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Spectrophotometric test of trace elements
Key words: spectrophotometry; trace elements; aesthetic instrument ; UV-1800A
1. After the tin---benzophenone colorimetric sample is digested, the tetravalent tin ion forms a sparingly soluble orange-red complex with benzophenone in a weakly acidic solution, in the presence of a protective colloid and a standard series. Compare quantitative. 1, tartaric acid solution (100 g / L) 2, ascorbic acid solution (10 g / L): prepared at the time of use. 3, animal glue solution (5 g / L): prepared at the time of use. 4. Phenolphthalein indicator solution (10 g/L): dissolved in ethanol. 5. Ammonia (1+1)6, sulfuric acid (1+9)7, benzophenone solution (0.1g/L): Weigh 0.020 g of benzophenone (1,3,7-trihydroxy- 9-phenyl)蒽醌), add a small amount of methanol and sulfuric acid (1+9) to dissolve in a few drops, dilute to 200 mL with methanol. 8. Tin standard use solution (10.0ppm): Pipette 1.00mL-5.00mL sample digestive solution and the same amount of reagent blank solution, respectively, in 25mL colorimetric tube. Pipette 0, 0.20, 0.40, 0.60, 0.80, 1.00 mL of tin standard solution (equivalent to 0, 2.0, 4.0, 6.0, 8.0, 10.0 ug tin), placed in a 25 mL colorimetric tube. Add 0.5 mL of tartaric acid solution (100g/L) and 1 drop of phenolphthalein indicator solution to the sample, digestive solution, reagent blank and tin standard solution, mix well, and add ammonia (1+1) to neutralize to light red. Add 3 mL of sulfuric acid (1+9), 1 mL of animal glue solution and 2.5 mL of ascorbic acid solution, add water to 25 mL_, mix well, add 2 mL of benzophenone solution, mix well, measure after 1 hour, use 2 cm ratio The color cup is adjusted to zero by water, and the absorbance is measured at a wavelength of 490 nm by a visible spectrophotometer. After subtracting the zero-tube absorbance from each standard point, a standard curve is calculated or a linear regression equation is calculated, and the absorbance of the sample is compared with the curve or the generation is replaced. The equation finds the content. Second, the organic matter in the phosphorus food is oxidized by acid, and the phosphorus is combined with ammonium molybdate under acidic conditions to form ammonium phosphomolybdate. This compound is reduced to a blue compound, key blue, by hydroquinone or sodium sulfite. The absorbance of the key blue was measured at a wavelength of 660 nm using a visible spectrophotometer. 1, 15% sulfuric acid solution: 2, ammonium citrate solution: 1g / 200ml, diluted with 15% sulfuric acid solution. 3, sodium sulfite solution: 20g / 100ml, temporarily prepared, otherwise the key blue solution can be turbid. 4, phosphorus standard use solution (10.0ppm): draw 0.625, 1.25, 2.5, 3.75, 5, 6.25 ml phosphorus standard use solution ( Corresponding to the phosphorus content of 0, 5, 10, 20, 30, 40, 50 ug) were placed in a 25 mL stoppered test tube. Accurately take 2.5 mL of the sample solution and the same amount of blank solution, and place them in a 25 ml stoppered test tube. Add 2.5 mL of molybdic acid solution in turn and shake for a few seconds. Add 1.25 ml of sodium sulfite solution, 1.25 mL of hydroquinone solution, and shake well. Add water to the mark and mix. After standing for 30 minutes, the absorbance was measured at a wavelength of 660 nm of a spectrophotometer. A standard curve was plotted for the phosphorus content based on the measured absorbance. 3. After the nickel in the nickel sample is extracted with dilute acid, ammonium persulfate is used as an oxidant in a strong alkaline solution, and nickel and dimethylglyoxime form a reddish-brown complex, which is quantitatively compared with the standard series. The national standard is non-digestive, is it enough to call more points, but consider that the digestion time may be too long. 1, dimethylglyoxime (C4H3N202,) monoethanol solution (10g / L): 2, potassium sodium tartrate solution (500 g / L): 3, sodium hydroxide solution (100g / L): 4, ammonium persulfate solution (60g/L): ready-to-use, 5, nickel standard use solution (1.0ug): draw 0,1,2,4,6,8,10,12,14,16ml nickel standard use solution, respectively 25mL with a colorimetric tube. How much does the sample suck? Add 1.25mL sodium potassium tartrate solution, 3.75mL sodium hydroxide solution and 1.25mL ammonium persulfate solution to the sample and standard tube, and mix for 3 minutes. Add 0.5 mL of dimethylglyoxime-ethanol solution to each, add water to 25 mL, and mix. After standing for 15 min, use a 3 cm cuvette to adjust the zero point with water, measure the absorbance at a visible spectrophotometer wavelength of 470 nm, and compare the standard curve. 