Ultrasonic nebulization extraction coupled with on-line gas chromatography for determination of trans-anethole in spices

Ultrasonic nebulization extraction (UNE) coupled with on-line gas chromatography (GC) was proposed for the determination of trans-anethole in fruits of Illicium verum Hook. f. and Foeniculum vulgare Mill. The extraction was performed in a common self-made extraction system. In the UNE the analyte was transferred and enriched from the solid sample to gas phase. The sample gas containing analyte obtained by UNE was introduced into the sampling loop with the purging gas (N₂). And then the sample gas in the sampling loop was introduced into the GC column. Several experimental parameters of on-line UNE-GC, including sampling time, flow rate of purging gas, standstill time and temperature of tubing, were optimized. The calibration curve ranging from 0.05 to 1.5 mg g⁻¹ for determining the trans-anethole was obtained. The recoveries for determining trans-anethole are between 99.2% and 111.2% and RSDs are less than 8.3% when the UNE was applied. The analytes can rapidly be extracted and transferred from the solid sample to gas phase. The analytes in the gas phase are easier to be introduced into GC system than those in the solid and liquid phase. Compared with off-line systems, the proposed on-line system is more suitable to detect volatile compounds.     

Extraction of the Volatile and Semivolatile Compounds in Seeds of Cuminum cyminum L. Using Hydrodistillation Followed by Headspace-Ionic Liquid-Based Single-Drop Microextraction

Hydrodistillation (HD) coupled with headspace single-drop microextraction by using ionic liquid (IL) as the extraction solvent, followed by gas chromatography analysis technique, was successfully developed to determine the volatile and semivolatile compounds in seeds of Cuminum cyminum L. In the proposed method, a 1.5-??L microdrop of 1-octyl-3-methylimidazolium hexafluorophosphate, working as the extraction solvent was suspended in the headspace of a 50-mL round-bottom sample flask. After extracting for 30?min, both IL and target analytes were injected into the gas chromatographic system by thermal desorption for 5?s under 240?°C. Then, the IL was retracted back to the microsyringe. Thus, the capillary column should not be contaminated and a clean chromatogram was obtained. The parameters affecting extraction performance were investigated and optimized. The extraction efficiency of the proposed method was compared with that of HD, which is a standard extraction method. The contents of constituents in the extract obtained by the proposed method were close to those obtained by HD. It seems to be an environmentally friendly, time-saving, high efficiency and low solvent consumption technique and would be useful, especially for aromatic plants analysis.     

Extraction of the Volatile and Semivolatile Compounds in Seeds of Cuminum cyminum L. Using Hydrodistillation Followed by Headspace-Ionic Liquid-Based Single-Drop Microextraction

Hydrodistillation (HD) coupled with headspace single-drop microextraction by using ionic liquid (IL) as the extraction solvent, followed by gas chromatography analysis technique, was successfully developed to determine the volatile and semivolatile compounds in seeds of Cuminum cyminum L. In the proposed method, a 1.5-μL microdrop of 1-octyl-3-methylimidazolium hexafluorophosphate, working as the extraction solvent was suspended in the headspace of a 50-mL round-bottom sample flask. After extracting for 30 min, both IL and target analytes were injected into the gas chromatographic system by thermal desorption for 5 s under 240 °C. Then, the IL was retracted back to the microsyringe. Thus, the capillary column should not be contaminated and a clean chromatogram was obtained. The parameters affecting extraction performance were investigated and optimized. The extraction efficiency of the proposed method was compared with that of HD, which is a standard extraction method. The contents of constituents in the extract obtained by the proposed method were close to those obtained by HD. It seems to be an environmentally friendly, time-saving, high efficiency and low solvent consumption technique and would be useful, especially for aromatic plants analysis.

     

Ultrasonic nebulization extraction coupled with headspace single drop microextraction and gas chromatography-mass spectrometry for analysis of the essential oil in Cuminum cyminum L.

