Hollow-fiber Liquid-phase Microextraction Method Research Articles

Combination of online hollow fiber liquid phase microextraction with smartphone-based sensing for in situ formaldehyde assay in fabric and wastewater samples.

A miniaturized analytical methodology was introduced based on the combination of a direct and online hollow fiber microextraction method with smartphone color detection. The method was used for the determination of formaldehyde (target analyte) in fabric and wastewater samples. In this regard, two reagents including ammonium acetate buffer and acetylacetone were added to the formaldehyde samples to create a colored compound. The colored compound was extracted from the sample by using the hollow fiber liquid-phase microextraction method, the extracted phase was not taken out of the extraction box and was directly transferred into a specially designed detection cell, and a smartphone was applied forin-situ color sensing and data readout. This combination gathered the advantages of both state-of-the-art microextraction techniques and smartphone sensing. Formaldehyde, as a carcinogenic compound widely used in paint and clothing industries, was selected as a model test. Factors affecting extraction efficiency were investigated and optimized, including the type of organic solvents, reagent concentration, salt, pH, stirring speed, reaction temperature, and extraction time. The linear region of the method under optimal conditions was 40-1500µg L-1 for wastewater samples and 0.3-11.2mg kg-1 for fabrics. The limit of detection and limit of qualification were 13 and 40µg L-1, respectively. The relative standard deviations for concentrations of 100 and 1000µg L-1 were 6% and 4%, respectively. To evaluate the application of the method for real samples, types of fabric and two samples of oil refinery wastewater were selected. The relative recovery in real samples was 84-98%. The results of the analytical parameters of the method show that the developed method can be used as an efficient method to determine formaldehyde in real samples.

Statistical optimization of two-phase hollow fiber liquid-phase microextraction for preconcentration of strychnine in the clinical and postmortem biological fluids prior to gas chromatography-mass spectroscopy detection

Strychnine is a herbal alkaloid whose role in military and doping applications as well as the nervous system stimulation and cancer therapy has been confirmed. Because of its lethal nature, even at low dosages, developing a rapid, sensitive, and accurate method for determination of this alkaloid in the clinical and postmortem samples is of great importance. In this study, a green analytical method based on the two-phase hollow fiber liquid-phase microextraction (HF-LPME) combined with gas chromatography-mass spectrometry (GC–MS) was presented for preconcentration and determination of strychnine in biological fluids. A Box-Behnken design (BBD) with three variables, including extraction time (30–90 min), solution pH (9.0–11.0), and ionic strength (1.0–3.0 mol/L) was employed to maximize the extraction efficiency of strychnine by 1-octanol. The results were satisfactorily fitted to a quadratic response surface model (R2 = 0.979, F = 34.4) which predicted the optimum conditions of operation (extraction time of 89 min, pH = 11.0, and ionic strength of 3.0 mol/L). Based on the results, the studied variables and the interaction between pH and extraction time showed highly significant effects on the process efficiency. The calibration curve was linear in the concentration range of 2.7–1000.0 µg/L (R2 = 0.9978) and the limits of detection and quantitation were found to be 0.8 and 2.7 µg/L, respectively. Moreover, the method was successfully applied to different real samples, including urine (clinical sample), bile and stomach contents, blood, and vitreous humor (postmortem samples), and relative recoveries were obtained in the range of 93.8 % to 99.8 %. The findings of this study suggest that the environmentally friendly HF-LPME method which uses a small amount of a chlorine-free solvent, is a sensitive, cost-effective, simple, and efficient preconcentration method for trace determination of strychnine in biological fluids.

Development of a hollow fiber–liquid phase microextraction method using tissue culture oil for the extraction of free metoprolol from plasma samples

In this research, a method known as a hollow fiber-liquid-phase microextraction was employed to extract and concentrate free metoprolol from plasma samples. The extracted analyte was subsequently determined using high-performance liquid chromatography coupled with a diode-array detector. Several parameters, including hollow fiber length, sonication time, extraction temperature, and salt addition, were investigated and optimized to enhance extraction efficiency. After extracting the analyte under optimum conditions from plasma samples, the enrichment factor and extraction recovery were 50 and 86 %, respectively. Moreover, the method exhibited detection and quantification limits of 0.41 and 1.30 ng mL−1, respectively. The analysis of real samples demonstrated satisfactory relative recoveries in the range of 91–99 %.

