Solvent Bar Microextraction Research Articles

Membrane Assisted Simultaneous Extraction and Derivatization with Triphenylphosphine of Elemental Sulfur in Arabian Crude Samples by Gas Chromatography/Mass Spectrometry

Determination of trace level elemental sulfur from crude oil samples is a tedious task. Recently, several gas chromatographic methods were reported in which selective triphenylphosphine derivatization of sulfur was used to form triphenylphosphine sulfide. Direct quantitation of elemental sulfur from crude oil requires an efficient sample preparation method. This paper describes how simultaneous extraction derivatization of elemental sulfur was performed for the first time using porous hollow fiber membrane. A thick (0.25 um pore size; 1550 μm wall thickness; and 5500 μm inner diameter) hollow fiber membrane filled with triphenylphosphine (dissolved N-methylpyrrolidone) is used as a solvent bar. The solvent bar is tumbled freely in the crude oil sample; the elemental sulfur was extracted and derivatized. Finally, the derivatized sulfur was analyzed by gas chromatography/mass spectrometry. Various experimental conditions of solvent bar microextraction (SBME) were optimized to achieve higher extraction. The linear range was established between 1 and 50 μg/mL, while a squared regression coefficient was found to be 0.9959 μg/mL. Relative standard deviation (RSD) was below 10%. Relative recoveries were calculated for SBME in crude oil samples and were in the range between 98.2% and 101.2%.

Three-phase solvent bar micro-extraction as an approach to silver ultra-traces speciation in estuarine water samples

Silver ion inputs into the environment due to human activities have been increased in the last years because it has been used as a bactericide with application in medical, homecare and self-care products. In addition, it is toxic at low concentration for aquatic organisms. In estuarine waters, salinity and dissolved organic matter (DOM) regulate Ag+ concentration by the formation of complexes as AgCln(n-1)− and Ag-DOM.Difficulties of Ag+ analysis in estuaries are associated to its low concentration level and interferences of sample matrix. Liquid and solid phase extraction methods have been used for speciation of silver in waters; however, miniaturized methods that offer a better environmental profile are desirable. Hollow fiber liquid phase micro-extraction (HFLPME) allows obtaining higher pre-concentration factors with a reduction of waste generation. Notwithstanding, some operational improvements are needed to permit their use as a routine method that can be afforded using a configuration of three-phase solvent bar micro-extraction (3PSBME).In this work, tri-isobutylphosphine sulphide (TIBPS) has been used as an extractant for Ag+ pre-concentration in estuarine waters by 3PSBME. Under optimized conditions, Ag+ has been pre-concentrated 60 times and the method presents a limit of detection of 1.53ngL−1. To evaluate which Ag species is transported by TIBPS, Cl− and DOM have been added to synthetic samples. As a result, a decrease in Ag pre-concentration efficiency after additions has been observed and quantified. Results showed that Ag+ is selectively transported by TIBPS from estuarine water samples after comparison of the results with those obtained by the reference method of liquid extraction with APDC/DDDC.

Determination of Sulfonylurea Herbicides in Pears Using Hollow Fiber-Protected Magnetized Solvent-Bar Liquid-Phase Microextraction HPLC

Hollow fiber-protected magnetized solvent-bar liquid-phase microextraction of sulfonylurea herbicides, including nicosulfuron, bensulfuron-methyl, pyrazosulfuron and chlorimuron-ethyl, in pears was developed. The analytes were determined by high-performance liquid chromatography. This present method has the advantages of stir bar sorptive extraction and hollow fiber-protected solvent-bar microextraction, that permits active magnetic stirring, extraction and preenrichment in a single device simultaneously. The magnetized solvent-bar was easily retrieved after extraction with a magnet, so the extract is conveniently collected. Experimental parameters, including type of extraction solvent, the number of magnetized solvent-bars, extraction temperature and time, stirring speed, pH of the sample solution, and the salting-out effect, were investigated and optimized. Under optimal experimental conditions, the calibration curve showed good linearity (r ≥ 0.9998). The limits of detection and quantification were in the range of 7.15–8.26 ng/g and 24.99–27.52 ng/g, respectively. The recoveries were in the range of 80.08–105.56 %, and the relative standard deviations were lower than 6.82 %. The results showed that the present method was a satisfactory method for the determination of sulfonylurea herbicides in pears.

