Liquid-phase microextraction of aromatic amines: hollow fiber-liquid-phase microextraction and parallel artificial liquid membrane extraction comparison.

Aromatic amines (AA) are carcinogenic compounds that can enter the human body through many sources, one of the most important being tobacco smoke. They are excreted with the urine, from which they can be extracted and measured. To that end, hollow fiber-liquid-phase microextraction (HF-LPME) and parallel artificial liquid membrane extraction (PALME) were optimized for the analysis of representative aromatic amines, as alternatives to liquid-liquid extraction (LLE). Relevant extraction parameters, namely organic solvent, extraction time, agitation speed, and acceptor solution pH, were studied, and the two optimized techniques-HF-LPME: dihexyl ether, 45 min, 250 rpm, and pH 1; PALME: undecane, 20 min, 250 rpm and pH 1-were compared. Comparison of the optimized methods showed that significantly higher recoveries could be obtained with PALME than with HF-LPME. Therefore, PALME was further validated. The results were successful for nine different AA, with regression coefficients (R2) of at least 0.991, limits of detection (LOD) of 45-75 ng/L, and repeatability and peak area relative standard deviations (RSD) below 20%. Furthermore, two urine samples from smokers were measured as proof of concept, and 2-methylaniline was successfully quantified in one of them. These results show that PALME is a great green alternative to LLE. Not only does it use much smaller volumes of toxic organic solvents, and sample-enabling the study of samples with limited available volumes-but it is also less time consuming and labor intensive, and it can be automated.

Photocatalytic degradation of bisphenol-A (BPA) over titanium dioxide, and determination of its by-products by HF-LPME/GC-MS.

In this work, analytical strategies were developed based on the technique of hollow fiber liquid-phase microextraction and chromatographic methods (LC-UV and GC/MS). These methods allowed the identification of the main Bisphenol-A by-products applying heterogeneous photocatalysis in water samples. BPA degradation in this study was in the order of 90%, and the conditions used in the HF-LPME were optimized through 23 factorial design (6 cm fiber length, stirring speed of 750 rpm, and an extraction time of 30 min). Using a HF-LPME/GC-MS analytical strategy, it was possible to identify six by-products of BPA photodegradation, two of which have not been reported in the literature so far. This knowledge was quite important since the degradation can lead to the formation of more toxic and persistent by-products than the BPA. With the Toxtree software, three degradation products were found to be persistent to the environment, in addition to BPA; however, in 360 minutes of reaction, chromatographic peaks of the precursors were not identified, suggesting that there may have been a total degradation of these compounds. The results showed a great application potential of a miniaturized extraction technique to extract and pre-concentrate the degradation products of emerging contaminants.

Two-phase and three-phase liquid-phase microextraction of hydrochlorothiazide and triamterene in urine samples.

This paper reports the applicability of two-phase and three-phase hollow fiber based liquid-phase microextraction (HF-LPME) for the extraction of hydrochlorothiazide (HYD) and triamterene (TRM) from human urine. The HYD in two-phase HF-LPME is extracted from 24 mL of the aqueous sample into an organic phase with microliter volume located inside the pores and lumen of a polypropylene hollow fiber as acceptor phase, but the TRM in three-phase HF-LPME is extracted from aqueous donor phase to organic phase and then back-extracted to the aqueous acceptor phase, which can be directly injected into HPLC for analysis. Under optimized conditions preconcentration factors of HYD and TRM were obtained as 128 and 239, respectively. The calibration curves were linear (R(2) ≥ 0.995) in the concentration range of 1.0-100 µg/L for HYD and 2.0-100 µg/L for TRM. The limits of detection for HYD and TRM were 0.5 µg/L. The intra-day and inter-day RSD based on four replicates were obtained as ≤5.8 and ≤9.3%, respectively. The methods were successfully applied for determining the concentration of the drugs in urine samples. Copyright © 2015 John Wiley & Sons, Ltd.

Hollow-fiber liquid phase microextraction for determination of fluoxetine in human serum by nano-liquid chromatography coupled to high resolution mass spectrometry.

