Food additives Ammonia water and liquid ammonia detection

The detection method of ammonia water and liquid ammonia in food additives is mainly determined based on their physical and chemical properties and uses. The following is a detailed description of the detection method of ammonia water and liquid ammonia:

1. Ammonia detection method
When ammonia water is used as a food additive, the main detection items include ammonia content, lead content, evaporation residue, and oxidizable substance test. The specific detection methods are as follows:

Ammonia content detection:
The concentration of ammonia water can be determined by the phenolphthalein indicator method, Nessler reagent method, pH meter method, or specific gravity method.
Among them, the phenolphthalein indicator method is to judge the concentration of ammonia water by mixing the sample with phenolphthalein indicator and observing the color change of the solution; the Nessler reagent method is to use the Nessler reagent to react with ammonia water to produce a brown precipitate to determine the concentration; the pH meter method is to measure the pH value of the solution, then add a standard ammonia solution for titration, and calculate the ammonia concentration; the specific gravity method is to determine the concentration by measuring the specific gravity of the sample and comparing it with an ammonia solution of known concentration.
Lead content detection:
Atomic absorption spectroscopy or inductively coupled plasma mass spectrometry (ICP-MS) are usually used to determine the lead content in ammonia water.
These methods are highly sensitive and accurate and can accurately determine trace lead elements in samples.
Evaporation residue detection:
Place a certain amount of ammonia sample in an electric constant temperature drying oven and dry it to constant weight, then weigh the mass of the residue, which is the amount of evaporation residue.
Oxidizable substance test:
By adding a certain amount of potassium permanganate solution to the sample and observing the change in the color of the solution, it is determined whether there is an oxidizable substance in the sample.
2. Liquid ammonia detection method
When liquid ammonia is used as a food additive or industrial raw material, its detection items mainly include ammonia content, moisture, oxygen content, nitrogen content, carbon monoxide content, and hydrocarbon content. The specific detection methods are as follows:

Ammonia content detection:
The ammonia content of liquid ammonia is usually determined by gas chromatography or chemical titration.
Gas chromatography separates and determines the content of each component by injecting liquid ammonia into the gas chromatograph after vaporization, and using the different retention times of different components on the chromatographic column; the chemical titration rule is to calculate the ammonia content by adding a standard acid solution to react with liquid ammonia and using an indicator to determine the titration endpoint.
Moisture detection:
The moisture content in liquid ammonia can be determined by Karl Fischer titration or dew point method.
Karl Fischer titration is to calculate the moisture content by adding Karl Fischer reagent to react with the moisture in the sample and using an indicator to determine the titration endpoint; the dew point rule is to infer the moisture content by measuring the dew point temperature of the sample under specific conditions.
Oxygen content, nitrogen content, carbon monoxide content, and hydrocarbon content detection:
The detection of these components usually adopts instrumental analysis methods such as gas chromatography or mass spectrometry.
The sample is vaporized and injected into the instrument, and the separation and detection characteristics of different components on the chromatographic column or mass spectrometer are used to determine the content of each component.
3. Testing precautions
When testing ammonia water and liquid ammonia, relevant safety operating procedures should be strictly followed to prevent dangerous accidents such as sample leakage or explosion.
Qualified testing equipment and reagents should be used during the test to ensure the accuracy and reliability of the test results.
The samples should be fully mixed and homogenized before testing to ensure the representativeness of the test results.
During the test, attention should be paid to observing the operating status of the instrument and the reading changes of the indicator, and abnormal situations should be discovered and handled in time.
In summary, there are many methods for testing ammonia water and liquid ammonia in food additives and appropriate methods should be selected for determination according to specific test requirements and sample characteristics. At the same time, relevant standards and specifications should be strictly followed during the test to ensure the accuracy and reliability of the test results.