1994 Volume 10 Issue 1 Pages 187-192
New precipitation reactions for alkali metal ions are proposed. The crown ether complexes of alkali metal ions were found to be less soluble than the alkali metal ions, themselves, in water when they form ion-association complexes with a bulky anion, such as the Hexyl ion (Hexyl-: 2, 4, 6, 2′, 4′, 6′-hexanitrodiphenylaminate ion) and its analogues as a counter ion. The apparent solubility products (K′sp) of alkali metal ions were determined in aqueous solutions. On the basis of the precipitation reaction, a flow-injection (FI) method for the spectrophotometric determination of potassium ions in water samples is proposed. A double-line FI system was assembled, and samples were injected into a carrier stream, which merged with a reagent stream containing bulky anions, a crown ether, EDTA and saturated potassium ions. Calibration graphs with Hexyl- and DC18C6 (dicyclohexano-18-crown-6) as well as with α-Hexyl(2, 4, 6-trinitrophenyl-2′, 4′-dinitronaphthylaminate ion) were linear over the range 2×10-6-1×10-4M (M=mol dm-3) and 1× 10-7-1×10-5M potassium ion, respectively.
