Domingo Blanco Gomis

Simultaneous determination of fat-soluble vitamins and provitamins in milk by microcolumn liquid chromatography.

The fat-soluble vitamins A, D2, D3, E and K1, retinyl acetate, retinyl palmitate, tocopherol acetate, ergosterol and 7-dehydrocholesterol in milk were separated on a packed reversed-phase fused-silica microcolumn, and determined with UV detection. Conventional liquid chromatographic equipment was adapted for such purposes, providing a highly efficient and sensitive analytical system. The vitamins could be separated in gradient mode with detection limits comprised between 0.02 ng/ml for retinol and 2 ng/ml for vitamin E. All vitamins were separated in less than 17 min. Recovery studies showed good results for all solutes (89-107%) and the intra-day coefficients of variations ranged from 2 to 8%. Application of the proposed method to the quantification of fat-soluble vitamins in milk is reported.

Capillary liquid chromatographic determination of neutral phenolic compounds in apple juices

Capillary liquid chromatography (CLC) is evaluated as an alternative to conventional HPLC to analyse complex phenolics. Several neutral phenolic compounds were separated on a packed-reversed phase fused-silica capillary column, and determined with UV detection. A conventional liquid chromatographic equipment was adapted for such purposes. Application of the proposed method to the quantification of neutral phenols in apple juices is reported. Phenolics are extracted and fractionated into neutral and acidic compounds by means of a C18 solid-phase cartridge. Typical recoveries ranging from 90 to 105% are obtained and reproducibility between extractions is <7% in all cases. Mass detection limits are at the sub-nanogram level.

Speciation Analysis of Chromium Using Cryptand Ethers

The speciation analysis of chromium was studied using sequential solvent extraction of Cr III and Cr VI (previously reduced to Cr III ) with cryptand 2.2.1 as the ligand and eosin as a counter ion, in combination with spectrofluorimetry. A linear working range from the detection limit (1 ng ml - 1 ) to 150 ng ml - 1 of chromium was obtained. The proposed method was successfully applied to the determination of Cr III and Cr VI in sea-water and chromium in certified coal samples.

Determination of fat-soluble vitamins by capillary liquid chromatography in bovine blood plasma

Abstract The fat-soluble vitamins retinyl palmitate, D3, E and K1 were separated on a packed reversed-phase fused-silica capillary column using methanol-tetrahydrofuran as mobile phase, and determined with UV detection. Conventional liquid Chromatographic equipment was adapted for such purposes, providing a highly efficient and sensitive analytical system. The vitamins could be separated isocratically with detection limits of 2.9 pg, 1 pg, 29 pg and 2.6 pg, respectively. Application of the proposed method to the quantification of fat-soluble vitamins in blood is reported.

Simultaneous determination of vitamins D3, E and K1 and retinyl palmitate in cattle plasma by liquid chromatography with a narrow-bore column

A reversed-phase high performance liquid chromatographic method is described for the simultaneous determination of vitamins D3, E and K1 and retinyl palmitate in plasma. Narrow-bore columns are recommended because this alternative provides a good separation efficiency, plus greater economy and sensitivity. Detection limits for individual vitamins range from 0.42 to 2.8 ng. All vitamins were separated in less than 9 min. Recovery studies showed good results for all solutes (88.8-100.3%) and the intra-day coefficients of variations ranged from 1.0 to 4.5%. This method permits the simple determination of fat-soluble vitamins using 1 ml of cattle heparinized plasma.

Experimental design applied to the analysis of volatile compounds in apple juice by headspace solid-phase microextraction.

A simple and fast method based on solid-phase microextraction (SPME) followed by fast gas chromatography (Fast GC) has been developed for the analysis of volatile compounds in Asturian apple juices employed in the cider production. Three different fiber coatings have been checked (PDMS, PDMS-DVB and CAR-PDMS) and PDMS-DVB has been presented to be the most suitable one. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The use of Fast GC allowed the separation of 14 compounds (esters, aldehydes and alcohols) in approximately 4 min, clearly reducing the analysis time when compared to conventional GC. Good linearity, recoveries and repeatability of the solid-phase microextraction were obtained with r(2) values, recoveries and relative standard deviations ranging from 0.9822 to 0.9998, 83.2 to 109.8% and 0.5 to 11.7%, respectively, using standard solution.

