Abstract
A series of complexing adsorbents is prepared by coating silica particles with linear polyhexamethylene guanidinium (PHMG) chloride followed by saturation with a number of sulphonated nitrosonaphthols reagents electrostatically retained by positively charged polymer layer. PHMG coated silica is hydrolytically stable even during treatment with 6 M HCl heated up to 50 °C. The adsorption of 1-nitroso-2-naphthol-3,6-disulfonic acid (nitroso-R-salt), 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-N-salt), and 2-nitroso-1-naphthol-3,6-disulfonic acid (nitroso-K-salt) on PHMG modified silica was studied. The effective immobilisation of sulphonated nitrosonaphthols was achieved in the range of pH of 3 - 8, while the adsorption of the monosulphonated reagent (nitroso-N-salt) is twice as high as the disulphonated analogues (nitroso-R-salt and nitroso-K-salt). The adsorption of Cu(II), Fe(III), Co(II), Ni(II), Al(III), Zn(II), Pb(II), Mn(II), and Cr(III) on prepared complexing adsorbents under static and dynamic conditions was studied as a function of time, pH, sample volume, and presence of interfering ions. Metal ions can be desorbed by using 1 M HCl or 1 M HNO3. The preconcentration factors of metals under optimized conditions are varied from 20 to 80. The developed method was used for the preconcentration of trace metals from natural waters followed by ICP-OES determination. The sub-ppb limits of detection of metals are achieved.
Highlights
The determination of metal ions in natural waters at low concentration level remains one of the most important tasks in environmental monitoring
The combined complexing properties are defined by the presence of nitrosonaphthols groups from the electrostatically retained reagents and unshielded guanidinium groups from polyhexamethylene guanidinium (PHMG) layer
According to Thermogravimetric analysis (TGA) data the intermediate product SiO2-PHMG contains 1.36% of loaded PHMG; surface concentration of positively charged guanidinium groups can be estimated as 96 μequiv g−1 for this adsorbent
Summary
The determination of metal ions in natural waters at low concentration level remains one of the most important tasks in environmental monitoring. Group determination of metals at trace level in complex matrices requires sample pretreatment with the purpose of preconcentration of target analytes and/or elimination of undesirable matrix effects. Despite the wide range of adsorbents reported for the preconcentration of trace elements from natural waters, the development of new highly selective adsorbents combining simplicity of synthesis with low-cost of the production remains an important task. The selectivity of the adsorbents to the analytes is primarily determined by the nature of the functional group chemically or noncovalently fixed on the surface of solid matrices [2, 5, 8, 9]
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