title: Flow-injection analysis of dopamine in injections with a periodate-selective electrode.
abstract: Dopamine determination in pharmaceutical preparations based on its oxidation with periodate (IO(4)(-)) using a new IO(4)(-)-selective electrode under flow conditions is presented. An electrode with a tubular configuration, no internal reference solution, and a PVC (31. 2%) membrane, with metaperiodate bis(triphenylphosphoranylidene)ammonium (1.3%) as ion exchanger and 2-nitrophenyloctylether (67.5%) as mediator solvent, was used. Optimization procedures were directed at potentials versus dopamine readings instead of potential versus the remaining IO(4)(-). This approach was achieved by selecting a 50-cm reactor and an overall flow of 7 mL/min, and injecting 70 microL of dopamine standards in a 3.0 x 10(-4) M IO(4)(-) solution. Under these conditions, a linearity range of 8.0 x 10(-3) to 2.7 x 10(-1) g/L, with a slope of 310.1 +/- 7.4 mV L g(-1) and a reproducibility of +/-0.4 mV, were recorded (n = 8). Interference from common excipients was negligible. Under these conditions, analysis of dopamine injections (n = 12) presenting 200 mg/injection gave average and standard deviation values of 201.0 and 3.3 mg/injection, respectively. A simple and inexpensive flow-injection analysis (FIA) manifold, with a good potentiometric detector, enabled the analysis of 200 samples/h without requiring pretreatment procedures. Comparison with the dopamine injection analysis in the United States Pharmacopoeia monograph showed good accuracy, with a relative deviation of -0.2%.
authors.affiliation: CEQUP/Departamento de Química-Física, Faculdade de Farmácia, R. Aníbal Cunha, Porto, Portugal. mcbranco@mail.ff.up.pt
authors.forename: M C
authors.initials: MC
authors.lastname: Montenegro
authors.forename: M G
authors.initials: MG
authors.lastname: Sales
mesh_terms: D004298:Dopamine / Q000008:administration & dosage / Q000032:analysis*; D004566:Electrodes; D005079:Excipients; D017022:Flow Injection Analysis; D007202:Indicators and Reagents; D007475:Ion Exchange Resins; D010504:Periodic Acid / Q000737:chemistry*
chemical_list: D005079:Excipients; D007202:Indicators and Reagents; D007475:Ion Exchange Resins; D010504:Periodic Acid; D004298:Dopamine