Hollow-Fiber Liquid-Phase Micro-Extraction Method for the Simultaneous Derivatization, Extraction, and Pre-concentration of Organotin Compounds from Packed Fruit Juices

Organotin compounds are widely employed as pesticides and fungicides in agriculture and as stabilizers for the industrial manufacture of polyvinyl chloride and other polymers. Accordingly, these endocrine disruptors can be found in a variety of foods and beverages. In the present study, we describe the optimization of a hollow-fiber liquid-phase micro-extraction approach for the simultaneous derivatization, extraction, and pre-concentration of butyltin species from commercial fruit juices with the aim of investigating their migration from the packaging. The best extraction efficiencies were achieved by using hexane as the acceptor solvent and a polypropylene fiber length of 2 cm, whereas the agitation speed, extraction temperature, and total extraction time were set at 1100 rpm, 25 ºC, and 10 min, respectively. Using these optimal conditions, the method was satisfactorily validated in terms of linearity (5–1000 µg L−1), limits of detection (0.8–1.8 µg L−1), recovery (80.5–92.1%), intraday precision (10.2–13.1%), inter-day precision (11.0–15.5%), matrix effect (83.2–91.8%), accuracy (85.2–95.2%), specificity, and carryover. The application of this technique to commercial samples obtained from a local market demonstrated that levels of organotin species in packed fruit juices are negligible, in agreement with the limits established by the European Food Safety Authority (0.14 mg of total organotin compounds per kg of food).

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 (r 2 ≥ 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.

Determination of polar benzotriazoles in aqueous environmental samples by hollow-fibre microextraction method with LC-MS/MS and its comparison to a conventional solid-phase extraction method

A hollow-fibre liquid-phase microextraction method (HF-LPME) was developed for the extraction of polar benzotriazoles from aqueous samples. In combination with LC-MS/MS determination, the method was also validated for environmental waters. Several parameters were optimized, with solvent selection and sample pH having the greatest influence on the enrichment factors. Reduced enrichment factors were observed in HF-LPME from natural waters compared to deionized water, but this was successfully overcome by the addition of 0.20 mM EDTA. Due to matrix effects of up to ±62%, a matrix-matched calibration in river water was used. In terms of its efficacy and applicability for environmental water samples, HF-LPME was compared with a dispersive liquid–liquid microextraction (DLLME) method developed in our previous work and with a conventional solid-phase extraction method. Comparable LODs were achieved: 0.0020–0.16 μg/L for HF-LPME, 0.0020–0.090 μg/L for SPE, and 0.040–0.75 μg/L for DLLME, while repeatability with RSD below ±20% was acceptable for all three methods. The accuracy was highest for SPE, followed by HF-LPME and DLLME. The methods were also compared in terms of environmental impact using the tools Analytical Eco-Scale and GAPI, with HF-LPME giving the best results, followed by DLLME and SPE. Finally, polar benzotriazoles were determined in Slovenian wastewaters at concentrations up to 11.6 μg/L in the influent and up to 9.1 μg/L in the effluent wastewater, but they were generally not detected in samples of river water or groundwater.

Fast Hollow Fiber Liquid-Phase Microextraction as a Greener Alternative for the Determination of N,N-Dimethyltryptamine and Harmala Alkaloids in Human Urine.

Ayahuasca tea is an entheogen hallucinogenic beverage used for shamanic and spiritual purposes, prepared by the decoction of different Amazonian plants containing N,N-dimethyltryptamine (DMT) and harmala alkaloids. Since the therapeutic potential of this tea has been broadly studied in recent years, mainly for the treatment of psychiatric disorders, the determination of the ayahuasca tea components in human and animal matrices is of utmost importance. In order to avoid the use of large amounts of toxic solvents, typically employed in traditional sample preparation methods, hollow fiber liquid-phase microextraction (HF-LPME) presents a greener and time-saving alternative. The present study aims to fully develop and apply an HF-LPME method for the determination of DMT, harmine (HRM), harmaline (HRL), and tetrahydroharmine (THH) in human urine samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Fractional factorial and Box–Behnken designs were used to identify and optimize significant method variables. Once optimized, validation has shown a limit of detection (LoD) of 1.0 ng/ml for DMT and 2.0 ng/ml for the harmala alkaloid. The limit of quantification (LoQ) was of 5.0 ng/ml for all analytes. The method has shown to be linear over a concentration range of 5–200 ng/ml (r2 ≥ 0.99). Intra/inter-day precision and accuracy met the acceptance criteria at the three quality control (QC) levels studied (15.0, 90.0, and 170.0 ng/ml, n = 6, each). Matrix effect evaluation showed predominant ion enhancement and recovery values were above 80%. Dilution factors of 10- and 20-fold have shown acceptable values of accuracy. Selectivity studies showed no interferences. Analysis of eight authentic samples collected from four subjects proved method feasibility. A simple, time-saving and green alternative for the analysis of DMT and harmala alkaloids in human urine samples was developed, optimized using design of experiments, fully validated and applied to authentic samples.

