Application of solvent microextraction to the analysis of nitroaromatic explosives in water samples

The application of solvent microextraction to the analysis of nitroaromatic explosives is presented. Extraction of 11 nitroaromatics was achieved by suspending 1 microl of organic solvent to the tip of a microsyringe in a stirred aqueous solution. Parameters such as extraction solvent, stirring rate, salt concentration and sampling time were studied and optimized. The limits of detection using bench-top quadrupole mass spectrometry and short extraction times (15 min) were found to be between 0.08 and 1.3 microg/l and the relative standard deviations ranged between 4.3 and 9.8%. Although precision and accuracy of quantification of the method are still needed, solvent microextraction proved to be a fast, simple and inexpensive tool for preconcentration and matrix isolation of nitroaromatics on a microscale.     

Headspace single-drop microextraction for the analysis of chlorobenzenes in water samples

Exposing a microlitre organic solvent drop to the headspace of an aqueous sample contaminated with ten chlorobenzene compounds proved to be an excellent preconcentration method for headspace analysis by gas chromatography-mass spectrometry (GC-MS). The proposed headspace single-drop microextraction (SDME) method was initially optimised and the optimum experimental conditions found were: 2.5 microl toluene microdrop exposed for 5 min to the headspace of a 10 ml aqueous sample containing 30% (w/v) NaCl placed in 15 ml vial and stirred at 1000 rpm. The calculated calibration curves gave a high level of linearity for all target analytes with correlation coefficients ranging between 0.9901 and 0.9971, except for hexachlorobenzene where the correlation coefficient was found to be 0.9886. The repeatability of the proposed method, expressed as relative standard deviation varied between 2.1 and 13.2% (n = 5). The limits of detection ranged between 0.003 and 0.031 microg/l using GC-MS with selective ion monitoring. Analysis of spiked tap and well water samples revealed that matrix had little effect on extraction. A comparative study was performed between the proposed method, headspace solid-phase microextraction (SPME), solid-phase extraction (SPE) and EPA method 8121. Overall, headspace SDME proved to be a rapid, simple and sensitive technique for the analysis of chlorobenzenes in water samples, representing an excellent alternative to traditional and other, recently introduced, methods.     

Solid-phase microextraction for the analysis of short-chain chlorinated paraffins in water samples

A novel solid-phase microextraction (SPME) method coupled to gas chromatography with electron capture detection (GC-ECD) was developed as an alternative to liquid-liquid and solid-phase extraction for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples. The extraction efficiency of five different commercially available fibres was evaluated and the 100-microm polydimethylsiloxane coating was the most suitable for the absorption of the SCCPs. Optimisation of several SPME parameters, such as extraction time and temperature, ionic strength and desorption time, was performed. Quality parameters were established using Milli-Q, tap water and river water. Linearity ranged between 0.06 and 6 microg l(-1) for spiked Milli-Q water and between 0.6 and 6 microg l(-1) for natural waters. The precision of the SPME-GC-ECD method for the three aqueous matrices was similar and gave relative standard deviations (RSD) between 12 and 14%. The limit of detection (LOD) was 0.02 microg l(-1) for Milli-Q water and 0.3 microg l(-1) for both tap water and river water. The optimised SPME-GC-ECD method was successfully applied to the determination of SCCPs in river water samples.     

Use of single-drop microextraction for determination of fentanyl in water samples

Fentanyl is a very potent synthetic narcotic analgesic. Because of its strong sedative properties, it has become an analogue of illicit drugs such as heroin. Its unambiguous detection and identification in environmental samples can be regarded as strong evidence of its illicit preparation. In this paper we report application of single-drop microextraction (SDME) for analysis of water samples spiked with fentanyl. Experimental conditions which affect the performance of SDME, for example the nature of the extracting solvent, sample stirring speed, extraction time, ionic strength, and solution pH, were optimized. The method was found to be linear in the concentration range 0.10–10 ng mL⁻¹. The limits of quantitation and detection of the method were 100 pg mL⁻¹ and <75 pg mL⁻¹, respectively. This technique is superior to other sample-preparation techniques because of the simple experimental set-up, short analysis time, high sensitivity, and minimum use of organic solvent.     

