INFLUENCE OF CATALYST, SAMPLE WEIGHT, AND DIGESTION CONDITIONS ON KJELDAHL NITROGEN

The influence of catalyst (containing K2SO4/Cu/Ti, K2SO4/Se, or Se alo ne), sample weight (0.2 or 0.4 g), and digestion blocks (Tecator DS 10 15-20 or Tecator DS 1016- 40) on the Kjeldahl-nitrogen (N) determinati on in pecan, com, and turnip leaves was evaluated. Mean Kjeldahl-N val ues were 1.84, 2.43, and 3.72 % for the pecan, com, and turnip samples , respectively, which were significantly higher (= 0.05) using K2SO4/S e as a catalyst, a 0.4 g aliquot of the sample, and a DS 1015-20 diges tion block. The magnitude of the differences due to catalyst, sample w eight, or digestion conditions did not affect the N diagnosis status w hen applying interpretative data for the selected crops. The higher st andard deviation (SD) for the turnip leaves compared to the pecan or c orn leaves may be due to a higher nitrate (NO3) level in the turnip le aves. Selected catalyst, sample weight, and digestion conditions did n ot affect the SD, and therefore any combination of these factors could be used to determine Kjeldahl N. A protocol using K2SO4/Cu/Ti, a 0.4 g sample-aliquot, and a digestion block equipped with condensers as th e fume control system tended to give the lowest variance, and to be th e most accurate and practical method.