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1.
A novel analytical procedure has been developed for the analysis of ultra trace levels of 1,2-dichloroethane (EDC) in air using sample enrichment in combination with micromachined gas chromatography (GC) and differential mobility detection (DMD). When compared to other contemporary GC techniques, such as GC-flame ionization detection, GC-electron capture detection, or GC-electrolytic conductivity detection, the employment of a DMD in combination with a preconcentrator provided better sensitivity and markedly improved selectivity. The increase in sensitivity reduces false-negative results, while the improvement in selectivity decreases the potential for false-positive results. Using the technique described, a complete analysis can be conducted in less than 10 min, with a detection limit of 0.7 ppb (v/v) of EDC and a short term precision of less than 6%. A correlation coefficient of 0.9988 was obtained over an EDC concentration range from 0.7 ppb to 36.4 ppb (v/v). The analytical system also has an on-board microTCD in series with the DMD, allowing both detector outputs to be monitored simultaneously. With the pre-concentration technique, the microTCD can detect EDC as low as 15 ppb (v/v) with a substantially enhanced linear dynamic range in addition to providing a confirmation means for the presence of EDC at the level cited.  相似文献   

2.
Stability constants of complexes of Ag(I) and Cu(II) perchlorates and nitrates with some macrocyclic compounds in 90 and 75% (v/v) DMSO+water and 75% (v/v) DMF+water media have been determined by potentiometry. Silver and copper wires, and Coated Wire Ion Selective Electrodes (CWISE) were used as indicator electrodes. It was observed that complexation is stronger when the salt is present as a perchlorate than when it is as a nitrate. For both cations the stability constant values in 75% (v/v) DMF+water were somewhat higher than in 75% (v/v) DMSO. The macrocyclic effect due to cyclization of linear amine tosylates has been observed. Competitive potentiometry has been utilized to compare some of the results.  相似文献   

3.
脑区神经递质的测定对于研究神经系统的作用机制具有重要意义。该研究建立了同位素内标稀释-超高效液相色谱-串联质谱同时测定双酚A暴露后大鼠海马体中5种神经递质含量的方法,包括谷氨酸、γ-氨基丁酸、乙酰胆碱、多巴胺以及5-羟色胺。选用2%(体积分数)乙酸水-甲醇(9:1,v/v)溶液配制标准样品及溶解样品,以Ultimate AQ-C18(150 mm×4.6 mm,3 μ m)为分离柱,0.1%(体积分数)甲酸水和甲醇为流动相,在28℃柱温下,梯度洗脱,所有化合物在3 min内出峰。添加维生素C能显著减少多巴胺和5-羟色胺在前处理以及样品储存过程中的氧化,极大地提高神经递质的稳定性,从而准确定量。该方法标准曲线线性关系良好,相关系数R2>0.998,检出限和定量限低,日内和日间精密度为0.39%~13.6%,加标回收率为92.9%~119%,实际进样残留低,已被成功地应用于新生期双酚A暴露后大鼠海马体神经递质含量的测定。  相似文献   

4.
Summary For the title compounds 4,4-DADPM, MOCA, 3,3-DCB, 4-ADP and 4-ADPA listing on the EPA priority pollutant list, an analytical practicable, reliable, reproducible and sensitive procedure is required. Therefore a new method has been developed for the routine determination of these toxic aromatic amines in urine at the ppb level. The quantitative determination of amines is a suitable procedure of occupationally exposed persons. Urine sample preparation is done using simple liquid-liquid extraction followed by a precolumn enrichment (PRP1-material; Hamilton). Breakthrough measurements were done using an enrichment column packed with PRP1 material. The capacities of the studied amines ranged from 21.9mg/g to 96.6mg/g, while influent concentrations differed from 28.3mg/l to 332.0mg/l. The advantages of electrochemical detection regarding to selectivity and sensitivity are clearly indicated in this paper. Separation has been achieved applying reversed-phase-high-performance-liquid chromatography (LiChrosorb RP 18/5m) followed by electrochemical or UV-detection. The detection limits employing an electrochemical detector at a potential of 1 V range from 2.2ng to 12.1ng. UV detection at 254 nm and 280 nm is about 10–100 times less sensitive. Recoveries from spiked water samples at the 5ppb levels were 75% to 96% respectively. The standard deviation of the developed procedure varies from 5.3% to 14%. Day-to-day repeatability is good.  相似文献   

