Showing papers on "Color reaction published in 2005"

Color Reaction of 2-(2-Quinolylazo)-5-Dimethylaminoaniline with Palladium and Its Application

Abstract: A new chromogenic reagent, 2-(2-quinolylazo)-5-dimethylaminoaniline (QADMAA) was synthesized. A sensitive, selective and rapid method for the determination of palladium based on the rapid reaction of palladium(II) with QADMAA was developed. In the presence of 0.5-2.5 mol L-1 of hydrochloric acid solution and cetyl trimethylammonium bromide medium QADMAA reacts with palladium to form a violet complex with a molar ratio of 1:2 (palladium to QADMAA). The molar absorptivity of the chelate is 1.35x105 L mol-1 cm-1 at 600 nm. Beer's law is obeyed in the range of 0.01 to 0.6 m g mL-1. The detection limit is 1.2 m g L-1. This method has been applied to the determination of palladium with good results.

Hydrogen sulfide gas detection material

Abstract: PROBLEM TO BE SOLVED: To measure highly accurately hydrogen sulfide gas in a wide concentration range without changing the concentration of a reaction reagent of a carrier. SOLUTION: This material is constituted by being equipped with a color reaction base material 4 formed by carrying copper nitrate and a humectant on a carrier as the reaction reagent color-reacting with a test gas, and a film 3 having permeability to the test gas, and by laminating the film 3 at least on the inflow face side of the test gas of the color reaction base material 4. COPYRIGHT: (C)2005,JPO&NCIPI

A Modified Sensitive Micro Spectrophotometric Determination Of Iron(III) By Thiocyanate Method

Abstract: A systematic study of the colour reaction formed between iron (llI) and thiocyanate reagent has been carried out by using micro-scale spectrophotometric method. The optimized data resulted conditions in obtaining unusual highest sensitivity with molar absorption of 2.9565x104I/mol.cm at wavelength of maximum absorption 480 nm in 0.2-1.4 N nitric acid medium containing 60% acetone and 25,000 fold molar excess of the thiocyanate reagent. Beer's law is valid for 0.1-4.0 ppm of iron (llI). Sandell's sensitivity is 0.002 I¼g/cm2. Effects of reagent concentration, order of addition, stability, acidity, types of solvents and diverse ions are reported. It has been found to give accurate results of iron estimations in pharmaceutical preparations and mustard seeds. The proposed optimized method has highest sensitivity, unusual stability and simplicity in operation, without involving cumbersome extractive procedure. Further, the procedure has additional advantages of economy, safety and less time consuming with minimum waste disposal.

Research of determination of glutamic acid by colorimetry

Abstract: This paper investigates the method of quantitative determination of glutamic acid by colorimetry in the principle of color reaction between α-amino-acids and ninhydrin , and mainly discusses the effect factors , reaction conditions and points for attention of this color reaction . As a method of quantitatively determining glutamic acid ,it is characterized by simplicity and practicability compared with conventional methods of determining glutamic acid . It is available in common lab operations and determination in the process of glutamic acid production.

SPECTROPHOTOMETRIC DETERMINATION OF Fe(III), Cu(II) AND UO2(II) IONS BY A NEW ANALYTICAL REAGENT DERIVED FROM CONDENSATION OF MONOETHANOLAMINE AND ACETYL ACETONE

Abstract: A highly sensitive and selective spectrophotometric method is proposed for direct trace determination of Fe(III), Cu(II) and UO2(II) in aqueous solutions. The method is based on the reaction of those cations with a new analytical reagent 2-ethanolimino-2-pentylidino-4-one (B3). Under the optimum reaction conditions and other important analytic parameters, B3 reacts with the investigated cations and forms colored complexes. The optimum pH for complex formation has been adjusted. The color reaction is rapidly completed and the absorbance remains stable for at least a week at room temperature. The Fe(III) complex is detected at λmax = 440 nm and pH = 3.5, the Cu(II) complex is detected at λmax = 340 nm and pH = 6.0, while that of UO2(II) is detected at λmax = 370 nm and pH = 4.0. BearLambert’s law is obeyed in the concentration range = 0.5 ‐ 3.0·10 ‐4 M (2 ‐ 17 μg/ml for Fe(III), 3 ‐ 9 μg/ml for Cu(II) and 13 ‐ 81 μg/ml for UO2(II) complexes. The stoichiometries of the formed complexes are determined using different spectrophotometric methods. The conditions for the complexation were determined. The rate of the reaction between Fe(III) ion and the ligand has been evaluated under pseudo first order condition. The ability of the present ligand to determine micrograms of Fe(III), Cu(II) and UO2(II) ions is tested and the resulted data are analyzed using statistical parameter to obtain the minimum error. The effect of various substances on the determination of the investigated cations is also investigated in detail. The results indicate that most of the studied co-existing substances could be tolerated in considerable amounts. The proposed method offers the advantages of sensitivity, rapidity, selectivity and simplicity without any prior separation or extraction. It has been applied to the analytic samples with satisfactory results.