Therapeutic drug monitoring (TDM) is a personalized care tool based on the determination of a target drug concentration in human serum. An antidepressant drug of interest for such investigations is fluoxetine (FXT), due to a severe impact of genetic polymorphisms on its metabolism. A bioanalytical method employed for TDM purposes must exhibit satisfactory selectivity and detectability, which becomes more difficult due to highly complex biological matrices. In this study, a highly selective bioanalytical method for the determination of FXT in human serum is proposed, which provides excellent clean-up efficiency based on a low cost hollow fiber liquid-phase microextraction (HF-LPME) sample preparation step and nano-liquid chromatography coupled to high-resolution mass spectrometry (nano-LC-HRMS). HF-LPME was performed using a two-phase "U" configuration, with 6 cm fiber, 20 µL of 1-octanol acting as supported liquid membrane, and ammonium hydroxide (pH 10) as the donor phase with NaCl (10 % m/v) and methanol (5 % v/v) as additives, requiring only 250 µL of the sample. The procedure was conducted for 30 min under a 750 rpm stirring rate. Gradient elution was carried out employing an acetonitrile-water as mobile phase, the composition of 30:70 to 100:00 (v/v) for 15 min, using formic acid 0.1 % (v/v) as an additive. MS1 was acquired in an Orbitrap mass analyzer, while MS2 was acquired in a linear trap quadrupole. Satisfactory linearity (Pearson's r = 0.99709) was obtained for a concentration range of 0.02 to 2.5 µg mL-1, which is compatible with the therapeutic and toxic range for FXT. The developed method presents adequate precision (1.61 to 7.45 %) and accuracy (95 to 114 %) and allows the dilution of high concentration samples in a 1:4 ratio (v/v), enabling its application for forensic serum samples. To our knowledge, this is the first study reporting a method based on HF-LPME and nano-LC-HRMS with any analytical purpose, especially with a TDM focus.

[Rapid determination of nine preservatives in tobacco flavor by three phase-hollow fiber-liquid phase microextraction-high performance liquid chromatography].

Tobacco flavors are extensively utilized in traditional tobacco products, electronic nicotine, heated tobacco products, and snuff. To inhibit fungal growth arising from high moisture content, preservatives such as benzoic acid (BA), sorbic acid (SA), and parabens are often incorporated into tobacco flavors. Nonetheless, consuming preservatives beyond safety thresholds may pose health risks. Therefore, analytical determination of these preservatives is crucial for both quality assurance and consumer protection. For example, BA and SA can induce adverse reactions in susceptible individuals, including asthma, urticaria, metabolic acidosis, and convulsions. Parabens, because of their endocrine activity, are classified as endocrine-disrupting chemicals. Despite extensive research, the concurrent quantification of trace-level hydrophilic (BA and SA) and hydrophobic (methylparaben, ethylparaben, isopropylparaben, propylparaben, butylparaben, isobutylparaben, and benzylparaben) preservatives in tobacco flavors remains challenging. Traditional liquid phase extraction coupled with high performance liquid chromatography (HPLC) often results in high false positive rates and inadequate sensitivity. In contrast, tandem mass spectrometry offers high sensitivity and specificity; however, its widespread application is limited by laborious sample preparation and significant operational costs. Therefore, it is crucial to establish a fast and sensitive sample pretreatment and analysis method for the nine preservatives in tobacco flavors. In this study, a method for the simultaneous determination of the nine preservatives (SA, BA and seven parabens) in tobacco flavor was established based on three phase-hollow fiber-liquid phase microextraction (3P-HF-LPME) technology combined with HPLC. To obtain the optimal pretreatment conditions, extraction solvent type, sample phase pH, acceptor phase pH, sample phase volume, extraction time, and mass fraction of sodium chloride, were examined. Additionally, the HPLC parameters, including UV detection wavelength and mobile phase composition, were refined. The optimal extraction conditions were as follows: dihexyl ether was used as extraction solvent, 15 mL sample solution (pH 4) was used as sample phase, sodium hydroxide aqueous solution (pH 12) was used as acceptor phase, and the extraction was carried out at 800 r/min for 30 min. Chromatographic separation was accomplished using an Agilent Poroshell 120 EC-C18 column (100 mm×3 mm, 2.7 µm) and a mobile phase comprising methanol, 0.02 mol/L ammonium acetate aqueous solution (containing 0.5% acetic acid), and acetonitrile for gradient elution. Under the optimized conditions, the nine target analytes showed good linear relationships in their respective linear ranges, the correlation coefficients (r) were ≥0.9967, limits of detection (LODs) and quantification (LOQs) were 0.02-0.07 mg/kg and 0.08-0.24 mg/kg, respectively. Under two spiked levels, the enrichment factors (EFs) and extraction recoveries (ERs) of the nine target analytes were 30.6-91.1 and 6.1%-18.2%, respectively. The recoveries of the nine target analytes ranged from 82.2% to 115.7% and the relative standard deviations (RSDs) (n=5) were less than 14.5% at low, medium and high levels. The developed method is straightforward, precise, sensitive, and well-suited for the rapid screening of preservatives in tobacco flavor samples.

