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51.
52.
J. Sarah Caygill Stuart D. Collyer Joanne L. Holmes Frank Davis Séamus P. J. Higson 《Electroanalysis》2013,25(11):2445-2452
We describe the use of cobalt phthalocyanine as a mediator to improve the sensitivity for the electrochemical detection of TNT. Commercial screen‐printed electrodes containing cobalt phthalocyanine were employed for determination of TNT. Improved sensitivities compared to screen‐printed carbon electrodes without phthalocyanine were observed, current response for cyclic voltammetric measurements at modified electrodes being at least double that of unmodified electrodes. A synergistic effect between oxygen and TNT reduction was also observed. Correlation between TNT concentrations and sensor output was observed between 0–200 µM TNT. Initial proof‐of‐concept experiments combining electrochemical determinations, with the use of an air‐sampling cyclone, are also reported. 相似文献
53.
Determination of Pd,Rh, Pt,Au in road dust by electrothermal vaporization inductively coupled plasma mass spectrometry with slurry sampling 总被引:1,自引:0,他引:1
Inductively coupled plasma mass spectrometry coupled with ultrasonic slurry sampling electrothermal vaporization (USS-ETV-ICP-MS) has been applied to determine Pd, Rh, Pt and Au in 0.5% m/v slurries of several road dust samples. 2% m/v ammonium pyrrolidine dithiocarbamate (APDC) was used as the modifier to enhance the ion count. The influence of instrument operating conditions, slurry preparation and interferences on the ion count was reported. This method has been applied to the determination of Pd, Rh, Pt and Au in BCR 723 Road Dust and NIST SRM 2709 San Joaquin Soil reference materials and two road dust samples collected locally. The analysis results of the standard reference materials agreed with the certified values. Precision between sample replicates was better than 10% for all the determinations. The method detection limits estimated from standard addition curves were 0.9, 0.4, 0.6 and 0.4 ng g−1 for Pd, Rh, Pt and Au, respectively, in original dust samples. 相似文献
54.
The development of novel microanalytical techniques forin situ chemical characterization of the terrestrial subsurface environment has grown significantly over the last decade, particularly those instruments that are interfaced to the cone penetrometer. Cone penetrometer testing (CPT) has emerged as an effective means to introduce samplers and probes forin situ analysis of contaminants in soil and groundwater matrices. A variety ofin situ chemical samplers for CPT have been developed that can be driven into the subsurface to collect soil gas, groundwater, or soil samples at depth, thus providing a means of determining the vertical and horizontal extent of contamination. Cone penetrometer testing is also being explored as a means to deliverin situ subsurface sensor probes, including probes based on laser-induced fluorescence, Raman, and infrared spectroscopies for organics; on laser-induced breakdown and X-ray fluorescence spectroscopies for heavy metals; and on passive gamma-ray spectroscopy for radionuclides. The range of analytical technologies used in CPT for the determination of organic and inorganic species in the subsurface is described. 相似文献
55.
A slurry sampling method has been developed for the determination of Pb in marine plankton by ETAAS using a freshwater plankton certified reference material (CRM 414). Slurries were prepared in 1–3% m/v range with 1% v/v HNO3 by ultrasonic agitation for 5 min. The effects of several chemical modifiers, including Ir(NO3)2, Mg(NO3)2, Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, and Mg(NO3)2 + NH4H2PO4, were investigated for the stabilization of Pb during thermal pretreatment. Lead in slurries was effectively stabilized up to 1000 °C with Ir, Pd and Pd + Mg modifiers among which Pd + Mg provided the best results with complete atomization at 1850 °C. Firings in the presence of Ir were, problematic due to ash formation inside the atomizer. Water, dilute HNO3 and HF were examined as suspension medium. Dilute HNO3 (1–2% v/v) proved to be advantageous over water as it afforded extraction of Pb from plankton almost quantitatively in 5 min agitation. Hydrofluoric acid was the least suitable medium. Increasing HF concentration up to 5% v/v resulted in inaccuracy and substantial background absorption. Fast-heating furnace method provided comparable accuracy and precision to that of conventional-heating in slurries of CRM 414. Detection limits and characteristic masses were, respectively, 0.49 μg L− 1 and 32 pg for the conventional method and 0.62 μg L− 1 and 37 pg for the fast-heating method. However, fast-heating approach suffered from distorted peaks at high temperatures and incomplete pyrolysis of matrix at lower temperatures. Analysis of marine plankton samples for Pb was performed by using the conventional furnace program. The results showed a high correlation with those obtained by solution ICP-MS. Differences were statistically insignificant within 95% confidence interval. 相似文献
56.
Zeisler R 《Analytical and bioanalytical chemistry》2004,378(5):1277-1283
NIST maintains a portfolio of more than 1300 standard reference materials (SRM), more than a third of these relating to measurements in the biological and environmental fields. As part of the continuous renewal and replacement efforts, a set of new marine sediments has been recently developed covering organic and inorganic determinations. This paper describes the steps taken in sample preparation, homogeneity assay, and analytical characterization and certification with specific emphasis on SRM 2702 inorganics in marine sediment. Neutron activation analysis showed the SRM to be highly homogeneous, opening the possibility for use with solid sampling techniques. The certificate provides certified mass fraction values for 25 elements, reference values for eight elements, and information values for 11 elements, covering most of the priority pollutants with small uncertainties of only several percent relative. The values were obtained by combining results from different laboratories and techniques using a Bayesian statistical model. An intercomparison carried out in field laboratories with the material before certification illustrates a high commutability of this SRM.Electronic Supplementary Material Supplementary material is available in the online version of this article at 相似文献
57.
