Analysis of total phosphorus in ores

National standards for comprehensive analysis of phosphate rock and phosphate concentrate http://bbs.hcbbs.com/viewthread.php?tid=92906&highlight=%C1%D7%BF%F3%CA%AF

Methods for chemical analysis of silicate rocks – Determination of phosphorus pentoxide GB/T 14506.9-1993, available online for reference

I also have a question: does anyone know any methods for detecting phosphorus in ores with high vanadium content?

For high concentrations, the volumetric method is the best choice; the photometric method can be used for low concentrations. When the concentration is above 2%, the error associated with the photometric method becomes significant, so the volumetric method is preferred. Phosphorus ore with high vanadium content? Generally, the vanadium content in vanadium ores is only a little over 1%. Vanadium is present in very small amounts in phosphate ores; our laboratory often analyzes phosphate ores, and conventional methods are sufficient for that purpose.

I would like to ask you: our ore contains about 10% phosphorus, and the same is true for vanadium. Can phosphorus be determined using the ammonium vanadomolybdate method? ?

1 Determination of total phosphorus content — Quinoline phosphomolybdic acid gravimetric method 1.2 Method summary The sample is decomposed using aqua regia and perchloric acid; dilute hydrochloric acid is added to dissolve the soluble salts. In nitric acid solution, phosphate ions and quinoline form a yellow precipitate of quinoline phosphomolybdic acid, which is then dried at 180°C until a constant weight is reached. 　1.3 Reagents 1.3.1 Hydrochloric acid (specific gravity 1.19). 　1.3.2 Hydrochloric acid (1+5). 　1.3.3 Nitric acid (specific gravity 1.42). 　1.3.4 Nitric acid (1+1). 　1.3.5 aqua regia (hydrochloric acid: nitric acid = 3:1). 　1.3.6 Perchloric acid (72%). 　1.3.7 Quinomolybdenum citrate solution Solution (1): Dissolve 70 g of sodium molybdate in 150 mL of water ； 　　Solution (2): Dissolve 60 g of citric acid in a mixture of 85 mL of nitric acid and 150 mL of water ； 　　Solution (3): Under continuous stirring, solution (1) is slowly added to solution (2) ； 　　Solution (4): Take 5 mL of quinoline and dissolve it in a mixture of 35 mL of nitric acid and 100 mL of water. 　　While stirring continuously, solution (4) was slowly added to solution (3). After being left in the dark for 24 hours, 280 mL of propanol was added, and the mixture was diluted to 1 L with water, followed by mixing well. Store in a polyethylene bottle in a dark place. Filter over time. 　1.4 Operating Procedures 1.4.1 Preparation of the test solution Weigh 1 g of the sample (with accuracy to 0.0001 g) and place it in a 250 mL beaker. Add 20 mL of aqua regia (1.3.5), cover the beaker with a watch glass, and heat it slowly over low heat until the sample dissolves. Add 8 mL of perchloric acid, continue heating until white fumes appear for half an hour. Allow the mixture to cool slightly, then add 40 mL of hydrochloric acid (1.3.2). Heat gently to ensure that all soluble salts dissolve. After cooling, transfer the solution to a 250 mL or 500 mL volumetric flask, dilute it with water to the mark, mix well, and filter off any solids. 　1.4.2 Precipitation 　　Accurately transfer 25 mL of the filtrate obtained in 1.4.1, or an appropriate amount equivalent to about 30 mg of P2O5, into a 500 mL conical flask. Add 10 mL of nitric acid (1.3.4), dilute with water to 100 mL, mix well, heat to boiling, and then add 50 mL of the quinomolybdate citrate solution (1.3.7) while the mixture is still hot. Allow it to simmer for 1 minute without stirring, then cool to room temperature, rotating the conical flask 2–3 times during cooling. 　1.4.3 Filtration and washing The precipitate is filtered under vacuum using a No. 4 glass crucible that has been dried at 180°C until a constant weight is reached. First, filter the upper supernatant, then wash the precipitate twice by pouring, and finally transfer the precipitate to a crucible. Wash it with water 4–5 times, and use filter paper to absorb the moisture from the bottom of the crucible. 　1.4.4 Drying and weighing The crucible along with the precipitate is dried at 180°C for 1 hour, then taken out and placed in a desiccator to cool to room temperature. It is weighed until a constant weight is reached. 　1.4.5 Blank test A blank test is conducted simultaneously with the sample. 　