Hollow Fiber Liquid-phase Microextraction Research Articles

Optimization of hollow-fiber liquid phase microextraction for polychlorinated biphenyls in human breast milk.

A reliable and sensitive analytical approach has been optimized for the extraction of seven polychlorinated biphenyls (PCBs) from human breast milk. Hollow fiber liquid phase microextraction (HF-LPME) was applied for the first time for the extraction and pre-concentration of the analytes. Analytes were separated by gas chromatography with electron capture detector (GC-μECD) for the sensitive detection and mass spectrometry for the unequivocal identification. A rotable central composite design (RCCD) was performed for the multivariate optimization of the method. The best results were obtained at 40°C during 30min and 600rpm of stirring speed using a hollow fiber length of 5cm and toluene as an extractant phase and salt addition was not required. The detection limits were in the range 7-14ng L-1 for PCBs. The coefficients of determination of the calibration curves indicated good linearity (R2> 0.96) and the enrichment factors ranged from 74 to 143. This type of study is of great importance due to the deleterious effect that the presence of contaminants can produce in infants health related to the immature character of the defense system. Moreover, exclusive breastfeeding is recommended by neonatologists up to six months of life and as complementary food during the first two years.

Zeolitic imidazolate framework-8 reinforced hollow-fiber liquid-phase microextraction of free urinary biomarkers of whole grain intake followed by CE analysis.

The whole grain intake is closely associated with human health. In this work, three-phase dynamic hollow-fiber liquid-phase microextraction reinforced with 0.10mg/mL 30nm zeolitic imidazolate framework-8 nanoparticles was introduced for purification and enrichment of free urinary metabolite biomarkers of whole grain intake. Eightmilliliters of HCl (pH 3.00) and 8 μL of 300mM NaOH solutions were used as the donor and acceptor phases, respectively. The temperature and stirring rate were kept at 25℃ and 500rpm, and the extraction time was 40min. The extraction process required no further desorption, and the resultant extract was directly used for electrophoretic analysis without derivatization. Based on the synergistic effect of hollow-fiber liquid-phase microextraction and the electrophoretic stacking, the enrichment factors of 3,5-dihydroxybenzoic acid and 3-(3,5-dihydroxyphenyl)-1-propionic acid reached 1018-1034 times, and their limits of detection achieved 0.33-0.67ng/mL (S/N=3) in urine matrix. The developed method has been successfully used for urine analysis, and the sample recovery data were in the range of 97.0-103.5%. This developed method provided an attractive alternative for the determination of urinary metabolite biomarkers of whole grain intake due to its sensitive, fast, low-cost, and environmental-friendly features.

Liquid-phase microextraction of polycyclic aromatic hydrocarbons: A review

Abstract Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds comprised of two or more fused benzene rings, which arise from the incomplete combustion of organic materials. These compounds have been of concern as carcinogens and mutagens for the past 50-60 years. Lately, they are also receiving attention as endocrine-disrupting chemicals. Therefore, proper analytical methods are required for sampling and analyzing these compounds. In response to problems associated with the conventional methods like solid-phase extraction (SPE) and liquid-liquid extraction (LLE), many studies have focused on the miniaturization of different sample preparation techniques. In this regard, the use of different types of liquid phase microextraction (LPME) techniques has increased significantly during the recent few decades. LPME techniques are advantageous because they use single-step sample preparation and have shown a greater sensitivity, selectivity, and efficiency than the conventional methods. In addition, these techniques have good potential for automation, to reduce the time and cost of analysis. This review focuses on the most important configurations of LPME including single‐drop microextraction (SDME), hollow-fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) techniques used for the sampling and determination of PAHs in different samples, along with their cons and pros, as well as their prospects.

Three-phase hollow fiber liquid-phase microextraction combined with HPLC for determination of three trace acidic plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl.

