldehyde. With α-glucosidase-immobilized magnetic nanoparticles, an efficient method was developed to screen α-glucosidase inhibitors from traditional Chinese medicines in combination with capillary electrophoresis.

•Fe3O4/RGO@(*)β-CD was prepared by modifying Fe3O4/RGO with β-CD.•Fe3O4/RGO@β-CD was applied in MSPE to study its extraction performance in real samples.•Fe3O4/RGO@β-CD showed good molecular selectivity toward naphthalene-derived phytohormones.•RSM was used to optimize experimental parameters affecting the extraction efficiency in detail.•The proposed method had merits of simplicity, high sensitivity and selectivity.A β-cyclodextrin (β-CD) functionalized magnetic reduced graphene oxide composite (Fe3O4/RGO@β-CD) has been prepared and its application as a selective adsorbent for the determination of the two naphthalene-derived phytohormones (1-naphthalene acetic acid (NAA) and 2-naphthoxyacetic acid (2-NOA)) has been investigated. Magnetic reduced graphene oxide composite (Fe3O4/RGO) was first synthesized via in situ chemical precipitation method and then β-CD was applied to further functionalize the resultant Fe3O4/RGO composite. The as-prepared Fe3O4/RGO@β-CD was characterized by Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Compared with Fe3O4/RGO, the as-prepared Fe3O4/RGO@β-CD showed better molecular selectivity and higher extraction efficiency for NAA and 2-NOA by dint of the size complementarity brought by the introduction of β-CD. Response surface methodology (RSM), a multivariate experimental design technique, was used to optimize experimental parameters affecting the extraction efficiency in detail. Under the optimal conditions, good performance data was obtained. The calibration curves were linear over the concentration ranging from 2 to 600 ng g−1 with correlation coefficients (R2) between 0.9995 and 0.9997 for all the analytes. The limits of detection (LODs) were 0.67 ng g−1 for both NAA and 2-NOA. The intra- and inter-day relative standard deviations (RSDs) were less than 6.02% and 7.34%, respectively. The recoveries ranged from 91.45% to 95.89%. Taken together, the proposed method was an efficient pretreatment and enrichment procedure and could be successfully applied for selective extraction and determination of naphthalene-derived phytormones in complex matrices.

A rapid and efficient ultra-performance convergence chromatography (UPC2) method coupled with electrospray ionization single quadrupole mass spectrometry (ESI-MS) was developed and validated for the simultaneous quantification of five diester diterpenoid alkaloid constituents (3-acetylaconitine, hypaconitine, deoxyaconitine, mesaconitine, aconitine) in Aconitum pendulum. Optimum separation was achieved on a BEH 2-EP C18 column (2.1 × 150 mm i.d., 1.7 μm particle) with a gradient elution of a mixture of A (supercritical CO2) and B (methanol containing 10 mmol L−1 ammonium acetate) and at a flow rate of 0.8 mL min−1 within 3 minutes. Quantification was performed using mass spectrometry in a positive ion ionization mode and selected ion recording (SIR) mode. The influences of column, modifier, additive, column temperature, and back pressure were investigated. The five alkaloids were identified and quantified using a comparison of retention time, ultraviolet spectrum, molecular ion peak (obtained from a selective ion recording mode) and peak areas with the reference compounds. The method was validated through linearity, limits of detection, limits of quantification, precision, stability, repeatability, and accuracy. The validated method was applied to analyze A. pendulum, which provided a reference for the quality evaluation of A. pendulum.