1.5 Calculation of results The percentage content of total phosphorus (P2O5) is calculated using equation (1): Total phosphorus (P2O5%) = [(m1 – m2) × 0.03207/m] × 100………………………(1) Where: m1 —— the mass of the quinoline phosphomolybdic acid precipitate, in g ； m2──mass of the quinoline phosphomolybdate precipitate for the reagent blank, in g ； 0.03207──Coefficient for converting quinoline phosphomolybdate [(C9H7N)3H3PO4·12MoO3] to phosphorus pentoxide (P2O5) ； m──the mass of the sample in the taken test solution, in g. 　1.6 Accuracy The absolute difference between the results of parallel measurements shall not be greater than 0.20%. Note: To clean the crucible, first rinse the precipitate with water, then wash it with ammonia solution (1+1), and finally rinse it several times with hot distilled water before drying it for later use. 2 Determination of water-soluble phosphorus content──Quinoline phosphomolybdic acid gravimetric method 2.1 Scope of application Applicable to compound fertilizers, diammonium hydrogen phosphate, and triple superphosphate, etc. 　2.2 Method Summary The sample is rinsed with water at 20–25°C; the filtrate is acidified with nitric acid, and phosphorus is precipitated using a quinomolybdate-citrate solution. It is then dried at 180°C until a constant weight is reached. 　2.3 Reagents 2.3.1 Nitric acid (1+1). 　2.3.2 Quinomolybdenum citrate solution: The preparation method is the same as that described in 1.3.7 for the determination of total phosphorus content. 　2.4 Operating Procedures 2.4.1 Preparation of the test solution 2.4.1.1 Compound fertilizers, etc. Weigh 1 g of the sample (with accuracy to 0.0001 g) and place it in a funnel lined with 11 cm of medium-speed filter paper soaked in pulp. Below the funnel, use a 250 mL volumetric flask as a collection container. Wash the sample with water at 20–25°C; each time, ensure that the water and the sample are thoroughly mixed, and wait until all the water has been filtered out before proceeding with the next wash. Continue washing until the volume of the filtrate reaches about 200 mL. Then add 4 mL of nitric acid (2.3.1) to clarify the solution, and subsequently dilute it with water to the marked volume, mixing well. 　2.4.1.2 Diammonium hydrogen phosphate and triple superphosphate, etc.: Weigh 1 g of the sample (with accuracy to 0.0001 g) and place it on 11 cm of medium-speed filter paper coated with pulp. Use a 500 mL volumetric flask as a receiving container for the filtrate; wash the sample with water at 20–25°C. The subsequent steps are the same as those in 2.4.1.1. Continue washing until the volume of the filtrate reaches about 400 mL, then add 4 mL of nitric acid (2.3.1). Finally, dilute the mixture with water to the marked volume and mix well. 　2.4.2 Precipitation 　　Accurately transfer 25 mL of the aforementioned filtrate (2.4.1.1 or 2.4.1.2), or an appropriate amount equivalent to about 30 mg of P2O5, into a 500 mL conical flask. Add 10 mL of nitric acid (2.3.1), dilute with water to 100 mL, mix well, heat to a gentle boil for 10 minutes. While still hot, add 50 mL of the quinomolybdate citrate solution (2.3.2), allow it to simmer for 1 minute (without stirring), and then cool to room temperature. Rotate the conical flask 2–3 times during cooling. Filtering, washing, drying, weighing, and the blank test are carried out in accordance with sections 1.4.3 to 1.4.5 for the determination of total phosphorus content. 　2.5 Calculation of Results The percentage content of water-soluble phosphorus (P2O5) is calculated using equation (2): Water-soluble phosphorus (P2O5%) = [(m1 – m2) × 0.03207/m] × 100………………………………(2) Where: m1 —— the mass of the quinoline phosphomolybdate precipitate, in g ； m2──mass of the quinoline phosphomolybdate precipitate for the reagent blank, in g ； 0.03207──Coefficient for converting quinoline phosphomolybdate [(C9H7N)3·H3PO4 ·12MoO3] to phosphorus pentoxide (P2O5) ； m──the mass of the sample in the taken test solution, in g. 　2.6 Accuracy The absolute difference between the results of parallel measurements shall not be greater than 0.20%. 3 Determination of available phosphorus content──Quinoline phosphomolybdate gravimetric method. Available phosphorus refers to the total amount of phosphorus that is soluble in water and citrate or a 2% citric acid solution. 　