A novel method for analysis of essential oil in Cuminum cyminum L. using simultaneous ultrasonic nebulization extraction and headspace single drop microextraction (UNE-HS-SDME) followed by gas chromatography-mass spectrometry was developed. Experimental parameters, including the kind of suspended solvent, microdrop volume, sample amount, extraction time, enrichment time and salt concentration were examined and optimized. Compared with hydrodistillation (HD), UNE-HS-SDME provides the advantages of a small amount of sample (50 mg), time-saving (20 min), simplicity, cheapness and low toxicity. In addition, UNE-HS-SDME also provided higher enrichment efficiency and sensitivity compared with stirring extraction (SE)-HS-SDME, ultrasonic assistant extraction (UAE) and UNE. Some constituents in the essential oil, were identified and the detection limits for β-pinene, p-cymene and γ-terpinene range from 6.67 pL L⁻¹ to 14.8 pL L⁻¹. The results indicated that the UNE-HS-SDME is simple and highly efficient extraction and enrichment technique.     

Ultrasonic nebulization extraction-heating gas flow transfer-headspace single drop microextraction of essential oil from pericarp of Zanthoxylum bungeanum Maxim

The ultrasonic nebulization extraction-heating gas flow transfer coupled with headspace single drop microextraction (UNE-HGFT-HS-SDME) was developed for the extraction of essential oil from Zanthoxylum bungeanum Maxim. The gas chromatography-mass spectrometry was applied to the determination of the constituents in the essential oil. The contents of the constituents from essential oil obtained by the proposed method were found to be more similar to those obtained by hydro-distillation (HD) than those obtained by ultrasonic nebulization extraction coupled with headspace single drop microextraction (UNE-HS-SDME). The heating gas flow was firstly used in the analysis of the essential oil to transfer the analytes from the headspace to the solvent microdrop. The relative standard deviations for determining the five major constituents were in the range from 1.5 to 6.7%. The proposed method is a fast, sensitive, low cost and small sample consumption method for the determination of the volatile and semivolatile constituents in the plant materials.     

Residual Solvents Determination in Pharmaceuticals by Static Headspace-Gas Chromatography and Headspace Liquid-Phase Microextraction Gas Chromatography

A headspace liquid phase microextraction (HS-LPME) method has been developed and optimized for the residual solvent determination in pharmaceutical products. A microdrop of n-hexanol containing isopropanol (as internal standard) was suspended at the tip of a gas chromatographic syringe and exposed to the headspace of the sample solution. After extraction for an optimized time, the microdrop was retracted into the syringe and injected directly into a GC injection port. Critical experimental factors, including extraction solvent, temperature, ionic strength, stirring rate, extraction time, equilibrium time, drop volume, and sample volume were investigated and optimized. Compared with the static headspace technique, HS-LPME method showed superior results, being compatible with the pharmaceutical samples.     

Determination of phenols in water using liquid phase microextraction with back extraction combined with high-performance liquid chromatography.

Liquid phase microextraction with back extraction (LPME/BE) combined with high-performance liquid chromatography (HPLC) was studied for the determination of a variety of phenols in water samples. The target compounds were extracted from 2-ml aqueous sample adjusted to pH 1 (donor solution) through a microliter-size organic solvent phase (400-microl n-hexane), confined inside a small PTFE ring, and finally into a 1-microl basic aqueous acceptor microdrop suspended inthe aforementioned solvent phase from the tip of a microsyringe needle. After extracting for a prescribed time, the microdrop was taken back into the syringe and directly injected into an HPLC for detection. Factors relevant to the extraction procedure were studied. At the optimized extraction conditions, a large enrichment factor (more than 100-fold) can be achieved for most of the phenols within 35 min. The detection limit range was 0.5-2.5 microg/l for different analytes in aqueous samples. The results demonstrate the suitability of the LPME/BE approach to the analysis of polar compounds in aqueous samples.     