5.
Riaz A  Kim B  Chung DS 《Electrophoresis》2003,24(16):2788-2795
Trace metal ions in highly saline samples such as urine were determined with capillary electrophoresis (CE) without desalting or off-line preconcentration. By mixing with a dye, 4-(2-pyridylazo) resorcinol (PAR), the metal ions were converted into anionic complexes having strong absorbance near 500 nm. A large volume of the metal-PAR complex sample solution injected into a coated capillary was stacked isotachophoretically and separated under a reverse potential. The salt anion (chloride) and PAR in the sample matrix acted as the leading and terminating electrolytes, respectively. In a sample containing a 250 mM NaCl matrix, more than 400-fold enhancement in the absorbance detector response was realized compared to the normal CE injection mode. Combination of the dye complexation and isotachophoretic stacking provided excellent detection limits (S/N = 3) for three trace metal ions in the low ppb range (Fe(2+), 0.7 ppb, Ni(2+), 0.4 ppb; Zn(2+), 1.2 ppb) with absorbance detection. The migration time reproducibility was excellent (relative standard deviations: standard samples < 1%, urine samples approximately 1%). The proposed method is convenient and fast, and the sample analysis can be completed within 20 min.  相似文献   

6.
Water disinfection byproducts (DBPs) are a class of chemicals that are produced when chemical disinfectants react with organic materials in untreated water. Cytotoxicity and genotoxicity of DBPs have been systematically evaluated to compile a comparative, quantitative database of in vitro mammalian cell toxicity of DBPs. However, one of the most challenging limitations for current DBP cytotoxicity assessment assays is sample availability. Although our current cytotoxicity assay using a 96-well microplate has been designed to reduce sample consumption, further minimization of the size of the test system would allow us to explore various possibilities for point-of-care applications. We have developed a microfluidic device with micro-pillars that shows high uniformity in distribution of cells across all chambers with low cell count. We compare the performance between the 96-well microplate and the microfluidic device by running 72-hour standalone-on-chip cell culture and cytotoxicity analysis experiments, using dimethyl sulfoxide (DMSO) and ethanol as model toxic agents, and bromoacetic acid (BAA) as a representative DBP. The results show close agreement between the two systems. The measured LC(50) values for the 96-well microplate and the microfluidic device are 1.54% v/v and 1.27% v/v for DMSO, 1.44% v/v and 2.92% v/v for ethanol, and 17.6 μM and 8.20 μM for BAA, respectively. The micro-pillar microfluidic device offers a great reduction in sample consumption while maintaining the accuracy of the cytotoxicity analyses of water disinfection byproducts.  相似文献   

7.
Msagati TA  Nindi MM 《Talanta》2004,64(1):87-100
A high performance liquid chromatography (HPLC) coupled to a mass spectrometer (MS) was used for a simultaneous determination of 16 sulfonamide compounds spiked in water, urine, milk, and bovine liver and kidney tissues. Supported liquid membrane (SLM) made up of 5% tri-n-octylphosphine oxide (TOPO) dissolved in hexyl amine was used as a sample clean-up and/or enrichment technique. The sulfonamides mixture was made up of 5-sulfaminouracil, sulfaguanidine, sulfamethoxazole, sulfamerazine, sulfamethizole, sulfamethazine (sulfadimidine), sulfacetamide, sulfapyridine, sulfabenzamide, sulfamethoxypyridazine, sulfamonomethoxine, sulfadimethoxine sulfasalazine, sulfaquinoxaline, sulfadiazine, and sulfathiazole. Some of these compounds, such as, sulfaquinoxaline, sulfadiazine, sulfabenzamide, sulfathiazole and sulfapyridine failed to be trapped efficiently by the same liquid membrane (5% TOPO in hexylamine). The detection limits (DL) obtained were 1.8 ppb for sulfaguanidine and sulfamerazine and between 3.3 and 10 ppb in bovine liver and kidney tissues for the other sulfonamides that were successfully enriched with SLM; 2.1 ppb for sulfaguanidine and sulfamerazine and between 7.5 and 15 ppb in cow’s urine, whereas the DL values in milk were 12.4 ppb for sulfaguanidine and sulfamerazine and between 16.8 and 24.3 for the other compounds that were successfully enriched by the membrane. Several factors affecting the extraction efficiency during SLM enrichment, such as donor pH, acceptor pH, enrichment time and the membrane solvent were studied.  相似文献   

