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Direct Determination of Phosphite in Fertilizers by Flow‐Injection Amperometry
Author(s) -
Franzini Vanessa Pezza,
Fugivara Cecílio Sadao,
Benedetti Assis Vicente,
Ribeiro Clóvis Augusto,
Cavalheiro Eder Tadeu Gomes,
Neto José Anchieta Gomes
Publication year - 2007
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200703935
Subject(s) - amperometry , detection limit , palladium , chemistry , flow injection analysis , graphite , platinum , electrode , analytical chemistry (journal) , titration , nuclear chemistry , chromatography , catalysis , inorganic chemistry , electrochemistry , organic chemistry
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 PdCl 2 +28% m/v NH 4 OH and 2% m/v H 2 PtCl 6 +10% v/v H 2 SO 4 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 Na 2 HPO 3 ; R 2 =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 Na 2 HPO 3 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.