首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
This paper describes a high pressure device for filling small diameter capillaries with stationary phase solutions is described. A liquid is forced into the capillary column with the help of high pressure syringe whose needle (provided with a side opening) is tightened in a PTFE seal. The device allows use of liquefied gas as solvent. A detailed procedure is given for filling the capillary with stationary phase solution. The performance of the device was evaluated by filling 12 m × 15 μm i. d. glass capillary with 6.5 % (w/v) SE-54.  相似文献   

2.
A simple, inexpensive and disposable device for liquid-phase microextraction (LPME) is presented for use in combination with capillary gas chromatography (GC), capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). 1-4 ml samples of human urine or plasma were filled into conventional 4-ml vials, whereafter 15-25 microl of the extraction medium (acceptor solution) was filled into a short piece of a porous hollow fiber and placed into the sample vial. The drugs of interest were extracted from the sample solutions and into the small volumes of acceptor solution based on high partition coefficients and were preconcentrated by a factor of 30-125. For LPME in combination with GC, the porous hollow fiber was filled with 15 microl n-octanol as the acceptor solution. Following 30 min of extraction, the organic acceptor solution was injected directly into the GC system. For LPME in combination with CE and HPLC, n-octanol was immobilized within the pores of the hollow fiber, while the internal volume of the fiber was filled with either 25 microl of 0.1 M HCl (for extraction of basic compounds) or 25 microl 0.02 M NaOH (for acidic compounds). Following 45 min extraction, the aqueous acceptor solution was injected directly into the CE or HPLC system. Owing to the low cost, the extraction devices were disposed after a single extraction which eliminated the possibility of carry over effects. In addition, because no expensive instrumentation was required for LPME, 10-30 samples were extracted in parallel to provide a high number of samples per unit time capacity.  相似文献   

3.
Miniaturized solid-phase extraction (SPE) has been developed and successfully employed for the determination of organic species in water samples by liquid chromatography (LC). The method is based on the concept of a microscale extraction technique using a fused-silica capillary column for gas chromatography (GC), so-called in-tube solid-phase microextraction (SPME). The extraction conditions, such as the extraction time and flow-rate for the extraction and desorption process, were investigated as well as the effect of the internal structure of the extraction capillary on the efficiency. By inserting a stainless steel wire into the extraction capillary to reduce the internal volume of the capillary with the same surface area of the coating, an improved extraction and pre-concentration effects were obtained. Further pre-concentration was accomplished by the extraction device with a novel fiber-in-tube configuration. The direct coupling of the extraction method with a LC system has made it possible to determine low levels of phthalates in water samples without high consumption of organic solvents. The system developed must have potential applications for the analysis of environmental and biological samples in aqueous sample matrices.  相似文献   

4.
HPLC fractions involving eluents of low to intermediate polarity can be introduced into capillary GC using the retention gap technique. Partial or complete solvent evaporation during sample introduction reduces the length of, or almost eliminates, the zone in the column inlet (retention gap) flooded by the introduced liquid, allowing introduction of larger HPLC fractions and/or use of shorter retention gaps. The corresponding techniques are reviewed. The retention gap technique is poorly suited for water-containing HPLC eluents (reversed phase HPLC) and fails completely if HPLC eluents contain, e.g., buffer salts. Various techniques for extracting such HPLC eluents are considered, preference being given to extraction into GC stationary phases from where solutes are thermally desorbed into the GC separation column. Limiting factors are diffusion of solutes within the liquid phase to be extracted and retention power of the extraction tubes.  相似文献   

5.
In order to investigate whether the use of single-walled carbon nanotubes can improve enantioseparations on an ionic liquid stationary phase, a chiral ionic liquid, (R)-N,N,N-trimethyl-2-aminobutanol-bis(trifluoromethanesulfon)imidate, was synthesized. Two capillary columns, one containing the chiral ionic liquid and the other containing the single-walled carbon nanotubes and the chiral ionic liquid, were then prepared for GC. The results of the separations achieved with these columns show that coating the chiral ionic liquid stationary phase onto the capillary column containing single-walled carbon nanotubes improves the enantioselectivety of the chiral ionic liquid. This work indicates that using single-walled carbon nanotubes in this manner enables the application range of such GC chiral separations to be extended.  相似文献   

