共查询到20条相似文献,搜索用时 31 毫秒
1.
Karsten Haas J. Feldmann Rainer Wennrich Hans-Joachim Stärk 《Analytical and bioanalytical chemistry》2001,370(5):587-596
The analytical performance of an axial inductively-coupled-plasma time-of-flight mass spectrometer (ICP–TOFMS) as a detector
for fast transient chromatographic signals resulting from the coupling to capillary gas chromatography (CGC) was investigated.
A cryotrapping GC–ICP–TOFMS method for the determination of volatile metal(loid) compounds (VOMs) in gases was used and the
suitability of the TOF mass analyzer for multi-elemental speciation analysis and multi-isotope ratio determinations was studied
in terms of accuracy and precision. Isotope ratios 118Sn/120Sn and 121Sb/123Sb have been determined in in-house gas standard atmospheres in Tedlar bags at two different levels (100 pg and 1 ng) for
different elemental species (SnH4, MeSnH3, Me2SnH2, Me3SnH, BuSnH3, SbH3, and MeSbH2). A limitation arising from counting statistics in both detection modes could be shown. A solution containing rhodium (10
ng mL–1) and cadmium (40 ng mL–1) was introduced simultaneously to the GC outlet. Rhodium acts as a continuous internal standard and Cd is used for mass-bias
correction (by measuring the 111Cd/113Cd ratio). The detection system in both pulse counting and analog mode was examined. The best attainable precision was established
for Me2SnH2 (analog mode, 12 replicates, 1 ng, RSD 0.34%, accuracy 0.31%) whereas most other species ranged between 0.4 and 0.5% RSD
if higher concentrations were used. The limitations of the pulse counting system are clearly seen, with peak heights of more
than 2000 counts reaching saturation (for an integration time of 100 ms), which reduces the accuracy of isotope ratio determinations.
A dozen VOM could be detected in an aged landfill gas sample; several unidentified Sn compounds were present. Although their
isotope ratios are within the confidence value of the standards, it is not yet clear if the acquired precision is good enough
to identify isotopic fractionation of metal(loid)s through biovolatilization processes. With the precision achieved, the combination
of cryotrapping GC and ICP–TOFMS is a powerful tool for monitoring volatile multi-element species in multi-tracer experiments
and isotope dilution methodology.
Received: 23 November 2000 / Revised: 19 February 2001 / Accepted: 24 February 2001 相似文献
2.
A laboratory-built flow injection analyzer is reported for monitoring the drinking water disinfectants silver (I) ion and iodine in water produced from NASA's water recovery system. This analyzer uses spectrophotometric detection with a custom made 10 cm optical flow cell. Optimization and interference studies are discussed for the silver (I) ion configuration. Subsequent results using the silver (I) configuration with minor modifications and alternative reagents gave promising results for iodine determinations as well. The estimated MDL values for Ag+ and I2 are 52 μg L−1 Ag+ and 2 μg L−1 I2; the mean percent recoveries were 104% and 96.2% for Ag+ and I2 respectfully; and percent relative standard deviations were estimated at 1.4% for Ag+ and 5.7% for I2. The agreement of this potentially multifunctional analyzer to reference methods for each respective water disinfectant is measured using Bland–Altman analysis as well as more traditional estimates. 相似文献
3.
Ana Cristi B Dias 《Analytica chimica acta》2004,514(2):253-257
A sequential injection system with spectrophotometric detection was proposed for the determination of copper, zinc and lead in brass. In view of the high analyte concentrations and the sensitivity of the involved catalytic methods, optimization of the flow system was carried out aiming mild reaction conditions. Copper and lead determinations were based on the catalytic effects of Cu2+ and Pb2+ on the oxidation rates of resorcinol and pyrogallol red by H2O2, respectively, and zinc determination involved precipitate formation after oxidation of 1-nafthylethylenediamine by K3Fe(CN)6. The analytical procedures were designed with some common parameters such as pH=9.0 (borate system), λ=530 nm, and H2O2 as oxidizing agent; system geometry was maintained.The proposed system is rugged, and base line drift is not observed during 4 h operation periods. Twenty samples are run per hour (60 determinations) and reagent consumption is minimal, thus avoiding drawbacks related to waste management. Precise results (R.S.D.<1.0%; n=7) are obtained and a detection limit of 1% (w/w) was estimated for the three analytes. Results were in agreement with flame atomic absorption spectrometry. 相似文献
4.