3.1 Leaching method using neutral ammonium citrate solution 3.1.1 Scope of application Applicable to compound fertilizers, diammonium hydrogen phosphate, and triple superphosphate, etc. 　3.1.2 Method summary The sample is leached using a neutral ammonium citrate solution at 65°C, or it is first leached with water and then with a neutral ammonium citrate solution. After the leachate is hydrolyzed with nitric acid, phosphorus is precipitated using a quinomolybdate-citrate solution, followed by drying at 180°C until a constant weight is reached. 　3.1.3 Reagents 3.1.3.1 Ammonia water (specific gravity 0.9). 　3.1.3.2 Nitric acid (1+1). 　3.1.3.3 Triammonium citrate [(NH4)3C6H5O7], analytical grade. 　3.1.3.4 Neutral ammonium citrate solution: Dissolve 450 g of triammonium citrate in an appropriate amount of water, add ammonia solution slowly, and use a pH meter to adjust the pH of the solution to exactly 7. Then dilute it with water so that its specific gravity is 1.09 at 20°C. 3.1.3.5 Quinomolybdate citrate solution: The preparation method is the same as that described in 1.3.7 for the determination of total phosphorus. 　3.1.4 Operating Procedures 3.1.4.1 Preparation of the test solution a. Compound fertilizers, etc. – Single extraction Weigh 1 g of the sample (with accuracy to 0.0001 g), place it in a 250 mL volumetric flask, add 100 mL of neutral ammonium citrate solution preheated to 65°C, seal the flask tightly, shake the flask vigorously (or use a rotary shaker), and then place the flask in a water bath at 65°C for 1 hour. Shake the bottle once every 10 minutes, slightly opening the cap each time to release pressure from inside the bottle. After removal, cool it immediately, dilute it with water to the marked line, and mix well. Leave for more than 2 hours, then filter dry. 　　b. Diammonium hydrogen phosphate and triple superphosphate, etc. – leaching is carried out separately. Weigh 1 g of the sample (with accuracy to 0.0001 g), place it in a funnel lined with 11 cm of medium-speed filter paper soaked in pulp; use a 500 mL volumetric flask at the bottom of the funnel to collect the liquid. Wash the sample with water at 20–25°C. Each time it is washed, the water and the sample must be thoroughly mixed, and after all the water has been filtered out, a second wash is performed until the volume of the filtrate reaches about 400 mL. Add 4 mL of nitric acid (3.1.3.2), dilute with water to the mark, and mix well; this constitutes “Solution 1”. 　　Transfer the residue remaining on the filter paper along with the filter paper itself into another 500 mL volumetric flask. Add 100 mL of neutral ammonium citrate solution preheated to 65°C, seal the flask tightly, and shake it vigorously (or use a rotary shaker) to break the filter paper into pulp. Place the flask in a water bath at 65°C for 1 hour, shaking it once every 10 minutes while slightly opening the cap to release pressure inside the flask. After that, remove the flask, cool it immediately, dilute it with water to the mark, and mix well. Let it sit for more than 2 hours, then filter dry; this is “Test Solution 2”. 　3.1.4.2 Precipitation a. Accurately pipette 25 mL of the aforementioned solution (3.1.4.1a) or an appropriate amount (equivalent to about 30 mg of P2O5). 　　b. Accurately transfer 25 mL of \"Test Solution 1\" and 25 mL of \"Test Solution 2\" from the solution mentioned in (3.1.4.1b), or an appropriate amount equivalent to about 30 mg of P2O5, into a 500 mL conical flask. Add 20 mL of nitric acid (3.1.3.2), dilute with water to 100 mL, heat to boiling for 10 min. While still hot, add 50 mL of the quinomolybdic citrate solution (3.1.3.5), allow it to simmer for 1 min (without stirring), then cool to room temperature. Rotate the conical flask 2–3 times during cooling. Filtering, washing, drying, weighing, and the blank test are carried out in accordance with sections 1.4.3 to 1.4.5 for the determination of total phosphorus content. 3.1.5 Calculation of results The percentage content of available phosphorus (P2O5) is calculated using equation (3): Available phosphorus (P2O5%) = [(m1 – m2) × 0.03207 / m] × 100………………………(3) Where: m1 —— the mass of the quinoline phosphomolybdate precipitate, in g ； m2──mass of the quinoline phosphomolybdate precipitate for the reagent blank, in g ； 0.03207──Coefficient for converting quinoline phosphomolybdate [(C9H7N)3·H3PO4 ·12MoO3] to phosphorus pentoxide (P2O5) ； m──the mass of the sample in the taken test solution, in g. 　　The above separate extraction methods can also be applied to compound fertilizers. 　　