In this work, a facile protocol for preparing an online immobilized α-glucosidase microreactor was described, and also the enzyme kinetics and inhibition kinetics of such an immobilized enzyme were studied. In this procedure, α-glucosidase was immobilized on the inner wall of the capillary treated with 3-aminopropyltriethoxysilane (3-APTES) and the homobifunctional linker glutaraldehyde (GA). With cross-linking technology, the immobilized α-glucosidase microreactor was fabricated. As the key point for studying the enzyme kinetics and inhibition kinetics of the immobilized α-glucosidase with the developed microreactor, pressure was applied as the driving force to push the reaction mixture to the detection window, and the detection wavelength was set to 405 nm at which only the formed p-nitrophenol (pNP) could be detected. More importantly, with such a detection wavelength it is unnecessary to separate the substrate from the reaction mixture by applying the alkaline inactivating background electrolyte (BGE, borate buffer, pH ≥ 9.0) which is favorable for the separation. So the incubation buffer (phosphate buffer, pH 7.0) could be used as the running buffer making the online study of the enzyme kinetics and inhibition kinetics of immobilized α-glucosidase come true. The inhibition assay was performed by using acarbose as a model inhibitor, and under the optimized conditions, the Michaelis–Menten constant (Km), inhibition constant (Ki), and half-maximal inhibitory concentration (IC50) for the immobilized α-glucosidase were determined as 0.43 mM, 30.65 μM and 99.48 μM, respectively. This study indicates, for the first time, that the immobilized α-glucosidase microreactor could be used for studying the enzyme kinetics and inhibition kinetics online.

In this work, an electromembrane extraction (EME) technique based on carbon nanotubes reinforced hollow fiber (CNTs-HF) was developed and applied to determine two plant hormones in tomato samples. The CNTs-HF was prepared by a feasible physical method in which CNTs were dispersed in 1-hexanol and then immobilized into the wall pores of HF supported by capillary forces and sonication. Subsequently, the CNTs-HF was placed in tomato samples to extract plant hormones under electric field drive. In this mode, porous HF held the extractants and provided excellent sample clean-up ability. 1-Hexanol and CNTs held in the wall pores of HF served as a supported liquid membrane (SLM) and a sorbent, respectively, enabling the enrichment and migration of the analytes. The comparison between CNTs-HF-EME and HF-EME showed that CNTs could increase the overall partition coefficient of analyte in the membrane due to their large surface area and high adsorption capacity. In order to achieve the best extraction efficiency, optimal conditions of CNTs-HF-EME were obtained using 1-hexanol as the SLM, 105 V of applied voltage, pH 9 and 13 of the sample solution and the acceptor phase, respectively, an extraction time of 0.5 min and a stirring rate of 1200 ± 24 rpm. Under these conditions, CNTs-HF-EME was able to provide higher enrichment factors and lower limits of detection and quantification within a shorter extraction time, compared to the HF-EME. This newly developed extraction method has been shown to be a rapid, feasible, and cost-effective sample pretreatment technique for trace analysis in complex matrices.

An efficient, accurate and reliable chromatographic fingerprint based on ultra-performance liquid chromatography coupled with photodiode array detection and electrospray ionization mass spectrometry (UPLC-PDA-ESI-MS) was developed for the identification and quality control of Oxytropis falcate Bunge. The method was validated for precision, repeatability, stability, and specificity. The RSD values of retention times and peak areas of the common peaks were 0–0.7% and 1.0–3.6% for within-day precision, while 0–0.5% and 1.5–6.1% for between-day precision. For repeatability, the values were lower than 0.5% and 2.6%, respectively, and for stability (24 h), the values were lower than 0.9% and 3.3%, respectively. Twenty-one batches of O. falcate obtained from different regions were analyzed by employing the developed method. Several multivariate statistical analysis including similarity analysis (SA), hierarchical clustering analysis (HCA) and principal component analysis (PCA) were applied to cluster and evaluate the O. falcate samples according to their collection sites. The results showed that the quality of O. falcate did not merely depend on the geographic origin. Thirty common peaks were found in the chromatographic fingerprints of O. falcate and eleven of them were identified by comparing the retention time, the ultraviolet spectrum and the molecular ion peaks (obtained from selective ion recording mode) with the reference compounds. This method with high precision, reliable stability and good repeatability can provide a reference for the quality evaluation of O. falcate.

