Online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry for the determination of five tannins in traditional Chinese medicine injections

A rapid analytical method based on online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry has been established and applied to the determination of tannin compounds that may cause adverse effects in traditional Chinese medicine injections. Different solid‐phase extraction sorbents have been compared and the elution buffer was optimized. The performance of the method was verified by evaluation of recovery (≥40%), repeatability (RSD ≤ 6%), linearity (r² ≥ 0.993), and limit of quantification (≤0.35 μg/mL). Five tannin compounds, gallic acid, cianidanol, gallocatechin gallate, ellagic acid, and penta‐O‐galloylglucose, were identified with concentrations ranging from 3.1–37.4 μg/mL in the analyzed traditional Chinese medicine injections.     

Therapeutic deferoxamine and deferiprone monitoring in β‐thalassemia patients’ plasma by field‐amplified sample injection and sweeping in capillary electrophoresis

One CE method was established for detecting deferoxamine (DFO) and deferiprone (DFR) in plasma. For β‐thalassemia patients, DFO and DFR are major medicines to treat the iron overload caused by blood transfusion. Field‐amplified sample injection combined with sweeping was used for sensitivity enhancement in CE. This method was performed on an uncoated fused‐silica capillary. After liquid–liquid extraction, the plasma samples were electrokinetically injected into capillary at +10 kV for 180 s. The phosphate buffer (100 mM) containing 50 mM triethanolamine was used as the BGE (pH 6.6). Separation buffer was phosphate buffer (100 mM, pH 3.0) containing 150 mM SDS. This method showed good linearity (r ≥ 0.9960). Precision and accuracy were evaluated by the results of RSD and relative error of intrabatch and interbatch analyses, and all of the absolute values were less than 6.12%. The LODs (S/N = 3) were 200 ng/mL for DFO, and 25 ng/mL for DFR. The LOQ (S/N = 10) of DFO and DFR were 600 and 75 ng/mL, respectively. This method was applied for clinical applications of five β‐thalassemia patients.     

Preparation of metal‐organic framework UiO‐66‐incorporated polymer monolith for the extraction of trace levels of fungicides in environmental water and soil samples

A zirconium terephthalate metal‐organic framework‐incorporated poly(N‐vinylcarbazole‐co‐divinylbenzene) monolith was fabricated in a capillary by a thermal polymerization method. The optimized monolith had a homogeneous structure, good permeability, and stability. The monolith could be used for the effective enrichment of fungicides through π‐π interactions, electrostatic forces, and hydrogen bonds. The potential factors that affect the extraction efficiency, including ionic strength, solution pH, sample volume, and eluent volume, were investigated in detail. The monolith‐based in‐tube solid‐phase microextraction coupled with ultra‐high‐performance liquid chromatography and high‐resolution Orbitrap mass spectrometry was performed for the analysis of five fungicides (pyrimethanil, tebuconazole, hexaconazole, diniconazole, and flutriafol) in environmental samples. Under the optimized conditions, the linear ranges were 0.005–5 ng/mL for pyrimethanil, 0.01–5 ng/mL for flutriafol, and 0.05–5 ng/mL for other fungicides, respectively, with coefficients of determination ≥0.9911. The limits of detection were 1.34–14.8 ng/L. The columns showed good repeatability (relative standard deviations ≤9.3%, n = 5) and desirable column‐to‐column reproducibility (relative standard deviations 5.3–9.4%, n = 5). The proposed method was successfully applied for the simultaneous detection of five fungicides in water and soil samples, with recoveries of 90.4–97.5 and 84.0–95.3%, respectively.     

Analysis of phenolic acids and flavonoids in leaves of Lycium barbarum from different habitats by ultra‐high‐performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry

