Journal articles: 'Kjeldahl method'

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Miller, Eric L., Anthony P. Bimbo, Stuart M. Barlow, Berni SHeridan, L. B. W. Burks, T. Barrins, M. Bassompierre, et al. "Repeatability and Reproducibility of Determination of the Nitrogen Content of Fishmeal by the Combustion (Dumas) Method and Comparison with the Kjeldahl Method: Interlaboratory Study." Journal of AOAC INTERNATIONAL 90, no. 1 (January 1, 2007): 6–20. http://dx.doi.org/10.1093/jaoac/90.1.6.

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Abstract Ten fishmeal samples (hidden duplicates of 4 meals plus 2 high-protein meals as a Youden pair), tryptophan, and nicotinic acid were analyzed by 18 laboratories using the Dumas method. Thirteen of the laboratories also analyzed the same 12 samples using their current Kjeldahl method. Recoveries (± sR) of tryptophan and nicotinic acid were 99.3 ± 1.04 and 98.8 ± 2.11 by Dumas and 97.1 ± 3.03 and 74.6 ± 26.76 by Kjeldahl. The Dumas method gave significantly greater values (P < 0.001) than the Kjeldahl method. For fishmeals, Kjeldahl N 0.989 of Dumas N (P < 0.001). A similar proportionate difference (0.984 of Dumas N) was observed with tryptophan. Most laboratories failed to determine nicotinic acid correctly by Kjeldahl. For fishmeals, the relative standard deviations for repeatability and reproducibility were for Dumas 1.48 and 2.01% and Kjeldahl 1.62 and 2.37%, respectively. A single analysis conducted in 2 laboratories should not differ by more than 5.63% of the mean value when measured by Dumas or by more than 6.64% by Kjeldahl. It is concluded that with fishmeal, Dumas gives a more reliable measure of organic nitrogen than Kjeldahl, and, therefore, Dumas should be the method of choice.

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Lynch, Joanna M., and David M. Barbano. "Kjeldahl Nitrogen Analysis as a Reference Method for Protein Determination in Dairy Products." Journal of AOAC INTERNATIONAL 82, no. 6 (November 1, 1999): 1389–98. http://dx.doi.org/10.1093/jaoac/82.6.1389.

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Abstract Measurement of total nitrogen by Kjeldahl analysis is the historical reference method for determination of the protein content of dairy products and is used for both calibration and validation of alternative methods for protein determination. Accurate evaluation of alternative methods is not possible if there is large uncertainty regarding the reference values. When Kjeldahl analysis is used to establish reference values, the performance of the Kjeldahl testing must be verified and within established expectations. Advice is given for Kjeldahl system optimization, evaluation of test results, and troubleshooting. Techniques for successful Kjeldahl nitrogen analysis of dairy products other than milk are discussed.

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Hach, Clifford C., Brian K. Bowden, Alan B. Kopelove, and Scott V. Brayton. "More Powerful Peroxide Kjeldahl Digestion Method." Journal of AOAC INTERNATIONAL 70, no. 5 (September 1, 1987): 783–87. http://dx.doi.org/10.1093/jaoac/70.5.783.

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Abstract Enhanced ammonia recovery and a simplified method are described for a rapid Kjeldahl digestion using sulfuric acid and hydrogen peroxide as the sole digestion reagents. This micro procedure uses a Vigreux fractionating head fitted to a 100 mL volumetric flask and a hot plate with a solid-state controller. Continuous-flow peroxide addition is controlled by a capillary funnel, and fumes are evacuated through a side-arm vent leading to a water aspirator. Complete recovery of nitrogen from the refractory compound, nicotinic acid, is obtained with less than 10 min digestion. The described method reduces digestion time by 25-50% over the open-manifold peroxy method. A digestibility index (DI), scaled 0-10, establishes the difficulty of digestion for each sample and assigns values to compounds. A useful tool for determining the minimal amount of reagent and digestion time required, the DI assigns zero for compounds not needing digestion and 10 for nicotinic acid. Digested samples obtained from the described method are suitable for direct colorimetric analysis of many elements in addition to Kjeldahl nitrogen. Distillation of the digested sample is not required

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Tate, Donald F. "Determination of Nitrogen in Fertilizer by Combustion: Collaborative Study." Journal of AOAC INTERNATIONAL 77, no. 4 (July 1, 1994): 829–39. http://dx.doi.org/10.1093/jaoac/77.4.829.

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Abstract Fourteen laboratories participated in a collaborative study to compare abilities of AOAC modified copper catalyst Kjeldahl method, 978.02, and the generic combustion method, 990.03, to analyze the nitrogen content of fertilizer materials. Combustion analyses are more time efficient, more accurate, and less hazardous than Kjeldahl analyses. There were 3 different types of instrumentation involved in the collaborative study: (1) Leco FP-428 Nitrogen Determinator; (2) Perkin-Elmer 2410 Series II Nitrogen Analyzer; (3) Carlo-Erba 1500 Series II Nitrogen Analyzer. Thirty samples of fertilizer containing 1–67% N included 2 ACS grade standard materials: ammonium nitrate, theory 35.00% N; and dicyandiamide, theory 66.64% N. A diammonium phosphate and urea mixture (3 + 1 ; 1.0 mm grind) and 2 ACS grade standard materials of ammonium nitrate and ammonium sulfate were supplied for repetitive combustion analyses. Overall method performance of the combustion method was at least as good as the modified Kjeldahl method. Repeatability standard deviation (Sr) values for the combustion method ranged from 0.09 to 0.34 vs the modified Kjeldahl method range of 0.06–0.49; reproducibility standard deviation (SR) values for the combustion method ranged from 0.13 to 1.07 vs the range of 0.09–3.57 for the modified Kjeldahl method. The grand mean was 20.78% for the combustion method, and 20.79% for the modified Kjeldahl method using various fertilizers. The average ranges of sr and SR for the methods were, respectively, 0.17 and 0.29 for the combustion method, and 0.19 and 0.54 for the modified Kjeldahl method. The method was adopted first action by AOAC INTERNATIONAL.

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Qi, Ning Li, Pu Wang Li, Xian Hai Zeng, Hong Hai Huang, Zi Ming Yang, and Xiao Gong. "Comparison of Kjeldahl and the Elemental Analysis Methods for Determination of Nitrogen Content in Raw Natural Rubber." Advanced Materials Research 815 (October 2013): 722–26. http://dx.doi.org/10.4028/www.scientific.net/amr.815.722.

