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1.
Competitive adsorption on adsorptive solid-phase microextraction (SPME) fibres implies careful determination of operating conditions for reliable quantitative analysis of VOCs in indoor air. With this objective, two analytical approaches, involving non-equilibrium and equilibrium extraction, were compared. The average detection limit obtained for GC-MS analysis of nine VOCs by the equilibrium method is 0.2 μg m−3, compared with 1.9 μg m−3 with the non-equilibrium method. The effect of the relative humidity of the air on the calibration plots was studied, and shown to affect acetone adsorption only. Hence, the concentrations that can be accurately determined are up to 9 μmol m−3. The methods were then applied to indoor air containing different concentrations of VOCs. The non-equilibrium method, involving short extraction time, can be used for detection of pollution peaks whereas equilibrium extraction is preferable for measurement of sub-μg m−3 ground concentration levels.   相似文献   

2.
Eight PM10 aerosol samples were collected in the vicinity of the “Mario Zucchelli” Italian Antarctic Station (formerly Terra Nova Bay Station) during the 2000–2001 austral summer using a high-volume sampler and precleaned cellulose filters. The aerosol mass was determined by differential weighing of filters carried out in a clean chemistry laboratory under controlled temperature and humidity. A two-step sequential extraction procedure was used to separate the water-soluble and the insoluble (dilute-HCl-extractable) fractions. Cd, Pb and Cu were determined in the two fractions using an ultrasensitive square wave anodic stripping voltammetric (SWASV) procedure set up for and applied to aerosol samples for the first time. Total extractable metals showed maxima at midsummer for Cd and Pb and a less clear trend for Cu. In particular, particulate metal concentrations ranged as follows: Cd 0.84–9.2 μg g−1 (average 4.7 μg g−1), Pb 13.2–81 μg g−1 (average 33 μg g−1), Cu 126–628 μg g−1 (average 378 μg g−1). In terms of atmospheric concentration, the values were: Cd 0.55–6.3 pg m−3 (average 3.4 pg m−3), Pb 8.7–48 pg m−3 (average 24 pg m−3), Cu 75–365 pg m−3 (average 266 pg m−3). At the beginning of the season the three metals appear widely distributed in the insoluble (HCl-extractable) fraction (higher proportions for Cd and Pb, 90–100%, and lower for Cu, 70–90%) with maxima in the second half of December. The soluble fraction then increases, and at the end of the season Cd and Pb are approximately equidistributed between the two fractions, while for Cu the soluble fraction reaches its maximum level of 36%. Practically negligible contributions are estimated for crustal and sea-spray sources. Low but significant volcanic contributions are estimated for Cd and Pb (∼10% and ∼5%, respectively), while there is an evident although not quantified marine biogenic source, at least for Cd. The estimated natural contributions (possibly including the marine biogenic source) cannot account for the high fractions of the metal contents, particularly for Pb and Cu, and this suggests that pollution from long-range transport is the dominant source. Figure Aerosol sampling in Antarctica  相似文献   

3.
Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NOx-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO2/m3. The detection limit for the passive sampler is 1 μg NO2/m3 (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NOx-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO2/m3, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%. Received: 3 December 1996 / Revised: 11 March 1997 / Accepted: 15 March 1997  相似文献   