4. Microwave digestion - Spectrophotometric determination of boron in soybeans respectively absorb 0, 0.5, 1.5, 2.5, 3.5, 5, 6, 7.5mL boron standard solution in 25mL colorimetric tube; add 5mL ammonium acetate buffer Add 2.5 mL of the imine solution, mix well, add water to the mark, and shake well. The absorbance was measured at 420 nm on a visible spectrophotometer for 1 h. The sample was adjusted to pH 6.5 with (1+1) HN3·H2O solution. 1. Boron standard use solution (5.0ppm): 2, ammonia 1+1:3, ammonium acetate buffer solution (pH 6.7): Take 115 g of ammonium acetate, dilute to 500 mL, then add 33.5 g EDTA, mix. Methylenimine solution (9.0 g / L): Now with. Weigh 1.8g of imine and 4 g of ascorbic acid, dissolved in 200mL of water, slightly heat. V. Determination of Boron in Water Quality - Methylenimine-H Acid Photometric Method The detection concentration of this method is 0.03ppm, and the upper limit of determination is 5.0ppm (equivalent to 10.0ppm of HBO2). It can be used for the determination of boron in drinking water and surface water. Tin, antimony, mercury and chromogenic reagents form a white precipitate. Aluminium, titanium, zirconium, vanadium, gallium, molybdenum (VI) forms yellow, copper and chromium produce brownish yellow, and iron (III) iron (II) interferes with the determination. Masking, the presence of potassium and sodium slows down the reaction but prolongs the reaction time, and after 6 hours, the measurement is performed to eliminate interference. Principle In a pH 5.2 hydrochloric acid and ammonium acetate buffer solution, boron and methylimine-H acid form a water-soluble methylimine H-borate brown-yellow compound with a maximum absorption wavelength of 410-420 nm. The color speed was slow, and the color developed completely after 6 h. The compound was stable within 30 h. Reagents: 1, ammonium acetate aqueous solution 500g / L: 2, 1 + 4 hydrochloric acid solution: 40ml diluted to 200ml3, EDTA saturated solution: solubility at room temperature is 0.2g / L, EDTA disodium salt solubility is greater, at 22 ° C 11.1 g can be dissolved per 100 ml of water, and the concentration of this solution is about 0.3 mol/L-1. Since the aqueous solution of EDTA disodium salt is mainly H2Y2-, the pH of the solution is close to 4.42. The solubility is relatively small and is affected by temperature for a long time. It can be considered that its solubility is constant. Generally, it is prepared by using sodium to obtain a saturated solution. 4. Boron standard use solution (10ppm): 5. Methyl imine-H acid developer: Accurately weigh 0.50g of methylimine-H acid and 2g of ascorbic acid dissolved in 100mL of deionized water. Determination: Accurately transfer HBO2 standard use solution 0, 0.1, 0.3, 0.625, 1.25, 2.5, 7.5, 15ml into 25ml colorimetric tube; add 0.50mL EDTA saturated solution, 2.5mL hydrochloric acid solution (1+4), 5.0 mL ammonium acetate solution, shake well, add 6.00mL of the imine-H acid developer, shake well and dilute to the mark with water, shake. After measuring the darkness for 6 h, use a 10 mm cuvette at a wavelength of 420 mm at a wavelength of 420 mm to determine the absorbance of the blank test solution. (1) pH has an effect on the color reaction. The suitable pH range is 5.2~5.8. (2) The chromogenic reagent imine-H acid is easily oxidized and should be stored in a brown bottle with a plastic gland. The reagent is now used together with ascorbic acid to prevent oxidation. (3) When the concentration of HB02 is 6.0 mg/L, The addition of 6.0 mL of the developer to the 50 mL test solution is the best complex ratio. (4) Pretreatment and color development of boron samples often contained in hard glass. Glassware used in glassware should not be used for long-term contact with the sample solution. For other glassware, a full-program blank test should be performed first. Use the method of subtracting the blank to eliminate the influence of the glassware. (5) The water used to prepare the reagents needs to be distilled from the quartz distiller or deionized water. 