1987 Volume 36 Issue 2 Pages 98-102
Methionine (Met) in blood serum was determined by HPLC with the electrochemical detector in which an anodically treated glassy carbon (GC) electorde was used. The result were compared with those obtained with an untreated GC electrode. The oxidation current of Met appeared at the potentials more positive than +1.2 V using an untreated GC electrode, but the peak height was very small and nonreproducible. The response of the electrode was improved by preanodizing for 2 min at +1.9 V in 0.2 M phosphate solution (pH 6.5). The peak current showed linearity from 1 ng to 500 ng at the potential of +1.7 V with 0.02 M phosphate buffer (pH 3.0) used as a mobile phase. Reproducibility of relative standard deviation was as small as 1.31% (n=20) in the continuous injection of 100 ng samples. The detection limit of Met with the treated electrode was 360 times lower than with the untreated electrode. The treated electrode could be used without any deterioration for one week, 8 h per day.