It is also possible to separately determine the phosphorus content in the water-soluble phosphorus in \"Test Solution 1\" and the ammonium citrate solution in \"Test Solution 2\". Available phosphorus (P2O5%) = Water-soluble phosphorus (P2O5%) + Ammonium citrate-soluble phosphorus (P2O5%) 3.1.6 Accuracy The absolute difference between the results of duplicate measurements shall not be greater than 0.20%. 　3.2 2% citric acid solution leaching method 3.2.1 Scope of application Applicable to compound fertilizers (where a 2% citric acid solution is specified in the contract). 　3.2.2 Method Summary The sample is leached using a 2% citric acid solution; the leachate is hydrolyzed with nitric acid, and phosphorus is precipitated using a quinomolybdate-citrate solution. It is then dried at 180°C until a constant weight is reached. 　3.2.3 Reagents 3.2.3.1 Citric acid (C6H8O7·H2O). 　3.2.3.2 2% citric acid solution: Weigh 20 g of citric acid, dissolve it in an appropriate amount of water, dilute to 1 L, and mix well. 　3.2.3.3 Nitric acid (1+1). 　3.2.3.4 Quinomolybdate citrate solution: The preparation method is the same as that described in section 1.3.7 for the determination of total phosphorus content. 　3.2.4 Operating Procedures 3.2.4.1 Preparation of the test solution Weigh 1 g of the sample (with accuracy to 0.0001 g) and place it in a 250 mL volumetric flask. Add 100 mL of 2% citric acid solution at 20–25°C, seal the flask tightly, and shake it vigorously for 1 hour (or use a rotary shaker). Immediately dilute with water to the mark, mix well, and filter off any solids. 　3.2.4.2 Precipitation, filtration, washing, and blank tests shall be carried out in accordance with paragraphs 3.1.4.2a and 3.1.4.2b of the method for determining available phosphorus content. 　3.2.5 Calculation of results The percentage content of available phosphorus (P2O5) is calculated using formula (3) in section 3.1.5. 　3.2.6 Accuracy The absolute difference between the results of parallel measurements shall not be greater than 0.20%.

Water quality – Determination of total phosphorus – Ammonium molybdate spectrophotometric method GB 11893-89 1 Subject matter and scope: This standard specifies a method for determining total phosphorus in unfiltered water samples by digesting them using potassium persulfate (or nitric acid–perchloric acid) as an oxidizing agent, followed by ammonium molybdate spectrophotometry. Total phosphorus includes dissolved, particulate, organic, and inorganic phosphorus. This standard applies to surface water, sewage, and industrial wastewater. Take 25 mL of the sample; the minimum detectable concentration according to this standard is 0.01 mg/L, while the upper limit for determination is 0.6 mg/L. Under acidic conditions, arsenic, chromium, and sulfur interfere with the determination. 2 Principle: Under neutral conditions, the sample is digested using potassium persulfate (or nitric acid–perchloric acid) to oxidize all the phosphorus present into orthophosphates. In an acidic medium, orthophosphates react with ammonium molybdate to form phosphomolybdic heteropolyacids in the presence of antimony salts, which are then immediately reduced by ascorbic acid to produce a blue complex. 3 Reagents Unless otherwise specified in this standard, analytical reagents that meet **standards or professional standards, as well as distilled water or water of equivalent purity, shall be used. 3.1 Sulfuric acid (H2SO4), with a density of 1.84 g/mL. 3.2 Nitric acid (HNO3), with a density of 1.4 g/mL. 3.3 Perchloric acid (HClO4), reagent grade, with a density of 1.68 g/mL. 5.4 Sulfuric acid (H2SO4), 1+1. 3.5 Sulfuric acid, approximately c(1/2H2SO4) = 1 mol/L: Add 27 mL of sulfuric acid (3.1) to 973 mL of water. 3.6 Sodium hydroxide (NaOH), 1 mol/L solution: Dissolve 40 g of sodium hydroxide in water and dilute to 1000 mL. 3.7 Sodium hydroxide (NaOH), 6mol/L solution ； Dissolve 240 g of sodium hydroxide in water and dilute to 1000 mL. 3.8 Potassium persulfate, 50 g/L solution: Dissolve 5 g of potassium persulfate (K2S2O8) in water and dilute to 100 mL. 3.9 Ascorbic acid, 100 g/L solution: Dissolve 10 g of ascorbic acid (C6H8O6) in water and dilute to 100 mL. This solution is stored in a brown reagent bottle and can remain stable at low temperatures for several weeks. It can be used for a long time if it does not change color. 3.10 Molybdate solution: Dissolve 13 g of ammonium molybdate in 100 mL of water. Dissolve 0.35 g of potassium antimony tartrate in 100 mL of water. Under continuous stirring, the ammonium molybdate solution was slowly added to 300 mL of sulfuric acid (3.4), and the potassium antimony tartrate solution was added and mixed thoroughly. This solution is stored in a brown reagent bottle and can be kept at low temperature for two months. 