GB/T 6730.55-2019Iron ores - Determination of tin content - Flame atomic absorption spectrometric method (English PDF)

7.2 of edition 2004);

-- it changes the precision regression equation (see 8.2.1; 8.2.1 of edition 2004);

-- it changes the trueness check equation (see 8.2.4; 8.2.4 of edition 2004).

This Part was redrafted by modifying and adopting ISO 11534:2006, Iron ores -

Determination of tin - Flame atomic absorption spectrometric method.

The technical differences between this Part and ISO 11534:2006, and the reasons, are

as follows:

-- with respect to normative references, some adjustments are made in this Part

resulting in some technical differences, in order to adapt to the technical conditions

in China. The adjustments are intensively reflected in "Normative references" of

Clause 2. This Part:

 adds the references including GB/T 6379.1, GB/T 6379.2, GB/T 7728, GB/T

8170, GB/T 12807, GB/T 12808 (see Clause 5, 8.2.1, 8.2.5);

 deletes ISO 648;

 uses GB/T 6682 modifying and adopting the international standard to

replace ISO 3696 (see Clause 4);

 uses GB/T 6730.1 modifying and adopting the international standard to

replace ISO 7764 (see 6.2);

 uses GB/T 10322.1 equivalently adopting the international standard to

replace ISO 3082 (see 6.1);

 uses GB/T 12806 non-equivalently adopting the international standard to

replace 1042 (see Clause 5);

-- it adjusts the sequence and numbers of the clauses in the "Reagents"

Iron ores - Determination of tin content - Flame

atomic absorption spectrometric method

Warning - The operators using this Part shall have practical experiences

in the work in a normal laboratory. This Part does not purport to address

all of the safety problems associated with its use. It is the responsibility

of the user of this Part to establish appropriate health and safety practices

and determine the applicability of regulatory limitations prior to use.

4.5 Hydrofluoric acid, rho about 1.13 g/mL.

4.6 Hydrochloric acid, 1+1.

4.7 Hydrochloric acid, 2+3.

4.8 Sulfuric acid, 1+1.

4.9 Ascorbic acid solution, 200 g/l, freshly prepared just prior to use.

4.10 Potassium iodide/ascorbic acid solution: dissolve 90 g of potassium iodide in

water, add 30 g of ascorbic acid and 30 mL of hydrochloric acid (4.3), and dilute with

water to 200 mL. This solution shall be freshly prepared just prior to use.

4.11 Tri-n-octyl phosphine oxide (TOPO)/4-methyl-2 pentanone (MIBK) solution:

dissolve 1 g of TOPO in 100 mL of MIBK.

4.12 Tin standard solution, 200 µg/mL.

Dissolve 0.1 000 g of tin metal (purity > 99.5%) in a platinum crucible (with cover) with

4.13 Tin standard solution, 20 µg/mL.

Transfer 10 mL of tin standard solution (4.12) to a 100 mL volumetric flask, dilute to

volume with hydrochloric acid (4.6) and mix.

5.1 Platinum crucible, of capacity 25 ml to 30 ml.

5.2 Platinum rod.

5.3 Separating funnel, 200 mL.

5.4 High temperature furnace, suitable for heating at 1 000°C to 1 020°C.

5.5 Atomic absorption spectrometer, equipped with a dinitrogen oxide/acetylene burner.

Carry out the analysis at least in duplicate in accordance with Annex A, independently,

on one predried test sample.

NOTE: The expression "independently" means that the second and any subsequent result is

not affected by the previous result(s). For the particular analytical method, this condition implies

that the repetition of the procedure is carried out either by the same operator at a different time

or by a different operator including, in either case, appropriate recalibration.

7.2 Test portion

Taking several increments, weigh, to the nearest 0.000 2 g, approximately 1.00 g of

the predried test sample obtained in accordance with 6.2. The test portion should be

taken and weighed quickly to avoid re-absorption of moisture.

7.3 Blank test and check test

7.3.1 Blank test

When the analysis is carried out, carry out the blank test; all reagents are from the

same reagent bottle.

7.3.2 Check test

When the analysis is carried out, carry out the check test on the same type of reference

samples.

7.4 Determination

7.4.1 Decomposition of the test portion

Transfer the test portion (7.2) to a crucible (5.1), moisten with a few drops of water,

add 2 ml of sulfuric acid (4.8) and 6 ml of hydrofluoric acid (4.5), mix well using a

platinum rod (5.2) and wash the rod with water. Using a low-temperature electric

furnace, heat the crucible gently at first, then to white fumes, and continue heating until

no fumes are observed. Place the crucible in a high temperature furnace (5.4) at 1

000°C to 1 020°C for 30 min. Remove the platinum crucible and cool. Add 4.8 g the

mixed solvent (4.1) of sodium carbonate and sodium tetraborate, put on the platinum

cover, place int the high temperature furnace for fusion for 30 min at 1 000°C ~ 1 020°C;

remove to cool. Place the platinum crucible and cover in a 200 ml beaker. Add 50 ml

of hydrochloric acid (4.7), cover the beaker with a watch glass and heat in a water bath

at about 90°C until dissolution of the melt is complete. Wash out the crucible and cover

and cool. In order to avoid the volatilization of tin, they shall be placed in a water bath

at about 90°C.

7.4.2 Treatment of the test solution

Transfer the solution (7.4.1) to a 200 ml separating funnel having a mark indicating 100

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