Total Nitrogen In Fertilizers Research Articles

Determination of Kjeldahl Nitrogen in Fertilizers by AOAC Official MethodSM 978.02: Effect of Copper Sulfate as a Catalyst

In AOAC Official Method 955.04, Nitrogen (Total) in Fertilizers, Kjeldahl Method, fertilizer materials are analyzed using mercuric oxide or metallic mercury HgO or Hg) as a catalyst. AOAC Official Methods 970.02, Nitrogen (Total) in Fertilizers is a comprehensive total nitrogen (including nitrate nitrogen) method adding chromium metal. AOAC Official Method 978.02, Nitrogen (Total) in Fertilizers is a modified comprehensive nitrogen method used to measure total nitrogen in fertilizers with two types of catalysts. In this method, either copper sulfate or chromium metal is added to analyze for total Kjeldahl nitrogen. In this study, the part of AOAC Official Method 978.02 that is for nitrate-free fertilizer products was modified. The objective was to examine the necessity of copper sulfate as a catalyst for the nitrate-free fertilizer products. Copper salts are not environmentally friendly and are considered pollutants. Products such as ammonium sulfate, diammonium phosphate, monoammonium phosphate, urea-containing fertilizers such as isobutylene diurea (IBDU), and urea-triazone fertilizer solutions were examined. The first part of the study was to measure Kjeldahl nitrogen as recommended by AOAC Official Method 978.02. The second part of the study was to exclude the addition of copper sulfate from AOAC Official Method 978.02 to examine the necessity of copper sulfate as a catalyst in nitrate-free fertilizers, which was the primary objective. Our findings indicate that copper sulfate can be eliminated from the method with no significant difference in the results for the nitrogen content of the fertilizer products.

Abstracts of Nippon Dojo-Hiryogaku Zasshi (Japanese Journal of Soil Science and Plant Nutrition)

Abstracts of Nippon Dojo-Hiryogaku Zasshi (Japanese Journal of Soil Science and Plant Nutrition)

Determination of Ammoniacal and Total Nitrogen in Fertilizers by Ammonia-Selective Electrode

Abstract A method was studied for determining ammoniacal nitrogen in fertilizers by using an ammonia-selective electrode. Recovery for the method was evaluated with synthetic samples, and the method was also compared with the magnesium oxide method by analyzing 3 Magruder Check Samples. The method was adapted to determine total nitrogen in fertilizers by using the digestion procedure of the modified comprehensive nitrogen method and eliminating metal interferences by forming soluble complexes with tartaric acid. Recovery was evaluated and a comparison with AOAC official methods was made by performing a /-test on results for 3 Magruder Check Samples. Recoveries were good for determinations of both ammoniacal and total nitrogen by the method described, and results were not significantly different from those for AOAC methods.

Ammonia-Selective Electrode Determination of Nitrogen in Fertilizers

Abstract The official AOAC magnesium oxide method (MOM), 2.065, for determining ammoniacal nitrogen in fertilizers not containing urea was compared with an alternative ammonia-selective electrode method (ASEM-1). Likewise, the official AOAC Raney powder method (RPM), 2.063-2.064, for determining total nitrogen in fertilizers, except nitric phosphates containing nonsulfate S, was compared with an ammonia- selective electrode method (ASEM-2). Each comparison included 6 samples. For ammoniacal nitrogen determination, MOM and ASEM-1 showed equivalent precision, although significant statistical differences were obtained in average values for the majority of samples. For total nitrogen determination, RPM and ASEM-2 showed equivalent precision, although significant statistical differences were obtained in 3 samples. The AOAC official methods showed better accuracy than ASEM-1 and ASEM-2. However, the accuracy and precision of ASEM-1 for ammoniacal nitrogen is suitable for routine work.

