Analysis of semi-volatile organic compounds in aqueous samples by microwave-assisted headspace solid-phase microextraction coupled with gas chromatography-electron capture detection

The pretreatment technique of microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) has been developed and studied for the extraction of semi-volatile organic compounds (SVOCs) in aqueous samples prior to chromatographic analysis. The optimum conditions for obtaining extraction efficiency, such as the extraction time, extraction temperature, addition of salts, and the ratio of sample to headspace volume parameters were investigated. Experimental results indicated that the proposed MA-HS-SPME technique attained the best extraction efficiency under the optimized conditions, i.e., irradiation of extraction solution (20mL aqueous sample in 40mL headspace vial with no addition of salt) under 30W microwave power for 30min at 70 degrees C. The detection was linear at 1-250ng/L with correlation coefficient exceeding 0.997. The detection limits obtained were between 0.2-10.7ng/L, repeatability range from 2 to 15%. Real water samples collected from known sites in southern Taiwan were analyzed using the optimized conditions.     

Determination of amphetamine and methamphetamine in serum via headspace derivatization solid-phase microextraction-gas chromatography-mass spectrometry

This study evaluates solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to determine trace levels of amphetamine and methamphetamine in serum. Headspace post-derivatization in a laboratory-made design with heptafluorobutyric anhydride vapor following SPME was compared with that without derivatization SPME. The SPME experimental procedures to extract amphetamine and methamphetamine in serum were optimized with a relatively non-polar poly(dimethylsiloxane) coated fiber at pH 9.5, extraction time for 40 min and desorption at 260 degrees C for 2 min. Experimental results indicate that the concentration of the serum matrix diluted to a quarter of original (1:3) ratio by using one volume of buffer solution of boric acid mixed with sodium hydroxide and two volumes of water improves the extraction efficiency. Headspace derivatization following SPME was performed by using 6 microl 20% (v/v) heptafluorobutyric anhydride ethyl acetate solution at an oil bath temperature of 270 degrees C for 10 s. The precision was below 7% for analysis for without derivatization and below 17% for headspace derivatization. Detection limits were obtained at the ng/l level, one order better obtained in headspace derivatization than those achieved without derivatization. The feasibility of applying the methods to determine amphetamine and methamphetamine in real samples was examined by analyzing serum samples from methamphetamine abused suspects. Concentrations of the amphetamine and methamphetamine ranged from 6.0 microg/l (amphetamine) to 77 microg/l (methamphetamine) in serum.     

Determination of aliphatic amines using N-succinimidyl benzoate as a new derivatization reagent in gas chromatography combined with solid-phase microextraction

A simple, selective and sensitive approach was developed for the quantitation of aliphatic amines in lake water applying a new reagent (N-succinimidyl benzoate, SIBA), synthesized in the laboratory of the authors. Derivatization of the n-C1-C6 aliphatic monoamines and dimethylamine in aqueous solution with SIBA was followed by headspace solid-phase microextraction (SPME). Derivatives were identified by gas chromatography-mass spectrometry and determined by gas chromatography-flame ionization detection. Both derivatization and SPME conditions have been optimized. Derivatizations were performed in borate buffer (pH 8.8), at 60 degrees C for 22 min. SPME was carried out from saturated sodium chloride solution, at 80 degrees C for 60 min, desorption at 250 degrees C for 2 min. Detection limit of derivatized amines proved to be 0.13-7.2 nmol/l, while recovery of amines from lake water samples, in the concentration range of 100-200 microg/l, varied from 94.1 to 102.7%.     

Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.     

Direct screening of water samples for benzene hydrocarbon compounds by headspace liquid-phase microextraction-gas chromatography

The applicability of headspace liquid-phase microextraction and gas chromatography is evaluated for the expeditious and reliable screening of tap and drinking water samples for selected volatile organic compounds (viz., benzene, toluene, ethylbenzene, and xylene isomers, BTEX). The method uses 3.5 microL of n-hexadecane as extraction solvent, 10 min extraction time with stirring at 1250 rpm, at 20 degrees C and 0.38 g/mL salt addition. The enrichment factors of this method are from 135 to 213. Limits of detection are in the range of 4.1-23.5 ng/L. The relative standard deviations at 0.05, 50, 200, and 400 microg/L of spiking levels are in the range of 0.61%-4.01%. Recoveries of six BTEX from drinking water at these spiking levels are between 95.4% and 104.4%.     

