In this work, a new double-reactor method for the analysis and speciation of trace amounts of
Cr(III)/Cr(VI) ions in environmental samples has been developed combining on-line magnetic solid
phase extraction (MSPE) with inductively coupled plasma optical emission spectrometry (ICP OES).
For the preconcentration and speciation of Cr, a new magnetic graphene oxide (MGO)
functionalized with p-sulfanilic acid has been syhthesized. This material presents good capacity of
adsorption towards Cr(III) and Cr(VI) species. The FI manifold used for on-line preconcentration
and elution is shown in Fig.1. The eight-port valve (V) was changed from position A-B, and vice versa
allowing the load of sample of the two reactors (R1 and R2) followed of the elution of Cr(VI) with
NH3 3.2 % in R1 and total Cr with HNO3 2.3 % in R2 to ICP-OES. Subtracting the signal of Cr (VI) to
the signal of Cr(III)+Cr(VI), both ions can be determined. Moreover, several flow and chemical
variables were optimized by two multivariate central composite designs (CCD). The optimized
method offers good sensitivity and precision. The accuracy of the proposed method was verified
using certified reference materials. The obtained results were in good agreement with the certified
values and high recoveries were achieved for the spiked samples. Thus, the new adsorbent has
demonstrated to be useful for the preconcentration and speciation of Cr(III)/Cr(VI).
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