The Kjeldahl method is a commonly used method for determining the total nitrogen content in compounds or mixtures. Due to its accurate detection results, it is still regarded as a standard testing method. The Kjeldahl nitrogen analyzers that are currently popular and widely promoted in the market are highly respected. However, due to various issues during the experimental process, a series of detection anomalies are inevitable. Therefore, when using the Kjeldahl method to measure protein, the blank test results tend to be on the high side. What are the specific reasons for this?

Firstly, the purity of all reagents used should be checked. Generally, this includes whether the distilled water, boric acid, and sodium hydroxide used are of analytical grade. These are the most basic testing conditions that must be ensured to be correct. If any reagent issues are detected, the reagent should be replaced in time, and then the test can be conducted again.

Secondly, the blank experiment introduces nitrogen-containing impurities. This requires us to be meticulous in our experiments, ensuring that the containers used are clean and dry, and that the reagents used do not contaminate each other.

Furthermore, the relevant containers may be contaminated and not cleaned thoroughly. For example, the splash guard assembly on the digestion tube will inevitably accumulate some dirt due to prolonged distillation, requiring us to clean it. The most commonly used cleaning method is to pour half of boric acid into the digestion tube, heat the water to melt it, and directly attach it to the instrument for distillation for about 10 minutes. Then, steam it several times with distilled water.

The above is our basic analysis of the high detection values of blank paper by the nitrogen analyzer. Of course, if problems arise during the experiment, we need to identify the causes step by step. In summary, the requirements for the experiment are reliable conditions and careful steps, which generally lead to satisfactory results.