Factorial design for optimization of flow-injection preconcentration procedure for copper(II) determination in natural waters, using 2-aminomethylpyridine grafted silica gel as adsorbent and spectrophotometric detection

Abstract

The 2-aminomethylpyridine anchored silica gel (AMPSG) was successfully used as a sorbent in a simple spectrophotometric flow system for Cu²⁺ preconcentration in natural water samples, using sodium diethyldithiocarbamate as chromogenic agent (460 nm). The system was optimized using a full factorial design 2⁵ to determine better analytical conditions to determine copper in the natural water samples such as those from river, tap, stream, spring, well, waste, synthetic brackish water and a water reference material (NIST-1640). The better conditions used were: 180 s loading; 30 s elution; 30 s regeneration of the column; loading flow rate 6.6 mL min⁻¹; buffer solution for the preconcentration and regeneration of the column-acetate buffer pH 5.75; elution flow rate 1.6 mL min⁻¹; eluent composition 0.20 mol L⁻¹ HNO₃. Under these conditions, the preconcentration factor obtained was 77, and the detection limit achieved was 3.0 ng mL⁻¹. The recovery of spiked water samples ranged from 95.2 to 104.7%.

Keywords:

• Copper preconcentration
• 2-Aminomethylpyridine grafted silica gel
• Flow injection
• Spectrophotometry
• Factorial design
• Water samples

Acknowledgements

We are grateful to Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), Fundação de Amparo à pesquisa do Estado de São Paulo (FAPESP), and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support and fellowships.