Antioxidants solid-phase extraction

An HPLC-DAD method was developed for the separation and the determination of flavonoid and phenolic antioxidants in commercial and freshly prepared cranberry juice.Two sample preparation procedures were used with and without hydrolysis of the glycoside forms of flavonoids carried out by the addition of HCl in the step prior to solid-phase extraction (SPE). The flavonoid and phenolic compounds were then fractionated into neutral and acidic groups via a solid-phase extraction method (Sep-Pak Cig), followed by a RP HPLC separation with gradient elution with water-methanol-acetic acid and a detection at 280 and 360 nm. A comparison of the chromatograms obtained for extracts prepared with and without hydrolysis showed that flavonoids and phenolic acids exist predominantly in combined forms such as glycosides and esters. In a freshly squeezed cranberry juice, for instance, 400 mg of total flavonoids and phenolics per liter of sample was found, 56% of which were flavonoids. Quercetin was the main flavonoid in the hydrolyzed products, where it accounted for about 75% of the total flavonoids, while it was absent in the unhydrolyzed products. 

M Hedenmo, BM Eriksson. On-line solid-phase extraction with automated cartridge exchange for liquid chromatographic determination of lipophilic antioxidants in plasma. J Chromatogr 692 161—166, 1995. 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

With low detection limit techniques, the identity, migration levels and accumulation of antioxidants and their degradation products in food, in hquids and in pharmaceutical solutions can be controlled. HPLC or GC-MS offers functional methods together with, e.g., hquid-liquid extraction (LLE). Recently, solid phase extraction (SPE) has been used successfully with lower detection hmits and smaller errors than LLE. SPE is a technique that uses a small amount of solvent and that efficiently concentrates solutions of analytes depending on, e.g., polarity. 

Litridou, M., Linssen, J., Schols, H., Bergmans, M., Posthumus, M., Tsimidou, M. andBoskou, D. (1997) Phenolic compounds of virgin olive oils fractionation by solid phase extraction and antioxidant activity assessment. J. Sci. Food Agric., 74, 169-174. 

See also Carbohydrates Overview. Extraction Solid-Phase Extraction Supercritical Fluid Extraction. Food and Nutritional Analysis Sample Preparation Antioxidants and Preservatives Mycotoxins Oils and Fats. Lip-Ids Overview. Peptides. Proteins Overview. Toxins Mycotoxins Neurotoxins. Vitamins Overview Fat-Soluble Water-Soluble. 

Liquid-solid extraction procedures are accompanied by a serious risk of contamination. For example, blank tests with commercial extraction columns have revealed traces of plasticizers and antioxidants as well as various alkanes and alkenes [154]. For this reason certain manufacturers now offer solid-phase extraction columns made from glass. The extent of the po-tential contamination depends on the manufac-turer, the adsorbent load, conditioning steps, and the solvent used for the extraction [154], [155], If no satisfactory commercial column is available, one can easily be prepared in the laboratory from a suitable adsorbent and an appropriate glass tube. For example, XAD can be purified to an extent sufficient for this purpose by Soxhiet extraction [ 156], [ 157]. which reduces the level of impurities by a factor of 30. Silica gel and aluminum oxide can be purified... 

Fries, E. and Puttmann, W. (2002) Analysis of the antioxidants butylated hydroxytoluene (BHT) in water by means of solid phase extraction combined with GC-MS. Water Research... 

A chemiluminescence method has been described for the determination of PG in edible oils using the enhancing effect of this antioxidant on the luminescent signal of 2-phenyl-4,5-di(2-furyl)-lH-imidazole (PDFI) and potassium ferricyanide system in an alkaline medium [57]. The method involves the use of solid-phase extraction with a Cjg cartridge as the stationary phase for sample treatment. The interferents were retained on the cartridge while PG was eluted. A flow system was used to introduce the reagents (PDFI, sodium hydroxide, and potassium ferricyanide) and the sample into the sample cell of the instrument and to measure the enhanced chemiluminescence signal, which was linearly related to the PG concentration. A detection limit of 36 ng/mL PG was obtained. 

A variety of solvent extraction techniques have been used to extract antioxidants from food matrices. The most commonly used is maceration or homogenization of the sample with an extraction solvent however, alternative procedures have been developed including pressurized fluid extraction (PFE), ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and matrix solid-phase dispersion (MSPD), among others. The principles of each extraction technique will be briefly discussed. 

Table 2.5 Examples of extraction of antioxidant phytochemicals from various plant materials by matrix solid phase dispersion. (MSPD). 

Flow injection methods have excellent potential in almost all areas of analysis since they provide high-throughput analysis (increase of analytical frequency) and the possibility of automation. However, the application of analytical methods based on flow analysis for food analysis has still received little attention, due to the complexity of food matrices (Lopez-Fernandez et al., 1995). Therefore, the development of automated methods for the determination of additives, such as synthetic antioxidants (e.g., BHA, BHT, and TBHQ), is a promising area of investigation. Flow injection solid-phase spectrophotometry was used for the determination of BHA and PC in fatty food (dehydrated chicken soup, chicken cream, bull calf, and chicken broth) and cosmetics, providing greater selectivity to the conventional spectrophotometric technique. After extraction with petroleum either for food and with hexane for cosmetics, the two antioxidants were separated by... 

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