Abstract
Ascorbic acid can be determined by flow injection amperometry at a sessile mercury drop electrode without the need to deoxygenate the eluent or sample. The determination is made at +0.19 V
vs.
S.C.E. in pH 5.5 acetate buffer. The size of the blank signal is equivalent to about 0.01 µg ml
-1
of ascorbic acid and the signal is rectilinear up to about 60 µg ml
-1
. Chloride gives an oxidation signal at the mercury electrode but at a more positive potential and at the 1 µg ml
-1
level of ascorbic acid 1000 µg ml
-1
of chloride ion did not interfere.
Hydrodynamic voltammograms of dopamine [2-(3,4-dihydroxyphenyl)ethylamine] show a plateau distinct from that of ascorbic acid and the mercury oxidation cut-off. Calibration graphs obtained at +0.26 V
vs.
S.C.E. for dopamine are rectilinear in the range 0.1-60 µg ml
-1
. At +0.26 V chloride ion gives a signal approximately 1% of that of dopamine on a molar basis and interferes at higher ratios.