The leaves of Lycium barbarum (LLB) have been utilized as crude drugs and functional tea for human health in China and Southeast Asia for thousands of years. To control its quality, a rapid and sensitive ultra‐high‐performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry method was established and validated for the first time for simultaneous determination of 10 phenolic acids and flavonoids (including neochlorogenic acid , protocatechuic aldehyde, p‐hydroxybenzoic acid, chlorogenic acid, cryptochlorogenic acid, caffeic acid, p‐coumaric acid, ferulic acid, rutin and kaempferol‐3‐O‐rutinoside) in LLB. The separation was performed on an Acquity UPLC C₁₈ chromatographic column (100 × 2.1 mm internal diameter, 1.7 μm particle size) with 0.1% formic acid in water (A)–acetonitrile (B) as the mobile phase under gradient elution. Multiple reaction monitoring mode was adopted to simultaneously monitor the target components. The developed method was fully validated in terms of linearity (r² ≥ 0.9860), precision (RSD ≤ 6.58%), repeatability (RSD ≤ 6.60%), stability (RSD ≤ 6.17%), recovery (95.56–108.06%, RSD ≤ 4.64%) and limit of detection (0.021–0.664 ng/mL) and limit of quantitation (0.069–2.210 ng/mL), and then successfully applied to evaluate the quality of 64 batches of LLB collected from 41 producing areas in four different provinces of China. The results showed that the LLB, especially collected from Inner Mongolia regions, were rich in the phenolic acids and flavonoids. Rutin, kaempferol‐3‐O‐rutinoside and chlorogenic acid are the predominant compounds contained in LLB. The above findings will provide helpful information for the effective utilization of LLB.     

Simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone,and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma by liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study

A new liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma using chlorpropamide as an internal standard. Plasma samples (50 μL) were prepared using a simple deproteinization procedure with 150 μL of acetonitrile containing 100 ng/mL of chlorpropamide. Chromatographic separation was carried out on an Acclaim RSLC120 C₁₈ column (2.1 × 100 mm, 2.2 μm) using a gradient elution consisting of 7.5 mM ammonium acetate and acetonitrile containing 0.1% formic acid (0.4 mL/min flow rate, 7.0 min total run time). The detection and quantitation of all analytes were performed in selected reaction monitoring mode under both positive and negative electrospray ionization. This assay was linear over concentration ranges of 50–5000 ng/mL (trifolirhizin), 25–2500 ng/mL ((–)‐maackiain), 5–250 ng/mL ((–)‐sophoranone), and 1–250 ng/mL 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran) with a lower limit of quantification of 50, 25, 5, and 1 ng/mL for trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran, respectively. All the validation data, including the specificity, precision, accuracy, recovery, and stability conformed to the acceptance requirements. The results indicated that the developed method is sufficiently reliable for the pharmacokinetic study of the analytes following oral administration of Sophora tonkinensis extract in rats.     

Separation and pre‐concentration of glucocorticoids in water samples by ionic liquid supported vortex‐assisted synergic microextraction and HPLC determination

We have developed a synergic microextraction procedure based on ionic liquid for the pre‐concentration and determination of glucocorticoids in water samples. Using nonionic surfactant Triton X‐100 (TX‐100) as synergic reagent, 1‐butyl‐3‐methylimidazolium hexa‐fluorophosphate accomplished extraction rapidly without heating in water bath. One key property of ionic liquids that highlights their potential is their wide liquid temperature range. The improved extraction was named as ionic liquid supported vortex‐assisted synergic microextraction. Compared with the traditional liquid–liquid extraction and cloud point extraction, ionic liquid supported vortex‐assisted synergic microextraction was accomplished in 8 min with considerably high recovery. The proposed method greatly improved the sensitivity of HPLC for the determination of glucocorticoids. The results obtained indicated a good linearity with the correlation coefficient of 0.997 over the range of 0.6–300 ng/mL and high sensitivity with LODs of 4.11, 9.19, and 7.50 ng/mL for hydrocortisone butyrate, beclomethasone dipropionate, and nandrolone phenylpropionate, respectively. The RSD of the method was 1.57–1.81% (n = 6) with enrichment factor of 99.85, and good recovery (≥97.24%). The method was successfully applied to the determination of glucocorticoids in mineral water, water of Dianchi lake, and tap water samples.     

