UV-1100 UV-Vis spectrophotometer for the determination of volatile phenols in water - 4-aminoantipyrine spectrophotometry

Determination of volatile phenols in water - 4-aminoantipyrine spectrophotometric method

Key words: determination of volatile phenols in water; 4-aminoantipyrine spectrophotometry; US analytical instrument ; UV-1100; UV-1200

$Src="http://i.bosscdn.com/blog/nophoto.gif" /></p>1, Volatile phenol source and hazard (1) Meaning: According to whether phenol can be distilled together with water vapor, It is a volatile phenol and a non-volatile phenol. Volatile phenols generally refer to the classification of boiling points below 230 Â° C and usually belong to monohydric phenols. (2) Source: Phenols mainly come from wastewater such as refining, gas washing, coking, paper making, ammonia synthesis, wood preservative and chemical industry. (3) Hazard: The classified substances are highly toxic substances. When the human body ingests a certain amount, acute poisoning symptoms may occur. Drinking contaminated water for a long time may cause dizziness, rash, itching, anemia and various nervous system symptoms. . When water contains low concentrations (0.1-0.2 mg/L) of phenols, it can cause odor of fish, and poisoning death occurs at high concentration (>mg/L). Wastewater with a high concentration of phenol is not suitable for irrigation in farmland, otherwise the crop will die or reduce production. The water contains traces of phenols, which can produce specific chlorophenol odor when chlorinated. 2. Selection of methods for determination of volatile phenols 4-aminoantipyrine spectrophotometry is commonly used in various countries. When the content is high (>0.5mg/L), the direct method is used; when the content is low (<0.5mg/L), the chloroform extraction method is adopted. 3. Collection of water samples Water samples were collected using glass instruments. After the water sample is collected, it should be checked in time for the presence or absence of oxidant. If necessary, add an excess of ferrous sulfate, immediately add phosphoric acid to pH = 4.0 (indicated by methyl orange), and add an appropriate amount (2ml) of copper sulfate (1g / L) to inhibit the biooxidation of phenols by microorganisms, while It should be refrigerated (5 ~ 10 Â° C) and measured within 24 hours of collection. 4, pre-distillation [Do (1) (2), re-distillation] After the volatile phenol in water is distilled, it can eliminate the interference of color and turbidity. However, when the water sample contains interfering substances such as oxidants, oils, and sulfides, it should be properly pretreated before distillation. (1) Oxidizer: When the water sample is acidified and drops on the potassium iodide-starch test paper, blue color indicates the presence of an oxidizing agent. Excess ferrous sulfate can be added for removal. (2) Sulfide: When a small amount of sulfide is contained in the water sample, the pH of the water sample is adjusted to 4.0 (indicated by methyl orange) with phosphoric acid, and an appropriate amount of copper sulfate (1 g/L) is added to remove copper sulfide. When the content is high, the phosphoric acidified water sample is placed in a fume hood to be stirred and aerated to cause hydrogen sulfide to escape. (3) Oil: The water sample is transferred into the separatory funnel, and the oil is separated and allowed to stand. After adding the granular sodium hydroxide to pH=12.0~12.5, it is extracted with carbon tetrachloride (40 ml per liter of sample). The carbon tetrachloride was extracted twice. The carbon tetrachloride layer was discarded. The extracted water sample was transferred to a beaker and heated in a water bath in a fume hood to remove residual carbon tetrachloride and adjusted to pH 4 with phosphoric acid. 0. When the concentration of petroleum is high, treatment with n-hexane is better than treatment with carbon tetrachloride. (4) Organic or inorganic reducing substances such as formaldehyde and sulfite: The appropriate amount of water can be separated into the separatory funnel, and the water sample is made acidic by adding sulfuric acid. It is added in 50 ml, 30 ml, 30 ml of diethyl ether or dichloromethane. Phenol, combined with dichloromethane or ether layer in another separatory funnel, add 4ml, 3ml, 3ml of 10% sodium hydroxide solution in batches for back extraction, transfer phenols into sodium hydroxide solution, and combine The alkali extract is transferred to a beaker and heated on a water bath to remove residual extraction solvent, and then the alkali extract is diluted with water to the original water sample volume. At the same time, the water is used as a blank test. Note: Ether is a low boiling, flammable and anesthetic organic solvent. Be careful when using it. There should be no open flame around and operate in the fume hood. When the room temperature is high, the water sample and the ether should be placed in an ice water bath to cool down, and then the extraction operation, each extraction should be completed as soon as possible. 