Abstract
A bi-parametric sequential injection method for the determination of copper(II) and zinc(II) when present together in aqueous samples was developed. This was achieved by using a non-specific colorimetric reagent (4-(2-pyridylazo)resorcinol, PAR) together with two ion-exchange polymeric materials to discriminate between the two metal ions. A polymer inclusion membrane (PIM) and a chelating resin (Chelex 100) were the chosen materials to retain zinc(II) and copper(II), respectively. The influence of the flow system parameters, such as composition of the reagent solutions, flow rates and standard/sample volume, on the method sensitivity were studied. The interference of several common metal ions was assessed, and no significant interferences were observed (<10% signal deviation). The limits of detection were 3.1 and 5.6 µg L−1 for copper(II) and zinc(II), respectively; the dynamic working range was from 10 to 40 µg L−1 for both analytes. The newly developed sequential injection analysis (SIA) system was applied to natural waters and soil leachates, and the results were in agreement with those obtained with the reference procedure.
Highlights
Sample preparation is considered an essential part of the analytical process
Two different colorimetric reagents for metal ions, namely PAR and 1-(2-pyridylazo)-2-naphthol (PAN), were initially studied via wet/bench chemistry, to determine which would be more advantageous for the spectrophotometric quantification of both Cu(II) and Zn(II)
By assessing the wavelength of maximum absorption of both metal complexes, it was observed that the signal was higher for the metal–PAR complexes, PAR was chosen as the metal indicator to develop the sequential injection analysis (SIA) method
Summary
Sample preparation is considered an essential part of the analytical process. Some of the most commonly used sample pre-treatment methods are extraction techniques, namely solid-phase extraction (SPE), liquid–liquid extraction (LLE) and, more recently, membrane-based extraction techniques, among others [1].The basic principles of both SPE and LLE can involve adsorption, partition or ion-exchange of solutes between the two different phases. In SPE, this occurs between a liquid phase (i.e., aqueous sample) and a solid phase (e.g., sorbent material), while, in LLE, this occurs between two immiscible liquid phases [2,3,4,5]. In recent years, these techniques have been evolving towards their miniaturization (i.e., solid-phase/liquid-phase microextraction), and different types of membranes have been used as a support for organic phase in the microextraction process [1].
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