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Optimalization of Poly(neutral red) Coated-wire Electrode for Determination of Citrate in Soft Drinks

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ABSTRACT

This report presents an optimization of potentiometric measurements with citrate-selective electropolymerized poly(neutral red) electrodes. The optimal background electrolyte for these measurements is a TRIS buffer with nitrate at pH 8.5. The electrodes described here exhibit stable and reproducible near-Nernstian response to citrates with a low detection limit of 6 × 10-6 M. Electrodes polymerized from sulfuric acid and acetonitrile are compared in detail. Simple and sensitive method for quantification of citrate in real-life samples by potentiometry with poly(neutral red) electrodes are presented. Data from potentiometric measurements of citrate are compared with capillary electrophoresis.

No MeSH data available.


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Potential response of PNR electrode prepared from aqueous solution toward citrate at various pH's (3 and 5 (MES), 8.5 and 11 (TRIS)).
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f4-sensors-08-00594: Potential response of PNR electrode prepared from aqueous solution toward citrate at various pH's (3 and 5 (MES), 8.5 and 11 (TRIS)).

Mentions: Citric acid can lose three hydrogen ions (pK1=3.13: H3A↔H2A- + H+; pK2=4.75: H2A− ↔ HA2− + H+; pK3=6.40: HA2− ↔ A3− + H+) and each of these anions might interact with PNR in a different way. This possibility was examined by measuring the potentiometric response toward citrates at different pHs, in this case 3, 5, 8.5 and 11. Figure 4 shows that the response of the electrode toward citrate differs with pH. As can be seen from the potentiometric measurements with the PNR electrode, the polymer does not respond to the monovalent ion H2A- (pH=3). Only very limited response was observed for the divalent ion HA2- (pH=5). The trivalent ion A3- (pH=8.5 and 11), on the other hand, gives a nice response with a slope between -22 and -17 mV per concentration decade, which is close to the theoretical -20 mV for the trivalent anion. pH 8.5 is a better choice because the working range is slightly narrower at pH 11.


Optimalization of Poly(neutral red) Coated-wire Electrode for Determination of Citrate in Soft Drinks
Potential response of PNR electrode prepared from aqueous solution toward citrate at various pH's (3 and 5 (MES), 8.5 and 11 (TRIS)).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672997&req=5

f4-sensors-08-00594: Potential response of PNR electrode prepared from aqueous solution toward citrate at various pH's (3 and 5 (MES), 8.5 and 11 (TRIS)).
Mentions: Citric acid can lose three hydrogen ions (pK1=3.13: H3A↔H2A- + H+; pK2=4.75: H2A− ↔ HA2− + H+; pK3=6.40: HA2− ↔ A3− + H+) and each of these anions might interact with PNR in a different way. This possibility was examined by measuring the potentiometric response toward citrates at different pHs, in this case 3, 5, 8.5 and 11. Figure 4 shows that the response of the electrode toward citrate differs with pH. As can be seen from the potentiometric measurements with the PNR electrode, the polymer does not respond to the monovalent ion H2A- (pH=3). Only very limited response was observed for the divalent ion HA2- (pH=5). The trivalent ion A3- (pH=8.5 and 11), on the other hand, gives a nice response with a slope between -22 and -17 mV per concentration decade, which is close to the theoretical -20 mV for the trivalent anion. pH 8.5 is a better choice because the working range is slightly narrower at pH 11.

View Article: PubMed Central - PubMed

ABSTRACT

This report presents an optimization of potentiometric measurements with citrate-selective electropolymerized poly(neutral red) electrodes. The optimal background electrolyte for these measurements is a TRIS buffer with nitrate at pH 8.5. The electrodes described here exhibit stable and reproducible near-Nernstian response to citrates with a low detection limit of 6 × 10-6 M. Electrodes polymerized from sulfuric acid and acetonitrile are compared in detail. Simple and sensitive method for quantification of citrate in real-life samples by potentiometry with poly(neutral red) electrodes are presented. Data from potentiometric measurements of citrate are compared with capillary electrophoresis.

No MeSH data available.


Related in: MedlinePlus