Shen ChangHong The measurement of COD, ammonia nitrogen, total phosphorus and total nitrogen are all developed according to the documents issued by the State Administration of protection, and the results are accurate and effective. Closed digestion colorimetry was used for COD, Nessler's Reagent Colorimetry for ammonia nitrogen, closed digestion colorimetry for total phosphorus and closed digestion ultraviolet spectrophotometry for total nitrogen. The instrument is widely used in environmental testing, sewage treatment, scientific research institutions and colleges. So, how to operate the total phosphorus analyzer?
Measurement of total phosphorus by ammonium molybdate method
Shenchanghong used ammonium molybdate method to measure total phosphorus, which can be used to determine the content of total phosphorus in surface water, domestic sewage and industrial wastewater. Measurement range: 0.01-2.00mg/l, 2.00-10.0mg/l.
Under neutral condition, potassium persulfate was used to digest the water sample and convert the phosphorus contained into orthophosphate. In the acid medium, orthophosphate reacts with ammonium molybdate to form phosphomolybdic heteropoly acid in the presence of antimony salt, which is immediately reduced by ascorbic acid to form a blue complex, and the color is compared at the wavelength of 700nm.
Analysis steps of total phosphorus measurement by ammonium molybdate method
1. When the total phosphorus concentration is 0.01-2.00mg/l (total phosphorus ﹤ L):
Preparation of blank sample: take 5.0ml distilled water and put it into a clean special digestion colorimetric tube, then add 1.0ml reagent (I), tighten the plug and shake the mixture well;
Sample preparation: take 5.0ml of the sample to be tested and put it into a clean dedicated digestion colorimetric tube, then add 1.0ml of reagent (I), tighten the plug and shake the mixture well.
When the digestion temperature reaches 120 ℃, insert the digestion colorimetric tube into the digestion furnace hole of the digester in turn, put on the protective cover, and conduct digestion (see the instructions of dis-16 / 25 / 30 / 36 multi-functional numerical control digester for specific operation and precautions). The buzzer will give a finish alarm after 30 minutes digestion.
Cool and take out the digestion colorimetric tube and put it into a dry beaker, cool it for 2min naturally, then cool it to room temperature, then add 0.2ml reagent (II) and 0.3ml reagent (III), shake it with a stopper, allow it to stand for color development for 15min, and test on the machine. (Note: when cooling, it is necessary to prevent the cooling water from entering the digestion colorimetric tube or contaminating the tube plug at the tube mouth, which will affect the measurement results. )
2. When the total phosphorus concentration is 2.00-10.0mg/l (total phosphorus · h):
Preparation of blank sample: take 5.0ml distilled water and put it into a clean special digestion colorimetric tube, then add 1.0ml reagent (I), tighten the plug and shake the mixture well.
Preparation of sample 1.0ml of the sample to be tested is placed in a clean dedicated digestion colorimetric tube, then 4.0mL of distilled water is added, then 1.0ml of reagent (I) is added, tighten the plug and shake the mixture well.
When the digestion temperature reaches 120 ℃, insert the digestion colorimetric tube into the digestion furnace hole of the digester in turn, cover the protective cover, and conduct digestion (see the instructions of dis-16 / 25 / 30 / 36 multi-functional numerical control digester for specific operation and precautions). The buzzer will give a finish alarm after 30 minutes digestion.
Cool and take out the digestion colorimetric tube and put it into a dry beaker, cool it for 2min naturally, then cool it to room temperature, add 0.2ml reagent (II) and 0.3ml reagent (III), shake it with a stopper, allow it to stand at room temperature for 15 minutes for color development, and test on the machine. (Note: when cooling, it is necessary to prevent the cooling water from entering the digestion colorimetric tube or contaminating the tube plug at the tube mouth, which will affect the measurement results. )
3. For blank measurement, wipe the blank colorimetric tube to be measured, put the colorimetric tube into the colorimetric hole, click the "blank measurement" item under the main menu, press the "confirm" key when the absorption value is stable, and the instrument will automatically set to zero.
4. For sample measurement, wipe the colorimetric tube of the sample to be measured and put it into the colorimetric hole. Under the main menu, click the item "sample measurement", the instrument will enter the sample measurement interface and display the total phosphorus concentration value (mg / L) directly.
Precautions for total phosphorus measurement
During the experiment, the glassware and colorimetric tube used shall be cleaned with sulfuric acid if necessary.
Before the prepared sample is tested on the machine, ensure that the outer wall of the colorimetric tube is wiped clean without water drops or hand marks.
When analyzing water samples, shake it evenly before taking. Besides, the water sample cannot be filtered.
