differential pulse cathodic stripping voltammetry Dotaz Zobrazit nápovědu
The cyclic voltammetric behavior of minoxidil was studied in a buffer with pH 3. Contradictory to that mentioned in a previously published work, the cyclic voltammogram of minoxidil exhibited a single 2-electron irreversible reduction wave in a buffer with pH 3. This wave was attributed to the reduction of the N›O bond. The cathodic differential pulse wave height decreased on the increase of pH till it disappeared in solution with pH 7.2. The quantitative trace determination of minoxidil was studied at a hanging mercury drop electrode by adsorptive cathodic stripping voltammetry. A fully validated sensitive procedure based on controlled adsorptive accumulation of the drug onto a HMDE was developed for its direct determination. Accumulation of minoxidil was found to be optimized in 0.1 M Britton–Robinson buffer with pH 2.0 as supporting electrolyte under the following conditions: accumulation potential –0.2 V, accumulation time 40 s, scan rate 40 mV s–1 and pulse height 50 mV. The proposed procedure was applied successfully for determination of minoxidil in its topical solution and illegal shampoo and cream. The mean recoveries of the minoxidil were 99.8, 97.8 and 96.7% and with RSD of 0.86, 1.24 and 1.89% in pharmaceutical topical solution, shampoo and cream, respectively.
The optimum conditions were found for the determination of 1,1-dimethyl-3-phenyltriazene in the concentration range from 1 × 10-4 to 1 × 10-7 mol l-1 by differential pulse voltammetry at a hanging mercury drop electrode. The sensitivity of the determination can be improved by preliminary adsorptive accumulation of the substance on the surface of the hanging mercury drop. Differential pulse adsorptive stripping voltammetry can be used for the purpose in the concentration range from 1 × 10-6 to 1 × 10-9 mol l-1. The determination limit is 1 × 10-9 mol l-1 for a deposition time of 10 min, the relative standard deviation being 5% (n = 10) for a concentration of 2 × 10-9 mol l-1.
Differential pulse voltammetry, direct current voltammetry, adsorptive stripping voltammetry and HPLC with electrochemical detection were used for the determination of 5-amino-6-nitroquinoline at a carbon paste electrode. The methods are based either on anodic oxidation or cathodic reduction of this substance, whose electrochemical behavior at carbon paste electrode was further studied by cyclic voltammetry. Practical applicability of these methods was demonstrated on the determination of 5-amino-6-nitroquinoline in model samples of drinking and river water. The detection limit was 2.0 × 10–6 mol l–1 for anodic differential pulse voltammetry in a mixture of Britton–Robinson buffer (pH 11)–methanol 1:1 (v/v) and 1.6 × 10–7 mol l–1 for HPLC with electrochemical detection (E = +1.2 V) in a mobile phase Britton–Robinson buffer (pH 7)–methanol 1:9 (v/v).
Direct current voltammetric (DCV) and differential pulse voltammetric (DPV) determination of antineoplastic agent doxorubicin (DOX) at a carbon paste electrode (CPE) was developed. Britton–Robinson buffer (pH 7.0) was used as a supporting electrolyte. The limits of detection are 8 × 10–7 mol l–1 (DCV) and 6 × 10–8 mol l–1 (DPV). The accumulation of DOX at the electrode surface was used to decrease the limits of detection down to 2.2 × 10–7 mol l–1 for adsorptive stripping DC voltammetry (DCAdSV) and 2.8 × 10–9 mol l–1 for adsorptive stripping differential pulse voltammetry (DPAdSV) at CPE. The results of the voltammetric methods were utilized for the development of a new determination of doxorubicin using HPLC with amperometric detection on CPE based on spherical microparticles of glassy carbon in a wall-jet configuration. A column with chemically bonded C18 stationary phase and a mobile phase containing 0.01 M phosphate buffer (pH 5.0)–methanol 25:75 (v/v) were used. The limit of detection is 4 × 10–7 mol l–1 (HPLC with electrochemical detection (ED)).
The removal of selenium from superficial and waste water is a worldwide problem. The maximum limit according to the World Health Organization (WHO) for the selenium in the water is set at a concentration of 10 μg/L. Carbon based adsorbents have attracted much attention and recently demonstrated promising performance in removal of selenium. In this work, several materials (iron oxide based microparticles and graphene oxides materials) and their composites were prepared to remove Se(IV) from water. The graphene oxides were prepared according to the simplified Hummer's method. In addition, the effect of pH, contact time and initial Se(IV) concentration was tested. An electrochemical method such as the differential pulse cathodic stripping voltammetry was used to determine the residual selenium concentration. From the experimental data, Langmuir adsorption model was used to calculate the maximum adsorption capacity. Graphene oxide particles modified by iron oxide based microparticles was the most promising material for the removal of Se(IV) from its aqueous solution at pH 2.0. Its adsorption efficiency reached more than 90% for a solution with given Se(IV) concentration, meanwhile its maximal recorded adsorption capacity was 18.69 mg/g.
- MeSH
- adsorpce MeSH
- časové faktory MeSH
- chemické látky znečišťující vodu izolace a purifikace MeSH
- elektrochemické techniky metody MeSH
- elektrody MeSH
- grafit chemie MeSH
- koncentrace vodíkových iontů MeSH
- mikrosféry MeSH
- roztoky MeSH
- selen izolace a purifikace MeSH
- statická elektřina MeSH
- teplota MeSH
- velikost částic MeSH
- Publikační typ
- časopisecké články MeSH
The performances of ionic liquid (1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide, IL/CPE) and iron phthalocyanine (IP/CPE) modified carbon paste electrodes in electroanalytical determinations of rutin were evaluated and compared to the performance of unmodified carbon paste electrode (CPE). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), differential pulse adsorptive stripping voltammetry (DPAdSV), and amperometry were used for rutin analysis. The best current responses of rutin were obtained at pH 4.0 for all tested techniques. IL/CPE electrode was found to perform best with DPAdSV technique, where a detection limit (LOD) as low as 5 nmol L(-1) of rutin was found. On the other hand, IP/CPE showed itself to be an optimum choice for DPV technique, where LOD of 80 nmol L(-1) was obtained. Analytical applicability of newly prepared electrodes was demonstrated on determination of rutin in the model samples and the extracts of buckwheat seeds. To find an optimum method for buckwheat seeds extraction, a boiling water extraction (BWE), Soxhlet extraction (SE), pressurized solvent extraction (PSE), and supercritical fluid extraction (SFE) were tested.
- MeSH
- elektrochemie metody MeSH
- elektrody MeSH
- Fagopyrum chemie MeSH
- molekulární struktura MeSH
- rutin chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