[Determination of three plant growth regulators in Dendrobium officinale and Anoectochilus roxburghii by three-phase hollow fiber liquid phase microextraction- high performance liquid chromatography].

Dendrobium officinale (D. officinale) and Anoectochilus roxburghii (A. roxburghii) are precious raw materials for traditional Chinese medicine. The growing demand for D. officinale and A. roxburghii cannot be met by current production techniques. Hence, the widespread artificial cultivation of D. officinale and A. roxburghii using substantial amounts of plant growth regulators (PGRs) has emerged. The excessive use of PGRs not only affects the quality and efficacy of medicinal materials but also causes a series of safety issues. Therefore, expanding research on residual PGRs in valuable Chinese medicinal materials is important to avoid the health hazards caused by these substances. Unfortunately, the identification of PGRs is challenging because of their trace and complex matrices. High performance liquid chromatography (HPLC) has become one of the mainstream analytical methods for PGR determination. An important consideration in the application of this technique to the detection of trace acidic PGRs is how to improve its accuracy and sensitivity. Three-phase hollow fiber liquid phase microextraction (3P-HF-LPME) has the advantages of a high enrichment factor, complex sample purification ability, low reagent consumption, low cost, and easy integration with chromatographic systems. Thus, the 3P-HF-LPME method overcomes the many shortcomings of traditional sample pretreatment methods. In this study, a novel, simple, and effective analytical method based on 3P-HF-LPME combined with HPLC was developed to extract, purify, enrich, and detect three trace acidic PGRs (indole-3-acetic acid, naphthyl acetic acid and indolebutyric acid) in D. officinale and A. roxburghii. The chromatographic separation conditions and 3P-HF-LPME model parameters were systematically optimized for this purpose. First, the sample solution was prepared by ultrasonication and low-temperature standing, and then adjusted to pH 3.0 using dilute hydrochloric acid. The sample solution (10 mL) and NaCl (1.50 g) were stored in a 15 mL brown extraction bottle with a built-in magnetic stirrer. Next, 30 µL of NaOH solution (pH 11.0) as the inner phase solution was injected into the inner cavity of a hollow fiber tube, which was subsequently sealed at both ends. The hollow fiber tube was soaked in n-octanol for 5 min and dried naturally to remove excess extraction solvent from its surface. Finally, the fiber tube was placed in a brown extraction bottle and stirred using a thermostatic magnetic stirrer at 40 ℃ and 1600 r/min for 2 h. After extraction, the three target analytes were separated on a Welch Ultimate XB-C18 column (250 mm×4.6 mm, 5 µm) under isocratic elution conditions using acetic acid aqueous solution and methanol (45∶55, v/v) as the eluent. The results indicated that the three PGRs showed good linearity in the range of 0.5-100.0 µg/L (coefficients of determination (r2)=0.9999), with limits of detection (LODs) of 0.02-0.15 µg/L. The method recoveries were 88.5-102.2%, with relative standard deviations (RSDs) of less than 3.7% (n=3). The extraction efficiencies and enrichment factors of the three PGRs in 15 batches of fresh D. officinale and A. roxburghii products were found to be 42.0%-86.8% and 140-289. Full-scan mass spectrometry was used to further identify positive samples to avoid false-positive results and enhance the reliability of the experimental method. In summary, the proposed method is sensitive, accurate, reliable, environment friendly, and capable of high enrichment. It could be used to determine the residues of three acidic PGRs in D. officinale and A. roxburghii. Moreover, it can provide technical support for the residue detection of PGRs in other Chinese medicinal materials.