6. Spectrophotometric determination of titanium content in Hedyotis diffusa. Accurately transfer 10 ppm of titanium standard solution 0, 1, 2, 3, 4, 5 mL into 25 mL volumetric flasks, each adding 1:1 hydrochloric acid 10 mL, 10% ascorbic acid 0.5 mL, shake well, add 2% diantipyrylmethane 5mL each, dilute to the mark with water, shake and let stand for 30 min. The wavelength was 383 nm. The sample was spiked with 10% ascorbic acid to complete fading. Add 2% diantipyrine methane 5mL, dilute with water to the mark and shake. 1, titanium standard use solution (10ppm); 2, hydrochloric acid solution 1 mol / L: 3, diantipyrine methane solution 2%: Accurately weigh 10.0g diantipyrine methane powder, with 1 mol / L The hydrochloric acid solution was dissolved and made up to 500 mL. VII. Determination of trace silicon in water by silicon-molybdenum blue-ray method for the determination of silicon by silicon molybdenum blue light method. Generally, at a higher acidity, orthosilicate and ammonium molybdate form β-type yellow silicon molybdenum heteropoly acid, which is reduced to blue with a reducing agent. Silicon molybdenum blue was measured spectrophotometrically at a wavelength of 810 to 820 nm in a visible spectrophotometer. At present, there are many kinds of known reducing agents, and each has its own advantages and disadvantages, such as stannous chloride and ammonium ferrous sulfate. The reduction speed is fast, the sensitivity is high, and the stability is poor; ascorbic acid, silicon molybdenum blue is very stable, and the reduction speed is too Slow; ferrous sulfate and oxalic acid are mixed as a reducing agent, and the mixture has a short stabilization time; amino naphthol sulfonic acid, silicon molybdenum blue, although stable for a long time, is prone to precipitation and reduced reducing power; and metol-Na 2SO3 is used for reduction The agent is prone to precipitation, and the reduction rate is slow and unstable. In this paper, a mixture of sodium formaldehyde sulfoxylate and sodium sulfite was studied and prepared as a reducing agent for the determination of trace silicon in water (silicon molybdenum blue). The experiment proved that its stability, reducing ability, sensitivity and accuracy were good. The reducing agent can be stored for a longer period of time. Standard silicon use solution (20ppm): ammonium molybdate solution: Weigh 7.2 g of ammonium molybdate in a 50mL beaker, add 10mL of distilled water to heat and dissolve, slowly add it to 5mL concentrated sulfuric acid and 11mL concentrated nitric acid, stir evenly. After slightly cooling, dilute to 30mL with water. If it is cloudy, filter it overnight. Tartaric acid solution: 21g/30ml sodium formaldehyde sulfoxylate (reducing agent) solution: Weigh 1.50 g of sodium formaldehyde sulfoxylate and 4.0 g of sodium sulfite In a beaker, add distilled water to dissolve to 30 mL, and store in a brown dropper vial. Determination: Accurately absorb silicon standard solution 0, 0.2, 0.5, 0.7, 0.9, 1.2, 1.5 mL in 25mL colorimetric tube, add 0.2ml ammonium molybdate, shake well, place for 4-5min, then add 0.15ml tartaric acid, Shake well, place for 2 min, add 0.4 ml of reducing agent, dilute to the mark with distilled water, shake well, place in boiling water bath for 3 to 5 minutes, remove the running water and cool to room temperature, at visible wavelength spectrophotometer at wavelengths 810-820 nm and 1 mL In the cuvette, the reagent (or distilled water) is used as a reference to measure the absorbance A value. Eight, photometric method for the simultaneous determination of phosphorus and silicon Phosphorus and silicon and ammonium molybdate can produce a yellow complex, this complex and reducing agent can be reduced to molybdenum blue at the same time, but oxalic acid can quickly destroy phosphorus molybdenum, Moreover, experiments have shown that the absorbance of phosphorus molybdenum blue and silicon molybdenum blue is good in the range of 0 to 2 ppm. Therefore, under certain conditions, the