Analytical Method: Heavy metals in textiles

Instruments and Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or

Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or

Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60

Cat.No. 114946  Rectangular cells 10 mm and/or

Cat.No. 114947  Rectangular cells 20 mm and/or
Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 109531  MColorpHastTM pH-indicator strips pH 0 - 6
Cat.No. 105432  Ammonia solution 25 % for analysis
Cat.No. 114687  Spectroquant® Crack-Set 10
Cat.No. 114724  Empty cells 16 mm with screw cap
Cat.No. 107209  Hydrogen peroxide 30 % (Perhydrol®)for analysis
Cat.No. 100366  Lactic acid 90 % extra pure
Cat.No. 106404  Sodium chloride for analysis
Cat.No. 105590  Sodium hydroxide solution 32 % for analysis
Cat.No. 109072  Sulfuric acid 0.5 mol/l
Cat.No. 100731  Sulfuric acid 95 - 97 % for analysis
Cat.No. 108487  Urea for analysis
Cat.No. 116754  Water for analysis
Cat.No. 114552  Spectroquant® Chromium Cell Test
Cat.No. 114541  Spectroquant® COD (25 - 1500 mg/l)
Cat.No. 114691  Spectroquant® COD (300 - 3500 mg/l)
Cat.No. 114767  Spectroquant® Copper Test
Cat.No. 114761  Spectroquant® Iron Test
Cat.No. 114785  Spectroquant® Nickel Test
Cat.No. 171200  Spectroquant® Thermoreactor TR 320 or
Cat.No. 171201  Spectroquant® Thermoreactor TR 420 or
Cat.No. 171202  Spectroquant® Thermoreactor TR 620
Cat.No. 109535  MColorpHastTM Universal indicator strips pH 0 - 14
pH meter, e.g. WTW
 
Sample extraction and digestion procedures:
 
1. 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.
 
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.
 
For further treatment of the extract see determination of heavy metals.
 
2. 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.
 
For further treatment of the extract see determination of heavy metals.
 
3. 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.
 
For further treatment of the extract see determination of heavy metals.
 
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.
 
Remark:
For customers using spectrophotometers we are offering programming data for spectrophotometers which contains all information about the necessary data for entering in such an instrument.

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