Improving the Detection Limit of Anion-Selective Electrodes: An Iodide-Selective Membrane with a Nanomolar Detection Limit

Department of Chemistry & Biochemistry, Auburn University, AUO, Alabama, United States
Analytical Chemistry (Impact Factor: 5.64). 09/2003; 75(15):3865-71. DOI: 10.1021/ac026454r
Source: PubMed


The lower detection limit and the selectivity behavior of anion-selective electrodes (ISEs) are improved by using optimized inner solutions and membrane compositions. With a membrane based on the recently described ionophore [9]mercuracarborand-3, a detection limit of 2 x 10(-9) M has been achieved for iodide. Nevertheless, the improvements are less pronounced than in the case of cation ISEs. This is mainly due to the fact that so far no anion ISE is known with the extremely high selectivities of cation ISEs. If the membrane does not contain an ionophore, leaching of the ion exchanger from the membrane into the sample is also a relevant limiting factor except for ion exchangers of very high lipophilicity.

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    • "Recently, electrodes based on derivatives of vitamin B 12 or on transition metal complexes of porphyrin, phthalocyanine, metallocenes, and Schiff base (Schulthess et al. 1985; Stepanek at al. 1986; Chaniotakis et al. 1988; Daunert and Bachas 1989; Huser et al. 1990; Daunert et al. 1991; Rothmaier and Simon 1993; Gao et al. 1994; Yuan et al. 1993; Shamsipur et al. 2003; Ganjali et al. 2003) have been reported as typical examples of nonconventional carriers with potential response characteristics apparently deviating from the Hofmeister sequence. Due to the outstanding work of the groups of Pretsch, Bakker, Bühlmann, and Meyerhoff, who reported many important theoretical and experimental works with the crucial achievement of improving the low detection limit near nanomolar concentrations, the field of ion-selective electrodes has expanded, especially in the last decades (Bakker et al. 1997; Mi et al. 1999; Malon et al. 2003; Radu et al. 2003). In view of the gradually understood importance of a lipophilic ionic additive (so-called ionic sites) in membrane cocktails, to potentiometric responses of membrane electrodes, the direct incorporation of lipophilic ionic additives into polymer membranes has become a fairly standard practice for anion-selective electrodes, in order to improve the selectivity of the studied electrodes towards the target anion and the response slopes, as well as to provide information of possible response mechanism of the chosen ionophore (Bakker et al. 1994; Steinle et al. 1998; Steinle et al. 2000; Schaller et al. 1994). "
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