Phosphorus Phosphorus

I'm a novice in this area. As long as it's relevant, thank you very much.

A lot of what materials? It’s difficult to start if you don’t know the properties of the material.

1. Principle: Organic matter in food is oxidized and decomposed by acid, so that phosphorus combines with ammonium molybdate under acidic conditions to form ammonium phosphomolybdate. This compound is reduced to a blue compound - molybdenum blue by hydroquinone and sodium sulfite. Use a spectrophotometer to measure the absorbance value of molybdenum blue at a wavelength of 660 nm to determine the phosphorus content. The reaction formula is: H3PO4+12(NH4)3MoO4+21HNO3→(NH4)3PO4·12MoO3+21NH4NO3+12H2O 2. Scope of application is based on the People’s Republic of China * * standard: GB12393-90, this method is suitable for the determination of phosphorus content in all foods and health products. 3. Instrument 722 visible spectrophotometer 4. Reagents (1) Nitric acid (GR), perchloric acid (GR) sulfuric acid ( A.R ) (2) Mixed acid digestion liquid: Nitric acid + perchloric acid mixed 4+1 (3) 15% (V/V) sulfuric acid solution: Slowly add 15ml of sulfuric acid to 80ml of water and adjust the volume to 100ml. (4) 5% (W/V) ammonium molybdate solution: Take 5g of ammonium molybdate and dilute it to 100ml with 15% sulfuric acid solution. (5) Hydroquinone solution: Take 0.5g hydroquinone in 100ml water, dissolve it and add a drop of concentrated sulfuric acid. (6) 20% (W/V) sodium sulfite solution (note: This solution needs to be temporarily prepared before each experiment): Weigh a certain amount of sodium sulfite and dissolve it in distilled water. (7) Standard quality control materials: Pork liver powder ( * * Provided by the Reference Materials Research Center), quality control materials need to be stored dry at room temperature. (8) * * Provided by the Reference Materials Center: Phosphorus standard stock solution, concentration is 1000μg/mL (9) Preparation of standard intermediate solution: Take 1 ml of phosphorus standard stock solution, then transfer it to a 100 ml volumetric flask, and adjust the volume to 100 ml with deionized water. The concentration is 10 mg/L. 5. Operation step 5.1 Sample digestion: Experimental operations must be conducted in an environment free of elemental pollution. Accurately weigh dry samples (about 0.3-0.7g), wet samples (about 1.0g), beverages and other liquid samples (about 1.0-2.0g), then put them into a 50ml digestive tube, add 15ml of mixed acid (add more acid for oil samples or foods with high sugar content), and leave overnight. The next day, put the digestive tube into the digestion furnace. At the beginning of digestion, the temperature can be lowered (about 130°C), and then the temperature can be gradually raised (finally to about 240°C) for digestion until the white smoke liquid in the sample turns colorless or yellow-green. If the sample is not completely digested, add a few milliliters of mixed acid until digestion is complete. After digestion, wait for it to cool, add 5 ml of deionized water, and continue heating until about 2 ml of liquid remains in the digestive tube. Remove, let cool, and then transfer to a 10 ml test tube. Rinse the digestive tube 2-3 times with deionized water, and finally adjust the volume to 10 ml. When samples are digested, sample blank digestion should be done at the same time. 5.2 Phosphorus standard curve: Pipette 1.0ml, 3.0ml, and 5.0ml of the standard stock solution into a 20ml graduated test tube respectively, then add 2ml ammonium molybdate solution, 1ml sodium sulfite solution, and 1ml hydroquinone solution in sequence, add distilled water to adjust the volume to 20ml, mix, and let stand for 30 minutes. Measure the absorbance at a wavelength of 660nm. Calculate the regression coefficient from this, and use the regression equation to calculate or draw a calibration curve. 5.3 Determination: Take 2 ml each of the sample and blank solution into a 20 ml test tube, then add 2 ml ammonium molybdate solution, 1 ml sodium sulfite solution, and 1 ml hydroquinone solution in sequence, add distilled water to adjust the volume to 20 ml, mix, and let stand for 30 minutes. Measure the absorbance at a wavelength of 660 nm, and calculate the phosphorus content in the unknown solution based on the measured absorbance on the standard curve. 6. Calculate X (mg/100g) = (C∕m ) × (V1∕V2 ) × 100 where: X----Phosphorus content in the sample, mg/100g C----Calculate the phosphorus content in the sample measurement solution from the standard curve and regression equation, mg m---weigh the sample amount g V1---the total volume of the digestion solution, ml V2-the volume of the digestion solution for determination, ml The minimum detection limit of this element is 2 μg 7. Notes (1) It is best to prepare the sodium sulfite solution temporarily before each experiment, otherwise the molybdenum blue solution may become turbid. (2) Secondly, after setting the volume, do not let it stand for too long, otherwise the color of the solution will deepen and the result will be inaccurate. This is for measuring food. I don’t know if it will be useful to you.

I'm confused. Maybe my form is not clear! I re-edited it