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The nitrogen in raw natural rubber is mainly derived from crude protein of latex. In this study, the nitrogen content of six kinds of raw natural rubber was analyzed for evaluating Kjeldahl and elemental analysis methods. The nitrogen content ranged from 0.43% to 0.66% for Kjeldahl methods and from 0.45% to 0.75% for elemental analysis method. There was no significant difference between the two methods. The coefficient of variation was below 1%. The data of nitrogen content showed a simple linear correlation (r=0.9937) between the two methods. It was concluded that the elemental analysis method could replace Kjeldahl method in nitrogen analysis of raw natural rubber.

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Marcia King, Brink, Sebranek Joseph G., C. Anthony, P. Coleman, B. Cottingham, R. Culmo, R. Curtis, et al. "Combustion Method for Determination of Crude Protein in Meat and Meat Products: Collaborative Study." Journal of AOAC INTERNATIONAL 76, no. 4 (July 1, 1993): 787–93. http://dx.doi.org/10.1093/jaoac/76.4.787.

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Abstract Twelve laboratories participated in a collaborative study to compare a combustion method with the AOAC mercury catalyst Kjeldahl method (928.08) for the determination of crude protein in meat and meat products. Three different combustion instruments were used; consequently, the combustion method for this study is written in generic terms describing the principle, the apparatus specifications, and the performance requirements needed. Fifteen sample pairs were used for the study; each pair consisted of the same commercial meat product from each of 2 different manufacturers. Protein content of all samples ranged from about 10 to 20%. In addition, nicotinic acid and lysine monohydrochloride were used as standards to assess combustion equipment performance. All laboratories and all instruments performed the combustion method satisfactorily on the basis of results for the standards. For the meat samples, repeatability standard deviations (sr) ranged from 0.11 to 0.40 for the Kjeldahl method and from 0.12 to 0.41 for the combustion method; the repeatability relative standard deviations (RSDr) ranged from 0.82 to 2.41% and from 0.60 to 2.23% for the Kjeldahl and combustion methods, respectively. Reproducibility standard deviations (SR) ranged from 0.20 to 0.49 for the Kjeldahl method and from 0.18 to 0.46 for the combustion method, whereas the reproducibility relative standard deviations (RSDR) ranged from 1.59 to 2.84% for the Kjeldahl method and from 1.32 to 3.35% for the combustion method. Overall grand means were 15.59% protein for the Kjeldahl method and 15.75% protein for the combustion method. The combustion method was adopted first action by AOAC International.

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Khanizadeh, Shahrokh, Deborah Buszard, and Constantinos G. Zarkadas. "Comparison of Three Methods for Calculating Protein Content in Developing Apple Flower Buds." Journal of AOAC INTERNATIONAL 75, no. 4 (July 1, 1992): 734–37. http://dx.doi.org/10.1093/jaoac/75.4.734.

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Abstract Three methods (Kjeldahl, sulfuric acid-hydrogen peroxide, and summation of amino acid content) for determining and calculating the protein content of apple flower buds were compared. Quantitation of protein content based on summation of amino acids appears to be the most accurate method. A new nitrogen:protein conversion factor (5.51) was calculated based on total amino acid analysis. This new conversion factor could replace the conventional 6.25 factor for estimating total protein content of apple flower bud by the Kjeldahl method. However, Kjeldahl is not an accurate method for estimating protein content in apple flower bud tissue, regardless of the conversion factor, and probably would not be a good method for estimation of protein in other plant species.

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Sachen, Robert W., and Nancy J. Thiex. "Effect of Sample Introduction and Atmospheric Blank on Determination of Nitrogen (Crude Protein) by Combustion." Journal of AOAC INTERNATIONAL 80, no. 1 (January 1, 1997): 14–19. http://dx.doi.org/10.1093/jaoac/80.1.14.

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Abstract To reduce analysis time, reagent use, and chemical waste, existing Kjeldahl methods for crude protein were converted to combustion methods. When validating the combustion method for various samples, a high bias for the combustion method compared with the Kjeldahl method was apparent for high-fiber samples. The bias was sample dependent, varying from 0.15 to 1.38% crude protein for hay and corn silage samples. The bias was repeatable among 3 laboratories using identical instruments. Studies showed the bias was related to uncorrected atmospheric blanks. Various means to correct for the blank were studied, including pelleting of sample under high pressures to remove atmospheric nitrogen. Pelleting samples at a pressure of >1000 lbs provides combustion crude protein values consistent with Kjeldahl values.

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Hach, Clifford C., Scott V. Brayton, and Alan B. Kopelove. "A powerful Kjeldahl nitrogen method using peroxymonosulfuric acid." Journal of Agricultural and Food Chemistry 33, no. 6 (November 1985): 1117–23. http://dx.doi.org/10.1021/jf00066a025.

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10

Anglov, T., I. M. Petersen, and J. Kristiansen. "Uncertainty of nitrogen determination by the Kjeldahl method." Accreditation and Quality Assurance 4, no. 12 (December 2, 1999): 504–10. http://dx.doi.org/10.1007/s007690050423.

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11

Soon, Y. K., and Y. P. Kalra. "SHORT COMMUNICATION: A comparison of plant tissue digestion methods for nitrogen and phosphorus analyses." Canadian Journal of Soil Science 75, no. 2 (May 1, 1995): 243–45. http://dx.doi.org/10.4141/cjss95-034.

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Four variations of the Kjeldahl digestion were compared with a H2SO4–H2O2 digestion for N and P analysis, and a microwve digestion method and a dry ashing procedure for P analysis. One Kjeldahl variant using a Na2SO4–Se catalyst was found to be suitable for multi-element analysis while doubling the per diem output of digestions compared with the H2SO4–H2O2 method, provided that P was analyzed by the molybdivanadate (MV) procedure. Key words: Kjeldahl digestion, nitrogen, phosphorus, plant tissue

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12

Sweeney, Rose A., and Paul R. Rexroad. "Comparison of LECO FP-228 "Nitrogen Determinator" with AOAC Copper Catalyst Kjeldahl Method for Crude Protein." Journal of AOAC INTERNATIONAL 70, no. 6 (November 1, 1987): 1028–30. http://dx.doi.org/10.1093/jaoac/70.6.1028.

