Improved model for improving the inter-instrument agreement of spectrocolorimeters

A proposal by Robertson slightly modified by Berns and Petersen, to use spectral differences to predict systematic errors in spectrophotometers has found limited success in practical application. Porter suggested a way to improve the level of agreement between standardizing laboratories based on the Berns and Petersen method but suggested using derivatives calculated from piecewise polynomial splines. He did not know it at the time, but such a model was already in use. That model now has over five years of successful field testing and this paper discloses how the model was developed, the efficiency with which it can reduce systematic errors and the kinds of errors that cannot presently be corrected by computational comparison of reflectance or transmittance factor readings. For instruments of the same basic design, this model will produce a reduction of the systematic errors in colorimetric coordinates on the order of factors of 2–3. The magnitude of the initial color differences appears to be irrelevant. The corrective power of the model is limited by the numerical noise generated by the process of simulating analytical derivatives. We show that instruments with average color differences of 1.0 CIELAB unit can be reduced to a level of 0.5–0.3 units. Our testing has included a large variety of material samples including textiles, plastics, inks, paints and ceramics. Over 400 samples have been measured in proving this method. In addition, the model has been in place in industrial environments where multiple instruments of different manufacturer have been made to operate successfully from the same set of laboratory standards at reproducibility levels that rival those of national standards laboratories.     

应用吸光光度法测定液本有机产品的色度

根据色度学原理应用吸光光度法测定了工业乙酸酐及冰乙酸产品的色度。应用分光光度计,建立标准曲线,通过测定样品在380-780nm处的透光度,计算黄变度,查得其相应铂-钴色度号。此方法能准确地反映了样品的真实颜色,消除了人为误差,提高了分析方法的准确度。适用于日常工业分析、科学研究及仲裁,对于目视比色时存在色调干扰的样品测定尤为重要。     

Acid decomposition method for visual colorimetric determination of molybdenum in geochemical exploration

A mixture of nitric and sulphuric acids is used for the decomposition of geochemical samples. Determination of molybdenum at the μg g^?1 level is effected by visually comparing the colour of the thiocyanate complex. The acid medium seems to be well suited for the colorimetric determination of molybdenum. The same solution can be used advantageously for atomic absorption measurements for larger amounts of molybdenum. The method is suitable for batch analysis and results in a high throughput.     

The photochromic effect of bismuth vanadate pigments. Part I: Synthesis, characterization and lightfastness of pigment coatings

We report on investigations of the photochromic effect of BiVO₄ pigments. Emphasis is placed on an approach widely used in industrial color testing. By means of colorimetry ΔE_ab^*-values, which measure the perceived color difference, can be calculated from reflectance spectra of non-illuminated and illuminated pigment coatings. Pigments were prepared by either wet-chemical precipitation or solid-state reactions. Depending on the choice of starting compounds, lightfastness was found to vary significantly. Small amounts of impurity phases do not seem to affect photochromism. In contrast, impurities like Fe and Pb cause intense photochromism. The role of Fe is suggested by trace analyses, which (in case of pigments synthesized by precipitation reactions) reveal a correlation between concentration and ΔE_ab^*. Indications are found that other effects like pigment-lacquer interactions might also be of importance. Difference reflectance spectra turn out to vary in shape depending on the type and concentration of impurities or dopants. For BiVO₄ at least three different mechanisms of photochromism can be assumed.     

Field procedures to assess soils and waste disposals

The aim of this research was the development of rapid analytical test methods for arsenic, lead, cadmium, chromium(VI), copper, nickel, and zinc to classify waste materials into waste classes and assess contaminated soils for purification purposes. In order to estimate the danger potentials of contaminated soils, a rapid ecotoxicological method was developed (A. Götzl, H. Malissa, W. Riepe, FACT 3 (6) (1999) 329.). These rapid analytical and ecotoxicological tests offer an instrument to comprehensively assess soils and wastes. The developed rapid methods are suitable for the elution of different soils and wastes, the analysis of the eluates and also for waste waters with concentrations greater than 0.1 mg l⁻¹ arsenic, 0.5 mg l⁻¹ lead, 0.01 mg l⁻¹ cadmium, 0.1 mg l⁻¹ chromium(VI), 0.3 mg l⁻¹ copper, 0.5 mg l⁻¹ nickel and 0.1 mg l⁻¹ zinc in the eluate. Our developed rapid analytical test methods described below can be implemented on site, are of low cost and are not time-consuming (about 30 min). They also do not need to be carried out by highly qualified specialists only, they can also be easily applied by persons with some experience. The comparability of results obtained using the developed rapid test method and standardised methods was tested with various matrices.     

