Development of gas chromatography-mass spectrometry following microwave distillation and simultaneous headspace single-drop microextraction for fast determination of volatile fraction in Chinese herb

In this work, for the first time, microwave distillation (MD) coupled with simultaneous headspace single-drop microextraction (HS-SDME) was developed for the determination of the volatile components in the Chinese herb, Artemisia capillaris Thunb. The volatile components were rapidly isolated by MD, and simultaneously extracted and concentrated by using a dodecane microdrop. The volatile oil extracted in the microdrop solvent was analyzed by gas chromatography-mass spectrometry (GC-MS). The experimental parameters of solvent selection, microdrop volume, microwave power, irradiation time and sample amount were investigated, and the method precision was also studied. The optimal parameters were extraction solvent of dodecane, solvent volume of 2.0 microL, microwave power of 400 W, irradiation time of 4 min, and sample amount of 2.0 g. Thirty-five volatile compounds present in Artemisia capillaris Thunb. were identified by using the proposed method, which were identical with those obtained by the conventional steam distillation method. The experimental results showed that MD-HS-SDME is a simple, rapid, reliable, and solvent-free technique for the determination of volatile compounds in Chinese herbs.     

Application of single-drop microextraction combined with in-microvial derivatization for determination of acidic herbicides in water samples by gas chromatography-mass spectrometry

A single-drop microextraction (SDME) method and gas chromatography with mass spectrometry detection have been developed for the determination of acidic herbicides in water. The analytes were extracted from a 3 mL sample solution using 4 microL of hexyl acetate. After extraction, derivatization was carried out inside a glass microvial (1.1mm i.d.) using pentafluorobenzyl bromide (PFBBr). Triethylamine (TEA) was used as the reaction catalyst. The influence of derivatization reagent volume, catalyst amount, derivatization time and temperature on the yield of the in-microvial derivatization was investigated. Derivatization reaction was performed using 0.3 microL of PFBBr and 0.4 microL of TEA (10%, v/v in toluene) at 100 degrees C during 5 min. Also, the effects of different experimental SDME parameters such as selection of organic solvent, sample pH, addition of salt, extraction time and temperature of extraction were studied. Analytical parameters such as enrichment factor, precision, linearity and detection limits were also determined. The enrichment factors were between 83 and 157. The limits of detection (LOD) were in the range 1.2-7 ng/L (S/N=3). The relative standard deviations obtained were below 10.1% (n=5).     

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%。     

Pressurised hot water extraction followed by simultaneous derivatization and headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry for the determination of aliphatic primary amines in sewage sludge

In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS-MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS-MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) (n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg⁻¹ s (range found 9-135) and the average limit of quantification (LOQ) was of 230 μg kg⁻¹ (range found 50-450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg⁻¹ (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE.     

Determination of phenols in water samples by single-drop microextraction followed by in-syringe derivatization and gas chromatography-mass spectrometric detection

Trace analysis of phenolic compounds in water was performed by coupling single-drop microextraction (SDME) with in-syringe derivatization of the analytes and GC-MS analysis. The analytes were extracted from a 3ml sample solution using 2.5microl of hexyl acetate. After extraction, derivatization was carried out in syringe barrel using 0.5microl of N,O-bis(trimethylsilyl)acetamide. The influence of derivatizing reagent volume, derivatization time and temperature on the yield of the in-syringe silylation was investigated. Derivatization reaction is completed in 5min at 50 degrees C. Experimental SDME parameters, such as selection of organic solvent, sample pH, addition of salt, extraction time and temperature of extraction were studied. Analytical parameters, such as enrichment factor, precision, linearity and detection limits were also determined. The limits of detection were in the range of 4-61ng/l (S/N=3). The relative standard deviations obtained were between 4.8 and 12% (n=5).     