•G-MNPs consist of zero-valent iron, iron oxide–oxyhydroxide and graphene.•G-MNPs were prepared through a simple one-step synthesis method.•G-MNPs were applied to MSPE for the determination of carbamates in tomatoes.•G-MNPs were not only employed as magnetic carrier, but also as adsorbents.•This novel method was proved to be simple, effective, sensitive and green.Graphene-based magnetic nanoparticles, comprising zero-valent iron, iron oxide–oxyhydroxide and graphene, were prepared through a simple one-step synthesis method, and subsequently applied to magnetic solid-phase extraction for the determination of trace carbamate pesticides in tomatoes coupled with high performance liquid chromatography. The properties of the nanocomposites were confirmed by using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometer. The components within the nanocomposites endowed the material with high extraction performance and manipulative convenience. Compared with reduced graphene oxide, the as-prepared G-MNPs showed the better extraction efficiencies for the carbamate pesticides thanks to the contribution of the iron-containing magnetic nanoparticles to the adsorption capacity of the nanocomposites. Various experimental parameters affecting the extraction efficiency had been investigated in detail. Under the optimal conditions, the method provided high enrichment factors ranging from 364 to 434, good linearities ranging from 5 to 200 ng g−1 for metolcarb, baygon and methiocarb and 10 to 200 ng g−1 for carbofuran and isoprocarb, low limits of detection ranging from 0.58 to 2.06 ng g−1, and satisfactory spiked recoveries (between 90.34% and 101.98% with the relative standard deviation values from 1.21% to 5.93%). It was confirmed that this novel method was an efficient pretreatment and enrichment procedure and could be successfully applied for extraction and determination of trace carbamate pesticides in complex matrices.Graphene-based magnetic nanoparticles were prepared through a simple one-step synthesis method, and subsequently applied to magnetic solid-phase extraction for the determination of trace carbamate pesticides in tomatoes coupled with high performance liquid chromatography.

•We review four ways of modifying hollow fibers of polypropylene.•We review applications of hollow-fiber-based solid-phase microextraction (HF-SPME).•Modified HF-SPME has advantages over conventional SPME.Polypropylene hollow fibers (PPHFs) are usually applied for HF liquid-phase microextraction and have proved effective in various applications. By modifying PPHFs with sorbents, they can be used for solid-phase microextraction, and the method is novel, efficient and economical. This article mainly reviews the modification of PPHFs using carbon nanotubes, graphene, ceramic metal oxides and self-synthesized polymers.

•Ionic liquid based electromembrane extraction (IL-EME) was first established.•The extraction performance of IL-EME compared with ENB based EME was carried.•The simultaneous extraction for multiple samples was achieved by parallel extraction setup.•The method was applied to the determination of strychnine and brucine in human urine samples.An ionic liquid-based electromembrane extraction (IL-EME) method was presented, and its performance was compared with 2-ethylnitrobenzene (ENB) based EME for the determination of strychnine and brucine in human urine. For the two methods, the fundamental extraction parameters such as supported liquid membrane, voltage, extraction time, pH values of sample solution and acceptor solution, temperature and salting-out effect were separately optimized. IL-EME provided 96- and 122-fold enrichment factors for strychnine and brucine, respectively, which were better than those obtained in EME (83- and 86-fold, respectively). The calibration curves were linear over the ranges of 20–720 μg L−1 for strychnine and 20–640 μg L−1 for brucine with the correlation coefficients higher than 0.9950. The repeatability of EME and IL-EME were evaluated by five parallel experiments giving the relative standard deviations of 5.12–6.98%. As the results indicated, compared with ENB based EME, the proposed IL-EME is more reliable and could provide better extraction performance for the determination of strychnine and brucine in human urine.

