Spectrophotometric determination of nitrate content by thymol - Master's thesis

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Determination of nitrate content by thymol spectrophotometry

Key words: thymol spectrophotometry; nitrate; US analytical instrument ; UV-1100; UV-1200 $Width="805" height="537" src="http://i.bosscdn.com/blog/nophoto.gif" />This specification specifies the use of thymol (thymol) spectrophotometric determination of drinking The content of nitrate nitrogen in water and its source water. This specification is applicable to the determination of nitrate nitrogen in drinking water and its source water. The minimum detection quality of this specification is 0.12 Î¼g of nitrate nitrogen (in terms of N). If 1.0 ml of water is taken, the minimum detected mass concentration is 0.12 mg/L of nitrate nitrogen (in terms of N). Nitrite is positively interfered with this specification and can be removed with ammonium sulfamate; chloride is negatively interfered with this specification and can be eliminated with silver sulfate. Principle 1.0 Nitrate thymol forms a nitro compound in a concentrated sulfuric acid solution, undergoes molecular rearrangement in an alkaline solution to form a yellow compound, which is determined by colorimetry. 2.0 reagent 2.1 ammonia water (Ï<sub>20</sub>=0.88g/ml). 2.2 acetic acid solution (1+4). 2.3 Ammonium sulfamate solution (20g / L): Weigh 2.0g ammonium sulfamate (NH<sub>4</sub>SO<sub>3</sub>NH<sub>2</sub> ), dissolved in acetic acid solution, and diluted to 100 ml. 2.4 Thymol phenol acetic acid solution (5g / L): Weigh 0.5g thymol [(CH<sub>3</sub>)(C<sub>3</sub>H<sub>7</ Sub>)C<sub>6</sub>H<sub>3</sub>OH, Thymol, also known as thymol], dissolved in absolute ethanol and diluted to 100 ml. 2.5 silver sulfate sulfuric acid solution (10g / L): Weigh 1.0g silver sulfate (AgSO<sub>4</sub>), dissolved in 100mi sulfuric acid (Ï<sub>20</sub>=1.84g/ml )in. 2.6 Nitrate nitrogen standard stock solution [Ï(NO<sub>3</sub>-N)=1mg/ml]: Weigh 7.218g of potassium nitrate dried at 105~110 Â°C for 1 hour (KNO<sub> 3</sub>), dissolved in pure water and dissolved to 1000 ml. Add 2ml as a preservative. 2.7 Nitrate Nitrogen Standard Use Solution [Ï(NO<sub>3</sub>-N)=10ug/ml]: Dilute 5.00ml of nitrate nitrogen standard stock solution (3.6) to 500ml. 3.0 Instrument 3.1 with a colorimetric tube, 50ml 3.2 spectrophotometer. US Instruments ; UV-1100; UV-12004.0 Analysis Step 4.1 Take 1.00ml water sample in a dry 50ml colorimetric tube. 4.2 Another 50 ml colorimetric tube was taken, and the standard solution of nitrate nitrogen (3.7) was added: 0, 0.05, 0.10, 0.30, 0.50, 0.70 and 1.00 ml, and diluted to 1.00 ml with pure water. 4.3 Add 0.1 ml of ammonium sulfamate solution to each tube, shake and place for 5 min. 4.4 Each was added 0.2 ml of thymol ethanol solution (3.4). Note: Add directly to the solution from the center of the colorimetric tube and do not run down the tube wall. 4.5 Shake well and add 2ml silver sulfate sulfuric acid solution (3.5), mix and put for 5min. 4.6 Add 8ml of pure water, mix and add ammonia water (3.1) until the solution yellow reaches the deepest. The silver chloride precipitate was dissolved (about 9 ml). Add pure water to the 25ml mark and mix. 4.7 Absorbance was measured at 415 nm wavelength, 2 cm cuvette with pure water as a reference. 4.8 Draw a standard curve and find the mass M of nitrate nitrogen in the sample from the curve. 5.0 Calculate the nitrate content in water by the following formula: where: X - nitrate content in water, mol / l; M - mass of nitrate nitrogen in the sample M, mg; V - water sample volume; ml. 4. Determination of alkalinity - indicator method This method is applicable to the determination of alkalinity in circulating cooling water and natural water. 1.0 Principle Using phenolphthalein as an indicator, the water sample is titrated with a standard acid solution to reach the end point. The measured alkalinity is called phenolphthalein alkalinity. At this time, all the hydroxide and one half of the carbonic acid contained in the water sample are included. The root is combined with acid, and its reaction is as follows: OH<sup>-</sup>+H<sup>+</sup>=H<sub>2</sub>OCO<sub>3</sub><sup> 2-</sup>+H<sup>+</sup>=HCO<sub>3</sub><sup>-</sup> adding a methyl orange indicator to the water sample titrated with phenolphthalein, Continue to the standard acid solution titration to reach the end point (including the amount of phenolic alkalinity), the measured alkalinity is called methyl orange alkalinity, also known as total alkalinity, at this time all the bicarbonate contained in the water sample is And, the reaction is as follows: HCO<sub>3</sub><sup>-</sup>+H<sup>+</sup>â†’H<sub>2</sub>CO<sub>3</ Sub><br clear="all" />H<sub>2</sub>O+CO<sub>2</sub>â†‘2.0 Reagent 2.1 0.1% methyl orange in water. 