Showing papers on "Color reaction published in 2015"

Determination of Apparent Amylose Content in Rice by Using Paper-Based Microfluidic Chips.

Abstract: Determination of apparent amylose content in rice is a key function for rice research and the rice industry. In this paper, a novel approach with paper-based microfluidic chip is reported to determine apparent amylose content in rice. The conventional color reaction between amylose and iodine was employed. Blue color of amylose-iodine complex generated on-chip was converted to gray and measured with Photoshop after the colored chip was scanned. The method for preparation of the paper chip is described. In situ generation of iodine for on-chip color reaction was designed, and factors influencing color reaction were investigated in detail. Elimination of yellow color interference of excess iodine by exploiting color removal function of Photoshop was presented. Under the optimized conditions, apparent amylose content in rice ranging from 1.5 to 26.4% can be determined, and precision was 6.3%. The analytical results obtained with the developed approach were in good agreement with those with the continuous flow analyzer method.

Utilization of cloud-point extraction for colorimetric determination of trace amounts of thorium(IV) in real samples

Abstract: A cloud point extraction process using mixed micelles of the cationic surfactant CTAB and non-ionic surfactant Triton X-100 to extract thorium(IV) from aqueous solutions was investigated. The method is based on the color reaction of thorium with 5-(2′,4′-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD) in the presence of potassium iodide in hexamethylenetetramine buffer media and mixed micelle-mediated extraction of the complex. The optimal extraction and reaction conditions (e.g. surfactant concentration, reagent concentration, effect of time) were studied and the analytical characteristics of the method (e.g. limit of detection, linear range, molar absorptivity, Sandell sensitivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.5–15 ng mL−1 of thorium(IV) ion and the detection limit of the method is 0.16 ng mL−1. The interference effect of some anions and cations was also tested. The proposed method was successfully applied for the preconcentration of trace thorium in natural water samples as well as in plant material and soil samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) with satisfactory results.

Fruit extract dyes as photosensitizers in solar cells

Abstract: 6+ . The leaf powder was found to be stable for at least one year when kept in dry condition at room temperature. However, compositions of plant parts are known to vary due to various factors like variety, climate, soil, competition, diseases, etc. Therefore, the same batch of reagents should be used for preparing the calibration curve and analysis of samples. Table 3 lists other plant extracts that gave similar colour reaction as S. jambolanum. Therefore, it may be concluded that compounds responsible for the colour reaction are widely distributed. The S. jambolanum extract gave a deep purple colour with ferric iron, lemon yellow colour with titanium and a bluish colour with vanadate ion. A compound like quercetin or tannic acid may be involved in colour development.

Determination of vanadium in different environmental, Leafy vegetable andbiological samples using 2-hydroxy-1-naphthaldehyde-p-hydroxybenzoichydrazone (HNHBH) spectrophotometrically

Abstract: 2-hydroxy-1-naphthaldehyde-p-hydroxy benzoic hydrazone (HNHBH) is used as a new analytical reagent for the direct and derivative spectrophotometric determination of vanadium (V). It reacts with vanadium in acidic medium (pH 4.0, sodium acetate and acetic acid buffer) to form deep yellow colored (λ max, 430 nm) 2:3 (V- HNHBH) complexes. The colour reaction is instantaneous and the absorbance remains constant for about 72h. The molar absorptivity and Sandall’s sensitivity were found to be 2.30 x 104 L mol-1cm-1 and 0.0025 μg cm-2 respectively. The system obeys Beer’s law in the range of 0.101-1.121 μg mL-1 of V (V). Tolerance limits of various foreign ions were also studied. The complex was fairly stable (stability constant 4.73 x 1019) and Second and third order derivative spectrophotometric methods were also developed for the determination of vanadium (V) which showed greater sensitivity and selectivity. The proposed method was applied for the determination of vanadium (V) in Different Environmental, Leafy vegetable, and Biological Samples. The method has high sensitivity, selectivity, and precision and accuracy.

Spectrophotometric determination of mercury (II) in environmental samples and synthetic mixtures using N'-(1-(pyridin-2-yl) ethylidene) isonicotinohydrazide as sensitive analytical reagent

Abstract: N'-(1-(Pyridin-2-yl)ethylidene)isonicotinohydrazide (2-ACPINH) is identified as a selective and sensitive analytical reagent for the determination of trace levels of mercury (II) in environmental samples and synthetic mixtures by spectrophotometry. 2-ACPINH reacts with mercury (II) forms greenish yellow colored 2:3 (Hg-2-ACPINH) complex at pH 5.5, in aqueous DMF. The Hg-2-ACPINH complex shows maximum absorbance at λmax 357nm. The color reaction is immediate and the absorbance remains constant for about 24h.The molar absorptivity coefficient and Sandell’s sensitivity are found to be 5.48x104 L.mol-1 cm-1 and 0.0010μg cm-2of mercury (II) respectively. The linear regression coefficient is 0.99925 and standard deviation is 0.04175. The system obeys Beer`s law in the range of 0.2-2.0 μg mL-1 of Hg (II). Large number of cations, anions and complexing agents do not interfere in this method. This method is successfully applied for the determination of mercury in a number of environmental water samples (potable and polluted), food samples and synthetic mixtures.

