Use of β-Cyclodextrin in the 2nd Derivative Simple Oscillovoltammetric Determination of L-Phenylalanine

In the base solution of 0.2 mol·L-1 NaOH,a reversible peak produced by β-cyclodextrin (β-CD) was found in the 2nd derivative oscillovoltammogram at -0.38 V (vs.SCE);and the peak height of cathodic branch was found to decrease with the increase of concentration of the inclusive complex formed between β-CD and L-phenylalanine.A linear relationship between the peak height and concentration of L-phenylalanine was found in the range of 2.5×10-6-4.5×10-5mol·L-1 (r=0.999 6),with a detection limit of 1.0×10-6mol·L-1.Based on this feature,a method of 2nd derivative oscillovoltammetric determination of L-phenylalanine was proposed.Test of precision was made with 5 determinations of L-phenylalanine at the concentration level of 8.0×10-5mol·L-1,giving the value of RSD of 3.1%.Results of recovery test were obtained with an average of 100.0%.Molar ratio of the inclusive complex formed between β-CD and L-phenylalanine was found to be 1 to 1 and the complex formation constant was 1.9×106.