Dispersive liquid–liquid microextraction with little solvent consumption combined with gas chromatography–mass spectrometry for the pretreatment of organochlorine pesticides in aqueous samples

Dispersive liquid–liquid microextraction with little solvent consumption (DLLME-LSC), a novel dispersive liquid–liquid microextraction (DLLME) technique with few solvent requirements (13 μL of a binary mixture of disperser solvent and extraction solvent in the ratio of 6:4) and short extraction time (90 s), has been developed for extraction of organochlorine pesticides (OCPs) from water samples prior to gas chromatography/mass spectrometry analysis. In DLLME-LSC, much less volume of organic solvent is used as compared to DLLME. The new technique is less harmful to environment and yields a higher enrichment factor (1885–2648-fold in this study). Fine organic droplets were formed in the sample solution by manually shaking the test tube containing the mixture of sample solution and extraction solvent. The large surface area of the organic solvent droplets increases the rate of mass transfer from the water sample to the extractant and produces efficient extraction in a short period of time. DLLME-LSC shows good repeatability (RSD: 4.1–9.7% for reservoir water; 5.6–8.9% for river water) and high sensitivity (limits of detection: 0.8–2.5 ng/L for reservoir water; 0.4–1.3 ng/L for river water). The method can be used on various water samples (river water, tap water, sea water and reservoir water). It can be used for routine work for the investigation of OCPs.     

Solid-phase microextraction for the investigation of sex pheromone of Eucosma notanthes Meyrick

A simple and efficient technique that does not require solvent and uses less operating time for the investigation of sex pheromones of the carambola fruit borer (Eucosma notanthes Meyrick) by utilizing headspace solid-phase microextraction (SPME) followed by GC-MS analysis has been developed. Variables such as types of SPME fiber, number of pests, temperature and extraction time have been studied. Whole sex glands of Eucosma notanthes Meyrick were dissected from 5 virgin insects, placed in a 2 mL vial, equilibrated at 170 °C for 10 min, and then extracted by headspace SPME at room temperature for 5 min. The results of the GC-MS analyses of headspace SPME of these sex glandular solid samples were much better than those obtained with hexane extraction of sex glandular from 117 insects followed by either headspace SPME or direct injection due to higher absorption efficiency. The simplicity of this technique renders it a very suitable method for research on the biological control of pests.     

Temperature-controlled headspace liquid-phase microextraction device using volatile solvents

A novel temperature-controlled headspace liquid-phase microextraction (TC-HS-LPME) device was established in which volatile solvents could be used as extractant. In this device, a PTFE vial cap with a cylindrical cavity was used as the holder of the extraction solvent. Up to 40 μl of extraction solvent could be suspended in the cavity over the headspace of aqueous sample in the vial. A cooling system based on thermoelectric cooler (TEC) was used to lower the temperature of extractant in PTFE vial cap to reduce the loss of volatile solvent during extraction process and increase the extraction efficiency. The selection of solvents for HS-LPME was then extended to volatile solvents, such as dichloromethane, ethyl acetate and acetone. The use of volatile extraction solvents instead of semi-volatile solvent reduced the interference of the large solvent peak to the analytes peaks, and enhanced the compatibility of HS-LPME with gas chromatograph (GC). Moreover, the use of larger volume of extractant solvent increases the extraction capacity and the injection volume of GC after extraction, thus improving detection limits. Several critical parameters of this technique were investigated by using chlorobenzenes (CBs) as the model analytes. High enrichment factors (498–915), low limits of detection (0.004–0.008 μg/L) and precision (3.93–5.27%) were obtained by using TC-HS-LPME/GC-FID. Relative recoveries for real samples were more than 83%.     

Determination of organophosphorous pesticides in water using in-syringe ultrasound-assisted emulsification and gas chromatography with electron-capture detection

