The methods for determining the content of ferric pyrophosphate in foods mainly include chemical analysis methods and instrumental analysis methods. The specific introductions are as follows:
I. Chemical Analysis Method
Principle: Usually, ferric pyrophosphate is made to undergo a chemical reaction with specific reagents, and the content of ferric pyrophosphate is indirectly determined by measuring the amount of reaction products or the amount of consumed reagents. For example, the iron ions in it can be released first, and then the complexometric titration method is used. With disodium ethylenediaminetetraacetate (EDTA) as the titrant, under a certain pH condition, EDTA forms a stable complex with iron ions. The content of iron ions is calculated by the amount of consumed EDTA, and then the content of ferric pyrophosphate is deduced.
Operation Steps: First, pre-treat the food sample, such as ashing or acid digestion, to break down the organic substances in the food and release the iron ions in ferric pyrophosphate. Then, adjust the treated sample solution to an appropriate pH value, add an indicator, and titrate it with a known concentration of EDTA standard solution until the end point is reached. Calculate the content of iron ions according to the consumption of this standard solution.
Advantages and Disadvantages: The advantage is that the operation is relatively simple and the cost is low, making it suitable for some occasions where the precision requirement is not particularly high. The disadvantages are that the sensitivity is low, there are many interfering factors. For food samples with complex matrices, multiple separation and purification operations may be required, and the analysis time is relatively long.
II. Instrumental Analysis Method
1. Atomic Absorption Spectrometry (AAS)
Principle: Utilize the characteristic that iron atoms have selective absorption of light at a specific wavelength. After atomizing the sample solution, it is introduced into the atomizer to convert iron ions into ground-state atoms. When the characteristic light emitted by the hollow cathode lamp passes through the atomizer, the ground-state iron atoms will absorb the light at a specific wavelength. According to the linear relationship between the absorbance and the concentration of iron ions, determine the iron content in the sample, and thus obtain the content of ferric pyrophosphate.
Operation Steps: First, digest the food sample to prepare a sample solution suitable for analysis. Then, introduce the sample solution into the atomic absorption spectrometer, select appropriate analysis wavelengths and instrument parameters, and carry out the determination. By comparing with the standard curve, obtain the concentration of iron ions in the sample, and then calculate the content of ferric pyrophosphate.
Advantages and Disadvantages: It has the advantages of high sensitivity, good selectivity, and high accuracy. It can quickly and accurately determine the trace iron elements in foods and is suitable for various types of food samples. The disadvantages are that the instrument is expensive, professional operators are required, and it can only determine the total amount of iron elements and cannot directly determine the form of ferric pyrophosphate.
2. Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Principle: After atomizing the sample solution, it is introduced into the inductively coupled plasma to ionize various elements in the sample, and then the ions are separated and detected by a mass spectrometer. According to the relationship between the intensity of ion peaks with different mass-to-charge ratios and the element concentration, determine the iron element content in the sample, and thus determine the content of ferric pyrophosphate.
Operation Steps: After the sample undergoes pretreatment such as digestion, inject the solution into the ICP-MS instrument. The instrument automatically performs the processes of ionization, separation, and detection. By comparing with the standard substances, obtain the content of each element in the sample, and then calculate the content of ferric pyrophosphate.
Advantages and Disadvantages: This method has extremely high sensitivity and accuracy, can simultaneously determine multiple elements, and can accurately analyze food samples with complex matrices. However, the instrument is expensive, the operation cost is high, and the requirements for the pretreatment of samples are strict.