Application of an improved hollow fiber liquid phase microextraction technique coupled to LC-MS/MS to studying migration of fluorescent whitening agents from plastic food contact materials.

In this paper, a new hollow fiber liquid-phase microextraction method was developed to improve the extraction of five fluorescent whitening agents that migrated from plastics food contact materials. Influencing factors, such as the types of membrane, the extraction solvent, the stirring speed, the addition of salt ion, and extraction time, were investigated in detail. Under the optimal conditions, high enrichment factors (71-205) can be obtained with 15 µL extraction solvent. The new method is advantageous; the polypropylene hollow fiber membrane modified by sepiolite nanoparticles had excellent solvent binding force and mass transfer effect compared with the conventional extraction technique. The extracts were analyzed by high performance liquid chromatography-tandem mass spectrometry, the limits of detection were 0.3 or 0.9 ng kg-1 with good correlation coefficients (r2 ≥ 0.9940) for the five fluorescent whitening agents. The intra-day and inter-day recoveries ranged between 82.6% and 112%, with a relative standard deviation of less than 12%. The established method was successfully applied to the analysis of fluorescent whitening agent migration from four types of plastic food contact materials immersed in three food simulants.

A Critical Study of the Effect of Polymeric Fibers on the Performance of Supported Liquid Membranes in Sample Microextraction for Metals Analysis.

Popularity of hollow fiber-supported liquid membranes (HF-SLM) for liquid-phase microextraction (HF-LPME) has increased in the last decades. In particular, HF-SLM are applied for sample treatment in the determination and speciation of metals. Up to the date, optimization of preconcentration systems has been focused on chemical conditions. However, criteria about fiber selection are not reflected in published works. HFs differ in pore size, porosity, wall thickness, etc., which can affect efficiency and/or selectivity of chemical systems in extraction of metals. In this work, Ag+ transport using tri-isobutylphosphine sulfide (TIBPS) has been used as a model to evaluate differences in metal transport due to the properties of three different fibers. Accurel PP 50/280 fibers, with a higher effective surface and smaller wall thickness, showed the highest efficiency for metal transport. Accurel PP Q3/2 exhibited intermediate efficiency but easier handling and, finally, Accurel PP S6/2 fibers, with a higher wall thickness, offered poorer efficiency but the highest stability and capability for metal speciation. Summarizing, selection of the polymeric support of HF-SLM is a key factor in their applicability of LPME for metals in natural waters.

[Determination of two alkaloids in Mongolian medicine Mauleri-Dabusi-4 soup by hollow fiber liquid phase micro-extraction coupled with ultra-high performance liquid chromatography].

In this study, a method combining hollow fiber liquid phase micro-extraction (HF-LPME) and ultra-high performance liquid chromatography (UPLC) was developed for the determination of two alkaloids (piperine and piperlonguminine) in Mongolian medicine Mauleri-Dabusi-4 Soup. The parameters affecting the micro-extraction efficiency were evaluated and optimized. The optimum conditions were as follows:polyvinylidence fluoride HF (54% pore size); 10 g/L NaCl; 30 µ L octanol as extraction solvent; 173 r/min stirring rate of extraction; and 128 min extraction time. The extracted drug was detected by UPLC. The calibration curves obtained good linear relationship in the concentration ranges of 100-8500 and 8.3-5000 µg/L for piperine and piperlonguminine, respectively. The enrichment factors of the method for piperine and piperlonguminine were achieved to be 59 and 65. The limits of detection were 2.2 µg/L for piperine and 2.5 µg/L for piperlonguminine. The method was successfully applied for the determination of alkaloids in Mongolian medicine Mauleri-Dabusi-4.

Hollow Fiber Supported Liquid Membrane Extraction Combined with HPLC-UV for Simultaneous Preconcentration and Determination of Urinary Hippuric Acid and Mandelic Acid.