Separation of cucurbitane triterpenoids from bitter melon drinks and determination of partition coefficients using vortex‐assisted dispersive liquid‐phase microextraction followed by UHPLC analysis

A rapid, effective method applying vortex‐assisted liquid–liquid microextraction before ultra‐high performance liquid chromatography with mass spectrometry and evaporative light scattering detection was developed for the analysis of four cucurbitane triterpenoids (momordicoside L, momordicoside K, momordicoside F₂, and 3β,7β,25‐trihydroxy cucurbita‐5,23(E )‐dien‐19‐al) in bitter melon juices. Variables affecting the extraction efficiency including different extraction solvents, volume of extraction solvent, salt amount, acid condition, vortex speed and time were optimized thoroughly. Under the optimum conditions, precision was determined by the intra‐ and inter‐day tests in a range of 1.1–5.7% and 2.9–4.0% (RSD), respectively, with recoveries between 95.7 and 106.1%. The calibration curves showed good linearity with square correlation coefficient of 0.9936–0.9991 (evaporative light scattering detection) and 0.9858–0.9989 (MS). The detection limits ranged from 0.8–1.9 ng/mL (MS) to 3–10 ng/mL (evaporative light scattering detection) for these compounds. Enrichment factors of four target compounds were between 27 and 63 times. The proposed method was also used to determine the apparent solvent/water partition coefficients of analytes within the range of 53–120. The developed method can effectively enrich and quantify cucurbitane triterpenoids from bitter melon drinks.     

Up‐and‐down shaker‐assisted ionic liquid‐based dispersive liquid—liquid microextraction of benzophenone‐type ultraviolet filters

Sun protection is an important part of our lives. UV filters are widely used to absorb solar radiation in sunscreens. However, excess UV filters constitute persistent groups of organic micropollutants present in the environment. An environmentally friendly ionic‐liquid‐based up‐and‐down shaker‐assisted dispersive liquid?liquid microextraction device combined with ultra‐performance liquid chromatography coupled with photodiode‐array detection has been developed to preconcentrate three UV filters (benzophenone, 2‐hydroxy‐4‐methoxybenzophenone, 2,2′‐dihydroxy‐4‐methoxybenzophenone) from field water samples. In this method, the optimal conditions for the proposed extraction method were: 40 μL [C₈MIM][PF₆] as extraction solvent and 200 μL methanol as disperser solvent were used to extract the UV filters. After up‐and‐down shaking for 3 min, the aqueous solution was centrifuged at 5000 rpm speed, then using microtube to collect the settled extraction solvent and using ultra‐performance liquid chromatography for further analysis. Quantification results indicated that the linear range was 2–1000 ng/mL. The LOD of this method was in the range 0.2–1.3 ng/mL with r² ≥ 0.9993. The relative recovery in studies of different types of field water samples was in the range 92–120%, and the RSD was 2.3–7.1%. The proposed method was also applied to the analysis of field samples.     

Comparison of three‐phase hollow fiber liquid‐phase microextraction based on reverse micelle with conventional two‐phase hollow fiber liquid‐phase microextraction and their applications for analysis of cinnamic acids in traditional Chinese medicines

A novel three‐phase hollow fiber liquid‐phase microextraction was developed based on reverse micelle as extraction solvent and acceptor phase, and compared with conventional two‐phase hollow fiber liquid‐phase microextraction. Both procedures were used in the extraction and concentration of four cinnamic acids (caffeic acid, p‐hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicines prior to high‐performance liquid chromatography analysis. Parameters affecting the two procedures were investigated and optimized to obtain the optimum enrichment factors. The mechanism of the developed procedure was explored and elucidated by comparison with conventional two‐phase hollow fiber liquid‐phase microextraction. Under the optimized conditions, the analytes’ enrichment factors were between 50 and 118 for the proposed procedure, and 31–96 for conventional two‐phase mode. Satisfactory linear ranges (r² ≥ 0.99), detection limits (0.1–0.6 ng/mL), precisions (<9.2%), and accuracies (recoveries: 80–123.1%) were observed for the two procedures. The results showed that the enrichment capacity of the proposed procedure for the cinnamic acids is better than that of conventional two‐phase procedure, and both are eco‐friendly, simple, and effective for the enrichment and detection of cinnamic acids in traditional Chinese medicines.     

