Off-line coupling of pressurized liquid extraction and LC/ED for the determination of retinyl acetate and tocopherols in infant formulas.
An analytical methodology including pressurized liquid extraction (PLE) as sample treatment to isolate retinyl acetate and tocopherols from infant formulas has been developed. The milk extracts were kept at -18 degrees C for 30min and after filtration could be injected directly into the chromatographic system. Thus, a rapid and simple routine control method of these products is possible. The parameters affecting both the extraction process and the liquid chromatography (LC) system were optimized. PLE was performed using one cycle of extraction during a static time of 5min. Methanol was chosen as the extraction solvent for a temperature of 50 degrees C. Chromatographic separation was accomplished using a RP-18 column; the mobile phase used was methanol-water (94:6, v/v) containing 2.5mM acetic acid/sodium acetate buffer. Electrochemical detection in amperometric mode with a glassy carbon electrode at +1100mV was applied. The proposed methodology was successfully used for the determination of retinyl acetate, delta-tocopherol, (beta+gamma)-tocopherol and alpha-tocopherol in different infant formulas. The analytes were evaluated in the same chemical form present in the samples. Recoveries were between 92 and 106%. A certified reference material of milk powder was also analyzed.
Delgado-Zamarreño
M M
MM
Departamento de Química Analítica, Nutrición y Bromatología, Universidad de Salamanca, 37008 Salamanca, Spain.
Bustamante-Rangel
M
M
García-Jiménez
M
M
Sánchez-Pérez
A
A
Carabias-Martínez
R
R