GB/T 20385.1-2021Textiles - Determination of organotin compounds - Part 1: Derivatisation method using GC-MS (English PDF)

5.1 Water, which complies with Grade-3 water specified in GB/T 6682.

5.2 Ethanol, chromatographically pure, CAS No.: 64-17-5.

5.3 Glacial acetic acid, CAS No.: 64-19-7.

5.4 Sodium tetraethyl-borate, CAS No.: 15523-24-7.

5.5 Tetrahydrofuran, CAS No.: 109-99-9.

5.6 n-heptyltin trichloride, CAS No.: 59344-47-7 (internal standard substance).

5.7 Di-n-heptyltin dichloride, CAS No: 74340-12-8 (internal standard substance).

5.8 Tri-n-pentyltin chloride, CAS No: 3342-67-4 (internal standard substance).

5.9 Tetra-n-propyltin, CAS No.: 2176-98-9 (internal standard substance).

NOTE: if the recovery rate of the internal standard substances (5.6, 5.7, 5.8 and 5.9) is relatively low, other internal standard substances (for example, deuterated compounds) may be selected (see also 9.1).

5.10 N-hexane, CAS No.: 110-54-3.

5.11 Inert gas, for example, nitrogen or argon, with a purity of 99.9%.

5.12 Tropolone, CAS No.: 533-75-5.

5.13 Methanol, CAS No.: 67-56-1.

5.14 Anhydrous sodium acetate, CAS No.: 127-09-3.

5.15 Organotin compounds, see Table 1.

6.1 Gas chromatograph - mass spectrometer (GC-MS).

6.2 Analytical balance, with a division value of 0.1 mg.

6.3 Glass reaction flask with a screw stopper, 50 mL.

6.4 Micropipette, 10 L ~ 500 L, disposable tip.

6.5 Pipette, with a measuring range of 1 mL ~ 10 mL.

6.6 pH meter, equipped with a glass composite electrode, with a measuring range of 0 ~ 14 and

the measurement accuracy accurate to 0.1.

6.7 Ultrasonic generator, with a working frequency of (40  5) kHz and the temperature

controllable.

6.8 Centrifuge.

6.9 Horizontal mechanical vibrator.

NOTE: the minimum frequency of the horizontal vibrator is 5 s1, and the amplitude is 2 cm ~ 5 cm.

6.10 Volumetric flask, with a volume of 10 mL ~ 500 mL.

NOTE: before use, all glassware shall be soaked in nitric acid (volume fraction: 5%) for 24 h, and rinsed with water.

8.1 General

SAFETY WARNING: since sodium tetraethyl-borate is air-sensitive and will spontaneously ignite in air, sodium tetraethyl-borate solution shall be prepared in a large-volume fume hood. Organotin is toxic and endocrine disruptor, so special care shall be taken.

NOTE: before use, all reagents stored below room temperature should be taken out and placed to reach room temperature.

8.2 Preparation of Sodium Tetraethyl-borate Solution

In an inert environment, weigh-take 2 g of sodium tetraethyl-borate (5.4); add 10 mL of tetrahydrofuran (5.5) to dissolve it.

Store this solution in an inert gas (5.11) environment. The validity period is 3 months.

NOTE: sodium tetraethyl-borate or its solution can be purchased in fixed weights. An example of preparation: transfer-take 10 mL of tetrahydrofuran into a 40 mL sample bottle with a screw cap; open the 2 g package of sodium tetraethyl-borate; add it to the sample bottle and dissolve it. If the sodium tetraethyl-borate is in 5 g package, accordingly increase the volume of the added tetrahydrofuran to ensure a concentration of approximately 0.2 g/mL.

8.3 Preparation of Standard Solution

8.3.1 Conversion of organotin cation

The standard substance of organotin chloride is available on the market, but the mass concentration of the standard curve and the expression of results are all expressed in terms of organotin cation, and the unit is mg/kg.

Example 1: the corresponding cation of Bu2SnCl2 is Bu2Sn2+.

Table 2 provides the amount of organotin chloride and the weighting factor for re-calculation

of cation (assuming that the chloride purity is 100%).

The target compound solution can be directly purchased with a certificated standard solution, or prepared by the user.

Each substance is separately prepared: use the analytical balance (6.2) to weigh-take an appropriate amount of the target compound (see Table 1); select a volumetric flask with an appropriate volume; use methanol (5.13) to dissolve it and reach a constant volume to the scale.