Fast determination of Z-ligustilide in plasma by gas chromatography/mass spectrometry following headspace single-drop microextraction

Angelica sinensis (danggui in Chinese) is a common traditional Chinese medicine (TCM), and its essential oil has been used for the treatment of many diseases such as hepatic fibrosis. Z-Ligustilide has been found to be an important active component in the TCM essential oil. In this work, for the first time, headspace single-drop microextraction (HS-SDME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of Z-ligustilide in rabbit plasma after oral administration of essential oil of danggui. The extraction parameters of solvent selection, solvent volume, sample temperature, extraction time, stirring rate, and ion strength were systemically optimized. Furthermore, the method linearity, detection limit, and precision were also investigated. It was shown that the proposed method provided good linearity (0.02-20 microg/mL, R2 = 0.997), low detection limit (10 ng/mL), and good precision (RSD value less than 9%). Finally, HS-SDME followed by GC/MS was used for fast determination of Z-ligustilide in rabbit plasma at different time intervals after oral administration of danggui essential oil. The experimental results suggest that HS-SDME followed by GC/MS is a simple, sensitive, and low-cost method for the determination of Z-ligustilide in plasma, and a low-cost approach to pharmacokinetics studies of active components in TCMs.     

Purge-assisted headspace solid-phase microextraction combined with gas chromatography-mass spectrometry for determination of chlorophenols in aqueous samples

A simple, economical and very effective method is demonstrated for simultaneous determination of 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, in aqueous samples, by using purge-assisted headspace solid-phase microextraction (PA/HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In the new method, purging the sample enhances the removal of the trace chlorophenols without derivatization from the matrices to the headspace. Extraction parameters including extraction temperature, purge gas flow rate and extraction time were systematically investigated. Under optimal conditions, the relative standard deviations (RSDs) were 4-11% at 50 pg/mL and 5-14% at 5 pg/mL, respectively. The recoveries were in the range of 83-114%. Detection limits were determined at the fg level. These results indicate that PA/HS-SPME provides a significant contribution to highly efficient extraction of semi-volatile CPs, especially for pentachlorophenol, which has the smallest Henry's constant and large octanol-water partitioning coefficient. In addition, the proposed method was successfully applied to the analysis of chlorophenols in landfill leachate. New perspectives are opened for headspace extraction of relatively low vapor pressure compounds in complex matrices.     

Simultaneous determination of aliphatic and aromatic amines in water and sediment samples by ion-pair extraction and gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry (GC-MS) method has been proposed for the determination of aliphatic and aromatic amines in a variety of environmental samples including wastewater, river water, sea water and sediment samples. The method includes ion-pair extraction with bis-2-ethylhexylphosphate (BEHPA), derivatisation of compounds with isobutyl chloroformate (IBCF) and their GC-MS analysis. Aliphatic and aromatic amines were isolated from aqueous samples using BEHPA as ion-pair reagent and derivatised with IBCF for their chromatographic analysis. Solid-liquid extraction of aliphatic and aromatic amines in sediment samples were performed in Soxhlet apparatus with acidic MeOH and ion-pair extraction with BEHPA were carried out for the isolation of amines followed by derivatisation with IBCF. Aliphatic and aromatic amines were then analysed with GC-MS in both electron impact (EI) and positive and negative ion chemical ionisation (PNICI) mode as their isobutyloxycarbonyl (isoBOC) derivatives. The obtained recoveries ranged from 81.0 to 98.0% and the precision of this method, as indicated by the relative standard deviations (RSDs) was within the range of 0.5 and 4.3%. The detection limits obtained from calculations by using GC-MS results based on S/N = 3 were within the range from 0.07 to 0.50 ng/l.     

Development of gas chromatography/mass spectrometry following headspace solid-phase microextraction for fast determination of asarones in plasma

Asarones (alpha-asarone and beta-asarone) are the active components in the traditional Chinese medicine (TCM) of Acorus tatarinowii Schott, which has been used to treat epilepsy for several thousand years. To perform the pharmacokinetics (PK) study of alpha- and beta-asarone from the TCM essential oil, a simple, rapid and sensitive method was developed for the determination of asarones from the TCM in rabbit plasma, based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/mass spectrometry (GC/MS) with electron ionization (EI). The extraction parameters of headspace volume, fiber coating, sample temperature, extraction time, stirring rate and ion strength were systemically optimized. Furthermore, the method linearity, detection limit and precision were also investigated. It was shown that the proposed method provided a good linearity (0.02-20 microg/mL, R(2) > 0.99), low detection limit (<2.0 ng/mL) and good precision (RSD < 7.0%). Finally, HS-SPME followed by GC/MS was applied to fast determination of alpha- and beta-asarone in rabbit plasma at different time points after oral adminstration of the essential oil from A. tatarinowii. The experimental results suggest that the proposed method provides an alternative approach to the PK studies of volatile compounds in TCMs.     

