Development of a flow injection method with amperometric detection for the indirect determination of copper in drinking water samples

Abstract

A gas-diffusion flow injection method with amperometric detection for the indirect determination of copper on a silver electrode was developed. The flow through system was equipped with two injection valves and a gas-diffusion unit. In the first step, a signal of a cyanide solution was recorded. In the subsequent step, the signal of cyanide in the presence of copper was measured. Interferences (Cd(II), Co(II), Ag(I), Ni(II), Fe(III), Hg(II) and Zn(II)) were investigated and successfully removed. The calibration graph was linear in the range 1-90 mu mol dm(-3) of copper with a correlation coefficient of 0.993. The regression equation is I = (0.0455 +/- 0.0015)c + (0.4611 +/- 0.0671), where I is the relative signal decrease in mu A and c is concentration in mu mol dm(-3). Relative standard deviation for six consecutive injections of 30 mu mol dm(-3) copper(II) was 1.47 % and for 1 mu mol dm(-3) copper(II), it was 3.40 %. The detection limit, calculated as 3 s/m (where s is a standard deviation of nine measurement of a reagent blank and m is the slope of the calibration curve), was 0.32 mu mol dm(-3), which corresponds to 2.44 ng of copper(II) (the loop volume was 0.12 cm(3)). The method enables 60 analyses per hour and it was successfully applied for the determination of copper in drinking water samples.

Cilj ovog rada bio je razvoj gasno-difuzione protočno injekcione metode sa amperometrijskom detekcijom za indirektno određivanje bakra na srebrnoj elektrodi. Protočni sistem je opremljen sa dva injekciona ventila i gasno-difuzionom jedinicom. U prvom koraku snima se signal rastvora cijanida, a u drugom snima se signal pri istovremenom ubrizgavanju rastvora cijanida i rastvora bakra. Smetnje od Cd(II), Co(II), Ag(I), Ni(II), Fe(III), Hg(II) i Zn(II) su ispitane i uspešno uklonjene. Kalibraciona kriva je linearna u opsegu 1-90 μmol dm-3 bakra, koeficijent korelacije je 0,993, a jednačina prave I = (0,0455±0,0015)c + (0,4611±0,0671), gde je I razlika visine signala u μA, a c je koncentracija u μmol dm-3. Relativna standardna devijacija za šest uzastopnih ubrizgavanja rastvora bakra koncentracije 30 μmol dm-3 je 1,47 %, a za 1 μmol dm-3 rastvor Cu(II) je 3,40 %. Limit detekcije, izračunat kao 3s/m (gde je s standardna devijacija devet merenja slepe probe i m je nagib kalibracione prave), je 0,32 μmol dm-3, što odgovara 2,44 ng Cu(II) (zapremina petlje za uzorak je 0,12 cm3). Metoda omogućava 60 analiza po jednom satu i uspešno je primenjena za određivanje bakra u pijaćoj vodi.