6.
Sample preparation, such as extraction, concentration, and isolation of analytes, greatly influences their reliable and accurate analysis. In-tube solid-phase microextraction (SPME) is a new effective sample preparation technique using an open tubular fused-silica capillary column as an extraction device. Organic compounds in aqueous samples are directly extracted and concentrated into the stationary phase of capillary columns by repeated draw/eject cycles of sample solution, and they can be directly transferred to the liquid chromatographic column. In-tube SPME is an ideal sample preparation technique because it is fast to operate, easy to automate, solvent-free, and inexpensive. On-line in-tube SPME-performed continuous extraction, concentration, desorption, and injection using an autosampler, is usually used in combination with high performance liquid chromatography and liquid chromatography-mass spectrometry. This technique has successfully been applied to the determination of various compounds such as pesticides, drugs, environmental pollutants, and food contaminants. In this review, an overview of the development of in-tube SPME technique and its applications to environmental, clinical, forensic, and food analyses are described.  相似文献   

7.
An overview is presented of methods currently in use to combine the preparation of aqueous samples on-line with capillary gas chromatography. Two approaches can be distinguished: heartcut-orientated reversed-phase liquid chromatography-gas chromatography (GC) and analyte-isolation-orientated analyte extraction-GC. These approaches either use techniques in which water is directly introduced onto the GC column, or an indirect approach in which water is eliminated, i.e., by solid-phase extraction, solid-phase microextraction or liquid-liquid extraction, prior to introduction of the analytes onto the GC column. The latter type of approach is much more successful and user friendly, and many applications have been reported.  相似文献   

8.
环境样品中硝基苯类化合物的分析方法研究进展   总被引:4,自引:0,他引:4  
主要介绍了我国近年来在环境样品中硝基苯类化合物的分析研究进展,内容包括:光度法(还原-偶氮光度法、阻抑动力学光度法、化学计量学分光光度法、人工神经网络-分光光度法)、气相色谱法(固相微萃取-毛细管气相色谱法、树脂吸附-气相色谱法、液-液微萃取气相色谱法、超声萃取-气相色谱法)、高效液相色谱法(反相高效液相色谱法、固相萃取-高效液相色谱法)和极谱法等分析方法。  相似文献   

9.
For two-dimensional reversed-phase liquid chromatography–gas chromatography (2D RPLC–GC), a specially-designed needle packed with a polymer-coated fibrous stationary phase was introduced as a novel interface. The bundle of synthetic fibers coated with polydimethylsiloxane (PDMS) was packed into the head section of the needle, and served as the extraction medium. Using the post-column dilution of the LC eluent by water and subsequent extraction with the needle interface, the analyte was successfully concentrated to the PDMS phase on the fibrous support in the needle. The concentrated analytes were directly injected to GC system by inserting the needle to a heated GC injector. 2D separations of aliphatic and aromatic hydrocarbons, and also kerosene-extract were performed with the off-line RPLC–GC system interfaced by the needle extractor. The results suggested that the fiber-packed needle interface could be one of the simple and effective approaches to develop an on-line coupled LC–GC system.  相似文献   

10.
A new and simple method of solventless extraction of volatile organic compounds (VOCs) from air is presented. The sampling device has an adsorbing carbon coating on the interior surface of a hollow needle, and is called the inside needle capillary adsorption trap (INCAT). This paper describes a study of the reproducibility in the preparation and sampling of the INCAT device. In addition, this paper examines the effects of sample volume in active sampling and exposure time in passive sampling on the analyte adsorption. Analysis was achieved by sampling the air from an environmental chamber doped with benzene, toluene, ethyl benzene and xylenes (BTEX) compounds. Initial rates of adsorption were found to vary among the different compounds, but ranged from 0.0099 to 0.016 nmol h(-1) for passive sampling and from 2.2 to 10 nmol h(-1) for active sampling. Analysis was done by thermal desorption of the adsorbed compounds directly into a gas chromatograph injection port. Quantification of the analysis was done by comparison to actively sampled activated carbon solid phase extraction (SPE) measurements.  相似文献   

11.
柳丹侠 《色谱》1997,15(2):122-124
描述了一个结合项空气流收集与无溶剂热解吸气相色谱进样的方法。用填充PorapskQ的微量注射器作为吸附管进行气流收集。将收集物不经溶剂洗脱直接进行热解吸进样。用人工合成的昆虫外激素化合物反-7-十二碳单烯乙酸酯(E-7-DA)及顺-5,反-7-十二碳二烯乙酸酯(Z-5,E-7-DDA)测定了方法的回收率,初步探索了运用于昆虫外激素分析的可行性,并讨论了提高回收率的途径。  相似文献   

