Abstract: The research established a method for determining trace zinc in table salt by adding the same content of NaCI matrix to the standard solution and using flame atomic absorption spectrometry. The method is simple, the measurement range is 0.02-0. 8mg / L, the precision and accuracy are good, and the relative deviation of the measurement is less than 3%.
Keywords: atomic absorption spectrophotometry; zinc; table salt
Zinc is a trace element necessary for the human body. The lack of zinc in the human body will affect various systems of the body, such as causing decreased taste, anorexia, loss of appetite and anorexia. In addition, it will cause obvious slow growth and low immune function. In addition to the general iodized salt in the current salt market. One after another appeared health salt added with various trace elements, such as zinc salt. Add iron salt, add magnesium salt, and compound salt with a variety of trace elements. There have been reports on the determination of trace elements in table salt. The determination of the atomic absorption of zinc usually involves extraction. To rule out the effects of coexisting salt. This method eliminates the interference of coexisting salts on the determination of zinc by adding the same salt matrix to the standard solution. The results show that this method has high precision and accuracy. Wide linear range and easy operation.
Materials and Methods
1 Instruments and main reagents WFX-120 atomic absorption spectrophotometer (Beijing Ruili Analytical Instrument Company); AB204-N electronic balance (Mettler-Toledo Instruments (Shanghai) Co., Ltd.). Zinc standard solution: Dissolve 1.000 g of metallic zinc with 1: 1 HC1, and then dilute it with 2% HC1 to 1 L. This is the stock solution. The concentration is 1 mg / ml. Before use, dilute the application solution with 2% HC1 to 10 mg / L. NaCI (Analytical Pure) (Xilong Chemical Plant, Shantou City, Guangdong). The reagents used are all above analytically pure; water is ultrapure water; all reagents are stored in PVC bottles.
2 Analysis steps
2.1 Instrument operating conditions Wavelength 213.9 nm. The slit is 0.4 nm. HCL current 2.0mA, D2 lamp background correction. D2 lamp current is 99.5 mA, and acetylene flow is 3.0 ml / min. The air flow rate is 10.ml/min, and the measurement method is time average (reading time is 3.0 s).
2.2 Preparation of working curve Pipette 0, 0.05, 0.10, 0.25, 0.50, 1.00, and 2.00ml of zinc application solution into 25ml volumetric flask, add 10.00ml each 6 g / L NaC1 solution, dilute to the mark with 2% HC1. The flame atomic absorption method was used to determine the absorbance value, the working curve was plotted against the concentration, and the regression equation was calculated.
2.3 Determination of precision In the linear range, three concentrations of the above zinc solution (high (0.4 mg / L), medium (0.2 mg / L), low (0.04 mg / L), each 9 parts of the solution, the absorbance was measured under operating conditions. Calculate the coefficient of variation separately.
2.4 Determination of accuracy Accurately weigh 0.6g of table salt in a 100ml volumetric flask and dilute to the mark with 2% HC1. Accurately draw 10.00 ml of this sample solution into four 25ml volumetric flasks. 4 bottles of zinc standard application solution 0, 0.10, 0.40. 1. 00ml, and then diluted with 2% HC1 to the mark. Measure the absorbance under the operating conditions, and calculate the recovery rate according to the following formula.
Results and references
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