A carbon Paste electrode modified with cobalt (II) phthalocyanine (CoPC) was
used as a sensitive potentiometric sensor for determination of ascorbic acid in
aqueous solutions. The potential response of the electrode is a linear function of
ascorbic acid concentration over the range 5 10 to 10 M (?1- 1800 µg ML ) with a Nernstian slope of 56 mV at pH 7. The limit of detection was 0.2 µg ml ascorbic acid. The modified electrode was used to determine ascorbic acid in vitamin
preparations. The recovery was 97-98% for the vitamin added to the preparations with
a relative standard deviation of less than 5%.