An in-syringe ultrasound-assisted emulsification microextraction (USAEME) was developed for the extraction of organophosphorus pesticides (OPPs) from water samples. The OPPs subsequently analyzed gas chromatography (GC) using a microelectron capture detector (μECD). Ultrasound radiation was applied to accelerate the emulsification of μL-level low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OPPs in the sample preparation for GC-μECD. Parameters affecting the efficiency of USAEME, such as the extraction solvent, solvent volume, pH, salt-addition, and extraction time were thoroughly investigated. Based on experimental results, OPPs were extracted from a 5 mL aqueous sample by the addition of 20 μL toluene as the extraction solvent, followed by ultrasonication for 30 s, and then centrifugation for 3 min at 3200 rpm, offered the best extraction efficiency. Detections were linear in the concentration of 0.01–1 μg/L with detection limits between 1 ng/L and 2 ng/L for OPPs. Enrichment factors ranged from 330 to 699. Three spiked aqueous samples were analyzed, and recovery ranged from 90.1% to 104.7% for farm-field water, and 90.1% to 101.8% for industrial wastewater. The proposed method provides a simple, rapid, sensitive, inexpensive, and eco-friendly process for determining OPPs in water samples.     

Determination of organochlorine pesticides in water using solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction

The organic solvent film formed within a hollow fiber was used as an extraction interface in the headspace liquid-phase microextraction (HS-LPME) of organochlorine pesticides. Some common organic solvents with different vapor pressures (9.33-12,918.9 Pa) were studied as extractants. The results indicated that even the solvent with the highest vapor pressure (cyclohexane) can be used to carry out the extraction successfully. However, those compounds (analytes) with low vapor pressures could not be extracted successfully. In general, the large surface area of the hollow fiber can hasten the extraction speed, but it can increase the risk of solvent loss. Lowering the temperature of the extraction solvent could not only reduce solvent loss (by lowering its vapor pressure) but also extend the feasible extraction time to improve extraction efficiency. In this work, a solvent cooling assisted dynamic hollow-fiber-supported headspace liquid-phase microextraction (SC-DHF-HS-LPME) approach was developed. By lowering the temperature of the solvent, the evaporation can be decreased, the extraction time can be lengthened, and, on the contrary, the equilibrium constant between headspace phase and extraction solvent can be increased. In dynamic LPME, the extracting solvent is held within a hollow fiber, affixed to a syringe needle and placed in the headspace of the sample container. The extracting solvent within the fiber is moved to-and-fro by using a programmable syringe pump. The movement facilitates mass transfer of analyte(s) from the sample to the solvent. Analysis of the extract was carried out by gas chromatography-mass spectrometry (GC-MS). The effects of identity of extraction solvent, extraction temperature, sample agitation, extraction time, and salt concentration on extraction performance were also investigated. Good enrichments were achieved (65-211-fold) with this method. Good repeatabilities of extraction were obtained, with RSD values below 15.2%. Detection limits were 0.209 microg/l or lower.     

Extraction and determination of organophosphorus pesticides in water samples by a new liquid phase microextraction-gas chromatography-flame photometric detection

A rapid, sensitive and efficient liquid phase microextraction (LPME) method was developed to determine trace concentrations of some organophosphorus pesticides in water samples. This method combines liquid phase microextraction with gas chromatographic (GC) analysis in a simple and inexpensive apparatus involving very little organic solvent consumption. It involves exposing a floated drop of an organic solvent on the surface of aqueous solution in a sealed vial. Experimental parameters which control the performance of LPME such as type of organic solvent, organic solvent and sample volumes, sample stirring rate, sample solution temperature, salt addition and exposure time were investigated and optimized. Finally, the enrichment factor, dynamic linear range (DLR), limit of detection (LOD) and precision of the method were evaluated by the water samples spiked with organophosphorus pesticides. Using optimum extraction conditions, very low detection limits (0.01-0.04 μg L⁻¹) and good linearities (0.9983 < r² < 0.9999) were achieved. The LPME was performed for determination of organophosphorus pesticides in different types of natural water samples and acceptable recoveries (96-104%) and precisions (3.5 < R.S.D.% < 8.9) were obtained. The results suggested that the newly proposed LPME method is a rapid, accurate and effective sample preparation method and could be successfully applied for extraction and determination of organophosphorus pesticides in water samples.     