This work describes a new extraction method with hollow-fiber liquid-phase microextraction based on facilitated pH gradient transport for analyzing hippuric acid and mandelic acid in aqueous samples. The factors affecting the metabolites extraction were optimized as follows: the volume of sample solution was 10 mL with pH 2 containing 0.5 mol·L-1 sodium chloride, liquid membrane containing 1-octanol with 20% (w/v) tributyl phosphate as the carrier, the time of extraction was 150 min, and stirring rate was 500 rpm. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 µL of a solution containing sodium carbonate with pH 11, which was placed inside the lumen of the fiber. Under optimized conditions, the high enrichment factors of 172 and 195 folds, detection limit of 0.007 and 0.009 µg·mL-1 were obtained. The relative standard deviation (RSD) (%) values for intra- and inter-day precisions were calculated at 2.5%-8.2% and 4.1%-10.7%, respectively. The proposed method was successfully applied to the analysis of these metabolites in real urine samples. The results indicated that hollow-fiber liquid-phase microextraction (HF-LPME) based on facilitated pH gradient transport can be used as a sensitive and effective method for the determination of mandelic acid and hippuric acid in urine specimens.

Sequential hollow-fiber liquid phase microextraction for the determination of rosiglitazone and metformin hydrochloride (anti-diabetic drugs) in biological fluids.

A new analytical method for the simultaneous determination of the antidiabetic drugs rosiglitazone (ROS) and metformin hydrochloride (MH) with marked differences in their affinity towards organic solvents (log P of 2.4 and -1.43, respectively) was developed. Prior to the HPLC separation, the drugs were subjected to a sequential hollow fiber liquid phase microextraction (HF-LPME) procedure. Two sequential HF-LPME approaches were considered, the preferred one involves the use of two vials containing solution mixtures for the extraction of ROS (vial 1) and MH (vial 2), respectively, but using the same fiber and acceptor phase. Important parameters that affect the extraction efficiency such as extracting solvent, donor phase conditions, HCl concentration, agitation, extraction time, addition of salt, etc. were studied. Under the optimum conditions, good enrichment factors (EF, 471 and 86.6 for ROS and MH, respectively) were achieved. Calibration curves were linear over the range 1-500 (r(2)=0.998) and 5-2500 ng mL(-1) (r(2)=0.999) for ROS and MH, respectively. The relative standard deviation values (RSD%) for six replicates were below 8.4%. Detection and quantitation limits based on S/N ratio of 3 and 10 were 0.12, 1.0 and 0.36, 3.0 ng mL(-1) for ROS and MH, respectively. The proposed method is simple, sensitive and opens up new opportunities for the microextraction of analytes with contrasting properties.

Calibration of pre-equilibrium HF-LPME and its application to the rapid determination of free analytes in biological fluids.

This study establishes a novel calibration method for pre-equilibrium hollow-fiber liquid-phase microextraction (PE-HF-LPME), where the time constant of the extraction of the analyte from sample matrix to the extraction phase (organic solvent) is obtained from a simple concentration curve. Comparing to the traditional kinetic calibration method, where the time constant was obtained from the extraction time profile, the new calibration approach shows improved accuracy and precision. More importantly, deuterated standards are not required in the new method, thus significantly improving its cost-effectiveness and extending its applicability to a wide range of analytes lack of deuterated analogs serving as internal standards. In addition, mass spectrometry is not necessary for the quantification of analytes with the new calibration method, which may further extend the applicability of PE-HF-LPME to some laboratories without mass spectrometers. This study has been substantiated with both theoretical and experimental evidences. Further, the feasibility of the method for real biological samples was demonstrated by measuring the free concentration of flunitrazepam in urine and plasma samples and its drug-protein binding ratio in plasma. The results showed that the method had a short analysis time and was easily implemented with high accuracy and good reproducibility.

Hollow fiber liquid-phase microextraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry for the simultaneous determination of naloxone, buprenorphine and norbuprenorphine in human plasma.

