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Featured researches published by Martin Adam.


Central European Journal of Chemistry | 2010

Comparison of pressurised fluid and ultrasonic extraction methods for analysis of plant antioxidants and their antioxidant capacity

Petr Dobiáš; Petra Pavlíková; Martin Adam; Aleš Eisner; Blanka Beňová; Karel Ventura

The analytical method based on the high-performance liquid chromatography coupled with UV detection (HPLC/UV) for determination of selected antioxidants (i.e., esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Pressurised fluid extraction (PFE) and ultrasonic extraction (USE) methods for the isolation of these compounds from ten real plant samples were used. Both extraction methods were optimised and compared to each other. For the proposed HPLC/UV method the LOQ values (limit of quantification) in the range from 22.7 (xanthotoxin) to 97.2 ng mL−1 (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also determined. Results ranged from 82.04 to 94.43% of DPPH radical inhibition for PFE method and from 76.01 to 89.94% in the case of USE method.


Journal of Separation Science | 2009

Extraction of antioxidants from plants using ultrasonic methods and their antioxidant capacity

Martin Adam; Petr Dobiáš; Aleš Eisner; Karel Ventura

The analytical method based on the HPLC coupled with UV detection (HPLC-UV) for the determination of selected antioxidants (i.e. esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Two ultrasonic extraction methods for the isolation of these compounds from the plants such as Mentha longifolia L., Mentha spicata L., Ruta graveolens L., Achyllea millefolium L., Plantago lanceolata L. and Coriandrum sativum L. were used. Both of these methods, i.e. ultrasonic probe and ultrasonic bath, were optimised and compared to each other. For the proposed HPLC-UV method LOQ values in the range from 22.7 (xanthotoxin) up to 97.2 ng/mL (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was also determined. Obtained results ranged from 10.11 up to 73.50% of DPPH radical inhibition.


Journal of Separation Science | 2008

Analysis of selected stilbenes in Polygonum cuspidatum by HPLC coupled with CoulArray detection.

Blanka Beňová; Martin Adam; Kateřina Onderková; Josef Královský; Milan Krajíček

The roots of three varieties of Polygonum cuspidatum were analyzed for resveratrol and its analogs. The powder of the dried roots was extracted with aqueous ethanol (60% v/v) and the extracts obtained were analyzed using RP HPLC with coulometric detection. A simple HPLC method with a multichannel CoulArray detector was developed for the determination of four stilbenes: resveratrol, its glucoside piceid, piceatannol, and its glucoside astringin. Analyses were carried out on a LiChrospher C18 (125 x 4.6 mm id, particle size 5 microm) column with a mobile phase of ammonium acetate (pH 3) and ACN in gradient mode. Four compounds were monitored by a CoulArray electrochemical detector. Potentials of eight electrochemical cells in series were set in the range of 200-900 mV. Optimization of the mobile phase pH was performed. Calibration curves showed good linearity with correlation coefficients (r(2))--more than 0.9975.


Food Chemistry | 2012

Microextraction by packed sorbent (MEPS) as a suitable selective method for L-ascorbic acid determination in beverages

Martin Adam; Petra Pavlíková; Andrea Čížková; Petra Bajerová; Karel Ventura

In this study the modern microextraction by packed sorbent (MEPS) method followed by HPLC-UV analysis was optimised and evaluated for determination of l-ascorbic acid (AA) content in beverages. In this case 300μL of sample was passed through silica BIN (barrel insert and needle assembly) and entrapped AA was eluted by 60μL of methanol-water (10%, v/v) solution. Recovery of the proposed method for three concentration levels ranged between 97.46% and 106.88% with relative standard deviation 8.7% (low conc.), 2.49% (medium conc.) and 1.98% (high). Obtained results of AA contents in real samples were in the ranges 56.5-195.4μg/mL and 130.4-1090.0μg/mL for ice-tea and fruit juice samples, respectively. Proposed method was compared with iodometric titration and DPPH methods, but microextraction method was found to be more selective for AA determination in tested samples.


Journal of Separation Science | 2014

Comparison of various techniques for the extraction and determination of antioxidants in plants.

Petra Bajerová; Martin Adam; Tomáš Bajer; Karel Ventura

The following extraction techniques have been used for extracting antioxidants (apigenin, coumarin, esculetin, umbelliferone, bergapten, quercetin, rutin, scopoletin and xanthotoxin) from plant material: supercritical fluid extraction, pressurized liquid extraction, extraction by means of Soxhlet apparatus, ultrasonic extraction in ultrasonic bath, and by means of ultrasonic probe. The analytical method based on HPLC-UV detection for the determination of selected antioxidants was developed. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical was also determined. Comparing all results the ultrasonic probe method using 0.75 g of sample extracted by 50 mL of acetonitrile in water (30%, v/v) for 25 min at room temperature and with amplitude at 60% (equal to 90 W) without pulsation was evaluated as the best tool. The most significant indicator demonstrating this statement is the antioxidant capacity expressed as gallic acid equivalent where the ultrasonic probe method showed the best results in 10 of 16 samples. Also the operability of ultrasonic probe extraction method compared to other tested methods is more favorable.


