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.     

Salt‐assisted dispersive liquid–liquid microextraction for enhancing the concentration of matrine alkaloids in traditional Chinese medicine and its preparations

A fast, simple, and efficient salt‐assisted dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography was developed and introduced for the simultaneous enrichment, extraction, and determination of the trace levels of matrine alkaloids (sophoridine, matrine, and sophocarpine) in Sophorae Flavescentis Radix and Composite Kushen injection. Compared with conventional dispersive liquid–liquid microextraction, the proposed method, with added salt but without dispersant and centrifuging, makes the operation simpler, greener, and leads to a higher enrichment factor. The crucial parameters affecting the enrichment factors of target analytes, such as type and volume of extraction solvent, pH of sample phase, salt concentration, volume of sample phase, and extraction time, were investigated and optimized, meanwhile, the extraction mechanism of the method was analyzed and described. Under the optimized conditions, the enrichment factors of the three matrine alkaloids were 150, 178, and 227, respectively. Good linearities (r² ≥ 0.9992) for all analytes, low limits of detection (less than 0.08 ng/mL), satisfactory precisions (2.1–12.3%), and accuracies (recoveries, 99.3–103.9%) were achieved. The experimental results showed that the approach is a simple, fast, green, eco‐friendly, and sensitive method and can be used for the preconcentration and determination of matrine alkaloids in traditional Chinese medicines and their preparations.     

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.     

Development of a novel stirrerliquid/solid microextraction method for the separation and enrichment of trace levels of active compounds in traditional Chinese medicine

A novel stirrer‐liquid/solid microextraction method was developed for the separation and enrichment of trace levels of curcumin, bisdemethoxycurcumin, and demethoxycurcumin in Rhizoma Curcumae Longae, Radix Curcumae, and Rhizoma Curcumae before their analysis by high‐performance liquid chromatography with ultraviolet detection. In the proposed approach, a magnetic stirrer was immersed in decanol to coat its surface completely with decanol, which was used as an extraction platform. The stirrer coated with decanol is not only a power to agitate the sample solution to constantly update the sample on the stirrer surface but also it can adsorb and extract the target analytes. Some effective parameters, including suitable superficial area of stirrer, extraction solvent, sample phase pH, NaCl concentration, stirring rate, extraction time, sample phase volume, were analyzed and selected. Under the optimal conditions, the linearities are 0.0044–2.20 μg/mL, detection limits are 0.3–0.6 ng/mL, and the extraction content per unit length and enrichment factors of the target analytes are 6.24–9.71/mm and 589–917, respectively. Also, the stirrer‐liquid/solid microextraction mechanism for the extraction and enrichment of the target analytes was analyzed and expounded. The results showed that stirrer‐liquid/solid microextraction is a simple, rapid sample pretreatment approach with a high enrichment factor.     

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.     

Three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase for extraction and preconcentration of main active compounds in a traditional Chinese medicinal formula

A three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase was developed and coupled with high‐performance capillary electrophoresis for the simultaneous extraction, enrichment, and determination of main active compounds (hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin) in a traditional Chinese medicinal formula. In this procedure, two hollow fibers, impregnated with n‐heptanol/n‐nonanol (7:3, v/v) mixture in wall pores as the extraction phase and a combination (9:1, v/v) of methyltrioctylammonium chloride/glycerol (1:3, n/n) and methanol in lumen as the acceptor phase, were immersed in the aqueous sample phase. The target analytes in the sample solution were first extracted through the organic phase, and further back‐extracted to the acceptor phase during the stirring process. Important extraction parameters such as types and composition of extraction solvent and deep eutectic solvent, sample phase pH, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, detection limits were 0.3–0.8 ng/mL with enrichment factors of 6–114 for the analytes and linearities of 0.001–13 μg/mL (r² ≥ 0.9901). The developed method was successfully applied to the simultaneous extraction and concentration of the main active compounds in a formula of Zi‐Cao‐Cheng‐Qi decoction with the major advantages of convenience, effectiveness, and environmentally friendliness.     

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid‐phase extraction combined with dispersive liquid–liquid microextraction and high‐performance liquid chromatography

Solid‐phase extraction coupled with dispersive liquid–liquid microextraction was developed as an ultra‐preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion‐methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid‐phase extraction coupled with dispersive liquid–liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid‐phase extraction coupled with dispersive liquid–liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9–6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.     