The concentration of the organotin cation is 1,000 mg/L.

Store the standard solution in the refrigerator to reduce the volatilization of the solvent, and the storage period shall not exceed one year.

8.3.5 Target compound - working solution (the mass concentration of organotin cation is

10 mg/L)

Use the pipette (6.5) to transfer-take an appropriate volume of the target compound - stock solution (8.3.4) to a volumetric flask of an appropriate volume. Use methanol (5.13) to reach a constant volume to the scale. Thus, the target compound - working solution with organotin cation concentration of 10 mg/L is obtained.

Store the target compound - working solution in the refrigerator to reduce the volatilization of the solvent, and the storage period shall not exceed one month.

8.4 Preparation of Tropolone Solution

Use the analytical balance (6.2) to weigh-take 0.500 g of tropolone (5.12) into a glass beaker;

use about 20 mL of methanol (5.13) to dissolve it, then, transfer it to a 100 mL volumetric flask.

Use methanol to dilute to the scale. Thus, tropolone solution with a concentration of 5 g/L is obtained.

Store this solution in the refrigerator to reduce the volatilization of the solvent, and the storage period is one month.

8.5 Preparation of Buffer Solution

Prepare sodium acetate solution with a concentration of 0.2 mol/L. For example, weigh-take

16.4 g of anhydrous sodium acetate (5.14) into 1 L of water (5.1); use glacial acetic acid (5.3)

to adjust the pH value to 4.5.

8.6 Preparation of Standard Curve

8.6.1 Optionally prepare standard solutions with a concentration of 100 g/L, 200 g/L, 300

g/L, 400 g/L and 500 g/L.

8.6.2 Use a micropipette (6.4) to draw 20 L, 40 L, 60 L, 80 L and 100 L of the target

compound - working solution (8.3.5). Respectively add them to containers containing 20 mL of methanol (5.13) / ethanol (5.2) mixed solvent (volume ratio 80 / 20).

8.6.3 Add an appropriate volume of internal standard substance - working solution (8.3.3).

8.6.4 Add 8 mL of pH 4.5 buffer solution (8.5).

8.6.5 Use the pipette (6.5) to draw 1 mL of tropolone solution (8.4) into the container.

8.6.6 Add 100 L of sodium tetraethyl-borate solution (8.2); use the horizontal mechanical

vibrator (6.9) to vigorously oscillate it for 30 min.

8.6.7 Use the pipette (6.5) to draw 2 mL of n-hexane (5.10) into the container; use the horizontal

mechanical vibrator (6.9) to vigorously oscillate it for 30 min.

8.6.8 After stratification, take the n-hexane phase for analysis by GC-MS.

NOTE: if necessary (to obtain a clear n-hexane layer), the centrifuge (6.8) may be used to perform centrifugation for 5 min.

8.7 Preparation of Sample Solution

8.7.1 Use the analytical balance (6.2) to weigh-take (1.0  0.1) g of specimen into a 50 mL glass

reaction flask with a screw stopper (6.3); record the mass of the specimen as m1, accurate to 0.1 mg.

8.7.2 Add 20 mL of methanol (5.13) / ethanol (5.2) mixed solvent (volume ratio 80 / 20).

8.7.3 Add an appropriate volume of internal standard substance - working solution (8.3.3).

8.7.4 Use the pipette (6.5) to draw 1 mL of tropolone solution (8.4) and add it to the glass

reaction flask with a screw stopper.

8.7.5 In the temperature-controlled ultrasonic generator (6.7), perform ultrasonic extraction at

(60  5) C for 1 h  5 min. Then, cool it to room temperature.

8.7.6 If necessary, centrifuge it for 5 min, then, transfer the supernatant to another container.

8.7.7 Add 8 mL of pH 4.5 buffer solution (8.5).

8.7.8 Add 100 L of sodium tetraethyl-borate solution (8.2); use the horizontal mechanical

vibrator (6.9) to vigorously oscillate it for 30 min.

8.7.9 Use the pipette (6.5) to draw 2 mL of n-hexane (5.10) into the container; use the horizontal

mechanical vibrator (6.9) to vigorously oscillate it for 30 min.

NOTE: Some sample solutions may generate air bubbles and pressure after adding reagents, so be careful to release excess air in the sealed container before oscillation, so as to ensure the safety.

8.7.10 If necessary (to obtain a clear n-hexane layer), perform centrifugation for 5 min.

8.7.11 After stratification, take the n-hexane phase for analysis by GC-MS.