p-Aminobenzoate ion determination in pharmaceutical formulations by using a potentiometric sensor immobilized in a graphite matrix.
The characteristics, performance, and application of an electrode, namely, Pt|Hg|Hg(2)(PABzt)(2)| graphite, where PABzt stands for p-aminobenzoate ion, are described. This electrode responds to PABzt with sensivity of (58.1+/-1.0) mV per decade over the range 1.0x10(-4) to 1.0x10(-1)moll(-1) at pH 6.5-8.0 and a detection limit of 3.2x10(-5)moll(-1). The electrode shows easy construction, fast response time (within 10-30s), low-cost, and excellent response stability (lifetime greater than 6 months, in continuous use). The proposed sensor displayed good selectivity for p-aminobenzoate in the presence of several substances, especially, concerning carboxylate and inorganic anions. It was used to determine p-aminobenzoate in pharmaceutical formulations by means of the standard additions method. The results obtained by using this electrode compared very favorably with those given by an HPLC procedure.
Santini
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Instituto de Quimica-UNESP, P.O. Box 355, CEP 14801-970, Araraquara, SP, Brazil.
Silva
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Pezza
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Nasser
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Melios
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Pezza
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