A highly automated, chemically inert, stopped-flow mixing system for rapid kinetic determinations is described. The reactant solutions are drawn into the drive syringes through novel double check valves, which are an integral part of the syringe block. The prime movers for the flow systems are pneumatic cylinders driven by compressed air; air flow is controlled by electromechanical valves actuated by optically isolated zero-crossing switches. The dead time of the flow system is 2–3 ms, depending on the drive pressure.The spectrophotometric detection system consists fo a high-intensity light source, a wavelength selector and a reference detector that are mechanically isolated from the flow system by a quartz fiber-optic light guide. The transducers are solid-state photodiodes. The sample photodiode is mounted adjacent to the output window of the cell to minimize light losses. The signal-to-noise ratio of the photometric system is from 2×102 to greater than 4×4, depending on wavelength, absorbance level, and amount of signal averaging.The reduction of Fe(CN)63? by ascorbic acid was used as a test reaction. Accuracy and precision better than 0.3% were obtained for routine determination. A detection limit of 4.10×10?7 M Fe(CN)63?, or 134 μg kg?1 K3Fe(CN)6, was found for this system. 相似文献
5.
A detection system for hydrogen peroxide, i.e., luminol chemiluminescence (CL) in a hexadecyltrimethylammonium bromide (CTAB) reversed micellar system, was coupled to enzyme reactions. The use of CTAB reversed micellar medium allows one to conduct both the oxidase enzymatic and CL detection reactions simultaneously at mild pH (l-amino acid system, pH 8.7; glucose system, pH 8.5) in the absence of any co-oxidant or catalyst. Based on this result, simple and unique determinations of l-amino acids and glucose as substrates were developed. The calibration graph for a representative amino acid, l-phenylalanine, was linear in the concentration range 4.0×10?6?200×10?6M with a relative standard deviation of 5.78% (five determinations). The method established for l-phenylalanine was also applicable for the assay of fourteen other l-amino acids. The calibration graph for glucose was linear in the concentration range 5.4×10??540×10?6M with a relative standard deviation of 4.27% (eight determinations). This method was compared with a standard spectrophotometric method (hexokinase) and successfully applied to the determination of glucose in human serum. 相似文献
6.
Instrumentation is described for the direct determination of Cl, Br, I and S in dissolved samples. A tantalum furnace is coupled directly to a TM010 cavity, in which a helium microwave plasma is generated at atmospheric pressure. Samples (20 μl) are dried, ashed and atomized; the free atoms are transported by helium to the cavity, where they are excited. Detection limits are in the sub-mg l-1 region. The effect of counter cations is removed by the addition of 50 mg l-1 potassium hydroxide, which also helps to suppress interferences by large amounts of matrix constituents, but the standard addition technique remains necessary to permit determinations that are reliable to within 5%. 相似文献
7.
