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.
ABSTRACT
Non-isothermal thermogravimetry in an inert atmosphere was used to investigate the thermal stability of poly(e-caprolactone) (PCL), polylactide (PLA), thermoplastic starch (TPS) and their binary (PCL/PLA,PCL/TPS andPLA/TPS) and ternary (PCL/PLA/TPS) blends. All investigated blends were prepared by Brabender kneading chamber. A two-stage degradation pattern is seen in the case ofPCL, whilePLAexhibits only single stage degradation. On the other hand, the degradation of neat TPS proceeds through three degradation stages. It was found that addition ofPLAaffects the degradation ofPCL/PLAblends indicatingPLA's destabilising effect onPCL. TPS addition thermally destabilizes both,PCLandPLA, but notably thePCLsample. Likewise, that addition of TPS thermally destabilized all investigated ternary blends. The obtained data were used for the kinetic analysis of the degradation process. By using the isoconversional Friedman method and the multivariate nonlinear regression method kinetic analysis was performed. Kinetic analysis revealed the complexity of the thermal degradation process for neat samples and all investigated blends. Kinetic parameters (activation energy, pre-exponential factor and kinetic model) for each degradation stage of neat samples and all investigated blends were calculated.