Determination of nitroaromatic explosives in water samples by direct ultrasound-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry

A fast, simple, inexpensive, sensitive, efficient and environmental friendly direct ultrasound-assisted dispersive liquid-liquid microextraction (DUSA-DLLME) procedure has been developed to concentrate five nitroaromatic explosives from water samples prior to quantification by gas chromatography-mass spectrometry (GC-MS). An efficient ultrasonic probe has been used to radiate directly the samples producing very fine emulsions from immiscible liquids. A D-optimal design was used for optimizing the factors and to evaluate their influential upon extraction. The optimum experimental conditions were: sample volume, 10 mL; extraction time, 60 s; cycles, 0.6 s(s⁻¹); power of ultrasound energy, 40% (70 W); and, extractant solvent (chlorobenzene) volume, 20 μL. Under the optimized experimental conditions the method presents good level of repeatability with coefficients of variation under 6% (n = 8; spiking level 10 μg L⁻¹). Calculated calibration curves gave high level of linearity with correlation coefficient values between 0.9949 and 0.9992. Limits of detection were ranged between 0.03 and 0.91 μg L⁻¹. Finally, the proposed method was applied to the analysis of two types of water samples, reservoir and effluent wastewater. The samples were previously analysed and confirmed free of target analytes. At 5 μg L⁻¹ spiking level recovery values ranged between 75 and 96% for reservoir water sample showing that the matrix had a negligible effect upon extraction. However, a noticeable matrix effect (around 50% recovery) was observed for effluent wastewater sample. In order to alleviate this matrix effect, the standard addition calibration method was used for quantitative determination. This calibration method supplied recovery values ranged between 71 and 79%. The same conclusions have been obtained from an uncertainty budget evaluation study.     

Solid-phase microextraction with on-fiber derivatization for the analysis of anti-inflammatory drugs in water samples

A sensitive and solvent-free procedure for the determination of non-steroidal acidic anti-inflammatory drugs in water samples was optimized using solid-phase microextraction (SPME) followed by on-fiber silylation of the acidic compounds and gas chromatography-mass spectrometry (GC-MS) determination. Microextraction was carried out directly over the filtered water samples using a polyacrylate fiber. Derivatization was performed placing the SPME fiber, loaded with the extracted analytes, in the headspace of a vial containing 50 microl of N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Derivatives were desorbed for 3 min in the GC injector. Influence of several parameters in the efficiency of microextraction (volume of sample, time, pH, type of fiber coating, etc.) and derivatization steps (time, temperature and volume of MTBSTFA) was systematically investigated. In the optimal conditions an excellent linearity over three orders of magnitude and quantification limits at the ng/l level (from 12 to 40 ng/l) were achieved. The proposed method was applied to the determination of acidic compounds in sewage water and results compared to those obtained using solid-phase extraction (SPE) followed by the derivatization of the compounds in the organic extract of the solid-phase extraction cartridge.     

Determination of decabromodiphenyl ether in water samples by single-drop microextraction and RP-HPLC

This paper describes the development of a new method using single-drop microextraction (SDME) and RP-HPLC for the determination of decabromodiphenyl ether (BDE-209) in water samples. The effects of SDME parameters such as extraction solvent, microdrop volume, extraction time, stirring speed, salt concentration, and sample pH on the extraction performance are investigated. Under optimal extraction conditions (extraction solvent, toluene; solvent drop volume, 3.0 microL; extraction time, 15 min; stirring speed, 600 rpm; no addition of salt and change of sample pH), the calibration curve was drawn by plotting peak area against a series of BDE-209 concentrations (0.001-1 microg/mL) in aqueous solution; the correlation coefficient (r) was 0.9998. The limit of detection was 0.7 ng/mL. The enrichment factor was 10.6. The precision of this method was obtained by six successive analyses of a 100 ng/mL standard solution of BDE-209, and RSD was 4.8%. This method was successfully applied to the extraction of BDE-209 from tap and East Lake water samples with relative recoveries ranging from 92.5 to 102.8% and from 91.5 to 96.2%, respectively, and the relative standard deviations (n = 3) were 4.4 and 2.2%. The proposed method is acceptable for the analysis of BDE-209 in water samples.     