4.
Bombesin (BNN)-like peptides have very high binding affinity for the gastrin-releasing peptide (GRP) receptor. The goal of the current study was to optimize the labeling conditions of a new 99mTc-radiolabeled BNN-like peptide based on the bifunctional chelating ligand HYNIC using different co-ligands (EDDA and tricine). The radiolabeling conditions (pH, amount of co-ligand, amount of stannous chloride, temperature and reaction time) for newly-formed 99mTc-tricine-HYNIC-Q-Litorin and 99mTc-EDDA-HYNIC-Q-Litorin were optimized and evaluated by RHPLC and RTLC. Radiochemical yields for 99mTc-tricine-HYNIC-Q-Litorin and 99mTc-EDDA-HYNIC-Q-Litorin were 98.0 ± 1.7 and 97.5 ± 2.5%, respectively. When EDDA was used as co-ligand, the labeling of 99mTc-EDDA-HYNIC-Q-Litorin was optimal in the following reaction mixture: HYNIC-peptide: EDDA: 10 μg/5 mg, pH 3, SnCl2 concentration: 12 μg/0.1 mL, reaction temperature: 100 °C, reaction time: 15 min. Besides, the optimum conditions were HYNIC-peptide:tricine: 10 μg/50 mg, pH 5, SnCl2 concentration: 12 μg/0.1 mL, reaction temperature: 100 °C, reaction time: 15 min for preparing 99mTc-tricine-HYNIC-Q-Litorin. The manufactured 99mTc-HYNIC-Q-Litorin conjugates may offer new possibilities for imaging cancer cells expressing bombesin receptors.  相似文献   

5.
Guanidinoacetate methyltransferase deficiency is a recently discovered inborn defect of creatine biosynthesis which reduces serum creatinine concentrations to as low as 0.58 μg mL−1 (or 0.00058 μg mL−1 after 1,000-fold dilution). To measure ultra trace levels of creatinine in diluted samples, molecularly imprinted solid-phase extraction (MISPE) and molecularly imprinted polymer (MIP) sensor techniques have been found to be inadequate. A combination of these techniques (i.e. MISPE hyphenated with use of an MIP-sensor), reported in this paper, has been found to be highly suitable for direct assay of creatinine in highly diluted human blood serum without complicated pretreatment of the sample. The proposed technique has the potential to enhance the sensitivity of creatinine measurement from μg mL−1 to ng mL−1 in highly dilute aqueous samples in which the concentrations of interfering constituents are reduced to negligible levels. In this work the sensitivity to creatinine was found to be improved compared with that of the MIP-sensor method alone (limit of detection, LOD, 0.00149 μg mL−1). After preconcentration by MISPE and use of the sensor the detection limit for creatinine was as low as 0.00003 μg mL−1 (RSD = 0.94%, S/N = 3; 50-fold preconcentration factor) in aqueous samples.  相似文献   

6.
An electrospray ionization tandem mass spectrometric (ESI-MS-MS) method has been developed for the determination of cyanide (CN) in blood. Five microliters of blood was hemolyzed with 50 μL of water, then 5 μL of 1 M tetramethylammonium hydroxide solution was added to raise the pH of the hemolysate and to liberate CN from methemoglobin. CN was then reacted with NaAuCl4 to produce dicyanogold, Au(CN)2, that was extracted with 75 μL of methyl isobutyl ketone. Ten microliters of the extract was injected directly into an ESI-MS-MS instrument and quantification of CN was performed by selected reaction monitoring of the product ion CN at m/z 26, derived from the precursor ion Au(CN)2 at m/z 249. CN could be measured in the quantification range of 2.60 to 260 μg/L with the limit of detection at 0.56 μg/L in blood. This method was applied to the analysis of clinical samples and the concentrations of CN in the blood were as follows: 7.13 ± 2.41 μg/L for six healthy non-smokers, 3.08 ± 1.12 μg/L for six CO gas victims, 730 ± 867 μg for 21 house fire victims, and 3,030 ± 97 μg/L for a victim who ingested NaCN. The increase of CN in the blood of a victim who ingested NaN3 was confirmed using MS-MS for the first time, and the concentrations of CN in the blood, gastric content and urine were 78.5 ± 5.5, 11.8 ± 0.5, and 11.4 ± 0.8 μg/L, respectively.  相似文献   