Novel fiber coated with β-cyclodextrin derivatives used for headspace solid-phase microextraction of ephedrine and methamphetamine in human urine

Heptakis (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) blending with hydroxy-terminated silicone oil (OH-TSO) coated solid-phase microextraction (SPME) fiber (DM-β-CD/OH-TSO) was first prepared with sol-gel technology and applied to headspace SPME for analysis of ephedrine (EP) and methamphetamine (MA) in human urine by gas chromatography (GC). By exploiting the advantages of the unique cavity-shaped cyclic molecular structure of CD and the superiorities of sol-gel coating technique, the novel fiber showed desirable extraction ability and operational stability. Influence of relevant experimental parameters (extraction time, extraction temperature, basicity, ionic strength, etc.) was systematically investigated. In the optimal conditions the proposed headspace SPME-GC method provided good linearity over four orders of magnitude with limit of detection (LOD) of ng/ml (0.33 ng/ml for EP, 0.60 ng/ml for MA). The recoveries of EP and MA in urine were 98.0% and 98.2%. And the relative standard deviations (R.S.D., n = 6) for EP and MA were 3.9% and 5.0%, respectively.     

Headspace solvent microextraction: a very rapid method for identification of volatile components of Iranian Pimpinella anisum seed

At the present study, a new and rapid headspace solvent microextraction (HSME), for the extraction and pre-concentration of the volatile components of plant sample into a microdrop was applied. The extraction occurred by suspending a microliter drop of the solvent from the tip of a microsyringe to the headspace of a ripen and powdered dry fruit sample (Iranian Pimpinella anisum seed) in a sealed vial for a preset extraction time, then the microdrop was retracted back into the microsyringe and injected directly into a GC injection port. The chemical composition of the HSME extracts were confirmed according to their retention indexes and mass spectra (EI, 70 eV); and quantitative analysis was performed by GC-FID.Parameters such as the nature of the extracting solvent, particle size of the sample, temperatures of the microdrop and sample, volume of sample and the extraction time were studied and optimized, and the method's performance was evaluated. The optimized conditions were: sample particle size, 1 mm; sample volume, 5 ml (in a 15 ml vial); sample temperature, 60 °C; microsyringe needle temperature, 0 °C; and extraction time, 10 min. Finally, accordingly, the percentage of trans-anethole (the major compound of P. anisum) and the relative standard deviation for extraction and determination of trans-anethole (seven-replicated analysis) were determined to be 90% and 3.9%, respectively.     

Gas flow headspace liquid phase microextraction

There is a trend towards the use of enrichment techniques such as microextraction in the analysis of trace chemicals. Based on the theory of ideal gases, theory of gas chromatography and the original headspace liquid phase microextraction (HS-LPME) technique, a simple gas flow headspace liquid phase microextraction (GF-HS-LPME) technique has been developed, where the extracting gas phase volume is increased using a gas flow. The system is an open system, where an inert gas containing the target compounds flows continuously through a special gas outlet channel (D = 1.8 mm), and the target compounds are trapped on a solvent microdrop (2.4 μL) hanging on the microsyringe tip, as a result, a high enrichment factor is obtained. The parameters affecting the enrichment factor, such as the gas flow rate, the position of the microdrop, the diameter of the gas outlet channel, the temperatures of the extracting solvent and of the sample, and the extraction time, were systematically optimized for four types of polycyclic aromatic hydrocarbons. The results were compared with results obtained from HS-LPME. Under the optimized conditions (where the extraction time and the volume of the extracting sample vial were fixed at 20 min and 10 mL, respectively), detection limits (S/N = 3) were approximately a factor of 4 lower than those for the original HS-LPME technique. The method was validated by comparison of the GF-HS-LPME and HS-LPME techniques using data for PAHs from environmental sediment samples.     

Optimization of a single-drop microextraction procedure for the determination of organophosphorus pesticides in water and fruit juice with gas chromatography-flame photometric detection

A single-drop microextraction (SDME) procedure was developed for the analysis of organophosphorus pesticides (OPPs) in water and fruit juice by gas chromatography (GC) with flame photometric detection (GC-FPD). The significant parameters affecting the SDME performance such as selection of microextraction solvent, solvent volume, extraction time, stirring rate, sample pH and temperature, and ionic strength were studied and optimized. Two types of SDME mode, static and cycle-flow SDME, were evaluated. The static SDME procedure provided more sensitive analysis of the target analytes. Therefore, static SDME with tributyl phosphate (TBP) as internal standard was selected for the real sample analysis. The limits of detection (LODs) in water for the six studied compounds were between 0.21 and 0.56 ng/mL with the relative standard deviations ranging from 1.7 to 10.0%. Linear response data was obtained in the concentration range of 0.5-50 ng/mL (except for dichlorvos 1.0-50 ng/mL) with correlation coefficients from 0.9995 to 0.9999. Environmental water sample collected from East Lake and fruit juice samples were successfully analyzed using the proposed method, but none of the analytes in both lake water and fruit juice were detected. The recoveries for the spiked water and juice samples were from 77.7 to 113.6%. Compared with the conventional methods, the proposed method enabled a rapid and simple determination of organophosphorus pesticides in water and fruit juice with minimal solvent consumption and a higher concentration capability.     