The analysis of plant growth regulators presents a challenge due to their trace quantities and complex matrices. A novel, simple, and effective analytical method for the determination of three trace acidic plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl was developed to address this issue. Three-phase hollow fiber liquid-phase microextraction combined with high-performance liquid chromatography was applied for the enrichment, purification, and determination of three acidic plant growth regulators, namely, indole-3-acetic-acid, indole-3-butyric-acid, and (+)-abscisic acid. The factors affecting extraction performance, including extractant species, pH of donor and acceptor phases, salt addition dosage, extraction time, temperature, and stirring rate, were investigated and optimized. Under optimum conditions, the proposed method provided good linearity (R2 , 0.9994-0.9999), low limit of detection (0.038-0.12ng/mL), and acceptable relative recoveries (56.7-117.6%). The enrichment factors were between 153 and 328. The developed method was successfully applied to the enrichment and determination of plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl and exhibited increased purification capacity, higher sensitivity, and decreased organic solvent consumption compared with conventional sample preparation methods. This method may provide atesting platform for the monitoring of plant growth regulator residues, ensuring the safe and effective use of traditional Chinese medicine.

Analysis of basic drugs in biological samples using dynamic single-interface hollow fiber liquid-phase microextraction combined with fast electromembrane extraction

In this study, a combination of single-interface hollow fiber liquid-phase microextraction and electromembrane extraction was applied for the extraction of some basic drugs from biological samples. The extraction process was followed by the HPLC-UV instrument. In this dynamic system, 1-octanol was impregnated into the pores of hollow fiber wall as an acceptor phase, the sample solution (pH = 12.0) was pumped into the lumen of hollow fiber by a syringe pump, the extraction efficiency was improved by filling and emptying (25 times) of sample solution (step-1). The extracted analytes in the organic acceptor phase were back-extracted by a fast electromembrane extraction procedure (step-2). Effective parameters on the extraction efficiency of both methods were investigated and optimized. Under optimized conditions (organic acceptor phase: 1-octanol, sample solution volume: 1500 µL, flow rate: 2.0 mL min−1, the number of filling and emptying cycles: 25, voltage: 100 V, back-extraction time: 2 min, and aqueous acceptor phase: 100 mM HCl), the proposed method provided good linearity with determination coefficients ranging from 0.992 to 0.996 over a concentration range of 2.5–1000 ng mL−1. Extraction recoveries were obtained in the range of 65.1 and 88.8%, which resulted in preconcentration factors in the range of 32.6–44.4. The limits of detection were found to be within the range of 0.12–0.36 ng mL−1, while the corresponding repeatability ranged from 3.7 to 9.3% (n = 3). Finally, the optimized method was applied for the quantification of propranolol, diltiazem and, lidocaine in urine and, plasma samples with relative recoveries ranged between 94.1 and 105.4%, indicating the reliability of the method.

Reverse Micelle Hollow Fiber Liquid-Phase Microextraction Coupled with HPLC for the Determination of Q-Markers of Anthraquinones in Rhubarb and Their Plasma Protein Binding Rates

A three-phase hollow fiber liquid-phase microextraction based on reversed micellar supramolecule was developed and employed for the determination of quality markers of three anthraquinones in Rhubarb and their plasma protein binding rates. Moreover, the extraction mechanism of reversed micellar supramolecule and determination mechanism of plasma protein binding rate by the proposed method are both explored. In this procedure, n-nonanol was impregnated in the wall pores and reverse micelle of tetrabutylammonium chloride/n-nonanol filled in lumen of hollow fibers, which were covered with a thin salt film and used for the microextraction of target compounds prior to HPLC analysis. Important extraction parameters including extraction solvent type, reversed micellar supramolecule type and concentration, sample phase pH, salt concentration, stirring rate, extraction time, and binding time between active compound and plasma protein were investigated. Under the optimized conditions, limits of detection were 0.1–0.4 ng/mL with enrichment factors in the range of 54.2–100.7. The linearities were 0.5–500 ng/mL with r2 ≥ 0.9838. Satisfactory accuracies (relative recoveries 95.7–98.3%) were also obtained. The average plasma protein binding rates of rhein, chrysophenol, and physcion were 96.7%, 41.8%, and 46.7%, respectively. The results showed that the proposed procedure can not only extract and concentrate anthraquinones in Rhubarb, but also determine their plasma protein binding rates.