Solvent‐vapor‐assisted liquid–liquid microextraction: A novel method for the determination of phthalate esters in aqueous samples using GC–MS

A novel liquid–liquid microextraction method, namely, solvent‐vapor‐assisted liquid–liquid microextraction for the determination of dimethyl phthalate, diethyl phthalate, dibutyl phthalate and bis(2‐ethylhexyl) phthalate in the aqueous samples using gas chromatography with mass spectrometry was developed. In the proposed method, extracting solvent was heated, and solvent vapor as the extracting phase was injected into the sample solution. As a result of the low temperature of the sample solution and higher density of the extracting phase than the aqueous medium, solvent vapor was condensed and an organic‐phase drop formed in the bottom of sample tube. Because of the gas status of the extracting solvent, the surface area between the extracting solvent and the aqueous sample was remarkably high. Under the optimized conditions, tetrachloride carbon was used as an extracting solvent. The method shows high coefficient of determination (R ²) values in the range of 0.5–200 and 1.0–200 ng/mL for the target analytes. Enrichment factors and limits of detection for the studied phthalates are obtained in the ranges of 2800–3000 and 0.15–0.3 ng/mL, respectively. Recoveries and relative standard deviations were in the range of 80.0–100.0 and 2.2–7.8%, respectively. The proposed method successfully used for analysis of several aqueous samples.     

Vortex‐assisted liquid–liquid microextraction of strontium from water samples using 4′,4″(5″)‐di‐(tert‐butylcyclohexano)‐18‐crown‐6 and tetraphenylborate

A vortex‐assisted liquid–liquid microextraction method was developed for the chromatographic determination of strontium in aqueous samples. In the method, strontium was complexed with 4′,4″(5″)‐di‐(tert‐butylcyclohexano)‐18‐crown‐6 in the presence of tetraphenylborate as the counter anion, which increased the hydrophobicity of the ion‐association complex, resulting in its improved extraction into 1‐octanol. Strontium from the organic phase was stripped with nitric acid back to aqueous solution and determined by ion chromatography. The optimum microextraction conditions were as follows: 2.0 mL aqueous samples with 3 mM tetraphenylborate; 150 μL of 1‐octanol as the extractant phase with 10 mM DtBuCH18C6; vortex extraction time for 10 s; centrifugation at 6000 rpm for 4 min; stripping by 0.1 M nitric acid. Under the optimum conditions, the detection limit for strontium was 0.005 mg/L. The calibration curves showed good linearity over the range between 0.01 and 2.5 mg/L. Intra‐ and interday precisions of the present method were satisfactory with relative standard deviations of 1.7 and 2.1%, respectively.     

Validation of a liquid chromatography‐triple quadrupole mass spectrometric method for the determination of 5‐nitro‐5′‐hydroxy‐indirubin‐3′‐oxime (AGM‐130) in human plasma and its application to microdose clinical trial

A liquid chromatography–triple quadrupole mass spectrometric (LC‐MS/MS) method was developed and validated for the determination of 5‐nitro‐5′‐hydroxy‐indirubin‐3′‐oxime (AGM‐130) in human plasma to support a microdose clinical trial. The method consisted of a liquid–liquid extraction for sample preparation and LC‐MS/MS analysis in the positive ion mode using TurboIonSpray^TM for analysis. d₃‐AGM‐130 was used as the internal standard. A linear regression (weighted 1/concentration) was used to fit calibration curves over the concentration range of 10–2000 pg/mL for AGM‐130. There were no endogenous interference components in the blank human plasma tested. The accuracy at the lower limit of quantitation was 96.6% with a precision (coefficient of variation, CV) of 4.4%. For quality control samples at 30, 160 and 1600 pg/mL, the between run CV was ≤5.0 %. Between‐run accuracy ranged from 98.1 to 101.0%. AGM‐130 was stable in 50% acetonitrile for 168 h at 4°C and 6 h at room temperature. AGM‐130 was also stable in human plasma at room temperature for 6 h and through three freeze–thaw cycles. The variability of selected samples for the incurred sample reanalysis was ≤12.7% when compared with the original sample concentrations. This validated LC‐MS/MS method for determination of AGM‐130 was used to support a phase 0 microdose clinical trial. Copyright © 2015 John Wiley & Sons, Ltd.     