Ballpoint connector‐protected salt‐oil‐salt liquid phase microextraction for concentration and enrichment of trace anthraquinone compounds in rhubarb

This study proposed a new ballpoint connector‐protected salt‐oil‐salt liquid phase microextraction for extraction and enrichment of trace rhein and chrysophanol in rhubarb prior to determination of the analytes by high performance liquid chromatography. In this study, a handy ballpoint connector (between ballpoint tip and ink chamber) was used as extraction device, in which its cavity was filled with n‐octanol, and the bare n‐octanol in its two opening ends was covered with a thin layer of sodium chloride film. The design subtly assembled salt film onto ballpoint connector for extraction and enrichment, which greatly improved the enrichment factors of the target analytes. Moreover, the novel procedure and its extraction mechanism were described and analyzed, and several crucial parameters reflecting the extraction effect were investigated and optimized. Under optimum conditions, high enrichment factors (247 and 127), good linearities with r ≥ 0.9998, limits of detection (0.6–1.1 ng/mL), relative standard deviations of intra‐ and interday (2.2–8.8% and 4.3–8.9%), and average recoveries (97.6–98.1%), were obtained, respectively. The proposed method can not only eliminate the negative effects from viscosity and ion strength at high salt concentration of sample phase, but also make salting‐out effect be focused on small area so as to maximize the extraction effect.     

Ion‐pair switchable‐hydrophilicity solvent‐based homogeneous liquid–liquid microextraction for the determination of paraquat in environmental and biological samples before high‐performance liquid chromatography

An approach involving ion‐pair switchable‐hydrophilicity solvent‐based homogeneous liquid–liquid microextraction coupled to high‐performance liquid chromatography has been applied for the preconcentration and separation of paraquat in a real sample. A mixture of triethylamine and water was used as the switchable‐hydrophilicity solvent. The pH was regulated using carbon dioxide; hence the ratio of the ionized and non‐ionized form of triethylamine could control the optimum conditions. Sodium dodecyl sulfate was utilized as an ion‐pairing agent. The ion‐associate complex formed between the cationic paraquat and sodium dodecyl sulfate was extracted into triethylamine. The separation of the two phases was carried out by the addition of sodium hydroxide, which changed the ionization state of triethylamine. The effects of some important parameters on the extraction recovery were investigated. Under the optimum conditions (500 μL of the extraction solvent, 1 mg sodium dodecyl sulfate, 2.0 mL of 10 mol/L sodium hydroxide, and pH 4), the limit of detection and the limit of quantification were 0.2 and 0.5 μg/L, respectively, with preconcentration factor of 74. The precision (RSD, n  = 10) was  <5%. The recovery of the analyte in environmental and biological samples was in the range of 90.0–92.3%.     

Dispersive admicelle solid‐phase extraction based on sodium dodecyl sulfate coated Fe3O4 nanoparticles for the selective adsorption of three alkaloids in Gegen‐Qinlian oral liquid before high‐performance liquid chromatography

A novel dispersive admicelle solid‐phase extraction method based on sodium dodecyl sulfate‐coated Fe₃O₄ nanoparticles was developed for the selective adsorption of berberine, coptisine, and palmatine in Gegen‐Qinlian oral liquid before high‐performance liquid chromatography. Fe₃O₄ nanoparticles were synthesized by a chemical coprecipitation method and characterized by using transmission electron microscopy. Under acidic conditions, the surface of Fe₃O₄ nanoparticles was coated with sodium dodecyl sulfate to form a nano‐sized admicelle magnetic sorbent. Owing to electrostatic interaction, the alkaloids were adsorbed onto the oppositely charged admicelle magnetic nanoparticles. The quick separation of the analyte‐adsorbed nanoparticles from the sample solution was performed by using Nd‐Fe‐B magnet. Best extraction efficiency was achieved under the following conditions: 800 μL Fe₃O₄ nanoparticles suspension (20 mg/mL), 150 μL sodium dodecyl sulfate solution (10 mg/mL), pH 2, and vortexing time 2 min for the extraction of alkaloids from 10 mL of diluted sample. Four hundred microliters of methanol was used to desorb the alkaloids by vortexing for 1 min. Satisfactory extraction recoveries were obtained in the range of 85.9–120.3%, relative standard deviations for intra‐ and interday precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied to analyze the alkaloids in two batches of Gegen‐Qinlian oral liquids.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Application of in-situ formed polymer-based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction for the extraction of neonicotinoid pesticides from milk samples

An in-situ formed polymer–based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction was developed for the extraction of neonicotinoid pesticides from milk samples. The extracted analytes were determined using high-performance liquid chromatography–diode array detector. In this approach, after precipitating the proteins of milk using a zinc sulfate solution, the supernatant phase (containing sodium chloride) was transferred into another glass test tube, and a homogenous solution of polyvinylpyrrolidone and a suitable water-miscible organic solvent was rapidly injected into it. By this step, the polymer particles were re-produced and the analytes were extracted onto the sorbent surface. In the following step, the analytes were eluted with an appropriate organic solvent to use in the following solidification of floating organic droplet-based dispersive liquid–liquid microextraction step that was done to acquire the low limits of detection. Under the optimized conditions, satisfactory results consisting of low limits of detection (0.13–0.21 ng/ml) and quantification (0.43–0.70 ng/ml), high extraction recoveries (73%–85%), and enrichment factors (365–425), and good repeatability (relative standard deviations equal or less than 5.1% and 5.9% for intra- and inter-day precisions, respectively) were obtained.     