•CNTs-β-CD nanocomposite was prepared by modifying the surface of CNTs with β-CD.•Reinforced fibers were obtained by immobilizing the nanocomposite in their wall pores.•The fiber was applied in SPME of plant hormones to study its extraction performance in real samples.•This new extraction fiber had merits of simplicity, high sensitivity, and selectivity.A new, efficient, and environmental friendly solid-phase microextraction (SPME) medium based on β-cyclodextrin (β-CD)-modified carbon nanotubes (CNTs) and a hollow fiber (HF) was prepared. Functionalized β-CD was covalently linked to the surface of the carboxylic CNTs and then the obtained nanocomposite was immobilized into the wall pores of HFs under ultrasonic-assisted effect. The scanning electron microscope was used to inspect surface characteristics of fibers, demonstrating the presence of nanocomposites in their wall pores. The reinforced HF was employed in SPME, and its extraction performance was evaluated by analyzing 1-naphthaleneacetic acid (NAA) and 2-naphthoxyacetic acid (2-NOA) in vegetables. Without any tedious clean-up procedure, analytes were extracted from the sample to the adsorbent and organic solvent immobilized in HFs and then desorbed in acetonitrile prior to chromatographic analysis. Under the optimized extraction conditions, the method provided 275- and 283-fold enrichment factors of NAA and 2-NOA, low limits of detection and quantification (at an ng g−1 level), satisfactory spiked recoveries, good inter-fiber repeatability, and batch-to-batch reproducibility. The selectivity of the developed fiber was investigated to three structurally similar compounds and two reference compounds with recognition coefficients up to 3.18. The obtained results indicate that the newly developed fiber is a feasible, selective, green, and cost-effective microextraction medium and could be successfully applied for extraction and determination of naphthalene-derived plant hormones in complex matrices.

Multiple components in traditional Chinese medicines (TCMs) have a synergistic action on the therapeutic effects of TCMs and their contents may vary substantially with environmental changes. In this study, an ultra-performance liquid chromatographic (UPLC) fingerprint was established to choose the optimum environmental conditions for the cultivation of Angelica sinensis (A. sinensis). Optimum separation was achieved on a C18 column (50 × 2.1 mm i.d., 1.7 μm particles) with a 25 min gradient. The method was applied to establish the chromatographic fingerprint of A. sinensis by analyzing 109 samples cultivated under controlled environmental conditions. A representative standard fingerprint chromatogram was obtained using professional software, in which 30 common peaks were marked. The common peaks for all samples were subjected to principal component analysis with partial least squares discriminant analysis to screen out the peaks related to specific environmental factors. Peaks with areas that showed significant differences under different environmental conditions were screened out and used to obtain the optimum environmental conditions. Our method of integrating the advantages of chromatographic fingerprinting and multivariate statistical analysis can reveal the integral characteristics of herbal medicines. Consequently, it is a comprehensive, scientific method that provides a technical safeguard for the cultivation of herbal medicines.

•Multiple functional ILs [BSO3HMIm][OTf] and [EMIm][BF4] were first used in DLLME.•The acidic compounds were directly extracted from water without pH adjustment.•The whole extraction procedure was green without any consumption of organic solvent.A new mode of ionic liquid based dispersive liquid–liquid microextraction (IL-DLLME) is developed. In this work, [C6MIm][PF6] was chosen as the extraction solvent, and two kinds of hydrophilic ionic liquids, [EMIm][BF4] and [BSO3HMIm][OTf], functioned as the dispersive solvent. So in the whole extraction procedure, no organic solvent was used. With the aid of SO3H group, the acidic compound was extracted from the sample solution without pH adjustment. Two phenolic compounds, namely, 2-naphthol and 4-nitrophenol were chosen as the target analytes. Important parameters affecting the extraction efficiency, such as the type of hydrophilic ionic liquids, the volume ratio of [EMIm][BF4] to [BSO3HMIm][OTf], type and volume of extraction solvent, pH value of sample solution, sonication time, extraction time and centrifugation time were investigated and optimized. Under the optimized extraction conditions, the method exhibited good sensitivity with the limits of detection (LODs) at 5.5 μg L−1and 10.0 μg L−1 for 4-nitrophenol and 2-naphthol, respectively. Good linearity over the concentration ranges of 24–384 μg L−1 for 4-nitrophenol and 28–336 μg L−1 for 2-naphthol was obtained with correlation coefficients of 0.9998 and 0.9961, respectively. The proposed method can directly extract acidic compound from environmental sample or even more complex sample matrix without any pH adjustment procedure.Multiple functional ionic liquids [BSO3HMIm][OTf] and [EMIm][BF4] serving as dispersive solvent were first used in DLLME. With the aid of acidic ionic liquids, the phenolic compounds were directly extracted from environmental water samples without pH adjustment.