3.11 Turbidity-chromaticity compensation solution: Mix two volumes of sulfuric acid (3.4) with one volume of ascorbic acid solution (3.9). Prepare on the day of use. 3.12 Phosphorus standard stock solution: Weigh 0.2197±0.001 g of potassium dihydrogen phosphate (KH2PO4), dry it at 110°C for 2 hours, and allow it to cool in a desiccator. Dissolve it in water and transfer the solution to a 1000 mL volumetric flask; add about 800 mL of water, 5 mL of sulfuric acid (3.4), dilute to the mark with water, and mix thoroughly. 1.00 mL of this standard solution contains 50.0 μg of phosphorus. This solution can be stored in a glass bottle for at least six months. 3.13 Phosphorus standard working solution: Transfer 10.0 mL of the phosphorus standard solution (3.12) to a 250 mL volumetric flask, dilute with water to the mark, and mix thoroughly. 1.00 mL of this standard solution contains 2.0 μg of phosphorus. Prepare on the day of use. 3.14 Phenolphthalein, 10 g/L solution: 0.5 g of phenolphthalein is dissolved in 50 mL of 95% ethanol. 4 Instruments: Common laboratory equipment and the following instruments. 4.1 Medical portable steam sterilizer or ordinary pressure cooker (1.1–1.4 kg/cm2). 4.2 50mL stoppered (ground glass) graduated cylinder. 4.3 Spectrophotometer. Note: All glassware should be soaked in dilute hydrochloric acid or dilute nitric acid. 5 Sampling and Samples 5.1 After collecting a 500 mL water sample, 1 mL of sulfuric acid (3.1) is added to adjust the pH of the sample to 1 or lower, or no reagents are added and the sample is stored at low temperature. Note: For water samples with low phosphorus content, do not use plastic bottles for sampling, as phosphates tend to adhere to the walls of plastic bottles. 5.2 Preparation of the sample: Take 25 mL of the sample (5.1) and place it in a stoppered graduated cylinder (4.2). It should be shaken carefully at the time of sampling to obtain a sample that is representative of both the dissolved and suspended portions. If the phosphorus concentration in the sample is high, the sample volume can be reduced. 6 Analysis Steps 6.1 Blank Sample Conduct a blank test in accordance with the provisions of (6.2), using water in place of the sample, and adding the same volume of reagent as used during the determination. 6.2 Determination 6.2.1 Digestion 6.2.1.1 Potassium persulfate digestion: Add 4 mL of potassium persulfate (3.8) to the sample in (5.2). Secure the stopper of the graduated cylinder, then tie the glass stopper in place using a small piece of cloth and string (or use another method for fixation). Place it in a large beaker inside a high-pressure steam sterilizer (4.1) and heat it. Once the pressure reaches 1.1 kg/cm2 and the temperature reaches 120°C, maintain this condition for 30 minutes before stopping the heating. Once the pressure gauge reading drops to zero, remove it and let it cool down. Then dilute with water to the mark. Note: If the water sample is to be stored with sulfuric acid. When digesting with potassium persulfate, the sample must first be adjusted to neutrality. 6.2.1.2 Nitric acid-perchloric acid digestion: Take 25 mL of the sample (5.1) into a conical flask, add a few glass beads, add 2 mL of nitric acid (3.2), and heat it on an electric hot plate until the volume is reduced to 10 mL. After cooling, add 5 mL of nitric acid (3.2), then heat to concentrate to 10 mL and allow to cool. Add 3 mL of perchloric acid (3.3), heat until white fumes appear from the perchloric acid; at this point, a small funnel can be placed on the conical flask or the temperature of the electric heating plate can be adjusted to ensure that the digestion solution remains in reflux on the inner walls of the conical flask, until 3–4 mL remain, after which it should be cooled. Add 10 mL of water and 1 drop of phenolphthalein indicator (3.14). Add sodium hydroxide solution (3.6 or 3.7) drop by drop until a slight pink color appears, then add sulfuric acid solution (3.5) drop by drop until the pink color disappears completely, and mix thoroughly. Transfer to a stoppered graduated cylinder (4.2) and dilute with water to the mark. Note: ① Digestion with nitric acid and perchloric acid must be carried out in a fume hood. A mixture of perchloric acid and organic substances can be dangerous when heated; therefore, the sample must first be digested with nitric acid, and then nitric-perchloric acid is added for further digestion. ②Under no circumstances should the solution used for dissolution be evaporated to dryness. ③If there is residue after digestion, filter it using filter paper into a stoppered graduated cylinder; thoroughly wash the conical flask and the filter paper as well, and transfer everything to the stoppered graduated cylinder. ④When the organic matter in water cannot be completely destroyed by oxidation with potassium persulfate, this method can be used for digestion. 