Concentration prediction:
Before testing the water sample, first predict the zinc concentration value of the water sample, and select the operation steps corresponding to the range, e.g. predict the zinc concentration value is 0-3mg/L, you need to select the operation procedure of 0-3mg/L range; If the zinc concentration is predicted to be 3-15mg/L, the procedure of the 3-15mg/L range is selected.
Notes:
Cleaner water samples can be directly sampled for determination, and water samples with more total zinc and suspended solids and organic matter need to be treated as follows: 50ml of water samples should be pipettedIn a 150ml beaker, add 5ml of concentrated nitric acid, heat and evaporate to about 10ml, and then add 5ml of concentrated nitric acid and 1ml of perchloric acid when it is slightly cold, and continue to heat and evaporate to nearDry, add 40ml of water, heat and boil for 3min, cool, adjust the pH of the test solution to neutral with (1+1) ammonia, transfer to a 50ml volumetric flask and dilute it with water to the standardLine.
1 1. When the predicted value is in the range of 0-3mg/L
If zinc is present, the water sample will show a dark orange-red color, and the darker the color, the higher the concentration value of the water sample. Analytical procedure: Zinc L; Watch out for overrange tips!
2. When the predicted value is in the range of 3-15mg/L
If zinc is present, the water sample will show a dark orange-red color, and the darker the color, the higher the concentration value of the water sample. Analytical procedure: Zinc H; Watch out for overrange tips!
3. When the predicted value exceeds 15 mg /L
The water sample needs to be diluted to the corresponding concentration value in sections 1-2 above, and then operated according to the corresponding range, and the determination result is multiplied by the dilution factor.
4. Test steps on the computer
5. Precautions
◆ If there is zinc, the water sample shows a dark orange-red color, and the darker the color, the higher the concentration value of the water sample.
◆ Pay attention to cross-contamination, use different measuring utensils for different liquids (pay attention to changing the tip when using a pipette).
◆ Use appropriate pipetting tools to take liquids, and large range measuring tools cannot measure small volumes of water samples, such as: 5mL pipettes cannot be used to remove 2mL and below liquidsFor liquids less than or equal to 2mL, it is recommended to pipette twice with a 1mL pipette.
◆ When using a pipette, it is necessary to calibrate the pipette frequently (it is recommended to do so once a week), and pay attention to replacing the tip during use.