An effective and sensitive method to determinate five carbamate pesticides in apples was developed by using carbon nanotubes-reinforced hollow fibre solid-phase microextraction (CNTs-HF-SPME) combined with high performance liquid chromatography-photodiode array detection (HPLC-DAD). The CNTs were dispersed in water via adding surfactant, and then were held in the pores of HF supported by capillary forces and sonification. The SPME device, which was wetted with 1-octanol, was placed in a stirred apple samples to extract target analytes. After extraction, analytes were desorbed and analyzed using HPLC-DAD. Under the optimized extraction conditions, the enrichment factors were achieved in the range from 49 to 308 with good inter-fibre repeatability and batch-to-batch reproducibility, while good linearity ranges and recoveries were obtained. The limits of detection ranged from 0.09 to 6.00 ng/g. Therefore, the results demonstrated that this novel method was an efficient pretreatment and enrichment procedure for the determination of trace carbamate pesticides in apples.Highlights► CNTs were dispersed in water by surfactant and held in the pores of hollow fibre. ► The developed CNTs-HF was applied in SPME to extract carbamate pesticides in apples. ► This novel method was proved to be effective, simple and low cost.

Temperature controlled ionic liquid dispersive liquid–liquid microextraction (TC IL-DLLME) combined with high performance liquid chromatography (HPLC) has been developed for the simultaneous determination of di(2-ethylhexyl)phthalate (DEHP) and its metabolite mono(2-ethylhexyl)phthalate (MEHP) in human urine samples. Dibutyl phthalate (DBP) was employed as an internal standard. Some important parameters, such as the type of extraction solvent and dispersive solvent, the volume ratio of extraction to dispersive solvent, volume of a mixture of extraction solvent and dispersive solvent, temperature, sample pH, salt effect, cooling time and centrifugation time, were investigated and optimized to achieve a high extraction efficiency. Under the optimized extraction conditions, the method showed 115- and 164-fold enrichment factors for MEHP and DEHP in urine samples, respectively. It also exhibited high sensitivity with the limits of detection at 0.96 μg L−1 and 3.2 μg L−1 for MEHP and DEHP, respectively. The calibration curves were linear in the concentration range of 20–1920 μg L−1 for MEHP and 60–1920 μg L−1 for DEHP, with the correlation coefficients higher than 0.9990. The proposed method can be expected to monitor the human exposure to the plasticizer agent by determining its metabolites in human urine samples.

•CNTs were held into the wall pores of hollow fiber via surfactant-assisted effect.•The developed CNTs–HF was applied in SPME to extract strychnine and brucine in urine.•This novel method was proved to be effective, sensitive, simple, green and of low cost.A mixed matrix membrane (MMM), based on carbon nanotubes (CNTs) and hollow fiber (HF), was prepared and combined with solid phase microextraction (SPME) mode to determine strychnine and brucine in urine. This MMM was prepared by dispersing CNTs in water via surfactant assistance, and then immobilizing CNTs into the pores of HF by capillary forces and sonification. The prepared carbon nanotubes reinforced hollow fiber (CNTs–HF) was subsequently wetted by a few microliters of organic solvent (1-octanol), and then applied to extract the target analytes in direct immersion sampling mode. After extraction, analytes were desorbed via ultrasonic-assisted effect, and then detected via high-performance liquid chromatography (HPLC). To achieve the highest extraction efficiency, main extraction parameters such as the type and amount of surfactant, the diameter and doping level of CNTs, extraction time, desorption condition, pH value, stirring rate and volume of the donor phase were optimized. Under the optimum extraction conditions, the method showed good linearity ranges with correlation coefficients higher than 0.9990, good repeatability and batch-to-batch reproducibility with relative standard deviations (RSDs) less than 6% and 5% for strychnine and brucine, respectively, and low limits of detection (0.7 and 0.9 µg L−1 for strychnine and brucine, respectively). The recoveries were in the range of 83.81–116.14% at three spiked levels. The developed method was successfully applied to real urine sample with mean relative recoveries of 94.28% and 91.30% for strychnine and brucine, respectively. The developed method shows comparable results against reference methods and is a simple, green, and cost-effective microextraction technique.

