PULSE POLAROGRAPHIC DETERMINATION OF NITROGEN / 营养学报

A simple and rapid method was described for determining nitrogen content of a Kjeldahl digest by pulse polarography. The amount of sample needed was as small as 200mg. The digest was diluted and pipetted into a solution of formaldehyde in an acetate buffer. The hexamethylenetetramine produced by reaction between ammonia and formaldehyde was determined electrochemically at -0.9v.This method proved itself a better reproducibility. The recovery rate of nitrogen was 94.5% to 103.1%. Calibration curve of nitrogen in the range of 20 to 120 ?g/ml showed linear relation.Human milk and eleven different food-stuffs were analysed. There was no significant difference between the results by this method and Kjeldahl method.