Liquid-liquid Microextraction Based on Solidification of Floating Organic Drops Coupled with Gas Chromatography for Analyzing Trace Benzene,Toluene and Xylene in Water Samples

A new liquid-liquid microextraction method based on the solidification of floating organic drops coupled with gas chromatography was developed for the determination of trace benzene, toluene and xylene(BTX) in water samples. In the microextraction procedure, a microdrop of n-decanol was delivered to the surface of the analytes’ solution, and stirred for a desired time. Following the absolute extraction, the sample vial was cooled in an ice bath for 10 min. The solidified n-decanol was then transferred into a plastic tube and melted naturally; and 1 μL of it was injected into gas chromatography for analysis. Factors relevant to the extraction efficiency were studied and optimized. The optimal experimental conditions were: 15 μL of n-decanol as extractive solvent, 30 mL of solution containing analytes, no salt, the stirring rate 400 r/min, the extraction temperature 30 °C, and the extraction time 30 min. Under those optimized conditions, the detection limit(LOD) of analytes was in a range of 0.05―0.10 ng/mL by the developed method. A good linearity(r>0.99) in a calibration range of 0.01―100 μg/mL was obtained. The recoveries of the real samples at different spiked levels of BTX were in the range from 92.2% to 103.4%.     

Headspace Single Drop Microextraction for the Analysis of Fire Accelerants in Fire Debris Samples

Fire accelerants such as gasoline, kerosene, and diesel have commonly been used in arson cases. Improved analytical methods involving the extraction of fire accelerants are necessary to increase sample yield and to reduce the number of uncertain findings. In this study, an analytical method based on headspace single drop microextraction (HS-SDME) followed by gas chromatography–flame ionization detection (GC-FID) has been developed for the analysis of simulated fire debris samples. Curtain fabric was used as the sample matrix. The optimized conditions were 2.5 μL benzyl alcohol microdrop exposed for 20 min to the headspace of a 10 mL aqueous sample containing accelerants placed in 15-mL sample vial and stirred at 1500 rpm. The extraction method was compared with the solvent extraction method using n-hexane for the determination of fire accelerants. The HS-SDME process is driven by the concentration difference of analytes between the aqueous phases containing the analyte and the organic phase constituting the microdrop of a solvent. The limit of detection of HS-SDME for kerosene was 1.5 μL. Overall, the HS-SDME coupled with GC-FID proved to be rapid, simple and sensitive and a good alternative method for the analysis of accelerants in fire debris samples.     

Development of new extraction method based on liquid–liquid–liquid extraction followed by dispersive liquid–liquid microextraction for extraction of three tricyclic antidepressants in plasma samples

In the present study, a new extraction method based on a three–phase system, liquid–liquid–liquid extraction, followed by dispersive liquid–liquid microextraction has been developed and validated for the extraction and preconcentration of three commonly prescribed tricyclic antidepressant drugs – amitriptyline, imipramine, and clomipramine – in human plasma prior to their analysis by gas chromatography–flame ionization detection. The three phases were an aqueous phase (plasma), acetonitrile and n–hexane. The extraction mechanism was based on the different affinities of components of the biological sample (lipids, fatty acids, pharmaceuticals, inorganic ions, etc.) toward each of the phases. This provided high selectivity toward the analytes since most interferences were transferred into n–hexane. In this procedure, a homogeneous solution of the aqueous phase (plasma) and acetonitrile (water–soluble extraction solvent) was broken by adding sodium sulfate (as a phase separating agent) and the analytes were extracted into the fine droplets of the formed acetonitrile. Next, acetonitrile phase was mixed with 1,2–dibromoethane (as a preconcentration solvent at microliter level) and then the microextraction procedure mentioned above was performed for further enrichment of the analytes. Under the optimum extraction conditions, limits of detection and lower limits of quantification for the analytes were obtained in the ranges of 0.001–0.003 and 0.003–0.010 μg mL⁻¹, respectively. The obtained extraction recoveries were in the range of 79–98%. Intra– and inter–day precisions were < 7.5%. The validated method was successfully applied for determination of the selected drugs in human plasma samples obtained from the patients who received them.     

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.     