A Reaction of Aspirin with Ferrous Gluconate.

Abstract: A color reaction of aspirin with ferrous gluconate was studied by UV-Vis spectrophotometry and HPLC-MS. It was found that the UV-Vis spectra of the two drugs were different before and after they were mixed in water at about 0.3 M (diluted by >20 times for analysis), indicating that a complexation reaction took place. The drug-iron complex dissociated when the reacting solution was diluted by 400 times. The by-products of the reaction identified by HPLC-MS were salicylic acid, acetylated gluconic acid, salicylate-gluconic acid conjugate, and an oxidized product of salicylic acid that was complexed with iron with a molecular weight of 212. This reaction may be used as an important consideration to optimize the dosing regime of the two drugs and to help explain some pharmacological reactions between aspirin and biomolecules.

Spectrophotometric Determination of Bendiocarb After Synthesis a New Colored Compound with a Para-Amino Phenol in Environmental Water Samplesf

Abstract: A simple, sensitive, rapid and accurate spectrophotometric method was developed for the analysis of parts per million levels of widely used carbamate pesticide bendiocarb. The proposed method was based on alkaline hydrolysis of the bendiocarb pesticide, and the resultant hydrolysis product of bendiocarb was coupled with para-amino phenol to give blue color product with λmax (630 nm). This compound shows an absorption maxima at a wavelength of (630 nm) with apparent molar absorptivity (2.018 × 104 L mol-1cm-1) and obeyed Beer’s law in the concentration range of (0.1-10 μg/mL). Sandell's of the color reaction are 0.01106 μg cm-2. The effect of the non-target species on the determination of bendiocarb was studied. The formation of colored derivatives with the coupling agents is and stable for 3-6 hr.

Systematic Investigation on AlCl_3 Colorimetric Determination of Total Flavonoids from Pyracantha Fortuneana Fruit

Abstract: Rutin was taken as reference substance and the optimal condition of aluminum chloride colorimetric assay affecting the determination of total flavonoids from Pyracantha fortuneana extract was established. Several parameters, such as the standard substance, light, reaction time and temperature, concentration and the amount of chromogenic agent, p H and buffer dosage that affecting the color reaction of total flavonoids were investigated systematically. The results indicated the appropriate reaction conditions were as the following:2 m L2 %(m/m) Aluminum chloride was added to 1 m L pyracantha extract with specific concentration, after being blended the reaction was carried out at 30 ℃ for 12 min, then absorbance was measured at 285 nm. As a result,Statistical analysis showed the method had good repeatability, stability, reproducibility and high recovery rate.

Determination of Dicofol in Various Environmental Samples by Spectrophotometric Method Using Chromogenic Reagent

Abstract: A sensitive spectrophotometric method for determination of dicofol in subparts per million levels is described, which is based on Fujiwara reaction. Dicofol on alkaline hydrolysis gives chloroform, which reacts with pyridine to produce red color. The color is discharged by addition of glacial acetic acid. The glutaconic aldehyde formed reacts with 4-aminoacetanilide to gave an orange-red dye which is extractable in 3-methyl-1-butanol. The extracted dye shows absorption maximum at 525 nm. Beer's law is obeyed in the range of 0.025–0.25 μg mL−1. Important analytical parameters such as time, temperature, reagent concentration, acidity etc. have been optimized for complete color reaction. Sandell's sensitivity and molar absorptivity for the system were found to be 0.000343 μg cm−2 and 1.077 × 106 L mol−1cm−1, respectively. The proposed method is satisfactorily applied to microlevel determination of dicofol in various environmental samples.

Method for determining false positive reaction of urinary urobilinogen in qualitative analysis using color reaction and qualitative analyzing device using the same method

Abstract: PROBLEM TO BE SOLVED: To provide a method for determining false positive reaction of urine protein in qualitative analysis using color reaction and a qualitative analyzing device using the same method.SOLUTION: A method for determining false positive reaction of urine protein in qualitative analysis using color reaction comprises the steps of: bringing urine into contact with a reagent part of an inspection object provided with a reagent for urine protein and color reaction; measuring the color of the reagent part at least twice immediately after bringing the urine into contact with the reagent part and after end of the color reaction; and determining whether the urine protein indicates positive reaction or false positive reaction on the basis of an amount of change of a blue component obtained from color information of the measured reagent part or on the basis of an amount of change of a blue component ratio, a red component ratio, or a green component ratio.