Determination of Organochloride and Triazine Pesticides in Natural Waters by Solvent Bar Microextraction

A new analytical methodology based on solvent bar microextraction has been developed to preconcentrate two triazine and two organochloride pesticides in natural waters prior to analysis by gas chromatography. The method was optimized for the organic solvent, sample pH, sample agitation, length of the fiber, extraction time, and salt concentration. The optimized methodology provides high enrichment factors, ranging between 40.2 (aldrin) to 107.0 (lindane). Since no salinity effects were observed, this method may be used to analyze fresh and salt water. Thus, three real samples with different salinities were analyzed with pesticide recoveries higher than 80%. As this methodology agreed with the principles of green analytical chemistry, it offers low solvent and sample consumption, simplicity, and compatibility with current analytical techniques.

Analysis of Local Anesthetics in Biological Samples via Kinetically Calibrated Liquid-Phase Solvent Bar Micro-Extraction Combined with HPLC

In this study, a liquid-phase solvent bar micro-extraction technique was used to investigate both the extraction and back-extraction processes of the target analyte. A novel concentration curve method and a classic time curve method, used under the same experimental conditions, verified the symmetry between the extraction process (target analyte moves from sample matrix to the organic solvent-based extraction phase) and the back-extraction process (target analyte moves from organic solvent to the sample matrix), providing the basis to use the target analyte in the back-extraction process to calibrate its extraction process. A quantitative calibration can be achieved using back extraction on the target analyte from the blank sample matrix in the organic solvent. Information from the process of back extraction of the target analyte, such as the time constant a, can be directly used to calculate the initial concentration of the target analyte in the sample matrix. This new kinetic calibration method employs a liquid-phase solvent bar micro-extraction technique combined with high-performance liquid chromatography with a diode array detector (HPLC-DAD) and was successfully used to analyze three local anesthetics in biological samples; it extends the application of the kinetic calibration to HPLC-DAD and establishes a novel, simple and accurate method to determine the concentration of the free drug in biological samples and its protein-binding ratio.

Hollow Fiber/Solvent Bar Microextraction Coupled with High Performance Liquid Chromatography for Preconcentration and Determination of Tanshinones and Salvianolic Acids in Radix Salvia miltiorrhiza

Hollow fiber solvent bar microextraction coupled with high-performance liquid chromatography was developed for the preconcentration and determination of active ingredients in Radix Salvia miltiorrhiza. These ingredients include dihydrotanshinone I, cryptotanshinone, tanshinone I, tanshinone IIA, salvianolic acid B, danshensu, and protocatechuic aldehyde. To evaluate the technique, seven compounds of varying polarity were used as model analytes, and a polyvinylidene fluoride hollow fiber (1.0 cm) with octanol (2 µL) was used as microextraction bar. The extraction conditions, including the identity of the hollow fiber, organic solvent, pH, salt addition, agitation speed, extraction time, and volume, were investigated and optimized. The extraction mechanism was analyzed and verified. The two main parameters, extraction recovery and enrichment factor, were obtained. Under the most favorable conditions, the enrichment factors of the analytes were 0.7–612, the limits of detection were below 1.11 ng mL−1, and the recoveries were between 95.4% and 101.3%. Thus, hollow fiber solvent bar microextraction is simple, rapid, and practical with a wide range of potential applications.

Optimization of solvent bar microextraction combined with gas chromatography for preconcentration and determination of methadone in human urine and plasma samples

In this study, solvent bar microextraction combined with gas chromatography-flame ionization detector (GC-FID) was used for preconcentration and determination of methadone in human body fluids. The target drug was extracted from an aqueous sample with pH 11.5 (source phase) into an organic extracting solvent (1-Undecanol) located inside the pores and lumen of a polypropylene hollow fiber as a receiving phase. To obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied using an experimental design. The variables of interest were the organic phase type, source phase pH, ionic strength, stirring rate, extraction time, concentration of Triton X-100, and extraction temperature, which were first investigated by Plackett-Burman design and subsequently by central composite design (CCD). So that the optimum experimental condition was obtained when the sodium chloride concentration was 5% (w/v); stirring rate, 700 rpm; extraction temperature, 20 °C; extraction time, 45 min and pH of the aqueous sample, 11.5. Under the optimized conditions, the preconcentration factors were between 275 and 300. The calibration curves were linear in the concentration range of 10-1500 μg L(-1). The limits of detection (LODs) were 2.7-7 and relative standard deviations (RSDs) of the proposed method were 5.9-7.3%. Ultimately, the applicability of the current method was evaluated by the extraction and determination of methadone in different biological samples.