In the present study, pressure mediated microanalysis (PMMA), a fast, convenient and efficient capillary electrophoresis (CE) method was developed for studying enzyme kinetics of tyrosinase and inhibition kinetics of kojic acid, a model inhibitor of tyrosinase. The enzymatic reaction conditions and CE conditions were optimized in order to obtain high enzyme activity and short analysis time. By PMMA, only the product could be detected at 475 nm, and no voltage was applied to separate the product from the reaction mixture thus greatly simplifying the optimization procedure. The spectrophotometric assay and electrophoretically mediated microanalysis (EMMA) were also performed to validate the developed method. With the present method, the Michaelis-Menten constant (Km) was calculated to be 1.347 mM for tyrosinase. The inhibition constant of kojic acid to free tyrosinase (KI) and kojic acid to tyrosinase/L-DOPA complex (KIS) were calculated to be 36.64 and 74.35 μM, respectively, and the half-maximal inhibitory concentration (IC50) was determined to be 46.64 μM for kojic acid. The developed method is fast and convenient for studying enzyme kinetics, inhibition kinetics and further screening enzyme inhibitors.

•A novel Fe3O4@PEI-RGO was synthesized and applied for the analysis of polar acidic herbicides.•PEI affected the surface property of RGO and changed the polarity of RGO.•Fe3O4@PEI-RGO showed good extraction efficiency towards polar acidic herbicides.•RSM was used to optimize parameters affecting the extraction efficiency.•The absorption mechanism was discussed in detail.A novel magnetic polyethyleneimine modified reduced graphene oxide (Fe3O4@PEI-RGO) had been fabricated based on a self-assemble approach between positive charged magnetic polyethyleneimine (Fe3O4@PEI) and negative charged GO sheets via electrostatic interaction followed by chemical reduction of GO to RGO. The as-prepared Fe3O4@PEI-RGO was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), thermal gravimetric analyzer (TGA), vibrating sample magnetometer (VSM) and zeta potential analysis, and then was successfully applied to determine four phenoxy acid herbicides and dicamba in rice coupled with high performance liquid chromatography (HPLC). As a surface modifier of RGO, PEI not only effectually affected the surface property of RGO (e.g. zeta potential), but also changed the polarity of RGO and offered anion exchange groups to polar acidic herbicides, which would directly influence the type of adsorbed analytes. Compared with Fe3O4@PEI, Fe3O4/RGO and Fe3O4@PEI-GO, the as-prepared Fe3O4@PEI-RGO, integrating the superiority of PEI and RGO, showed higher extraction efficiency for polar acidic herbicides. Besides, the adsorption mechanism was investigated as well. It turned out that electrostatic interaction and π-π interaction were considered to be two major driving force for the adsorption process. Response surface methodology (RSM), a multivariate experimental design technique, was used to optimize experimental parameters affecting the extraction efficiency in detail. Under the optimal conditions, a satisfactory performance was obtained. The calibration curves were linear over the concentration ranging from 2 to 300 ng g−1 with correlation coefficients (r) between 0.9985 and 0.9994. The limits of detection (LODs) were in the range of 0.67–2 ng g−1. The recoveries ranged from 87.41% to 102.52% with relative standard deviations (RSDs) less than 8.94%. Taken together, the proposed method was an efficient pretreatment and enrichment procedure and could be successfully applied for selective extraction and determination of polar acidic herbicides in complex matrices.