12.
We report on a simple, rapid, and efficient method for the extraction of volatile organic compounds (VOCs; including methanol, tetrahydrofuran, 2-hexanone and benzene) from air and solid samples. The system is based on the use of a laboratory-made syringe as the extractor. The needle of the syringe is placed in a chamber cooled by liquid nitrogen. The tip of the needle is placed in the headspace of a vial containing the sample. The headspace components then are circulated with a pump to pass the needle, and this results in freeze-trapping of the VOCs on the inner surface of the needle. The circulation of the headspace components is continued for 15 min, and the syringe is then removed and placed in a GC injector. The effects of volume of the sample vial, headspace flow rate, temperature and time of extraction and desorption were optimized. The overall time for sampling and analysis is <30 min. The method displays an extraction efficiency of >80%) and a good sample transfer efficiency into the GC column due to the absence of a sorbent inside the needle. No carry-over was observed after 30?s desorption at 260?°C. An external standard method was used for quantitative analysis. The relative standard deviation values are below 10% and the limits of detection range from 1.3 to 4.6?ng?g?1.
Fiugre
The scheme of sorbentless cryogenic needle trap device  相似文献   

13.
Supercritical fluid extraction can be coupled with capillary gas chromatography (SFE-GC) using commercially-available on-column or split/splitless injection ports. While liquid solvent extractions require several hours or even days to perform, SFC-GC analyses can be completed in ≤ 1 hour including extraction, analyte concentration, and GC separation. SFE-GC yields chromatographic peak shapes that compare favorably with those obtained using conventional liquid solvent injections. Quantitative extraction and recovery of analytes is usually achieved in 10 minutes, and maximum sensitivity is obtained since the extracted analytes can be quantitatively transferred into the GC column for cryogenic focusing prior to GC analysis. SFE-GC analysis of a variety of organic pollutants from environmental solids and sorbent resins, and flavor and fragrance compounds from food products will be discussed.  相似文献   

14.
Simultaneous derivatization and air‐assisted liquid–liquid microextraction using an organic that is solvent lighter than water has been developed for the extraction of some parabens in different samples with the aid of a newly designed device for collecting the extractant. For this purpose, the sample solution is transferred into a glass test tube and a few microliters of acetic anhydride (as a derivatization agent) and p‐xylene (as an extraction solvent) are added to the solution. After performing the procedure, the homemade device consists of an inverse funnel with a capillary tube placed into the tube. In this step, the collected extraction solvent and a part of the aqueous solution are transferred into the device and the organic phase indwells in the capillary tube of the device. Under the optimal conditions, limits of detection and quantification for the analytes were obtained in the ranges of 0.90–2.7 and 3.0–6.1 ng/mL, respectively. The enrichment and enhancement factors were in the ranges of 370–430 and 489–660, respectively. The method precision, expressed as the relative standard deviation, was within the range of 4–6% (= 6) and 4–9% (= 4) for intra‐ and interday precisions, respectively. The proposed method was successfully used for the determination of methyl‐, ethyl‐, and propyl parabens in cosmetic, hygiene and food samples, and personal care products.  相似文献   

15.
In this study, a sorbent was immobilized inside a needle resulting in the development of a needle trap (NT) device. This device was applied to extract organic components from gaseous samples and to introduce an enriched mixture into a conventional gas chromatography (GC) injector. Construction of this simple and integrated sampling/extraction/sample introduction device was optimized by considering different ways to immobilize a sorbent in the needle, packing single and multiple-layer sorbent beds, and applying different desorption strategies into the GC injector. A carrier gas system was modified to minimize the carryover for the needle trap with a sealed tip (NT-1), and a narrow-neckliner was used for the blunt-tip needle trap (NT-2). Breakthrough in the device was investigated by connecting two NT-2 devices in series. The needle trap performed very well as an exhaustive spot sampler, as well as in a time-weighted average (TWA) operation. The linear velocity of the mobile phase has no influence on the sampling rate of the needle trap. Validation results against the standard NIOSH 1501 method using charcoal tubes for indoor air surveys demonstrated good accuracy for the NT approach. The reproducibility of the NT-2 was about 1% for benzene. The detection limits for FID detection and for 25 ml gas sample were 0.23 ng/l, 2.10 ng/l and 1.12 ng/l for benzene, ethylbenzene and o-xylene, respectively.  相似文献   

