کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1190690 | 963537 | 2010 | 6 صفحه PDF | دانلود رایگان |
Ascorbic acid is found in many food samples. Its clinical and technological importance demands an easy-to-use, rapid, robust and inexpensive method of analysis. For this purpose, this work proposes a new flow procedure based on the oxidation of ascorbic acid by periodate. A new potentiometric periodate sensor was constructed to monitor this reaction. The selective membranes were of PVC with porphyrin-based sensing systems and a lipophilic cation as additive. The sensor displayed a near-Nernstian response for periodate over 1.0 × 10−2–6.0 × 10−6 M, with an anionic slope of 73.9 ± 0.9 mV decade−1. It was pH independent in acidic media and presented good selectivity features towards several inorganic anions. The flow set-up operated in double-channel, carrying a 5.0 × 10−4 M IO4- solution and a suitable buffer; these were mixed in a 50-cm reaction coil. The overall flow rate was 7 ml min−1 and the injection volume 70 μl. Under these conditions, a linear behaviour against concentration was observed for 17.7–194.0 μg ml−1, presenting slopes of 0.169 mV (mg/l)−1, a reproducibility of ±1.1 mV (n = 5), and a sampling rate of ∼96 samples h−1. The proposed method was applied to the analysis of beverages and pharmaceuticals.
Journal: Food Chemistry - Volume 120, Issue 3, 1 June 2010, Pages 934–939