Capillary electrophoresis for the investigation of two novel aminoalkanol derivatives of 1,7‐diethyl‐8,9‐diphenyl‐4‐azatricyclo[5.2.1.02,6] dec‐8‐ene‐3,5,10‐trione as potential anticancer drugs in water solution and serum

A simple, rapid, capillary zone electrophoresis method was developed and validated for the analysis of two novel aminoalkanol derivatives ( I ) and ( II ) of 1,7‐diethyl‐8,9‐diphenyl‐4‐azatricyclo[5.2.1.0^2,6]dec‐8‐ene‐3,5,10‐trione, which were found in earlier studies as potential anticancer drugs. Samples were analyzed to demonstrate the specificity and stability indicating ability of the developed method. The samples were extracted using n‐hexane‐ethyl acetate mixture in the ratio of 90:10. Electrophoretic separation was performed on a eCAP fused silica capillary (37 cm length, 50 µm inside diameter) with a 50 mM tetraborate buffer as a background electrolyte adjusted to pH = 2.5. The separation time of ( I ) and ( II ) was achieved within 7 min. In addition, analysis of the two compounds in the serum was conducted. Limits of detection of ( I ) and ( II ) by UV absorbance at 200 nm were achieved in the range of 87.4–92.1 ng/mL. The sufficient recovery was observed in the range of 90.3–99.8%. The quantification limits for the compounds ( I ) and ( II ) were in the range of 279.71–291.03 ng/mL, respectively. The method has been successfully applied to the analysis of compounds ( I ) and ( II ) in serum samples.     

Development of a novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt and its comparison with conventional one

A novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt was proposed and introduced for the simultaneous extraction and enrichment of the main active compounds of hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin in a formula of Zi‐Cao‐Cheng‐Qi decoction and the single herb, Fructus Aurantii Immaturus , Cortex Magnoliae Officinalis , Radix et Rhizoma , and Lithospermum erythrorhizon , composing the formula prior to their analysis by high‐performance liquid chromatography. The results obtained by the proposed procedure were compared with those obtained by conventional hollow‐fiber liquid‐phase microextraction, and the proposed procedure mechanism was described. In the procedure, a hollow‐fiber segment was first immersed in organic solvent to fill the solvent in the fiber lumen and wall pore, and then the fiber was again immersed into sodium chloride solution to cover a thin salt membrane on the fiber wall pore filling organic solvent. Under the optimum conditions, the enrichment factors of the analytes were 0.6–109.4, linearities were 0.002–12 μg/mL with r ² ≥ 0.9950, detection limits were 0.6–12 ng/mL, respectively. The results showed that oil‐in‐salt hollow‐fiber liquid‐phase microextraction is a simple and effective sample pretreatment procedure and suitable for the simultaneous extraction and concentration of trace‐level active compounds in traditional Chinese medicine.     

Miniaturized matrix solid‐phase dispersion combined with ultrasound‐assisted dispersive liquid–liquid microextraction for the determination of three pyrethroids in soil

A simple and miniaturized pretreatment procedure combining matrix solid‐phase dispersion (MSPD) with ultrasound‐assisted dispersive liquid–liquid microextraction (UA‐DLLME) technique was proposed in first time for simultaneous determination of three pyrethroids (fenpropathrin, cyhalothrin and fenvalerate) in soils. The solid samples were directly extracted using MSPD procedure, and the eluent of MSPD was used as the dispersive solvent of the followed DLLME procedure for further purification and enrichment of the analytes before GC‐ECD analysis. Good linear relationships were obtained for all the analytes in a range of 5.0–500.0 ng/g with LOQs (S/N=10) ranged from 1.51 to 3.77 ng/g. Average recoveries at three spiked levels were in a range of 83.6–98.5% with RSD≤7.3%. The present method combined the advantages of MSPD and DLLME, and was successfully applied for the determination of three pyrethroids in soil samples.     

Determination of N‐nitrosamines in cosmetic products by vortex‐assisted reversed‐phase dispersive liquid–liquid microextraction and liquid chromatography with mass spectrometry

A new analytical method for the simultaneous determination of trace levels of seven prohibited N‐nitrosamines (N‐nitrosodimethylamine, N‐nitrosoethylmethylamine, N‐nitrosopyrrolidine, N‐nitrosodiethylamine, N‐nitrosopiperidine, N‐nitrosomorpholine, and N‐nitrosodiethanolamine) in cosmetic products has been developed. The method is based on vortex‐assisted reversed‐phase dispersive liquid–liquid microextraction, which allows the extraction of highly polar compounds, followed by liquid chromatography with mass spectrometry. The variables involved in the extraction process were studied to obtain the highest enrichment factor. Under the selected conditions, 75 μL of water as extraction solvent was added to 5 mL of n‐hexane sample solution and assisted by vortex mixing during 30 s to form the cloudy solution. The method was successfully validated showing good linearity (0.5–50 ng/mL), enrichment factors up to 65 depending on the target compound, limits of detection values of 1.8–50 ng/g, and good repeatability (RSD < 9.8%). Finally, the proposed method was applied to different cosmetic samples. Quantitative relative recovery values (80–113%) were obtained, thus showing that matrix effects were negligible. The achieved analytical features of the proposed method, besides of its simplicity and affordability, make it useful to perform the quality control of cosmetic products to ensure the safety of consumers.     

