Determination of trace metals by ICP-OES in plant materials after preconcentration of 1,10-phenanthroline complexes on activated carbon

Abstract

In this work, 1,10-phenanthroline was used as a complexing agent for the separation and preconcentration of Cd(II), Co(II), Ni(II), Cu(II) and Pb(II) on activated carbon. The metals were adsorbed on activated carbon by two methods: static (1) and dynamic (2). The optimal condition for separation and quantitative preconcentration of metal ions with activated carbon for the proposed methods was for (1) in the static methods in the pH range 7-9. The desorption was found quantitative with 8mol dm(-3) HNO(3) for Cd(II) (92.6%), Co(II) (95.6%), Pb(II) (91.0%), and with 3mol dm(-3) HNO(3) for Cd(II) (95.4%), Pb(II) (100.2%). The preconcentration factor was 100 with R.S.D. values between 1.0 and 2.9%. For (2), the dynamic method (SPE), the pH range for the quantitative sorption was 7-9. The desorption was found quantitative with 8mol dm(-3) HNO(3) for Cd(II) (100.6%), Pb(II) (94.4%), and reasonably high recovery for Co(II) (83%), Cu(II) (88%). The optimum flow rate of metal ions solution for quantitative sorption of metals with 1,10-phenanthroline was 1-2cm(3)min(-1) whereas for desorption it was 1cm(3)min(-1). The preconcentration factor was 50 for all the ions of the metals with R.S.D. values between 2.9 and 9.8%. The samples of the activated carbon with the adsorbed trace metals can be determined by ICP-OES after mineralization by means of a high-pressure microwave mineralizer. The proposed method provides recovery for Cd (100.8%), Co (97.2%), Cu (94.6%), Ni (99.6%) and Pb (100.0%) with R.S.D. values between 1.2 and 3.2%. The preconcentration procedure showed a linear calibration curve within the concentration range 0.1-1.5microg cm(-3). The limits of detection values (defined as "blank+3s" where s is standard deviation of the blank determination) are 5.8, 70.8, 6.7, 24.6, and 10.8microg dm(-3) for Cd(II), Pb(II), Co(II), Ni(II) and Cu(II), respectively, and corresponding limit of quantification (blank+10s) values were 13.5, 151.3, 20.0, 58.9 and 33.2microg dm(-3), respectively. As a result, these simple methods were applied for the determination of the above-mentioned metals in reference materials and in samples of plant material.