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Determination of propyl gallate on carbon paste electrode
Vysoká, Marie ; Zima, Jiří (advisor) ; Fischer, Jan (referee)
Propyl gallate (PG) is a significant synthetic antioxidant and preservative. Its determination has been studied at carbon paste electrode (CPE) using differential pulse voltammetry (DPV) and high performance liquid chromatography with electrochemical detection (HPLC-ED) and with UV spectrometric detection (HPLC-UV). Concentration dependences were measured in the media of Britton-Robinson buffer (pH 5) and methanol (20 %, v/v) by DPV and the limit of detection 0,6110-7 moldm-3 was obtained. Using HPLC with a mobile phase consisting of 0,01 moldm-3 phosphate buffer (pH 4) and methanol (50 %, v/v) with potential of working electrode E = +0,8 V and detection wavelength λ = 280 nm, concentration dependences were measured. Limit of detection was determined to 0,39 moldm-3 for HPLC-ED and 4,95 moldm-3 for HPLC-UV. After verification of the extraction procedure PG was determined in vegetable oil. The resulting value of 3,2 mgkg-1 corresponds with permited limits.
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Determination of synthetic antioxidants using HPLC with electrochemical detection on carbon felt detector
Baroch, Martin ; Dejmková, Hana (advisor) ; Fischer, Jan (referee)
Title: Determination of synthetic antioxidants using HPLC with electrochemical detection on carbon felt detector Author: Martin Baroch Supervisor: RNDr. Hana Dejmková, Ph.D. Department: Department of Analytical Chemistry The aim of this work was to find suitable conditions for HPLC separation with subsequent coulometric detection on a carbon felt detector. The analytes were synthetic phenolic antioxidants, specifically propyl gallate (PG), tert-Butylhydroquinone (tBHQ), butylated hydroxyanisole (BHA) and butylhydroxytoluene (BHT). For the complete separation of the analytes, gradient elution was required. As a mobile phase methanol and acetate-phosphate buffer of pH 4.5 were used. Concentration of methanol in mobile phase was linearly increased from 55 % to 95 % during 8 minutes and next 2 minutes was concentration of methanol held at 95 %. As a stationary phase was used Lichrospher® RP- 18 (125×4 mm, 5 µm) (LichroCART) column. Potentials putted on a carbon-fiber working electrode were 1.40 V for BHT and 0.80 V for other analytes. Two potentials were chosen for a better detector response to BHT. The calibration dependence of the signal on the concentration was observed in the concentration range of · 10-4 - 1 · 10-6 mol dm-3 for all analytes. In this range the dependencies are linear. Inaccurate...
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Determination of propyl gallate on carbon paste electrode
Vysoká, Marie ; Fischer, Jan (referee) ; Zima, Jiří (advisor)
Propyl gallate (PG) is a significant synthetic antioxidant and preservative. Its determination has been studied at carbon paste electrode (CPE) using differential pulse voltammetry (DPV) and high performance liquid chromatography with electrochemical detection (HPLC-ED) and with UV spectrometric detection (HPLC-UV). Concentration dependences were measured in the media of Britton-Robinson buffer (pH 5) and methanol (20 %, v/v) by DPV and the limit of detection 0,6110-7 moldm-3 was obtained. Using HPLC with a mobile phase consisting of 0,01 moldm-3 phosphate buffer (pH 4) and methanol (50 %, v/v) with potential of working electrode E = +0,8 V and detection wavelength λ = 280 nm, concentration dependences were measured. Limit of detection was determined to 0,39 moldm-3 for HPLC-ED and 4,95 moldm-3 for HPLC-UV. After verification of the extraction procedure PG was determined in vegetable oil. The resulting value of 3,2 mgkg-1 corresponds with permited limits.
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Using Voltammetric Method for Monitoring of Antioxidant Content in Biofuels
Tomášková, M. ; Chýlková, J. ; Navrátil, Tomáš ; Šelešovská, R.
The simple and fast method for analysis of Propyl gallate (PG) in biofuels was proposed in this paper. Voltammograms of antioxidant under study were recorded using linear sweep voltammetry method at a gold disc electrode in supporting electrolyte containing 0.18 mol L-1 H2SO4 and 10 % ethanol. For purposes to monitor effects on fuel quality caused by oxidative degradation, the proposed method was applied to samples of biodiesel and Ekodiesel® (the blend of biodiesel with fuel diesel). The analysis of PG can be performed without pretreatment of Ekodiesel samples, and after extraction using distilled water in case of biodiesel samples.
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