BS EN ISO 17075-2:2017 pdf.Leather – Chemical Determination Of Chromium(VI) Content In Leather – Part2:Chromatographic Method.
BS EN ISO 17075-2 specifies a method for determining chromium(VI) in solutions leached from leather under defined conditions. The method described is suitable to quantify the chromium(VI) content in leathers down to 3 mg/kg.
BS EN ISO 17075-2 is applicable to all leather types.
The results obtained from this method are strictly dependent on the extraction conditions. Results obtained by using other extraction procedures (extraction solution, pH, extraction time, etc.) are not comparable with the results produced by the procedure described in this document.
If a leather sample is tested with both ISO 17075-1 and this document, the results obtained with this document are considered as the reference. The advantage of the method described in this document is that there are no interferences from the colour of the extract. Nevertheless, interlaboratory trials do not show significant differences (see Annex D) and the results are comparable between both methods.
4 Principle
Extractable chromium(VI) is leached from the sample in phosphate buffer at pH 7,0 to 8,0. An aliquot of
the filtered extract is analysed for Cr(VI) using ion-exchange chromatography with UV-VIS detection.
5 Chemicals
All reagents used shall have at least analytical grade purity.
5.1 Extraction solution
Dissolve 22,8 g dipotassium hydrogenphosphate K211P0431120 in 1 000 ml water (Z) adjusted to pH 8,0 ± 0,1 with phosphoric acid (52). Degas this solution with either argon or nitrogen (5) or ultrasonic bath.
Standard practice is to make up a fresh solution each day. However, the solution can be kept for up to one week in a refrigerator at (4 ± 3) °C but shall be warmed to room temperature and degassed prior to use.
5.2 Phosphoric acid solution
700 ml o-phosphoric acid, p = 1,71 g/ml, made up to 1 000 ml with water (51).
First add approximately 200 ml of deionised water (1) to a 1 000 ml volumetric flask, then add the 700 ml of o-phosphoric acid and dilute to the mark with deionised water.
5.3 Potassium dichromate (K2Cr2O7), dried for (16 ± 2) h at (102 ± 2) °C.
5.4 Chromium(V1) stock solution
Dissolve 2,829 g potassium dichromate (K2Cr207) (5) in water (.51) in a volumetric flask and make up to 1 000 ml with water (51). One millilitre of this solution contains 1 mg of chromium.
A stock solution at this concentration level of hexavalent chromium is an alternative available commercially.
5.5 Chromium(VI) standard solution
Pipette 1 ml of solution (.5A) into a 1 000 ml volumetric flask and make up to the mark with extraction solution (ii). One millilitre of this solution contains 1 ig of chromium.
The solution can be kept for up to one week in a refrigerator at (4 ± 3) °C but shall be warmed to room temperature prior to use.
A stock solution of hexavalent chromium at this concentration level is an alternative available commercially.
5.6 Argon or nitrogen, oxygen-free
Preference should be given to argon as an inert gas instead of nitrogen because argon has a higher specific mass than air.