Hollow fiber‐based liquid membrane microextraction combined with high‐performance liquid chromatography for extraction and determination of trimetazidine in human plasma

A hollow fiber‐based liquid phase microextraction strategy combined with high‐performance liquid chromatography was evaluated for the quantitative determination of trimetazidine in human plasma. Trimetazidine was extracted from a 2.1 mL basified plasma sample (donor phase) into the organic solvent (n‐octanol) impregnated in the pores of a hollow fiber and then extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. The result showed that transport of drugs from alkaline sample solution into 0.5 m HCl occurred efficiently when 25 μL of 250 mm sodium 1‐octanesulfonate was added into the donor phase. Several parameters influencing the efficiency of the method, such as the nature of organic solvent used to impregnate the membrane, compositions of donor phase and acceptor phase, type and concentration of carrier, extraction time, stirring rate and salt concentration, were investigated and optimized. Under the optimal conditions, the calibration curves were obtained in the range of 5–200 ng/mL with reasonable linearity (r > 0.9980). The method was successfully applied to determine the concentration of trimetazidine in human plasma. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of Double-Phase Liquid Phase Microextraction in the Determination of Partition Coefficients and Analysis of Pesticides in Water Samples

A simple and solvent-minimized sample preparation technique based on two-phase hollow fiber-protected liquid-phase microextraction has been developed and used for the determination of partition coefficient and analysis of selected pesticides in environmental water samples. The analysis was performed by gas chromatography–electron capture detector. Three pesticides namely hexaconazole, quinalphos, and methidathion were considered as target analytes. Extraction conditions such as solvent identity, salt concentration, stirring speed, extraction time, length of the hollow fiber, and volume of donor phase were optimized. The analytes were extracted from a donor phase (water sample) through 3 μL of an organic solvent immobilized in the pores of a porous polypropylene hollow fiber and then into the acceptor phase present inside the hollow fiber. Excellent extractions of the analytes were achieved under the optimized conditions, with relative standard deviations of 4.6–7.9%, correlation coefficients (r ²) of 0.9954–0.9986 and limits of detection of 3–7 ng L^?1. The proposed method provided good average enrichment factors of up to 250-fold. The partition coefficients of the analytes determined were found to be directly correlated with the enrichment factor. The present methodology also confirms the robustness of microextraction for monitoring trace levels of pesticides in environmental water samples.     

Analysis of Paraben Preservatives in Cosmetic Samples: Comparison of Three Different Dynamic Hollow Fiber Liquid-Phase Microextraction Methods

This study focused on a comparison of three different dynamic hollow fiber-based liquid-phase microextraction (DHF-LPME) methods for extraction and preconcentration of parabens from wastewater, toothpaste, cream, and shampoo samples. The first method is two-phase DHF-LPME, in which n-octanol was used as the extraction solvent. The second is three-phase DHF-LPME, in which n-octanol and basic aqueous solution were used as the extraction solvent and acceptor phase, respectively. High-performance liquid chromatography with UV detection (HPLC–UV) was applied for determination of the parabens in both methods. The third method is a recently introduced method; three-phase DHF-LPME based on two immiscible organic solvents (n-dodecane as organic solvent and acetonitrile as an acceptor phase). The quantitative analyses were performed by the use of gas chromatography-mass spectrometry (GC–MS) after injection port derivatization. The effect of different extraction conditions (i.e., extraction solvent, pH, ionic strength, stirring rate, and dynamic and extraction times) on the extraction efficiency of the parabens was investigated and optimized. All the three procedures provide similar working parameters characterized by high repeatability (3.9–6.3 %) and good linearity (correlation coefficient ranging from 0.989 to 0.998). Results of real sample analyses obtained by these three methods were highly correlated. Although all methods provide compatible alternatives for paraben analysis, the three-phase DHF-LPME based on two immiscible organic solvents may be a more appropriate technique due to its higher extraction efficiency and thus lower limits of detection (LODs). LODs for all the parabens ranged from 0.2 to 5.0 μg L^?1 using the two first methods combined with HPLC–UV. An improvement in sensitivity of several orders of magnitude was achieved using three-phase DHF-LPME based on two immiscible organic solvents followed by single-ion monitoring GC–MS analyses (0.01–0.2 μg L^?1) due to compatibility of this technique with GC instrument.     

