Tin is one of the 14 essential trace elements in the human body, but its role in organisms is not yet clear. The method of determining tin in water has not been reported. At present, there is no standard test method for the determination of tin in water. Today, hydrochloric acid is used to digest the sample, and the deuterium lamp background correction technology eliminates the non-characteristic absorption and light scattering effects. Flame atomic absorption spectrometry is used to determine high concentration of tin in electroplating wastewater. Claim.
1. Test
1.1 Main instruments and reagents
TAS-986 Flame Atomic Absorption Spectrometer, Beijing General Analysis General Corporation; Tin Hollow Cathode Lamp, Shanghai Electro-Optical Devices Co., Ltd. 1000μg / mL tin standard stock solution: accurately weigh 1.000g metal tin (99.99%), dissolve in 100mL warm concentrated HCl, dilute to 1L with water after cooling, the concentration of Sn in this solution is 1000μg / mL, avoid light Stored in polyethylene bottles; hydrochloric acid, excellent grade pure.
1.2 Working conditions of the instrument
The working conditions of flame atomic absorption spectrometer are shown in Table 1.
1.3 Sample preparation
Take 100ml of uniformly mixed wastewater sample in a beaker, heat to near dryness, remove and let cool, then add 10ml of hydrochloric acid, cover and heat at 95 ° C under reflux, continue to add hydrochloric acid if necessary, until the digestion is complete, continue heating to near dryness, use heat 10 Wash the watch glass and beaker with% hydrochloric acid solution, dissolve the precipitate and residue, move to a 100kl brown volumetric flask, and make up to volume with 10% hydrochloric acid solution.
2. Results and discussion
2.1 Interference and elimination
The air-acetylene rich flame is more sensitive, so it is better to choose the 286.3nm wavelength at this time, with less interference. In the actual analysis, the acetylene flow rate should be carefully adjusted to obtain the maximum sensitivity. In the measurement, it should be a very flaming flame, but at the same time, the chemical interference of the coexisting elements is greatly affected by the flame state, such as PO43- and SO2-4. Therefore, ammonium chloride was added to the experiment to eliminate it. At the same time, ammonium chloride has a sensitizing effect on the determination of many elements and suppresses the interference of multiple coexisting elements. Non-characteristic absorption and light scattering are eliminated with deuterium lamp background correction technology.
2.2 Calibration curve
Pipette the standard solution of Sn accurately, its concentration is 0, 25, 50, 60, 80mg / L, put into 5 100ml dissolving flasks, add 2ml of the mass fraction 20% ammonium chloride solution, and use the mass fraction 10 % HCL is diluted and dissolved. Under the above working conditions, with 10% HCL solution as a reference, the absorbance was measured.
2.3 Precision and accuracy
In order to verify the precision and accuracy of the method, the 50 mg / L standard solution was tested.
3. Conclusion
The experimental results show that using hydrochloric acid digestion and flame atomic absorption spectrometry to determine the mass concentration of tin in wastewater has simple operation and less interference. The precision and preparation of this method can meet the technical requirements of wastewater monitoring.
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