Effervescence-assisted spiral hollow-fibre liquid-phase microextraction of trihalomethanes, halonitromethanes, haloacetonitriles, and haloketones in drinking water

A new analytical method was optimized to determine 18 disinfection by-products (DBPs) in drinking water, including four different chemical groups. For this purpose, spiral-shaped hollow-fibre liquid phase microextraction with 1-octanol as the acceptor solvent assisted by effervescence was applied using a homemade supporting device that was specifically designed for this application. The device was printed in a 3D printer and allows for an increased fibre surface even with a low sample volume, which significantly facilitates the extraction. The samples were analysed by gas chromatography coupled to both an electron capture detector and a mass spectrometer for the quantification and unequivocal identification of the analytes, respectively. Effervescence was generated using citric acid and bicarbonate at a molar ratio 1:2, which significantly improves the extraction efficiency and reduces mechanical operations, since stirring and modifiers are not required. The results showed enrichment factors ranging from 13.1 to 140.1. Satisfactory recoveries (80-113 %) were obtained, with relative standard deviations from 3 to 15 % and good linearity. The detection limits (ng L-1) ranged from 10 to 35 (trihalomethanes), 12 to 220 (halonitromethanes), 17 to 79 (haloacetonitriles) and 10 to 16 (haloketones). The applicability of the method was assessed in 6 local water distribution systems.

Hollow Fiber Liquid-Phase Microextraction At-Line Coupled to Capillary Electrophoresis for Direct Analysis of Human Body Fluids.

A simple and cheap all-in-one concept for at-line coupling of hollow fiber liquid-phase microextraction (HF-LPME) to commercial capillary electrophoresis (CE) is demonstrated, which enables the direct analysis of complex samples. A disposable microextraction device compatible with injection systems of Agilent CE instruments is proposed, which consists of a short segment of a porous HF attached to a tapered polypropylene holder. The holder maintains a constant position of the HF in a CE vial during extraction and simultaneously guides the injection end of a separation capillary into the HF lumen for automated CE injection and analysis. In a typical analytical procedure, the HF is impregnated with a water-immiscible solvent, its lumen is filled with 5 μL of an aqueous acceptor solution, and the microextraction device is placed in a 2 mL glass CE vial containing 550 μL of a donor solution. The vial is agitated at 750 rpm for 10 min, and the resulting acceptor solution is injected directly from the HF lumen into the commercial CE. No additional manual handling is required, except for the transfer of the CE vial to the CE autosampler. Multiple complex samples can be simultaneously pretreated in a multiple-well plate format, thus significantly reducing the total analysis time. Suitability of the analytical method is demonstrated by the direct determination of model basic drugs (nortriptyline, haloperidol, loperamide, and papaverine) in physiological solutions, urine, and dried blood spot (DBS) samples. Repeatability of the method is better than 12.8% (%RSD), extraction recoveries range between 34 and 76%, and enrichment factors are 37-84. The method is linear in a range of 2 orders of magnitude (R2 ≥ 0.9977) with limits of detection of 0.7-1.55 μg/L. The method has a high potential for the direct analysis of DBS samples since DBS elution and HF-LPME are performed simultaneously during the 10 min agitation. The manual DBS handling is thus reduced to inserting the DBS punch into the CE vial only. Moreover, the universal character of the HF-LPME might extend the applicability of the method to a wide range of analytes/matrices, and combination with other commercial detectors might improve the selectivity/sensitivity of the CE analysis.

