When testing the turbidity parameters of water quality samples, the ability to accurately prepare a standard solution of formazin is a weight technology to ensure the accuracy of turbidity measurement results. Therefore, as a qualified water quality inspector, you must be able to master formazin The preparation method of the standard solution, understand the reagents and equipment involved, and the matters needing attention during the operation.
Reagents and equipment used for formazin standard solution
1. Zero turbid water
2. Six times tetrakisamine
3. Hydrazine sulfate (hydrazine sulfate)
4. Volumetric flask 50, 100mL scattered light turbidity meter.
5. Pipette 5, 10, 15, 20, 25mL
6. Analytical balance
7. Ear wash ball
Preparation method of formazin turbidity standard solution
1. Weighing: Weigh 10.00g hexamethylenetetramine and 1.000g hydrazine sulfate respectively.
2. Dissolution: Dissolve the weighed two reagents separately in a small amount of zero turbidity water.
3. Constant volume: Use zero turbidity water to dilute the dissolved medicine to 100 mL, and then shake it until uniform.
4. Prepare formazin standard stock solution: pipette 5.00mL hexamethylenetetramine solution and 5.00mL hydrazine sulfate solution into a 100mL volumetric flask, shake well, then stand for 24h at 25±3 degrees Celsius, and then dilute to Scale. The turbidity of this standard stock solution is 400FNU. This standard stock solution is stored in a dark place at 25±3 degrees Celsius and can be used stably for 4 weeks.
Prepare Formazin Standard Control Solution
Take the standard stock solutions of formazide 5.0, 10.0, 12.5, 15.0, 25.0mL and place them in 5 50mL volumetric flasks respectively, dilute to the mark with zero turbidity water, shake them evenly, their turbidity is 40, 80, 100, 120, 200FNU. The diluted standard solution with a turbidity value of less than 200FNU cannot be stored for a long time, and should be used along with it. If there are obvious particles in the solution, it has expired.
Precautions for preparing formazin turbidity standard solution
1. Precise preparation of formazin standard solution is an important technology to ensure the accuracy of turbidity measurement results. Pay attention to each step of preparing the standard solution. When shaking the stock solution, it should be uniform, and the pipetting should be accurate. When pouring the zero turbidity solution, you should pay attention to the scale. The low turbidity standard solution should use a large-capacity measuring bottle to reduce the preparation. error.
2. Select the standard solution for calibration, the content should be the appropriate full-scale value of the measurement range, and it should be shaken well before calibration. For low turbidity determination and higher precision measurement, the difference between sample bottles should be considered, and the same bottle must be used for calibration and detection. Zero turbidity water should be used for zero calibration, and distilled water can be used when the requirements are not high.