16.
文毅  汪颖  冯钰锜 《色谱》2006,24(5):471-474
建立了鸡蛋中磺胺嘧啶和磺胺二甲嘧啶残留量的聚合物整体柱微萃取和高效液相色谱检测方法。以聚(甲基丙烯酸-乙二醇二甲基丙烯酸酯)毛细管整体柱作为萃取装置。为了得到较高的萃取效率,优化了影响萃取效率的参数(萃取流速、萃取体积、样品基质pH值)。样品经过匀浆、乙醇提取、磷酸盐缓冲溶液稀释、离心等步骤后直接进行萃取。鸡蛋中磺胺嘧啶和磺胺二甲嘧啶的检出限分别为11.2 ng/g和8.8 ng/g,在50~5000 ng/g的浓度范围内具有良好的线性关系。加标回收率大于65%,日内、日间测定的相对标准偏差不高于8.2%。结果表明,方法简单、快速、灵敏度高,适用于鸡蛋中磺胺嘧啶和磺胺二甲嘧啶的常规分析。  相似文献   

17.
The usefulness and ease of utilizing supercritical fluid extraction (SFE) directly coupled to capillary gas chromatography (GC) as quantitative or qualitative analytical problem-solving tools will be demonstrated. As an alternative to conventional liquid solvent extractions, SFE presents itself as a means to achieve high extraction efficiencies of different compounds in complex solid matrices in very rapid tims frames. Moreover, SFE has an additional advantage of being able to achieve distinct extraction selectivities as a function of the solubilizing power of the supercritical fluid extracting phase. For on-line SFE/GC, the extraction effluent is directly transferred to the analytical chromatograph. On-line SFE/GC involves the decompression of pressurized extraction effluent directly into a heated, unmodified capillary split injection port of the GC. In this respect, SFE introduction into GC can be used as an alternative means of GC injection, comparable to such modes of injection as pyrolysis and thermal desorption. This paper will show applications of SFE/GC where mass spectrometric detection together with flame ionization detection was used for component identification from environmental, tobacco, and petroleum matrices.  相似文献   

18.
Two methods, one based on high-performance liquid chromatography (HPLC) and the other on gas chromatography (GC), were developed for the quantification of the partial adrenergic receptor antagonist cicloprolol. In the GC method, samples are cleaned up by back-extraction, then derivatized with heptafluorobutyric anhydride and separated on a capillary cross-linked methylsilicone column. This GC method is time-consuming but, with electron-capture detection, cicloprolol can be quantified at levels down to 1 ng/ml. The HPLC method, using a reversed ODS stationary phase and fluorimetric detection, is less sensitive (5 ng/ml) but, with a single-step extraction, is faster and simpler. The determination of cicloprolol in human blood samples by the two methods gave comparable results. Routine monitoring of cicloprolol can be done easily with the HPLC method, whereas the time-consuming GC method may be reserved for pharmacokinetic studies where late-sampled tubes, with low concentrations, must be analysed.  相似文献   

19.
An injector designed for automatic direct liquid injection into narrow bore capillary GC columns has been constructed and evaluated. The tip of the syringe needle is aligned with, and positioned close to, the column entrance in a small, pressurized cavity: when the sample is dispensed it is immediately forced into the column by the action of the surrounding carrier gas. A standard autosampler equipped with a standard stainless steel syringe needle was utilized for at-column sample transfer into 100 μm i.d. columns. RSD values for n-alkanes were between 0.1 and 0.3% for relative area counts and approximately 1% for absolute area counts.  相似文献   

20.
In this work, carbon‐nanotube‐assisted electromembrane extraction in the two‐phase mode combined with GC was developed for the preconcentration and determination of basic drugs in body fluids. The multiwalled carbon nanotubes dispersed in organic solvent are held in the pores of the porous fiber wall by capillary forces and sonification. The membrane with immobilized carbon nanotubes acts as a sorbent and provides an additional pathway for analyte transport. This study demonstrates that the immobilization of carbon nanotubes in the supported liquid membrane is an excellent approach to enhance the performance of the extraction. Optimization of the variables affecting this method was carried out in order to achieve the best extraction efficiency. Optimal extractions were accomplished with octanol as the extraction solvent, 50 V as the driving force and pH 7.4 in the sample solution with the whole assembly agitated at 1000 rpm for 20 min. Under the optimized extraction conditions, the proposed technique provided good linearity (R2 > 0.9990), repeatability (3.5–3.8%), low LODs (1.5 ng/mL), good preconcentration factors (292–316) and high recoveries (80–87%). Finally, this method was successfully used for the determination of tramadol and methadone in different body fluids including plasma and urine samples.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号