GB/T 13885-2017Determination of the contents of calcium, copper, iron, magnesium, manganese, potassium, sodium and zinc in feeds -- Method using atomic absorption spectrometry (English PDF)

4.11 Lanthanum/cesium blank solution: Take 5mL of lanthanum nitrate solution, 5mL

of cesium chloride solution and 5mL of hydrochloric acid solution (4.3) into a 100mL volumetric flask. Use water to set the volume constant.

5.2 Crucible: platinum, quartz or porcelain; free of potassium and sodium; the inner

layer is smooth and not corroded; the upper diameter is 4cm~6cm; the lower diameter is 2cm~2.5cm; the height is about 5cm; boil with hydrochloric acid solution (4.3) before use.

5.3 Rigid glassware. Boil with hydrochloric acid solution (4.3) before use. Rinse off

with water.

5.4 Heating plate.

5.5 High temperature resistance furnace: the temperature can be controlled at

550°C±15°C.

5.6 Atomic absorption spectrophotometer: the wavelength range complies with the

provisions of 8.6.1 and 8.7.1. It is with air-acetylene flame and background correction.

5.7 Ca, Cu, Fe, K, Mg, Mn, Na, Zn hollow cathode lamps or electrodeless discharge lamps.

5.8 Quantitative filter paper.

8.1 Check for organic matter

Take some of the test material with a flat spoon. Heat it over a flame. If the test material melts without smoke, there is no organic matter present. If the color of the test material changes and does not melt, the test material contains organic matter.

8.2 Test material

Weigh 1g~5g of test material according to the estimated content, accurate to 1mg. Put it in the crucible. For test material containing organic matter, start from 8.3. For test material not containing organic matter, start directly from 8.4.

solution (4.4) and the absorbance of the standard solution. Subtract the absorbance of the hydrochloric acid solution (4.4) from the absorbance of the standard solution. The calibration curve is plotted against the contents of Cu, Fe, Mn and Zn with the corrected absorbance values.

NOTE 1: Most atomic absorption spectrophotometers have the function of automatically drawing curves.

NOTE 2: Non-linearly drawn curves are not required. If the curve presents a high-order function shape, the method of drawing the curve nonlinearly can improve the accuracy of the measured data.

8.6.3 Determination of test material solution

Under the same conditions, measure the absorbance of the test material solution (8.4) and blank solution (8.5). The absorbance of the test material solution minus the absorbance of the blank solution. Calculate the concentration of elements in the test material solution from the standard curve. Calculate the content according to Chapter

9. If necessary, dilute the sample solution and blank solution with hydrochloric acid solution (4.4). Make its absorbance within the linear range of the standard curve.

NOTE 1: Most atomic absorption spectrophotometers have the function of automatically calculating the concentration of elements in the test material solution.

NOTE 2: Background correction is not required. If there is a background value, the use of background correction can improve the accuracy of the measured data.

8.7 Determination of calcium, magnesium, potassium, sodium

8.7.1 Measurement conditions

Adjust the instrument test conditions of the atomic absorption spectrophotometer. Make the instrument in the best analysis state in the air-acetylene flame measurement mode.

The measuring wavelengths of Ca, K, Mg and Na are as follows:

Ca: 422.6nm;

K: 766.5nm;

Mg: 285.2nm;

Na: 589.6nm.

8.7.2 Standard curve

Use water to dilute to the standard solution (4.10). For every 100mL of standard solution, add 5mL of lanthanum nitrate solution, 5mL of cesium chloride solution and

5mL of hydrochloric acid solution (4.3). Prepare a set of suitable standard working solutions.

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