5,4-aminoantipyrine direct photometric method principle Phenolic compounds react with 4-aminoantipyrine in the presence of iron in pH 10.00Â±0.2 medium to form orange-red indophenol The Bilin dye has an aqueous solution with maximum absorption at a wavelength of 510 nm. Studies have shown that in the phenolic compounds, the hydroxy para-substituent prevents the reaction from proceeding; except halogen, carboxyl, sulfonate, hydroxy and methoxy, most of which can be substituted; ortho-nitro Prevents the formation of the reaction, while the meta-nitro group does not completely prevent the reaction: the coupling of the aminoantipyrine with the phenol is more common in the para-position, when the para position is alkyl, aryl, ester, nitro, benzene The acyl group, the nitroso group or the aldehyde group is substituted, and when the ortho position is unsubstituted, no color reaction occurs. The minimum detectable concentration of phenol was 0.1 mg/L as measured by a cuvette with an optical path of 20 mm. 6. Reagents (1) Phenol standard storage stock solution: Weigh 1.00g of leucophenol (C<sub>6</sub>H<sub>5</sub>OH) and dissolve it in water, and transfer it to a l000ml volumetric flask. Dilute to the mark and store in a refrigerator at 4 Â° C for at least one month. (2) Calibration of stock solution (calibration principle: potassium bromate-potassium bromide, acidity, bromine formation, quantitative reaction with phenol, excess potassium bromate oxidizes potassium iodide to precipitate iodine, titrated with sodium thiosulfate. Potassium acid-potassium iodide calibration) (3) Phenol intermediate solution: The phenol stock solution was diluted with water to 10 Î¼g/ml of phenolic standard solution. Prepared on the same day of use. (4) Buffer solution (pH 10): Weigh 20 g of ammonium chloride dissolved in 100 ml of ammonia water, stopper, and store in a refrigerator. (5) 2% 4-aminoantipyrine solution: Weigh 2 g of 4-aminoantipyrine dissolved in water, diluted to 100 ml, and stored in a refrigerator for one week. Note: Solid reagents are easily deliquescent and oxidized and should be stored in a desiccator. (6) 8% iron solution: Weigh 8g of iron dissolved in water, dilute to 100ml, and store in the refrigerator for one week. (7) Copper sulfate (1 g/L) (8) Phosphoric acid (9) 5% ferrous sulfate: 5 g of ferrous sulfate solid was weighed and dissolved in 100 ml of water. 7. Analysis step (1) The calibration curve is drawn in 8 50ml colorimetric tubes, adding 0.00, 0.50, 1.00, 3.00, 5.00, 7.00, 10.00, 12.50ml, and a concentration of 10Î¼g/ml of phenol standard liquid. , add water to the 50m1 mark. Add 0.5m1 buffer solution and mix. At this time, the pH value is 10.00Â±0.2, and add 4-aminoantipyrine solution 1.0m1 to mix. Add 1.0m1 iron solution, mix well, place it for 10min, immediately at 510nm wavelength, with a light path of 20mm cuvette, with water as a reference. The absorbance was measured. Water was used instead of the water sample, and after distillation, the same procedure was carried out according to the water sample, and the result was used as a blank correction value for the water sample measurement. (2) Determination of water sample An appropriate amount of the distillate was placed in a 50 m1 colorimetric tube and diluted to a 50 ml mark. The absorbance was measured in the same manner as in the drawing of the calibration curve, and finally the absorbance obtained in the blank test was subtracted. (3) After the data processing absorbance is corrected by blank, the regression equation of absorbance to phenol content (Î¼g) is obtained, and the absorbance of the water sample is subtracted from the blank value, and then substituted into the regression equation to obtain the volatile phenol content in the water sample, and according to Calculate the volatile phenol content (phenol, mg/L) in the water sample. Finally, draw a calibration curve of absorbance versus phenol content (Î¼g), and mark the measurement points and their water samples in the figure. 8.4-Aminoantipyrazine Extraction Spectrophotometry Principle Orange-red antipyrine dye produced by the reaction of phenolic compound with 4-aminoantipyrine in the presence of iron in pH=10.00Â±0.2 medium It can be extracted by dichloromethane and has only maximum absorption at a wavelength of 460 nm. The method is suitable for the determination of volatile phenols in drinking water, surface water farmers, groundwater and industrial wastewater. The minimum detectable concentration was 0.002 mg/L; the upper limit of determination was 0.12 mg/L. Key words: determination of volatile phenols in water; 4-aminoantipyrine spectrophotometry; analysis instrument ; UV-1100; UV-1200</p> </div> <div class=" Tech-detail-share">  <div class="bdsharebuttonbox"> <a href="#" class="bds_qzone" data-cmd="qzone" title="Share to QQ Space"></a> <a href="#" class="bds_tsina" data-cmd="tsina" title="Share to Sina Weibo"></a> <a href="#" class=" Bds_weixin" data-cmd="weixin" title="Share to WeChat"></a> <span>Share to:</span> </div> <script>window._bd_share_config = { "common": { "bdSnsKey ":}, "bdMini": "1", "bdMiniList": false, "bdPic": "", "bdStyle": "2", "bdSize": "16" }, "share": {} }; with (document) 0[(getElementsByTagName($

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