The interference standard method (IFS) is evaluated to improve the accuracy of the determination of S, Mn and Fe in meat and grain samples by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Due to ICP-QMS relatively low resolution, polyatomic interferences caused by 16O2+, (16OH)2+, 40Ar14NH+, and 40Ar16O+, for example, can compromise determinations at m/z 32, 34, 55, and 56, respectively. In IFS, differently from traditional internal standard methods, plasma naturally occurring species are used to correct for variations in the interference signal rather than the analyte signal. The method is based on the hypothesis that the interfering ion and the IFS probe present similar behaviors in the plasma, and that by using the analytical (analyte plus interference)/IFS signal ratio one could reduce variations due to interference and, consequently, improve accuracy. In this work, this strategy is evaluated in real sample applications and significant improvements on accuracy are observed for 32S, 34S, 55Mn, and 56Fe determinations. Recoveries ranging from 72% for Mn to 105% for Fe in two different standard reference materials are obtained using the 38Ar probe. These analytes are successfully determined in meat and grain samples with concentrations ranging from 4.42 μg g−1 for Mn in corn to 7270 μg g−1 for S in chicken liver. The method is compared with other strategies such as internal standardization and mathematical correction. No instrumental modification or introduction of foreign gases is required, which is especially attractive for routine applications. 相似文献
8.
《Analytical letters》2012,45(7):463-472
Abstract Sodium, potassium and ammonium ions, in concentration ranges of natural and waste water samples, have been simultaneously determined by direct potentiometry, using sodium, potassium, and ammonia ion-sensitive electrodes. The results are printed out as concentration units directly from an automated continuous -flow system with on-line minicomputer and printer. The optimum sampling rate is 20 samples or 60 determinations per hour. Various water samples have been analyzed and the results compared to those obtained by the standard methods. The lower detection limits were 0.1 ppm for Na+ and NH4 + and 1.0 ppm for K+. The values of standard deviation were < 10%, with the exception of the lowest concentrations. The relative error was in the range of ± 2%. The correlation of standard and proposed methods was very good. 相似文献
9.
Wang ZA Liu X Byrne RH Wanninkhof R Bernstein RE Kaltenbacher EA Patten J 《Analytica chimica acta》2007,596(1):23-36
An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength of ∼15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed within the bore-hole of a PEEK rod. This Teflon AF tubing is filled with a standard indicator solution with a fixed total alkalinity, and forms a liquid core waveguide (LCW). The LCW functions as both a long pathlength (∼15 cm) optical cell and a membrane that equilibrates the internal standard solution with external seawater. fCO2 is then determined by measuring the pH of the internal solution. DIC is measured by determining the pH of standard internal solutions in equilibrium with seawater that has been acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ∼7 samples (21 measurements) per hour. The system was used for underway measurements of sea surface pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean in 2005. The field precisions were evaluated to be 0.0008 units for pH, 0.9 μatm for fCO2, and 2.4 μmol kg−1 for DIC. These field precisions are close to those obtained in the laboratory. Direct comparison of our measurements and measurements obtained using established standard methods revealed that the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 μatm for fCO2, and 2.2 ± 6.0 μmol kg−1 for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of both seawater and freshwater. 相似文献
10.
《Spectrochimica Acta Part B: Atomic Spectroscopy》1998,53(5):699-708
The direct and simultaneous determinations of Cu and Mn in seawater using a multielement graphite furnace atomic absorption spectrometer (Perkin-Elmer SIMAA6000) are described. Three kinds of chemical modifier (Mg(NO3)2, Pd(NO3)2 and a mixture of these) were tested. The matrix interferences were removed completely so that a simple calibration curve method could be used to determine Cu and Mn in seawater from the open ocean using Pd or a mixture of Pd and Mg as the chemical modifier. The relative standard deviations (RSDs) for the simultaneous determination of Cu and Mn in seawater from open ocean are 10% or less, and the detection limits were 0.07 μg 1−1 for Cu and 0.10 μg 1−1 for Mn, using Pd as the chemical modifier. The accuracy of the method is confirmed by analysis of four kinds of certified reference saline waters. 相似文献
11.
