Heavy Metals in Textiles

Instruments and Reagents

Product No. 173016 Spectroquant^® VIS Spectrophotometer Prove 100 or
Product No. 173017 Spectroquant^® UV/VIS Spectrophotometer Prove 300 or
Product No. 173018 Spectroquant^® UV/VIS Spectrophotometer Prove 600 or
Product No. 109751 Spectroquant^® Photometer NOVA 60
Product No. 114946 Rectangular cells 10 mm and/or
Product No. 114947 Rectangular cells 20 mm and/or
Product No. 114944 Rectangular cells 50 mm
Product No. 109531 MColorpHastTM pH-indicator strips pH 0 - 6
Product No. 105432 Ammonia solution 25 % for analysis
Product No. 114687 Spectroquant^® Crack-Set 10
Product No. 114724 Empty cells 16 mm with screw cap
Product No. 107209 Hydrogen peroxide 30 % (Perhydrol^®)for analysis
Product No. 100366 Lactic acid 90 % extra pure
Product No. 106404 Sodium chloride for analysis
Product No. 105590 Sodium hydroxide solution 32 % for analysis
Product No. 109072 Sulfuric acid 0.5 mol/l
Product No. 100731 Sulfuric acid 95 - 97 % for analysis
Product No. 108487 Urea for analysis
Product No. 116754 Water for analysis
Product No. 114552 Spectroquant^® Chromium Cell Test
Product No. 114541 Spectroquant^®COD (25 - 1500 mg/l)
Product No. 114691 Spectroquant^® COD (300 - 3500 mg/l)
Product No. 114767 Spectroquant^®Copper Test
Product No. 114761 Spectroquant^® Iron Test
Product No. 114785 Spectroquant^® Nickel Test
Product No. 171200 Spectroquant^® Thermoreactor TR 320 or
Product No. 171201 Spectroquant^® Thermoreactor TR 420 or
Product No. 171202 Spectroquant^® Thermoreactor TR 620
Product No. 109535 MColorpHast^TM Universal indicator strips pH 0 - 14
pH meter, e.g. WTW

Sample Extraction and Digestion Procedures

Extraction with 0.5 mol/l Sulfuric Acid

Cut the textile sample using a pair of scissors into pieces of approx. 5 by 5 mm. Mix 5.0 g, exactly weighed with 100 mL 0.5 mol/l sulfuric acid in a 200-mL Erlenmeyer flask. Close with a ground glass stopper and stir at 50 °C for 1 hour. Filter off solid parts using a folded filter and adjust the pH value of the filtrate with sodium hydroxide solution to 4 - 5 (pH-indicator strips or pH meter). Fill the sample in a 200-mL volumetric flask, make up to volume with water for analysis and mix.

Total acid mineralisation with sulfuric acid 95 - 97 % and Perhydrol^®

Cut the textile sample using a pair of scissors into pieces of approx. 5 by 5 mm. Mix 2.0 g, exactly weighed with 5 mL sulfuric acid 95 - 97 % in a 600-mL glass beaker. Heat on a hot plate until the mixture starts to decompose and becomes dark colored. Let cool and add carefully 5-mL portions of Perhydrol^®. Wait until the initial heavy reaction (foaming, release of gas) has decreased and heat until the mixture starts to foam. Again let cool and add another 5-mL portion of Perhydrol^®. Heat again until the mixture starts to foam. Repeat this step until the solution remains colorless in the heat. After cooling, dilute with 40 mL water for analysis and adjust the pH value to 4 - 5 with using sodium hydroxide 32 % (pH-indicator strips or pH meter). Transfer the mixture in a 200-mL volumetric flask and make up to volume with water for analysis, mix.

During the above described digestion all COD and color will be destroyed. Only for the analysis of Total Chromium Cr(III) and Cr(IV) an additional oxidising digestion using potassium peroxodisulfate (= K₂S₂O₈) must be done. All required reagents for total chromium determination are provided with this Chromium Cell Test.

Digestion Required for Total Chromium

Pipette 10.0 mL pretreated sample into an empty cell. Add 1 drop reagent Cr-1K and mix. Add 1 dose reagent Cr-2K (= K₂S₂O₈), close the cell tightly, and mix. Heat the cell at 120 °C in the preheated thermoreactor for 60 min. Allow the closed cell to cool to room temperature in a test-tube rack. Do not cool with cold water! Check the pH of the solution with Universal indicator strips. Adjust the pH with sodium hydroxide solution or sulfuric acid within the range 1 - 9.

Extraction Using Synthetic Sweat

Prepare the extractant solution as follows: Mix 5 g sodium chloride, 1 g urea and 1 g lactic acid

90 % with 900 mL water for analysis. Adjust the pH value to 6.4 using ammonia solution 25 % (pH-meter).

Cut the textile sample using a pair of scissors into pieces of approx. 5 by 5 mm. Mix 5.0 g, exactly weighted with 100 mL extractant solution in a 200-mL Erlenmeyer flask. Close with a ground glass stopper and stir at 50 °C for 1 hour. Filter off solids using a folded filter.

During the above described extraction COD will not be destroyed. To ensure that COD does not interfere at the determination, test the sample by measuring the COD with one of the above COD Cell Tests. Colored samples and samples containing COD must be digested by using the Crack-Set 10. If the COD value of the extracted sample is above 400 mg/l, dilute the sample to come into the range of 200 - 400 mg/l COD. The digestion using the Crack-Set 10 will oxidise the COD to CO₂ and destroy the color.

Therefore pipette 10.0 mL pretreated sample into an empty glass tube. Add 1 dose reagent R-1 (= K₂S₂O₈) when the COD value is below 200 mg/l [2 doses R-2 when the COD value is between 200 - 400 mg/l], close the tube tightly, and mix. Heat the tube at 120 °C in the preheated thermoreactor for 60 min. Allow the closed tube to cool to room temperature in the cell rack. Do not cool with cold water! Add 3 drops of reagent R-2 to the cool tube and mix. Check the pH of the solution with Universal indicator strips. Adjust the pH with sodium hydroxide solution or sulfuric acid within the range 4 - 8.

Determination of heavy metals after sulfuric acid extraction and digestion with Crack-Set 10:

Determine the leached heavy metals by means of the above Spectroquant^® tests. Follow the instruction given in the package inserts for the analysis.

Determination of heavy metals after total acid mineralization:

Determine the pretreated sample by means of the above Spectroquant^® tests. Follow the instruction given in the package inserts for the analysis. If only Copper, Iron, and Nickel need to be analysis, the additionally digestion using the potassium peroxodisulfate is not necessary. The pH of the digestied sample by analysis the above parameters must be within the range of 4 - 8. The potassium peroxodisulfate digestion is only required for the analysis of Total Chromium.

Determination of heavy metals after synthetic sweat extraction and digestion with Crack-Set 10:

Determine the leached heavy metals by means of the above Spectroquant^® tests. Follow the instruction given in the package inserts for the analysis.