Development and validation of liquid chromatographic method for the determination of lycopene in plasma

Simultaneous quantification of lycopene, β-carotene, retinol and α -tocopherol in plasma after a simple extraction procedure: stability study and application to human volunteers

“…However, most of them require protein precipitation, liquid-liquid extraction, drying under nitrogen stream and sample reconstitution prior to analysis. 1,[3][4][5][11][12][13]16,17,[19][20][21][22][23][24]26 In general, these procedures are quite laborious and do not eliminate the risk of unwanted transformations such as isomerization, oxidation and formation of degradation products. 25 Approximately 90% of the total plasmatic lipidsoluble vitamins in humans is associated with low-density lipoprotein and high-density lipoprotein fractions, so protein precipitation procedures with ethanol, methanol, isopropanol or acetonitrile, followed by extraction with organic solvents, have been currently used.…”

“…6,[7][8][9] High-performance liquid chromatographic (HPLC) methods are considered the best choice for the determination of lipid-soluble vitamins. The first method developed for the quantification of these vitamins was described in 1973 10 and up to now several studies have reported new methods for the quantification of these compounds with the use of various mobile phases, 1,[3][4][5][6]11,[12][13][14][15] the adoption of chromatographic columns with either normal 15,16 or reverse phases, 3,4,6,11,[17][18][19][20][21] and also different detectors, such as Vis, UV (DAD), 1,[3][4][5][6]11,[12][13][14][15][17][18][19][20][22][23][24][25] fluorescence (FLD), 4,6,15,…”

“…6,22,25 Many studies have indicated that it is necessary to use a gradient elution for the complete chromatographic separation of vitamins 1,3,11,15,19,20,22,25 and other works have described an isocratic elution. [4][5][6][12][13][14]16,17,21,23 Gradient elution involves a substantially longer chromatographic time, compared to the isocratic method, and also requires a rebalance of the HPLC system after injections. 12 So, methods that use isocratic elution are faster and less laborious.…”

“…Several procedures for sample extraction have been reported for vitamins, some of them based on protein precipitation using an organic solvent such as ethanol, methanol, isopropanol or acetonitrile, followed by liquid-liquid extraction and/or evaporation of the organic solvent under nitrogen stream and posterior reconstitution, 1,[3][4][5][11][12][13]16,17,[19][20][21][22][23][24]26 but these methods are normally very time-consuming. Extraction reagents include n-hexane, petroleum ether, dichloro methane-methanol, chloroform, ethyl acetate and n-butanol 1,[3][4][5][6][11][12][13]16,17,[19][20][21][22][23][24][25][26] with the addition of antioxidants such as butylated hydroxytoluene (BHT) 4,6,13,16,[19][20][21][22][23] or ascorbic acid 5 to avoid oxidation of lipidsoluble vitamins.…”

“…Extraction reagents include n-hexane, petroleum ether, dichloro methane-methanol, chloroform, ethyl acetate and n-butanol 1,[3][4][5][6][11][12][13]16,17,[19][20][21][22][23][24][25][26] with the addition of antioxidants such as butylated hydroxytoluene (BHT) 4,6,13,16,[19][20][21][22][23] or ascorbic acid 5 to avoid oxidation of lipidsoluble vitamins. Therefore, extraction methods without many steps for the samples treatment would offer a great advantage in the analysis of hydrophobic vitamins.…”