Journal of Separation Science | 2008

Headspace single‐drop microextraction of herbal essential oils

Martin Adam; Petr Dobiáš; Aleš Eisner; Karel Ventura

A method employing the headspace single-drop microextraction (HS-SDME) is presented for the determination of essential oils in dried herbal leaves. By optimising the key experimental parameters, a linear response for the individual target compounds was obtained in the concentration range from LOQ to 4 mg/mL (r(2) = 0.9912-0.9998), with LODs from 3.3 up to 20.5 microg per 100 g of dried leaves, and the repeatability within the RSD of 2.1-8.9%. The HS-SDME-based procedure, enabling a rapid and simple analysis of essential oils in herbs, was applied to selected real samples (nine essential oils in four different samples) in combination with GC-FID identification and quantification of the target volatiles.


Journal of Separation Science | 2008

Comparison of supercritical fluid and Soxhlet extractions for the isolation of nitro compounds from soils

Petra Bajerová; Aleš Eisner; Věra Ježová; Martin Adam; Karel Ventura

Supercritical fluid extraction (SFE) with CO(2), a clean and rapid alternative to conventional Soxhlet extraction, was investigated for the extraction of nitro compounds from soil samples. Quantitative extraction by SFE was accomplished at a pressure of 25 MPa and an extraction temperature of 60 degrees C, for 30 min in dynamic mode and using acetonitrile as modifier, and the results were comparable with those obtained by acetonitrile Soxhlet extraction (3 h) for all soil samples. Extracts from these two procedures were analyzed by gas chromatography coupled with mass spectrometry. Quantitative reproducibility for SFE extracts was acceptable (RSD 2-10%), and the quantity of solvent was reduced from 160 mL for Soxhlet extraction to 5 mL in the case of SFE.


Journal of Separation Science | 2013

Solid-phase microextraction based method for determination of essential oils components in herbal beverages

Martin Adam; Andrea Čížková; Aleš Eisner; Karel Ventura

A method employing the direct immersion solid-phase microextraction followed by GC-MS analysis is presented for the determination of essential oils components in herbal tea infusions, i.e. their direct content in the liquid phase. The extraction performances were compared using five different microextraction fibres. Significant parameters affecting sorption process such as sample amount, sorption and desorption time and temperature, stirring speed, pH adjustment and effect of ionic strength were optimised and discussed. By optimising the key parameters, a detection limits (LOD = S/N × 3) for ten target marker compounds were obtained in the range from 5.3 to 48.2 ng/mL with recoveries ranged between 93.03 and 100.50%. Intra-day and inter-day repeatability at three concentration levels were found to be 1.1-15.3 and 7.2-15.5% RSD, respectively. Finally, the optimised procedure enabling a rapid and simple analysis of essential oils was applied for the direct determination of these compounds in ten herbal tea infusions.


Central European Journal of Chemistry | 2009

Comparison of solid-phase and single-drop microextractions for headspace analysis of herbal essential oils

Martin Adam; Petr Dobiáš; Petra Pavlíková; Karel Ventura

The analytical microextraction methods of gas chromatography coupled with flame ionisation detector (GC-FID) for determination of selected essential oils in herbs were proposed. Two microextraction methods for the isolation of essential oils from plants such as Lavandula spica L., Melissa officinalis L., Mentha piperita L. and Salvia officinalis L. were used. The methods of solid-phase and single-drop microextractions, were optimised and compared. The obtained LOD values for all studied essential oils were found to be within 2.5–20.5 μg for SDME and 57.0–139.8 μg for SPME method per 100 g of dried sample leaves. The appropriate LOQ values were then 8.4–68.4 μg for SDME and 189.8–466.1 μg for SPME of target analytes per 100 g of dried sample leaves.


Talanta | 2012

Optimization of focused ultrasonic extraction of propellant components determined by gas chromatography/mass spectrometry

Ondřej Fryš; Petr Česla; Petra Bajerová; Martin Adam; Karel Ventura

A method for focused ultrasonic extraction of nitroglycerin, triphenyl amine and acetyl tributyl citrate presented in double-base propellant samples following by the gas chromatography/mass spectrometry analysis was developed. A face-centered central composite design of the experiments and response surface modeling was used for optimization of the time, amplitude and sample amount. The dichloromethane was used as the extractant solvent. The optimal extraction conditions with respect to the maximum yield of the lowest abundant compound triphenyl amine were found at the 20 min extraction time, 35% amplitude of ultrasonic waves and 2.5 g of the propellant sample. The results obtained under optimal conditions were compared with the results achieved with validated Soxhlet extraction method, which is typically used for isolation and pre-concentration of compounds from the samples of explosives. The extraction yields for acetyl tributyl citrate using both extraction methods were comparable; however, the yield of ultrasonic extraction of nitroglycerin and triphenyl amine was lower than using Soxhlet extraction. The possible sources of different extraction yields are estimated and discussed.

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Aleš Eisner

University of Pardubice

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Daniel Kremr

University of Pardubice

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