Hollow fiber liquid phase microextraction combined with total reflection X-ray fluorescence spectrometry for the determination of trace level inorganic arsenic species in waters

In the present study, we investigated the possibilities and drawbacks of hollow fiber liquid phase microextraction (HF-LPME) combined with total reflection X-ray fluorescence (TXRF) spectrometry for the determination of low amounts of inorganic arsenic (As) species in water samples. The obtained results showed that a three-phase HF-LPME system was more suitable to be used in combination with TXRF than the two phase configuration, since lower detection limit and better precision for As determination can be attained. Relevant experimental parameters affecting As extraction (i.e. types of extractant, organic solvent, agitation speed, pH and extraction time) and TXRF analysis (deposition volume and drying mode) were systematically evaluated. It was found that As(III) was more efficiently extracted at pH 13, whereas, optimum pH for As(V) extraction was at pH 8.5. Limits of detection (LOD) achieved using the best analytical conditions meet the requirements of current legislation and allow the determination of inorganic As(V) and As(III) in water. The proposed method was also applied to different spiked environmental water samples for the preconcentration and subsequent determination of trace inorganic As species.

Hollow fiber–liquid phase microextraction method based on a new deep eutectic solvent for extraction and derivatization of some phenolic compounds in beverage samples packed in plastics

The present study describes a sensitive, efficient, and easy approach for isolation, enrichment, and derivatization some phenolic compounds in the beverage samples packed in plastic bottles. The sample preparation method is based on a hollow fiber–liquid phase microextraction technique using a deep eutectic solvent. The enriched analytes are determined by gas chromatography–mass spectrometry. For this purpose, a new deep eutectic solvent composed of 8–hydroxyquinoline and pivalic acid is synthesized and used as an extraction solvent. The solvent is mixed with chloroacetyl chloride as a derivatization agent and filled into a hollow fiber segment containing an iron wire within the lumen. The prepared stir bar (hollow fiber) is stirred into the sample solution in which sodium chloride is dissolved to increase ionic strength of the solution. Temperature of the solution is adjusted at 50 °C to improve efficiency of the extraction/derivatization procedure. Under optimum conditions, the introduced method indicated high enhancement (1652–3265) and enrichment (1085–1256) factors, low limits of detection (9–22 ng L−1) and quantification (29–76 ng L−1), good linearity (r2 ≥ 0.9950), and satisfactory repeatabilities. Finally, the proposed method was applied in analysis of the analytes in the various beverage samples packed in plastic packages.

Combining graphite with hollow-fiber liquid-phase microextraction for improving the extraction efficiency of relatively polar organic compounds

In this study, we have developed a simple and effective hybrid extraction method based on the incorporation of raw carbon nanosorbents and octanol in the pores of a hollow-fiber membrane for improving the extraction efficiency of relatively polar organic compounds. Trihalomethanes (THMs) were used as model analytes. Three types of carbon nanosorbents (graphite, graphene, and multi-walled carbon nanotubes) were studied. The carbon sorbent incorporating membrane was used in a two-phase mode liquid-phase microextraction, with 1-octanol as the acceptor solution. Using a graphite-reinforced hollow-fiber membrane and an extraction time of 10 min, enrichment factors of 40–71 were obtained for trichloromethane, bromodichloromethane, bromoform, and chlorodibromomethane. Linear working ranges of 0.2–100 μg L−1 and limits of detection ranging from 0.01 μg L−1 (for CHCl2Br and CHClBr2) to 0.1 μg L−1 (for CHCl3) were achieved. The minimum detectable concentrations were far below the maximum concentration levels (60–200 μg L−1) set by the WHO for drinking water. The carbon-sorbent-reinforced hollow-fiber liquid-phase microextraction afforded higher extraction efficiency and shorter extraction time compared with conventional hollow-fiber liquid-phase microextraction. Finally, the method was applied to the analysis of real water samples, such as drinking water, tap water, and swimming pool water samples.

