Increased Sensitivity Spectrophotometric Flow Analysis Method for Copper Determination in Water Samples

Abstract

A reverse configured flow injection system was developed for the determination of copper in water samples. In this study, a bathocuproine disulfonic acid copper complexing reagent was used. In the presence of a reducing agent (hydroxylamine), the formation of complex was monitored at 484 nm. The determination range extended from 1 to 40 µg L⁻¹, with an applicable determination rate of 40 h⁻¹. The developed method was applied to the determination of copper in water samples (estuarine, river, and drinking water) and showed good accuracy (z-score below 2). The detection limit of 0.7 µg L⁻¹ copper is consistent with the requirement of the target water samples. The developed method was also used for the comparison of different spectrophotometric flow cells. Alternative flow cells (U, Z shaped, and the liquid waveguide capillary cell) were compared in terms of their sensitivity and response to refractive index changes.

Keywords:

• Copper determination
• Increased path-length flow cell
• Liquid-core waveguide capillary cell
• Reverse flow injection analysis
• Visible spectrophotometry

Acknowledgments

I. V. Tóth thanks Fundo Social Europeu (FSE) and Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) for the financial support through the POPH-QREN program. The authors also thank to Fundação para a Ciência e a Tecnologia (FCT, Portugal) for financial support through national funds on project PEst-C/EQB/LA0006/2011.

Notes

^a according to Ruzicka and Hansen (1988).

^a Values within brackets correspond to the limits of the 95% confidence intervals for the estimated regression parameters (4 different standard solutions in the range between 2 to 20 µg L⁻¹of Cu, injected in triplicate).

^a Values in parentheses correspond to the standard deviation of the estimated equation parameters from three consecutive working days.

^a mean and standard deviation (n = 3).

^b assessed based on a calibration curve performed using standard solutions with 15 g L⁻¹ NaCl.