GB/T 223.87-2018Iron,steel and alloy—Determination of calcium and magnesium—Inductively coupled plasma mass spectrometric method (English PDF)

4.5 Calcium standard stock solution, 1,000 µg/mL

Weigh-take 2.4972 g of calcium carbonate (mass fraction >= 99.99%) that is already dried at 110 °C for 1 h and cooled down to room temperature in a dryer. Place it in 400 mL beaker; add 100 mL of hydrochloric acid (1+1) to dissolve it. After cooling it down, transfer it into 1,000 mL volumetric flask. Use water to dilute to the constant volume; thoroughly mix it.

1 mL of this solution contains 1,000 µg of calcium.

4.6 Magnesium standard stock solution, 1,000 µg/mL

Weigh-take 1.6582 g of magnesium oxide (mass fraction >= 99.99%) that is already burnt at 850 °C for 30 min and cooled down to room temperature in a dryer. Place it in 400 mL beaker; add 100 mL of hydrochloric acid (1+1). After heating it up and dissolving it, cool it down to room temperature; transfer it into 1,000 mL volumetric flask.

Use water to dilute to the constant volume; thoroughly mix it.

1 mL of this solution contains 1,000 µg of magnesium.

4.7 Mixed standard solution of calcium and magnesium

4.7.1 Mixed standard solution of calcium and magnesium, 100 µg/mL

7.2 Blank Test

Conduct blank test in accordance with the sample.

7.3 Determination

7.3.1 Preparation of sample solution

In terms of carbon steel and low-alloy steel sample. place the sample (7.1) in 100 mL quartz beaker. Add 10 mL of water and 5 mL of nitric acid (4.2) [add 0.5 mL of hydrofluoric acid (4.3) to high-silicon sample], heat it up till it boils. After eliminating nitrogen oxide, take it down; cool it down, then, transfer it into 100 mL plastic volumetric flask; add 1.0 mL of internal standard solution of scandium (4.8.3). Use water to dilute to the constant volume, then, thoroughly mix it for later determination.

In terms of high-carbon steel and alloy steel sample. place the sample (7.1) in 100 mL quartz beaker. Add 3 mL of hydrochloric acid (4.1) and 1 mL of HNO3 (4.2); use heating plate to heat it up till it boils. Add 2 mL of perchloric acid (4.4), heat it up till it begins to fume and stable perchloric acid fume reflux is formed around the bottle mouth or on the wall. Continue to heat it up, till white perchloric acid fume vanishes. Cool it down, then, add 3 mL of hydrochloric acid (4.1) and 1 mL of HNO3 (4.2); conduct low-temperature heating till salt is dissolved. If there are hydrolysable elements in alloy steel, add 0.5 mL of hydrofluoric acid (4.3) for complexation. Cool it down, then, transfer to 100 mL plastic volumetric flask; add 1.0 mL of internal standard solution of scandium (4.8.3). Use water to dilute to the constant volume, then, thoroughly mix it for later determination.

NOTE: microwave digestion system can also be adopted for the preparation of sample solution, but the laboratory shall determine an optimized experimental plan in accordance with conditional experiments.

7.3.2 Preparation of calibration solution

Respectively transfer 0, 0.20 mL, 0.50 mL, 1.00 mL, 2.00 mL and 5.00 mL of mixed standard solution of calcium and magnesium (4.7.3), and 1.00 mL, 2.00 mL and 5.00 mL of mixed standard solution of calcium and magnesium (4.7.2) in 9 plastic volumetric flasks (100 mL). Respectively add 10 mL of Fe matrix solution (4.11) and 1.00 mL of scandium internal standard solution (4.8.3). Add acid that is consistent with sample dissolution; use water to dilute to the constant volume, then, thoroughly mix it. Solution that does not contain the mixed standard solution of calcium and magnesium is calibration blank solution.

7.3.3 Preparation of instrument

Before analysis, ignite plasma; pre-heat it for 30 min ~ 60 min in accordance with the requirements in the instruction for use to stabilize the instrument. During this process, pump in water or mass spectrometer cleaning solution (4.10) to rinse nebulizer and […]