Differential spectrophotometry

The principles of various methods of differential spectrophotometry are briefly discussed. Practical problems connected with the measurements are presented and analytical applications so far available are reviewed.     

Flow injection spectrophotometry followed by atomic Absorption spectrometry for the determination of iron(II) and total iron

In the flow system described, iron(II) is measured spectrophotometrically with 1,10-phenanthroline, and total iron is determined in the same flow line by atomic absorption spectrometry. Linear calibration ranges are 0.1–35 and 0.1–10 μg ml^?1 for iron(II) and total iron, respectively.     

Ion-exchanger analogue-derivative spectrophotometry

Summary Derivative spectrophotometry using the analogue differentiation circuit was introduced to ion-exchanger colorimetry in order to enhance its sensitivity and remove the large background caused by the absorption of the ion-exchange resin layer itself. Determination of micro-amounts of copper with ,,,-tetrakis(1-methylpyridinmm-3-yl)porphine [T(3-MPy)P], chromium with 1,5-diphenylcarbazide (DPC) and iron with 1,10-phenanthroline (PHEN) or 2,4,6-tris(2-pyridyl)-s-triazine (TPTZ) are described as examples for the application of this new technique. The lower determination limit is in the range of 0.2 to 2 ppb. This technique is applicable to all kinds of ion-exchanger colorimetry reported already without any trouble.

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Analogderivativ-Spektralphotometrie am IonenaustauscherBestimmung von Kupfer, Chrom und Eisen

Zusammenfassung Die Derivativ-Spektralphotometrie mit Analogdifferential-Schaltung wurde auf die Ionenaustausch-Colorimetrie angewendet, um deren Empfindlichkeit zu erhöhen und die große Untergrundabsorption durch die Austauscherschicht zu eliminieren. Als Beispiele für das Verfahren wird die Bestimmung von Kupfer mit ,,,-Tetrakis (1-methylpyridinium-3-yl)porphin, von Chrom mit 1,5-Diphenylcarbazid und von Eisen mit 1,10-Phenanthrolin oder 2,4,6-Tris(2-pyridyl)-s-triazin beschrieben. Die untere Bestimmungsgrenze liegt im Bereich von 0,2–2 ppb. Das Verfahren kann für alle Arten von Ionenaustausch-Colorimetrie angewendet werden.

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Presented at the 47th annual meeting of the Chemical Society of Japan in Kyoto, April 1983     

Thermal lens spectrophotometry

A thermal lens effect induced under laser irradiation is useful for the detection of very small absorptions. This forms the basis of a new technique which is becoming increasingly important as a tool for ultratrace analysis.     

Determination of chlorprothixene and amitryptyline hydrochlorides by UV-derivative spectrophotometry and UV-solid-phase spectrophotometry

Two methods for spectrophotometric determination of chlorprothixene and amitryptyline hydrochlorides were proposed. One of them is based on spectral analysis of their derivative spectra. The measurement of the value at 316.0 nm of first derivative was used for construction of calibration graph for chlorprothixene. The Beer law was obeyed in the concentration range 0.5-50.0 microg ml(-1). The amplitude of the second derivative at 261.4 nm was used for determination of amitryptyline in the range 0.5-75.0 microg ml(-1). The second proposed method is utilized the use of solid sorbent for simultaneous preconcentration and assay of studied compounds. For this purpose the filtration gel Sephadex G100 was applied. The elaborated solid-phase spectrophotometric method was used for determination of chlorprothixene at 268.0 nm in the range 2.5-75.0 microg ml(-1) and amitryptyline at 238.0 nm in the concentration range 10.0-75.0 microg ml(-1).     

Solvents for ultraviolet spectrophotometry

Mathematical relations are presented showing the effect of light absorption by the solvent on the absorption measurements. A simple modification in the silica-gel adsorption method of purifying isooctane is described that greatly improves the transmittance in the 2000 Å region. A procedure of purifying dioxan is also included.     

Low detection limit spectrophotometry

An efficient, more sensitive and accurate spectrophotometric process is possible and can be used to obtain qualitative or quantitative results for analytes at limiting concentrations lower than usual. Transmission measurements (incident light power, P₀, or transmitted, P) are performed with a fluorescence spectrometer. One cell only is used to measure standards or unknown solutions, placed between the standard holder cuvette and the emission monochromator of the instrument. The source of the radiant power (P₀) is not the xenon lamp but the fluorescence or scattered radiation from the holder cuvette filled with an appropriate solution. The analyte concentration is found from a calibration graph, based upon Beer’s law or the approximate formula P₀−P=2.303P₀εbc, which is valid for dilute solutions. Determination of iron in a reference material, using 1,10-phenanthroline as the chromogenic reagent, was chosen as an example to demonstrate the suitability of the proposed method and clarify several important statistical questions. Also discussed is why and to what extent molecular fluorescence methods are more sensitive than molecular absorption methods.     