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.

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.

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.

Extraction of carbonyl derivatives from ozonated wastewater samples using hollow fiber liquid phase microextraction followed by gas chromatography-electron capture detection

Herein, a simple and sensitive method was successfully developed for the extraction and quantification of seven carbonyl compounds (acetaldehyde, propanal, butanal, pentanal, hexanal, glyoxal, methylglyoxal) in a number of wastewater samples previously treated by ozonation process. The compounds were initially derivatized (derivatizing reagent (PFBHA)) and then extracted by a hollow-fiber liquid-phase microextraction method (HF-LPME) in the aqueous sample solution. Afterwards, the extraction solvent was withdrawn from the fiber and injected to a gas chromatograph equipped with electron capture detection (GC–ECD). Factors affecting the extraction efficiency of the whole procedure were optimized using a univariate approach. Under the optimal conditions obtained (sample solution pH, 4; organic extraction solvent, dihexylether; stirring rate, 1000 rpm; no salt addition; and extraction time of 40 min), limits of quantification were 0.5–0.8 μg/l for the studied carbonyl compounds. Dynamic linear ranges were 0.5–100 μg/l for five targets (acetaldehyde, propanal, butanal, pentanal and hexanal) and 0.8–80 μg/l for two targets (glyoxal and methylglyoxal). The relative standard deviations (RSDs %) representing the precision of the method were in the range of 6.4–11.9 based on the average of three measurements. Accuracy of the method was also tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 113%. Finally, the method could be used for routine screening of carbonyl compounds in complex matrices.

Analysis of isophthalaldehyde in migration samples from polyethylene terephthalate packaging

ABSTRACTIn the present work, different pre-concentration strategies were evaluated for the analysis of isophthalaldehyde in migration samples from food packaging materials. This compound is a potential migrant in several copolymers used for food packaging, and since it is considered a non-intentionally added substance, its concentration in migration samples must be determined. Derivatisation was the first sample treatment evaluated. o-(2,3,4,5,6-Pentafluorobenzyl)hydroxylamine was tested as derivatisation agent, but no satisfactory results were obtained. Then, hollow-fibre liquid-phase microextraction (HF-LPME) and solid-phase microextraction were optimised. The HF-LPME method showed the highest sensitivity, achieving an enrichment factor of 60-fold. The limit of detection of the method was 10 ng g−1, the limit of quantification was 30 ng g−1 and the relative standard deviation was 6.1%. Finally, the method was applied to migration studies to evaluate the safety in use of a poly(ethylene terephthalate) packaging material. The content of isophthalaldehyde was determined in two aqueous food simulants: 10% ethanol (v/v) and 3% acetic acid (w/v). Different migration conditions were tested. The results obtained showed a considerable rise in the concentration of isophthalaldehyde when increasing the time and temperature of the migration experiment.

Determination of Carotenoids in Egg Yolk by High Performance Liquid Chromatography with Vortex-Assisted Hollow Fiber Liquid-Phase Microextraction using Mixed Extraction Solvent.

A vortex-assisted hollow fiber liquid-phase microextraction method using a mixed solvent as the extraction solvent followed by high performance liquid chromatography diode-array detection was developed for the extraction and determination of two carotenoids including lutein and β-carotene from egg yolk. The method is based on the microextraction of carotenoids from sample solution into extracting agent (20 μL), which is located in the lumen of hollow fiber followed by vortex-mixing. The mixed solvent (1-octanol+1-undecanol, 6:4, v:v) was employed as extracting agent for it has suitable viscosity and compatible with carotenoids via hollow fiber. Vortex-mixing was utilized to provide effective and mild mixing of sample solution and increase the contact between analytes and boundary layers of the hollow fiber. Parameters influencing recoveries were investigated and optimized. Under the optimum conditions, the linear range of lutein and β-carotene were from 50 to 1,000 ng mL-1 The correlation coefficients of the calibration curves were >0.9982, relative standard deviations (n =5) were between 2.23% and 3.51% and the limits of detection were 0.038 and 0.045 μg mL-1 for lutein and β-carotene, respectively. The proposed method was successfully applied to the extraction and determination of caroteonids in egg yolk with the satisfactory relative recoveries (90.2-101.8%).

