Preparation of chitosan-coated polystyrene microspheres for the analysis of trace Pb(ii) ions in salt by GF-AAS assisted with solid-phase extraction

The content of heavy metals is an important index to measure the quality and safety of salt. However, due to the high content of Na(i) in salt causing a large background interference, it is difficult to accurately analyze trace Pb(ii) through the existing atomic absorption spectrometry. Therefore, it is of great significance to design a new solid-phase extraction (SPE) material for the removal and determination of Pb(ii) from salt. Herein, using polystyrene microspheres as carriers, the chitosan-coated polystyrene SPE fillers PS@SO3H@G-CTS were synthesized by sulfonating with sulfonyl chloride, coating with chitosan and crosslinking with glutaraldehyde successively. The structure was characterized by elemental analysis, FT-IR, SEM, XRD and thermal stability. The SPE column prepared by PS@SO3H@G-CTS was used for the adsorption of heavy metal Pb(ii) in salt, with 0.1 mol L-1 of HCl as Na(i) eluent and 2 mmol L-1 of EDTA-2Na as Pb(ii) eluent. The salt concentration below 0.03 g mL-1 could better reflect the performance of column, with the recovery rate of 101.17-106.45% by standard addition. The PS@SO3H@G-CTS fillers could remove Na(i) under certain salt concentration, so as to accurately determine Pb(ii) in the actual sample. Their adsorbability was undisturbed by common anions and low concentration of cations.