Solvent Bar Microextraction with HPLC for Determination and Protein-Binding Characteristics of Oleanolic Acid and Ursolic Acid

An improved solvent bar microextraction (SBME) combined with HPLC was applied to rapidly determine oleanolic acid (OA) and ursolic acid (UA) in Chinese medicinal herbs (CMHs), and to investigate drug–protein binding. Variables influencing SBME were investigated and optimized. Under optimal conditions, the linear ranges of 3.6–1,820 ng mL−1 for OA and 4.2–2,080 ng mL−1 for UA were obtained with square correlation coefficients of 0.9996 and 0.9997, respectively. The detection limits were 1.3 ng mL−1 for OA and 1.5 ng mL−1 for UA. The relative standard deviations were lower than 9.4 %. The protein-binding rates, the numbers of binding sites, and the binding constants of OA and UA were also obtained via the method. It has been demonstrated that SBME can not only be a simple, rapid and efficient sample preparation method for determination of active components from CMHs but also be a potential research protocol for protein-binding interactions.

Solvent bar microextraction combined with high‐performance liquid chromatography for preconcentration and determination of pramipexole in biological samples

A simple, rapid and sensitive analytical method for preconcentration and determination of pramipexole in different biological samples has been developed using solvent bar microextraction (SBME) combined with HPLC-UV. The target drugs were extracted from 10 mL of basic aqueous sample solution into an organic extracting solvent located inside the pores of a polypropylene hollow fiber, then back-extracted into an acidified aqueous solution in the lumen of the hollow fiber. In order to obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The experimental parameters of SBME were optimized using a Box-Behnken design after a Plackett-Burman screening design. Under the optimized conditions, an enrichment factor up to 96 was achieved and the relative standard deviation of the method was 4.64% (n = 5). The linear range was 0.05-2000 µg/L with a correlation coefficient (r) of 0.987. Finally, the applicability of the proposed method was evaluated by extraction and determination of pramipexole in plasma and urine samples. The results indicated that SBME method has excellent clean-up and high preconcentration factor and can serve as a simple and sensitive method for analysis of pramipexole in biological samples.

Carrier mediated transport solvent bar microextraction for preconcentration and determination of dexamethasone sodium phosphate in biological fluids and bovine milk samples using response surface methodology

In the current study, a fast and simple preconcentration and sample clean up procedure was developed based on carrier mediated three phase solvent bar liquid phase microextraction (TPSB-LPME) method prior to high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) absorbance detector for simultaneous extraction and determination of trace amounts of dexamethasone sodium phosphate (DSP) in human plasma, human urine and bovine milk. According to this procedure, dexamethasone sodium phosphate was extracted from an acidic aqueous sample (SP, 7.5mL with pH=6) into the organic solvent 1-octanol (containing 5%, w/v of Aliquat-336 as carrier) residing in the pores of a hollow fiber and then back extracted into an alkali receiving phase (RP, 5μL of 0.65M NaClO4 with pH=10) was located inside the lumen of the fiber. After the extraction period, the receiving phase was directly injected into HPLC. The effect of different extraction conditions (i.e., pH of source and receiving phases, ionic strength, stirring rate, counter-ion concentration and extraction time) on the extraction efficiency of DSP was investigated and optimized using central composite design (CCD) as a powerful tool. Under the optimal conditions, preconcentration factor of 320, extraction recovery of 23%, dynamic linear range of 1-1000ngmL(-1) (r(2)=0.997) and limit of detection of 0.1ngmL(-1) were obtained. Eventually, applicability of the proposed method was successfully confirmed by extraction and determination of drug in plasma and urine samples and bovine milk with R.S.D.s<8%. Comparing to the traditional methods, the proposed method exhibits high sensitivity and high preconcentration factors as well as good precision. The extraction setup is simple and due to active transport of analytes, high cleanup effect and good selectivity are obtained in the extraction process. This extraction technique is also the most economical sample preparation and preconcentration technique as compared to traditional extraction techniques.