儿茶酚胺是一类非常重要的神经递质,在人体的心血管系统、神经系统、内分泌腺、肾脏、平滑肌等组织系统的生理活动中起着广泛的调节作用。肾上腺素为儿茶酚胺的一种,建立灵敏、高效的肾上腺素检测技术具有重要的临床意义。本文将银(Ⅲ)配合物与鲁米诺组成新的流动注射化学发光体系,利用碱性介质中肾上腺素对三价银配合物-鲁米诺化学发光体系有明显的增强效应来测定肾上腺素的含量,并据此建立了高效测定肾上腺素的流动注射化学发光新方法。在优化的条件下,该方法测定肾上腺素的线型范围为1.0×10-9~1.0×10-7 mol L-1,检出限为8.0×10-10 mol L-1,对1.5×10-8 mol L-1肾上腺素11次平行测定,其相对标偏差为2.9%。利用建立的分析方法测定了药物肾上腺素,并对三价银-鲁米诺化学发光新体系测定肾上腺素的反应机理进行了讨论。 相似文献
12.
The application of the therinometric method to the catalytic endpoint indication in volumetric determinations by precipitation reactions is discussed. The direct titration of silver, mercury(II) and palladium(II) as well as the determination of several anions (Cl?, Br?, J?, SCN?, CN?, [Fe(CN)6]4? and S2?) by backtitration with iodide standard solution is described. The well known reaction between cerium(IV) and arsenic(III), catalysed by iodide, serves as an indicator. The ions mentioned can thus be determined in the microgram range with good accuracy. 相似文献
13.
Karine L. Marques S. Sofia M. Rodrigues João L.M. Santos José L.F.C. Lima 《International journal of environmental analytical chemistry》2013,93(13):1256-1266
In this work a simple, fast and fully automated analytical methodology for the spectrophotometric determination of phenylglyoxylic acid is proposed. Phenylglyoxylic acid is a metabolite of styrene that is excreted in urine, being used as an indicator of styrene occupational exposure. The developed procedure was based on the phenylglyoxylic acid ability to inhibit the formation of the peroxovanadium cation produced by the reaction between vanadate and H2O2. The analytical process was implemented in a multi-pumping flow system that employs multiple solenoid actuated micro-pumps as the only active components. This enabled the reproducible insertion and efficient mixing of low volumes of sample and reagents as well as the transportation of the sample zone towards detection. Thus an easily controlled, low cost, compact and reliable analytical system was implemented. A linear working range for phenylglyoxylic acid concentrations up to 700?mg?L?1 (r 2?=?0.995, n?=?7), was obtained, with a detection limit of 37?mg?L?1. The system handles about 43 determinations per hour yielding precise results (relative standard deviation?<?5%, n?=?10). The developed methodology was applied to the determination of phenylglyoxylic acid in urine samples and the obtained results were in agreement with those furnished by the comparison method with relative percentage deviations lower than 6.6%. 相似文献
14.
A continuous flow “stat” method is described in which a certain arbitrarily imposed state in the flowing stream is automatically maintained by regulating the rate of flow of one of the components. The electronic system is regulated by measuring a physical phenomenon in the flowing solution. The method is illustrated by the examples of a continuous flow absorptiostat [Fe(III)/S2O32-/Cu(II)]for determinations of copper(II) (1–10 μg ml-1), iron(III) (25–250 or 12.5–125 μg ml-1), as well as for determination of iodide (12.8–128 μg ml-1). A continuous flow conductostat [HCl/NaOH] for determination of 1–2.5 × 10-4 M HCl is also described. This analytical technique is intended for automatic continuous monitoring of sample streams. 相似文献
15.
A new metallic atomization cell is used for trace metal determinations by tungsten coil atomic absorption spectrometry and tungsten coil atomic emission spectrometry. Different protecting gas mixtures are evaluated to improve atomic emission signals. Ar, N2, CO2 and He are used as solvents, and H2 and C2H2 as solutes. A H2/Ar mixture provided the best results. Parameters such as protecting gas flow rate and atomization current are also optimized. The optimal conditions are used to determine the figures of merit for both methods and the results are compared with values found in the literature. The new cell provides a better control of the radiation reaching the detector and a small, more isothermal environment around the atomizer. A more concentrated atomic cloud and a smaller background signal result in lower limits of detection using both methods. Cu (324.7 nm), Cd (228.8 nm) and Sn (286.3 nm) determined by tungsten coil atomic absorption spectrometry presented limits of detection as low as 0.6, 0.1, and 2.2 μg L−1, respectively. For Cr (425.4 nm), Eu (459.4 nm) and Sr (460.7 nm) determined by tungsten coil atomic emission spectrometry, limits of detection of 4.5, 2.5, and 0.1 μg L−1 were calculated. The method is used to determine Cu, Cd, Cr and Sr in a water standard reference material. Results for Cu, Cd and Cr presented no significant difference from reported values in a 95% confidence level. For Sr, a 113% recovery was obtained. 相似文献
16.