Liquid–liquid–liquid microextraction of degradation products of nerve agents followed by liquid chromatography–tandem mass spectrometry

Alkyl alkylphosphonic acids (AAPAs) are important environmental markers of nerve agents. A simple hollow fiber-based liquid–liquid–liquid microextraction (HFLLLME) technique has been developed to enrich the AAPAs from water. AAPAs were extracted from acidified aqueous phase to organic phase present in pores of the hollow fiber, and then back extracted into the alkaline acceptor phase present in the lumen of the hollow fiber. Variables affecting the HFLLLME process were optimized using a Plackett–Burman design and a Doehlert design. Optimal experimental conditions were: organic solvent, 1-octanol; pH of acceptor phase, 14; extraction time, 60 min; pH of donor phase, 1; and NaCl concentration, 10% (w/v). Depending upon the alkyl substituent, lower limits of detection varied from 0.1 to 100 ng mL⁻¹ (S/N ≥ 5). Repeatability of the method was observed with relative standard deviation of 1.49–9.83% (n = 3). After validation, the method was applied to detect AAPAs present in the water sample provided by the Organization for Prohibition of Chemical Weapons (OPCW) during the 23rd official proficiency test. The added advantage of this method is that several successive extractions of AAPAs from the same water sample can be performed.     

Determination of estrogens in wastewater using three-phase hollow fiber-mediated liquid-phase microextraction followed by HPLC

Three-phase hollow fiber-mediated liquid-phase microextraction followed by HPLC was used for the determination of three synthetic estrogens, namely diethylstilbestrol, dienestrol, and hexestrol, in wastewater. Extraction conditions including organic solvent, volume ratio between donor solution and acceptor phase, extraction time, stirring rate, donor phase and acceptor phase were optimized. The target compounds were extracted from a 10 mL aqueous sample at pH 1.5 (donor solution) through a 45 mm in length hollow polypropylene fiber that was immersed in 1-octanol in advance, and then the hollow fiber was filled with 10 microL 0.5 mol/L sodium hydroxide solution (acceptor phase). After a 40 min extraction, the acceptor phase was directly injected into an HPLC system for detection. Under the optimized extraction conditions, a large enrichment factor (more than 300-fold) was achieved for the three estrogens. The determination limit at an S/N of 3 ranged from 0.25 to 0.5 microg/L for the estrogens. The recovery ratio was more than 86% in the determination of these estrogens in wastewater.     

Extraction of hydroxyaromatic compounds in river water by liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase technique is described for the extraction of six hydroxyaromatic compounds in river water using a disposable and ready to use hollow fiber. Separation and quantitative analyses were performed using LC with UV detection at 254 nm. Analytes were extracted from the acidified sample solution (donor phase) into the organic solvent impregnated in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10 microL LC syringe. The acceptor phase was sandwitched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber using a syringe pump. This movement provides a fresh acceptor phase to come in contact with the organic phase and thus enhancing extraction kinetics thereby leading to the improvement in enrichment of the analytes. The microcap separates the acceptor phase and the donor phase in addition to being partially responsible for mass transfer of the analytes from the donor solution to the acceptor solution. Under stirring, a fresh donor phase will enter through the open end of the fiber that will also contribute to the mass transfer. Various parameters affecting the extraction efficiency viz type of organic solvent, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. RSD (3.9-5.6%), correlation coefficient (0.995-0.997), detection limit (2.0-51.2 ng/mL), enrichment factor (339-630), relative recovery (93.2-97.9%), and absolute recovery (33.9-63.0%) have also been investigated. The developed method was applied for the analysis of river water.     