Assay of Peracid in the Presence of Excess Hydrogen Peroxide

ABSTRACT

A simple and rapid colorimetric method for the determination of peracids in the presence of excess hydrogen peroxide is described. The method is based on the selective destruction of hydrogen peroxide by the enzyme catalase, a procedure which leaves the peracid unaffected. The residual solution, then containing only peracid, can be assayed using the stoichiometric oxidation of 2, 2′-azino-bis-(3-ethyl-benzthiazoline-6-sulfonate) diammonium salt (ABTS) in the presence of peroxidase, a reaction that can be quantified photometrically at 405 run. The double-enzyme method was extended to microtiter plate-based systems, thus providing an easy way of analyzing multiple samples for their peracid content.     

A colorimetric and surface-enhanced Raman scattering dual-signal sensor for Hg based on Bismuthiol II-capped gold nanoparticles

The addition of Bismuthiol II to the gold nanoparticles (AuNPs) solution led to the aggregation of AuNPs with a color change from red to blue. As a result, hot spots were formed and strong surface-enhanced Raman scattering (SERS) signal of Bismuthiol II was observed. However, the Bismuthiol II-induced aggregation of AuNPs could be reversed by Hg²⁺ in the system, accompanied by a remarkable color change from blue to red. As evidenced by UV–vis and SERS spectroscopy, the variation in absorption band and SERS intensity was strongly dependent on the concentration of Hg²⁺, suggesting a colorimetric and SERS dual-signal sensor for Hg²⁺. The sensor had a high sensitivity, low detection limits of 2 nM and 30 nM could be achieved by UV–vis spectroscopy and by SERS spectroscopy, respectively. Other environmentally relevant metal ions did not interfere with the detection of Hg²⁺. The method was successfully applied to detect Hg²⁺ in water samples. It was simple, rapid and cost-effective without any modifying or labeling procedure.     

Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes

Based on target recycling amplification, the development of a new label-free, simple and sensitive colorimetric detection method for ATP by using un-modified aptamers and DNAzymes is described. The association of the model target molecules (ATP) with the corresponding aptamers of the dsDNA probes leads to the release of the G-quadruplex sequences. The ATP-bound aptamers can be further degraded by Exonuclease III to release ATP, which can again bind the aptamers of the dsDNA probes to initiate the target recycling amplification process. Due to this target recycling amplification, the amount of the released G-quadruplex sequences is significantly enhanced. Subsequently, these G-quadruplex sequences bind hemin to form numerous peroxidase mimicking DNAzymes, which cause substantially intensified color change of the probe solution for highly sensitive colorimetric detection of ATP down to the sub-nanomolar (0.33 nM) level. Our method is highly selective toward ATP against other control molecules and can be performed in one single homogeneous solution, which makes our sensing approach hold great potential for sensitive colorimetric detection of other small molecules and proteins.     

差示-比色法测定乙醛肟含量的研究

乙醛肟水解产物羟胺将过量Fe^3 部分还原为Fe^3 ，再经邻菲罗啉显色，焦磷酸钾掩蔽剩余Fe^3 后，用差示－比色法进行乙醛肟的含量测定，取得了相当满意的结果。乙醛肟的平均回收率为99.96%（n=19，RSD＝0.7％）     

Spectroscopic Investigation of the Europium(3+) Ion in a New ZnY4W3O16 Matrix

A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu₄W₃O₁₆, crystallized in the orthorhombic system and was synthesized by a solid‐state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu³⁺ ions in ZnEu₄W₃O₁₆ and ZnY₄W₃O₁₆ : Eu³⁺ diluted phases (1, 5, and 10 mol‐% of Eu³⁺ ion) were studied basing on the f⁶‐intraconfigurational transitions in the 250–720 nm spectral range. The excitation spectra of this system (λ_em 615 and 470 nm) show broad bands with maxima at 265 and 315 nm related to the ligand‐to‐metal charge‐transfer (LMCT) states. The emission spectra under excitation at the O→W (265 nm) and O→Eu³⁺ (315 nm) LMCT states present the blue‐green emission bands. The emission of tungstate groups mainly originate from the charge‐transfer state of excited 2p orbitals of O^2? to the empty orbitals of the central W⁶⁺ ions. On the other hand, in the emission of the Eu³⁺ ions, both the charge transfer from O^2? to Eu³⁺ and the energy transfer from W⁶⁺ ions to Eu³⁺ are involved. The emission spectra under excitation at the ⁷F₀→⁵L₆ transition of the Eu³⁺ ion (394 nm) of ZnY₄W₃O₁₆ : Eu³⁺ diluted samples show narrow emission lines from the ⁵D₃, ⁵D₂, and ⁵D₁ emitting states. The effect of the active‐ion (Eu³⁺) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented.