Potentiometric determination of La(III) in polluted water samples using modified screen-printed electrode by self-assembled mercapto compound on silver nanoparticles

• Mercapto compound alone or assembled on silver nanoparticles was used as modifier.
• Two modified screen printed electrodes were constructed.
• The electrodes follow Nernstian behavior and they optimized according to IUPAC recommendation.
• They showed a high selectivity for La(III) ion over many bi or trivalent metal ions and anions.
• They successfully applied for determination of La(III) in real spiked water samples.

A mercapto compound, 3-amino-5-mercapto-1,2,4-triazole (AMT), was self-assembled on silver nanoparticles and used as a modifier to construct a modified screen-printed electrode. The self-assembled ionophore exhibits a high selectivity for lanthanum ion (La(III)), in which the sulfur and nitrogen atoms in their structure play a role as the effective coordination donor sites for the lanthanum ion. The proposed potentiometric method was based on the fabrication of modified sliver nanoparticles-screen-printed electrode (SNPs-MSPE) and modified screen-printed electrode with AMT (MSPE). The sensors have characteristic performance with working concentration range of 1.0 × 10−6–1.0 × 10−2 and 1.0 × 10−8–1.0 × 10−1 mol L−1 and a Nernstian slope of 17.5 ± 0.1 and 20.2 ± 0.1 mV decade−1 of lanthanum ion using MSPE and SNPs-MSPE, respectively. The detection limit was found to be 1.9 × 10−7 and 1.5 × 10−9 mol L−1 and potential response was pH independent across the range of 3.5–8.5 and 3.0–9.5 for MSPE and SNPs-MSPE, respectively. The application of the prepared sensors has been demonstrated for the determination of lanthanum ions in spiked real water samples. The results obtained were compared well with those obtained using inductively coupled plasma atomic absorption spectrometry (ICP-AES).