Sequential injection trace determination of iron in natural waters using a long-pathlength liquid core waveguide and different spectrophotometric chemistries

We developed a sequential injection analysis (SIA) method for the determination of iron in coastal, ground, and surface fresh waters using two different reagents (ferrozine and 1,10-phenathroline). The methodology uses a double-line SIA system to improve mixing conditions between sample and reagent solutions. A liquid waveguide capillary cell (LWCC) with 1.0 m pathlength, 550 μm i.d., and 250 μL internal volume was used to enhance the sensitivity of the determination. The detection limits for the ferrozine and 1,10-phenanthroline reagent were 0.15 and 0.35 μg L–1, respectively. The system provides a linear response up to 20 μg L–1 and has a high throughput rate (41 h–1), low reagent consumption, and also low effluent production for both reagents. The developed method was applied to natural waters (river, well, ground, potable, and sea waters) and one reference water sample. *Corresponding author: E-mail: [email protected] Acknowledgments The authors thank Fundação para a Ciência e a Tecnologia (FCT) for financial support through Project PTDC/AMB/64441/2006. Ricardo Páscoa and Ildikó Tóth acknowledge financial support from FCT and FSE (III Quadro Comunitário) through the grants SFRH/BD/30621/2006 and SFRH/BPD/5631/2001, respectively. physical, chemical, and biological processes involved (Hanrahan et al. 2002). In the case of iron analysis in seawaters, matrix effects and low concentration levels are the main difficulties. To overcome these difficulties and to increase the sensitivity, separation and/or preconcentration of the analyte is often necessary (Lohan et al. 2005) in spectrophotometric