Showing papers on "Color reaction published in 2009"

Dry chemistry test paper for quantitative determination of urea content in human blood

Abstract: The invention belongs to the technical field of in-vitro clinical diagnostic reagent, in particular to a dry chemistry test paper for quantitative determination of urea content in human blood. The test paper comprises an upper, a middle and a lower support layers and testing layers thereof and is separated into a hand-held area and a test area. The test area is composed of a diffusion layer, a reagent layer and a color reagent layer from the top down. A loading hole is arranged on the upper support layer, a test sample is introduced into the diffusion layer from the loading hole to penetrate into the reagent layer, then enzymatic reaction is carried out on the reagent layer, ammonia is generated by catalyzing urea by using urease, and under the alkaline environment, the generated ammonia spreads to the color reagent layer to perform color reaction with the indicator of ammonia. The variation of optical density can be measured with a reflectance spectrophotometer through a test hole on the lower support layer. The test paper can be used to quantitatively test the urea content in human blood, provides basis for the diagnosis of renal function, and is suitable to be used in emergency rooms of the hospitals.

A Rapid Spectrophotometric Method for Trace Determination of Zinc

Abstract: A simple, sensitive, and highly selective method is proposed for the determination of zinc(II) using a bis-azo dye, 2,6-bis(1-hydroxy-2-naphthylazo)pyridine as spectrophotometric reagent. At pH 7.8, in 50% (v/v) ethanol–water medium, the complex is found to obey Beer’s law up to 1.3 mg/L with an optimum concentration range between 0.19 and 1.0 mg/L. Sandell’s sensitivity of the color reaction was calculated to be 0.0011 μg cm−2 with molar absorptivity of 6.0 × 104 L mol−1 cm−1 at 560 nm. The optimum conditions for the determination of Zn(II) with the reagent were ascertained. The complexation at different pH was studied in water–ethanol medium. The composition of the complex is 1:2. The action of some interfering ions was verified, and the developed method applied successfully for the estimation of zinc levels in food and milk samples, and the results were then compared with those obtained by using AAS.

Colorimetric Detection of Explosives

Abstract: Publisher Summary This chapter focuses on color reactions that are extensively used in the field of explosives analysis. Their application is easy, the equipment required is simple and inexpensive, their sensitivities are often in the sub-microgram range, and they enable rapid, on-site diagnostic detection of explosive materials. They are also used for preliminary laboratory tests of materials suspected of being explosive and can help in diagnosing impurities and degradation products of explosives. The main drawback of the use of color reactions for the analysis of explosives lies in their low specificity. Polynitroaromatic compounds were reported to undergo color reactions with numerous bases, such as ammonia in methanol and aqueous solution of tetramethyl-ammonium hydroxide. A completely different approach involves the reduction of a nitroaromatic compound to the corresponding aromatic amine in which Zn, SnCl2, and TiCl3 in acidic medium were used as reducing agents. The most important color reaction for nitrate esters and nitramines is based on the formation of nitrite ions (NO2), upon reaction of these compounds with alkalis, which are then detected by the classical Griess reaction. In 1999, Keinan and Itzhaky registered a patent on peroxide explosive tester, which enabled rapid on-site detection of triacetonetriperoxide (TATP). In the presence of organic peroxides, the outcome is a green-blue color and the detection limit is in the sub-microgram level. A simple, fast, and specific color test for urea nitrate was reported recently by Almog et al., which is based on the reaction between urea nitrate and ethanolic solution of p-dimethylaminocinnamaldehyde (p-DMAC) under neutral conditions from a red pigment that is formed within 1 min from contact.

Spectrophotometric determination of tranexamic acid using vanillin.

Abstract: A new spectrophotometric method has been examined for the determination of the tranexamic acid (TA) by derivatization with vanillin (VAN). The molar absorptivity of TA was calculated 25,160 L x mol(-1) x cm(-1) at lambdamax 354 nm and obeyed the Beer's law within 0.5-2.5 microg x mL(-1). The color reaction was highly stable and did not show any change in absorbance up to 24 h. The method was applied for the analysis of TA from capsules, injections and tooth pastes. The amounts of TA found in capsules, injections and tooth pastes of various pharmaceutical companies were observed with 249.0-250.9 mg/capsule, 249.3-250.7 mg/injection and 0.048%-0.049% in tooth pastes with relative standard deviation (RSD) 0.2%-5.0% (n = 3).

Trace determination of copper in foodstuffs and biological samples.

Abstract: A new heterocyclic bis-azo dye, 2,6-bis(4-sulfo-1-hydroxy-2-naphthylazo)pyridine, sodium salt (PBS), has been prepared and developed as a sensitive and highly selective chromogenic reagent for spectrophotometric determination of copper. The reagent is found to give a 1:2 (M/L) complex at pH 6.0. Beer's law is followed up to 1.8 ppm with an optimal concentration range between 0.2 and 1.4 ppm. Sandell's sensitivity of the color reaction was calculated to be 0.0013 µg cm−2 with molar absorptivity of 4.9 × 104 l·mol−1 cm−1 at 572 nm. The interfering effects of various cations and anions were also studied. The proposed method was successfully applied to the determination of copper(II) in milk, tea samples, cereals, and legume grains consumed by the Indian vegetarians and in some biological samples. Comparison of the results with those obtained using an atomic absorption spectrophotometer tested the validity of the method.