8.
Pai YF  Lin CC  Liu CY 《Electrophoresis》2004,25(4-5):569-577
A wall-coated histidine capillary column was developed for the on-line preconcentration of nonsteroidal anti-inflammatory drugs (NSAIDs) in capillary electrochromatography (CEC). A wide variety of experimental parameters, such as the sample buffer, background electrolyte (BGE) composition, concentration, sample plug lengths, water plug, and the effect of organic modifiers were studied. The relationship between peak height and injection times for the NSAIDs by variation of sample and BGE buffer concentration was investigated. On addition of sodium chloride (0.3-0.6%) to the sample zone, the stacking efficiency was increased. With acetate buffer (100 mM, pH 5.0)/ethanol (20% v/v) as BGE and sample solution in acetate buffer (0.2 mM, pH 5.0)/ethanol (20% v/v)/NaCl (0.3% w/v), NSAIDs could be determined at low microM levels without sample matrix removal. The detection limit was 0.096 microM for indoprofen, 0.110 microM for ketoprofen, 0.012 microM for naproxen, 0.023 microM for ibuprofen, 0.110 microM for fenoprofen, 0.140 microM for flurbiprofen, and 0.120 microM for suprofen. The method could be successfully applied to the simultaneous determination of NSAIDs in urine. The recoveries were better than 82% for all the analytes. The present method enables simple manipulation with UV detection for the determination of NSAIDs at low concentration levels in complex matrix samples.  相似文献   

9.
A practical gas chromatographic procedure has been developed and implemented for the measurement of arsine and phosphine in hydrocarbons such as propylene at the part-per-billion level. The successful measurement of arsine and phosphine at the level mentioned was attained by incorporating a large volume injection technique to increase the mass of solutes delivered for sensitivity improvement, capillary flow technology to keep the matrix from entering the detector by either back-flushing through the inlet vent, or by heart-cutting if required, and dielectric barrier discharge detector operating in argon mode for sensitivity enhancement, as well as offering improved selectivity towards the solutes cited. Using the technique described a complete analysis can be conducted in less than 4 min. A relative standard precision of less than 1.7% was achieved with repeated injections at the concentration level of 25 and 125 ppb (v/v) each of arsine and phosphine in nitrogen with a practical detection limit at the 5 ppb (v/v) level. Correlation coefficients of greater than 0.9999 were obtained for arsine and phosphine over a range from 10 to 2500 ppb (v/v). The analytical methodology was proven to be reliable in continuous operation during the first 6 months of deployment.  相似文献   

10.
A theoretical treatment was developed and validated that relates analyte concentration and mass sensitivities to injection volume, retention factor, particle diameter, column length, column inner diameter and detection wavelength in liquid chromatography, and sample volume and extracted volume in solid‐phase extraction (SPE). The principles were applied to improve sensitivity for trace analysis of clopyralid in drinking water. It was demonstrated that a concentration limit of detection of 0.02 ppb (μg/L) for clopyralid could be achieved with the use of simple UV detection and 100 mL of a spiked drinking water sample. This enabled reliable quantitation of clopyralid at the targeted 0.1 ppb level. Using a buffered solution as the elution solvent (potassium acetate buffer, pH 4.5, containing 10% of methanol) in the SPE procedures was found superior to using 100% methanol, as it provided better extraction recovery (70–90%) and precision (5% for a concentration at 0.1 ppb level). In addition, the eluted sample was in a weaker solvent than the mobile phase, permitting the direct injection of the extracted sample, which enabled a faster cycle time of the overall analysis. Excluding the preparation of calibration standards, the analysis of a single sample, including acidification, extraction, elution and LC run, could be completed in 1 h. The method was used successfully for the determination of clopyralid in over 200 clopyralid monoethanolamine‐fortified drinking water samples, which were treated with various water treatment resins.  相似文献   