Ultra trace analysis of 17 organochlorine pesticides in water samples from the Arctic based on the combination of solid-phase extraction and headspace solid-phase microextraction–gas chromatography-electron-capture detector

Solid-phase extraction (SPE) was combined with headspace solid-phase microextraction (HS-SPME) for the highly effective enrichment of 17 ultra trace organochlorine pesticides in water samples. The target compounds were successfully transferred from water samples to a gas chromatography capillary column by means of four consecutive steps, namely SPE, solvent conversion, HS-SPME, and thermal desorption of the SPME fiber. Parameters, including elution volume and breakthrough volume in the SPE step, temperature in the solvent conversion step, and fiber type, ionic strength, extraction temperature, extraction time, and pH in the SPME step were optimized to improve the performance of the method through either single factor comparative experiment or the orthogonal experimental design approach. After optimization, the method gave high sensitivity with a method detection limit ranging from 0.0018 to 0.027 ng L⁻¹, good repeatability with a relative standard deviation less than 20% (n = 4) and acceptable recovery with a value mostly exceeding 60%. External standard calibration was employed for the quantification, and a wide linear range (from 0.0010 to 60 ng mL⁻¹) with R² values ranging from 0.9988 to 0.9999 were observed. In the end, the method was successfully applied to the Arctic samples, and the results showed that, among all the organochlorine pesticides, hexachlorocyclohexanes (HCHs) were the most predominant in the Arctic surface water body with sum of their concentrations ranging from 0.262 to 3.156 ng L⁻¹.     

Analysis of hexachlorocyclohexanes in aquatic samples by one-step microwave-assisted headspace controlled-temperature liquid-phase microextraction and gas chromatography with electron capture detection

A microwave-assisted headspace controlled-temperature liquid-phase microextraction (HS-CT-LPME) technique was applied for the one-step sample extraction of hexachlorocyclohexanes (HCHs) from aqueous samples with complicate matrices, followed by gas chromatographic (GC) analysis with electron capture detector (ECD). Microwave heating was applied to accelerate the evaporation of HCHs into the headspace and an external-cooling system was used to control the temperature in the sampling zone for HS-LPME. Parameters affecting extraction efficiency, such as LPME solvent, sampling position and temperature, microwave power and irradiation time (the same as sampling time), sample pH, and salt addition were thoroughly investigated. From experimental results, the following conditions were selected for the extraction of HCHs from 10-mL water sample (pH 2.0) by using 1-octanol as the LPME solvent, with sampling done at 38 °C for 6 min under 167 W of microwave irradiation. The detections were linear in the concentration of 0.1–10 μg/L for α-HCH and γ-HCH, and 1–100 μg/L for β-HCH and δ-HCH. Detection limits were 0.05, 0.4, 0.03 and 0.1 μg/L for α-, β-, γ- and δ-HCH, respectively. Environmental water samples were analyzed with recovery between 86.4% and 102.4% for farm-field water, and between 92.2% and 98.6% for river water. The proposed method proved to serve as a simple, rapid, sensitive, inexpensive, and eco-friendly procedure for the determination of HCHs in aqueous samples.     

Application of headspace single-drop microextraction coupled with gas chromatography for the determination of short-chain fatty acids in RuO4 oxidation products of asphaltenes

In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography-flame ionization detection (GC-FID), was employed to determine short-chain fatty acids (SCFAs) in ruthenium tetroxide (RuO₄) oxidation products of asphaltenes. Several significant parameters, such as drop solvent type, drop volume, sample solution ionic strength, agitation speed, extraction time, and ratio of headspace volume to sample volume were optimized. Under optimum extraction conditions (i.e., a 3-μL drop of 1-butanol, 20 min exposure to the headspace of a 6 mL aqueous sample placed in a 10 mL vial, stirring at 1000 rpm at room temperature, and 30% (w/v) NaCl content), the reproducibility and accuracy of the method have been tested and found to be satisfactory. The analysis of a real asphaltene sample using this method proved that HS-SDME can be a promising tool for the determination of volatile SCFAs in complex matrices.     