Determination of Gold by Flame Atomic Absorption Spectrometry with Hollow Fiber Liquid Phase Microextraction Using Room Temperature Ionic Liquids

A novel method to preconcentrate gold was developed employing a synergistic enhancement of a room temperature ionic liquid combined with hollow fiber liquid phase micro-extraction with flame atomic absorption spectrometry detection. The method is based on the complexation of gold with dithizone. The formed hydrophobic complex was subsequently extracted into the lumen of a hollow fiber. The organic phase was siphoned into FAAS for the determination. A room temperature ionic liquid and dithizone were used the enhancement reagent and chelating reagent, respectively. The addition of a room temperature ionic liquid led to a five-fold improvement in the extraction of gold. The 1-octanol was immobilized in the pores of the polypropylene hollow fiber as the liquid membrane and was also used as the acceptor solution. Some parameters that influenced extraction and determination were evaluated in detail, such as concentrations of the ionic liquid and dithizone, pH of samples, stirring rates, extraction time, and interferences. Under optimized conditions, a detection limit of 0.9 ng mL^?1 and an enrichment factor of 130 were achieved. The relative standard deviation (RSD) was 3.7% for Au (40 ng mL^?1, n = 5). The proposed method was successfully applied to the determination of gold in certified reference environmental samples and ore samples with satisfactory results.     

Simultaneous derivatization and extraction of iodine from milk samples by hollow fiber liquid-phase microextraction followed by gas chromatography-electron capture detection

A simple, low-cost and sensitive method is demonstrated for derivatization and extraction of iodine from milk samples using hollow fiber liquid-phase microextraction (HF-LPME) and gas chromatography-electron capture detection. Iodide ions are converted to iodine under acidic medium and in the presence of an oxidant. The generated iodine reacted with 3-pentanone in extraction vial to give 2-iodo-3-pentanone and was extracted into 4 μL of 1-octanol located in the lumen of a hollow fiber. Organic solvent was selected using one variable at a time optimization method and the other main factors affecting derivatization and HF-LPME procedures were evaluated using a Taguchi’s L₁₆ (4⁵) orthogonal array. Under optimal conditions, the method showed low limit of detection (0.5 ng mL^?1), wide linear range (1–2,000 ng mL^?1) with good correlation coefficient (0.9997) and acceptable relative standard deviation (4.6 %, n = 5). Finally, the developed method was successfully applied for determination of iodide in real samples including infant milk formulas and cow milk with reasonable relative recoveries (99.8–110.5 %).     

Extraction,preconcentration, and determination of methylphenidate in urine sample using solvent bar microextraction in combination with HPLC–UV: Optimization by experimental design

Methylphenidate (Ritalin) is a drug used for attention-deficit hyperactivity disorder treatment and narcolepsy symptoms control. This drug inhibits norepinephrine and dopamine reuptake in presynaptic neuron and appears to stimulate the cerebral cortex and subcortical structures similar to amphetamines. The aim of this work is to develop a new method for extraction, preconcentration, and determination of methylphenidate in human urine samples using solvent bar microextraction combined with HPLC and optimization by design of experiment approach. To get to the highest preconcentration factor, the effect of various affecting parameters such as the type of extraction solvent, donor phase pH, receiving phase pH, salt addition to the acceptor phase, extraction time, stirring speed, and extraction temperature was investigated and optimized by design of experiment approach. Under the optimized condition extraction (solvent: n-octanol, donor phase pH: 11.6; acceptor phase pH: 4; stirring speed: 650?rpm; extraction time: 25?min; temperature: 25°C; salt concentration in donor phase: 30% w/v NaCl), the following results were achieved: preconcentration factor: 104, limit of detection: 15?ng/mL, intra-day RSD: 3.5%, and inter-day RSD: 3.9%. Finally, the feasibility of this extraction method was confirmed by analyzing urine sample and satisfactory results were obtained.     

Multivariate optimization of the hollow fiber-based liquid phase microextraction of lead in human blood and urine samples using graphite furnace atomic absorption spectrometry

