Protein Nitrogen Determination by Kjeldahl Digestion and Ion Chromatography. 2016

Hsiaoling Wang, and Nagarani Pampati, and William M McCormick, and Lokesh Bhattacharyya
Division of Biological Standard and Quality Control, Office of Compliance and Biologics Quality, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland 20993.

We report development and validation of a simple, rapid, and accurate method for the quantitation of protein nitrogen, which combines Kjeldahl digestion and ion chromatography with suppressed conductivity detection and requires nanomolar amount of nitrogen in samples (≥10 μg protein). The mechanism of suppressed conductivity detection does not permit analysis of samples containing copper (present in Kjeldahl digestion solution) and aluminum (present in many vaccines as adjuvants) due to precipitation of their hydroxides within the suppressor. We overcame this problem by including 10 μM oxalic acid in Kjeldahl digests and in the eluent (30 mM methanesulfonic acid). The chromatography is performed using an IonPac CS-16 cation exchange column by isocratic elution. The method reduces the digestion time to less than 1 h and eliminates the distillation and titration steps of the Kjeldahl method, thereby reducing the analysis time significantly and improving precision and accuracy. To determine protein nitrogen in samples containing non-protein nitrogen, proteins are precipitated by a mixture of deoxycholate and trichloroacetic acid and the precipitates are analyzed after dissolving in KOH. The method is particularly useful for biological samples that are limited and can also be applied to food, environmental, and other materials.

UI MeSH Term Description Entries
D009584 Nitrogen An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.
D010047 Ovalbumin An albumin obtained from the white of eggs. It is a member of the serpin superfamily. Serpin B14
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D002623 Chemistry Techniques, Analytical Methodologies used for the isolation, identification, detection, and quantitation of chemical substances. Analytical Chemistry Techniques,Analytical Chemistry Methods,Analytical Chemistry Method,Analytical Chemistry Technique,Chemistry Method, Analytical,Chemistry Methods, Analytical,Chemistry Technique, Analytical,Method, Analytical Chemistry,Methods, Analytical Chemistry,Technique, Analytical Chemistry,Techniques, Analytical Chemistry
D002852 Chromatography, Ion Exchange Separation technique in which the stationary phase consists of ion exchange resins. The resins contain loosely held small ions that easily exchange places with other small ions of like charge present in solutions washed over the resins. Chromatography, Ion-Exchange,Ion-Exchange Chromatography,Chromatographies, Ion Exchange,Chromatographies, Ion-Exchange,Ion Exchange Chromatographies,Ion Exchange Chromatography,Ion-Exchange Chromatographies
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000075462 Serum Albumin, Human Serum albumin from humans. It is an essential carrier of both endogenous substances, such as fatty acids and BILIRUBIN, and of XENOBITOICS in the blood. Albumin Human,Human Albumin,Human Serum Albumin,Albumin, Human,Albumin, Human Serum,Human, Albumin
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012710 Serum Albumin, Bovine Serum albumin from cows, commonly used in in vitro biological studies. (From Stedman, 25th ed) Fetal Bovine Serum,Fetal Calf Serum,Albumin Bovine,Bovine Albumin,Bovine Serum Albumin,Albumin, Bovine,Albumin, Bovine Serum,Bovine Serum, Fetal,Bovine, Albumin,Calf Serum, Fetal,Serum, Fetal Bovine,Serum, Fetal Calf
D022122 Anthrax Vaccines Vaccines or candidate vaccines used to prevent ANTHRAX. Anthrax Vaccine,Vaccines, Anthrax,Vaccine, Anthrax

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