absorbance in the presence of phosphorus and silicon is first measured, and under the same conditions, oxalic acid is added to measure the absorbance of silicon molybdenum blue. The difference between the two is the absorbance of phosphorus molybdenum blue, and then The corresponding phosphorus and silicon contents were found on the corresponding working curves. Ammonium molybdate solution (2.5%): NaF (0.24%)-SnCL2 (0.2%): 2.4 g NaF/100 ml water, plus 0.2 g SnCL2, used on the same day. Oxalic acid solution (1%): sulfuric acid (1mol/L): phosphorus standard use solution (10ppm) silicon standard use solution (10ppm), absorb 0, 1.0, 2.0, 3.0, 4.0, 5.0ml of standard use solution in 25ml colorimetric tube Add 1.2 ml of sulfuric acid (1 mol/L), 2.5 ml of ammonium molybdate solution, heat in a boiling water bath for 30 seconds, and 10 ml of NaF (0.24%)-SnCL2 (0.2%). After cooling, dilute to the mark and shake. Using a 1cm cuvette, the spectrophotometer is visible at 690nm, and the reagent blank is used as a reference to measure the absorbance. 9. After the aluminum sample is treated, the trivalent aluminum ion is in the sodium acetate monoacetate buffer medium, and the chrome azurol S The cetyltrimethylamine bromide reacts to form a blue ternary complex, and the absorbance is measured at a wavelength of 640 nm and quantified in comparison with the standard. 1, 1% (volume fraction) sulfuric acid: 0.1ml diluted to 10ml. 2, sodium acetate monoacetate solution: said 40.8g sodium acetate dissolved in 540mL water, add 3.12ml glacial acetic acid, adjust the pH to 5.5, diluted with water to 600mL, 3, chrome azurol S solution (0.5 g / L): 4, cetyltrimethyl bromide solution (0.2 g / L): 0.04g / 200ml, if necessary, heating and solubilization. 5, ascorbic acid solution (10g / L): when used. 6, aluminum standard use liquid (1.0ppm): should ensure that the sample solution contains 1% sulfuric acid. Pipette 0,0.5,1.0,2.0,3.0,4.0,6.0m L aluminum standard use liquid (equivalent to 0, 0.5, 1.0, 2.0, 4.0, 6.0 ug) were placed in a 25 mL colorimetric tube, and 1 mL of a 1% sulfuric acid solution was sequentially added to each tube. Pipette 1.0 mL of the digested sample solution and place in a 25 mL colorimetric tube. Add 8.0 ml of sodium acetate monoacetate buffer, 1.0 ml of ascorbic acid solution to the standard tube, sample tube and reagent blank tube, mix well, add 2.0 mL of cetyltrimethylammonium bromide solution, mix, add 2.0 mL of chrome azurol S solution, shake well, and dilute to the mark with water. After standing at room temperature for 20 min, the zero point was adjusted on a spectrophotometer with a 1 cm cuvette. The absorbance was measured at a wavelength of 640 nm by an ultraviolet-visible spectrophotometer, and the standard curve was compared and quantified. X. Zinc----Dithizone colorimetric method (primary extraction) After digestion, the zinc ion forms a purple-red complex with dithizone at pH 4.0-5.5, and is dissolved in carbon tetrachloride. Sodium thiosulfate is added to prevent interference with copper, mercury, lead, antimony, silver and cadmium, and is quantified in comparison with the standard series. Reagents: 1. Sodium acetate solution (2 mol/I): Weigh 68 g of sodium acetate (CH, COONa·3H, O), dilute to 250 mL with water, 2. Acetic acid (2 mol/L): take 10.0约左å³ã€‚ The pH of the solution is about 4. 7 or so, the pH of the solution is about 4. 7 or so. Extracted with disulfide gland-tetrachlorocarbon solution (0.1 g/L) several times, 10 mL each time, remove the zinc, until the carbon tetrachloride layer is green, and discard the carbon tetrachloride layer. Then, the excess disulfide trace in the acetic acid monoacetate buffer was extracted with carbon tetrachloride, and the carbon tetrachloride was colorless, and the carbon tetrachloride layer was discarded. 4å·¦å³å·¦å³ã€‚ The sodium thiosulfate solution (250 g / L): sodium acetate solution (2 mol / L) and acetic acid (2 mol / L), the pH of the solution is about 4. 7 or so. Extracted with disulfide gland-tetrachlorocarbon solution (0.1 g/L) several times, 10 mL each time, remove the zinc, until the carbon tetrachloride layer is green, and discard the carbon tetrachloride layer. Then, the excess disulfide trace in the acetic acid monoacetate buffer was extracted with carbon tetrachloride, and the carbon tetrachloride was colorless, and the carbon tetrachloride layer was discarded. 