Flow injection and HPLC determination of furosemide using pulsed amperometric detection at microelectrodes

• Published in: Journal of pharmaceutical and biomedical analysis Vol. 33; no. 5; pp. 923 - 933
• Main Authors: Guzmán, Alicia, Agüı́, Lourdes, Pedrero, Marı́a, Yáñez-Sedeño, Paloma, Pingarrón, José M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 04.12.2003; Elsevier Science
• Subjects: Analysis; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chromatography, High Pressure Liquid - methods; Electrochemistry; Flow Injection Analysis - methods; Fundamental and applied biological sciences. Psychology; Furosemide; Furosemide - analysis; Furosemide - chemistry; General pharmacology; Medical sciences; Microelectrodes; Milk; Pharmacology. Drug treatments; Pulsed amperometric detection; Pulsed amperometric detection; Microelectrodes; Furosemide; Milk; Sulfanilamide derivatives; Sulfonamide; HPLC chromatography; Diuretic; Anthranilic acid derivatives; Antihypertensive agent; Detection; Quantitative analysis; Flow injection
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/S0731-7085(03)00422-9

The flow-injection and HPLC determination of the diuretic drug furosemide using pulsed amperometric detection (PAD) at cylindrical carbon fibre microelectrodes (CFMEs) is reported. Experimental conditions such as pH (6.5) and buffer concentration (0.05 mol l −1 HPO 4 2−/H 2PO 4 −) were optimized using square-wave voltammetry (SWV). Repetitive flow-injection amperometric measurements at +1.25 V for furosemide showed a continuous decrease in the peak current, probably as a consequence of the microelectrode surface fouling. However, a suitable amperometric detection of furosemide was achieved using a PAD program consisting of a two-step potential waveform with alternating anodic and cathodic polarization. The anodic (detection) potential was +1.25 V (time of application 0.1 s), and the cathodic (cleaning) potential was −0.20 V (t=0.2 s). A linear calibration graph was obtained for furosemide in the 5.0×10 −7–1.0×10 −4 mol l −1 concentration range, with a limit of detection of 1.7×10 −7 mol l −1. HPLC-PAD at carbon fibre microelectrodes was used for the determination of furosemide in the presence of several thiouracil drugs and oxytetracycline (OTC). The mobile phase selected was a 25:75 acetonitrile:5.0×10 −3 mol l −1 NaH 2PO 4 (pH 5.0) mixture. A linear calibration graph was obtained for furosemide in the 1–100 μM range, with a limit of detection of 0.55 μM. The usefulness of this method for the determination of furosemide in real samples was evaluated by performing the analysis of commercial milk samples spiked with furosemide at a concentration level of 4.5×10 −7 mol l −1 (150 ng ml −1), as well as with other thiouracil drugs and OTC. A mean recovery of 95±5% furosemide was obtained.