Potentiometric Response of Solid-State Sensors Based on Ferric Phosphate for Iron(III) Determination

Abstract

A novel ion-selective electrode with membranes based on iron(III) phosphate and silver sulfide integrated into a completely new electrode body design has been developed for the determination of iron(III) cations. The best response characteristics with linear potential change were found in the iron(III) concentration range from 3.97× 10−5 to 10−2 mol L−1. The detection limit was found to be 2.41× 10−5 mol L−1 with a slope of –20.53 ± 0.63 and regression coefficient of 0.9925, while the quantification limit was 3.97× 10−5 M. The potential change per concentration decade ranged from –13.59 ± 0.54 to –20.53 ± 1.56 for Electrode Body 1 (EB1) and from –17.28 ± 1.04 to –24 ± 1.87 for Electrode Body 2 (EB2), which is presented for the first time in this work. The prepared electrode has a long lifetime and the ability to detect changes in the concentration of iron cations within 20 s. Membrane M1 showed high recoveries in the determination of iron cations in iron(III) standard solutions (98.2–101.2%) as well as in two different pharmaceuticals (98.6–106.5%). This proves that this type of sensor is applicable in the determination of ferric cations in unknown samples, and the fact that all sensor parts are completely manufactured in our laboratory proves the simplicity of the method.

The New Ion-Selective Electrodes Developed for Ferric Cations Determination, Modified with Synthesized Al and Fe−Based Nanoparticles

“…Merck, KGaA, Darmstadt, Germany), while pH value 5 with acetic buffer prepared by mixing sodium acetate (CH 3 COONa, p.a., Kemika, Zagreb, Croatia) and acetic acid (CH 3 COOH, p.a., VWR chemicals, Radnor, PA, USA). As it was reported before, membranes with FePO 4 , Ag 2 S, and PTFE composition showed the best response at pH = 1 [ 40 ], and ferric selective electrodes modified with nanoparticles of iron oxides showed the best response at pH = 5 [ 20 ]. The tests were carried out at RT.…”

“…The main components of the ion-selective electrode presented in this work, i.e., ferric phosphate (FePO 4 ), silver sulfide (Ag 2 S) and 4 different types of NPs, were preproduced or synthesized in our laboratory. The procedure for the preparation of FePO 4 , and Ag 2 S was described in detail in previous work [ 40 ]. The FePO 4 , Ag 2 S, Al, and Fe-based NPs, polytetrafluoroethylene (PTFE, p.a.)…”

“…Once the membrane was prepared, it was inserted into the electrode body and ultimately tested. The electrode body used in this work and represented in [ 40 ] was made of an epoxy plate with the cooper layer responsible for charge transfer between the membrane and cable connected to the millivoltmeter. Contact between the membrane and the copper layer was ensured with a conductive graphite adhesive.…”

“…In this work, we investigate which type of NPs is the best suited to improve the detection properties of the ion-selective electrode for iron(III) cations. The miniaturized electrode based on the ferric phosphate (FePO 4 ), Ag 2 S, and PTFE described in previous work [ 40 ] was modified with the hematite, magnetite, boehmite, and alumina oxide NPs, and their influence on the detection limit and sensitivity of the electrode was studied. Ferric-selective electrodes constructed from sparingly soluble salts that had been reported before showed linearity (1∙10 −5 – 1∙10 −2 ) mol L −1 [ 38 , 39 ] with a limit of detection of 5.1∙10 −6 mol L −1 [ 38 ].…”

Potenciometrijski senzori za određivanje željezovih(III) kationa

“…Idealan nagib kalibracijske krivulje za trovalentne katione tako iznosi ≈ −19,73 mV dec −1 . Za senzore opisane u literaturnim izvorima 4,[28][29][30][31][32][33]38,39 očita je visoka, gotovo idealna osjetljivost, dok senzori 26,[34][35][36] pokazuju super Nernstov i senzor 37 supra Nernstov odziv. Kao što je već spomenuto, očekivana vrijednost granice detekcije za potenciometrijske senzore je reda veličine 10 −6 te je iz podataka u tablici 1 očito da ih većina i zadovoljava očekivanja, dok su iznimne vrijednosti granice detekcije od 1 • 10 −9 mol l −1 dosegli Yari i sur.…”