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211.
S. Korhammer Rolf Herzig Peter Schramel Jorma Kumpulainen Bernd Markert Herbert Muntau Philippe Quevauviller 《Accreditation and quality assurance》2000,5(6):238-242
Cabbage is frequently used in environmental monitoring and food control, and, hence, cabbage reference materials (RMs) are
required for ensuring quality assurance. A cabbage RM was prepared in view of certification of specific elements from the
"black list" of high toxicological interest and nutritive importance. All tasks of the RM production (production of the plant
material, cutting and freeze-drying, determination of the residual water content, preparation of the RM, homogeneity testing,
stability testing, certification measurements) are described in detail.
Received: 12 November 1999 / Accepted: 29 January 2000 相似文献
212.
A simple, sensitive and rapid derivative spectrophotometric method using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) has been developed for simultaneous determination of Co(II), Ni(II) and Fe(II) which have very similar chemical behavior and appear together in many real samples. The complexes of all these metal ions with 5-Br-PADAP were formed immediately at pH 7.0 ammonium acetate buffered solution and were stable for at least 24 h. Second derivative spectra were selected for evaluation, because working wavelength determination was more precise and spectral overlap was less than in the ordinary and first derivative spectra. Three wavelengths at which the complexes exhibit extremum 2D values for Co(II), Ni(II) and Fe(II) were selected as analytical wavelengths, i.e., 640, 600 and 740 nm, respectively. Calibration curves drawn with zero-to-peak values at mentioned wavelengths were linear between 80 and 2000 ng ml−1 for each metal ion. Concentrations of Co(II) and Ni(II) were calculated from the total 2D values and the sum of the linear equations for these three cations at 640 and 600 nm, after Fe(II) assay by making use of the 2D value at 740 nm. Limits of detection (LOD) for Co(II), Ni(II) and Fe(II) were 2.7, 13.9 and 3.0 ng ml−1, respectively. The method has been applied to tool steel and heater resistance wire samples successfully. 相似文献
213.
214.
This study presents a novel miniaturized Hadamard transform fluorescence imaging microscope, by combining a conventional fluorescence microscope with Hadamard transform multiplexing encoding using a one-dimensional movable mask to realize spatial resolution and a linear CCD for multichannel detection. The microscope can provide high-resolution automatically-generated 0–255 gray level HT images for morphological analysis and visualization of a single cell, and normalized HT images for cellular quantitative measurements. The microscopes imaging capability was applied to measure the DNA content in human lymphocyte, chicken erythrocyte and eel erythrocyte, and a comparative study was performed. The results show that the calibrated DNA content in a chicken erythrocyte is 2.32 pg when human lymphocyte is used as the standard, and eel erythrocyte may be a potentially reliable and novel standard for determining DNA contents in other species because it has a stable DNA value of 2.06 pg, with a CV of 4.3% when 20 eel erythrocytes are measured. The results also demonstrate that the HT imaging microscope should be valuable in the fields of medicine and cell biology. 相似文献
215.
A simple, rapid and sensitive high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of oxytetracycline, doxycycline, tetracycline and chlortetracycline was developed, and successfully applied to the analysis of commercial tetracycline antibiotics. The separation was performed on a reverse-phase C18 column with a gradient elution composed of methanol and sodium acetate buffer (containing disodium ethylenediaminetetraacetate and calcium chloride, pH 8.10) as the mobile phase, and fluorescence detection at 532 nm (excitation at 380 nm). The detection limits for oxytetracycline, doxycycline, tetracycline and chlortetracycline were 0.1, 0.5, 0.3 and 0.4 g L–1, respectively. Data with respect to precision and accuracy were reported and discussed. 相似文献
216.
Danuta Wrbel Andrzej Boguta 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):67-76
In this paper we describe conversion of light energy into electric energy in a photoelectrochemical cell containing zinc phthalocyanine (ZnPc) dyes. For all dyes investigated in liquid polyvinyl alcohol with dimethyl sulfoxide solution and located in the photoelectrochemical cell the following measurements have been done: absorption, fluorescence, photoacoustic spectra, photovoltaic spectra, kinetics of photocurrent and current–voltage characteristics. It has been shown that all dyes located in the photoelectrochemical cell are able to convert light into electric energy but with different effectiveness. The influence of substituted different peripheral groups to ZnPc core and the correlation between the molecular structure and effectiveness of solar to electric energy conversion were observed and described. The unique behavior of ZnPc substituted with fluorines was indicated. 相似文献
217.