Deep eutectic solvent-based hollow fiber liquid-phase microextraction for quantification of Q-markers of cinnamic acid derivatives in traditional Chinese medicines and research of their plasma protein binding rates

A deep eutectic solvent-based hollow fiber liquid-phase microextraction was proposed and coupled with high performance liquid chromatography-ultraviolet detection for the quantification of four cinnamic acid derivatives (caffeic acid, p-hydroxycinnamic acid, ferulic acid, cinnamic acid) in traditional Chinese medicines and research of their plasma protein binding rates. Also, the extraction mechanism of target analytes and the determination mechanism of their plasma protein binding rate by the procedure are both explored and illustrated. In this study, the variables affecting the experiment procedure, including the type and composition of deep eutectic solvent, sample phase pH, salt amount, extraction temperature, stirring rate, extraction time, and incubation time of active compound in plasma (i.e., binding equilibrium time between active compound and plasma protein) were investigated and optimized. Under the optimum conditions, enrichment factors of 82.4, 105.9, 88.8, 127.1 for caffeic acid, p-hydroxycinnamic acid, ferulic acid and cinnamic acid, satisfactory linear ranges (r2 ≥ 0.9985), low detection limits (0.1–0.3 ng/mL), acceptable precisions with relative standard deviations (0.7%–6.1%) and recoveries (between 86.7% and 110.5%) were obtained. The feasibility of the proposed method was evaluated by the determination of four analytes in Chinese medicinal samples and research of their plasma protein binding rates. The results indicated that the developed method is eco-friendly, easy-to-handle, and has the major advantages of high-preconcentration factor and remarkable clean-up ability.

Central Composite Design for Optimizing Hollow Fiber Liquid Phase Microextraction of Carbamazepine from Aqueous and Biological Samples

A simple, sensitive and efficient method based on hollow fiber liquid phase microextraction followed by high performance liquid chromatography has been developed for preconcentration and determination of trace carbamazepine, an antiepileptic drug, in aqueous and biological solutions.The main parameters affecting the extraction efficiency were studied using response surface methodology. Central composite design was performed at five levels of extraction time, pH and ionic strength. The final model showed good linearity and performance. The optimal conditions were observed at 48.5 min, 8.9 and 0.29 M for extraction time, pH and ionic strength, respectively. The calibration curve was linear in the range of 5–500 µg/L with correlation coefficient of 0.9999 and limit of detection of 2.8 µg/L. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drug in aqueous and plasma samples. The intra- and inter-day coefficients of variation were less than 4.7 for all real samples.

Hollow-fibre liquid-phase microextraction and gas chromatography-mass spectrometric determination of amphetamines in whole blood

Here, we present a fully validated method using a hollow-fibre liquid-phase microextraction technique for the determination by gas chromatography-mass spectrometry (GC–MS) of amphetamine (AMP), methamphetamine (MET), fenproporex (FEN), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyethylamphetamine (MDEA) in whole blood. The validation parameters presented successful values within those recommended by the Scientific Working Group for Forensic Toxicology (SWGTox) in the Standard Practices for Method Validation in Forensic Toxicology. The limits of detection ranged from 1 to 3 ng/mL, and the limits of quantification ranged from 2 to 5 ng/mL. The determination coefficients (r2) ranged from 0.990 to 0.997, and the method presented good intraday and interday accuracy (from 90.4% to 97.2%) and satisfactory recovery (from 68% to 110%). No carryover was observed. The heteroscedasticity was tested, and only AMP presented homoscedasticity. Weighting factors were applied to correct the linearity of MET (1/x2), MDA (1/x), FEN (1/x1/2), MDMA (1/x2) and MDEA (1/y). Dilution integrity was tested at ratios of 1:2, 1:5 and 1:10, and all maintained intraday precision (from 94.9% to 99.3%) and interday precision (from 89.4% to 94.9%). The validated method was applied to six real whole blood samples from individuals suspected of consuming ecstasy, and MDMA, MDA and amphetamine were successfully identified and quantified.