单滴微萃取-气相色谱-质谱联用测定水中的硝基咪唑类药物

建立了单滴液相微萃取(SDME)与气相色谱-质谱(GC-MS)联用技术快速检测水中的硝基咪唑类药物,对影响萃取的因素(溶剂的种类及用量、萃取时间、萃取温度及搅拌子的搅拌速度)进行优化。优化的萃取条件为:溶剂为2.5μL正辛醇,温度为50℃,搅拌速度为600 r/min,时间为20 min。萃取后,微液滴转移至衍生化试管,于70℃水浴中衍生45 min,进样分析。该方法在水中的线性范围为0.5~400μg/L,线性相关系数良好(r0.998),检测限为0.16~0.57μg/L。加标自来水和湖水中的相对平均回收率为80.9%~103.6%,相对标准偏差为1.7%~9.0%。     

Solid-phase microextraction with micellar desorption and HPLC-fluorescence detection for the analysis of fluoroquinolones residues in water samples

A sensitive and useful method based on solid-phase microextraction with micellar desorption (SPME-MD) coupled to HPLC with fluorescence detection was developed for the determination of five fluoroquinolones (levofloxacin, norfloxacin, ciprofloxacin, enrofloxacin, and sarafloxacin) in environmental water matrices. The SPME extraction efficiency was optimized with regard to time, temperature, pH, and ionic strength using a CW-TPR fiber. A detailed study about the optimum conditions for micellar desorption (surfactant type, concentration, and desorption time) were made. Among different surfactants studied, Polyoxyethylene 10 lauryl ether showed the best responses to extract fluoroquinolones using SPME-MD. Relative standard deviations of the developed method were below 9%. Limits of detection and quantification were between 0.01–0.2 and 0.03–0.6 ng mL⁻¹, respectively. The recoveries achieved for all five compounds were in the 81–116% range. The proposed method was compared using conventional desorbing agent as methanol. Finally, the SPME-MD methodology was applied to the determination of these target analytes in several environmental liquid samples, including seawater, groundwater, and wastewater samples with excellent results.     

Solid-phase microextraction method for the quantitative analysis of styrene in water

A headspace solid-phase microextraction (HS-SPME) method is developed for the determination of styrene in drinking water. Gas chromatography (GC)-mass spectrometry is utilized for qualitative analysis. A manual SPME holder with 85-microm polyacrylate coating is used to extract the styrene from water, which is determined to have good linearity (correlation coefficient r = 0.9999 for 1.00-100.00 microg/L range), a relative standard deviation of 1.9%, and a detection limit of 0.30 microg/L. This method is compared with a classical headspace GC method.     

Solid-phase microextraction and chromatography of water samples containing aromatic compounds

A concentrator was designed for solid-phase microextraction of aromatic compounds (benzene, toluene, ethylbenzene, o-xylene) from water samples. The concentrator was used as an attachment to a water vapor mobile phase chromatograph with a detection limit (compounds <1 μg/l).     

Solid-phase microextraction for herbicide determination in environmental samples

Liquid-liquid extraction or solid-phase extraction followed by gas chromatography (GC) or high-performance liquid chromatography are traditional herbicide residue determination methods for environmental samples. Solid-phase microextraction (SPME) is a solventless, fast, and sensitive alternative herbicide residue extraction method that can be applied to numerous environmental matrices. The objective of this paper was to review SPME literature regarding extraction theory, extraction modes, fiber types, and method optimization in conjunction with present and future SPME applications for herbicide determination in environmental samples.     

Improved single-drop microextraction for high sensitive analysis

This paper described a simple approach to prepare a small bell-mouthed extraction device for single-drop microextraction (SDME). Analytical sensitivity was improved by increasing the suspended acceptor volume. Because of the increased contact area and the rough inner surface of the extraction device, the stability of drop was markedly increased. The merits of the proposed method were demonstrated by using 1-octanol as extractant and with cyanazine, simazine and atrazine as model compounds. The related parameters and the effect of humic acid were systematically investigated. Under the optimized extraction conditions, the linear range, detection limit (S/N=3) and precision (RSD, n=6) were 0.2-50, 0.06microgL-1, 5.7% for cyanazine, 0.1-25, 0.03microgL-1, 6.7% for simazine, and 0.15-37.5, 0.04microgL-1, 5.0% for atrazine, respectively. The established method was applied to determine the target compounds in four real water samples, and the satisfactory spiked recoveries at two concentration levels were obtained. Moreover, the comparison of the proposed SDME with the traditional SDME was performed. These results indicated that the proposed improvement made SDME be a competitive analytical tool and an alternative of the traditional methods for the analysis of organic pollutants at trace level.     