6.2.2 Color development: Add 1 mL of ascorbic acid solution (3.9) to each digestion sample and mix well; after 30 seconds, add 2 mL of molybdate solution (3.10) and mix thoroughly. Note: ① If the sample contains turbidity or color, a blank sample must be prepared (diluted with water to the mark after digestion), and then 3 mL of turbidity-color compensation solution (3.11) should be added to the sample; however, no ascorbic acid solution or molybdate solution should be added. Then, the absorbance of the blank sample is subtracted from the absorbance of the sample. ②Arsenic levels above 2 mg/L interfere with the determination; it should be removed using sodium thiosulfate. Sulfides above 2 mg/L interfere with the determination; nitrogen gas is used to remove them. Chromium levels above 50 mg/L interfere with the determination; it should be removed using sodium sulfite. 6.2.3 Spectrophotometric measurement: After being left at room temperature for 15 minutes, the absorbance is determined using a cuvette with a path length of 30 mm at a wavelength of 700 nm, with water as the reference. After subtracting the absorbance of the blank test, the phosphorus content is determined from the calibration curve (6.2.4). Note: If the room temperature is below 13°C at the time of color development, the color can be developed in water at 20–30°C for 15 minutes. 6.2.4 Drawing of the working curve: Seven stoppered graduated cylinders (4.2) were used to add 0.0, 0.50, 1.00, 3.00, 5.00, 10.0, and 15.0 mL of phosphate standard solution (3.14) respectively. Add water to 25 mL. Then proceed according to the measurement procedure (6.2). Absorbance is measured using water as a reference. After deducting the absorbance of the blank test, a calibration curve is plotted against the corresponding phosphorus content. 7 Representation of results The total phosphorus content is expressed in C (mg/L), calculated using the following formula: Where: m – the phosphorus content measured in the sample, in mg ； V — Volume of the sample used for determination, in mL. 8 Precision and Accuracy 8.1 Testing of a uniform sample containing 2.06 mg/L of phosphorus in thirteen laboratories (using digestion according to 6.2.1.1) 8.1.1 Repeatability The relative standard deviation within the laboratory was 0.75%. 8.1.2 Reproducibility: The inter-laboratory relative standard deviation is 1.5%. 8.1.3 Accuracy: The relative error is +1.9%. 8.2 Six laboratories determined the phosphorus content of a standardized sample at 2.06 mg/L using digestion according to 6.2.1.2. 8.2.1 Repeatability: The relative standard deviation in the laboratory is 1.4%. 8.2.2 Reproducibility: The inter-laboratory relative standard deviation is 1.4%. 8.2.3 Accuracy: The relative error is 1.9%. The main components of the quality control sample are alanine (NH2CH2COOH) and sodium glycerophosphate (). Additional note: This standard was proposed by the Standards Department of the **Environmental Protection Bureau**. This standard was drafted by the Beijing Environmental Monitoring Center and the Shanghai Environmental Monitoring Center. The main drafters of this standard are Yuan Yulu and Yao Yuan. This standard is entrusted to the China National Environmental Monitoring Center for interpretation.

If you want to use spectrophotometry for a 10% concentration, how much dilution is required? For phosphate ores with concentrations in this range, it’s best to use the quinoline phosphomolybdic acid titration method. The gravimetric method mentioned above is also a standard method, but it’s complicated and prone to large errors; the titration method is simpler. Generally, the gravimetric method is used for substances that are insoluble in acids.

We used to produce fertilizers with a phosphorus content of 7-8%, and for that we relied on the spectrophotometry method. We no longer work in this field, but I’m just providing this as a reference