A construção, avaliação e aplicação analítica de um sensor potenciométrico do tipo PtHgHg 2 (Fur) 2 Grafite, onde Fur significa íon 4-cloro-N-furfuril-5-sulfamoil-antranilato, são descritas. O eletrodo responde a Fur com sensibilidade de (−58,4 ± 0,9) mV década -1 no intervalo de 5,0 × 10 -7 -1,0 × 10 -2 mol L -1 , a pH 7,0-9,0 e com um limite de detecção de 3,8 × 10 -7 mol L -1 . O eletrodo é facilmente construído e de baixo custo, apresenta um rápido tempo de resposta (10-20 s) e pode ser usado por um período de 6 meses sem qualquer variação considerável nas suas características de desempenho. O eletrodo proposto mostrou boa seletividade na presença de várias substâncias, bem como na presença de alguns carboxilatos e ânions inorgânicos. O eletrodo foi aplicado com sucesso na determinação de furosemida em medicamentos, urina, soro sanguíneo e amostras comerciais de leite bovino.The construction, evaluation and analytical application of a potentiometric sensor, namely, PtHgHg 2 (Fur) 2 Graphite, where Fur stands for 4-chloro-N-furfuryl-5-sulphamoyl-anthranilate ion, are described. This electrode has a linear dynamic range between 5.0 × 10 -7 -1.0 × 10 -2 mol L -1 with a near-Nernstian slope of (-58.4± 0.9) mV decade -1 and a detection limit of 3.8 × 10 -7 mol L -1 . The potentiometric response is independent of the pH of the solution in the pH range 7.0-9.0. The electrode shows easy construction, low-cost, fast response time (within 10-20 s) and can be used for a period of 6 months without significant change in its performance characteristics. The proposed sensor displayed good selectivities over a variety of other anions (carboxylates and inorganic anions). Application of this potentiometric sensor for the furosemide determination in pharmaceuticals, urine, blood serum and commercial milk samples is reported.Keywords: 4-cloro-N-furfuryl-5-sulphamoylanthranilate-sensitive electrode, potentiometry, pharmaceuticals, urine, human blood serum, bovine milk
IntroductionFurosemide or frusemide (HFur, 4-chloro-N-furfuryl-5-sulphamoyl-anthranilic acid) is formally a sulfonamide, an antibacterial agent (Figure 1). However, the intense and fast dieresis produced by this drug has extended its application as a powerful acidic diuretic for diverse treatments in humans and veterinary medicine. Furosemide is often classified as a loop diuretic due to its predominant action in the nephron, where the drug interferes with the tubular re-absorption of sodium on Henle's loop. 1 The renal excretion of ions is not limited to sodium and chloride, but it may also influence potassium, magnesium, calcium and, to a lesser extent, hydrogen carbonate ions. 2 In the clinical practice, the effects of furosemide are applied in the treatment of edema associated with pulmonary, cardiac, hepatic and renal disease, and of hypertension accompanied by fluid retention or impaired renal failure. 3-7 A marked diuresis is also associated to loss of weight, a side effect that has been incorrectly abused in the sport practice to achieve acute weight ...