Dispersive liquid-liquid microextraction versus single-drop microextraction for the determination of several endocrine-disrupting phenols from seawaters

Two liquid-phase microextraction procedures: single-drop microextraction (SDME) and dispersive liquid-liquid microextraction (DLLME), have been developed for the determination of several endocrine-disrupting phenols (EDPs) in seawaters, in combination with high-performance liquid chromatography (HPLC) with UV detection. The EDPs studied were bisphenol-A, 4-cumylphenol, 4-tertbutylphenol, 4-octylphenol and 4-n-nonylphenol. The optimized SDME method used 2.5 μL of decanol suspended at the tip of a micro-syringe immersed in 5 mL of seawater sample, and 60 min for the extraction time. The performance of the SDME is characterized for average relative recoveries of 102 ± 11%, precision values (RSD) < 9.4% (spiked level of 50 ng mL⁻¹), and detection limits between 4 and 9 ng mL⁻¹. The optimized DLLME method used 150 μL of a mixture acetonitrile:decanol (ratio 15.7, v/v), which is quickly added to 5 mL of seawater sample, then subjected to vortex during 4 min and centrifuged at 2000 rpm for another 5 min. The performance of the DLLME is characterized for average relative recoveries of 98.7 ± 3.7%, precision values (RSD) < 7.2% (spiked level of 20 ng mL⁻¹), and detection limits between 0.2 and 1.6 ng mL⁻¹. The efficiencies of both methods have also been compared with spiked real seawater samples. The DLLME method has shown to be a more efficient approach for the determination of EDPs in seawater matrices, presenting enrichment factors ranging from 123 to 275, average relative recoveries of 110 ± 11%, and precision values (RSD) < 14%, when using a real seawaters (spiked level of 3.5 ng mL⁻¹).     

A new poly(phthalazine ether sulfone ketone)-coated fiber for solid-phase microextraction to determine nitroaromatic explosives in aqueous samples

A novel polar solid-phase microextraction (SPME) fiber coated with poly(phthalazine ether sulfone ketone) (PPESK) was prepared by immersion precipitation technique. The microstructure of the coating exhibits a sponge-like sublayer supporting a dense cracking shaped top layer (about 1 microm in thickness). This coating shows long lifetime (up to 100 times) and is stable at desorption temperature up to 290 degrees C due to the rigid aromatic rings in chemical structure. We evaluated the extraction-desorption properties of the PPESK fiber for nitroaromatic explosives in aqueous samples. The parameters affecting the extraction were optimized, including extraction temperature and time, salt addition, desorption temperature and time. Limits of detection (LOD), precisions and linear dynamic range for the analysis of explosives by SPME-GC/TSD or ECD were evaluated. Limits of detection of the new fiber was three orders of magnitude lower than those with carbowax/divinylbenzene (CW/DVB), and the relative standard deviation (RSD) of single fiber and fiber-to-fiber were less than 9.3 and 10.4%, respectively. The results demonstrated that the PPESK coating exhibited high extraction efficiency for nitroaromatic compounds due to the pi-pi interaction, dipole-dipole interactions and interactions by polar functional groups. The method was applied to the analysis of nitroaromatic explosives in real aqueous samples including seawater and groundwater samples, with relative recoveries better than 90.7%.     

Solid-phase microextraction for the determination of iodinated trihalomethanes in drinking water.

A headspace solid-phase microextraction (HS-SPME) method has been developed for the determination of iodinated trihalomethanes (ITHMs) in treated water samples. Mixed THMs (bromochloroido-, bromodiiodo-, chlorodiiodo-, dibromoiodo- and dichloroiodo-) were previously synthesized since commercial standards are not available. HS-SPME has shorter equilibration times than direct SPME, a cleaner background and a longer fiber life. Experimental parameters such as the selection of SPME coatings, sample volume, extraction time and addition of salts were studied. The Carbowax-divinylbenzene fiber appears to be the most suitable for the determination of ITHMs. Analytical parameters such as linearity, limit of detection and precision were also evaluated. HS-SPME was compared to liquid-liquid microextraction for the analyses of spiked treated water samples, obtaining a good agreement. It is concluded that HS-SPME has a great potential for drinking water analysis.     