5. 1:1 ammonia 6. Methyl orange indicator solution (2 g / L): Weigh 0.2 g of methyl orange, dissolve with ethanol (20%) and dilute to 100 Ml7. Hydrochloric acid (2 mol / L): amount Take 10 mL of hydrochloric acid, dilute to 60 mL with water, 8. Zinc standard use solution (1.0 ug): 10. Disulfide traces of tetrachlorocyanate solution (0.01 g/L). Pipette 5.0~10.0mL of the digested solution and the same amount of reagent blank solution, respectively, in a 25mL colorimetric tube; draw 0.0, 1.0, 2.0, 3.0, 4.0, 5.0mL zinc standard use solution (equivalent to 0, 1, 2, 3, 4, 5 μg of zinc), placed in a 25 mL colorimetric tube. Add 1 drop of methyl orange indicator solution to the sample digestive solution, reagent blank and zinc standard solution, adjust to red to blue with ammonia water, add 5mL acetic acid-acetate buffer solution and 1mL sodium thiosulfate solution respectively. After mixing, add 10.0 mL of 0 dithizone-carbon tetrachloride solution to a volume of 25 ml. Shake vigorously for 4 min, let stand for stratification, and filter the carbon tetrachloride layer into a 1 cm cuvette via cotton wool. The carbon tetrachloride was adjusted to zero point, and the absorbance was measured at a wavelength of 530 nm of a visible spectrophotometer, and a standard curve was drawn. 11. Zinc reagent - cyclohexanone spectrophotometric determination of zinc in dairy milk powder by drawing 0, 0.5, 1.0, 3.0, 5.0, 7.0, 10.0, 15.0 ml zinc standard solution; adding 2 drops of phenol red indicator hydrogen The sodium oxide (40 g/L) solution was adjusted to red, then adjusted to yellow with hydrochloric acid (1+50), and 0.5 g of ascorbic acid, 5.0 ml of buffer, 2.0 ml of solution (10 g/L) and 3.0 ml of zinc reagent solution were added. An additional 1.5 ml of cyclohexanone was added. Mix and place for 15 min with a 1 cm cuvette and measure the absorbance with a reagent blank as reference to a visible spectrophotometer at 620 nm. 1, phenol red ethanol solution (1 g / L): 2, sodium hydroxide (40 g / L): 3, hydrochloric acid (1 + 50): 4, ascorbic acid 5, buffer: weigh 42 g of granular hydroxide Sodium, dissolved in water, add 155 g of boric acid, add pure water to 500 ml after dissolution; the reagents used are of analytical grade, and the experimental water is pure water. 6, solution (10 g / L): 7, zinc standard use solution (10.0ppm): 8, zinc reagent solution: purple-brown crystalline powder. Soluble in ethanol and alkali, soluble in sodium hydroxide, red, insoluble in water. In the case of zinc, a blue compound is formed, which is a solution when diluted, and a dark blue precipitate when concentrated. 12. Microwave digestion - Determination of total nitrogen in water by ultraviolet spectrophotometry Take a certain amount of water in a Teflon sealed digestion tank, add water to 25 mL, and shake well. Take 0., 0.1, 0.3, 0.5, 0.7, 1.0, 3.0, 5.0, 7.0, 9.0, 11.0, 12.0, 13.0, 15.0 mL of nitrogen standard solution in a Teflon sealed digestion tank, add water to 25 mL, Shake well. 0.50 mL of H2O2 and 0.50 mL of 9 mol/L sulfuric acid solution were added in sequence, sealed and sealed in a microwave digestion furnace for 10 min in 10 minutes, and cooled to room temperature. Into a 10 mm quartz cuvette, the absorbance was measured at 220 and 275 nm of the UV-Vis spectrophotometer, and the total nitrogen was measured by dual-wavelength ultraviolet spectrophotometry. When the nitrogen content is between 0.024 2 and 9.60 ppm, it is linear with the absorbance, and the blank test is performed by using deionized water instead of the sample. Hydrogen peroxide is used to digest organic matter in water, including nitrogenous organic matter, so its amount is an important controlling factor. It was found that the absorbance remained basically unchanged between 0.40 and 0.80 mL of hydrogen peroxide. Under acidic conditions, hydrogen peroxide had strong oxidizing properties; however, the acidity was too strong, which was not conducive to the conversion of NH4+ to NO3-. 1. Nitrogen standard use solution: 20 mg/L potassium nitrate standard; 2. Sulfuric acid solution (9 mol/L;) 3. Hydrogen peroxide solution (0.3 g/mL); 4. The water used in this experiment is no ammonia. 