Temperature controlled ionic liquid dispersive liquid–liquid microextraction (TC IL-DLLME) combined with high performance liquid chromatography (HPLC) has been developed for the simultaneous determination of di(2-ethylhexyl)phthalate (DEHP) and its metabolite mono(2-ethylhexyl)phthalate (MEHP) in human urine samples. Dibutyl phthalate (DBP) was employed as an internal standard. Some important parameters, such as the type of extraction solvent and dispersive solvent, the volume ratio of extraction to dispersive solvent, volume of a mixture of extraction solvent and dispersive solvent, temperature, sample pH, salt effect, cooling time and centrifugation time, were investigated and optimized to achieve a high extraction efficiency. Under the optimized extraction conditions, the method showed 115- and 164-fold enrichment factors for MEHP and DEHP in urine samples, respectively. It also exhibited high sensitivity with the limits of detection at 0.96 μg L−1 and 3.2 μg L−1 for MEHP and DEHP, respectively. The calibration curves were linear in the concentration range of 20–1920 μg L−1 for MEHP and 60–1920 μg L−1 for DEHP, with the correlation coefficients higher than 0.9990. The proposed method can be expected to monitor the human exposure to the plasticizer agent by determining its metabolites in human urine samples.

Multiple components in traditional Chinese medicines (TCMs) have a synergistic action on the therapeutic effects of TCMs and their contents may vary substantially with environmental changes. In this study, an ultra-performance liquid chromatographic (UPLC) fingerprint was established to choose the optimum environmental conditions for the cultivation of Angelica sinensis (A. sinensis). Optimum separation was achieved on a C18 column (50 × 2.1 mm i.d., 1.7 μm particles) with a 25 min gradient. The method was applied to establish the chromatographic fingerprint of A. sinensis by analyzing 109 samples cultivated under controlled environmental conditions. A representative standard fingerprint chromatogram was obtained using professional software, in which 30 common peaks were marked. The common peaks for all samples were subjected to principal component analysis with partial least squares discriminant analysis to screen out the peaks related to specific environmental factors. Peaks with areas that showed significant differences under different environmental conditions were screened out and used to obtain the optimum environmental conditions. Our method of integrating the advantages of chromatographic fingerprinting and multivariate statistical analysis can reveal the integral characteristics of herbal medicines. Consequently, it is a comprehensive, scientific method that provides a technical safeguard for the cultivation of herbal medicines.

An efficient, accurate and reliable chromatographic fingerprint based on ultra-performance liquid chromatography coupled with photodiode array detection and electrospray ionization mass spectrometry (UPLC-PDA-ESI-MS) was developed for the identification and quality control of Oxytropis falcate Bunge. The method was validated for precision, repeatability, stability, and specificity. The RSD values of retention times and peak areas of the common peaks were 0–0.7% and 1.0–3.6% for within-day precision, while 0–0.5% and 1.5–6.1% for between-day precision. For repeatability, the values were lower than 0.5% and 2.6%, respectively, and for stability (24 h), the values were lower than 0.9% and 3.3%, respectively. Twenty-one batches of O. falcate obtained from different regions were analyzed by employing the developed method. Several multivariate statistical analysis including similarity analysis (SA), hierarchical clustering analysis (HCA) and principal component analysis (PCA) were applied to cluster and evaluate the O. falcate samples according to their collection sites. The results showed that the quality of O. falcate did not merely depend on the geographic origin. Thirty common peaks were found in the chromatographic fingerprints of O. falcate and eleven of them were identified by comparing the retention time, the ultraviolet spectrum and the molecular ion peaks (obtained from selective ion recording mode) with the reference compounds. This method with high precision, reliable stability and good repeatability can provide a reference for the quality evaluation of O. falcate.