Multisyringe flow injection analysis hyphenated with liquid core waveguides for the development of cleaner spectroscopic analytical methods: improved determination of chloride in waters

In this work, the hyphenation of the multisyringe flow injection analysis technique with a 100-cm-long pathlength liquid core waveguide has been accomplished. The Cl−/Hg(SCN)2/Fe3+ reaction system for the spectrophotometric determination of chloride (Cl−) in waters was used as chemical model. As a result, this classic analytical methodology has been improved, minimizing dramatically the consumption of reagents, in particular, that of the highly biotoxic chemical Hg(SCN)2. The proposed method features a linear dynamic range composed of two steps between (1) 0.2–2 and (2) 2–8 mg Cl− L−1, thus extended applicability due to on-line sample dilution (up to 400 mg Cl− L−1). It also presents improved limits of detection and quantification of 0.06 and 0.20 mg Cl− L−1, respectively. The coefficient of variation and the injection throughput were 1.3% (n = 10, 2 mg Cl− L−1) and 21 h−1. Furthermore, a very low consumption of reagents per Cl− determination of 0.2 μg Hg(II) and 28 μg Fe3+ has been achieved. The method was successfully applied to the determination of Cl− in different types of water samples. Finally, the proposed system is critically compared from a green analytical chemistry point of view against other flow systems for the same purpose.