GB/T 6730.81-2020Iron ores—Determination of multiple trace elements—Inductively coupled plasma mass spectrometric method (English PDF)

6.1 Laboratory samples

Sampling and preparation shall be carried out in accordance with GB/T 10322.1.

Generally, the sample particle size is less than 100 µm. If the content of combined water or easy oxides in the sample is high, the particle size shall be less than 160 µm.

For provisions regarding high combined water and easy oxides content, see GB/T 6730.1.

6.2 Pre-dried samples

Thoroughly mix the laboratory samples and take samples using the sample splitting method. According to the provisions of GB/T 6730.1, dry the sample at a temperature of 105 °C ± 2 °C, and cool it to room temperature in a desiccator for later use.

7.1 Number of determinations

According to Annex C, the same pre-dried sample shall be determined independently at least twice, and the average value of the results shall be taken.

NOTE: "Independent" means that the results of the second and any subsequent determination are not affected by the results of the previous determinations. In this analytical method, this condition means that the same determined object is independently and repeatedly determined in a short period of time by the same operator using the same equipment and the same test method in the same laboratory, including using appropriate recalibration.

7.2 Sample mass

Weigh 0.10 g of pre-dried sample (see 6.2), accurate to 0.0001 g. The sample weighing operation shall be carried out as quickly as possible to prevent the sample from absorbing moisture again.

7.3 Blank test and verification test

7.3.1 Blank test

Except for not adding the sample to be determined, the blank test shall be carried out in accordance with 7.4. All reagents shall be taken from the same reagent bottle. When analyzing multiple samples, it can use a blank value.

7.3.2 Verification test

Along with the sample analysis, carry out the verification test for reference materials of the same type.

7.4 Digestion of sample

ADD 7 mL of hydrochloric acid (see 4.1), 1 mL of hydrofluoric acid (see 4.2), and 2.5 mL of nitric acid (see 4.3) to the sample, SHAKE well, TIGHTEN the sealed digestion tank, and PUT it into the microwave digestion instrument. Refer to the microwave digestion working conditions in Annex B for microwave digestion. TAKE it out, COOL to room temperature, OPEN the digestion tank, TRANSFER the digested solution directly to a 100 mL plastic volumetric flask, RINSE the digestion tank and lid with water 3 ~ 5 times, COMBINE the washing liquid into the solution, DILUTE with nitric acid (see 4.4) to the mark, MIX well, and LET STAND for later test.

7.5 Quantitative determination

7.5.1 Plotting of calibration curve

Inter-laboratory precision is used to evaluate the consistency between the final results reported by two laboratories. After the two laboratories report the results according to the same steps specified in 8.2.2, calculate according to formula (2): where: µ12 - the average value of the final results; µ1 - the final result reported by Laboratory 1; µ2 - the final result reported by Laboratory 2.

If |µ1 - µ2| <= R, the final results of the two laboratories are consistent.

8.2.4 Correctness check

The correctness check uses a certified reference material (CRM) or a reference material (RM) for verification. The final laboratory result is compared with the standard value Ac of CRM or RM. There will be two possibilities.

a) |µc - Ac| <= C, in this case, there is no significant difference between the determined value and the standard value.

b) |µc - Ac| > C, in this case, there is a significant difference between the determined value and the standard value. where: µc - the determined value of CRM or RM; Ac - the standard value of CRM or RM;

C - the value depends on the type of CRM / RM used.

The C value of the certified reference material (CRM) or reference material (RM) determined by multiple laboratories is calculated according to formula (3): where:

R - the inter-laboratory reproducibility limit; r - the in-laboratory repeatability limit; […]