The present study developed a liquid-phase microextraction based on hollow fiber coupled with graphite furnace atomic absorption spectrometry for the effective extraction and quantitation of lead from urine and blood samples. A multivariate design was used for the optimization of the experimental conditions to ensure high extraction efficiency. Six factors (solvent type, chelating agent, time extraction, temperature, donor phase pH, and acceptor phase pH) were obtained by screening eleven factors of the Plackett–Burman design; these were optimized using the central composite design of response surface methodology. The optimum conditions of donor phase pH, acceptor phase pH, temperature, and extraction time were 5, 9.5, 40 °C, and 120 min, respectively. In addition, oleic acid containing dicyclohexyl-18-krone-6 was used for the membrane phase. Under optimal conditions, the enrichment factor, limit of detection, and limit of quantification were obtained in the ranges of 21.3–18.7, 0.001–0.002 ng mL^?1, and 0.008–0.01 ng mL^?1, respectively, in urine and blood samples. The linearity of the calibration curve was established for the concentration of Pb in the range of 1–50 ng mL^?1 (r²?=?0.9983). Finally, the performance of the developed method was evaluated for the determination of lead in urine and blood samples, and satisfactory results were obtained (RSDs <?10% with recovery >?95).     

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase for the extraction of phenoxyacetic acids prior to liquid chromatography detection

A simple liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase (LLLME/AMADP) technique is described for the quantitative determination of five phenoxyacetic acids in water using a disposable and ready to use hollow fiber. The target compounds were extracted from the acidified sample solution (donor phase) into the organic solvent residing in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10-microl syringe. The acceptor phase was sandwiched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber assisted by a programmable syringe pump. This repeated movement provides a fresh acceptor phase to come in-contact with the organic phase and thus enhancing extraction kinetics leading to high enrichment of the analytes. The microcap separates the aqueous acceptor phase and the donor phase in addition of being partially responsible for mass transfer of the analytes from donor solution (moving in and out of the hollow fiber from the open end of the fiber) to the acceptor solution. Separation and quantitative analyses were then performed using liquid chromatography (LC) with ultraviolet (UV) detection at 280 nm. Various parameters affecting the extraction efficiency viz. type of organic solvent used for immobilization in the pores of the hollow fiber, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. Repeatability (RSD, 3.2-7.4%), correlation coefficient (0.996-0.999), detection limit (0.2-2.8 ng ml(-1)) and enrichment factors (129-240) were also investigated. Relative recovery (87-101%) and absolute recoveries (4.6-13%) have also been calculated. The developed method was applied for the analysis of river water.     

Hollow fiber liquid-phase microextraction for the determination of trace amounts of rosiglitazone (anti-diabetic drug) in biological fluids using capillary electrophoresis and high performance liquid chromatographic methods

A three-phase hollow fiber liquid-phase microextraction (HF-LPME) coupled either with capillary electrophoresis (CE) or high performance liquid chromatography (HPLC) with UV detection methods was successfully developed for the determination of trace levels of the anti-diabetic drug, rosiglitazone (ROSI) in biological fluids. The analyte was extracted into dihexyl ether that was immobilized in the wall pores of a porous hollow fiber from 10 mL of aqueous sample, pH 9.5 (donor phase), and was back extracted into the acceptor phase that contained 0.1 M HCl located in the lumen of the hollow fiber. Parameters affecting the extraction process such as type of extraction solvent, HCl concentration, donor phase pH, extraction time, stirring speed, and salt addition were studied and optimized. Under the optimized conditions (extraction solvent, dihexyl ether; donor phase pH, 9.5; acceptor phase, 0.1 M HCl; stirring speed, 600 rpm; extraction time, 30 min; without addition of salt), enrichment factor of 280 was obtained. Good linearity and correlation coefficients of the analyte was obtained over the concentration ranges of 1.0–500 and 5.0–500 ng mL⁻¹ for the HPLC (r² = 0.9988) and CE (r² = 0.9967) methods, respectively. The limits of detection (LOD) and limits of quantitation (LOQ) for the HPLC and CE methods were (0.18, 2.83) and (0.56, 5.00) ng mL⁻¹, respectively. The percent relative standard deviation (n = 6) for the extraction and determination of three concentration levels (10, 250, 500 ng mL⁻¹) of ROSI using the HPLC and CE methods were less than 10.9% and 13.2%, respectively. The developed methods are simple, rapid, sensitive and are suitable for the determination of trace amounts of ROSI in biological fluids.     

