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21.
本文研究了Mn~(2+)和Co~(2+)对7-(8-羟基-3,6-二磺基萘偶氮)-8-羟基喹啉-5-磺酸-硼砂反应体系的混合荧光增敏作用。实验条件下,荧光增敏强度满足线性加和关系的范围是:Mn~(2+)浓度0~2.9×10~(-7)mol/L;Co~(2+)浓度0~8.8×10~(-7)mol/L;总浓度不超过1.0×10~(-6)mol/L。检出限量为Mn~(2+)4.5×10~(-9)mol/L和Co~(2+)1.4×10~(-8)mol/L。实现了Mn~(2+)和Co~(2+)的连续测定。 相似文献
22.
This paper describes the screening for metabolites of butoprozine, a new anti-anginal drug, in dog bile by means of reverse-phase HPLC. Although it does involve a simple clean-up step to remove a substantial amount of endogenous bile compounds, this screening method nevertheless avoids extraction of metabolites and thus allows all metabolites to be introduced into the chromatographic system. A single run of 100 minutes from 100% water to 100% methanol in a linear gradient effects adequate separation of the great majority of metabolites without interference from remaining endogenous compounds. Two methods of differentiating between metabolite peaks and endogenous peaks have been worked out. The first one makes use of 14C-labeled butoprozine by measuring the amount of radioactivity in the column effluent while simultaneously recording the UV absorbance. The second method compares continuous gradient chromatograms of bile recorded before and after butoprozine administration under very similar conditions. The latter method can be applied to both radioactive and non-radioactive materials. 相似文献
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24.
Rafael Lucena 《Analytica chimica acta》2004,509(1):47-54
A multipurpose chamber capable of implementing a variety of continuous separation techniques is reported. The proposed module can be used in conjunction with flow manifolds coupled on-line to optical detectors in order to develop simple autoanalyzers for full sample pretreatment. The analytical applicability of such a device is discussed with specific regard to gas diffusion, dialysis, solid-phase extraction (SPE), and precipitation/dissolution techniques. Its versatility and simplicity are among the main advantages. Four different automated analyzers based on the use of the multipurpose chamber have been developed for monitoring of different quality control parameters of liquid food samples, namely, carbon dioxide in beer, ascorbic acid in fruit juice, caffeine in soft drinks and lactose, fat and protein in milk. The results obtained were compared with those provided by the existing alternatives for the same applications in terms of sensitivity and precision. 相似文献
25.
《Electroanalysis》2005,17(8):668-673
A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days. 相似文献
26.
G. Sivalingam R. Karthik Giridhar Madras 《Journal of Analytical and Applied Pyrolysis》2003,70(2):631-647
The thermal degradation/modification dynamics of poly(-caprolactone) (PCL) was investigated in a thermogravimetric analyzer under non-isothermal and isothermal conditions. The time evolution of the molecular weight distribution during degradation was studied using gel permeation chromatography. Experimental molecular weight evolution and weight loss profile were modeled using continuous distribution kinetics. The degradation exhibited distinctly different behavior under non-isothermal and isothermal heating. Under non-isothermal heating, the mass of the polymer remained constant at initial stages with rapid degradation at longer times. The Friedman and Chang methods of analysis showed a 3-fold change (from 18 to 55–62 kcal mol−1) in the activation energy from low temperatures to high temperatures during degradation. This suggested the governing mechanism changes during degradation and was explained using two parallel mechanisms (random chain scission and specific chain end scission) without invoking the sequential reaction mechanisms. Under isothermal heating, the polymer degraded by pure unzipping of specific products from the chain end. 相似文献
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An on-line coupled continuous flow liquid membrane extraction (CFLME) and C18 precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l−1 NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C18 precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C18 analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l−1 (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C18 based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples. 相似文献
29.
Manganese is extracted on-line from solid seafood samples by a simple continuous ultrasound-assisted extraction system (CUES). This system is connected to an on-line manifold, which permits the flow-injection flame atomic absorption spectrometric determination of manganese. Optimisation of the continuous leaching procedure is performed by an experimental design. The proposed method allows the determination of manganese with a relative standard deviation of 0.9% for a sample containing 23.4 μg g−1 manganese (dry mass). The detection limit is 0.4 μg g−1 (dry mass) for 30 mg of sample and the sample throughput is ca. 60 samples per hour. Accurate results are obtained by measuring TORT-1 certified reference material. The procedure is finally applied to mussel, tuna, sardine and clams samples. 相似文献
30.
Barry Simon 《Journal of statistical physics》1981,26(2):307-311
For a one-dimensional array ofS
N–1 spins (N 2) with isotropic pair interactions (and more general systems) with J(j–i) obeying supn[n–1
1
n
j
2|J(j)|]<, we prove that every equilibrium state is invariant under the natural action ofSO(N). In particular, there is no long-range order of the conventional type. Included is the caseJ(n)=n
–2.Research partially supported by U.S.N.S.F. Grant No. MCS-78-01885.S. Fairchild Scholar at Caltech. On leave from Departments of Mathematics and Physics, Princeton University, Princeton, New Jersey 08544. 相似文献