固相微萃取-气质联用测定胶州湾海水中有机锡化合物

采用顶空固相微萃取-气质联用(HS-SPME-GC-MS)技术测定了胶州湾海水中有机锡的含量.样品用4%的四乙基硼化钠(NaBEt4)进行衍生,同时用PDMS纤维进行萃取,萃取富集后,用气质联用仪进行测定.通过分析,该方法中MBT的线性范围为10～1000ng/L,DBT和TBT的线性范围为50～1000ng/L,相对标准偏差低于14.0%,回收率在70.0%～125.0%之间,检出限低于12.5ng/L;通过所建立的方法对胶州湾海水中有机锡的污染现状进行了调查,发现胶州湾海水中存在不同程度的有机锡污染.     

A novel HS-SBSE system coupled with gas chromatography and mass spectrometry for the analysis of organochlorine pesticides in water samples

A methodology to analyze organochlorine pesticides (OCPs) in water samples has been accomplished by using headspace stir bar sorptive extraction (HS-SBSE). The bars were in house coated with a thick film of PDMS in order to properly work in the headspace mode. Sampling was done by a novel HS-SBSE system whereas the analysis was performed by capillary GC coupled mass spectrometric detection (HS-SBSE-GC-MS). The extraction optimization, using different experimental parameters has been established by a standard equilibrium time of 120 min at 85 degrees C. A mixture of ACN/toluene as back extraction solvent promoted a good performance to remove the OCPs sorbed in the bar. Reproducibility between 2.1 and 14.8% and linearity between 0.96 and 1.0 were obtained for pesticides spiked in a linear range between 5 and 17 ng/g in water samples during the bar evaluation.     

Analysis of polychlorinated biphenyls in aqueous samples by microwave-assisted headspace solid-phase microextraction

The hyphenated technique namely microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed and studied for the simultaneous extraction/enrichment of polychlorinated biphenyls (PCBs) in aqueous samples prior to the quantification by gas chromatography (GC). The PCBs in aqueous media are extracted onto a solid-phase micro fibre via the headspace with the aid of microwave irradiation. The optimum conditions for obtaining extraction efficiency, such as the extraction time, addition of salts, addition of methanol, ratio of sample to headspace volume, and the desorption parameters were investigated. Experimental results indicated that the proposed MA-HS-SPME method attained the best extraction efficiency under the optimized conditions, i.e., irradiation of extraction solution (20 ml aqueous sample in 40 ml headspace vial with no additions of salt and methanol) under 30 W microwave power for 15 cycles (1 min power on and 3 min power off of each cycle). Desorption at 270 degrees C for 3 min provided the best detection results. The detection limit obtained were between 0.27 and 1.34 ng/l. The correlation coefficient for the linear dynamic range from 1 to 80 ng/l exceeded 0.99 for 18 PCBs.     

Determination of butyltin stabilizers in PVC using Liquid-Phase microextraction with electrothermal atomic absorption spectrometry

A rapid and highly sensitive method is described for the extraction and determination of di- and tributyltin in PVC samples using headspace liquid phase microextraction followed by an analysis with graphite furnace atomic absorption spectrometry (HSLPME/ GFAAS). The analytes were derivatized in situ with sodium tetraethylborate and concentrated in a 2 ??l microdrop of benzyl alcohol suspended from the tip of a conventional GC microsyringe. The ethylated species then were directly transferred into a graphite furnace and quantified. The extractions were carried out for 5 ml sample solution (8 ml vial) adjusted at pH 5, with derivatization at 22 °C for 15 min in a 2% sodium tetraethylborate. The experimental parameters impacting the performance of HS-LPME were also investigated. According to the analysis, the linearity range was from 5.0 to 250.0 ng l^-1 with a detection limit of 0.5 ng l^-1 for dibutyltin and from 1.7 to 170.0 ng l^-1 with a detection limit of 0.17 ng l^-1 for tributyltin. Method RSD values were below 1.5%. Finally, the analysis of spiked PVC and water samples revealed that matrix had little effect upon extraction.     

