title: Application of a picrolonate ion-selective electrode to the assay of calcium and piperazine in pharmaceuticals and serum.
abstract: The construction and some analytical applications of a liquid picrolonate (Picrl-) ion-selective electrode based on the tris(phenanthrolinato)iron(II) (ferroin) picrolonate salt, dissolved in 2-nitrotoluene, are described. The liquid membrane electrode exhibits a rapid and almost Nernstian response to picrolonate anions in the concentration range from 5 x 10(-2) to 5 x 10(-2) mol l-1. The response is virtually unaffected by pH changes in the range 3-10. Major interferents are picrates, 4-nitrophenolates, 3,5-dinitrosalicylates and 2,4-dinitrophenolates. In analytical applications direct potentiometric methods for the determination of picrolonates and indirect methods for the determination of calcium and piperazine are described. Calcium in the ranges 4-24 and 50-90 mg l-1, under specified experimental conditions, can be determined with mean relative errors of 1.1 and 1.4%, respectively. The method is applicable to soluble samples, pharmaceuticals and industrial and real human serum. Piperazine in the ranges 1-10 and 13-20 mg can be determined with a mean relative error of 1.2% in soluble salts and pharmaceutical formulations, respectively. An accuracy of better than 1.5% and a reproducibility (relative standard deviation) of 0.1% were achieved in the analysis of pharmaceutical products.
authors.affiliation: Laboratory of Analytical Chemistry, University of Ioannina, Greece.
authors.forename: P G
authors.initials: PG
authors.lastname: Veltsistas
authors.forename: M I
authors.initials: MI
authors.lastname: Prodromidis
authors.forename: M I
authors.initials: MI
authors.lastname: Karayannis
mesh_terms: D002118:Calcium / Q000032:analysis* / Q000097:blood; D004566:Electrodes; D006801:Humans; D010879:Piperazines / Q000032:analysis* / Q000097:blood; D011720:Pyrazoles / Q000737:chemistry*; D047069:Pyrazolones; D013607:Tablets
chemical_list: D010879:Piperazines; D011720:Pyrazoles; D047069:Pyrazolones; D013607:Tablets; C010291:picrolonic acid; D002118:Calcium