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Abstract The LECO FP-228 "Nitrogen Determinator" was compared with the AOAC copper catalyst Kjeldahl method, 7.033-7.037, for the determination of crude protein in feed materials. The completely microprocessor- controlled instrument determines nitrogen by measuring the nitrogen gas following combustion of the sample; it was easy to operate and broadly applicable. A wide variety of feed materials of various nitrogen levels were analyzed in one mixed sequence. Results were precise, accurate, and rapid. Analysis time for one sample was approximately 3 min. Fourteen samples containing 2.5-15.5% N were selected for study and consisted of meals, grains, forages, and standard organic materials. The overall mean for the 14 samples by the LECO combustion method was 8.61% N compared with an overall mean of 8.58% N for the AOAC Kjeldahl method. Within-sample standard deviations for the LECO combustion method ranged from 0.013 to 0.052% N with a pooled standard deviation (SD) of 0.033% N for the 14 samples. Standard deviations for the AOAC Kjeldahl method ranged from 0.006 to 0.035% N with a pooled SD of 0.022% N. Combined average recovery of nitrogen from tryptophan, lysine- HC1, and EDTA determined by the LECO combustion method was 99.94% compared to 99.88% determined by the AOAC Kjeldahl method.

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Sweeney, Rose A. "Generic Combustion Method for Determination of Crude Protein in Feeds: Collaborative Study." Journal of AOAC INTERNATIONAL 72, no. 5 (September 1, 1989): 770–74. http://dx.doi.org/10.1093/jaoac/72.5.770.

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Abstract Nine laboratories participated in a collaborative study on determination of crude protein in animal feeds to compare a generically described combustion method with the AOAC mercury catalyst Kjeldahl method (7.015). The combustion method was written in general terms of method principle, apparatus specifications, and performance requirements. The sample set comprised closely matched pairs of feed ingredients and mixed products ranging from 10 to 90% protein. Ten pairs ground to 0.5 mm were the focus of the study; 4 pairs were ground to 1.0 mm for comparison. Nicotinic acid and lysine monohydrochloride were included as standards. Collaborators were instructed to report their results for performance checks using materials supplied. Only one laboratory failed to meet the proposed limits. Seven laboratories used the LECO Model FP-228 analyzer and 2 used the LECO CHN 600 analyzer. For the 0.5 mm pairs, repeatability standard deviations (sr) ranged from 0.09 to 0.58 for the Kjeldahl method and from 0.14 to 0.33 for the combustion method, with a pooled sr value of 0.28 and relative standard deviation (RSDr) of 0.59%. Reproducibility standard deviations (SR) ranged from 0.23 to 0.86 (Kjeldahl) and from 0.30 to 0.61 (combustion), with a pooled sR value of 0.52 and RSDR of 1.10%. Grand means for the samples ground to 0.5 mm were 47.65% protein by the combustion method and 47.41% protein by the Kjeldahl method. For samples ground to 1.0 mm, corresponding values were 31.82 and 31.50% protein. The generic combustion method has been approved interim official first action.

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Devani, Muljibhai B., Chamanlal J. Shishoo, Shailesh A. Shah, and Bhanubhai N. Suhagia. "Spectrophotometric Method for Microdetermination of Nitrogen in Kjeldahl Digest." Journal of AOAC INTERNATIONAL 72, no. 6 (November 1, 1989): 953–56. http://dx.doi.org/10.1093/jaoac/72.6.953.

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Abstract A new spectrophotometric method for the determination of nitrogen in Kjeldahl digest has been developed. The method is based on the reaction of ammonia with acetylacetone-formaldehyde reagent in aqueous medium to yield yellow 3,5-diacetyl- 1,4-dihydrolutidine with a characteristic absorption maxima at 412 nm. The effect of several experimental variables on the determination of nitrogen was studied. The method was suitable for determination of nitrogen in acidic medium without interference from the usual catalysts employed for the digestion in Kjeldahl method. Lambert-Beer’s law is obeyed in the concentration range of 0.5-6.0 ng nitrogen/mL in the reaction mixture. The molar absorptivity in terms of nitrogen was 1.4 X 103L mol-1 cm-1. The standard deviation and relative standard deviation were ±0.0447 and ±0.896% (n = 10), respectively. The method is simple, rapid, and precise. A variety of carbocyclic and heterocyclic nitrogen compounds have been analyzed for nitrogen content. The results are comparable with those obtained by AOAC method, 47.021.

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Barbano, David M., Joanna M. Lynch, and J. Richard Fleming. "Direct and Indirect Determination of True Protein Content of Milk by Kjeldahl Analysis: Collaborative Study." Journal of AOAC INTERNATIONAL 74, no. 2 (March 1, 1991): 281–88. http://dx.doi.org/10.1093/jaoac/74.2.281.

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Abstract Currently, the reference procedure for determination of the "protein" content of milk is based on measurement of the total nitrogen content of milk by the Kjeldahl method (AOAC method, 920.105). About 6% of the total nitrogen content of milk Is nonprotein nitrogen. Therefore, total nitrogen multiplied by the conversion factor 6.38 overestimates the true protein content of milk on average by about 6%. In the present study, new direct and Indirect methods were developed for measurement of the true protein content of whole milk by Kjeldahl nitrogen determination. Both new methods are sample preparation procedures used to fractionate the nitrogen-containing compounds In milk prior to measurement of the nitrogen content of these fractions by Kjeldahl analysis. The collaborative study consisted of 9 pairs of blind duplicate milk samples that were analyzed for total nitrogen, nonprotein nitrogen, and protein nitrogen by each of 10 laboratories. Both methods for true protein measurement (direct and Indirect) gave acceptable statistical performance characteristics and good agreement between methods. The new direct method requires about half the laboratory analysis work of the indirect method (i.e., total minus nonprotein nitrogen). The methods have been adopted official first action by AOAC as (1) a new method for nonprotein nitrogen determination in milk, (2) a new method (direct) for determination of protein nitrogen content of milk, and {3) an alternative method (indirect) for determination of protein nitrogen content of milk.

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Kuchnir, G. V., Т. R. Levytzkiy, G. P. Ryvak, L. V. Kurylas, O. M. Vilha, and G. Y. Fedor. "Характеристика сучасних методів визначення сирого протеїну у кормах та рослинній сировині." Scientific Messenger of LNU of Veterinary Medicine and Biotechnologies 19, no. 82 (November 6, 2017): 97–100. http://dx.doi.org/10.15421/nvlvet8220.

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Todays in laboratory and manufacturing practice of veterinary medicine of Ukraine, for the detertimations of raw protein in feed and in plant raw are used as classic and as modern methods depending from the aim and the task of research. Thats why the article describes the modern methods of the determination of content of nitrogen and the calculation of raw protein in feeds for animals and in plant materials, in particular, photometric, classical – Kjeldahl method, modern – Dumas and spectrometric methods (the method of infrared spectrometry in the near range (NIR-spectrometry). Despite of the facts, that the Kjeldahl method remains generally accepted in the determination of the protein and is most often used in research, but the modern methods – the Dumas method and NIR-spectrometry are widely adopted in laboratory practice. The main advantage of these methods is the speed of the analysis (the one definition takes only a few minutes), practically there is no sample preparation, and the most important is that the toxic chemicals and catalysts are not used.Thus, despite the fact that the Kjeldahl method remains generally accepted in the determination of the protein, and it is most frequently used in research, but modern methods, the Dumas method and NIR-spectrometry, are widely implemented in laboratory practice. The main advantage of these methods is the speed of conducting the analysis (one definition only takes a few minutes), there is practically no sample preparation, and most importantly, toxic chemicals and catalysts are not used.