Improved gas chromatography methods for micro-volume analysis of haloacetic acids in water and biological matrices

A fast headspace solid-phase microextraction gas chromatography method for micro-volume (0.1 mL) samples was optimized for the analysis of haloacetic acids (HAAs) in aqueous and biological samples. It includes liquid-liquid microextraction (LLME), derivatization of the acids to their methyl esters using sulfuric acid and methanol after evaporation, followed by headspace solid-phase microextraction with gas chromatography and electron capture detection (SPME-GC-ECD). The derivatization procedure was optimized to achieve maximum sensitivity using the following conditions: esterification for 20 min at 80 degrees C in 10 microL methanol, 10 microL sulfuric acid and 0.1 g anhydrous sodium sulfate. Multi-point standard addition method was used to determine the effect of the sample matrix by comparing with internal standard method. It was shown that the effect of the matrix for urine and blood samples in this method is insignificant. The method detection limits are in the range of 1 microg L(-1) for most of the HAAs, except for monobromoacetic acid (MBAA) (3 microg L(-1)) and for monochloroacetic acid (MCAA) (16 microg L(-1)). The optimized procedure was applied to the analysis of HAAs in water, urine and blood samples. All nine HAAs can be separated in < 13 min for biological samples and < 7 min for drinking water samples, with total sample preparation and analysis time < 50 min. Analytical uncertainty can increase dramatically as the sample volume decreases; however, similar precision was observed with our method using 0.1 mL samples as with a standard method using 40 mL samples.     

应用搅拌棒吸附萃取-热脱附-气相色谱/质谱法快速测定滇池水系中的16种多环芳烃

应用搅拌棒吸附萃取(SBSE)-热脱附(TDS)-气相色谱/质谱联用(GC/MS)方法测定了滇池水系(滇池和盘龙江上、中、下游)中16种多环芳烃(PAHs)的含量。方法快速简便,无有机溶剂污染,PAHs的最低检出限为1.0~468.8 pg,理论回收率在90%以上,加标回收率为83.1%~109.4%,相对标准偏差小于10%。测定结果表明,这16种多环芳烃在滇池水样中的含量为89.16 ng/L,在盘龙江上游水样中的含量为65.41 ng/L,在盘龙江中游水样中的含量为339.22 ng/L,而在盘龙江下游水样中的含量为62.25 ng/L,说明滇池水系已经受到一定的PAHs污染,加强对滇池、盘龙江中PAHs有机污染的控制势在必行。     

Coupling of ionic liquid-based headspace single-drop microextraction with GC for sensitive detection of phenols

A headspace single-drop microextraction (SDME) based on ionic liquid (IL) has been developed for the gas chromatographic determination of phenols. The volume of IL microdrop used was 1 microL. After extraction, the analytes were desorbed from the drop in the injection port and the involatile IL was withdrawn into the microsyringe. To facilitate the withdrawal of IL the upper diameter of the split inlet liner was enlarged to some extent. Some parameters were optimized for the determination of phenols. Under the selected conditions, i.e., desorption for 100 s at 210 degrees C after extraction for 25 min at 50 degrees C in solutions (pH 3) containing 0.36 g/mL sodium chloride, the LODs, RSDs, and the average enrichment factors of phenols were 0.1-0.4 ng/mL, 3.6-9.5% (n=5), and 35-794, respectively. The proposed procedure was applied to the determination of phenols in lake water and wastewater samples, and the spiked recoveries were in the range of 81-111% at a spiked level of 0.4 microg/mL. This method is a promising alternative for the sensitive determination of phenolic compounds.     

