graphite furnace atomic absorption spectrometry

Introduction

1. Principle of the method
Graphite furnace atomic absorption spectrometry is a method of quantitative analysis based on the absorption degree of the ground state atoms of the element to be measured to its characteristic spectral line. When determining lead in high-salt foods, the sample is digested and the lead element is converted into an ionic state that can be measured. Then, through the heating program of the graphite furnace, the lead is atomized to absorb light of a specific wavelength. By measuring the intensity of the absorbed light, the lead content in the sample can be calculated.

2. Advantage analysis
High sensitivity: Graphite furnace atomic absorption spectrometry can detect extremely low concentrations of lead, which has great advantages for the determination of trace lead in high-salt foods. The method of graphite furnace atomic absorption spectrometry established in the experiment to determine trace lead in high-salt food has a detection limit of 0.005mg/kg, which can meet the detection requirements of trace lead in high-salt food.

Good selectivity: This method can effectively eliminate the interference of other elements and improve the accuracy of determination by selecting appropriate wavelengths and spectral bandwidths.

Wide range of applications: It can be used not only for the determination of lead in high-salt foods, but also for the determination of lead in other types of foods and environmental samples.

3. Experimental steps
Sample digestion: High-salt food samples usually need to be digested to release lead from the sample. Commonly used digestion methods include nitric acid digestion. In the experiment, the sample was digested with nitric acid, heated at a constant temperature to drive out the acid, and then eluted and desalted with an Ag ion column.

Matrix improvement: Due to the complex matrix of high-salt food, it may interfere with the determination of lead.

Therefore, a matrix modifier is needed to improve the accuracy of the determination. For example, potassium chloride-ammonium dihydrogen phosphate is used as a matrix modifier to increase the ashing temperature in the experiment, and the standard addition method is used to remove matrix interference in high-salt foods.

Instrumental determination: The treated sample is placed in a graphite furnace atomic absorption spectrometer for determination. Set appropriate instrument parameters, such as drying temperature, ashing temperature, atomization temperature, etc. The graphite furnace heating program in the experiment is: drying 150℃ for 30s; drying 2140℃ for 20s; ashing 550℃ for 20s; atomization temperature is 2000℃ for 4s. The photomultiplier tube voltage is 506V, the lamp current is 6mA, the wavelength is 283.3nm, the slit width is 0.4nm, the time constant is 0.1s, and the Zeeman effect background correction is used.

4. Reliability verification of the method
Linear range: Graphite furnace atomic absorption spectrometry has a good linear relationship within a certain concentration range. The mass concentration of lead in the experiment showed a good linear relationship with the absorbance in the range of 0 - 30ng/mL, and the linear correlation coefficient was 0.9998.

Precision: The precision of the method was verified by repeatedly measuring the same sample and calculating the relative standard deviation (RSD). The CV% (relative standard deviation) of the determination method in the experiment was 3.7 in one day and 4.5 for six consecutive days. The relative standard deviation of the determination results in the experiment was 1.58% - 2.16% (n = 7).

Accuracy: The accuracy of the method can be verified by a spike recovery experiment. The sample spike recovery rate in the experiment was 82.40% - 107.89%. The average spike recovery rates of the three lead concentrations of low, medium and high in the experiment were 82.6% - 117.0%, 92.3% - 95.7%, and 93.6% - 103.0%, respectively, with a relative standard deviation of 1.2% - 7.5%.

5. Application Cases
Analyze the effect of graphite furnace atomic absorption spectrometry on the detection of lead in high-salt foods.

By using potassium chloride-ammonium dihydrogen phosphate as a matrix modifier and the standard addition method to remove matrix interference, this method can effectively remove the matrix interference formed by sodium chloride content >5% in the sample, and the detection limit is 0.025mg/kg. The precision of the standard material is 5.1% and 6.0%. At the same time, the results are within the quality control range compared with the certificate values.

Establish a graphite furnace atomic absorption spectrometry method to determine the content of trace lead in high-salt foods. This method has high sensitivity, accurate and reliable results, and is suitable for the detection of trace lead in high-salt foods. The salt content of food within 20% has no significant effect on the determination of lead.

Establish a method for the determination of lead in high-salt foods by solid phase extraction-graphite furnace atomic absorption spectrometry. The solid phase extraction column can effectively separate lead from sodium salt in high-salt foods, eliminating the matrix interference when determining lead in high-salt foods by graphite furnace atomic absorption spectrometry. The method is accurate, highly sensitive, and reproducible, and is suitable for the determination of lead content in high-salt samples.

Summarize
In summary, graphite furnace atomic absorption spectrometry is feasible and widely used in the determination of lead in high-salt foods. This method has the advantages of high sensitivity, good selectivity, and a wide range of applications. Through reasonable experimental steps and reliability verification of the method, the lead content in high-salt foods can be accurately determined.