Salt-effect enhanced hollow-fiber liquid-phase microextraction of glutathione in human saliva followed by miniaturized capillary electrophoresis with amperometric detection.

A hollow-fiber liquid-phase microextraction (HF-LPME) method was established for purification and enrichment of glutathione (GSH) in human saliva followed by a miniaturized capillary electrophoresis with amperometric detection system (mini-CE-AD). Based on regulating isoelectric point and increasing salt effect to modify donor phase, HF-LPME could provide high enrichment efficiency for GSH up to 471 times, and the extract was directly injected for mini-CE-AD analysis. The salt-effect enhanced HF-LPME/mini-CE-AD method has been successfully applied to saliva analysis, and acceptable LOD (0.46ng/mL, S/N = 3) and recoveries (92.7-101.3%) could be obtained in saliva matrix. The sample pretreatment of this developed method was simple and required no derivatization, providing a potential alternative for non-invasive fluid analysis using portable instrument.

Aflatoxins’ Clean-Up in Food Samples by Graphene Oxide–Polyvinyl Poly Pyrrolidone—Hollow Fiber Solid-Phase Microextraction

The present investigation reports the synthesis of graphene oxide–polyvinyl poly pyrrolidone composite and its application in the extraction of aflatoxins in food samples. This composite was successfully synthesized and characterized with analytical instruments such as UV–Vis, FITR, XRD, and SEM techniques. The extraction was carried out by reinforced hollow fiber liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC). Various parameters that affect the productivity of the present technique were exhaustively explored, and the quantifications were carried out under the optimized states. The limits of detection (LODs) were found to be 0.33, 0.10, 0.37, and 0.10 ng g−1, and limits of quantification (LOQs) were 1.10, 0.33, 1.24, and 0.33 ng g−1, respectively, for aflatoxins B1, B2, G1, and G2. The accuracy of the present method was determined based on the relative recovery (RR%) of the aflatoxins and the RR% of aflatoxins B1, B2, G1, and G2 which were found to be quite good (between 60.20 and 108.20 for 1 ng g−1 and between 62.02 and 95.39 for 5 ng g−1) in food samples. Applicability of the sorbent for the separation and quantification of the above-mentioned aflatoxins from food samples were examined. The developed method is straightforward, reliable, and effective, and has been successfully applied in determination of aflatoxins from food samples.

Hollow fiber-based liquid-phase microextraction and HPLC-UV determination of lovastatin in biological fluids

In this study, a hollow fiber liquid-phase microextraction (HF-LPME) method coupled with high-performance liquid chromatography (HPLC) was successfully developed for the determination of trace levels of lovastatin in urine and plasma samples. Lovastatin was extracted from 15 mL of the acidic sample solution with a pH of 2 into an organic extracting solvent (n-octanol) impregnated in the pores of a hollow fiber and then back extracted into an acidified aqueous solution in the lumen of the hollow fiber. After extraction, 10 µL of the acceptor phase was injected into HPLC system. To obtain high extraction efficiency, the parameters affecting the HF-LPME, including pH of the sample and extractant phases, type of organic phase, ionic strength, stirring rate, extraction time, and temperature, were studied and optimized. Under the optimized conditions (solvent 1-octanol, pH = 2, 45 min stirring at 45°C with 750rpm), the relative recovery percentage was 85.2–97, which shows the capability of the method to analyze the analyte concentration. This technique provided preconcentration factor 199, 185, and 170 for water, urine, and plasma, respectively. Good precisions values (with relative standard division ≤ 10.5%) were obtained. The results indicated that the HF-LPME method has an excellent cleanup capacity and a high preconcentration factor and could serve as a simple and sensitive method for monitoring the drug in biological samples.

Recent advances and trends in miniaturized sample preparation techniques.

