Solid phase extraction and a spectrophotometric method for the determination of trace amounts of gold with 4-rhodanineazo benzoic acid

摘要

У раду je описана синтеза и примена 4-роданиназо-бензоеве (4-БАРА) киселине као но-вог хромогеног реагенса. Високо осет(Jb)ива, селективна и брза метода за одре(n)ива(нь)е злата базирана je на реакц(иj)и са 4-БАРА и екстракц(иj)и o6ojeнor комплекса на Clean-up~® С_5 колони реверсних фаза. У присуству 0,02-0,2 mol/L раствора фосфорне киселине и полиокси-ети-леннонилфенил етра (emulsifier-OP) 4-БАРА формира са златом комплекс у стехиометриj-ском односу 2:1. После copпциje на колони комплекс се елуира етанолом, са фактором кон-центриса(нь)а 50. У етанолу, коефициjент моларне апсорпциjе комплекса износи 2,39×10~5 L mol~(-1) cm~(-1) на 505 nm. Зависнос апсорбанциjе од концентрациjе следи Веег-ов закон у опсегу ～0,01-～1,2 μg/mL. Релативна стандардна девиjациjа на концентрационом нивоу од 0,001 μg/mL износи 2,3 %, а границе детекциjе у оргиналном узорку 8,0×10~(-5)μg/mL. Метода je успешно приме(нь)ена за одре(n)ива(нь)е злата у узорцима руда.%The synthesis and application of 4-rhodanineazo benzoic acid (4--BARA) as a new chromogenic reagent for the determination of gold is described. A highly sensitive, selective, and fast method for the determination of gold based on its rapid reaction with 4-rhodanineazo benzoic acid and the solid phase extraction of the colored complex on a reversed phase Clean-up~®- C_5 cartridge was developed. In the presence of 0.02-0.2 mol/L phosphoric acid solution and a polyoxyethylene nonylphenol ether (emulsifier-OP) medium, 4-rhodanineazo benzoic acid reacted with gold to form a colored complex with a gold-to-4-BARA molar ratio of 1:2. The complex was enriched by solid phase extraction with a reversed phase Clean-up~® C_5 cartridge. The complex was eluted from the cartridge with ethanol and an enrichment factor of 50 was achieved. In ethanol medium, the molar absorptivity of the complex was 2.39×10~5 L mol~(-1) cm~(-1) at 505 nm. The Beer Law was obeyed in the concentration range 0.01-1.2 μg/mL. The relative standard deviation for eleven replicate samples at the 0.001 ug/mL level was 2.3 %. In the original sample, the detection limit was 8.0×10~(-5)μg/mL. This method was applied to the determination of trace amounts of gold in ore samples with good result.