Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 7. Sensing of Fe(CN)64–

✍ Scribed by Mila Maizels; Carl J. Seliskar; William R. Heineman

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 179 KB
• Volume: 12
• Category: Article
• ISSN: 1040-0397
• DOI: 10.1002/1521-4109(200011)12:17<1356::aid-elan1356>3.0.co;2-p

✦ Synopsis

A spectroelectrochemical sensor that has trimodal selectivity (selective partitioning, electrochemistry, and spectroscopy) is evaluated for the determination of ferrocyanide in solution. The sensor is based on attenuated total re¯ection spectroscopy at an indium-tin oxide optically transparent electrode coated with a cationic PDMDAAC-SiO 2 , where PDMDAAC means poly(dimethyldiallylammonium chloride) ®lm into which anionic Fe(CN) 6 47 partitions. Fe(CN) 6 47 loaded into the ®lm is subjected to spectroelectrochemical modulation, and the absorbance change at 420 nm associated with cycling Fe(CN) 6 47 =Fe(CN) 6 37 is used to quantitate the analyte. Cyclic voltammograms of Fe(CN) 6 47 , 0.1 M KNO 3 at high concentrations showed multiple peaks, which are interpreted as two types of Fe(CN) 6 47 =Fe(CN) 6 37 in the PDMDAAC-SiO 2 ®lm: Fe(CN) 6 47 bound to PDMDAAC and free Fe(CN) 6 47 in interstitial regions of the porous ®lm. The sensor response was affected by ionic strength and anion type of the supporting electrolyte and ®lm thickness. The diffusion coef®cient of Fe(CN) 6 47 in the PDMDAAC-SiO 2 ®lm was determined to be 4.9610 711 cm 2 =s. An analytical calibration plot of absorbance change at 420 nm versus Fe(CN) 6 47 concentration with a preconcentration time to equilibration was linear from 5 to 400 mM ferrocyanide with negative deviation from linearity observed at higher concentrations. However, a linear calibration plot at high concentrations (1±8 mM) could be achieved by making sensor measurements in a very short time period, only 1 min after exposure to the sample.