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Phenol belongs to high toxic substances. The higher the degree of substitution of phenol, the greater the toxicity, the teratogenic and carcinogenic effect of methyl derivatives of phenol. The acute poisoning symptoms will appear when the human body takes a certain amount; Drinking water contaminated with phenol for a long time can cause dizziness, itching, anemia and nervous system disorders. When the phenol content in water is more than 5mg/l, it will cause fish poisoning and death. When chlorination and disinfection of water, phenols can react with chlorine gas to produce chlorophenols, which makes the water body produce obvious odor. The main pollution sources of phenol are oil refining, coking, gas generating stations, wood corrosion prevention and some industrial wastewater such as phenolic resin.
Different phenols have different boiling points. Phenols can be divided into volatile phenols and non-volatile phenols by whether they can volatilize with water vapor. Generally, the volatile phenols with boiling point below 230 ℃ are volatile phenols, while those with boiling point above 230 ℃ are non-volatile phenols. The main analytical methods of phenol are brominated titration (gb7491-87), 4-antipyrine spectrophotometry (gb7490-87), chromatography, etc. Whether bromination titration or spectrophotometry, when there are oxidants, reducers, Oils and some metal ions in water samples, they should be eliminated and pre distilled. For example, the free chlorine is reduced by adding ferrous sulfate; Copper sulfate is added to sulfide to precipitate or escape in the form of hydrogen sulfide under acidic conditions; The oil is extracted and removed by organic solvent. The distillation has two functions: one is to separate volatile phenol, the other is to eliminate the interference of color, turbidity and metal ions.
This method is suitable for the determination of volatile phenol in drinking water, surface water, groundwater and industrial wastewater, and the range of determination is 0.002-6mg / L. When the concentration of volatile phenol in water is lower than 0.5mg/l, chloroform extraction method can be used; If the concentration is higher than 0.5mg/l, direct spectrophotometry can be used. Oxidants, oils, sulfides, organic or inorganic reducing substances and aromatic amines in water samples can interfere with the determination of volatile phenol.
bromination titration method
In solutions containing excess bromine (produced by potassium bromate and potassium bromide), phenol reacts with bromine to produce tribromophenol and further generates bromotribromophenol. The remaining bromine and potassium iodide release the iodine. At the same time, bromotribromopherol also reacted with potassium iodide to replace the iodine. The free iodine released by titration with sodium thiosulfate standard solution is calculated according to its consumption.
Spectrophotometric Determination of 4-aminoantipyrine
bromination titration method
Range: 0-5mg / L (range extendable))
The analyzer has successfully passed a series of tests to facilitate installation and setting. During installation, just connect reagent, sample, waste liquid pipeline and power line, and set parameters to start. Automatic calibration, automatic cleaning, automatic testing, automatic data storage. Long time automatic control, low maintenance, low operation cost, automatic operation, low reagent consumption, short preparation time, simple maintenance, no special electrician training.