Stable Azo Dye Research Articles

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

We have examined the kinetics and mechanism of the dediazoniation reaction of p-methylbenzenediazonium tetrafluoroborate in the presence and absence of CuCl2 using a methodology developed by us that allows, simultaneously, and within the same experiment to identify, to quantify, and to obtain the rate constants for the formation of all dediazoniation products, and, indirectly, the rate constant for the diazonium salt decomposition. The methodology developed combines the use of coupling reactions, to form a stable azo dye, followed by analysis by HPLC. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 31–39, 1998.

96/06233 Performance analysis of photovoltaic thermal air heaters

The photodegradation of two common and very stable azo-dyes, i.e. methyl-orange (C14H14N3SO3Na) and orange II (C16H11N2SO4Na), is reported. The photocatalytic oxidation was carried out in aqueous suspensions of polycrystalline TiO2 irradiated by sunlight. Compound parabolic collectors, installed at the “Plataforma Solar de Almerı́a” (PSA, Spain) were used as the photoreactors and two identical reacting systems allowed to perform photoreactivity runs for the two dyes at the same time and under the same irradiation conditions. The disappearance of colour and substrates together with the abatement of total organic carbon content was monitored. The main sulfonate-containing intermediates were found to be in lower number in respect to those obtained under artificial irradiation. In particular there were no more evidence of the presence of hydroxylated transients. The dependence of dye photooxidation rate on: (i) substrate concentration; (ii) catalyst amount; and (iii) initial pH was investigated. The influence of the presence of strong oxidant species (H2O2, S2O82−) and some ions (Cl−, SO42−) on the process was also studied.

Diazotised sulphanilic acid as a spectrophotometric reagent for the determination of trace amounts of indole in aqueous solution

A spectrophotometric method for the determination of trace amounts of indole in aqueous solution is described. The method is based on the coupling reaction of the determinand with diazotised sulphanilic acid to form, in an acidic medium, an intense yellow, water-soluble, stable azo dye, which shows maximum absorption at 445 nm. The graph of absorbance versus concentration in linear, indicating that Beer's law is obeyed over the range 30–90 µg of indole in a final volume of 25 ml, i.e., 1.2–3.6 p.p.m., with a molar absorptivity of 33.4 × 103 l mol–1 cm–1, a sensitivity index of 0.0035 µg cm–2, a relative error of 0 to –1.6% and a relative standard deviation of 0.2–1.9%, depending on the determinand concentration. The optimum reaction conditions and interferences from foreign organic compounds have been investigated.

Spectrophotometric Determination of 8-Hydroxyquinoline (Oxine) in Aqueous Solution by Azo Dye Formation with Diazotizedp-Aminoacetophenone

Abstract A sensitive spectrophotometric method for the determination of oxine in aqueous solution is investigated. It is based on the reaction of the analyte with diazotized p-aminoacetophenone to form, in the presence of sodium hydroxide, an intense cherry-red water-soluble and stable azo dye which shows maximum absorption at 520 nm. The linear absorbance plot with the concentration indicates that Beer's law is adhered over the range 10–100μg of oxine in a final volume of 25 ml, i.e., 0.4–4 ppm, with a molar absorptivity of 3.37 × 104 1mol−1 cm−1, a relative error of +0.44 to –1.12%, and a relative standard deviation of 0.54–2.9%, depending on the level of analyte concentration. The optimum conditions affecting the color reaction and interference due to foreign organic compounds have been examined.

Spectrophotometric Determination of Nitrite in Aqueous Solution by the Diazotization-Coupling Method with Orthanilic Acid-Resorcinol

Abstract A spectrophotometric method for the determination of nitrite is described. It relies upon the reaction of this ion with an acidified orthanilic acid solution to form a diazonium ion, which is subsequently coupled with resorcinol, in alkaline medium, to form immediately a yellow-colored stable water-soluble and intense azo dye having maximum absorption at 426 nm. The linear absorbance plot with concentration indicates that Beer's law is obeyed over the range of 1-12 μg of nitrite in a final volume of 10ml, with a molar absorptivity of 38.7 × 1031 mol−1cm−1, sensitivity index of 0.0012μgcm−3, relative error of –0.5 to +0.2% and relative standard deviation of 0.43-3.5%, depending on the concentration level. The optimum conditions affecting and related to the color reaction and interference due to foreign ions have been studied.