Batch and FIA Spectrophotometric Determination of Sodium and Potassium Ions via Reaction with Sulfophthalein Derivatized Crown Ethers

Abstract

The mono‐ and bis‐monoaza‐15‐crown‐5‐ethers and monoaza‐18‐crown‐6‐ethers, bound to the sulphophthalein dyes phenol and bromophenol red, were synthesized. Their complexing properties were studied and, on this basis, these substances were found to be suitable spectrophotometric reagents for nonextraction batch and flow‐through (FIA) determination of Na⁺ and K⁺ ions in ethanol medium. The optimal reaction and flow conditions were found and a method was developed for determination of both ions. Although the reactions are not fully selective toward both ions, it is possible to carry out the determination of both ions in sample by using a suitably selected reagent at certain concentration ratios. The results are comparable for both dyes and for the mono‐ and bis‐compounds; the size of the cavity in the crown ether is decisive.

Keywords:

• Alkali metals
• Crown ethers
• Sulphophthaleins
• Protic medium
• FIA

Acknowledgement

This work was supported by Research Project MSM 113 10000002 (Czech Republic).