CROWN ETHER-BASED EXTRACTION PHOTOMETRIC REAGENTS FOR CALCIUM

抄録

New, highly sensitive extraction photometric reagents for calcium were derived from cryptand-21 and -22 by introducing mono-protonic chromophoric groups, 2-hydroxy-5-X-benzyls (X = 4-nitrophenylazo, 2, 4-dinitrophenylazo), on the amino nitrogens. The reagents (H₂L) extracted alkaline earth metal ions (M²⁺) into 1, 2-dichloroethane by forming ML type complexes. The selectivity followed the order, Ca²⁺>Sr²⁺>Ba²⁺>>Mg²⁺, for both types of the reagents, and the extractability with cryptand-22 reagents surpassed that of cryptand-21 reagents. The interferences and the masking of transition metals in the determination of calcium were studied.