Separation and Determination of Amitriptyline and Nortriptyline in Biological Samples Using Single-Drop Microextraction with GC

The combination of liquid phase microextraction (LPME) based on a single drop and gas chromatography flame ionization detector (GC-FID) was used for separation and determination of amitriptyline and nortriptyline in human plasma and urine samples. The sample solution was kept alkaline (pH 12), then a microdrop of organic solvent (isooctane) was suspended in the donor solution; after extraction, the organic microdrop was injected into the GC-FID. Experimental LPME conditions were optimized. Finally, the enrichment factors (89.5?C139.0), the relative standard deviation (RSD%, n = 5) 1.1?C8.5, linearity ranges (0.05?C20 ??g mL^?1), and the limits of detections (0.01, 0.02 ??g mL^?1) for selected drugs were evaluated.     

Determination of chlorophenols in environmental water samples using directly suspended droplet liquid-liquid-liquid phase microextraction prior to high-performance liquid chromatography

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5?mL acidic donor phase, (pH 2, P1) into an organic phase, 350?µL?of benzene/1-octanol (90?:?10 v/v, P2) and then were back-extracted into a 7?µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe and neutralised by adding of 7?µL HCl 0.1?M. The total amount was eventually injected into the HPLC system with UV detection at 225?nm for further analysis. Parameters such as the organic solvent, phases volumes, extraction and back-extraction times, stirring rate and pH values were optimised. The calibration graphs are linear in the range of 10–2000?µg?L^?1 with r?≥?0.9973. The enrichment factors were ranged from 115 to 170, and the limit of detection (LOD, n?=?7) varied from 5 to 10?µg?L^?1. The relative standard deviations (RSDs, n?=?5) were found 6.8 to 7.4 at S/N?=?3. All experiments were carried out at room temperature, (22?±?0.5°C).     

Electromembrane extraction and anodic stripping voltammetric determination of mercury(II) using a glassy carbon electrode modified with gold nanoparticles

This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg^.L^?1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg^.L^?1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy.

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Graphical abstract Hg(II) ions were extracted from a donor phase into an acidic acceptor phase (15 μL) placed in the lumen of a hollow fiber using electromembrane extraction. The acceptor phase was then analyzed using anodic stripping voltammetry.

     

Determination of phenytoin in exhaled breath condensate using electromembrane extraction followed by capillary electrophoresis

Application of hollow fiber-based electromembrane extraction was studied for extraction and quantification of phenytoin from exhaled breath condensate (EBC). Phenytoin is extracted from EBC through a supported liquid membrane consisting of 1-octanol impregnated in the walls of a hollow fiber, and into an alkaline aqueous acceptor solution inside the lumen of the fiber. Under the obtained conditions of electromembrane extraction, that is, the extraction time of 15 min, stirring speed of 750 rpm, donor phase pH at 11.0, acceptor pH at 13.0, and an applied voltage of 15 V across the supported liquid membrane, an enrichment factor of 102-fold correspond to extraction percent of 25.5% was achieved. Good linearity was obtained over the concentration range of 0.001–0.10 µg/mL (r² = 0.9992). Limits of detection and quantitation were 0.001 and 0.003 µg/mL, respectively. The proposed method was successfully applied to determine phenytoin from EBC samples of patients receiving the drug. No interfering peaks were detected that indicating excellent selectivity of the method. The intra- and interday precisions (RSDs) were less than 14%.     

Hollow-Fiber-Based LPME as a Reliable Sampling Method for Gas-Chromatographic Determination of Pharmacokinetic Parameters of Valproic Acid in Rat Plasma

A sensitive and simple method based on two-phase liquid-phase microextraction in porous hollow fiber followed by gas chromatography-flame ionization detection was developed for quantification and pharmacokinetic study of valproic acid (VPA, an antiepileptic drug) in rat plasma after oral administration of pure sodium valproate (25 mg kg^?1). Some parameters such as type of organic solvent, pH of sample solution, stirring speed, salt addition, extraction time, and volume of sample that affected extraction efficiency of VPA were optimized. Under optimized microextraction conditions, VPA was extracted with 10 μL 1-octanol from 0.5 mL rat plasma previously diluted with 4.5 mL acidified and salinated water (pH 2) using 1-octanoic acid as internal standard. The limit of detection was 17 ng mL^?1 with linear response over the concentration range of 50–10,000 ng mL^?1 with correlation coefficient higher than 0.998. The developed method was successfully applied to determination of pharmacokinetic parameters such as t _max (peak time in concentration–time profile), C _max (peak concentration in concentration–time profile), t _1/2 (elimination half-life), AUC_0–t (area under the curve for concentration versus time), clearance, and apparent distribution volume in rats following oral administration of VPA.     

