Abstract
The atomic absorption spectrophotometry was applied to the determination of calcium in foods.
(1) Absorption at 422.7mμ was employed for the determination of calcium.
(2) A linear relationship between the absorbance and the concentration was found in the range of 0-50ppm calcium. (Fig. 5)
(3) Samples were ashed in an electric furnace at 550°C, and, after the ashes were dissolved in 4ml of 6N hydrochloric acid and made up to 100ml with water, the solution was submitted to the analysis of calcium. (Fig. 6)
Tin, potassium, chromium and aluminum interfered remarkably with the calcium determination, whereas zinc and iron interfered only slightly.
The interferences were eliminated by adding a solution containing 6000ppm magnesium, 200ppm sodium and 1500ppm potassium. However, when 50ppm of aluminum was contained, the interference was not eliminated. (Figs. 2, 3, 4)
Recoveries of calcium added were satisfactory, and the values obtained by atomic absorption spectrophotometry agreed with those obtain d by EDTA-titration method. (Tables I, II).
(4) The reproducibility of the analytical values was satisfactory, that is, the coefficients of variation for calcium were 2.6% for apple and 1.6% for pear. (Table V)
(5) The amounts of calcium in agricultural products were: 20-30mg% in raw vegetables, 3-10mg% in raw fruits, about 35mg% in canned pineapple and 3-15mg% in other canned fruits, respectively. (Table III)
(6) The amounts of calcium in marine products were: 25-70mg% in shellfishes and 10-20mg% in fishes, respectively. (Table IV)
Since the determination of calcium by atomic absorption spectrophotometry is convenient and rapid, and the interferences of coexistent elements can be controlled, it is considered that the method is best for the determination of calcium in foods.