2.2 0.5% phenolphthalein 50% ethanol solution. 2.3 bromocresol quinone-methyl red indicator solution. Three parts of a 0.1% bromocresol green ethanol solution was mixed with 1 part of a 0.2% methyl red ethanol solution. 2.4 0.1mol/L hydrochloric acid standard solution 2.4.1 Preparation: Measure 9mL hydrochloric acid (excellent pure) into 1000mL water. 2.4.2 Calibration: Weigh 0.2kg of reference anhydrous sodium carbonate at 270~300Â°C to constant weight, and weigh it to 0.0002g. Dissolve in 50mL water, add 10 drops of bromocresol green methyl red mixed indicator solution, use 0.1mol/L hydrochloric acid solution to drop the solution from green to dark red, boil for 2 minutes, continue to titrate after cooling until the solution is dark red. At the same time, do a blank test. 2.4.3 Calculate the molar concentration of hydrochloric acid standard solution M (mol/L) calculated as follows: <table cellspacing="0" cellpadding="0" border="0"> <tbody> M= GÃ—2 Ã— 1000 (V<sub>1</sub>-V<sub>2</sub>)Ã—105.99 </tbody></table> in the formula: Gâ€”the weight of anhydrous sodium carbonate, gram; V<sub> 1</sub> - the amount of hydrochloric acid solution, ml; V <sub> 2</sub> - the amount of the blank test hydrochloric acid solution, ml; 105.99 - the molar mass of sodium carbonate, g / mol. 3.0 Instrument Burette: 10 mL microburette. 4.0 Analysis step 4.1 Determination of phenolphthalein alkalinity Pipette 100mL water sample in 250mg/L conical flask, add three drops of phenolphthalein indicator, if it does not develop color, it means that the phenolic alkalinity is zero, if it is red, use The 0.1 mol/L hydrochloric acid standard solution was titrated until the red color just faded to the end point, and the amount of the hydrochloric acid standard solution was recorded as V<sub>3</sub>. 4.2 Determination of total alkalinity In the water sample after the determination of phenolphthalein, add 1 drop of methyl orange indicator, continue to titrate with 0.1mol / L hydrochloric acid standard solution until the orange red is just the end point. Record the amount of acid standard solution (including phenolic alkalinity) V<sub>4</sub>. 5.0 Calculation of analytical results 5.1 Phenolphthalein P in water samples (mg/L, calculated as CaCO<sub>3</sub>) Calculated as follows: <table cellspacing="0" cellpadding="0 " border="0"> <tbody> P= V<sub>3</sub>Ã—MÃ— 100.08 Ã—1000 2 V<sub>w</sub> </tbody></table> where: V< Sub>3</sub>â€”when the phenolphthalein indicator is used, titrate the volume of the standard solution of hydrochloric acid consumed, milliliter; M-hydrochloric acid standard solution molar concentration, mole/liter; 100.08â€”molar mass of calcium carbonate, g/mol; V <sub>w</sub>â€”water sample volume, ml. 5.2 Calculation of total alkalinity (methyl orange alkalinity): Total alkalinity T (mg/L, calculated as CaCO<sub>3</sub>) in water sample: Calculated as follows: <table cellspacing=" 0" cellpadding="0" border="0"> <tbody> T= V<sub>4</sub>Ã—MÃ— 100.08 Ã—1000 2 V<sub>w</sub> </tbody></table >ä¸ä¸:V<sub>4</sub>- After titrating the volume of the standard solution of hydrochloric acid consumed with methyl orange indicator, milliliter; molar concentration of M-hydrochloric acid standard solution, mole/liter; 100.08-calcium carbonate Molar mass, g/mol; V<sub>w</sub> - water sample volume, ml. 5.3 The alkalinity in the water is all formed by hydroxides, carbonates, and bicarbonates, and it is considered that there are no other weak inorganic and organic acids, and it is assumed that the hydroxide and the bicarbonate coexist. The relationship between hydroxide, carbonate and bicarbonate in water is shown in Table 1-6. Table 1-6 Various alkalinity relationships <table cellspacing="0" cellpadding="0" border="0"> <tbody> Titration results hydroxide alkalinity is calculated by CaCO<sub>3</sub> The salinity is calculated by CaCO<sub>3</sub> as the weight of carbonate alkalinity by CaCO<sub>3</sub> P=0 0 0 T 2P<T 0 2P T-2P 2P=T 0 2P 0 2P>T 2P-T 2(TP) 0 P=TT 0 0 </tbody></table>6.0 Allows the difference in alkalinity to be measured in the range of 25~250mg/L (calculated as CaCO<sub>3</sub>) The difference between the two results is not more than 2.5 mg / L. The 7.0 results show that the arithmetic mean of the two results is taken in parallel as the alkalinity of the water sample. Key words: thymol spectrophotometry; nitrate; mass spectrometer ; UV-1100; UV-1200</p></dl> </div> </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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