Determination of Oxalic Acid by Differential Pulse Polarography

A differential pulse polarographic method for determination of oxalic acid was proposed.In a base solution of 0.05 mol·L-1 potassium hydrogen phthalate and 1.0 mol·L-1 Li2SO4,and when differential pulse polargoraphic scanning was carried out at the potentials of -1.80 V to -1.20 V (vs.Ag/AgCl),3 significant polarographic reduction peaks were observed at the potentials of (Ep1) -1.29 V,(Ep2) -1.54 V and (Ep3) -1.76 V.To avoid the interference of the reduction product of oxalic aicd,i.e.the glyoxalic acid at Ep3,and the mutual interference at Ep2 and Ep3,the potential of -1.29 V (Ep1) was chosen for the determination of oxalic acid.Linear relationship between values of peak current and concentration of oxalic acid was shown by the linear regression equation y=-24.080 6+37.344 3 x (r=0.997 9).Five portions of standard solutions containing 9.018 g·L-1 oxalic acid were determined by the proposed method to test for precision,value of RSD (n=5) found was 0.23%.Recovery was tested by the standard addition method,giving recovery in the range of 99.6%-100.3%.