Determination of copper in steel by flame atomic absorption spectrometry after separation and enrichment through coprecipitation in Ni- 4-(2-pyridylazo)-resorcinol system

Copper was separated and enriched by coprecipitation in nickel(Ⅱ)- 4-(2-pyridylazo)-resorcinol (PAR) system,then Cu in steel was determined by flame atomic absorption spectrometry (FAAS). The effect of addition amount of coprecipitation reagent PAR, the coprecipitation carrier and its dosage, solution pH and standing time was investigated. The results showed that, Cu in sample could be completely precipitated with Ni²⁺ as coprecipitation carrier after adding 2.0 mL of PAR ethanol solution at pH 4.0. The experiments indicated that, the Cu content in range of 0.1-10.0 μg/mL, was linear to the absorbance with correlation coefficient of r=0.999 9. The detection limit of method was 6.48 μg/L. The proposed method was applied to the analysis of Cu in 35MoVALTiRE (No.8-2) and 35MoVALTiKE (No.8-3) CRMs. The results were consistent with the certified values. The relative standard deviation (RSD, n=6) was 0.69%-0.71%.