Gold nanoparticles (Au NPs) in three different silica based sol–gel matrixes with and without surfactants are prepared. They are characterized by UV–vis absorbance and transmission electron microscopic (TEM) studies. The size and shape of Au NPs varied with the organo-functional group present in the sol–gel matrix. In the presence of mercaptopropyl functionalized organo-silica, large sized (200–280 nm) spherical Au NPs are formed whereas in the presence of aminopropyl functionalized organo-silica small sized (5–15 nm) Au NPs are formed inside the tube like organo-silica. Further, it is found that Au NPs act as efficient catalyst for the reduction of organic dyes. The catalytic rate constant is evaluated from the decrease in absorbance of the dye molecules. Presence of cationic or anionic surfactants greatly influences the catalytic reaction. The other factors like hydrophobicity of the organic dyes, complex formation of the dyes with anionic surfactants, repulsion between dyes and cationic surfactant, adsorption of dyes on the Au NPs also play important role on the reaction rate.

Catalytic reduction of organic dyes at gold nanoparticles impregnated silica materials: influence of functional groups and surfactants

Thermally processed sewage sludge for methylene blue uptake

Targeting ribonucleic acids by toxic small molecules: Structural perturbation and energetics of interaction of phenothiazinium dyes thionine and toluidine blue O to tRNAphe

Sensitive voltammetric responses and mechanistic insights into the determination of residue levels of endosulfan in fresh foodstuffs and raw natural waters

s. (1999). First Internationl Symposium: Amphiphiles at Interfaces-from Structure Control to Properties, Beijing, China. Adamson. A. W. (1990). Physical Chemistry of Surfaces, Wiley, New York. Aguilera, A., Valverde, A., Camacho, F., Boulaid, M., García-Fuentes, L. (2014). Household processing factors of acrinathrin, fipronil, kresoxim-methyl and pyridaben residues in green beans. Food Control, 35, 146-152. Ahad, K., Mohammad, A., Mehboob, F., Sattar, A., Ahmad, I. (2006). Pesticide residues in Rawal Lake, Islamabad, Pakistan. Bull. Environ. Contam. Toxicol., 76, 463-470. Ahmad, I. (2004). Pesticide residues in fortifiied water, soil, food, fruits and vegetable samples in Pakistan. J. Exp. Zool. India, 7, 67-72. Albero, B., Sa ́nchez-Brunete, C., Tadeo J. L. (2003); Determination of endosulfan isomers and endosulfan sulfate in tomato juice by matrix solid-phase dispersion and gas chromatography. J. Chromatogr. A., 1007, 137–143. Ali, Mohammed A., Baugh, Peter J. (2003). Sorption-desorption studies of six pyrethroids and mirex on soils using GC/MS-NICI. International Journal of Environmental Analytical Chemistry, 83, 923-933. Allen, S. J., Mckay, G., Porter, J. F. (2004). Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems. J. Colloid Interface Sci., 280, 322–333. Al-Qodah, Z., Shawaqfeh, A. T., Lafi, W. K. (2007). Two-resistance mass transfer model for the adsorption of the pesticide deltamethrin using acid treated oil shale ash. Adsorption, 13, 73–82. American Medical Association (1997). Educational and Informal strategies to reduce pesticide risks. Preventive Medicine 26, 191-200.

http://prr.hec.gov.pk/jspui/bitstream/123456789/7968/1/Muhammad_Ashraf_Analytical_Chemistry_HSR_UoS_jamshoro_2015_04.08.2017.pdf

Soil adsorption of pesticides used on vegetables in southern Sindh

A simple, selective and sensitive spectrophotometric method is proposed for the determination of widely used organochlorine pesticide endosulfan using thionin and methylene blue as chromogenic reagents. The method is based on the liberation of sulfur dioxide from endosulfan by adding acid reagent and alcoholic potassium hydroxide. The liberated sulfur dioxide is passed through potassium iodate solution and the iodine so liberated bleaches the violet color of thionin and blue color of methylene blue and is measured at 600 nm and 665 nm respectively. This decrease in absorbance is directly proportional to the endosulfan concentration. The Beer’s law is obeyed in the range of 0.4–7.0 and 0.2–9.0 μg mL−1 of endosulfan using thionin and methylene blue as reagents respectively. The molar absorptivity and Sandell’s sensitivity were found to be 1.05 × 105 and 5.03 × 104 L mol−1 cm−1, 3.85 × 10−3 and 8.10 × 10−3 μg cm−2 of endosulfan using thionin and methylene blue as reagents respectively. The method has been applied for the determination of endosulfan in water, soil and vegetables.

Chand Pasha

Papers

Spectrophotometric Determination of Endosulfan Using Thionin and Methylene Blue as Chromogenic Reagents