3. Fluorine-ashing distillation - Fluorine reagent colorimetric sample is fixed with fluorine by magnesium nitrate. After high-temperature ashing, under the acidic condition, the fluorine is separated by distillation, and the distilled fluorine is absorbed by the sodium hydroxide solution. The fluorine reagent and cerium nitrate act to form a blue ternary complex, which is quantitatively compared with the standard. The water used in the method is deionized water containing no fluorine, the reagent is analytically pure, and all the reagents are stored in a polyethylene plastic bottle. 1 Acetone: 500ml.2 hydrochloric acid (1+11): 10mL hydrochloric acid, diluted with water to 120mL.3 sodium acetate solution (250g / L): 4 acetic acid solution (1mol / L): take 3ml, diluted to 50mL.5 Sodium hydroxide solution (40g / L): 6 Alizarin ammonia carboxylate solution: Now available. Weigh 0.19 g of alizarin aminocarboxylate complexing agent, add a small amount of water and sodium hydroxide solution (40 g / L) to dissolve it, add 0.125g of sodium acetate, adjust the pH to 5.0 (red) with acetic acid solution, dilute with water to 500ml. 7 Magnesium nitrate solution (100 g / L): 8 bismuth nitrate solution: now. Weigh 0.11 g of cerium nitrate, dissolve it with a small amount of acetic acid solution, add water to about 225 ml, adjust the pH to 5.0 with sodium acetate solution (250 g/L), and dilute to 250 mL with water. 9 Buffer (pH 4.7): Weigh 30 g of anhydrous sodium acetate, dissolve in 400 mL of water, add 22 mL of glacial acetic acid, then slowly add glacial acetic acid to adjust the pH to 4.7, then dilute with water to 500 mL. Sodium hydroxide solution (100 g / L): 11 phenolphthalein-ethanol indicator solution (10 g / L): 12 sulfuric acid (2 + 1): 13, fluorine standard use solution (5.0ppm): weighed and mixed sample 5.00 g (in terms of fresh weight), in a 30m1 ,, add 5.0 m L of magnesium nitrate solution and 0.5 m L of sodium hydroxide solution (100 g / L), make it alkaline, mix and soak for 0.5 h, set on a water bath Evaporate dry, then low temperature carbonization, until no smoke at all, move to the muffle furnace, ash for 6h at 600 degrees, take out, let cool. Add 10m L of water to the sputum and add a few drops of sulphuric acid (2:1) to the sputum to prevent the solution from splashing and neutralizing until no bubbles are formed. The solution was transferred to a 500 mL retort, and the mash was washed several times with 20 mL of water and incorporated into a retort. 60 mL of sulfuric acid (2+1) was added to the distillation flask, and several fluorine-free small glass beads were added to the distillation apparatus, followed by heating and distillation. The distillate is absorbed in a 50 mL beaker containing 5 mL of water, 7 drops to 20 drops of sodium hydroxide solution (100 g/L) and 1 drop of phenolphthalein indicator. Stop the distillation when the temperature of the solution in the distillation flask rises to 190 °C. (The whole distillation time is about 15 min-20 min), remove the condensation tube, wash the condensation tube with water with a dropper for 3 times to 4 times, and wash the liquid into the beaker. The absorption liquid in the beaker was transferred to a 50 mL volumetric flask, and the beaker was washed twice or three times with a small amount of water and combined in a volumetric flask. Neutralization with hydrochloric acid (1+11) until red just disappeared. Dilute to the mark with water and mix. Pipette 0, 1.0, 3.0, 5.0, 7.0, 9.0 mL of fluorine standard solution (equivalent to 0, 1, 3, 5, 7, 9 ug of fluorine) in a 25 mL plugged colorimetric tube. Pipette 10.0 mL of each sample distillate into a 25 mL plugged colorimetric tube. Add 2.OmL alizarin aminocarboxylate complex solution, 3.0 mL buffer, 6.0 mL acetone, 2.0 m L lanthanum nitrate solution, add water to the mark, mix, place 20m in, 3cm cuvette (reference wavelength 580 nm) Adjust the zero point with a zero tube, measure the absorbance of each tube, and compare the standard curve. Key words: spectrophotometry; trace elements; aesthetic instrument ; UV-1800A Transparent Led Screen
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