Improved Method for Manual, Colorimetric Determination of Total Kjeldahl Nitrogen Using Salicylate

1996/01/01 by Raymond B. Willis, Michael E. Montgomery, Philip R. Allen · 18 citations
Chemical Engineering · Agricultural and Biological Sciences · #Odor and Emission Control Technologies #Animal Nutrition and Physiology #Composting and Vermicomposting Techniques

paper · doi:10.1021/jf950522b

Abstract

A manual colorimetric method for analyzing ammonia or total Kjeldahl nitrogen is described that eliminates irreproducibility due to variability in time between additions of reagents. Variability is negligible when trisodium phosphate is substituted in the buffer in place of the usual disodium phosphate and sodium hydroxide. The resulting procedure is very simple and reliable and uses salicylate, which is the most environmentally acceptable of the alternative colorimetric reagents. Only two reagents are used, the first containing trisodium phosphate, salicylate, and sodium nitroprusside and the second containing hypochlorite. The accuracy of the method was verified in two ways: first, by analyzing the digestate of three NBS standards and comparing the results to the NBS certified value; second, by analyzing the digestate of in-house samples and comparing the results using this procedure to the results using two other colorimetric procedures. Keywords: Total Kjeldahl nitrogen; ammonia; salicylate; NBS Standard tomato leaves; NBS Standard bovine liver; NBS Standard pine needles

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