Cloud Point Extraction and Spectrophotometric Determination of Sulfide in Water Samples using Ethylene Blue Formation Reaction

Abstract: A rapid, selective, and sensitive cloud point extraction process using mixed micelle of a nonionic surfactant, Triton X-114, and an anionic surfactant, SDS, to extract sulfide from aqueous solutions was investigated. The method is based on the color reaction of sulfide with N,N-diethyl-p-phenylenediamine (DPD) in the presence of suitable oxidizing reagent (Fe3+) in acid media and cloud point extraction of ethylene blue (EB) dye. Various factors and optimal extraction and reaction conditions like: acid, Fe3+, reagent, and surfactant concentration were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, RSD%) were obtained. Linearity was obeyed in the range of 1–100 ng mL−1 of sulfide ion. The detection limit of the method is 0.5 ng mL−1 of sulfide ion. The interference effect of some anions, cations, and neutral species was also tested. The method was applied to the determination of sulfide in spring, river, and waste water samples.

Cross-linking Staining of Fibroin by Genipin in Solution

Abstract: Genipin,a natural iridoid compound,was transformed to blue pigment by the reaction with amino acids. Amethyst solution was formed when colorless fibroin abstracted from natural silk was mixed with genipin. The effects of temperature and acidity or alkalinity on genipin-fibroin reaction and the product stability against light were studied with UV-vis spectra analysis. The mechanism of the reaction was primarily investigated through fluorescence spetra. The results indicated that the reaction products had a characteristic absorbance at 590 nm,while high temperature and pH accelerated the color reaction and the color of the reaction products was correlated with pH changing,tending to be blue at acidic pH and purple at alkaline pH. The reaction products possessed a good stability against light because only a small decrease of A590 nm value was observed under natural light for one month or illumination at 5 000 lx for 6 h. The influorescence intensity of fibroin was obviously decreased after the reaction,suggesting that a drastic change of fibroin conformation happened. The results showed that genipin was cross-linked with some amino acid side chains of fibroin and produced a product with stable color. This study would be helpful for staining silk with natural iridoid compound. Fig 5,Tab 1,Ref 18

Standardization Study on Determination of Polyvinyl Alcohol in Dyeing Wastewater by Boric Acid-Iodine Spectrophotometric Method

Abstract: The determination of Polyvinyl alcohol in Dyeing Wastewater by Boric acid-Iodine Spectrophotometric method was described in this paper.The dosage of color developing reagent,maximum absorption wavelength,time for color reaction,amylum interference and storage time of samples were studied.It was shown that the most suitable wavelength is 645nm and amylum interference can be eliminated by acid and hydrolyzation.The calibration curve of this method shows good linearity,coefficient is 0.99915.

Determination of Chromium (VI) in Water by Ultraviolet Spectrophotometry

Abstract: Chromium (Ⅵ) in water was detected by the UV spectrophotometric method which based on the color reaction of Cr (Ⅵ) with diphenylcarbazide hydrazine to form purple complexes in acidic conditions. The optimized conditions were also studied. The maximum absorption wavelength at 540 nm and the linear range in 5.2×10-3 mg·L-1～1.2×10-1 mg·L-1 which was in accordance with the Beer's law were observed. The results showed that the UV spectrophotometric method was sensitive , simplified and specific and suit for determination of Cr(VI) in natural and waste water.

Spectrophotometric determination of dadmium in Chinese herbs and preparations by the solid phase extraction

Abstract: Objective:Based on synthesis of 2-(2'-quinolinylazo)-4,5-dimethylphenol,the color reaction of 2-(2'-quinolinylazo)-4,5-dimethylphenol with cadmium(Ⅱ)and the solid phase extraction of its colored complex with Waters Porapak Sep-Pak-C18 cartridge,a new method for the determination trace of cadmium(Ⅱ)was studied.Method:The presence of pH=2.5 HCl-potassium hydrogen phthalatebuffer solution.2-(2'-quinolinylazo)-4,5-dimethylphenol can reacts with cadmium(Ⅱ)to form a stable 2∶1 complex.The colored complex can be extracted by C18 cartridge and eluted by ethanol,then can be determined by spectrophotometry.Result:The molar absorptivity of the complex is 4.7×104 L·mol-1·cm-1at 550 nm.Beer's law is obeyed in range of 0-1.5 μg·mL-1.Conclusion:This method can be applied to the determination of cadmium in Chinese herbs.

Determination of Cadmium Ion by Spectrophotometry with 2-(2-thiazolylazo)-5-sulfopropylaminopHenol(TASPAP)

Abstract: The color reaction of a new reagent TASPAP with Cadmium was studied.The results showed that the new reagent TASPAP reacts with Cd(Ⅱ) to form a stable complex in the medium of Clark-Lubs at pH 8.The maximum absorption of this complex is at 550 nm with an apparent molar absorptivity of 3.30×104(L·mol-1·cm-1).Beer's law is obeyed in Cd(Ⅱ) concentration of 0 and 60 μg.The method was applied to determination of Cadmium ion,which shows satisfactory results.

A Simple Method for Measuring Methanol Content in Gas Field Wastewater

Abstract: This paper focuses on the color reaction of chromotrope and formaldehyde, an oxidation product of methanol, with sulfuric acid as the medium, under the existence of phosphoric acid. The generated purple complexes have characteristic absorption peak at wavelength of 570 nm. This reaction principle is applicable to measurement of methanol content in gas field wastewater. It is found there is a linear relationship between methanol content and absorbance while methanol content is within the range of 1~99.0 mg/L. This method has added recovery rate of 97.8~104.5%, detection limit of 1.0 mg/L and relative standard deviation less than 2.9%. The match rate of test results, obtained by this method and gas chromatography respectively, is higher than 95.0%. It is a simple, rapid and accurate method for supervision and management of methanol-containing wastewater in gas fields.