Performance of Avocado Seed Activated Carbon as Adsorbent for Highly Sensitive Determination of Cd Using a Flow Injection System Online Coupled to TS-FF-AAS

A flow-injection preconcentration system using detection by the thermospray flame furnace atomic absorption spectrometry (FIA-TS-FF-AAS) is proposed. Cd2+ are adsorbed on avocado seed activated carbon (ASAC) packed into a cylindrical mini-column and eluted using HCl solutions for the detection system. A 2(5) - 1 fractional factorial and Doehlert matrix design were employed to determine the optimum conditions for cadmium preconcentration (pH 7.68, buffer concentration (Tris/Tris-HCl) of 0.023 mol L-1, eluent concentration (HCl) of 2.0 mol L-1, the adsorbent mass of 100.0 mg and preconcentration flow rate of 4.8 mL min(-1)). The preconcentration method presents linearity within the range of 0.41-15.00 mu g L-1, limits of quantification and detection of 0.41 and 0.12 mu g L-1, respectively, preconcentration factor of 10.7, consumption of index of 0.93 mL and sample throughput of 26 h(-1). The precision assessed as the relative standard deviation (RSD) were found to be 0.48, 0.90 and 2.30% for inter-day precision (n = 2), and 0.30, 0.44 and 2.48% for intra-day precision (n = 6) for respective cadmium concentration of 0.50, 5.00 and 15.00 mu g L-1. The proposed method was applied satisfactorily in samples of cigarette (62.84 +/- 11.28 mu g kg(-1)), human hair (69.61 +/- 2.38 mu g kg(-1)) and water samples [lake (0.65 +/- 0.01 mu g L-1), tap and mineral].