Semiautomated Method for Total Nitrogen in Fertilizers

Abstract A semiautomated method (SAM) for total nitrogen in fertilizers has been developed which parallels the official first action semiautomated method for crude protein in feeds, 7.B05–7.B11. The SAM is simple, accurate, precise, flexible, rapid, and requires a minimum of laboratory space. Nitrate was reduced and organic nitrogen materials were digested by the sulfuric-salicylic acid chemistry in the block digestor. The nitrogen, as ammonia, in the digestate was determined automatically at the rate of 40 samples/hr with the automated ammonia analysis system. A small amount of CuSO4, (33 mg/sample) as the SAM digestion catalyst gave total recovery of organic nitrogen in fertilizer. Repeated analyses by the SAM and the AOAC official final action comprehensive nitrogen method (CNM) were made on Magruder fertilizer check samples, liquid and suspension fertilizers, and bulk blended commercial fertilizer materials. Average per cent nitrogen in liquid and suspension samples was higher by the SAM than by the CNM when sample weights similar to those for solid fertilizer were used. The precision of the SAM on liquids also agreed closely with that by the CNM. The only limitation of the semiautomated method was for fertilizer samples containing a Cl/NO3 ratio greater than 0.75 w/w. The SAM recoveries on 3 samples with very high Cl/NO3 ratios wert 94.1–99.1% of those by the CNM. Precision was also less than on any other samples. The average per cent nitrogen found for all experimental samples was 14.68 by the SAM and 14.67 by the CNM. The average relative standard deviation (RSD) for all 22 samples was 1.06% by the SAM and 0.74% by the CNM. When 3 samples with high Cl/NO3 ratios (>0.75) were excluded, the average per cent nitrogen was 15.77 (CNM) and 15.81 (SAM); respective RSDs were 0.68 and 0.65% for the SAM and CNM, respectively. A comparison of results on 405 commercial fertilizer samples by both methods showed an average difference (SAM — CNM) of + 0.017% nitrogen and aver age relative difference of 1.23%.

Zirconium Dioxide, A New Catalyst, in the Kjeldahl Method for Total Nitrogen Determination

Abstract The standard Kjeldahl method for the determination of total nitrogen in fertilizers, feeds, foods, and beverages has been modified to eliminate the use of mercuric oxide, which is poisonous to the environment. A new mixed catalyst, consisting of 0.60 g cupric sulfate and 0.20 g zirconium dioxide in combination or 0.70 g zirconium dioxide alone, is recommended to replace the 0.70 g or more of mercuric oxide used in all official macro Kjeldahl methods.

Mercury-Free Raney Catalyst Method for Total Nitrogen in Fertilizers

Abstract The original Raney catalyst powder method for total nitrogen was shown not to be applicable to nitric phosphates containing non-sulfate sulfur. Interference by the non-sulfate sulfur was eliminated by the addition of morin, a mordant dye, before the reduction. The method was modified further by omitting HgO, a possible pollutant, from the digestion and by shortening the digestion time. The modified method is highly rugged for a considerable range of fertilizer materials.

Total Nitrogen in Fertilizers

Abstract Automation and mercury pollution are discussed with the recommendation that copper be re-evaluated as a catalyst in Kjeldahl systems. An editorial change has been made in method 2.051 to increase the alkalinity of the digestion system

Missouri Automated Nitrogen Method (MANM) for Fertilizers

Abstract An automated spectrophotometric method, utilizing Technicon AutoAnalyzer modules, has been developed to determine total nitrogen in fertilizers containing only ammoniacal, nitrate , and urea nitrogen. This colorimetric system employs the Berthelot ammoniaphenate- hypochlorite reaction. A homogeneous chromous/titanous reduction system for the automatic reduction of nitrates was interfaced with the digestion unit and color development manifold, resulting in a total nitrogen system for fertilizers with an effective analysis r a t e of 20-25 samples/hr. A new sample retrieval system removes digested samples from the helix. The totally automated system was optimized to obtain t h e highest sensitivity for nitrogen. Data were compared for 458 samples analyzed by the automated method and the comprehensive nitrogen method (CNM), 2.053–2.054. The average difference between the 2 methods (MANM – CNM) was +0.04% nitrogen. The average relative difference was 1.12%. The average value for 140 samples of KNO3 primary standard analyzed by the MANM was 13.84% nitrogen (theoretical content 13.85%). The results of these standards ranged from 13.58 to 14.14% nitrogen and the standard deviation was 0.11%. The relative standard deviation was 0.80%. Of fertilizer samples received for analysis, less than 1% contained insoluble organic nitrogenous material which was unsuitable for analysis by the MANM. These few samples were not included in the statistical evaluation. The MANM is rapid, accurate, and precise and is a convenient and dependable automated method for the determination of total nitrogen in fertilizers containing only ammoniacal, nitrate , and urea nitrogen.

