Silica sequentially modified with polyhexamethylene guanidine and Arsenazo I for preconcentration and ICP–OES determination of metals in natural waters

• A new sorbent based on sequentially modified silica with polyhexamethylene guanidine and Arsenazo I has been prepared.
• A procedure for sorption-ICP–OES determination of metal ions in natural waters is proposed.
• LOD of the method is 0.03–0.44 μg/L.

Silica based sorbent sequentially modified with polyhexamethylene guanidine and 2-(1,8-dihydroxy-3,6-disulfo-2-naphthylazo)benzenearsonic acid (Arsenazo I) was developed and studied in the present work. Conditions for immobilizing Arsenazo I on the aminated silica surface were studied: optimal equilibration time was 10 min, and a maximum reagent extraction was achieved between pHs 4 and 7. The stability of the sorbent in highly saline and weakly acidic solutions was examined: it was found that the reagent had not been desorbed from the surface by treatment with dilute solutions of HNO3 and NaCl solutions up to a concentration of 10 g/L. Maximum recovery of Al(III), Ca(II), Cd(II), Co(II), Cu(II), Fe(II), Fe(III), Mg(II), Ni(II), Pb(II), and Sr(II) was observed in the pH range of 5–7. Metals were desorbed from the surface with 1 M HNO3. Sorption-inductively coupled plasma optical emission method for the determination of metal ions had been developed, including group sorption preconcentration of metal ions from aqueous solutions at pH 7 in the hydrocarbonate buffer medium, their desorption with 1 M HNO3, and inductively coupled plasma optical emission determination. The proposed method was used to determine metal concentration in river waters of Krasnoyarsk Krai.