7.
A new method was developed for the simultaneous determination of lidocaine, proline and lomefloxacin in human urine by capillary electrophoresis-electrochemiluminescence detection with Ru(bpy)3 2+. Conditions of the separation and detection were investigated and optimized. It was proved that 20 mM phosphate buffer at pH 6.7 could achieve the most favorable resolution, and the high sensitivity of detection was obtained by using the detection potential at 1.15 V and 5 mM Ru(bpy)3 2+–60 mM phosphate buffer at pH 7.6 in the detection reservoir. The detection limits were 0.02 μg mL−1 for lidocaine, 0.03 μg mL−1 for proline and 0.06 μg mL−1 for lomefloxacin. Relative standard deviations of the ECL intensity and the migration time were 3.5 and 1.1% for 6 μg mL−1 lidocaine, 3.2 and 1.0% for 6 μg mL−1 proline and 3.7 and 1.2% for 6 μg mL−1 lomefloxacin, respectively. A baseline separation for lidocaine, proline and lomefloxacin was achieved within 360 s. The developed method was successfully applied to determine the amounts of lidocaine, proline and lomefloxacin in human urine. The recovery and RSD were in the range of 93.3–97.2 and 3.8–4.9%, respectively.  相似文献   

8.
A personalized, miniaturized air sampling system was evaluated to estimate the daily exposure of pediatric asthmatics to nitrogen dioxide (NO2). The lightweight device (170 g) uses a sampling pump connected to a solid sorbent tube containing triethanolamine (TEA)-impregnated molecular sieve. The pump is powered by a 9 V battery and samples air over a 24 h period at a collection rate of 0.100 L/min. After exposure, the solid sorbent is removed from the tubes for spectrophotometric analysis (Griess Assay). The lower detection limit of the overall method for NO2 is 11 μg/m3. The linearity, precision and accuracy of the sampler was evaluated. Different NO2 concentrations generated in the laboratory (range: 50 to 340 μg/m3) were simultaneously measured by the TEA tube samplers and colocated continuous chemiluminescent NOx analyzers (reference method). The coefficient of determination for the laboratory test derived from ordinary linear regression (OLR) was r 2=0.99 (y OLR=0.94x−4.58) and the precision 3.6%. Further, ambient NO2 concentrations in the field (range: 10–120 μg/m3) were verified with continuous chemiluminescent monitors next to the active samplers. Reweighted least squares analysis (RLS) based on the least median squares procedure (LMS) resulted in a correlation of r 2=0.68 for a field comparison in Riverside, CA (y RLS=1.01x−0.94) and r 2=0.92 in Los Angeles, CA (y RLS=1.31x−7.12). The precision of the TEA tube devices was 7.4% (at 20–60 μg/m3 NO2) under outdoor conditions. Data show that the performance of this small active sampling system was satisfactory for measuring environmental concentrations of NO2 under laboratory and field conditions. It is useful for personal monitoring of NO2 in environmental epidemiology studies where daily measurements are desired.  相似文献   

9.
The cadmium ratios of 52 short-lived nuclides have been measured. Epithermal neutron irradiation reduces the activities of20F,27Mg,28Al,38Cl,49Ca,46mSc,51Ti,56Mn and66Cu by factors of 20–30. The calculated improvements in detection limits for Ga, Br, Rb, Y, Mo, Rh, Pd, Ag, In, Sn, Sb, I, Ba, Nd, Sm, Gd, Dy, Er, Yb, Hf, W, Re, Pt, Au, Th and U are in the range 1–6. Hafnium was measured in USGS rocks: AGV-1 (4.9 μg g−1), G-2 (7.5 μg g−1) and GSP-1 (14.7 μg g−1) and IAEA standards: SOIL-5 (6.3 μg g−1 and SL-1 (4.6 μg g−1). CCRMP reference concentrates PTC and PTM were analysed for rhodium (1.1 and 0.75 μg g−1, respectively) and silver (69 and 5.8 μg g−1, respectively).  相似文献   

10.
Mesoporous Ni hydroxynitrates were synthesized from a hydrothermal mixture of Ni nitrate, octylamine as the surfactant, ethanol and water at 25–100 °C for 24 h. Mesoporous Ni oxides were obtained by calcining the Ni hydroxynitrates in air at temperatures ranging from 200 to 500 °C for 2 h. The mesoporous Ni oxides have crystalline walls, a high surface area of 133 m2/g at 350 °C, high porosity up to 0.61 cm3/g, and a bimodal mesopore size distribution, with pores roughly 2 and 10–25 nm in diameter. With an increase in the synthesis temperature, the size of the larger pores and the total pore volume of the mesoporous Ni oxide increase, while the surface area decreases slightly from 133 (25 °C) to 111 m2/g (100 °C).  相似文献   

