The synthesis and analytical capabilities of chromogenic aza-12-crown-4 as a selective reagent for lithium ion

The synthesis and analytical capabilities of a new chromogenic crown ether, 1-(2-hydroxy-5-nitrobenzyl)-1-aza-4,7,10-trioxacyclododecane, chromogenic aza-12-crown-4. Constants found for this aza-12-crown-4 were pK_a1 = 5.77, pK_a2 = 10.31, pK_ex (Li) = 10.18, and pK_ex (Na) = 12.50. The calibration curve obtained for the extraction-spectrophotometric procedure was linear from 0.3 to 2 μg ml^?1. The imprecision of the measurement was calculated from the mean value of the standard deviations of triplicate samples over the linear range and was less than 5%. Results for the determination of lithium in blood serum and urine exhibited good agreement with atomic absorption data.