Development of new extraction method based on liquid–liquid–liquid extraction followed by dispersive liquid–liquid microextraction for extraction of three tricyclic antidepressants in plasma samples

In the present study, a new extraction method based on a three–phase system, liquid–liquid–liquid extraction, followed by dispersive liquid–liquid microextraction has been developed and validated for the extraction and preconcentration of three commonly prescribed tricyclic antidepressant drugs – amitriptyline, imipramine, and clomipramine – in human plasma prior to their analysis by gas chromatography–flame ionization detection. The three phases were an aqueous phase (plasma), acetonitrile and n–hexane. The extraction mechanism was based on the different affinities of components of the biological sample (lipids, fatty acids, pharmaceuticals, inorganic ions, etc.) toward each of the phases. This provided high selectivity toward the analytes since most interferences were transferred into n–hexane. In this procedure, a homogeneous solution of the aqueous phase (plasma) and acetonitrile (water–soluble extraction solvent) was broken by adding sodium sulfate (as a phase separating agent) and the analytes were extracted into the fine droplets of the formed acetonitrile. Next, acetonitrile phase was mixed with 1,2–dibromoethane (as a preconcentration solvent at microliter level) and then the microextraction procedure mentioned above was performed for further enrichment of the analytes. Under the optimum extraction conditions, limits of detection and lower limits of quantification for the analytes were obtained in the ranges of 0.001–0.003 and 0.003–0.010 μg mL⁻¹, respectively. The obtained extraction recoveries were in the range of 79–98%. Intra– and inter–day precisions were < 7.5%. The validated method was successfully applied for determination of the selected drugs in human plasma samples obtained from the patients who received them.     

Graphene‐sensitized microporous membrane/solvent microextraction for the preconcentration of cinnamic acid derivatives in Rhizoma Typhonii

A novel graphene‐sensitized microporous membrane/solvent microextraction method named microporous membrane/graphene/solvent synergistic microextraction, coupled with high‐performance liquid chromatography and UV detection, was developed and introduced for the extraction and determination of three cinnamic acid derivatives in Rhizoma Typhonii. Several factors affecting performance were investigated and optimized, including the types of graphene and extraction solvent, concentration of graphene dispersed in octanol, sample phase pH, ionic strength, stirring rate, extraction time, extraction temperature, and sample volume. Under optimized conditions, the enrichment factors of cinnamic acid derivatives ranged from 75 to 269. Good linearities were obtained from 0.01 to 10 μg/mL for all analytes with regression coefficients between 0.9927 and 0.9994. The limits of quantification were <1 ng/mL, and satisfactory recoveries (99–104%) and precision (1.1–10.8%) were also achieved. The synergistic microextraction mechanism based on graphene sensitization was analyzed and described. The experimental results showed that the method was simple, sensitive, practical, and effective for the preconcentration and determination of cinnamic acid derivatives in Rhizoma Typhonii.     

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.     

Determination of phthalic acid esters in Chinese white spirit using dispersive liquid–liquid microextraction coupled with sweeping β‐cyclodextrin‐modified micellar electrokinetic chromatography

A simple method that consumes low organic solvent is proposed for the analysis of phthalic acid esters in Chinese white spirit using dispersive liquid–liquid microextraction coupled with sweeping‐micellar electrokinetic chromatography. Tetrachloromethane and white‐spirit‐containing ethanol were used as the extraction and dispersing solvents, respectively. The electrophoresis separation buffer was composed of 5 mM β‐cyclodextrin, 50 mM sodium dodecyl sulfate and 25 mM borate buffer (pH 9.2) with 9% acetonitrile, enabling the baseline resolution of the analytes within 13 min. Under the optimum conditions, satisfactory linearities (5–1000 ng/mL, r ≥ 0.9909), good reproducibility (RSD ≤ 6.7% for peak area, and RSD ≤ 2.8% for migration time), low detection limits (0.4–0.8 ng/mL) and acceptable recovery rates (89.6–105.7%) were obtained. The proposed method was successfully applied to 22 Chinese white spirits, and the content of dibutyl phthalate in 55% of the samples exceeded the Specific Migration Limit of 0.3 mg/kg established by the domestic and international regulations.     