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Wiles, Peter G., Ian K. Gray, Roger C. Kissling, C. Delahanty, J. Evers, K. Greenwood, K. Grimshaw, et al. "Routine Analysis of Proteins by Kjeldahl and Dumas Methods: Review and Interlaboratory Study Using Dairy Products." Journal of AOAC INTERNATIONAL 81, no. 3 (May 1, 1998): 620–32. http://dx.doi.org/10.1093/jaoac/81.3.620.

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abstract The Kjeldahl and Dumas (combustion) methods were compared in 11 laboratories analyzing samples of milk, skim milk powder, whole milk powder, whey protein concentrate, infant formula, casein, caseinate, 2 reference compounds (glycine and EDTA), and a secondary reference skim milk powder. The comparison was conducted by using international standards where applicable. Overall means were 8.818 g N/100 g by the Kjeldahl method and 8.810 g N/100 g by the Dumas method. No evidence was found for a consistent bias between methods that may be of concern in the trading of dairy produce. A review of more than 10 related trials revealed a lack of consensus in the bias between the 2 methods, suggesting that differences in methodology and sources of systematic error may be contributors. For samples containing >2 g N/100 g, the Dumas relative repeatability and reproducibility standard deviations were consistently about 0.35 and 0.75%, respectively, whereas the corresponding Kjeldahl values declined generally with N content and were significantly larger. The Dumas precision characteristics may be due to the dominance of Leco analyzers in this trials, and in most other recent trials, rather than an inherent method attribute. Protein determination methods for dairy products need to be reviewed and updated. The Dumas method needs Codex Alimentarius status as a recognized test method.

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Pokhylko, S. Yu, S. V. Schwartau, V. V. Pochynok, L. M. Mykhalska, O. M. Dugan, and B. V. Morgun. "Complex analysis of total protein content in bread wheat containing GPC-B1 gene from Triticum turgidum SSP. dicoccoides." Visnik ukrains'kogo tovaristva genetikiv i selekcioneriv 15, no. 1 (October 1, 2017): 52–57. http://dx.doi.org/10.7124/visnyk.utgis.15.1.712.

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Aim. The purpose of our study was to determine the content of total protein in the F5 generation grains, the carriers of the Gpc-B1 gene from Triticum turgidum ssp. dicoccoides by two methods, which in turn would confirm the successful expression of the Gpc-B1 gene in the genetic environment of bread winter wheat. Methods. Determination of protein content was carried out by Kjeldahl method and by infrared spectrometry (NIR) method. Results. The 44 hybrid lines that are homozygous for the Gpc-B1 gene from T. turgidum ssp. dicoccoides have been analyzed. It has been established that for both methods, the average content of protein in the grain of hybrid lines is 14 % higher in comparison to the original Kuyalnik variety. Particular attention should be paid to the line number 10, 12 and 35 in which the content of protein exceeds 15 % by the method of Kjeldahl. Conclusions. The obtained results indicate that the gene Gpc-B1 from the wild relative in the new genetic environment of the highly productive registered wheat cultivar Kuyalnik has been functioning and has a positive effect on the accumulation of total protein in grains.Keywords: biofortification, protein content, Triticum aestivum, Gpc-B1 gene, Kjeldahl and NIR methods.

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Mulvaney, R. L., F. Azam, S. N. Stein, and F. W. Simmons. "Chloride interference in total nitrogen analysis by the Kjeldahl method." Communications in Soil Science and Plant Analysis 23, no. 15-16 (September 1992): 1805–13. http://dx.doi.org/10.1080/00103629209368705.

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Konstantinides, F. N., K. A. Boehm, W. J. Radmer, M. C. Storm, J. T. Adderly, S. A. Weisdorf, and F. B. Cerra. "Pyrochemiluminescence: real-time, cost-effective method for determining total urinary nitrogen in clinical nitrogen-balance studies." Clinical Chemistry 34, no. 12 (December 1, 1988): 2518–20. http://dx.doi.org/10.1093/clinchem/34.12.2518.

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Abstract Total urinary nitrogen (TUN) determinations for nitrogen-balance studies were traditionally performed by the Kjeldahl method, but this method is laborious, hazardous, prone to error, and no longer widely available in most clinical laboratories. During the last several decades, urinary urea nitrogen (UUN) determinations have replaced TUN as an index of urinary nitrogen excretion in many clinical laboratories, owing to its ease of determination, decreased cost, and wide availability. However, the validity of using UUN for estimating nitrogen loss has been questioned in many disease states, owing to wide variations in the proportional amount of urea found in TUN. Chemiluminescence has been proposed as an alternative to the Kjeldahl method for TUN. TUN values obtained from 24-h urine collections measured by both micro-Kjeldahl (x) and Pyrochemiluminescence (y) (Antek Instruments, Inc.) techniques were comparable by linear regression analysis: n = 97; r = 0.996; r2 = 0.992; y = 1.048x - 0.606; P less than 0.001. Automated induction of samples and calculation of results allows up to 42 samples to be run unattended. This dramatically reduces labor and overall costs for TUN determinations, while providing a more accurate and economical assessment of nitrogen excretion than UUN in a clinical setting.

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Dieckow, Jeferson, João Mielniczuk, Heike Knicker, Cimélio Bayer, Deborah Pinheiro Dick, and Ingrid Kögel-Knabner. "Comparison of carbon and nitrogen determination methods for samples of a Paleudult subjected to no-till cropping systems." Scientia Agricola 64, no. 5 (October 2007): 532–40. http://dx.doi.org/10.1590/s0103-90162007000500011.