《Electrochemistry communications》1999,1(5):194-196
A rapid and sensitive method is developed for the determination of coenzyme Q10 (CoQ10) on the basis of the measurement of the radical intermediate (ubisemiquinone) formed during the reduction reaction of CoQ10 at a silver electrode by in situ EPR spectroelectrochemical techniques. At the potential of −0.55 V (versus SCE), the ubisemiquinone is formed and is stable in ethanol+water. Under optimal conditions, it was found that the proposed method provided a linear response over the CoQ10 concentration range 5–100 μmol l−1 with a detection limit of 3 μmol l−1. The relative standard deviation of the results was 7.5% for six successive determinations at 10 μmol l−1 CoQ10. This method is a useful tool for improving the selectivity when other chemicals present in the sample do not interfere in the assay. 相似文献
17.
A sensitive extractive spectrophotometric method for the determination of nitrogen dioxide in air and nitrite and nitrate in water, soil and blood serum is described. Nitrogen dioxide in air is fixed as nitrite in a suitable trapping solution. The method is based on the diazo coupling reaction betweenp-nitroaniline andN-(1-naphthyl)ethylenediamme dihydrochloride [NEDA]. The azo dye formed under aqueous conditions is extracted with isobutyl methyl ketone [IBMK]. The system obeys Beer's law over the range 0–3 g of nitrite at 545 nm and the colour is stable for 3h. The molar absorptivity of the colour system is 5.7 × 104 L mol–1 cm–1. The relative standard deviation is 1.3% for ten determinations at 2 ug of nitrite. Nitrate is determined as nitrite after reduction on a cadmium column. Negative interferences from SO2, H2S, Cu2+ and Cr3+ and positive interference from Fe2+ and Fe3+ can be simply masked. 相似文献
18.
A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased. 相似文献
19.
ThecombinationofstrippingvoltammetrywithUPDcanleadtotheimprovementofsensitivity ,selectivi tyandreversibilityforelectroanalyticalpurposeandavoidtheuseoftoxicmercuryastheworkelectrode1andthenanalyticalapplicationshavebeendescribed .2 4 Inthiswork ,wedevelo… 相似文献
20.
《Analytical letters》2012,45(5):947-956
Abstract A new electrochemical substrate for horseradish peroxidase, methyl red, is reported. In this reaction system, horseradish peroxidase can catalyze the redox reaction of methyl red and H2O2. Methyl red exhibits a sensitive voltammetric peak at?0.51 V vs. Ag/AgCl reference electrode, the decrease of the peak current of methyl red is in proportion to the concentration of horseradish peroxidase (HRP). The linear range for determination of horseradish peroxidase is 5.0×10?8~5.0×10?7 g mL?1 and the detection limit is 1.8×10?8 g mL?1. The relative standard deviation is 3.3% when 2.0×10?7 g mL?1 HRP was sequentially determined 11 times. A voltammetric enzyme‐linked immunoassay method for the determination of estriol was developed, based on this electrochemical system. The linear range for determination of estriol is 1.0~1000.0 ng mL?1, and the detection limit is 0.33 ng mL?1. The relative standard deviation for 11 parallel determinations with 200 ng mL?1 estriol is 4.8%. Some pregnancy serum samples were analyzed with satisfactory results. 相似文献