Determination of inorganic arsenic in natural waters after selective extraction using Moringa oleífera seeds

Moringa oleifera seeds were used as a biosorbent for the selective extraction of inorganic arsenic in water and detection by furnace graphite atomic absorption spectrometry. The behavior of the As(III) and As(V) adsorption onto the biosorbent was evaluated at pH 1.0-9.0 in batch studies. The results indicated that As(III) was adsorbed at pH 7.0 while As(V) was poorly retained. So much, in a sample contained As(III) and As(V), the As(III) is going to be retained while most pentavalent species remained free in solution, allowing their determination by GF AAS. The operational variables of the separation method were optimized, the adsorbent mass of 1.0 g was found to be sufficient to retain the As(III) present in the solutions with a stirring time of 1 h. The limit of detection for As(V) determination is 6.3 μg L−1 and the precision was below 1.23%. Results for recovery tests using different water samples were higher than 92% As(V). The accuracy of the method was proven through the analysis of a certified water sample (APS 1071).