A hollow fiber liquid phase microextraction (HF-LPME) combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the extraction and determination of naloxone (NLX), buprenorphine (BP) and its major metabolite norbuprenorphine (NBP) in human plasma. The optimum extraction conditions of HF-LPME were: the porous of polyvinylidene fluoride (PVDF) hollow fiber was full of component solvent (1-octanol/chloroform/toluene, 2/4/4), the pH of donor phase was 8.7, the extraction time was 30min and stirring speed was 1000 revolutions per minute (rpm). The UHPLC-MS/MS method was performed with Waters ACQUITY UPLCTM BEH C18, 50mm×2.1mm, 1.7µm, using methanol-0.2%formic acid as mobile phase with a gradient elution at a flow rate of 0.25mL/min. The target compounds were detected under a tandem quadrupole mass spectrometer in positive electrospray ionization (ESI) mode, then analyzed in multiple reaction monitoring (MRM) mode and the isotope internal standard method was used for quantification. The results showed that linearities were in the range of 0.1-25ng/mL (R>0.996). The limits of detection (LOD) of BP/NBP/NLX were 0.05/0.05/0.025ng/mL and the limits of quantitation (LOQ) of BP/NBP/NLX were 0.1/0.1/0.05ng/mL, respectively. The spiked recoveries were in the range of 92.1-106.0% with relative standard deviation (RSD) values were less than 15%. This method was simple, inexpensive, sensitive and has been successfully used to quantify plasma samples from patients included in a clinical pharmacogenetic study.

Sensitive determination of endogenous hexanal and heptanal in urine by hollow-fiber liquid-phase microextraction prior to capillary electrophoresis with amperometric detection.

Hexanal (Hex) and heptanal (Hep) in human blood have been regarded as potential biomarkers of lung cancer. In this work, a hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the preconcentration of these trace aldehydes in urine samples. After derivatization with an electroactive compound 2-thiobarbituric acid, these two non-electroactive aldehydes were converted to electroactive adducts, therefore detectable by capillary zone electrophoresis with amperometric detection (CZE-AD) approach. Experimental conditions of derivatization, extraction, electrophoretic separation and detection were optimized. Under the optimum conditions, the enrichment factors for Hex and Hep could reach 320 and 355, respectively. The limits of detection for Hex and Hep were 2.7 and 0.97 nM, respectively; the average recoveries were in the range of 61-95% and relative standard deviation (RSD) values less than 8.5%. The present method has been applied to quantitative analysis of two biomarkers in human urine in lieu of blood samples, and the assay results showed that the contents of Hex (0.99-6.7 µM) and Hep (2.5-6.4 µM) found in the urine sample of the lung cancer patients were significantly higher than those in the healthy volunteers, liver cancer patients, as well as diabetics. The proposed HF-LPME/CZE-AD method may provide a potential alternative for early non-invasive diagnosis of lung cancer disease.

Green aspects, developments and perspectives of liquid phase microextraction techniques.

Determination of analytes at trace levels in complex samples (e.g. biological or contaminated water or soils) are often required for the environmental assessment and monitoring as well as for scientific research in the field of environmental pollution. A limited number of analytical techniques are sensitive enough for the direct determination of trace components in samples and, because of that, a preliminary step of the analyte isolation/enrichment prior to analysis is required in many cases. In this work the newest trends and innovations in liquid phase microextraction, like: single-drop microextraction (SDME), hollow fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) have been discussed, including their critical evaluation and possible application in analytical practice. The described modifications of extraction techniques deal with system miniaturization and/or automation, the use of ultrasound and physical agitation, and electrochemical methods. Particular attention was given to pro-ecological aspects therefore the possible use of novel, non-toxic extracting agents, inter alia, ionic liquids, coacervates, surfactant solutions and reverse micelles in the liquid phase microextraction techniques has been evaluated in depth. Also, new methodological solutions and the related instruments and devices for the efficient liquid phase micoextraction of analytes, which have found application at the stage of procedure prior to chromatographic determination, are presented.

Hollow fiber liquid phase microextraction with in situ derivatization for the determination of trace amounts of metformin hydrochloride (anti-diabetic drug) in biological fluids.

A three phase hollow fiber liquid-phase microextraction with in situ derivatization (in situ HF-LPME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method was developed for the trace determination of metformin hydrochloride (MH) in biological fluids. A new derivatization agent pentafluorobenzoyl chloride (PFBC) was used. Several parameters that affect the derivatization and extraction efficiency were studied and optimized (i.e., type of organic solvent, volume of NaOH (4M) and derivatization agent in the donor phase, acceptor phase (HCl) concentration, stirring speed, temperature, time and salt addition). Under the optimum conditions (organic solvent, dihexyl ether; volume of NaOH (4M) and derivatization agent (10mg PFBC in 1mL acetonitrile) in the donor phase, 600 and100µL, respectively; acceptor phase, 100mM HCl (10µL); stirring speed, 300rpm; extraction time, 30min; derivatization temperature, 70°C; without addition of salt) an enrichment factor of 210-fold was achieved. Good linearity was observed over the range of 1-1000ngmL(-1) (r(2)=0.9998). The limits of detection and quantitation were 0.56 and 1.68ngmL(-1), respectively. The proposed method has been applied for the determination of MH in biological fluids (plasma and urine) and water samples. Prior to the microextraction treatment of plasma samples, deproteinization step using acetonitrile was conducted. The proposed method is simple, rapid, sensitive and suitable for the determination of MH in a variety of samples.