11.
A monitor for continuous analysis of sulphur dioxide in the atmosphere at the ppb v/v level (1 ppb v/v = 2.62 g/m3 SO2) is described. The apparatus operates on the principle of equilibrium accumulation of sulphur dioxide from the air by a polydispersive water aerosol which continuously transfers SO2 from an air-flow of l/min into microlitre volumes of water condensate. High sensitivity (1 ppb v/v), low relative error (± 5% at 4 ppb v/v SO2), high selectivity (CO2 does not interfere at a concentration of 2 × 103 ppm v/v, interference by NO x and H2S is acceptably low), and low response delay (10 s) are provided by a compact coupling of the enrichment procedure with conductivity detection of SO2 in the film of water aerosol condensate formed directly on the wire-gauze sensor. The reliability of the method has been studied under simulated conditions, with spectrophotometric method as reference. The analyser is computer-controlled, and the detector response is processed on-line and displayed (as g/m3) in real-time on a screen or is transmitted telemetrically to a control centre. It is portable and suitable for use in both stationary and moving locations.The paper is dedicated to the 65th anniversary of the birthday of Prof. Josef F. K. Huber  相似文献   

12.
This paper describes a new analytical system, based on the combination of continuous flow liquid membrane extraction (CFLME) enrichment and capillary electrophoresis (CE) separation, for analysis of chlorinated phenols in water samples. Five chlorinated phenols including 3-chlorophenol (3CP), 4-chlorophenol (4CP) 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) were separated by CE with Tris/sodium dihydrogen phosphate solution containing methanol 1% (v/v) as the run buffer. CFLME related parameters were investigated and optimal enrichment was obtained by using 0.3 mol L(-1) Tris as acceptor and with a sample pH 5.0, a sample flow rate of 4.0 mL min(-1), and an enrichment sample volume of 150 mL. The detection limit (S/N= 3) was 6.9, 1.0, and 1.7 ng mL(-1) for DCP, PCP, and TCP, respectively. The reproducibility (RSD%, n = 6) was 5.7 for DCP, 2.5 for PCP, and 2.8% for TCP (n = 6). The proposed method was applied to the determination of chlorinated phenols in spiked water samples with relatively satisfactory recoveries.  相似文献   

13.
Polycyclic aromatic hydrocarbons (PAHs) are USEPA regulated priority pollutants. Their low aqueous solubility requires very sensitive analytical methods for their detection, typically involving preconcentration steps. Presented is the first demonstrated ‘proof of concept’ use of condensed phase membrane introduction mass spectrometry (CP-MIMS) coupled with direct liquid electron ionization (DEI) for the direct, on-line measurement of PAHs in aqueous samples. DEI is very well suited for the ionization of PAHs and other nonpolar compounds, and is not significantly influenced by the co-elution of matrix components. Linear calibration data for low ppb levels of aqueous naphthalene, anthracene, and pyrene is demonstrated, with measured detection limits of 4 ppb. Analytical response times (t10%–90% signal rise) ranged from 2.8 min for naphthalene to 4.7 min for pyrene. Both intra- and interday reproducibility has been assessed (<3% and 5% RSD, respectively). Direct measurements of ppb level PAHs spiked in a variety of real, complex environmental sample matrices is examined, including natural waters, sea waters, and a hydrocarbon extraction production waste water sample. For these spiked, complex samples, direct PAH measurement by CP-MIMS-DEI yielded minimal signal suppression from sample matrix effects (81%–104%). We demonstrate the use of this analytical approach to directly monitor real-time changes in aqueous PAH concentrations with potential applications for continuous on-line monitoring strategies and binding/adsorption studies in heterogeneous samples.
Graphical Abstract ?
  相似文献   