Simultaneous derivatization and lighter‐than‐water air‐assisted liquid–liquid microextraction using a homemade device for the extraction and preconcentration of some parabens in different samples

Simultaneous derivatization and air‐assisted liquid–liquid microextraction using an organic that is solvent lighter than water has been developed for the extraction of some parabens in different samples with the aid of a newly designed device for collecting the extractant. For this purpose, the sample solution is transferred into a glass test tube and a few microliters of acetic anhydride (as a derivatization agent) and p‐xylene (as an extraction solvent) are added to the solution. After performing the procedure, the homemade device consists of an inverse funnel with a capillary tube placed into the tube. In this step, the collected extraction solvent and a part of the aqueous solution are transferred into the device and the organic phase indwells in the capillary tube of the device. Under the optimal conditions, limits of detection and quantification for the analytes were obtained in the ranges of 0.90–2.7 and 3.0–6.1 ng/mL, respectively. The enrichment and enhancement factors were in the ranges of 370–430 and 489–660, respectively. The method precision, expressed as the relative standard deviation, was within the range of 4–6% (n = 6) and 4–9% (n = 4) for intra‐ and interday precisions, respectively. The proposed method was successfully used for the determination of methyl‐, ethyl‐, and propyl parabens in cosmetic, hygiene and food samples, and personal care products.     

Study of enrichment factors for six β‐blockers in aliphatic alcohols by hollow‐fiber liquid‐phase microextraction

The selectivity of a suitable organic solvent is key for extraction in liquid‐phase microextraction experiments. Nevertheless, the screening process remains a daunting task. Our research aimed to study the relationship between extraction efficiency and extraction solvents, analytes, and finally select the appropriate extraction solvent. In the present article, β‐blockers and six extraction solvents were chosen as the models and hollow‐fiber liquid‐phase microextraction was conducted. The relationship was built by statistical analysis on the data. Factors affecting extraction efficiency including the logarithms of the octanol/water partition coefficient (logP_o/w) of analytes, acid dissociation constants, the logarithms of the octanol/water partition coefficient of solvents and pH of the sample solution were investigated. The results showed that a low water solubility of extraction solvent is the foundation to ensure higher extraction efficiency. Moreover, when ΔlogP_o/w > 0, a higher extraction efficiency is observed at lower ΔlogP_o/w, on the contrary, when ΔlogP_o/w < 0, extraction efficiency is higher as the absolute value of ΔlogP_o/w becomes greater. Finally, the relationship between enrichment factor and extraction solvents, analytes was established and a helpful guidance was provided for the selection of an optimal solvent to obtain the best extraction efficiency by liquid‐phase microextraction.     

Determination of 19 sulfonamides residues in pork samples by combining QuEChERS with dispersive liquid–liquid microextraction followed by UHPLC–MS/MS

A new simple and rapid pretreatment method for simultaneous determination of 19 sulfonamides in pork samples was developed through combining the QuEChERS method with dispersive liquid–liquid microextraction followed by ultra‐high performance liquid chromatography with tandem mass spectrometry. The sample preparation involves extraction/partitioning with QuEChERS method followed by dispersive liquid–liquid microextraction using tetrachloroethane as extractive solvent and the acetonitrile extract as dispersive solvent that obtained by QuEChERS. The enriched tetrachloroethane organic phase by dispersive liquid–liquid microextraction was evaporated, reconstituted with 100 μL acetonitrile/water (1:9 v/v) and injected into an ultra‐high performance liquid chromatography with a mobile phase composed of acetonitrile and 0.1% v/v formic acid under gradient elution and separated using a BHE C₁₈ column. Various parameters affecting the extraction efficiency were investigated. Matrix‐matched calibration curves were established. Good linear relationships were obtained for all analytes in a range of 2.0–100 μg/kg and the limits of detection were 0.04–0.49 μg/kg. Average recoveries at three spiking levels were in the range of 78.3–106.1% with relative standard deviations less than 12.7% (n = 6). The developed method was successfully applied to determine sulfonamide residues in pork samples.     

Basalt fibers functionalized with gold nanoparticles for in‐tube solid‐phase microextraction

Basalt fibers were functionalized with gold nanoparticles and characterized by scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. An in‐tube solid‐phase microextraction device was developed by packing the functionalized basalt fibers in a polyether ether ketone tube. The device was connected into high performance liquid chromatography equipment with a diode array detector to build online enrichment and analysis system. Eight polycyclic aromatic hydrocarbons were used as model analytes, important factors including sampling rate, sampling volume, organic solvent content in sample, and desorption time were investigated. Linear range (0.01–20 μg/L), detection limits (0.003–0.015 μg/L), and enrichment factors (130–1628) were given by the online analysis method. Relative standard deviations (n = 5) of extraction repeatability on one tube and tube‐to‐tube repeatability were less than 5.2 and 14.7%, respectively. The analysis method was applied to detect polycyclic aromatic hydrocarbons in environmental water samples, and relative recoveries ranged from 87 to 128%.