Organotin speciation in French brandies and wines by solid-phase microextraction and gas chromatography--pulsed flame photometric detection

An analytical method devoted to organotin compounds (OTC) determination in brandy and wine was developed. It is based on solid-phase microextraction (SPME) of ethylated organotins. The following operating factors were examined: SPME mode/nature of fibre coating, sample volume/dilution, and sampling time. The optimisation work led to dilute the sample in an aqueous buffer (1/11, v/v ratio) in order to satisfactorily decrease the matrix effects due to competitive sorption of non-OTC species onto/into fibre coating. The optimised operating conditions consist of polydimethylsiloxane (PDMS) coated fibre used in headspace mode for 30 min. In wines, the limits of detection (LOD) and quantification (LOQ) ranged from 1 to 40 and 3 to 80 ng(Sn)L(-1) respectively, according to the species. The analytical validation was made by evaluating the accuracy of OTC determination in spiked samples with various concentrations over the whole calibration range, i.e. from LOQ to 1000 ng(Sn)L(-1). Recovery was around 80-110% and precision (relative standard deviation, RSD) was between 12% and 25%. Despite the presence of two chromatographic peaks corresponding to sulphur compounds during brandy analysis, the selectivity of the method is adequate. The analysis confirmed the analytical performances and applicability of the method to wine and brandy samples. The obtained results emphasise the contamination of brandy and wine by organotins, the storage in plastic container seeming to be confirmed as the main OTC source.     

Determination of the acaricide fenbutatin oxide in water samples by automated headspace-SPME-GC/MS

The analysis of the acaricide fenbutatin oxide (FBTO) having a molecular weight of 1052.66 g mol(-1) in water samples by capillary GC/MS after in-situ derivatization with sodium tetraethylborate (NaBEt4) and headspace-SPME enrichment is described. Automated SPME is performed at 80 degrees C for 30 min. Detection is carried out in the ion monitoring mode with deuterated triphenyltin (TPhTd15) as internal standard. Good linearity (R2 = 0.9993) was obtained in the dynamic range 20 to 1000 ng L(-1) with a limit of detection of 16 ng L(1) (LOD at 3 S/N) and a limit of quantitation of 50 ng L(-1) (LOQ at 10 S/N). Intra-day RSD% for n=6 was 8.9 at the LOQ level.     

Determination of pyrethroid,organophosphate and organochlorine pesticides in water by headspace solid-phase microextraction

Simultaneous determination of pyrethroid, organophosphate (OP) and organochlorine (OC) pesticides in water was achieved with headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron-capture detection (GC-ECD). The parameters affecting HS-SPME of pesticides from water were optimized, including extraction temperature, sample and headspace volumes, and sodium chloride amounts. The effects of desorption temperature, desorption time, and position of the fibre in the GC inlet were also investigated. Extraction temperature was the most important factor affecting the recoveries of analytes, and the optimized temperature was 96°C. The addition of salt did not increase extraction efficiencies of the pesticides from the water. The optimized desorption conditions in the GC were as follows: desorption time of 10?min; desorption temperature of 260°C; and a 2?cm position of the fibre in the inlet. The method detection limits were in the low-ng/L level with a linearity range of 50–1000?ng/L for the OCs, 50–5000?ng/L for the OP, and 50–20?000?ng/L for the pyrethroids. These data demonstrated that HS-SPME is a sensitive method for the determination of pyrethroid, OC, and OP pesticides in water.     

Rapid determination of C6-aldehydes in tomato plant emission by gas chromatography-mass spectrometry and solid-phase microextraction with on-fiber derivatization

A simple, rapid, sensitive, and solvent-free method was developed for determination of plant-signalling compounds, the three C6-aldehydes hexanal, (Z)-3-hexenal, and (E)-2-hexenal, in tomato plant emission by gas chromatography-mass spectrometry (GC-MS) and solid-phase microextraction (SPME) with on-fiber derivatization. In this method, O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine (PFBHA) in aqueous solution was first headspace adsorbed onto a 65 microm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber at 25 degrees C for 5 min, and then the fiber with adsorbed PFBHA was used for headspace extraction of tomato plant emission at 25 degrees C for 6 min. Finally, the resulting oximes adsorbed on the fiber were desorbed and analyzed by GC-MS. Extraction conditions and method validation were studied. The proposed method had low detection limit values for the three aldehydes from 0.1 to 0.5 ng/L and good precision (RSD less than 10%). In this work, the method was applied to investigation of tomato plant defense response to Helicoverpa armigera.     