Advances in the area of sample preparation are significant and have been growing significantly in recent years. This initial step of the analysis is essential and must be carried out properly, consisting of a complicated procedure with multiple stages. Consequently, it corresponds to a potential source of errors and will determine, at the end of the process, either a satisfactory result or a fail. One of the advances in this field includes the miniaturization of extraction techniques based on the conventional sample preparation procedures such as liquid-liquid extraction and solid-phase extraction. These modern techniques have gained prominence in the face of traditional methods since they minimize the consumption of organic solvents and the sample volume. As another feature, it is possible to reuse the sorbents, and its coupling to chromatographic systems might be automated. The review will emphasize the main techniques based on liquid-phase microextraction, as well as those based upon the use of sorbents. The first group includes currently popular techniques such as single drop microextraction, hollow fiber liquid-phase microextraction, and dispersive liquid-liquid microextraction. In the second group, solid-phase microextraction techniques such as in-tube solid-phase microextraction, stir bar sorptive extraction, dispersive solid-phase extraction, dispersive micro solid-phase microextraction, and microextraction by packed sorbent are highlighted. These approaches, in common, aim the determination of analytes at low concentrations in complex matrices. This article describes some characteristics, recent advances, and trends on miniaturized sample preparation techniques, as well as their current applications in food, environmental, and bioanalysis fields.

Modern Approaches to Preparation of Body Fluids for Determination of Bioactive Compounds

The current clinical and forensic toxicological analysis of body fluids requires a modern approach to sample preparation characterized by high selectivity and enrichment capability, suitability for micro-samples, simplicity and speed, and the possibility of automation and miniaturization, as well as the use of small amounts of reagents, especially toxic solvents. Most of the abovementioned features may be realized using so-called microextraction techniques which cover liquid-phase techniques (e.g., single-drop microextraction, SDME; dispersive liquid–liquid microextraction, DLLME; hollow-fiber liquid-phase microextraction, HF-LPME) and solid-phase extraction techniques (solid-phase microextraction, SPME; microextraction in packed syringes, MEPS; disposable pipette tip extraction, DPX; stir bar sorption extraction, SBSE). Some other extraction methodologies like dispersive solid-phase extraction (d-SPE) or magnetic solid-phase extraction (MSPE) can also be easily miniaturized. This review briefly describes and characterizes the abovementioned extraction methods, and then presents their current applications to the preparation of body fluids analyzed for bioactive compounds in combination with appropriate analytical methods, mainly chromatographic and related techniques. The perspectives of the analytical area we are interested in are also indicated.

Determination of ring-substituted amphetamines through automated online hollow fiber liquid-phase microextraction-liquid chromatography

The present paper describes an original method for the online preconcentration and analysis of ring-substituted amphetamines in urine samples, used on the integration of robot-assisted hollow fiber liquid-phase microextraction (HF-LPME), high-performance liquid chromatography (HPLC), and fluorescence detection (FLD). A lab-made autosampler, actuating a 100-μL syringe and equipped with a three-way solenoid microvalve, allowed the acceptor phase to flow through and be withdrawn from the lumen fiber, enabling the automated online transference of the enriched acceptor phase for chromatographic analysis, through a six-port switching valve. The developed online HF-LPME-LC/FLD method demonstrated high analytical throughput and confidence, facilitating the efficient extraction and determination of the target analytes, with minimal solvent consumption and sample manipulation, in a straightforward way. Sample cleanup, analyte uptake, and analysis were carried out in 14.5 min. Under optimal conditions, automated online HF-LPME showed excellent linearity, precision, and trueness, obtaining intraday RSDs between 2.9 and 9.2% (n = 6) and interday RSDs between 5.3 and 9.3% (n = 6). Enrichment factors (EFs) ranged between 14.2 and 15.7, extraction recoveries (ERs) ranged between 17.7 and 19.5%, and the limits of detection (S/N = 3) were 2.0, 3.0, and 3.0 μg L-1 for MDA, MDMA, and MDEA, respectively. The method proved to be an effortless, rapid, reliable, and environment-friendly approach for the determination of drug abuse in urine samples. Graphical abstract.