Procion red HE-3B (RR120) is an example of dye currently used in affinity purification. A method is described for determining trace amounts of RR120 dye contaminant in human serum albumin by cathodic stripping voltammetry. The method is based on a measure of a well-defined peak at −0.58 V, obtained when samples of HSA protein (0.01-2% w/v) containing dye concentrations are submitted to a heating time of 330 min at 80 °C in NaOH, pH 12.0 and the samples are removed to a solution containing Britton-Robinson buffer, pH 4.0. Using an optimum accumulation potential and time of 0 V and 240 s, respectively, linear calibration curves were obtained from 1.0×10−9 to 1.0×10−8 mol l−1 for RR120 dye. Leakage/hydrolysis of reactive red 120 from an agarose support (e.g. at pH 2 or 12) can also be conveniently determined at very low levels (sub-μg ml−1) by means of cathodic stripping voltammetry, which involves adsorptive accumulation of the dye onto the hanging mercury-drop electrode. 相似文献
218.
Makedonka D. GulcevGillian L.G. Goring Michael RakicJohn D. Brennan 《Analytica chimica acta》2002,457(1):47-59
We report on the development of reagentless fluorescence-based sensing films utilizing hydrolytic enzymes co-entrapped with polymers that are labelled with pH sensitive fluorophores. Aqueous solutions of a hydrophilic enzyme (urease) or a lipophilic enzyme (lipase) containing fluorescein or carboxy-seminaphtharhodafluor-1 (SNARF-1), either free or conjugated to a dextran polymer backbone, were mixed with hydrolyzed alkoxysilane solutions and cast onto planar surfaces to form thin, biologically active sol-gel derived films (ca. 500 nm thick). The films also contained various additives, such as methyltrimethoxysilane, dimethyldimethoxysilane, polyethylene glycol or polyvinyl alcohol, to optimize the activity of the entrapped enzymes. The photostability, leaching, pKa and pH response of the entrapped probes were characterized, as was the performance of the entrapped enzymes, and an optimal set of processing conditions was obtained for each different sensing film. In general, the results indicated that SNARF-labelled dextran was the most useful pH sensitive dye owing to insensitivity to leaching and photobleaching. Furthermore, it was observed that the pKa and pH response of this probe was insensitive to preparation conditions. The performance of the co-entrapped enzymes was highly dependent on the type and level of additive, but in all cases, it was possible to obtain active enzymes with good performance characteristics. Reagentless sensing films for urea and glyceryl tributyrate (GTB) are demonstrated based on the detection of enzyme-mediated pH changes from films coated onto planar substrates. 相似文献
219.
《Arabian Journal of Chemistry》2020,13(12):8848-8887
Phthalocyanine (Pc) complexes are an important class of dyes with numerous (e.g., biological, photophysical, and analytical) applications. Among the methods used to improve the properties of these complexes, one should mention the introduction of different substituents, variation of the central metal ion, ligand exchange, and conjugation to nanomaterials (e.g., carbon-based nanomaterials and metal nanoparticles (NPs)). This work briefly reviews Pc complex conjugation to Ag and Au NPs, highlights the different NP shapes, and discusses the diversity of conjugation approaches. Moreover, the use of UV–Vis spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering and Fourier transform infrared spectroscopy to characterize Pc-NP hybrids is summarized. The effect of conjugation on Pc photo-physicochemical properties (fluorescence, singlet oxygen generation, triplet state formation, and optical limiting behavior) is discussed, and future perspectives for the synthesis and applications of new hybrids are provided. 相似文献
220.
The synthesis and properties of a perylenediamide diol linker and several DNA hairpins possessing this linker are described. The diol linker absorbs and fluoresces strongly in the visible. Hairpins having poly(dA)-poly(dT) stems have fluorescence quantum yields and decay times similar to those of the linker, indicating that hole injection does not occur from the singlet excited linker into the base pair domain. Fluorescence quenching by dG or dZ bases is observed when these bases are located near the linker. The strong distance dependence of fluorescence quenching is consistent with a superexchange mechanism for electron transfer. Failure to observe formation of the linker anion radical by means of femtosecond time resolved absorption spectroscopy is attributed to fast charge recombination. The properties and behavior of the perylene linker and its hairpins are compared to those of other arenedicarboxamide linkers. 相似文献