Here we describe a reversibly sealed microchip device that incorporates poly(dimethylsiloxane) (PDMS)-based valves for the rapid injection of analytes from a continuously flowing stream into a channel network for analysis with microchip electrophoresis. The microchip was reversibly sealed to a PDMS-coated glass substrate and microbore tubing was used for the introduction of gas and fluids to the microchip device. Two pneumatic valves were incorporated into the design and actuated on the order of hundreds of milliseconds, allowing analyte from a continuously flowing sampling stream to be injected into an electrophoresis separation channel. The device was characterized in terms of the valve actuation time and pushback voltage. It was also found that the addition of sodium dodecyl sulfate (SDS) to the buffer system greatly increased the reproducibility of the injection scheme and enabled the analysis of amino acids derivatized with naphthalene-2,3-dicarboxaldehyde/cyanide. Results from continuous injections of a 0.39 nL fluorescein plug into the optimized system showed that the injection process was reproducible (RSD of 0.7%, n = 10). Studies also showed that the device was capable of monitoring off-chip changes in concentration with a device lag time of 90 s. Finally, the ability of the device to rapidly monitor on-chip concentration changes was demonstrated by continually sampling from an analyte plug that was derivatized upstream from the electrophoresis/continuous flow interface. A reversibly sealed device of this type will be useful for the continuous monitoring and analysis of processes that occur either off-chip (such as microdialysis sampling) or on-chip from other integrated functions. 相似文献
58.
Detection of ethanol in human body fluids by headspace solid-phase micro extraction (SPME)/capillary gas chromatography 总被引:1,自引:0,他引:1
Summary Ethanol has been found extractable from human whole blood and urine samples by headspace solid-phase micro extraction (SPME) with a Carbowax/divinylbenzene-coated fiber. After heating a vial containing the body fluid sample with ethanol, and isobutanol as internal standard (IS) at 70°C in the presence of (NH4)2SO4, a Carbowax/divinylbenzene-coated SPME fiber was exposed in the headspace of the vial to allow adsorption of the compounds. The fiber needle was then injected into a middle-bore capillary gas chromatography (GC) port. The headspace SPME-GC gave intense peaks for both compounds; a small amount of background noises appeared, but did not interfere with the detection of the compounds. Recoveries of ethanol and IS were 0.049 and 0.026% for whole blood, respectively, and 0.054 and 0.085% for urine, respectively. The calibration curves for ethanol showed excellent linearity in the range of 80–5000 mg L–1 for whole blood and 40–5000 mg L–1 for urine; the detection limits for both samples were 20 and 10 mg L–1, respectively. The data on actual determination of ethanol after the drinking of beer are also presented for two subjects. 相似文献
59.
Air monitoring is the quantitative-qualitative assessment of the extent of pollutants. It is performed to ensure compliance with legislation and to evaluate control measures and mitigation solutions. There are numerous approaches to measure airborne formaldehyde (FA), ranging from passive sampling techniques to remote sensing devices. Research of sampling procedures and analytical methods was performed in a scientific database and on the web to offer a scenario of the devices and techniques that can be used to assess FA exposure. Moreover, in the design of FA assessment, some crucial aspects were considered, such as standard atmosphere generation for devices calibration. This review summarizes the tools and basics used in FA air monitoring, useful to organize a functional monitoring strategy for assessment of FA concentration levels. An insight into the sampling and analysis of FA is provided. Recent advances in solid sorbent technology allow analysts to use these devices coupled to chromatographic instruments. A comparison of the strengths and weaknesses of analytical methods (gas-/liquid-chromatography coupled with mass spectrometry or UV detection, chromogenic, colorimetric, electrochemical determination) and sampling devices (impregnated papers, solid sorbents, liquid sorbents, bubblers, impingers, micro-impingers, denuder samplers, sealed bags, canisters) methods are illustrated. This survey found that a monitoring strategy should be planned considering the most appropriate methodology in terms of costs and practicability. Therefore, it is necessary to know the aspects that can make the chosen strategy suitable and valid for the exposure scenario under investigation. 相似文献
60.
Flavio Antonio Franchina Delphine Zanella Eliane Lazzari Pierre‐Hugues Stefanuto Jean‐Franois Focant 《Journal of separation science》2020,43(9-10):1790-1799
Headspace gas chromatography is frequently used for aroma profiling thanks to its ability to naturally exploit the volatility of aroma compounds, and also to provide chemical information on sample composition. Its main advantages rely on simplicity, no use of solvent, amenability to automation, and the cleanliness of the extract. In the present contribution, the most effective sampling (dynamic extraction), separation (multidimensional gas chromatography), and detection (mass spectrometry) techniques for untargeted analysis are exploited in combination, showing their potential in unraveling aroma profiles in fruit beers. To complete the overall analytical process, a neat workflow for data analysis is discussed and used for the successful characterization and identification of five different beer flavors (berries, cherry, banana, apple, and peach). From the technical viewpoint, the coupling of purge‐and‐trap, comprehensive two‐dimensional gas chromatography, and mass spectrometry makes the global methodology unique, and it is for the first time discussed. A (low‐)flow modulation approach allowed for the full transfer into the second dimension with mass‐spectrometry compatible flow (< 7 mL/min), avoiding the need of splitting before detection and making the overall method sensitive (1.2–5.2‐fold higher signal to noise ratio compared to unmodulated gas chromatography conditions) and selective. 相似文献