14.
《Analytical letters》2012,45(15):3083-3110
ABSTRACT

A solid phase extraction (SPE) system has been modified with cationic surfactants and evaluated for extraction and preconcentration of trace phenolic compounds contaminants in water at low ppb concentrations. Cationic surfactants such as cetyl trimethyl ammonium bromide (CTAB) has been steadily adsorbed on the surface of C-18 bonded silica, and the ionized functional group of the surfactant can then act as an ion–exchange site to attract the ionized phenolic compounds from water samples. The method includes enrichment of the phenolic compounds by the surfactant-loaded solid phase extraction system, followed by elution of the analyte with methylene chloride and derivatization of the phenolic compounds with acetic anhydride. Thirty-two phenolic analytes were identified and quantitatively determined by this method; identification and quantification of the compounds is performed with GC/FID using 2-bromophenol as internal standard. SPME analysis with this method was linear over 3-6 orders of magnitude, with linear correlation coefficient (R2) greater than 0.96. Experimentally determined FID detection limits ranged from ~30 ppt for methyl-substituted phenols to ~0.1ppb for phenol and chloro-substituted phenols. We tested the influence of sample pH, the loading amount of surfactant on the solid phase, and the volume and matrixes of the sample were studied. Absolute recoveries from pure water spiked with 0.2 ppb phenolic compounds were 96 – 103%. The method has been applied to analysis of various natural waters, including ground water, lake water, seawater, and wastewater. Recoveries from ground water, lake water, seawater, and wastewater were 92 – 106%, 75 – 93%, 87 – 103%, 86 – 99%, respectively. Therefore, the new technique proved to be an excellent tool for trace enrichments of phenolic compounds at low ppb concentration of these analytes, from different natural water samples.  相似文献   

15.
The potential of online trace enrichment on a highly apolar short column in LC was evaluated for the determination of pyrethroids in river water. Twelve millilitres of water samples, modified with 8 mL ACN (ACN/water 40:60, v/v), were passed through 50 x 4.6 mm ID first separation column packed with 5 microm Hypersil Elite C18. Pesticides were preconcentrated in this column while the matrix background was eluted to waste. Separation of pesticides was performed on a 3.5 microm symmetric C18 column (250 x 4.6 mm ID) with an ACN step gradient as mobile phase and fluorescence detection was used after postcolumn derivatization by using UV light. The use of photochemically induced fluorescence for detection improved sensitivity and selectivity. Quantification limits ranged from 0.05 to 0.1 microg/L and pesticide recoveries at two concentration levels (0.1 and 0.5 microg/L) were between 93.1 and 118.6%, with RSD between 2.5 and 7.5% (n = 3) in river water samples. No matrix effect was detected.  相似文献   

16.
An instrumental set up including on-line solid-phase extraction, nano-liquid chromatography, and nanospray mass spectrometry is constructed to improve the sensitivity for quantitation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in surface water. Sample volumes of 1000 microL are loaded onto a microbore 1.0-mm i.d. x 5 mm, 5 microm Kromasil C(18) enrichment column by a carrier solution consisting of 10mM ammonium acetate in acetonitrile-water (10:90, v/v) at a flow rate of 250 microL/min, providing on-line analyte enrichment and sample clean-up. Backflushed elution onto a 0.1-mm i.d. x 150 mm, 3.5 microm Kromasil C(18) analytical column is conducted using an acetonitrile-10mM ammonium acetate solvent gradient from 30% to 70% acetonitrile. Water samples are added with internal standard (perfluoroheptanoic acid) and filtrated prior to injection. The mass limits of detection of PFOA and PFOS are 0.5 and 1 pg, respectively, corresponding to concentration limits of detection of 500 pg/L and 1 ng/L, respectively. The total time spent on sample preparation, chromatography, and detection is approximately 12 min per sample. The method was employed for the determination of PFOS and PFOA in urban river water.  相似文献   