Optimization by Factorial Design of a Capillary Electrophoresis Method for the Chiral Resolution and Determination of Zopiclone and Its Synthesis Precursor

Abstract A rapid, simple and accurate capillary electrophoretic method has been developed for the determination of zopiclone and its synthesis precursor, zopiclone II, by a factorial design. The compounds are separated in a fused silica capillary (48.5 cm length, 40 cm effective length, 50 µm inner diameter) with UV detection at 215 nm. Separation was achieved with a 60.2 mM phosphate buffer containing 20 mM β-cyclodextrin and 1 M of urea, adjusting the pH to 2.0 and using diazepam as an internal standard. The method was validated in accordance with the International Conference on Harmonization guidelines, appropriate linearity and precision being observed for all compounds. The recoveries obtained ranged between 97.6% and 100.7%. This method is sensitive (detection limits ranged between 2.1 and 7.2 mg L−1) and selective to quantify the enantiomers of zopiclone and its synthesis precursor and could be used to evaluate the chiral intermediates and the enantiomeric purity of the final product.

Determination of amino acids in ripening apples by high performance liquid chromatography

High performance liquid chromatography (HPLC) was used to monitor amino acid changes in ripening apples in order to increase knowledge of the biochemistry of this type of fruit with a view to determining the optimum ripening time and evaluating the potential influence of the amino acid content of the different apple varieties studied on the juices and fermented beverages nmade from them.ZusammenfassungDie Hochleistungsflüssigchromatographie wurde angewendet, um Reifungsprozesse zu untersuchen mit dem Ziel, das Wissen über die Biochemie des Reifungsprozesses zu verbessern, einerseits um das Reifungsoptimum zu erkennen und andererseits um die mögliche Bedeutung des Gehalts an Aminosäuren der verschiedenen Apfelsorten für die daraus hergestellten Säfte und Gärungsgetränke festzustellen.SummaryHigh performance liquid chromatography (HPLC) was used to monitor amino acid changes in ripening apples in order to increase knowledge of the biochemistry of this type of fruit with a view to determining the optimum ripening time and evaluating the potential influence of the amino acid content of the different apple varieties studied on the juices and fermented beverages nmade from them.

Sequential extraction-spectrofluorimetric determination of lead and cadmium using cryptands

A spectrofluorimetric method for the determination of ultratrace amounts of lead and cadmium is described based on the sequential extraction of the ternary ion-association complexes formed between the cation, a cryptand as the ligand and eosin as a counter ion. A linear working range from the detection limit (0.5 ng ml(-1) to 250 ng ml(-1) of lead and to 1 50 ng ml(-1) of cadmium was obtained. The relative standard deviation was 2-4%. The proposed method has been applied successfully to the determination of lead and cadmium in zinc metals and soft drinks.

A novel method for the determination of total 1,3-octanediols in apple juice via 1,3-dioxanes by solid-phase microextraction and high-speed gas chromatography

In this work, a novel, simple and fast method based on solid-phase microextraction (SPME) followed by high-speed gas chromatography (HSGC) was developed for the analysis of total 1,3-octanediols in apple juices by means of derivatization reaction to volatile 1,3-dioxanes. The derivatization reaction, SPME conditions, glycosidically bound fraction and 1,3-nonanediol as a surrogate standard were studied. The formation of 1,3-dioxanes from 1,3-diols was confirmed by GC-MS. The method was validated obtaining a regression coefficient (r(2)) of 0.9996, precisions between 0.3 and 9.8%, extraction recoveries in the range 94.7-112.2% and LOD of 2.9 microg l(-1). Experimental design has been employed in the optimization of extraction factors and robustness assessment. The method was applied to the analysis of 21 Asturian apple varieties finding a double reciprocal relationship between the concentrations of saturated and unsaturated 1,3-octanediol.