Extraction of pesticides in water samples using vortex-assisted liquid–liquid microextraction

A simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-μECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30 μL toluene used as extraction solvent were directly injected into a 25 mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835–1115 and limits of detection below 0.010 μg L⁻¹ were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r²) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5 μg L⁻¹. Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72–106.3% were obtained.     

Determination of haloethers in water with dynamic hollow fiber liquid-phase microextraction using GC-FID and GC-ECD

Dynamic hollow fiber liquid-phase microextraction (HF-LPME) coupled with gas chromatography with flame ionization detection (GC-FID) and GC-electron capture detecion (GC-ECD) was used for quantification of toxic haloethers in lake water. The analytes were extracted from 5 ml of aqueous sample using 4 μl of organic solvent through a porous polypropylene hollow fiber. The effects on extraction performance of solvent selection, agitation rate, extraction time, extraction temperature, concentration of salt added and volumes of solvent for extraction and injection were optimized. The proposed method provided a good average enrichment factor of up to 231-fold, reasonable reproducibility ranging from 9 to 12% (n = 3), and good linearity (R² ≧ 0.9973) for spiked water samples. Method detection limits (MDLs) ranged from 0.55 to 4.30 μg/l for FID and 0.11-0.34 μg/l for ECD (n = 7).     

Solvent-bar microextraction—Using a silica monolith as the extractant phase holder

In this paper, a novel liquid-phase microextraction (LPME) approach, based on solvent-bar microextraction (SBME), was developed in which a silica monolith was used as the extractant solvent holder. Owing to the porous nature of the monolith, the extractant solvent could be easily held in the material; when the monolith containing the extractant solvent was exposed to the sample solution, analytes could directly diffuse from the sample solution into the extractant solvent. Polycyclic aromatic hydrocarbons (PAHs) were used as model analytes to evaluate the procedure. Through the investigation of the effect of agitation speed, extraction time, length of the monolith (that determined the volume of organic extractant solvent) and salt concentration on extraction efficiency, the following optimal extraction conditions were obtained: stirring at 1000 rpm for 30 min without salt addition using a 4-mm silica monolith. The limits of detection ranged from 3.9 pg/mL to 28.8 pg/mL, with relative standard deviations of between 8.16% and 10.5% on the same silica monolith. The linearity was 0.05–200 ng/mL for fluoranthene and pyrene, and 0.5–200 ng/mL for chrysene and benzo[b]fluoranthene, with acceptable correlation coefficient. When this method was applied for the spiked real river sample, the relative recoveries ranged from 87.1% to 100.7% for the tested PAHs. This method was also compared to polymeric hollow fiber-based SBME and hollow fiber-protected LPME and found to provide better results. Additionally, compared with the polymeric hollow fiber, the silica monolith possesses good resistance to extreme conditions, such as high temperature and pH, and is more compatible with various organic solvents. This is the first report of an application of a monolithic material for LPME, and as a solvent holder for SBME. It extends the scope of applications of such materials, to analytical chemistry, specifically to sample preparation.     

Headspace liquid-phase microextraction of trihalomethanes in drinking water and their gas chromatographic determination

In the present work, a novel method for the determination of trihalomethanes (THMs) such as chloroform, dichlorobromomethane, chlorodibromomethane and bromoform in drinking water has been described. It is based on coupling headspace liquid-phase microextraction (HS-LPME) with gas chromatography-electron capture detector (GC-ECD). A microdrop of organic solvent at the tip of a commercial microsyringe was used to extract analytes from aqueous samples. Three organic solvents—xylene, ethylene glycol and 1-octanol—were compared and 1-octanol was the most sensitive solvent for the analytes. Extraction conditions such as headspace volume, extraction time, stirring rate, content of NaCl and extraction temperature were found to have significant influence on extraction efficiency. The optimized conditions were 15 ml headspace volume in a 40 ml vial, 10 min extraction time and 800 rpm stirring rate at 20 °C with 0.3 g ml⁻¹ NaCl. The linear range was 1-100 μg l⁻¹ for THMs. The limits of detection (LODs) ranged from 0.15 μg l⁻¹ (for dichlorobromomethane and chlorodibromomethane) to 0.4 μg l⁻¹ (for chloroform); and relative standard deviations (RSD) for most of THMs at the 10 μg l⁻¹ level were below 10%. Real samples collected from tap water and well water were successfully analyzed using the proposed method. The recovery of spiked water samples was from 101 to 112%.     