Microwave assisted extraction combined with solvent bar microextraction for one-step solvent-minimized extraction, cleanup and preconcentration of polycyclic aromatic hydrocarbons in soil samples

For the first time, a novel one-step sample preparation method that combines microwave assisted extraction and solvent bar microextraction (MAE–SBME) with analysis by gas chromatography–mass spectrometry (GC–MS), was developed for the fast and efficient determination of polycyclic aromatic hydrocarbons (PAHs) in environmental soil samples. An interesting feature of the new procedure is that SBME was conducted simultaneously with MAE. Thus, the extract from the SBME could be directly and immediately analyzed by GC–MS. A separate clean up and/or preconcentration process, such as time-consuming and tedious gel permeation chromatography, solid-phase extraction, filtration, or adsorption chromatography, normally associated with conventional MAE, was not necessary. It is also notable that the procedure was environmentally benign since water was used as the extraction solvent in MAE, and only several microliters of organic solvent were used in SBME. Some factors affecting the extraction were studied and optimized. Under the most favorable conditions, the method showed good linearities (between 0.2 and 500, 0.5 and 500, 1 and 500, and 2 and 500ng/g, depending on the analytes), low limits of detection (from 0.03 to 0.25ng/g), and satisfactory precision (with relative standard deviations below 9.8%). The MAE–SBME procedure provides a fast and simple sample preparation approach for the processing of environmental soil samples.

Ionic liquid-based solvent bar microextraction for determination of organophosphorus pesticides in water samples

In this article, a method of ionic liquid-based solvent bar microextraction combined with high performance liquid chromatography was developed to measure organophosphorus pesticides (OPPs) in water samples. The solvent bar microextraction was based on applying hydrophobic ionic liquid to the lumen and wall pores of a hollow fiber. The main factors influencing the extraction including types of ionic liquid, stirring speed, extraction time, extraction temperature, and salt effect were investigated. The proposed method was successfully applied in the analysis of real environmental water samples under the optimal extraction conditions and good spiked recoveries of 86.71–103.7% were obtained. The linear range was 1–200 μg L−1 and the detection limits were 0.015–0.026 μg L−1 for the four OPPs analyzed. These results demonstrated that solvent bar microextraction was a simple and accurate technique with a high enrichment factor.

Vortex solvent bar microextraction for phthalate esters from aqueous matrices

An improved hollow fiber solvent bar microextraction method termed as vortex solvent bar microextraction (VSBME) was developed. A short hollow fiber immobilized with organic extraction solvent was served as the solvent bar for microextraction of phthalate esters from aqueous matrices. The hydrophobic analytes were pre-focused at the bottom of the vortex under the vigorous magnetic stirring before extraction, which facilitated the mass transfer of analytes from aqueous matrix to organic extraction phase in the subsequent solvent bar microextraction. With the extraction solvent lost gradually from the hollow fiber under the stirring, the efficient extraction was maintained by the absorption of analytes in the porous membrane. After extraction, the analytes were desorbed from the hollow fiber membrane using 50μL organic solvent. The phthalate esters with 1-octanol/water partition coefficients ranging from 1.69 to 8.83 were used as model compounds to investigate the extraction performance. Extraction conditions such as type and volume of extraction solvents, stirring intensity, extraction time, sample concentration and volume were investigated and optimized. Analysis was carried out with gas chromatography–mass spectrometry (GC–MS). Under the optimum conditions, this new method gave super high enrichment factors (over 1500), good reproducibility (<7.1%, n=6) in a rapid extraction within 5min. It allowed the determination of phthalate esters at ngL−1 level. Compared with the other microextraction methods, the proposed VSBME was simpler, more robust and had higher enrichment efficiency. The matrix effects on the extraction performance were also investigated with bottled ice red tea, red wine and human urine.

Ultrasonic-assisted water extraction and solvent bar microextraction followed by gas chromatography–ion trap mass spectrometry for determination of chlorobenzenes in soil samples

A novel and simple analytical method for the determination of chlorobenzenes (CBs) in soil samples was developed using ultrasonic-assisted water extraction (UAWE) coupled with solvent bar microextraction (SBME). Four chlorobenzenes, 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), hexachlorobenzene (HCB), and 1-chloro-4-nitrobenzene (1-C-4-NB), were used as model compounds to investigate the extraction performance. Parameters affecting the extraction efficiency were investigated in detail. UAWE was used for the extraction of CBs from 1.0g of sediment using 10mL of ultrapure water at 100W for 30min at 30–35°C. The extract was subsequently subjected to a single step SBME cleanup and enrichment procedure. Both ends of the solvent bar with about 4μL of 1-octanol were sealed by a sealing machine, and it was placed in the soil slurry for extraction. After extraction, analysis was carried out by gas chromatography–ion trap mass spectrometry (GC–ITMS) detection. The relative recoveries from the spiked soil sample varied between 93 and 105% for CBs, and exceeded levels achieved for conventional Soxhlet extraction. The method linearities were 10–150, 40–600, and 100–1500ngg−1 for different CBs. The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.7–27.3ngg−1 and 2.2–90.9ngg−1, respectively. Good reproducibilities were obtained with relative standard deviation (RSD) values below 6.8%. The analytical potential of the method was demonstrated by applying the method to spiked soil sample.

Optimization of solvent bar microextraction combined with gas chromatography mass spectrometry for preconcentration and determination of tramadol in biological samples

A simple, rapid and sensitive analytical method for preconcentration and determination of tramadol in different biological samples have been developed using solvent bar microextraction (SBME) combined with gas chromatography–mass spectrometry (GC–MS). The target drugs were extracted from 12ml of aqueous sample with pH 12.0 (source phase; SP) into an organic extracting solvent (n-nonanol) located inside the pores and lumen of a polypropylene hollow fiber (receiving phase; RP). In order to obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied using an experimental design. The variables of interest were the type of organic phase, pH of the source phases, ionic strength, volume of the source phase, stirring rate, extraction time and temperature. The experimental parameters of SBME were optimized using a Box–Behnken design (BBD) after a Plackett–Burman screening design. The detection limits were 0.02μgL−1 with 4.5% RSD (n=5, c=10μgL−1) for tramadol. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in different biological samples. The results indicated that SBME method has excellent clean-up and high-preconcentration factor and can be served as a simple and sensitive method for monitoring of tramadol in the biological samples.

One step solvent bar microextraction and derivatization followed by gas chromatography–mass spectrometry for the determination of pharmaceutically active compounds in drain water samples

For the first time, a simple and novel one-step combined solvent bar microextraction with derivatization with GC–MS analysis, was developed for the determination of pharmaceutically active compounds (PhACs) in water samples. In the procedure, the derivatization reagent was added in the extraction solvent (solvent bar), so that the analytes could be extracted from the aqueous sample and simultaneously derivatized in the solvent bar to enhance their volatility and improve chromatographic performance. After extraction, the derivatized analytes in the extract were directly injected into a GC–MS system for analysis. Six PhACs including naproxen, ibuprofen, ketoprofen, propranolol, diclofenac, and alprenolol were used here to develop and evaluate the method. The parameters affecting the derivatization and extraction efficiency including derivatization time and temperature, the proportion of derivatization reagent, the type of organic solvent, extraction time, extraction temperature, pH of sample solution, effect of ionic strength, and sample agitation speed, were investigated in detail. Under the most favorable conditions, the method provided good limits of detection ranging from 0.006 to 0.022μg/L, linearity (from 0.1–50 to 0.2–50μg/L, depending on analytes) and repeatability of extractions (RSDs below 9.5%, n=5). The proposed method was compared to hollow fiber protected liquid-phase microextraction and solid-phase microextraction, and showed higher extraction efficiency and/or shorter extraction time. The proposed method was applied to the determination of six PhACs in drain water, and was demonstrated to be simple, fast and efficient.

Ionic liquid based three-phase liquid–liquid–liquid solvent bar microextraction for the determination of phenols in seawater samples

For the first time, an ionic liquid based three-phase liquid–liquid–liquid solvent bar microextraction (IL-LLL-SBME) was developed for the analysis of phenols in seawater samples. The ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6]), was used as the intermediary solvent for LLL-SBME, enhancing the extraction efficiency for polar analytes. In the procedure, the analytes were extracted from the aqueous sample into the ionic liquid intermediary and finally, back-extracted into an aqueous acceptor solution in the lumen of the hollow fiber. The porous polypropylene membrane acted as a filter to prevent potential interfering materials from being extracted, and no additional cleanup was required. After extraction, the acceptor solution could be directly injected into a high-performance liquid chromatographic system for analysis. Six phenols, 2-nitrophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were selected here as model compounds for developing and evaluating the method. The most influential extraction parameters were evaluated, including the ionic liquid, the composition of donor solution and acceptor solution, the extraction time and the extraction temperature, the effect of ionic strength, and the agitation speed. Under the most favorable extraction parameters, the method showed good linearity (from 0.05–50 to 0.5–50 μg/L, depending on the analytes) and repeatability of extractions (RSD below 8.3%, n = 5). The proposed method was compared to conventional three-phase LLL-SBME and ionic liquid supported hollow fiber protected three-phase liquid–liquid–liquid microextraction, and showed higher extraction efficiency. The proposed method was demonstrated to be a simple, fast, and efficient method for the analysis of phenols from environmental water samples.