Solid-phase microextraction and headspace solid-phase microextraction for the determination of high molecular-weight polycyclic aromatic hydrocarbons in water and soil samples

The feasibility of direct-immersion (DI) solid-phase microextraction (SPME) and headspace (HS) SPME for the determination of high-ring polycyclic aromatic hydrocarbons (PAHs) (4- to 6-ring PAHs) in water and soil samples is studied. Three SPME fibers--100- and 30-microm polydimethylsiloxane (PDMS) and 85-microm polyacrylate (PA) fibers-are compared for the effective extraction of PAHs. Parameters affecting the sorption of PAHs into the fiber such as sampling time, sampling volume, and temperature are also evaluated. The extracted amounts of high-ring PAHs decrease with the decreasing of film thickness, and the 100-microm PDMS has the highest extraction efficiency than 85-microm PA and 30-microm PDMS fibers. Also, the extraction efficiency decreases with the increasing molecular weights of PAHs. Of the 10 high-ring PAHs, only fluoranthene and pyrene can reach equilibrium within 120 min at 25 degrees C for DI-SPME in a water sample. Increasing the temperature to 60 degrees C can increase the sensitivity of PAHs and shorten the equilibrium time. A 0.7- to 25-fold increase in peak area is obtained for DI-SPME when the working temperature is increased to 60 degrees C. For HS-SPME, the extraction efficiency of PAHs decrease when the headspace volume of the sampling system increases. All high-ring PAHs can be detected in a water sample by increasing the temperature to 80 degrees C. However, only 4- and 5-ring PAHs can be quantitated in a CRM soil sample when HS-SPME is used. The addition of a surfactant with high hydrophilic property can effectively enhance the sensitivity of high-ring PAHs. HS-SPME as well as DI-SPME with 100-microm PDMS or 85-microm PA fibers are shown to be suitable methods for analyzing high-ring PAHs in a water sample; however, this technique can only apply in a soil sample for PAHs having up to 5 rings.     

基于离子液体的单滴微萃取-毛细管电泳在线联用测定水体中3种溴酚类化合物

建立了基于离子液体的单滴微萃取-毛细管电泳联用测定溴酚类化合物的方法。考察了萃取剂种类与体积、萃取时间、有机溶剂、盐浓度及萃取温度对萃取效率的影响。确定了最佳萃取条件为:以1-丁基-3-甲基咪唑六氟磷酸盐([C₄MIM]PF₆])离子液体作为萃取剂,萃取时间为8 min,样品溶液中NaCl浓度为10%(质量分数),萃取温度为20 ℃。在最佳条件下,3种溴酚(4-溴酚、2,6-二溴酚和2,4,6-三溴酚)在1~100 mg/L范围内呈良好的线性关系,线性相关系数为0.9939~0.9988;检出限为0.3 mg/L (S/N=3);该方法对3种溴酚的富集倍数分别为115.8、327.0和569.8; 6次平行测定的相对标准偏差为5.21%~6.47%;对本地区自来水、河水和湖水的加标回收率为87.8%~96.7%。结果表明,该方法稳定可靠,适合于水体中溴酚类污染物的测定。     

Headspace single-drop microextraction with in-drop derivatization for aldehyde analysis

A new technique, headspace single-drop microextraction (HS-SDME) with in-drop derivatization, was developed. Its feasibility was demonstrated by analysis of the model compounds, aldehydes in water. A hanging microliter drop of solvent containing the derivatization agent of O-2,3,4,5,6-(pentaflurobenzyl)hydroxylamine hydrochloride (PFBHA) was shown to be an excellent extraction, concentration, and derivatization medium for headspace analysis of aldehydes by GC-MS. Using the microdrop solvent with PFBHA, acetaldehyde, propanal, butanal, hexanal, and heptanal in water were headspace extracted and simultaneously derivatized. The formed oximes in the microdrop were analyzed by GC-MS. HS-SDME and in-drop derivatization parameters (extraction solvent, extraction temperature, extraction time, stirring rate microdrop volume, and the headspace volume) and the method validations (linearity, precision, detection limit, and recovery) were studied. Compared to liquid-liquid extraction and solid-phase microextraction, HS-SDME with in-drop derivatization is a simple, rapid, convenient, and inexpensive sample technique.