Quantitative spectrophotometry using integrating cavities

Absorption spectrophotometry, a standard tool for quantitative analysis, suffers from two major drawbacks: lack of sensitivity and vulnerability to scattering. It has been pointed out earlier that the solution to these problems lies in using a reflecting cavity as a sample holder. Due to multiple reflections at the cavity wall, the effective pathlength becomes considerably larger than the diameter of the cavity, and scattering losses are eliminated because scattered light is prevented from escaping the detector. Though much effort has been spent in analysing and improving the performance of such a device, often called an integrating cavity absorption meter (ICAM), a simple strategy for deducing the absorbance of the sample is still lacking. It is shown here that the absorbance A' measured by using an ICAM exhibits a sublinear increase with the solute concentration C. The physical reason for this departure from linearity is explained, and a straightforward procedure for converting A' to the true absorbance A (proportional to C) is established. The reliability of the procedure is demonstrated by comparing the ICAM absorption spectrum of dilute dye solutions with the spectra of more concentrated solutions recorded in a conventional spectrophotometer. The ability of the device to cope with scattering was tested by filling the ICAM with a suspension of chloroplasts, and the spectrum was found, as expected, to be free from scattering artefacts.     

分光光度法测定薯蓣皂苷元

采用高氯酸反应使薯蓣皂苷元显色 ,对影响显色反应的主要因素进行了考察 ,于 41 0nm波长处对穿山龙中薯蓣皂苷元的含量进行测定 ,测定结果与高效液相色谱法相近。方法的线性范围为 3.1 2～2 1 .84μg mL ,适用于薯蓣皂苷元提取过程中的常规检测     

Using gold nanoparticles in spectrophotometry

Published data on the use of gold nanoparticles in spectrophotometry are summarized. Data on methods for preparing gold nanoparticles and their optical properties are presented. The main approaches on which spectrophotometic methods of substance determination using gold nanoparticles are based are discussed. Examples of determining of metal ions, anions, and organic compounds are presented.     

吸收光度法中的峰位移

该文从吸收干扰、单色光性质及被测物吸收特性改变三个方面探讨了吸收光度法中吸收峰位移的原因、影响及其消除与应用。重点论述了吸收干扰中的相长与相消干扰引起的吸收峰位移规律。该规律为研究试剂与溶剂中杂质、样品中共存物、反应试剂与产物等的吸收干扰引起被测吸收峰位置、高度及形状的变化提供了理论依据。运用被测物标准溶液的正、负吸光度吸收曲线提供的信息与吸收峰位移规律研究吸收光度法应用的新方法,为定量分析、消除共存物干扰、化学反应及试剂选择性等研究提供了新手段。作为峰的相长与相消干扰引起的测定峰位移规律也适用于检测峰的其它仪器分析。     

酶催化光度法测定异烟肼

基于异烟肼对牛血红蛋白模拟酶催化体系的抑制作用,建立了酶催化光度法测定异烟肼的新方法。研究了该抑制反应的最佳实验条件及动力学行为,测定的线性范围为3.65×10-8～3.65×10-6mol/L,检出限为5.4×10-9mol/L。对浓度为1.27×10-6mol/L的异烟肼进行11次平行测定,其相对标准偏差为3.9%。该方法可用于异烟肼注射液中异烟肼含量的测定。     

分光光度法测定高铁酸钠的浓度

目前 ,测定高铁酸盐浓度的方法有铬酸盐法[1] 、溴酸盐法及铈酸盐法[2 ] 、量气法[3] 、直接分光光度法[4] 。铬酸盐法、溴酸盐法、铈酸盐法是基于高铁酸盐的强氧化性 ,在碱性条件下将Ｃｒ(Ⅲ )、Ａｓ(Ⅲ )、Ｃｅ(Ⅱ )等化合物氧化为对应的高价化合物 ,再用已知浓度的还原剂滴定而测定高铁酸盐的浓度。该类方法操作简单、准确度高 ,但样品用量大 ,方法的灵敏度较低 ,环境污染较严重。量气法是依据高铁酸盐与非还原性酸反应放出Ｏ2 ,通过测定放出Ｏ2 的体积 ,而测定高铁酸盐的浓度。该法简便可行 ,但装置较复杂 ,环境温度、气压对测定结果的…     

Determination of molybdenum by atomic-absorption spectrophotometry

A new procedure is described for precise estimation of molybdenum by atomic-absorption spectrophotometry using an airacetylene flame. Phosphoric acid was found to be effective in suppressing interference by Fe(III), Al, Sb(III), Ca, Mg, Pb and Mn(II).     

Photochemical reaction monitoring by ultra-violet spectrophotometry

Within the framework of the monitoring of the trichloroacetylchloride (TCAC) photosynthesis, ultra-violet (UV) spectrophotometry is proposed as a simple and rapid tool allowing, in real time, the control of the process efficiency. A good correlation has been obtained between the results acquired by this alternative method and the standard gas chromatography.