Fully automated determination of N-nitrosamines in environmental waters by headspace solid-phase microextraction followed by GC-MS-MS

A fully automated method for determining nine Environmental Protection Agency N-nitrosamines in several types of environmental waters at ng/L levels is presented. The method is based on a headspace solid-phase microextraction followed by GC-MS-MS using chemical ionization. Three different fibers (carboxen/PDMS, divinylbenzene/carboxen/PDMS, and PEG) were tested. Solid-phase microextraction conditions were best when a divinylbenzene/carboxen/PDMS fiber was exposed for 60?min in the headspace of 10?mL water samples at pH 7 containing 360?g/L of NaCl, at 45°C. All compounds were analyzed by GC-MS-MS within 18?min. The method was validated using effluent from an urban wastewater treatment plant and the LODs ranged from 1 to 5?ng/L. The method was then applied to determine the N-nitrosamines in samples of different complexities, such as tap water and several influent and effluent wastewater samples from urban and industrial wastewater treatment plants and a potable water treatment plant. Although the analysis of influent industrial wastewater revealed high concentrations of some compounds (N-nitrosomorpholine and N-nitrosodimethylamine at μg/L levels), in industrial effluents and other samples, the concentrations were substantially lower (ng/L levels). The new method is suitable for the simple and reliable determination of N-nitrosamines in highly complex water samples in a completely automated procedure.     

Sensitive method for determination of methyl tert-butyl ether (MTBE) in water by use of headspace-SPME/GC-MS

A simple and rapid method for the determination of methyl tert-butyl ether (MTBE) in water by headspace-solid-phase microextraction (headspace-SPME) at sub-microg/L concentrations is described. On using a cooled SPME fiber coated with a 75-microm layer of poly(dimethylsiloxane)/carboxene and heating the sample to 35 degrees C, about 4 times more MTBE is extracted compared to SPME extraction with the fiber placed in the water sample. Stable analytical conditions with a detection limit of 10 ng/L are achieved. By use of a sample volume of 4 mL in a 10 mL vial, a sodium chloride content of 10% (w/w), and an extraction time of 30 min, the total time of an analytical cycle was optimized to 39 min. Precise linearity of R2>0.9991 and R2>0.9916 in the calibration range of 20-5000 ng/L and 20-100 ng/L, both in addition to blanks, respectively, and relative standard deviations of 10% (100 ng/L, long-term) and 11% (20 ng/L, short-term) are presented. The recovery is well within the accepted limits of 83-118% at a concentration of 100 ng/L and even close thereto at trace levels of 20 ng/L (96-125%). The data presented for a concentration of 100 ng/L are examined by statistical methods and show results for the T test at the 95% confidence level. Due to the large concentration range covered, the method is well suited for the monitoring of MTBE in the aquatic environment.     

顶空气相法测定氯乙烯生产过程产生的盐酸溶液中的乙炔和氯乙烯

 采用顶空气相法测定了氯乙烯生产过程产生的盐酸溶液中的乙炔和氯乙烯。使用氢氧化钠将试样中的氯化氢中和 ,从而消除其在气相分析乙炔和氯乙烯中的影响。顶空平衡温度为 35℃ ,平衡时间为 4 5min ,柱为填充了GDX 2 0 2固定相的 2m× 3mmi d 不锈钢柱 ,柱温 14 0℃。顶空气体进样量为 1mL。以外标法定量 ,乙炔含量测定结果的相对标准偏差为 0 85 % ;当其含量为 30 0 μg/g～ 15 0 μg/g时 ,回收率为 98 9%～10 3%。氯乙烯含量测定结果的相对标准偏差为 1 4 % ;当其含量为 2 0 0 μg/g～ 10 0 μg/g时 ,回收率为 98 8%～10 2 %。     

Determination of Se4+ in drinkable water by solid-phase microextraction and gas chromatography/mass spectrometry

A method was developed for the selective determination of Se4+ in drinkable water by solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS). Se4+ was selectively derivatized to ethane, 1,1'-selenobis by reaction with sodium tetraethylborate, extracted by the SPME fiber, and determined by GC/MS. Both headspace (HS)-SPME and direct SPME were studied. The method requires only a few milliliters of sample and 20 min for completion. At 2.0 microg/L concentration, the relative standard deviation was 10.1% for HS-SPME and 9.1% for direct SPME. For HS-SPME, the theoretical detection limit was 81 ng/L and 166 ng/L for direct SPME. The recovery rate was 95%. The method was used to determine Se4+ in 10 tap water samples.