The Color Reaction of Mercury(II) with the New Reagent 2-Methylthiophenyldiazoaminoazobenzene and Its Application

Abstract: A new and very sensitive and selective chromogenic reagent, 2-methylthiophenyldiazoaminoa-zobenzene (MTDAA), was synthesized and studied in detail for the determination of trace mercury(II) in water samples. The method is based on the color reaction between MTDAA and mercury(II). It was found that mercury(II) reacts with MTDAA in Na2B4O7-NaOH buffer solution (pH = 10.0) to form 1 : 2 red complexes; these show maximum absorption at 520 nm. Beer’s law is obeyed in 0–15 µg of mercury(II) in 25 mL of solution. The apparent molar absorptivity of the complex is 1.33 × 105 L/(mol cm); its limit of quantification, limit of detection, and relative standard deviation are 0.75 ng/mL, 0.27 ng/mL, and 1.0%, respectively, giving better sensitivity. The influence of the reaction variables and the effect of interfering ions are reported; most of the metal ions in water samples can be tolerated in considerable amounts. Only a few ions can interfere with the determination of trace mercury(II), but these can be eliminated by prior extraction. The proposed method is sensitive, simple, and rapid. It has been applied to the determination of trace mercury(II) in water samples with satisfactory results.

Determination of ammonium nitrogen in fermentationbroth through indophenol blue reaction

Abstract: A novel method for quantitative determinating of ammonium nitrogen was proposed to assay the nitrogen source in the fermentation industry by using the indophenol blue reaction. Optimizing the color reaction time, color stability conditions and the adding order of reactants, the correlation between the ammonium nitrogen concentration and the optical density was investigated. The method was validated through the intra-, inter-day repeatability tests and the recovery test, and determined the ammonium nitrogen concentration during the fermentation process of mildiomycin and S-adenosylmethionine. Results show that in the range of 0~7()mg/L, ammonium nitrogen concentration is significantly linear with the optical density of the reaction solution at 625()nm, and correlation coefficient is 0.998()6. The method has highly precise, accurate and is sensitive to detect subtle change of nitrogen source during the late phase of fermentation. The proposed method facilitate the adjustment of fermentation control strategy and the improvement of productivity.

Studies and Applications of Porphyrin Color Reagents

Abstract: Porphyrin compounds are a kind of very promising organic color reagents in analytical photometryAs a kind of highly sensitive color reagents,they have been applied to determine many trace metallic ionsThe color performance and application of porphyrin reagents used as color veagents in the last six years in China are reviewed,the questions met and improving methods are discussed,and their progressing tendency is pointed out as well

On the Relationship between Color Reaction of Starch with I_2 and Content of Reducing Sugar

Abstract: An experiment was designed that combines both qualitative and quantitative experiment on sugar. The content of reducing sugar is measured when the different colors change during the reaction of starch with I_2, and a qualitative result corresponding to a quantitative experiment is reported. When the concentration of substrate starch is 2 g/L and that of α-amylase is 0.5u/mL, the solution shows blue, violet and red for the reaction time of 0～2.5 minu, 2.5～5.5min and 5.5～13.5 min respectively. Beyond 13.5 min, the solution turns to colorless. The decomposition rates of reducing sugar corresponding to the changing point of colors are 45% (blue to violet), 66%(violet to red) and 76%(red to colorless) respectively.

Solid phase extraction-spectrophotometric determination of lead in environmental samples with p-sulfobenzylidene thiorhodanine

Abstract: A new chromogenic reagent,p-sulfobenzylidene thiorhodanine(SBDTR) was synthesized,and its structure was verified by elemental analysis,IR and HNMR.The color reaction of lead with SBDTR was studied.In HAc-NaAc buffer solution at pH 4.5 and in the presence of Tween-80,SBDTR can react with lead? to form a stable 2∶1 complex.The complex can be extracted by Waters Sep-Pak C_(18) cartridge and eluted by ethanol,the enrichment multiple can achieve 50 times.The molar absorptivity of the complex is 1.05×10~5 L·mol~(-1)·cm~(-1) at 552 nm.Beer's law is obeyed in the range of 0.05-4.0 μg/mL for lead.This method can be applied to the determination of lead in environmental samples.

Spectrophotometric determination of lead in environmental water and food samples with p-aminobenzylidene-thiorhodanine by solid phase extraction

Abstract: AbstrcatA new chromogenic reagent, p-aminobenzylidenethiorhodanine (ABTR) was synthesized, and its structure was verified by elemental analysis, IR, and ()~1HNMR. The color reaction of lead with ABTR was studied. In the pH 3.8 HAc-NaAc buffer solution with Tween-80, ABTR can react with lead (Ⅱ) to form a stable 2∶1 complex. This complex can be extracted by Waters Sep-Pak-C_(18) column and eluted with ethanol. The molar absorptivity is 1.09×10~5 L·moL~(-1)·cm~(-1) at 545 nm. Beer′s law is obeyed in range of 0.05～(4 μg/mL). This method can be applied to the determination of lead in environmental water and food samples with satisfactory results.