Simultaneous extraction and quantification of albendazole and triclabendazole using vortex-assisted hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography.

A novel, simple, and rapid vortex-assisted hollow-fiber liquid-phase microextraction method was developed for the simultaneous extraction of albendazole and triclabendazole from various matrices before their determination by high-performance liquid chromatography with fluorescence detection. Several factors influencing the microextraction efficiency including sample pH, nature and volume of extraction solvent, ionic strength, vortex time, and sample volume were investigated and optimized. Under the optimal conditions, the limits of detection were 0.08 and 0.12 μg/L for albendazole and triclabendazole, respectively. The calibration curves were linear in the concentration ranges of 0.3-50.0 and 0.4-50.0 μg/L with the coefficients of determination of 0.9999 and 0.9995 for albendazole and triclabendazole, respectively. The interday and intraday relative standard deviations for albendazole and triclabendazole at three concentration levels (1.0, 10.0, and 30.0 μg/L) were in the range of 6.0-11.0 and 5.0-7.9%, respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, milk, honey, and urine samples.

Development of Hollow-Fiber Liquid-Phase Microextraction Method for Determination of Urinary trans,trans-Muconic Acid as a Biomarker of Benzene Exposure.

For the first time, hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography–ultraviolet was used to extract trans,trans-muconic acid, in urine samples of workers who had been exposed to benzene. The parameters affecting the metabolite extraction were optimized as follows: the volume of sample solution was 11 mL with pH 2, liquid membrane containing dihexyl ether as the supporter, 15% (w/v) of trioctylphosphine oxide as the carrier, the time of extraction was 120 minutes, and stirring rate was 500 rpm. Organic phase impregnated in the pores of a hollow fiber was extracted into 24 µL solution of 0.05 mol L−1 Na2CO3 located inside the lumen of the fiber. Under optimized conditions, a high enrichment factor of 153–182 folds, relative recovery of 83%–92%, and detection limit of 0.001 µg mL−1 were obtained. The method was successfully applied to the analysis of ttMA in real urine samples.

Ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with hybrid artificial neural network-genetic algorithm for speciation and optimized determination of ferro and ferric in environmental water samples.

A novel and environmentally friendly ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with a hybrid artificial neural network (ANN)-genetic algorithm (GA) strategy was developed for ferro and ferric ions speciation as model analytes. Different parameters such as type and volume of extraction solvent, amounts of chelating agent, volume and pH of sample, ionic strength, stirring rate, and extraction time were investigated. Much more effective parameters were firstly examined based on one-variable-at-a-time design, and obtained results were used to construct an independent model for each parameter. The models were then applied to achieve the best and minimum numbers of candidate points as inputs for the ANN process. The maximum extraction efficiencies were achieved after 9 min using 22.0 μL of 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) as the acceptor phase and 10 mL of sample at pH = 7.0 containing 64.0 μg L(-1) of benzohydroxamic acid (BHA) as the complexing agent, after the GA process. Once optimized, analytical performance of the method was studied in terms of linearity (1.3-316 μg L(-1), R (2) = 0.999), accuracy (recovery = 90.1-92.3%), and precision (relative standard deviation (RSD) <3.1). Finally, the method was successfully applied to speciate the iron species in the environmental and wastewater samples.

Hollow fiber based liquid phase microextraction for the determination of organochlorine pesticides in ecological textiles by gas chromatography–mass spectrometry

In this study, the hollow fiber-liquid phase microextraction (HF-LPME) coupled gas chromatograph/mass spectrometry (GC/MS) was firstly developed to determine 10 organochlorine pesticides (OCPs) in ecological textiles. The present method can offer high separation efficiencies with minimal sample and solvent consumption. The extraction conditions were optimized, including the types of hollow fiber and organic solvent, the extraction time, the stirring and the salinity. Under the optimized conditions, the linear ranges of OCPs in cotton, terylene and fur samples were 5–1000ng/g, 10–1000ng/g and 10–800ng/g, respectively, and the detection limit of the three samples were 0.07–2.30ng/g, 0.89–1.66ng/g and 0.06–1.04ng/g, respectively. The optimized method was then successfully used to determine the OCPs in 3 kinds of spiked real samples, including cotton, terylene and fur. The good recoveries and RSDs of the quantification in real textile samples were obtained and the results were confirmed by the traditional liquid extraction method (GB/T 18412-2006). This study proved that the HF-LPME method, which was simple, low-cost and virtually solvent-free, was reliable for the qualitative and quantitative analysis of the harmful OCP residues in ecological textiles.