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Organic carbon (C) concentration evaluated by the Walkley-Black method, and total nitrogen(N)concentration determined by Kjeldahl method, were compared with corresponding results of C and N concentrations obtained through the dry combustion method (Elementar Vario EL analyzer), using samples of ten soil layers down to the depth of 107.5 cm of a kaolinitic Typic Paleudult (220-418 g clay kg-1 along the profile) subjected to no-till cropping systems [fallow bare soil, pigeon pea (Cajanus cajan L. Millsp.) plus maize, and lablab (Lablab purpureum L. Sweet) plus maize]. A close correlation (R² > 0.96) was observed between the C results of the Walkley-Black and dry combustion methods, but a correction was suggested to be applied to C results of Walkley-Black (C = 1.05C W.Black + 0.47). A close correlation (R² > 0.96) was also found between results of Kjeldahl-N and dry combustion-N, but no correction was necessary to be applied. The relationships between results of Walkley-Black and dry combustion and between results of Kjeldahl and dry combustion did not change among soil samples from different management systems, in disagreement to findings of a previous study where results of analytical C recovery were influenced by samples from different managements, supposedly because changes in lability or recalcitrance of organic matter might have affected the wet combustion reactions. A poor correlation (R² = 0.42) was found between the C:N ratios based on Walkley-Black and Kjeldahl analysis and the C:N ratios based on dry combustion analysis. The methods for C and N determination did not affect the interpretation of the effects of management systems on soil C and N stocks.

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Keller, R. P., and M. C. Neville. "Determination of total protein in human milk: comparison of methods." Clinical Chemistry 32, no. 1 (January 1, 1986): 120–23. http://dx.doi.org/10.1093/clinchem/32.1.120.

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Abstract We evaluated four spectrophotometric methods for suitability in determining total protein in human milk samples. Results were compared with those by an established method for the determination of total nitrogen (micro-Kjeldahl). Values for total protein by all four methods significantly correlated with micro-Kjeldahl. For the biuret assay, Lowry-Peterson assay, Bio-Rad Coomassie Blue assay, and Pierce BCA assay, the correlation coefficients were 0.96, 0.97, 0.89, 0.99, respectively. We also assessed the sensitivity of each assay to several purified human milk proteins. The Pierce BCA assay showed the least difference in values among different types of protein. For this reason, and because it showed the greatest precision (with acceptable constant and proportional error), we recommend the BCA method.

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Bellomonte, Guido, Anna Costantini, and Stefania Giammarioli. "Comparison of Modified Automatic Dumas Method and the Traditional Kjeldahl Method for Nitrogen Determination in Infant Food." Journal of AOAC INTERNATIONAL 70, no. 2 (March 1, 1987): 227–29. http://dx.doi.org/10.1093/jaoac/70.2.227.

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Abstract This study compares 2 methods for determining nitrogen and protein in various types of infant food: the Kjeldahl method, developed in 1883, which is time consuming and labor intensive, and a newer, automatic method, based on the Dumas method. In each category of infant food considered, the results obtained from both methods are shown to be comparable; however, the modified Dumas method is quicker, easier, and does not pollute the laboratory environment

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Lynch, Joanna M., David M. Barbano, and J. Richard Fleming. "Determination of the Total Nitrogen Content of Hard, Semihard, and Processed Cheese by the Kjeldahl Method: Collaborative Study." Journal of AOAC INTERNATIONAL 85, no. 2 (March 1, 2002): 445–55. http://dx.doi.org/10.1093/jaoac/85.2.445.

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Abstract The objective of this collaborative study was to determine interlaboratory performance statistics for a modified and optimized version of AOAC Method 920.123 for the determination of the total nitrogen content of hard, semihard, and processed cheese by Kjeldahl analysis. Details included addressing the issues of material homogeneity, test portion size (1 g), quantitative transfer (weighing on to filter paper), ensuring system suitability (nitrogen recoveries), and using AOAC Method 991.20 as the basis for nitrogen analysis. Fifteen laboratories tested 18 pairs of blind duplicate cheese materials with a crude protein content between 18 and 36%. Materials represented hard, semihard, and processed commercial cheeses with a wide range of composition. Statistical performance parameters expressed as crude protein (nitrogen × 6.38), g/100 g, with invalid and outlier data removed were mean = 26.461, repeatability standard deviation (Sr) = 0.111, reproducibility standard deviation (SR) = 0.153, repeatability relative standard deviation (RSDr) = 0.42%, reproducibility relative standard deviation (RSDR) = 0.58%, repeatability (r) = 0.312, and reproducibility (R) = 0.428. The interlaboratory study results were acceptable and comparable to those for the milk Kjeldahl nitrogen method on a relative nitrogen basis. The Study Directors recommend that this modified method for the determination of total nitrogen in hard, semihard, and processed cheese by Kjeldahl analysis be adopted First Action as an improved method to replace Method 920.123.

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Lynch, Joanna M., David M. Barbano, and J. Richard Fleming. "Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study." Journal of AOAC INTERNATIONAL 81, no. 4 (July 1, 1998): 763–74. http://dx.doi.org/10.1093/jaoac/81.4.763.

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Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

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Watkins, Kevin L., Trygve L. Veum, and Gary F. Krause. "Total Nitrogen Determination of Various Sample Types: A Comparison of the Hach, Kjeltec, and Kjeldahl Methods." Journal of AOAC INTERNATIONAL 70, no. 3 (May 1, 1987): 410–12. http://dx.doi.org/10.1093/jaoac/70.3.410.

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Abstract Conventional Kjeldahl analysis with modifications, Kjeltec analysis with block digestion and semiautomated distillation, and the Hach method for determining nitrogen (N) were compared using a wide range of samples. Twenty different sample types were ground and mixed. Each sample type was divided into 5 subsamples which were analyzed for N by each of the 3 methods. In each sample type, differences (P < 0.05) were detected among the 3 N determination methods in 5 of the 20 N sources analyzed. The mean N content over all 20 samples was higher with Kjeldahl analysis (P < 0.05) than with Kjeltec, while Hach analysis produced intermediate results. Results also indicated that the Hach procedure had the greatest ability to detect differences in N content among sample types, being more sensitive than either other method (P < 0.05).

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NOAMAN, M. M., G. A. TAYLOR, and C. F. MCGUIRE. "ESTIMATION OF PROTEIN CONCENTRATION IN THREE PLANT PARTS AT FOUR GROWTH STAGES IN WHEAT BY NEAR INFRARED REFLECTANCE." Canadian Journal of Plant Science 68, no. 1 (January 1, 1988): 217–20. http://dx.doi.org/10.4141/cjps88-024.

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Near Infrared Reflectance was examined to be used as a technique of estimating protein concentration in the head, flag leaf, and peduncle of Newana, hard red spring wheat (Triticum aestivum L.) at four growth stages. The plant samples were taken from a field experiment including three N levels. The standard Kjeldahl method was used to estimate protein concentration in these plant parts. Protein concentration in these samples ranged from 2.7% in the peduncle to 16.7% in the flag leaf. The NIR was calibrated using these plant parts. Using 3 of 19 available filters the R2 for the calibration between Kjeldahl and NIR was 0.98. The validity of the NIR calibration was tested using an independent set of plant parts of winter wheat taken at three growth stages. The r2 obtained between Kjeldahl and NIR was highly significant. It was concluded that NIR provides an accurate, rapid, and economical technique for estimating protein concentration in aerial plant tissues. This should facilitate the screening of wheats for genotypic variation in aerial plant protein.Key words: Wheat, Kjeldahl N, protein translocation, protein estimation, Triticum aestivum L.