17.
The feasibility of fabricating copper-sensitive chemically modified electrodes (CMEs) for trace analysis in aqueous and in 40% (v/v) ethanol-water media was investigated. Carbon paste electrodes modified with crown ethers were constructed by mixing the crown ethers into a graphite powder-paraffin oil matrix. The electrodes so formed were able to bind Cu(II) ions chemically and gave better voltammetric responses than the unmodified ones. The crown ethers studied and compared were 15-crown-5, benzo-15-crown-5 and dibenzo-18-crown-6. With a 3% benzo-15-crown-5 CME, Cu(II) could be quantified at sub-ppm levels by differential pulse voltammetry with a detection limit of 0.05 ppm. By differential pulse anodic stripping voltammetry Cu(II) could be quantified over the range I to 100 ppb. Interference from metal ions like Ni(II), Co(II), Mn(II), Fe(II), etc. have also been studied. The method was successfully applied to artificial as well as commercial samples of alcoholic beverages.  相似文献   

18.
The feasibility of fabricating copper-sensitive chemically modified electrodes (CMEs) for trace analysis in aqueous and in 40% (v/v) ethanol-water media was investigated. Carbon paste electrodes modified with crown ethers were constructed by mixing the crown ethers into a graphite powder-paraffin oil matrix. The electrodes so formed were able to bind Cu(II) ions chemically and gave better voltammetric responses than the unmodified ones. The crown ethers studied and compared were 15-crown-5, benzo-15-crown-5 and dibenzo-18-crown-6. With a 3% benzo-15-crown-5 CME, Cu(II) could be quantified at sub-ppm levels by differential pulse voltammetry with a detection limit of 0.05 ppm. By differential pulse anodic stripping voltammetry Cu(II) could be quantified over the range 1 to 100 ppb. Interference from metal ions like Ni(II), Co(II), Mn(II), Fe(II), etc. have also been studied. The method was successfully applied to artificial as well as commercial samples of alcoholic beverages. Received: 12 January 2000 / Revised: 14 March 2000 / Accepted: 16 March 2000  相似文献   

19.
A simple detection method using ultra-performance liquid chromatography electrospray ionisation tandem mass spectrometry (UPLC-ESI-MS-MS) coupled with the sample dilution method for determining trace microcystin-LR (MC-LR) in drinking water is presented. The limit of detection (LOD) was 0.04 μg/L and the limit of quantitation (LOQ) was 0.1 μg/L. Water matrix effects of ionic strength, dissolved organic carbon (DOC) and pH were examined. The results indicate that signal detection intensity for MC-LR was significantly suppressed as the ionic strength increased from ultrapure water condition, whereas it increased slightly with solution pH and DOC at low concentrations. However, addition of methanol (MeOH) into the sample was able to counter the signal suppression effects. In this study, dilution of the tap water sample by adding 4% MeOH (v/v) was observed to be adequate to compensate for the signal suppression. The recoveries of the samples fortified with MC-LR (0.2, 1, and 10 μg/L) for three different tap water samples ranged from 84.4% to 112.9%.  相似文献   

20.
A novel approach for the determination of parts‐per‐billion level of 5‐hydroxymethyl‐2‐furaldehyde, furfuryl alcohol, furfural, 2‐furyl methyl ketone, and 5‐methylfurfural in transformer or rectifier oils has been successfully innovated and implemented. Various extraction methods including solid‐phase extraction, liquid–liquid extraction using methanol, acetonitrile, and water were studied. Water was by far the most efficient solvent for use as an extraction medium. Separation of the analytes was conducted using a 4.6 mm × 250 mm × 3.5 μm Agilent Zorbax column while detection and quantitation were conducted with a variable wavelength UV detector. Detection limits of all furans were at 1 ppb v/v with linear ranges range from 5 to 1000 ppb v/v with correlation coefficients of 0.997 or better. A relative standard deviation of at most 2.4% at 1000 ppb v/v and 7.3% at 5 ppb v/v and a recovery from 43% to 90% depending on the analyte monitored were obtained. The method was purposely designed to be environmental friendly with water as an extraction medium. Also, the method uses 80% water and 20% acetonitrile with a mere 0.2 mL/min of acetonitrile in an acetonitrile/water mixture as mobile phase. The analytical technique has been demonstrated to be highly reliable with low cost of ownership, suitable for deployment in quality control labs or in regions where available analytical resources and solvents are difficult to procure.  相似文献   

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