Combination of Solid Phase Extraction With Supercritical Fluid Extraction for the Determination of Contaminants in Water

Food Additives and Contaminants

Moravcová

et al. 2006

Two polar analytes, 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI), were extracted with supercritical carbon dioxide (CO2) modified with aqueous methanol. The method was applied to a roasted coffee powder with good recovery rates. Method efficiency was compared with that of solid-phase extraction using SCX Disc cartridges and validated for spiked solid matrix. The analytes were determined using isocratic liquid chromatography-mass spectrometry (LC/MS) on an Atlantis HILIC Silica column (150 x 2.1 mm, 3 microm) with 80% methanol and 20% 0.01 mol l-1 ammonium formate as the mobile phase. The limit of quantification was around 1.5 pg for 4-MeI and 2.0 pg for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients of >0.999. The coefficient of variation for the intra-day and inter-day precisions was <4% (n = 6). Accuracy was in the range 98-101%; recovery rates were > or = 98 and > or = 99% for THI and 4-MeI, respectively. Several samples of Arabica coffee from various locations and commercially available 'off-the-shelf' coffee products (Arabica/Robusta mixtures) were analysed to test the method.

Section: Supercritical Fluid Extractionmentioning

confidence: 99%

Supercritical fluid extraction (SFE) of 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI) from ground-coffee with high-performance liquid chromatographic-electrospray mass spectrometric quantification (HPLC/ESI-MS)

Food Additives and Contaminants

Moravcová

et al. 2006

“…All SFEs were carried out using an SE-l instrument (SEKO-K, Brno, Czech Republic) equipped with a Valco valve (VICI, Schenkon, Switzerland; loop 1 mL) for continuous modifier addition ( , ). The extraction cell was pressurized at 50−100 °C to 10−40 MPa using SFC/SFE grade CO 2 (Siad, Brno, Czech Republic) with 1−10% v/v of modifier mixture added via Valco valve to the instrument piston pump.…”

Section: Methodsmentioning

confidence: 99%

Supercritical Fluid Extraction of Bioavailable Amino Acids from Soils and Their Liquid Chromatographic Determination with Fluorometric Detection

Formánek

et al. 2006

J. Agric. Food Chem.

A new procedure with supercritical CO2 modified with 0.5 mL of water and 0.75 mL of 0.1 M HCl in situ and 0.75 mL of water on-line at 15 MPa and 50 degrees C for 45 min was applied for the extraction of bioavailable amino acids from soil samples. Total extraction time was 60 min, but more favorable conditions are even possible for selected groups of amino acids. All analytes were trapped into 20 mL of methanol with satisfactory recovery (94-104%) and determined using high-performance liquid chromatography with fluorometric detection on a Zorbax Eclipse column (4.6 x 75 mm, 3.5 microm) with Na2HPO4 and acetonitrile/methanol/water as a mobile phase. Linear calibration curves were obtained (r > 0.999 except 0.99823 for Ile) with lower limits of detection (S/N = 3) in the range from 1.54 pg (Gly) to 13.5 pg (Cy2) or from 18.6 fmol (Ser) to 64.8 fmol (Lys). Validation and repeatability data are also given. Comparable results were obtained with a robust, commonly used extraction method (0.5 M ammonium acetate, 60 min in shaker, followed by filtration and lyophilization). Limiting values of artificial release of amino acids were also determined for each soil sample to eliminate any false results to ensure that all extracted amino acids originate from soil solution and exchangeable bound positions of soil samples.

“…All extractions were carried out using an SE-l instrument (SEKO-K, Brno, Czech Republic) equipped with a Valco valve for continuous modifier addition (VICI, Schenkon, Switzerland, loop 1 mL) according to the method described by Ventura [18]. The extraction cell was pressurized at 35 to 1008C up to 10 -40 MPa using SFC/SFE grade CO 2 (Siad, Brno, Czech Republic) with 1 -10% v/v of modifier mixture added via a Valco valve to the instrument piston pump.…”

Section: Supercritical Fluid Extractionmentioning

confidence: 99%

“…For the troublesome lyophilized leaves matrix [18,19], it was necessary: (i) to find appropriate extraction conditions for SFE of AAs; (ii) to avoid the prospective matrix effect and verify the method robustness for various leaf samples; (iii) to confirm that amino acid enrichment of samples cannot occur during the extraction, either due to contamination by human touch or by hydrolysis of proteins or any other amino acids producing or releasing mechanism. Common validation and reproducibility tests were also performed.…”

Section: Introductionmentioning

confidence: 99%

Supercritical fluid extraction of amino acids from birch (Betula pendula Roth) leaves and their liquid chromatographic determination with fluorimetric detection

J of Separation Science

Kula

et al. 2008

A method for supercritical fluid extraction (SFE) of amino acids was adapted and optimal experimental conditions were selected for a matrix consisting of dry leaves. The matrix-dependent SFE method uses a mixture of MeOH-H(2)O-acetonitrile (10:10:1 v/v/v) as a modifier (0.5 mL in situ, 300 muL on-line) at 70 degrees C and 40 MPa and no HCl is needed as an entrainer. The amino acids were quantified using high-performance liquid chromatography with fluorimetric detection (HPLC/FLD) after gradient elution on Zorbax Eclipse AAA columns (4.6x150 mm, 3.5 mum) with aqueous Na(2)HPO(4 )buffer of pH 7.8 and ACN-MeOH-water as a mobile phase. In comparison with Soxhlet extraction, SFE gave higher recovery and selectivity, but it required longer extraction time (90 min) and it was more labor-intensive (clean-up step after the pre-concentration). Both methods should be used separately or in combination according to the matrix, number of samples, and levels of ballast compounds.