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Lou, Jiangfei, Jinfang Zhang, Shengxiang Xu, Dan Wang, and Xuerong Fan. "New Method to Evaluate the Crosslinking Degree of Resin Finishing Agent with Cellulose Using Kjeldahl Method and Arrhenius Formula." Processes 9, no. 5 (April 27, 2021): 767. http://dx.doi.org/10.3390/pr9050767.

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In anti-wrinkle finishing, the crosslinking degree of fabric is mainly determined by wrinkle recovery angle, stiffness, and viscosity, these indicators can only reflect the finishing effect from a macro perspective, which cannot reflect whether the crosslinking is sufficient, and it is difficult to quantify the crosslinking degree. In this paper, we combined the Kjeldahl method with the Arrhenius formula and proposed a method to analyze the crosslinking degree of dimethyloldihydroxyethyleneurea (two-dimensional (2D) resin) with cotton cellulose during delayed-cure finishing for the first time. The nitrogen content of completed fabrics during storage was measured by the Kjeldahl method, and the reaction rate equation of the 2D resin and cellulose under normal temperature conditions was calculated. The results show that the nitrogen content is more suitable to indicate the crosslinking degree, and the apparent activation energy was 28.271 kJ/mol and the pre-finger factor was 0.622, which indicated that the 2D resin was prone to cross-linking with cotton fabrics during storage. During long-term storage, the relative errors between the calculated and measured values of the nitrogen content were within ±5%, and the accuracy was higher than the traditional evaluation method. The stability of 2D resins during the storage of delayed-curing finishing was also analyzed through this method.

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Zauer, E. A., and A. B. Ershov. "Modern analyzers for the determination of nitrogen by the Kjeldahl method." Аналитика и контроль 23, no. 2 (2019): 168–92. http://dx.doi.org/10.15826/analitika.2019.23.2.002.

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Bowman, D. C., J. L. Paul, and R. M. Carlson. "A method to exclude nitrate from Kjeldahl digestion of plant tissues." Communications in Soil Science and Plant Analysis 19, no. 2 (February 1988): 205–13. http://dx.doi.org/10.1080/00103628809367932.

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Guebel, D. V., B. C. Nudel, and A. M. Giulietti. "A simple and rapid micro-Kjeldahl method for total nitrogen analysis." Biotechnology Techniques 5, no. 6 (1991): 427–30. http://dx.doi.org/10.1007/bf00155487.

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Demirata, Birsen, Resat Apak, Hüseyin Afsar, and Izzet Tor. "Spectrophotometric Determination of Organic Nitrogen by a Modified Lassaigne Method and Its Application to Meat Products and Baby Food." Journal of AOAC INTERNATIONAL 85, no. 4 (July 1, 2002): 971–77. http://dx.doi.org/10.1093/jaoac/85.4.971.

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Abstract A modified Lassaigne method was developed for N determination based on fusion of the organic substance with metallic Na, conversion of the cyanide in the aqueous leachate to thiocyanate by ammonium polysulfide treatment, and colorimetric measurement of the thiocyanate formed by the addition of excessive ferric ions in acidic medium. The mean molar absorptivity of the Fe(NCS)2+ complex at 480 nm is 2.96 × 103 L/mol·cm, enabling quantitation of 0.25–7.72 ppm N (linear range) in the final solution. The relative amounts of Na, (NH4)2S2, and Fe(III) with respect to nitrogen in the analyte were optimized. The developed method was successfully applied to the determination of N in various brands of baby food, and it was compared statistically with the conventional Kjeldahl and elemental analysis methods. Protein nitrogen in a number of meat products was also precisely determined by the developed method. Thus, the total digestion time of the conventional Kjeldahl method was reduced considerably (e.g., to approximately 15 min for a dried sample) with a relatively simple spectrophotometric method requiring no sophisticated instrumentation.

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Kartika Ningrum, Dian, Gervacia Jenny Ratnawati, and Indah Purwaningsih. "Pengaruh Suhu Penyeduhan terhadap Kadar Protein pada Susu Formula Menggunakan Metode KJELDAHL." Jurnal Laboratorium Khatulistiwa 2, no. 1 (July 7, 2019): 1. http://dx.doi.org/10.30602/jlk.v2i1.317.

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Abstract: Formula milk is a liquid or powder with a specifc formula given to infants and children. Serves as a substitute for breast milk. Formula milk has an important role in baby food because it often acts as the only source of nutrition for infants. Milk includes a high quality protein source. The purpose of this research is to determine the effect of temperature brewing on protein content in formula milk using the KJELDAHL method. This research was an experimental research using quasi-experiment. The samples in this research were 25 samples consisting of 5 treatments with repetition of each treatment 5 times. The examination method used in this research is a Kjeldahl method. From these results, the data obtained were analyzed statistically using a simple linear regression test. The results obtained in this study were the mean protein content of formula milk that was brewed at 40˚C, 50˚C, 60˚C, 70˚C and 80˚C respectively were 5,38%, 5,52%, 5.82%, 5.62% and 5.43%. Based on the results of statistical tests obtain p-value (0.139)> α (0,05) which means that Ha is rejected. Of the result it can be concluded that there is no effect of temperature brewing on protein content in formula milk using KJELDAHL method.Abstrak: Susu formula adalah cairan atau bubuk dengan formula tertentu yang diberikan pada bayi dan anak-anak. Berfungsi sebagai pengganti ASI. Susu formula memiliki peranan yang penting dalam makanan bayi karena seringkali bertindak sebagai satu-satunya sumber gizi bagi bayi. Susu termasuk sumber protein berkualitas tinggi. Tujuan dari penelitian ini yaitu untuk mengetahui pengaruh suhu penyeduhan terhadap kadar protein pada susu formula dengan menggunakan metode kjeldahl. Penelitian ini merupakan penelitian eksperimental menggunakan quasi experiment. Sampel pada penelitian ini berjumlah 25 sampel yang terdiri dari 5 perlakuan dengan pengulangan setiap perlakuan sebanyak 5 kali. Metode pemeriksaan yang digunakan dalam penelitian ini yaitu metode KJELDAHL. Dari hasil tersebut, data yang diperoleh dianalisis secara statistik menggunakan uji regresi linear sederhana. Hasil yang diperoleh pada penelitian ini yaitu rata-rata kadar protein pada susu formula yang diseduh pada suhu 40˚C, 50˚C, 60˚C, 70˚C dan 0˚C berturut-turut adalah 5,38%, 5,52%, 5,82%, 5,62% dan 5,43%. Berdasarkan hasil uji statistik diperoleh nilai p (0,798) > α (0,05) yang berarti bahwa Ha ditolak. Dari hasil tersebut disimpulkan bahwa tidak ada pengaruh suhu penyeduhan terhadap kadar protein pada susu formula menggunakan metode KJELDAHL.