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%。     

Determination of the chloroacetanilide herbicides in waters using single-drop microextraction and gas chromatography

In this article, a new method using single-drop microextraction (SDME) and gas chromatography micro-electron capture detection (GC-μECD) for the determination of chloroacetanilide herbicides (alachlor, acetochlor, metolachlor, pretilachlor and butachlor) residues was developed. The effects of SDME parameters such as extraction solvent, stirring rate, ionic strength, microdrop volume and extraction time were optimized. The optimum experimental conditions found were: 1.6 μl toluene microdrop, 5 ml water sample, 400 rpm stirring rate, 15 min extraction time and no salt addition. Analytical parameters such as linearity, repeatability and limit of detection were also evaluated. The proposed method was proved to be a simple and rapid analytical procedure for chloroacetanilide herbicides in water with limits of detection 0.0002–0.114 μg/l. The relative recoveries range from 80% to 102% for all the target analytes, with the relative standard deviations varying from 3.9% to 11.7%.     

Hydrodistillation–Solvent Microextraction and GC–MS Identification of Volatile Components of Artemisia aucheri

A new, simple hydrodistillation–solvent microextraction (HD–SME) technique has been used for analysis of the volatile components of the aerial parts of Artemisia aucheri. The components were collected in a single microdrop, and this was injected directly for gas chromatographic–mass spectrometric (GC–MS) analysis. The effects on extraction efficiency of extraction solvent, sample mass, microdrop volume, and extraction time were optimized by use of a simplex method. The identities of the components of HD–SME extracts were confirmed according to their retention indexes and mass spectra with those of standards. Forty components were extracted and identified by use of the method; 1,8-cineol (22.8%), chrysanthenone (18.16%), α-pinene (8.33%), and mesitylene (7.41%) were the major constituents. The results obtained from the microextraction method were compared with those obtained by conventional hydrodistillation.     

On-Line Coupled Liquid Chromatography – Gas Chromatography in the Analysis of Process Samples

Normal phase liquid chromatography–gas chromatography was used with on-column interfacing and partially concurrent solvent evaporation in the analysis of process samples. Samples were taken from reaction mixtures, where the solvent was toluene. The analytes were oxygenated compounds: methyl isobutyrate, methyl methacrylate, methyl α-formyl isobutyrate, and methyl β-formyl isobutyrate. The analytes were transferred from LC to GC using back-flush with a solvent mixture of pentane and diethyl ether. Linearity, repeatability, and transfer efficiency were determined for the method. The method was applied in the determination of the analytes of two different process samples. The results were in good agreement with results obtained by the gas chromatographic method currently in use for the analysis of the process samples.     

Screening method for phthalate esters in water using liquid-phase microextraction based on the solidification of a floating organic microdrop combined with gas chromatography-mass spectrometry

A simple and efficient liquid-phase microextraction (LPME) technique was developed using directly suspended organic microdrop coupled with gas chromatography–mass spectrometry (GC–MS), for the extraction and the determination of phthalate esters (dimethyl phthalate, diethyl phthalate, diallyl phthalate, di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBP), dicyclohexyl phthalate and di-2-ethylhexyl phthalate (DEHP)) in water samples. Microextraction efficiency factors, such as nature and volume of the organic solvent, temperature, salt effect, stirring rate and the extraction time were investigated and optimized. Under the optimized extraction conditions (extraction solvent: 1-dodecanol; extraction temperature: 60 °C; microdrop volume: 7 μL; stirring rate: 750 rpm, without salt addition and extraction time: 25 min), figures of merit of the proposed method were evaluated. The values of the detection limit were in the range of 0.02–0.05 μg L⁻¹, while the R.S.D.% value for the analysis of 5.0 μg L⁻¹ of the analytes was below 7.7% (n = 4). A good linearity (r² ≥ 0.9940) and a broad linear range (0.05–100 μg L⁻¹) were obtained. The method exhibited enrichment factor values ranging from 307 to 412. Finally, the designed method was successfully applied for the preconcentration and determination of the studied phthalate esters in different real water samples and satisfactory results were attained.     