Application of headspace solid-phase microextraction followed by gas chromatography-mass spectrometry to determine short-chain alkane monocarboxylic acids in aqueous samples

In this study, a procedure was developed to determine short-chain alkane monocarboxylic acids (SCMAs) in aqueous samples using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography (GC) coupled with mass spectrometry (MS). A Stabilwax-DA capillary column (30 m × 0.32-mm inner diameter, 0.50-μm film thickness) was used for GC separation and a 60-μm poly(ethylene glycol) fiber was used to isolate SCMAs from water and introduce them into the gas chromatograph. Parameters of HS-SPME, analyte desorption, and GC-MS analysis were selected and an analytical procedure was proposed. Limits of quantitation were on the order of about 0.2 mg L^-1. As an example of the application of the procedure, SCAMs were determined in municipal wastewater at different steps of treatment.     

Automated headspace solid-phase microextraction and in-matrix derivatization for the determination of amphetamine-related drugs in human urine by gas chromatography-mass spectrometry

An automated extraction and determination method for the gas chromatography (GC)-mass spectrometry (MS) analysis of amphetamine-related drugs in human urine is developed using headspace solid-phase microextraction (SPME) and in-matrix derivatization. A urine sample (0.5 mL, potassium carbonate (5 M, 1.0 mL), sodium chloride (0.5 g), and ethylchloroformate (20 microL) are put in a sample vial. Amphetamine-related drugs are converted to ethylformate derivatives (carbamates) in the vial because amphetamine-related drugs in urine are quickly reacted with ethylchloroformate. An SPME fiber is then exposed at 80 degrees C for 15 min in the headspace of the vial. The extracted derivatives to the fiber are desorbed by exposing the fiber in the injection port of a GC-MS. The calibration curves show linearity in the range of 1.0 to 1000 ng/mL for methamphetamine, fenfluramine, and methylenedioxymethamphetamine; 2.0 to 1000 ng/mL for amphetamine and phentermine; 5.0 to 1000 ng/mL for methylenedioxyamphetamine; 10 to 1000 ng/mL for phenethylamine; and 50 to 1000 ng/mL for 4-bromo-2,5-dimethoxyphenethylamine in urine. No interferences are found, and the time for analysis is 30 min for one sample. Furthermore, this proposed method is applied to some clinical and medico-legal cases by taking methamphetamine. Methamphetamine and its metabolite amphetamine are detected in the urine samples collected from the patients involved in the clinical cases. Methamphetamine, amphetamine, and phenethylamine are detected in the urine sample collected from the victim of a medico-legal case.     

Optimization of simultaneous derivatization and extraction of aliphatic amines in water samples with dispersive liquid-liquid microextraction followed by HPLC

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) with simultaneous derivatization followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of primary and secondary aliphatic amines in environmental water samples. A ternary mixture consisting of a disperser, an extractant and a derivatization reagent was used for the simultaneous derivatization and extraction of aliphatic amines in different water samples. The effects of various experimental parameters on derivatization and extraction efficiency were studied simultaneously using experimental design. A Plackett-Burman design was performed for screening of variables in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by using a Box-Behnken design (BBD) and the response surface equations were derived. Under optimal conditions, the preconcentration factors were between 210 and 290. The limit of detections (LODs) ranged from 0.005 to 0.02 μg/L and dynamic linear ranges (DLRs) of 0.05-500 and 0.1-500 μg/L were obtained for most of analytes. The performance of the method was evaluated for extraction and determination of primary and secondary aliphatic amines in environmental water samples in micrograms per liter and satisfactory results were obtained (RSDs <12.5%).     