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Lynch, Joanna M., David M. Barbano, Patrick A. Healy, and J. Richard Fleming. "Performance Evaluation of Direct Forced-Air Total Solids and Kjeldahl Total Nitrogen Methods: 1990 through 1995." Journal of AOAC INTERNATIONAL 80, no. 5 (September 1, 1997): 1038–43. http://dx.doi.org/10.1093/jaoac/80.5.1038.

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Abstract Results from collaborative studies of the performance of the direct forced-air oven-drying method for determination of milk total solids content (AOAC Method 990.20) and the Kjeldahl total nitrogen method for determination of milk total nitrogen content (AOAC Method 991.20) were published in 1989 and 1990, respectively. Method performance was characterized by using the harmonized ISC7IUPAC/ AOAC guidelines for method validation, and the methods now have final action status. During1990 through 1995, the split sample collaborative study format was used to monitor the performance of these methods as part of a multilaboratory quality assurance program. Seven blind duplicate milk materials were sent from a central laboratory onceevery 2 months to participating laboratories. Data were analyzed with the same statistical procedures used in the original collaborative studies. Compared with the original collaborative study, the repeatability and reproducibility of the oven-drying method improved over time. For the Kjeldahl total nitrogen method, within-laboratory repeatability improved slightly, whereas between-laboratory reproducibility was similar to but not always as good as in the original study. The results demonstrate that the statistical protocol for collaborative studies can be used effectively as the basis for a multilaboratory quality assurance program and that the method performance achieved in a collaborative study can be maintained and even improved with time.

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Meliashchenia, A., and K. Shehidzevich. "RESEARCH ALGORITHM OF THE PROTEIN COMPOSITION OF RAW MILK BY THE KYELDAL METHOD." Topical issues of processing of meat and milk raw materials, no. 14 (December 14, 2020): 77–85. http://dx.doi.org/10.47612/2220-8755-2019-14-77-85.

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The details of determining the protein composition of raw milk in accordance with the regulatory documents of the EAEU member-countries were studied. Based on the researches has been developed an algorithm for the dairy industry that establishes the sequence for determining the criteria characterizing the protein composition of raw milk using the Kjeldahl method.

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36

Anderson, Kim A., and Gregory Möller. "Alternative Catalyst to Mercury for Kjeldahl Determination of Nitrogen in Water and Wastewater Samples." Journal of AOAC INTERNATIONAL 78, no. 6 (November 1, 1995): 1516–18. http://dx.doi.org/10.1093/jaoac/78.6.1516.

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Abstract A non-polluting alternative catalyst was used in a U.S. Environmental Protection Agency (EPA) Kjeldahl digestion procedure for water and wastewater samples. The colorimetric semiautomated block digestion method (EPA Method 351.2) was essentially unchanged except that 1 mL of a saturated solution of titanium dioxide was added to the digestant mixture, instead of 2 g mercuric oxide. Titanium dioxide is a nontoxic compound, which makes an excellent replacement in total Kjeldahl nitrogen (TKN) determination. Samples were digested and then placed on a flow injection autoanalyzer for ammonia determination. All other digestion and analysis procedures were the same as in the original method. Detection limit for TKN was 0.1 mg/L. Recovery of glutamic acid averaged 96.2%. Recoveries of standard reference water samples over a 9 month period averaged >95%.

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37

Choi, Chul-Ho, and Chang-Sub Song. "Improvement of the Postmortem Tissue Plankton Detection Method by Using Kjeldahl Flask." Joural of the Korea Entertainment Industry Association 9, no. 2 (June 30, 2015): 323. http://dx.doi.org/10.21184/jkeia.2015.06.9.2.323.

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38

Khanizadeh, Shahrokh, Deborah Buszard, and Constantinos G. Zarkadas. "Misuse of the Kjeldahl Method for Estimating Protein Content in Plant Tissue." HortScience 30, no. 7 (December 1995): 1341–42. http://dx.doi.org/10.21273/hortsci.30.7.1341.

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39

Alvarado, José, Manuel Márquez, and Luis E. León. "Determination of Organic Nitrogen by the Kjeldahl Method Using Microwave Acid Digestion." Analytical Letters 21, no. 3 (March 1988): 357–65. http://dx.doi.org/10.1080/00032718808066330.

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40

Willis, Raymond B., Michael E. Montgomery, and Philip R. Allen. "Improved Method for Manual, Colorimetric Determination of Total Kjeldahl Nitrogen Using Salicylate." Journal of Agricultural and Food Chemistry 44, no. 7 (January 1996): 1804–7. http://dx.doi.org/10.1021/jf950522b.

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41

Barbano, David M., Jenny L. Clark, Chapman E. Dunham, and Richard J. Flemin. "Kjeldahl Method for Determination of Total Nitrogen Content of Milk: Collaborative Study." Journal of AOAC INTERNATIONAL 73, no. 6 (November 1, 1990): 849–59. http://dx.doi.org/10.1093/jaoac/73.6.849.

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Abstract A macro-KJeldahl procedure using a copper catalyst for determination of milk total nitrogen was developed for both traditional and block dlgestor/steam distiller equipment, and the performance was evaluated by collaborative study. In the first trial of the collaborative study, 9 pairs of blind duplicate milk samples were analyzed for total nitrogen and total nitrogen was converted to "protein" by using a factor of 6.38. Protein content of milk samples ranged from 3.086 to 3.610%. In the first trial, sR and R values for the block dlgestors were influenced significantly by protein concentration; 8R and R values were not Influenced by protein concentration for traditional equipment. It was hypothesized that total digestion time for some block dlgestors In the first trial was not sufficient for high protein milk samples. Thus, a second trial was undertaken with boiling time after clearing Increased by 0.5 h. In the second trial, none of the parameters for reproducibility with either type of equipment were Influenced by protein concentration. It was concluded that laboratory-to-laboratory differences In line voltage may require different total digestion times in different laboratories, particularly those using block dlgestors. The Kjeldahl method using a copper catalyst and either traditional or block digestor equipment for determination of milk total nitrogen has been adopted official first action by AOAC to replace method 920.105.

