Synthesis of fluorophosphonazo-DBF (FPA-DBF) and the study on its chromogenic reaction with rare earths, bismuth and thorium .

New chromogenic reagent fluorophosphonazo-DBF(FPA-DBF) was synthesized and refined. Conditions of its chromogenic reaction with rare earths, bismuth and thorium were optimized. The ranges of acidity for reactions with rare earths are pH 0.49 - 2. 09 (cerium), pH 0. 61-2. 09(yttrium). The complexes of rare earths with the reagent have maximum absorption at about 630 nm and the apparent molar absorptivitis are eCe=1.13×105 L·mol-1·cm-1 and eY = 1.08×105L·mol-1·cm-1.The ranges of acidity for reactions with bismuth and thorium are pH 0.14~1. 32,pH0. 08~0. 62 respectively. The apparent molar absorptivities of the complexes are eeBi=1.02×105L·mol-1·cm-1 and eTh = 1. 34×105L·mol-1·cm-1 respectively. This method has been used to determine Bi (Ⅲ) in compound bismuth aluminate tablets and trace Th (Ⅳ) in seafood with satisfactory results.