市販野菜表面のリン酸の簡易吸光光度定量 : モリブドリン酸-マラカイトグリーン会合体のメンブランフィルター捕集

抄録

Phosphate on the surface of vegetables was determined by the spectrometric detection of the molybdophosphate-Malachite Green aggregate after preconcentration with a membrane filter. Vegetables obtained commercially were washed by an adequate volume of water, and the Mo-MG reagent (mixed solution of ammonium molybdate and Malachite Green) was added to the washings. The molybdophosphate-Malachite Green aggregate formed was selectively collected on a nitrocellulose membrane filter (3 μm pore size) and dissolved in methylcellosolve together with the membrane filter. The absorbance at 627 nm was proportional to the concentration of phosphate in the washings with the molar absorptivity of 2.7×10⁵ M^-1 cm^-1. The method was applied to the determination of phosphate on the surface of vegetable samples ; soybean sprouts, edible burdock roots and young taroes. In the case of soybean sprouts, the amounts of phosphate (20-37 μg P/g sample) for the white samples (8 samples) were higher than those for natural color samples (12 samples). For the samples of edible burdock roots packed in vinylresine bags, the amount of phosphate was about 170 mg P/g sample which was about two-fold larger than the natural one. Phosphate was also detected for young taroes (peeled and washed at the market) with an amount about twenty-fold larger than the natural one (1 μg P/cm² surface). Phosphate used for the surface treatment did not penetrate taroes deeper than 1 mm.