Primaquine-selective electrodes based on macrocyclic crown ethers

Abstract

Electrodes based on poly(vinyl chloride) matrix membranes containing one of three macrocyclic crown ethers with dioctyl phenyl phosphonate solvent mediator and, in some instances, anion excluder have been studied for their potentiometric response to the primaquinium cation. Primaquine-selective electrodes based on dibenzo(18-crown-6) gave sub-Nernstian responses while those based on dibenzo(24-crown-8)(DB24C8) and dibenzo(30-crown-10)(DB30C10) exhibited good electrochemical characteristics such as Nernstian responses, fast dynamic response times (≈30 s), a wide range of working pH (pH ≈ 4–10) and good selectivity over many metal cations, chloroquine and sulfonamide drugs. The addition of 50% mole ratio anion excluder, relative to the sensor, not only led to an improvement in the e.m.f. stability, but also produced, in most instances, improved selectivity characteristics for both the DB24C8- and DB30C10-based electrodes. Determination of primaquine diphosphate (4.5–453.0 µg cm^–3) using the standard additions method resulted in a mean recovery and relative standard deviation of 107.0 and 8.0%, respectively. Determination of primaquine in pharmaceutical preparations is also described.