New method for the determination of bile acids in human plasma by liquid-phase microextraction using liquid chromatography-ion-trap-time-of-flight mass spectrometry

Bile acids (BAs) are derived from cholesterol and produced in the liver. The most abundant bile acids in humans are usually conjugated with glycine and taurine and are divided into primary BAs such as cholic acid (CA) and chenodeoxycholic acid (CDCA) and secondary BAs like deoxycholic acid (DCA), lithocholic acid (LCA) and ursodeoxycholic acid (UDCA).The differences amongst individual bile acids (BAs) are significant in order to distinguish different pathological processes and exposure to chemical compounds. Hollow fiber based liquid-phase microextraction (HF-LPME) is a technique that combines sample cleansing, extraction and the concentration of analytes, where a hydrophobic porous capillary membrane is impregnated with an organic extraction solvent and the lumen is filled with microliters of a phase acceptor both organic by nature. The aim of this study was to develop a new method to extract bile acids from plasma through HF-LPME of two phases (octanol as the acceptor phase) using LCMS-IT-TOF. The optimized two-phased LPME procedure for the extraction of bile acids showed limits of detection 1.0μgL−1 and limits of quantification of 5.0μgL−1. The intra-assay precision ranged from 2.1 to 11.9%. The method developed was linear over the range of 5.0–200.0μgL−1 for all analytes. The hollow-fiber liquid-phase microextraction method was applied to human plasma from workers exposed to organic and halogenated solvents and also to unexposed volunteers. The method is simple, low cost and it does not require large amounts of organic solvents, therefore it is quite suitable for the analysis of bile acids exposed to hepatotoxic compounds.

Determination of nitrophenolic compounds from atmospheric particles using hollow‐fiber liquid‐phase microextraction and capillary electrophoresis/mass spectrometry analysis

A hollow-fiber liquid-phase microextraction method was developed to enrich nine nitrophenolic compounds from aqueous extracts of atmospheric aerosol particles. Analysis was performed by CE coupled with ESI MS. The BGE composition was optimized to a 20 mM ammonium acetate buffer at pH 9.7 containing 15% methanol v/v. Several extraction parameters (composition of organic liquid membrane, pH of acceptor phase, salting-out effect, extraction time) were investigated for their effect on the analyte recoveries. The donor phase consisted of a 1.8 mL sample solution kept at pH 2 while the acceptor phase was a 15 μL 100 mM aqueous ammonia solution. Dihexyl ether served as supported liquid membrane. Low detection limits in the range of nanomole per liter were achieved. Recoveries of aqueous standard solutions were found to be between 11 and 90% with enrichment factors between 10 and 100. Interday and intraday repeatabilities were in an acceptable range for most compounds (6-15% and 7-10%, respectively) but somewhat higher for 4-nitrocatechol (59 and 48%) and 2-nitrophenol (17 and 35%). The developed method was found to be competitive with more established method and was successfully applied to samples of atmospheric particulate matter from field experiments.

Chemometric optimization of hollow fiber-liquid phase microextraction for preconcentration of trace elements in diesel and gasoline prior to their ICP-OES determination

A hollow fiber-liquid phase microextraction (HF-LPME) method for the simultaneous extraction and preconcentration of Ag, Al, As, Mn and Ti as ammonium pyrrolidine dithiocarbamate (APDC) complexes in [C6MIM][PF6] ionic liquid are reported. Multivariate techniques such as 24 factorial and Box–Behnken designs were used for the optimization of experimental parameters. Under optimized conditions, the limits of detection and quantification ranged from 0.04 to 0.09 and 0.15–0.29μgL−1, respectively. The preconcentration factors of 150, 291, 112, 405, 367 for Ag, Al, As, Mn and Ti, respectively, were achieved. The precision of the HF-LPME method estimated as the relative standard deviation (RSD) for five replicate determinations of metal ions at a concentration of 10μgL−1 was less than 5%. The HF-LPME method was verified by analysis of the target analytes in commercial diesel and gasoline samples. The accuracy of the proposed method was confirmed by performing standard addition method (spike recovery experiments, that is, spiking the samples with known amount of the standard). The recovery values (96–101%) indicated a satisfactory accuracy.