Antioxidant Capacity of Herzegovinian Wildflowers Evaluated by UV-VIS and Cyclic Voltammetry Analysis.

Considering the vast cultural and traditional heritage of the use of aromatic herbs and wildflowers for the treatment of light medical conditions in the Balkans, a comparison of the antioxidant capacity of wildflowers extracts from Herzegovina was studied using both cyclic voltammetry and spectrophotometry. The cyclic voltammograms taken in the potential range between 0 V and 800 mV and scan rate of 100 mV s-1 were used for the quantification of the electrochemical properties of polyphenols present in four aqueous plant extracts. Antioxidant capacity expressed as mmoL of gallic acid equivalents per gram of dried weight of the sample (mmoL GAE g-1 dw) was deduced from the area below the major anodic peaks (Q400 pH 6.0, Q500 pH 4.7, Q600 pH 3.6). The results of electrochemical measurements suggest that the major contributors of antioxidant properties of examined plants are polyphenolic compounds that contain ortho-dihydroxy-phenol or gallate groups. Using Ferric reducing-antioxidant power (FRAP) and 2,2'-azino-bis spectrophotometric methods (3-ethylbenzthiazoline-6-sulphonic acid) radical cation-scavenging activity (ABTS) additionally determined antioxidant capacity. The FRAP results ranged from 2.9702-9.9418 mmoL Fe/g dw, while the results for ABTS assays expressed as Trolox equivalents (TE) ranged from 14.1842-42.6217 mmoL TE/g dw. The Folin-Ciocalteu procedure was applied to determine the total phenolics content (TP). The TP content expressed as Gallic acid equivalents (GAE) ranged from 6.0343-9.472 mmoL GAE/g dw. The measurements of total flavonoid (TF) and total condensed tannin (TT) contents were also performed to obtain a broader polyphenolic profile of tested plant materials. Origanum vulgare L. scored the highest on each test, with the exception of TT content, followed by the Mentha × piperita L., Artemisia annua L., and Artemisia absinthium L., respectively. The highest TT content, expressed as mg of (-)catechin equivalents per gram of dried weight of sample (mg CE/g dw), was achieved with A. absinthium extract (119.230 mg CE/g dw) followed by O. vulgare (90.384 mg CE/g dw), A. annua (86.538 mg CE/g dw) and M. piperita (69.231 mg CE/g dw), respectively. In addition, a very good correlation between electrochemical and spectroscopic methods was achieved.

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

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.