Comparison of the Automatic Dumas and Kjeldahl Methods for the Determination of Total Nitrogen in Fertilizers

Abstract Representative N-P-K fertilizers were analyzed for total nitrogen by the automatic Dumas method, using a catalyst-assisted combustion at 900°C, and by the macro Kjeldahl method. The precision and accuracy of both methods were considered to be adequate for this type of material and compared favorably. The automatic Dumas method gave slightly higher results than the Kjeldahl method and a statistical evaluation of the experimental data showed that the Kjeldahl method was generally more precise.

A New Approach to the Raney Catalyst Powder Method for Total Nitrogen in Fertilizers

Abstract Further study of the Raney catalyst powder method for the determination of nitrogen in fertilizers established conditions in which the commercial alloy containing 50% Ni and 50% Al was a more efficient reductant for nitrates than an experimental alloy that contained 10% Co. Errors in measurement were decreased, accuracy was increased, and time was saved by adding all the sulfuric acid and part of the potassium sulfate as a single dilute solution and heating the mixture immediately to promote the reduction. Changes in the amounts of reagents, including use of the contents of a Kcl-Pak without the polyethylene envelope, resulted in smoother and more effective Kjeldahl digestions. The method is “rugged” and is equally applicable to the refractory compound nicotinic acid, mixtures of nitrates and organic materials, and the simplest inorganic fertilizers. The time required for an analysis can be further shortened by using “Autopettes” for dispensing the standard acid and a “Titralyzer” for back titrations.

Total Nitrogen in Fertilizers

Abstract A three-laboratory collaborative study was made of the comprehensive nitrogen method and the new Raney catalyst powder method for total nitrogen in fertilizers. Both methods worked quite well and, with minor modifications, they should provide the basis for a broader collaborative stvidy to provide an official method for total nitrogen in fertilizer applicable to all samples. The limitations of method 2.045 are reviewed and a rephrasing of the official applications of the method is recommended. Further work is recommended toward adoption of a new method and possible deletions or change of status in current official methods.

How Rugged Are Our Nitrogen Methods?

Abstract Youden’s ruggedness test was made of two official methods and four more recent methods for the determination of total nitrogen in fertilizers containing nitrates. Among the variables tested were amounts of nitrogen and reductant, effect of chloride, and time of reaction of reductant. Official method 2.039 (reduced-iron) failed the test. In order of increasing standard deviation, the five methods that passed the test were the chromous reduction method, Raney-catalyst-powder method, official method 2.037 (salicylic acid), improved reduced-iron method, and the chromiumpowder method.

Determination of Total Nitrogen in Fertilizers

Abstract Five methods, AOAC 2.037, 2.039, modified reduced iron, chromium powder, and Raney nickel catalyst powder for the determination of total nitrogen in fertilizers, were submitted to collaborators for study. Twelve laboratories participated and completed the work. No one method was “best.” The modified reduced iron, chromium powder, and Raney nickel catalyst powder methods gave essentially equal results, but the chromium powder method is favored for case of operation and time required. However, if considerable organic matter and nitrate are present in a sample, satisfactory results may not be obtained. The analyst should select the official method best suited to the makeup of the sample. It is recommended that the chromium powder method he adopted as official, first action, and that study be continued with the modified reduced iron and Raney nickel catalyst methods, including helpful proposals in developing a method that may be applicable to all fertilizers.

The Use of Selenium as a Catalyser determing the total Nitrogen in Fertilizers.

The Use of Selenium as a Catalyser determing the total Nitrogen in Fertilizers.