Hollow-fiber liquid-phase microextraction combined with capillary electrophoresis for trace analysis of sulfonamide compounds.

A hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the preconcentration of trace sulfonamides in water samples. Six commonly used sulfonamides including sulfamethazine (SMZ), sulfamerazine (SMR), sulfadiazine (SDZ), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and sulfathiazole (STZ) were determined by CE with electrochemical detection (CE-ED) after microextraction. Several factors that affect extraction efficiency, separation, and detection were investigated. Under the optimum conditions, above sulfonamide compounds could achieve baseline separation within 35min, exhibiting a linear calibration over three orders of magnitude (r(2)≥0.998); the obtained enrichment factors were between 121 (for SDZ) and 996 (for SDM), and the LODs were in the range of 0.033-0.44ng/mL. The proposed HF-LPME/CE-ED method has been applied for the sensitive analyses of the real-world water samples with recoveries in the range of 75.1-109%.

Determination of chlorophenols in water by headspace solid phase microextraction ion mobility spectrometry (HS-SPME-IMS).

Chlorophenols (CPs) as persistent toxic compounds are of worldwide environmental concern. Usage of chlorinated phenols, especially pentachlorophenol (PCP), has been restricted or widely banned in many countries due to their possible adverse health effects even at low concentrations. Ion mobility spectrometry (IMS) has received increasing interest in environmental applications due to its unique characteristics, such as portability and speed of analysis. A range of sample introduction methods combined with IMS enable analysis from different environmental matrices. This study utilised headspace solid phase microextraction IMS (HS-SPME-IMS) in the determination of CPs from water samples. The extraction conditions were examined and the method was applied to real water samples. The developed method is suitable to detect CPs at milligram per liter level in water. Based on the results, SPME-IMS setup is feasible as an early warning system for water monitoring of pollutants present in drinking or surface water in case of environmental accidents or leakages.

Direct coupling of supported liquid membranes to capillary electrophoresis for analysis of complex samples: a tutorial.

This tutorial provides an overview of direct coupling of extraction techniques based on supported liquid membranes (SLMs) to capillary electrophoresis (CE) for treatment and subsequent analysis of complex samples. Pros and cons of using each of the described instrumental arrangement are addressed and where relevant, comments with personal experience of the authors are presented. Solid porous membrane based extraction techniques coupled directly to CE are also presented in this tutorial and a comprehensive discussion is included on their instrumental set-ups and their possible adaptation for use with SLMs.

Toward decentralized analysis of mercury (II) in real samples. A critical review on nanotechnology-based methodologies.

In recent years, it has increased the number of works focused on the development of novel nanoparticle-based sensors for mercury detection, mainly motivated by the need of low cost portable devices capable of giving fast and reliable analytical response, thus contributing to the analytical decentralization. Methodologies employing colorimetric, fluorometric, magnetic, and electrochemical output signals allowed reaching detection limits within the pM and nM ranges. Most of these developments proved their suitability in detecting and quantifying mercury (II) ions in synthetic solutions or spiked water samples. However, the state of art in these technologies is still behind the standard methods of mercury quantification, such as cold vapor atomic absorption spectrometry and inductively coupled plasma techniques, in terms of reliability and sensitivity. This is mainly because the response of nanoparticle-based sensors is highly affected by the sample matrix. The developed analytical nanosystems may fail in real samples because of the negative incidence of the ionic strength and the presence of exchangeable ligands. The aim of this review is to critically consider the recently published innovations in this area, and highlight the needs to include more realistic assays in future research in order to make these advances suitable for on-site analysis.