IMPROVED METHOD FOR MANUAL, COLORIMETRY DETERMINATION OF TOTAL KJELDAHL NITROGEN USING SALICYLATE

A manual colorimetric method for analyzing ammonia or total Kjeldahl n itrogen is described that eliminates irreproducibility due to variabil ity in time between additions of reagents. Variability is negligible w hen trisodium phosphate is substituted in the buffer in place of the u sual disodium phosphate and sodium hydroxide. The resulting procedure is very simple and reliable and uses salicylate, which is the most env ironmentally acceptable of the alter native colorimetric reagents. Onl y two reagents are used, the first containing trisodium phosphate, sal icylate, and sodium nitroprusside and I;he second containing hypochlor ite, The accuracy of the method was verified in two ways: first, by an alyzing the digestate of three NBS standards and comparing the results to tl-ie NBS certified value; second, by analyzing the digestate of i n-house samples and comparing the results using this procedure to the results using two other colorimetric procedures.