11.
Protein can greatly enhance the fluorescence of curcumin (CU) in the presence of sodium dodecyl benzene sulfonate (SDBS). Experiments indicate that under the optimum conditions, the enhanced intensity of fluorescence is proportional to the concentration of proteins in the range of 0.0050–20.0 μg mL−1 for bovine serum albumin (BSA), 0.080–20.0 μg mL−1 for human serum albumin (HSA), and 0.040–28.0 μg mL−1 for egg albumin (EA). Their detection limits (S/N=3) are 1.4 ng mL−1, 20 ng mL−1, and 16 ng mL−1, respectively. The method has been satisfactorily used for the determination of proteins in actual samples. In comparison with most of fluorimetric methods, this method is quick and simple, has high sensitivity and good stability. The interaction mechanism is also studied.  相似文献   

12.
This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5 to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO) and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996. Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d 3 A/dλ3 (peak-to-peak signal between λ2 = 625 and λ1 = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d 3 A/dλ3) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in various synthetic and water samples. The text was submitted by the authors in English.  相似文献   

13.
A method was developed for sampling and selective quantitative determination of typical volatile organic compounds (VOCs) in ambient urban air. A mobile and self-contained dual-channel air sampling tool based on solid phase adsorption was constructed. A simple calibration procedure circumventing the adsorption/desorption process was designed. The method was validated for seven “key-analytes”: n-hexane, 3-methyl-2-pentene, benzene, tetrachloroethene, styrene, 1,2,4-trimethylbenzene and acetophenone. The complete air sampling equipment is easily accommodated in a business suitcase. The lower limits of the practical working ranges are between 0.1 μg m–3 (tetrachloroethene) and 1.2 μg m–3 (benzene). Air samples were collected at a location in Salzburg with heavy motor vehicle traffic and measured in order to prove a satisfactory method performance under practical monitoring conditions. Received: 4 January 1998 / Revised: 14 September 1998 / Accepted: 21 October  相似文献   

14.
Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn3O4, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10–3 mol dm–3 for the Mn(II) complex and 10–4 mol dm–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn2+, Co2+, Ni2+ and Cu2+ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn2+), 4.73–5.17 μB (for Co2+), 3.26–3.35 μB (for Ni2+) and 0.27–1.42 μB (for Cu2+). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.  相似文献   

15.
Long-lived rhodium radionuclides were produced by the following reactions:103Rh(n, 2n)102(m)Rh;103Rh(γ,xn)100Rh,101Rh,102(m)Rh;104Pd(d, α)102(m)Rh; Ru(d, n)99Rh,101(m)Rh,102(m)Rh; and . The average cross-section of the103Rh(n, 2n)102Rh reaction in a fission neutron spectrum is about 0.75 mb. Irradiation of rhodium in the bremsstrahlung spectrum of 50 MeV electrons yielded a102Rh activity of 0.11 μCi/g after 3 days at a power of 2 kW. The thick target yield of the reaction104Pd(d, α)102Rh was 0.002 μCi/μAh for 12 MeV deuterons. The thick target yield of the reaction Ru(d,xn)102Rh was 0.05 μCi/μAh for 12 MeV deuterons and 4.8 μCi/μAh for 18 MeV deuterons. The best yield was obtained by deuteron bombardment of ruthenium. The chemical separation of carrier-free Rh radionuclides from deuteron-irradiated ruthenium is described, with a chemical yield better than 90%. The same procedure has also been applied for the isolation of105Rh from neutron-irradiated ruthenium. γ-Ray spectra of99Rh,101(m)Rh and102(m)Rh from deuteron-irradiated ruthenium and of105Rh from neutron-irradiated ruthenium, taken with a Ge(Li) detector, are shown; a number of γ-rays, not reported in the literature, were observed. The γ-ray energies were determined with a precision of ca. 0.3–0.4 keV.  相似文献   