Three-phase solvent bar microextraction and determination of trace amounts of clenbuterol in human urine by liquid chromatography and electrospray tandem mass spectrometry

Three-phase solvent bar microextraction (TPSBME) technique is described for the quantitative determination of trace amounts of clenbuterol (CB) in urine samples using liquid chromatography (LC) and electrospray tandem mass spectrometry (ES-TMS). CB was extracted from a basified urine sample (donor phase) into the organic solvent residing in the pores of a freely moving hollow fiber and then back extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. The ends of the fiber were pressure-sealed. Here, forward and back extraction took place spontaneously. We studied various parameters affecting the extraction efficiency viz. type of organic solvent (octanol, nonanol and dihexyl ether) used for immobilization in the pores of the hollow fiber, i.e. extraction time (10-40 min), stirring speed (0-1000 rpm), effect of sodium chloride (0-25%, w/v) and concentration of the donor (0.25-3 M NaOH) and the acceptor (0.5-5 M formic acid) phases. After extraction, CB was analyzed by injecting the analyte enriched acceptor phase into LC combined with ES-TMS. Enrichment factor (79), repeatability (R.S.D. = 5.1%), correlation coefficient (0.9972, for the range of 0.1-4 ng mL⁻¹), detection limit (7 pg mL⁻¹) were also investigated. The present technique is compared with the reported solid phase microextraction techniques in terms of selectivity, analysis time per extraction, cost of analysis per extraction, and precision. Among all microextraction techniques reported, this technique is the most economical sample preparation/preconcentration technique to our knowledge. The method was applied for the analysis of CB in human urine.     

Fast Analysis of Synthetic Pyrethroid Metabolites in Water Samples Using In-Syringe Derivatization Coupled Hollow Fiber Mediated Liquid Phase Microextraction with GC-ECD

A fast and efficient method has been demonstrated for the trace determination of six important metabolites of synthetic pyrethroids including cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis- and trans-Cl₂CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-Br₂CA), 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), 3-phenoxybenzoic acid (3-PBA), and 2-phenoxybenzoic acid (2-PBA) in environmental water samples using hollow fiber (HF)-mediated liquid-phase microextraction (LPME) coupled with in-syringe derivatization (ISD) followed by gas chromatography (GC) with electron capture detector (ECD) analysis. This method utilizes a HF membrane segment impregnated with extraction solvent as the LPME sampling probe, which was connected to a microsyringe pre-filled with derivatizing agents, and it was immersed into sample solution for extraction. After extraction, the extracting solution was subjected to derivatization reaction that was performed inside the syringe barrel followed by GC-ECD analysis. Under optimal conditions, the best extraction efficiency was obtained using sampling probe (2.0 cm hollow fiber) impregnated with 1-octanol immersed into water sample (5.0 mL, adjusted pH below 1.0) and stirring (1,250 rpm) for 10 min at 70 °C and diisopropylcarbodiimide (2 μL) and 1,1,1,3,3,3-hexafluoro-2-propanol (1 μL) were the derivatizing agents used. The detection limits of 3 ng mL^?1 for cis- and trans-Cl₂CA, 2 ng mL^?1 for cis-Br₂CA, 6 ng mL^?1 for 4-F-3-PBA, and 0.6 ng mL^?1 for 3-PBA and 2-PBA. The method showed good linearity (R ² = 0.973?0.998), repeatability from 4.0 to 13 % (n = 5), recovery from 79.2 to 95.7 %, and enrichment factors ranged between 109 and 159 for target analytes spiked in water samples. The proposed method and conventional methods were compared. Results suggested that the proposed HF-LPME-ISD/GC-ECD method was a rapid, simple, inexpensive, and eco-friendly technique for the analysis of metabolites of pyrethroids.     

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.