How do you measure total protein?

Total protein is commonly measured using nitrogen analysis. Here's a breakdown of the process, based on the provided reference:

Nitrogen Analysis for Total Protein Measurement

The determination of total protein hinges on accurately quantifying the nitrogen content within a sample. This method relies on the fact that proteins contain a relatively constant percentage of nitrogen.

Steps involved in Nitrogen Analysis

1. Combustion: The sample undergoes combustion with oxygen. This process breaks down the protein molecules and converts the nitrogen present into nitrogen oxides (NOx).
2. Gas Collection: The resulting gases, which include the nitrogen oxides, are collected in a ballast tank. This tank serves to contain the gases until a specific pressure is reached, ensuring accurate measurement.
3. Carrier Gas: Helium is used as a carrier gas during the combustion and collection processes. Helium is inert and helps to efficiently transport the gases through the system.
4. Reduction: An aliquot (a small, representative portion) of the combustion gas, now containing the nitrogen oxides, is taken. This aliquot is then subjected to a reduction process, which converts the nitrogen oxides back into elemental nitrogen (N2).
5. Quantification: The amount of elemental nitrogen is then measured. This measurement is directly proportional to the amount of nitrogen originally present in the sample.
6. Calculation: Finally, the total protein content is estimated by multiplying the measured nitrogen content by a conversion factor. This factor is based on the average nitrogen content of proteins (approximately 16%).

Summary in a Table

Step	Description	Purpose
Combustion	Sample is burned with oxygen.	Converts nitrogen in the protein to nitrogen oxides.
Gas Collection	Gases, including nitrogen oxides, are collected in a ballast tank.	To contain the gases until a specific pressure is reached for accurate measurement.
Carrier Gas	Helium is used.	To efficiently transport the gases through the system.
Reduction	Nitrogen oxides are reduced to elemental nitrogen.	To prepare the nitrogen for quantification.
Quantification	The amount of elemental nitrogen is measured.	To determine the nitrogen content in the sample.
Calculation	Total protein is estimated by multiplying the measured nitrogen content by a conversion factor (around 6.25).	To estimate the total protein content of the original sample, based on the known nitrogen content of most proteins.