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Garcia CA, Júnior LR, Neto Gde O.
J Pharm Biomed Anal. 2003 Feb 5;31(1):11-8.
Determination of potassium ions in pharmaceutical
samples by FIA using a potentiometric electrode based on
ionophore nonactin occluded in EVA membrane.
Department of Chemistry, UFS, 49100-000, São
Cristóvão, SE, Brazil.
cgarcia@sergipe.ufs.br
A simple and rapid method was developed for the
K(+) ions determination employing a flow injection system using
a flow-through electrode based on the naturally-occurring
antibiotic ionophore nonactin occluded in a polymeric membrane.
The nonactin ionophore was trapped in poly(ethylene-co-vinyl
acetate) (EVA) matrix (40% w/w in vinyl acetate) and dispersed
on the surface of a graphite-epoxy tubular electrode. The
plasticizer-free all-solid-state potassium-selective electrode
showed a linear response for K(+) concentrations between 5.0 x
10(-5) and 5.0x10(-2) M (r=0.9995) with a near-Nernstian slope
of 51.5 mV per decade, when Tris-HCl buffer (pH 7.0;0,1 M) was
employed as a carrier. The potentiometric-FIA system allows an
analytical frequency of 120 samples per hour with a precision of
3.6%. The relative standard deviations (R.S.D.) for K(+)
determination in pharmaceuticals samples, without any previous
treatment, were lower than 4.0%, comparable to those obtained by
flame photometry. Ammonium is the main analytical interference
and the electrode response time was 5 s at 25 degrees C. The
useful lifetime of the tubular sensor is longer than 3 months in
continuous use.
PMID: 12560044 |
