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Determination of selenium content in different types of seed oils by cathodic stripping potentiometry (CSP)

Dugo, G., La Pera, L., Pollicino, D., Saitta, M.
Journal of agricultural and food chemistry 2003 v.51 no.19 pp. 5598-5601
seed oils, peanut oil, soybean oil, sunflower oil, rice oil, corn oil, grapeseed oil, selenium, nutrient content, mineral content, food analysis, potentiometers
Seed oils are consumed worldwide; moreover, they are used in the alimentary, cosmetic, pharmaceutical, and chemical industries. Due to their diffusion, it is interesting to investigate the presence of important micronutrients such as selenium in seed oils. The aim of this work was to develop a rapid, precise, and sensitive cathodic stripping potentiometry (CSP) method to determine the concentration of selenium in different types of seed oils. Selenium was extracted from the oily matrix by concentrated hydrochloric acid treatment at 90 °C. The analysis was executed by applying an electrolysis potential of -150 mV for 60 s and a constant current of -30 microampere. Under these conditions, detection limits of <0.5 ng g-1 were obtained. The method reproducibility (expressed as total RSD %) spanned from 0.2 to 0.8%. Recoveries ranged from 92.1 to 97.5%, providing evidence that selenium quantification remained unaffected by the extraction procedure described. The results obtained with the proposed method were compared with those obtained via graphite furnace atomic absorption spectroscopy (GFAAS), a common method for determining selenium. The results of the two methods agreed within 93.5-107.7%. The mean amounts of selenium found were 313.0 ± 2.0, 458.3 ± 1.3, 224.6 ± 0.9, 99.5 ± 0.8, 332.2 ± 0.5, 144.0 ± 0.7, and 295.5 ± 1.2 ng g-1, respectively, in peanut, soybean, sunflower, rice, corn, grapestone, and seed oils.