Solid-phase microextraction coupled with capillary electrophoresis to determine ephedrine derivatives in water and urine using a sol-gel derived butyl methacrylate/silicone fiber

A sensitive method for determination of ephedrine derivatives using headspace solid-phase microextraction (SPME) with a novel fiber followed by capillary electrophoresis has been developed. The co-poly(butyl methacrylate/hydroxy-terminated silicone oil) (BMA/OH-TSO) was used as stationary phases with the aid of γ-methacryloxypropyltrimethoxysilane (KH-570) as bridge in SPME using sol-gel-coating method and cross-linking technology. It has high extraction efficiency for ephedrine derivatives in comparison with commercial poly(dimethylsiloxane) and poly(acrylate)-coated fiber. The coating exhibits good thermal and solvent stability as well as long lifetime. A simple and flexible device for desorption of analytes after headspace SPME was constructed. The effect of various experimental parameters for SPME (temperature, time, pH, ionic strength, desorption solvent, etc.) were discussed. Field amplified sample injection (FASI) was applied for on-line sample concentration and a sensitivity enhancement of two orders of magnitude was achieved. Linear ranges were found to be 20-5000 ng/ml. The detection limits for (1R,2S)-ephedrine, (1R,2R)-pseudoephedrine and (1S,2S)-pseudoephedrine were 3, 5 and 5 ng/ml, respectively. Relative standard deviation (n = 6) was found to be 4.96-7.57%. The method was successfully applied to the analysis of ephedrine derivatives in human urine.     

Determination of 7-aminoflunitrazepam in urine by dispersive liquid-liquid microextraction with liquid chromatography-electrospray-tandem mass spectrometry

Dispersive liquid-liquid microextraction (DLLME) and liquid chromatography-electrospray-tandem mass spectrometry (LC-ES-MS/MS) procedure was presented for the extraction and determination of 7-aminoflunitrazepam (7-aminoFM2), a biomarker of the hypnotic flunitrazepam (FM2) in urine sample. The method was based on the formation of tiny droplets of an organic extractant in the sample solution using water-immiscible organic solvent [dichloromethane (DCM), an extractant] dissolved in water-miscible organic dispersive solvent [isopropyl alcohol (IPA)]. First, 7-aminoFM2 from basified urine sample was extracted into the dispersed DCM droplets. The extracting organic phase was separated by centrifuging and the sedimented phase was transferred into a 300 μl vial insert and evaporated to dryness. The residue was reconstituted in 30 μl mobile phase (20:80, acetonitrile:water). An aliquot of 20 μl as injected into LC-ES-MS/MS. Various parameters affecting the extraction efficiency (type and volume of extraction and dispersive solvent, effect of alkali and salt) were evaluated. Under optimum conditions, precision, linearity (correlation coefficient, r² = 0.988 over the concentration range of 0.05-2.5 ng/ml), detection limit (0.025 ng/ml) and enrichment factor (20) had been obtained. To our knowledge, DLLME was applied to urine sample for the first time.     

Determination of ethoprop, diazinon, disulfoton and fenthion using dynamic hollow fiber-protected liquid-phase microextraction coupled with gas chromatography-mass spectrometry

A technique for the analysis of organophosphorus pesticides (ethoprop, diazinon, disulfoton, fenthion) in aqueous sample using liquid-phase microextraction (LPME), coupled with gas chromatography-mass spectrometry (GC-MS) was developed. A small section of a hollow fiber inserted into the needle of GC syringe and filled with the 3.5 μl of organic solvent was used to extract pesticides from a 20 ml aqueous sample. The limits of detection (LOD) with the selected ion monitoring (SIM) mode varied from 0.2 to 0.006 μg/l. The calibration curves were linear over three orders of magnitude with R² ≥ 0.996. The relative standard deviations of the analysis (inter- and intra-day) were 5-8%, and the relative recoveries from the lake water sample were greater than 83%. The results were compared with results obtained using solid-phase microextraction (SPME/GC/MS).