16.
Liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissue samples. Prior to instrumental analysis, samples were subjected to acid extraction followed by solid-phase cleanup using Strata-X cartridges. Mass spectral acquisitions were performed under selective multiple reaction monitoring (MRM) mode at m/z 199 and 670 from triply charged precursors of bacitracin A (m/z 475); m/z 385 and 379 from triply charged precursors of colistin A (m/z 391); and m/z 380 and 374 from triply charged precursors of colistin B (m/z 386). Method precision was evaluated from spike recovery of samples fortified at concentrations corresponding to 2/5 of the maximum residue limits (MRLs) for each of the analytes under study. Intra-day and inter-day variations were found to range from 90.9 to 104% with relative standard deviation (RSD) <6.5%, and from 90.1 to 106% with RSD <9.1%, respectively. Limits of quantification (LOQs) were defined as the spiking concentrations at 2/5 MRL, and limits of detection (LODs) were 10–47 μg kg−1 for bacitracin A, 1–16 μg kg−1 for colistin A, and 6–14 μg kg−1 for colistin B in milk and animal tissues. The presented method has good precision and high sensitivity and was applied as a fast screening protocol and a quantitative tool for monitoring of the concerned polypeptides in foods as part of a surveillance program.   相似文献   

17.
Summary This paper describes an HPLC method for the determination of cefuroxime in human plasma. The method uses solid phase extraction (SPE) and has acceptable sensitivity, precision and accuracy. The limit of quantification in plasma samples is 0.1 μg mL−1. Calibration curves were linear within 0.1–20 μg mL−1, with mean correlation coefficient of 0.9982. Mean inter day precision and accuracy were 7.8% and 6.4%, respectively. The method was applied to determine cefuroxime levels in patients receiving cefuroxime, 3 time per day.  相似文献   

18.
The possibility of a simultaneous determination of low and medium Z elements in hair in a single ion beam exposure was studied. Different ion beams, proton, deuteron,3He and18O, at velocities ranging from 2.7–6.9 MeV/amu were investigated. In this work,18 8O4+ beam was found to give the best experimental condition in terms of sensitivity and number of elements detected. The detection limits in a single hair ranged from 2.9·10−5 μg for Fe to 0.72 μg for H using this beam.  相似文献   

19.
In soil science (ca. 1970), bromide ion (Br) in various forms (e.g., KBr, NaBr, SrBr2) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water without substantial chemical or physical interactions with the soil. Typically, Br is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method, which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum (i.e. ≈20), the principal interfering soil constituent, calculated for the79Br(n,γ)80Br reaction compared to27Al(n, γ)28Al. Br was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φepi=2.5·1012 n·cm-2·s-1) using a BN capsule.  相似文献   

20.
Various ion beam techniques (E≥1 MeV/amu) are compared from the standpoint of their analytical capabilities: Charged Particle Activation Analysis (CPAA), Particle Induced X-Ray Emission (PIXE), Ion Induced γ-Ray Emission for bulk analysis, Prompt Reaction Analysis (PRA), Rutherford Backscattering Spectrometry for surface layer characterization and ion absorptiometry for microscopic analysis. With CPAA and PIXE≥70 elements can be detected with sub-ppm sensitivity. The scope of CPAA is being extended with heavy ion beams for radioactivation of H, He, Li, Be, B, C isotopes. In surface layer characterization recent developments in PRA and RBS also involve heavy ion beams. In RBS they can significantly enhance mass resolution for M>50 in comparison with α scattering. For example,63Cu and65Cu can be quantitatively identified in surface films using a 1 MeV/amu40Ar beam. In microscopic analysis, the nuclear microprobe can provide atom-specific signals from quantities ≥10−12 g on spots of a diameter ≥2 μm. Ion absorptiometry techniques can sense density variations as low as ±0.5% in 1 μm3 or less of sample volume.  相似文献   

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