The sample was decomposed by HCl and HNO3, and the absorbance of Ag was determined by air-acetylene flame AAS method in aqua regia (1+4) medium. Multiple coexisting elements do not interfere with the assay. When the Ag content is low and the sampling amount is large, there is background interference. This method is applicable to the determination of w(Ag)/10-6=1-500 (the instrument has a background correction device) and w(Ag)/10-6=5-500 (the instrument has no background correction device) in rocks and minerals.
Second, reagent preparation
Silver standard storage solution: A standard storage solution of 1000 μg/mnL Ag was prepared by the method of determining silver by a thiourea medium flame method.
Silver standard solution: Pipette 50.0mL silver standard storage solution in a 500mL volumetric flask, dilute to the mark with HNO3 (1+99), and mix. This solution contained 100 μg/mL Ag.
Third, the instrument and working conditions
WFX-1E atomic absorption spectrometer. Silver hollow cathode lamp; lamp core 4 mA; wavelength 328.1 nm; spectral passband 0.2 nm; burner height 13 mm; air flow rate 7 L/min; acetylene flow rate 1.2 L/min.
Fourth, the analysis steps
Weigh 0.2-1.0g (accurate to 0.0001g) sample in a beaker, wet with a small amount of water, add 15-20mL HCl, heat at low temperature for about 10min, add 5mL HNO3, continue heating until decomposition and steam to near dry, remove Slightly cold, add 8 mL HCl, 2 mL HNO3 and a small amount of water, and heat to dissolve the salts. After the test solution is cooled, transfer it to a 50 mL volumetric flask, dilute to the mark with water, and mix. Stand still and clarify. Adjust the AAS instrument to the proposed working conditions, and take the test solution into the air-acetylene flame to determine the absorbance of Ag. The same batch is accompanied by a blank test.
Drawing of the working curve: separately transfer the calculated amount of silver standard solution into two groups of 100 mL volumetric flasks, add 16 mL of HCl, 4 mL of HNO3, dilute to the mark with water, and mix. In the standard series, the mass concentrations of Ag were 0, 0.20, 0.40, 0.60, 0.80, 1.00 μg/mL, and 0, 1.0, 2.0, 3.0, 4.0, and 5.0 μg/mL, respectively. The sample solution was measured in the same batch, and the mass concentration of Ag was taken as the abscissa, and the corresponding absorbance was the ordinate, and the working curve was drawn.
V. Calculation of analysis results
General rule
(ÏB2-ÏB1)×Vs
wB/10-6=------------------
Ms Calculate the amount of Ag in the sample.
Six, matters needing attention
The same method as for the determination of silver by the hydrochloric acid medium flame method.
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