Direct Determination of Phosphite in Fertilizers by Flow‐Injection Amperometry |
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Authors: | Vanessa Pezza Franzini Cecílio Sadao Fugivara Assis Vicente Benedetti Clóvis Augusto Ribeiro Eder Tadeu Gomes Cavalheiro José Anchieta Gomes Neto |
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Affiliation: | 1. Departamento de Química Analítica, Universidade Estadual Paulista, 14801‐970, PO Box 355, Araraquara‐SP, Brazil;2. Instituto de Química de S?o Carlos, Universidade de S?o Paulo, P.?O. Box 780, 13560‐970 S?o Carlos, SP, Brazil |
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Abstract: | A sensor based on graphite electrode modified with palladium‐platinum‐palladium film is proposed for phosphite determination by flow‐injection amperometry. The modified electrode was prepared by a sequential cathodic deposition of Pd, Pt and Pd on a graphite electrode from 0.5% m/v PdCl2+28% m/v NH4OH and 2% m/v H2PtCl6+10% v/v H2SO4 solutions. After suitable conditioning, the electrode showed catalytic activity for phosphite oxidation when 0.15 V was applied. The proposed system handles approximately 50 samples per hour (0.01–0.05 mol L?1 Na2HPO3; R2=0.9997), consuming ca. 70 μL of sample per determination. The limit of detection and amperometric sensibility were 5×10?4 mol L?1 and 1.5 mA L mol?1, respectively. The proposed method was applied to analysis of fertilizer samples without pre‐treatment. Results are in agreement with those obtained by spectrophotometry and titrimetry at 95% confidence level and good recoveries (96–109%) of spiked samples were found. Relative standard deviation (n= 12) of a 0.01 mol L?1 Na2HPO3 sample was 2%. The useful lifetime of modified electrode was around 220 determinations. For routine purposes it means that this electrode can be continuously used for 5 hours. |
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Keywords: | Phosphite Fertilizer Modified electrode Flow‐injection analysis |
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