Enantioselective capillary electrophoresis for pharmacokinetic analysis of methadone and 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in equines anesthetized with ketamine and isoflurane

An enantioselective assay for the determination of methadone and its main metabolite 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in equine plasma based on capillary electrophoresis with highly sulfated γ‐cyclodextrin as chiral selector and electrokinetic analyte injection is described. The assay is based on liquid/liquid extraction of the analytes at alkaline pH from 0.1 mL plasma followed by electrokinetic sample injection of the analytes from the extract across a buffer plug without chiral selector. Separation occurs cationically at normal polarity in a pH 3 phosphate buffer containing 0.16% (w/v) of highly sulfated γ‐cyclodextrin. The developed assay is precise (intra‐ and interday RSD < 4% and < 7%, respectively), is capable to determine enantiomer levels of methadone and 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in plasma down to 2.5 ng/mL, and was successfully applied to monitor enantiomer drug and metabolite levels in plasma of a pony that was anesthetized with racemic ketamine and isoflurane and received a bolus of racemic methadone and a bolus followed by constant rate infusion of racemic methadone. The data suggest that the assay is well suited for pharmacokinetic purposes.     

New oil‐in‐salt liquid‐phase microextraction on permutite for the extraction and concentration of alkaloids in Coptis chinensis

A novel oil‐in‐salt liquid‐phase microextraction was developed and introduced for the extraction and concentration of the trace levels of active alkaloids in Coptis chinensis prior to being analyzed by high‐performance liquid chromatography with ultraviolet detection. Also, the oil‐in‐salt extraction mechanism was analyzed, the enrichment factor and extraction recovery were redefined, and the proposed method was compared with other methods. In the approach, the mixed solvent of pentanol/octanol (6:4, v/v) and NaCl (20% w/v) are immobilized on the permutite surface in turn to form oil‐in‐salt double membranes, through which the target analytes can be molecularized though salting‐out effect and be extracted by organic solvent. The main parameters affecting the approach were investigated and optimized. Under the optimized conditions, the enrichment factors of the analytes were 30–117, the linear ranges were 0.002–2 μg/mL for jatrorrhizine, coptisine, and palmatine, and 0.001–3 μg/mL for berberine (r ² ≥ 0.9923). The limits of detection were less than 1 ng/mL. Satisfactory recoveries (84.3%–120.3%) and precision (0.9%–7.5%) were also obtained. These results confirm that the approach is a simple and reliable sample pretreatment procedure and allows for the quantification of active alkaloids in C. chinensis at actual concentration levels.     

Determination of chlorophenols in water using dispersive liquid–liquid microextraction coupled with water‐in‐oil microemulsion electrokinetic chromatography in normal stacking mode

The current routes to couple dispersive liquid–liquid microextraction with capillary electrophoresis are the evaporation of water immiscible extractants and the back‐extraction of analytes. In this study, a new methodology for this combination using water‐in‐oil microemulsion electrokinetic chromatography coupled with normal stacking mode on‐line sample concentration was developed to analyze chlorophenols in water samples. The analytes were extracted with tributyl phosphate and the extractant dilution (3×) was directly injected into an electrophoresis buffer (7.7 cm) containing 5% sodium dodecyl sulfate, 78% 1‐butanol, 2% 1‐heptane, and 15% sodium acetate solution (pH 8.0). This proposed method is very simple and convenient compared to the conventional procedures. The key parameters affecting separation and concentration were systematically optimized. Under the optimized conditions, dispersive liquid–liquid microextraction contributed an enrichment factor of 45–50, and the overall sensitivity improvement was 312–418‐fold. Limits of detection between 1.4 and 3.0 ng/mL and limits of quantification between 4.5 and 10.2 ng/mL were achieved. Acceptable repeatability lower than 3.0% for migration time and 9.0% for peak areas were obtained. The developed method was successfully applied for analysis of the chlorophenols in real water samples.