Non-chromatographic arsenic speciation in algae, rice, and shrimp samples using iron-modified magnetic nanoparticles

Abstract

A new iron oxide magnetic nanomaterial functionalized with organophosphorus compound was used as solid-phase for arsenic speciation in algae, rice and shrimp samples using ICP OES and ICP-MS. The nanoparticles-based arsenic extraction/preconcentration procedure was optimized using chemometric tools. The optimum response was obtained at pH = 4.0, 15 min of extraction time, and 20 mg of nanoparticle mass The rice samples presented total As content between 0.090 and 0.295 µg kg-1 and inorganic As mass fraction between 0.055 and 0.109 µg kg-1. The accuracy for tAs and iAs quantification was verified using CRM NIST 1568b presenting 97% and 101% of recovery, respectively. The method proposed shown satisfactory precision (RSD lower than 15% for all samples), LOD and LOQ (1.08 and 3.70 µg kg-1, respectively, using ICP OES). For algae samples, the arsenic concentration quantified using ICP OES was between 9 and 11 mg kg-1 for tAs and between 0.332 and 0.382 mg kg-1 for iAs,. The accuracy of the proposed method for this matrix was evaluated using ERM CD200 obtaining 105% of recovery. Arsenic speciation analysis using liquid chromatographic coupled with ICP-MS shown that the major arsenic species found in algae are arsenosugars and the values of iAs content were similar to the proposed method using magnetic solid-phase extraction. For shrimp samples, iAs concentrations between 20 and 100 µg kg-1. The proposed method was validated for accuracy using CRMs DOLT-5 and DORM-4 and LC-MS. It was obtained a detection limit of 16.4 ng kg-1 iAs using ICP-MS. The stability of Fe3O4@DTPMP nanoparticles was studied using different batches of Fe3O4@DTPMP nanoparticles production. The recovery of arsenic was statistically similar between the analysis, besides that, it was possible to reuse the same magnetic nanomaterial for 6 successive cycles with recoveries higher than 85% of arsenic. A proposed mechanism of adsorption was studied using FT-IR and XPS analysis with possible interaction between N from modified nanomaterial and O from the arsenic anion. The proposed method is suitable for inorganic speciation of arsenic in several matrices, presenting good accuracy, precision, relatively low cost, and acquittance to green chemistry principles.