Microwave-assisted headspace solid-phase microextraction for the rapid determination of organophosphate esters in aqueous samples by gas chromatography-mass spectrometry

The rapid and solvent-free determination of organophosphate esters (OPEs) in aqueous samples via one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analysis is described. Tri-n-butyl phosphate (TnBP) and tris-(2-ethylhexyl) phosphate (TEHP) were selected as model compounds for the method of development and validation. The effects of various extraction parameters for the quantitative extraction of these analytes by MA-HS-SPME were systematically investigated and optimized. The analytes, in a 20 mL water sample (in a 40 mL sample bottle containing 2 g of NaCl, pH 3.0), were efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the system was microwave irradiated at 140 W for 5 min. The limits of quantification (LOQs) for TnBP and TEHP were 0.5 and 4 ng/L, respectively. Using the standard addition method, MA-HS-SPME coupled with GC-MS was utilized to determine selected OPEs in surface water and wastewater treatment plants (WWTP) influent/effluent samples. Preliminary results show that TnBP was commonly detected OPEs in these aqueous samples, the correlation coefficients (r²) of the standard addition curves were greater than 0.9822, indicating that the developed method appears to be a good alternative technique for analyzing OPEs in aqueous samples.     

Determination of aliphatic amines in water by gas chromatography using headspace solvent microextraction

The possibility of applying headspace microextraction into a single drop for the determination of amines in aqueous solutions is demonstrated. A 1 μl drop of benzyl alcohol containing 2-butanone as an internal standard was suspended from the tip of a micro syringe needle over the headspace of stirred sample solutions for extraction. The drop was then injected directly into a GC. The total chromatographic determination was less than 10 min. Optimization of experimental conditions (sampling time, sampling temperature, stirring rate, ionic strength of the solution, concentration of reagents, time of extraction and organic drop volume) with respect to the extraction efficiency were investigated and the linear range and the precision were also examined. Calibration curves yielded good linearity and concentrations down to 2.5 ng ml⁻¹ were detectable with R.S.D. values ranging from 6.0 to 12.0%. Finally, the method was successfully applied to the extraction and determination of amines in tap and river water samples. This system represents an inexpensive, fast, simple and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.     

Evaluation of liquid-phase microextraction conditions for determination of chlorophenols in environmental samples using gas chromatography-mass spectrometry without derivatization

Determination of trace chlorophenols (CPs) in environmental samples has been evaluated using liquid-phase microextraction (LPME) coupled with gas chromatography-mass spectrometry (GC-MS) without derivatization. The LPME procedure used to extract CPs from water involved 15 microL 1-octanol as acceptor solution in a 5.0 cm polypropylene hollow fiber with an inner diameter of 600 microm and a pore size of 0.2 microm. Under the optimal extraction conditions, enrichment factors from 117 to 220 are obtained. The obtained linear range is 1-100 ng mL(-1) with r(2)=0.9967 for 2,4-dichlorophenol (2,4-DCP); 1-100 ng mL(-1) with r(2)=0.9905 for 2,4,6-trichlorophenol (2,4,6-TCP); 5-500 ng mL(-1) with r(2)=0.9983 for 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and 10-1000 ng mL(-1) with r(2)=0.9929 for pentachlorophenol (PCP). The limits of detection range from 0.08 to 2 ng mL(-1), which is comparable with the reported values (12-120 ng mL(-1)). Recoveries of CPs in various matrices exceed 85% with relative standard deviations of less than 10%, except for PCP in landfill leachate. The applicability of this method was examined to determine CPs in environmental samples by analyzing landfill leachate, ground water and soil. The 2,4-DCP and 2,4,6-TCP detected in the landfill leachate are 6.68 and 2.47 ng mL(-1). The 2,4,6-TCP detected in ground water is 2.08 ng mL(-1). All the studied CPs are detected in contaminated soil. The proposed method is simple, low-cost, less organic solvent used and can potentially be applied to analyze CPs in complex environmental matrices.     

Simultaneous determination of aliphatic and aromatic amines in indoor and outdoor air samples by gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry (GC-MS) method has been proposed for the simultaneous determination of aliphatic and aromatic amines in indoor and outdoor air samples. The method includes pre-concentration of the compounds by percolating the air samples through the acidic solution, ion-pair extraction with bis-2-ethylhexylphosphate (BEHPA), derivatisation of compounds with isobutyl chloroformate (IBCF) and their GC-MS analysis. Aliphatic and aromatic amines were isolated from aqueous samples using BEHPA as ion-pair reagent and derivatised with IBCF for their chromatographic analysis. Aliphatic and aromatic amines were then analysed with GC-MS in both electron impact (EI) and positive and negative ion chemical ionisation (PNICI) mode as their isobutyloxycarbonyl (isoBOC) derivatives. The obtained recoveries ranged from 75.6 to 96.8% and the precision of this method, as indicated by the relative standard deviations (R.S.D.) was within the range of 1.0-4.4%. The detection limits obtained from calculations by using GC-MS results based on S/N: 3 were within the range of 0.08-0.01 ng/m³.     