Deep eutectic solvent based gas‐assisted dispersive liquid‐phase microextraction combined with gas chromatography and flame ionization detection for the determination of some pesticide residues in fruit and vegetable samples

In this study, a gas‐assisted dispersive liquid‐phase microextraction method using a deep eutectic solvent as the extraction solvent combined with gas chromatography and flame ionization detection was developed for the extraction and determination of some pesticide residues in vegetable and fruit juice samples. In this method, choline chloride and 4‐chlorophenol at a molar ratio of 1:2 were mixed. By heating and vortexing, a clear, water‐immiscible, and homogeneous liquid was formed. The obtained deep eutectic solvent was added to an aqueous solution of the analytes in a conical test tube. Air was bubbled into the aqueous solution and a cloudy solution was obtained. During this step, the analytes were extracted into the fine droplets of the extraction solvent. After centrifugation, an aliquot of the settled phase was injected into the separation system. Under the optimum extraction conditions, enrichment factors, and extraction recoveries were obtained in the ranges of 247–355 and 49–71%, respectively. The obtained values for the limits of detection and quantification were in the ranges of 0.24–1.4 and 0.71–4.2 μg/L, respectively. The proposed method is simple, fast, efficient, and inexpensive.     

Hydrodistillation-headspace solvent microextraction, a new method for analysis of the essential oil components of Lavandula angustifolia Mill

A new method involving concurrent headspace solvent microextraction combined with continuous hydrodistillation (HD-HSME) for the extraction and pre-concentration of the essential oil of Lavandula angustifolia Mill. into a microdrop is developed. A microdrop of n-hexadecane containing n-heptadecane (as internal standard) extruded from the needle tip of a gas chromatographic syringe was inserted into the headspace above the plant sample. After extraction for an optimized time, the microdrop was retracted into the syringe and injected directly into a GC injection port. The effects of the type of extracting solvent, sample mass, microdrop volume and extraction time on HD-HSME efficiency were investigated and optimized. Using this method, thirty-six compounds were extracted and identified. Linalool (32.8%), linalyl acetate (17.6%), lavandulyl acetate (15.9%), alpha-terpineol (6.7%) and geranyl acetate (5.0%) were found to be the major constituents. To the best of our knowledge this is the first report on the use of continuous headspace solvent microextraction coupled with hydrodistillation for investigation of essential oil components.     

A simple and fast micromethod for the analysis of polychlorinated biphenyls in air by sorbent enrichment and ultrasound-assisted solvent extraction

A combination of sorbent enrichment and ultrasound-assisted solvent extraction has been used to determine polychlorinated biphenyls in air. Analytes were sampled by pumping a known volume of air through a porous polymer (Tenax TA). The enriched adsorbent was transferred into a glass vial, and ultrasound-assisted extraction of the analytes was then performed in n-hexane. Quantification was carried out by using gas chromatography coupled to tandem mass spectrometry. Breakthrough volume of the sampling step was studied, indicating that 10 m³ of air could be processed without losses of the most volatile compounds. Good recoveries (75–96%) were obtained, and limits of detection at the sub ng m^–3 were achieved for all the analytes. The proposed method is very simple and fast, avoiding the use of large solvent volumes and time-consuming preconcentration steps.     

Determination of Geosmin and 2-Methylisoborneol in Water by Headspace Liquid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

Geosmin (GSM) and 2-methylisoborneol (MIB) were extracted from water samples, adsorbed in organic solvent microdrop by headspace liquid-phase microextraction (HS-LPME), and were analyzed by gas chromatography-mass spectrometry (GC-MS). Influence factors such as the extraction solvent types, headspace and microdrop volumes, stirring rate, equilibrium and extraction time, and ionic strength for HS-LPME efficiency were thoroughly evaluated. Under optimized extraction and detection conditions, the calibration curves of GSM and MIB were linear in the range of 5–1000 ng/L. The detection limits of GSM and MIB were 1.1 and 1.0 ng/L, respectively. Average recoveries of 95.45–113.7% (n = 5) were obtained and method precisions were also satisfactory. Trace levels of the off-flavor compounds at ng/L in tap water and raw water were successfully quantified.