Three-Phase Solvent Bar Microextraction Combined with HPLC for Extraction and Determination of Plasma Protein Binding of Bisoprolol

A three-phase solvent bar microextraction (TPSBME) technique combined with high performance liquid chromatography (HPLC)–fluorescence detection was evaluated for the quantitative determination of plasma protein binding of bisoprolol. Bisoprolol was extracted from a 5.6-mL basified plasma sample (donor phase) into the organic solvent (n-octanol) impregnated in the pores of a hollow fiber and then extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. Metoprolol was used as the internal standard. Several parameters influencing the efficiency of the method were investigated and optimized including organic solvent (n-butanol, n-octanol, dibutyl phthalate, dihexyl ether), stirring rate (100–1,000 rpm), extraction time (5–35 min), extraction temperature (15–45 °C), concentration of the donor phase (0.1–2 M NaOH) and the acceptor phase (0.5–5 M formic acid), salt concentration (2.5–10%, w/v). Under the optimal condition, extraction recoveries from plasma samples were above 61.4% for bisoprolol. The calibration curves were obtained in the range of 10–100 ng mL−1 with reasonable linearity (r > 0.994). The method was successfully applied to determine the plasma protein binding rate of bisoprolol.

Solvent-bar microextraction of herbicides combined with non-aqueous field-amplified sample injection capillary electrophoresis

Solvent-bar microextraction (SBME) based on two-phase (water-to-organic) extraction was for the first time used as the sample pretreatment method for the non-aqueous capillary electrophoresis (NACE) of herbicides of environmental concern. Due to the compatibility of the extractant organic solvent and the NACE separation system, the extract could be introduced directly to the CE system after SBME. Through investigations of the effect of sample pH, extraction time, agitation speed and salt addition on extraction efficiency, the most suitable extraction conditions were determined: sample solution at a pH of 1, without added salt, and stirring at 700 revolutions per minute for 30 min. SBME as applied here was also compared with single-drop microextraction and hollow fiber-protected liquid-phase microextraction. SBME showed the highest extraction efficiency. In addition, field-amplified sample injection with pre-introduced organic solvent plug removal using the electroosmotic flow as a pump (FAEP) was used to enhance the sensitivity further in NACE. Based on studies of the effect of different organic solvents, different lengths of the organic plugs and different volumes of sample injection on stacking efficiency under the most suitable separation conditions, methanol was found to be the most efficient solvent for on-line preconcentration. Combined with SBME, FAEP-NACE achieved limits of detection of between 0.08 ng/mL and 0.14 ng/mL for the studied analytes. This preconcentration approach for NACE was demonstrated to be amenable to aqueous environmental samples by applying it to spiked river water.

Optimization of solvent bar microextraction combined with gas chromatography for the analysis of aliphatic amines in water samples

Solvent bar microextraction (SBME) combined with gas chromatography-flame ionization detector (GC-FID), was used for preconcentration and determination of some aliphatic amines in waste water samples. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the SBME were ionic strength, organic additive effect, sodium hydroxide concentration, stirring rate and extraction time and temperature. A Plackett-Burman design was performed for screening in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by a Box-Behnken design (BBD) and the response surface equations were derived. The optimum experimental conditions were sodium chloride concentration, 20% (w/v); sodium hydroxide concentration, 1 mol L(-1); stirring rate, 700 rpm; extraction temperature, 45 degrees C; extraction time, 30 min, and without addition of acetone. Under the optimum conditions, the preconcentration factors were between 260 and 1130. The limit of detections (LODs) ranged from 0.01 microg L(-1) (for dibutylamine) to 0.06 microg L(-1) (for N-ethyldiisopropylamine). The linear dynamic ranges (LDRs) of 0.05-800 and 0.1-600 microg L(-1) were obtained for most of the analytes. The performance of the method was evaluated for extraction and determination of aliphatic amines in waste water samples in the range of microgram per liter and satisfactory results were obtained (RSDs<13.6%).