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42

Edwards, A. H. "The semi-micro Kjeldahl method for the determination of nitrogen in coal." Journal of Applied Chemistry 4, no. 6 (May 4, 2007): 330–40. http://dx.doi.org/10.1002/jctb.5010040610.

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43

Špirić, Zdravko, Trajče Stafilov, Ivana Vučković, and Marin Glad. "Study of nitrogen pollution in Croatia by moss biomonitoring and Kjeldahl method." Journal of Environmental Science and Health, Part A 49, no. 12 (July 29, 2014): 1402–8. http://dx.doi.org/10.1080/10934529.2014.928532.

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44

Abrams, Dean, David Metcalf, and Michael Hojjatie. "Determination of Kjeldahl Nitrogen in Fertilizers by AOAC Official MethodSM 978.02: Effect of Copper Sulfate as a Catalyst." Journal of AOAC INTERNATIONAL 97, no. 3 (May 1, 2014): 764–67. http://dx.doi.org/10.5740/jaoacint.13-299.

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Abstract In AOAC Official MethodSM 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 MethodSM 970.02, Nitrogen (Total) in Fertilizers is a comprehensive total nitrogen (including nitrate nitrogen) method adding chromium metal. AOAC Official MethodSM 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 MethodSM 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 MethodSM 978.02. The second part of the study was to exclude the addition of copper sulfate from AOAC Official MethodSM 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.

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Sittampalam, G. Sitta, Robert M. Ellis, David J. Miner, Eugene C. Rickard, and Dean K. Clodfelter. "Evaluation of Amino Acid Analysis as Reference Method to Quantitate Highly Purified Proteins." Journal of AOAC INTERNATIONAL 71, no. 4 (July 1, 1988): 833–38. http://dx.doi.org/10.1093/jaoac/71.4.833.

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Abstract The applicability of amino acid analysis for accurate quantitation of reference standard preparations of proteins has been evaluated. This approach is very useful since, in addition to absolute quantitative information, it also provides a measure of composition, partial identity, and purity in a single experiment. Comparisons with Kjeldahl nitrogen assay and/or UV measurements shows that amino acid analysis is reliable for the quantitation of small-to-medium size proteins in the molecular weight range of 6-22 kDa. For larger proteins such as immunoglobulins (150 kDa), amino acid analysis may "underestimate" the total protein concentration. These results also show the effect of recovery of individual residues on protein quantitation. As expected, the recovery of more than one stable residue could be used to calculate total protein content of samples, which is in good agreement with the results obtained by Kjeldahl nitrogen assay. However, the protein concentrations calculated from the total mass of the recovered residues appear to give relatively low estimates in almost all cases. Thus, it is concluded that amino acid analysis is an appropriate reference method only when stable residues are employed for quantitation, particularly for highly purified proteins of rDNA origin

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Botaro, Bruno Garcia, Cristina Simões Cortinhas, Lucinéia Mestieri, Paulo Fernando Machado, and Marcos Veiga dos Santos. "Prediction of bovine milk true protein content by mid-infrared spectroscopy." Ciência Rural 41, no. 8 (August 2011): 1472–74. http://dx.doi.org/10.1590/s0103-84782011000800028.

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The aim of this study was to estimate the concentration of milk true protein (TP) by mid-infrared absorbance method (MIR) in samples from bulk tank of dairy herds, and to determine the correlation between the results of TP of milk determined by Kjeldahl and MIR. Forty nine dairy herds were selected (17 Holstein, 6 Jersey and 26 Girolando) for monthly collections of samples from bulk tanks during the period of one year (284 samples). Fat, lactose, crude protein and total solids were firstly determined by MIR, and then analyzed for total and true protein by Kjeldahl method. The regression equation to estimate TP contents based on MIR crude protein determination was as follows: TP=0.0021+(1.0104xCP), where: TP is the content of true protein, CP is the crude protein content determined by the MIR method, and 0.0155 is the model error term.

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Marcó, A. "Comparison of the Kjeldahl method and a combustion method for total nitrogen determination in animal feed." Talanta 57, no. 5 (July 3, 2002): 1019–26. http://dx.doi.org/10.1016/s0039-9140(02)00136-4.

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48

NOZAWA, Shintaro, Akiko HAKODA, Kenichi SAKAIDA, Tadanao SUZUKI, and Akemi YASUI. "Method Performance Study of the Determination of Total Nitrogen in Soy Sauce by the Kjeldahl Method." Analytical Sciences 21, no. 9 (2005): 1129–32. http://dx.doi.org/10.2116/analsci.21.1129.

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Schaalje, G. B., and H. H. Mündel. "Use of residual maximum likelihood to evaluate accuracy of two NIRS calibration procedures, relative to Kjeldahl, for determining nitrogen concentration of soybeans." Canadian Journal of Plant Science 71, no. 2 (April 1, 1991): 385–92. http://dx.doi.org/10.4141/cjps91-053.

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The accuracy of estimates of plant properties based on near-infrared reflectance spectroscopy (NIRS) varies with many factors including the biological material in question and the method used to calibrate the NIRS instrument. This study investigated the accuracy, relative to Kjeldahl analysis, of NIRS analysis based on two calibration methods in estimating nitrogen concentration of four stages and/or parts of soybean (Glycine max (L.) Merr.) plants. Samples of whole top growth at anthesis, whole top growth at maturity, whole top growth at maturity excluding seeds, and seeds were obtained from two field trials and one phytotron experiment. Two Kjeldahl determinations of nitrogen concentration were obtained for each sample, as well as reflectance values at each of 19 infrared wavelengths, using a Technicon InfraAlyser 400R. Different subsets of the sample data were used for calibration and assessment of accuracy. The instrument was calibrated using stepwise multiple linear regression (SMLR) and principal component regression (PCR). The residual maximum likelihood procedure was useful in showing that NIRS estimates based on either SMLR or PCR were at least as accurate as Kjeldahl estimates for all stages and/or parts except whole top growth at maturity excluding seeds. Key words: Calibration, principal component regression, stepwise regression

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Praveen-Kumar and R. K. Aggarwal. "Substitution of reduced iron by zinc in total soil nitrogen estimation by modified Olsen's method." Journal of Agricultural Science 108, no. 3 (June 1987): 681–82. http://dx.doi.org/10.1017/s0021859600080138.

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The conventional Kjeldahl method which is usually employed for determination of total N in soil does not effect quantitative recovery of NO2- or NO3- (Bremner, 1965). Therefore, various modifications have been suggested (Cope, 1916; Davisson & Parson, 1919). Bremner (1965) observed that the quantitative recovery of NO2- and NO3- by any method, other than the modified Olsen's method (Bremner & Shaw, 1958), is not certain.

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Journal articles on the topic 'Kjeldahl method'

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