Microwave-assisted derivatization and single-drop microextraction for gas chromatographic determination of chromium(III) in water

A rapid and efficient sample preparation method combining microwave-assisted derivatization (MAD) and single-drop microextraction (SDME) for the gas chromatographic (GC) determination of trace Cr(III) in water was developed. Aqueous Cr(III) was first converted to the volatile chromium trifluoroacetylacetonate (Cr(tfa)3) by reaction with 1,1,1-trifluoroacetylacetone (Htfa) under the irradiation of microwave. Derivatization of Cr(III) at ng ml(-1) level could be completed in less than 1 min. The formed Cr(tfa)3 was then extracted into a small droplet (2 microl) of toluene suspended at the tip of a microsyringe needle. The optimal extraction time was 30 min. The solvent drop was directly injected into a GC equipped with a flame photometric detector (FPD) for analysis. The two Cr(tfa)3 isomers extracted could be efficiently separated in 2 min. Linearity (r>0.99) over the concentration range 2-300 ng ml(-1) Cr was obtained and the limit of detection was 0.5 ng ml(-1) Cr. The relative standard deviation was 7.8% at 20 ng ml(-1) Cr (n=5). Applicability of this method to water analysis was examined by analyzing the chromium content in a reference standard water sample and an industrial effluent.     

Full automatic determination of chlorophenols in water using solid-phase microextraction/on-fiber derivatization and gas chromatography-mass spectrometry

A fully automated combination of solid-phase microextraction and on-fiber derivatization coupled with gas chromatography-mass spectrometry was developed to determine 17 chlorophenols in aqueous samples. Optimal parameters for the automated process, such as fiber coating (polyacrylate), derivatization reagent (N,O-bis(trimethylsilyl) trifluoroacetamide), extraction time (60 min), derivatization time (5 min), incubation temperature (35°C), sample pH (3), and ionic strength (300 g L(-1) of NaCl), as well as desorption time (5 min) and desorption temperature (270°C) were established. The whole procedure took only 90 min and was performed automatically. The shortcomings of silylation derivatives, like incompleteness and instability, were overcome by using solid-phase microextraction on-fiber silylation in this study. The results from both pure water and river water samples showed that the method had a good linearity (r(2) = 0.9993-1.0000), ranging from 0.01 to 100 μg L(-1). The related standard deviations were between 3.6 and 10.0%. The limits of detections and qualifications ranged from 0.03 to 3.11 ng L(-1) and 0.09 to 10.4 ng L(-1) for the CPs, respectively. The proposed method is superior to traditional solid phase extraction procedure.     

Simple and automatic determination of aldehydes and acetone in water by headspace solid-phase microextraction and gas chromatography-mass spectrometry

We describe a simple and automatic method to determine nine aldehydes and acetone simultaneously in water. This method is based on derivatization with 2,2,2-trifluoroethylhydrazine (TFEH) and consecutive headspace-solid-phase microextraction and gas chromatography-mass spectrometry. Acetone-d(6) was used as the internal standard. Aldehydes and acetone in water reacted for 30 min at 40°C with TFEH in a headspace vial and the formed TFEH derivatives were simultaneously vaporized and adsorbed on polydimethylsiloxane-divinylbenzene. Under the established condition, the method detection limit was 0.1-0.5 μg/L in 4 mL water and the relative standard deviation was less than 13% at concentrations of 0.25 and 0.05 mg/L. This method was applied to determine aldehydes and acetone in 5 mineral water and 114 surface water samples. All mineral water samples had detectable levels of methanal (24.0-61.8 μg/L), ethanal (57.7-110.9 μg/L), propanal (11.5-11.7 μg/L), butanal, pentanal (3.3-3.4 μg/L) and nonanal (0.3-0.4 μg/L). Methanal and ethanal were also detected in concentration range of 2.7-117.2 and 1.2-11.9 μg/L, respectively, in surface water of 114 monitoring sites in Korea.