ISO 17075-2:2017 pdf free download.Leather — Chemical determination of chromium(VI) content in leather — Part 2: Chromatographic method.
1 Scope
ISO 17075-2 specifies a method for determining chromium(Vl) 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.
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 ISO 17075-2, the results obtained with ISO 17075-2 are considered as the reference. The advantage of the method described in ISO 17075-2 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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of  ISO 17075-2. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2418, Leather — Chemical, physical and mechanical and fastness tests — Sampling location
ISO 3696, Water for analytical laboratory use — Speafication and test methods
ISO 4044:2017, Leather — Chemical tests— Preparation of chemical test samples
ISO 4684, Leather — Chemical tests — Determination of volatile matter
4 Principle
Extractable chromium( VI) is leached from the sample in phosphate bufferat pH 7.0 to 8.0. An aliquot of
the fiftered ex tract is analysed for Cr(Vl) using ion-exchange chromatography with IJV•VIS detection.
5 Chemicals
All reagents used shall have at least analytical grade purity.
5.1 Extraction solution
Dissolve 22,8 g dipotasslum hydrogenpbosphate KHPO43H20 in 1 000 ml water (Z)’ adjusted to pH 8,0 * 0,1 with phosphoric acid (2). Degas this solution with either argon or nitrogen (i) or ultrasonic bath.
Standard practice is to make up a fresh solution each day. However, the solutioncan be kept for up toone week in a refrigerator at (4 ± 3) °C but shall be warmed to room temperature and degassed prior to use.
5.2 Phosphonc acid solution
700 ml o-phosphoric acid, p 1.71 g/ml, made up to 1 000 ml with water (5.Z.
First add approximately 200 ml of deionLsed water (Si) to a 1 000 ml volumetric flask, then add the
700 ml ofo•phosphoricacid and dilute to the mark with delonised water.
5.3 Potassium dichromate (KZCrZO7), dried for(16 ± 2) h at(102 ± 2)°C.
5.4 Chramium(Vl) stock solution
Dissolve 2,829 g potassium dichromate (KCr2O7) in water (52) in a volumetric flask and make up to 1 000 ml with water (5.2). 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 Chroniium(Vl) standard solution
Pipette I ml of solution (5.4) into a 1 000 ml volumetric flask and make up to the markwith extraction solution (5.1). One millilitre of this solution contains I tg of chromium.
The solution can be kept for up to one week In a refrigerator at (4 t 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.
5.7 Distilled or deionised water, Grade 3 quality as specified in ISO 3696.
6 Apparatus and materials
Usual laboratory equipment and, in particular, the following.
6.1 Suitable niechanical orbital shaker. (100± 10) min .
62 Conical flask, of capacity 250 ml.. with stoppec
6.3 Aerationtuheatid flow meter, suitable for allow rate of(50 ± 10) mI/mm.
6.4 Membrane filter. 0,45 pm pore size Ipolytetrafluoroethylene (PTFE) or polyamide 661.
6.5 Common Iaboratoryglassware and pipettes.
66 Ion-exchange chromatograph, with liv detector or high performance liquid chromatograph (HPLC) with anion-exchange column and 1W detector. It is recommended a photo diode array dvteclor(DAD).
6.7 Analytical balance, capable of weighingto 0,1 mg.
6.8 Suitable vials for HPLC.
6.9 Sharp cutting tool or blade, suitable for cutting the leather Into 3 mm to 5 mm plecc.
7 Procedure
7.1 Sampling and preparation of samples
If possible, sample in accordance with ISO 2418. If sampling in accordance with ISO 2418 is not possible (e.g. leathers from finished products like shoes, garments), details about sampling shall be given in the test report.
Prepare the leather sample by cutting (.9) Into small pieces according to the met hod specified In
ISO 4044:2017,6.3.
7.2 Preparation of analytical solution
Weigh (fz.Z)approximately(2 ± 0,1)gofleatherpieces tothe nearest 0,001g. Pipette lOOmI of degassed solution (1) into a 250 ml conical flask (LL2). Displace oxygen by passing oxygen-free argon (or nitrogen) () Into the flask for 5 mm with a volume flow of (50 ± 10) mI/mm. Remove the aeration tube (j). add the leather and close the flask with a stopper. Record the extract volume as V0.
Shake the conical flask with the leather pieces for 3 h ± 5 mm on a mechanical orbital shaker at (100± 10) mm”t (1) at room temperature to extract the chromlum(VI).
Shake the suspension in a smooth circular movement to keep the leather pieces from adhering to the wall of the flask and avoid shaking faster than specified.
Immediately after completing the 3 h of ext ractlor filter the contents of the conical flask through a membrane filter Into a glass or plastic vessel with lid. Check the pH of the solution. The pH of the solution shallbe between 7.Oand8,0. lfthe pH of the solution Is not within this range, start the complete procedure again.
Consider using a smaller sample mass, ifthe pH is not between 7,0 and 8,0. In this case, the quantification limit will be increased.
Transfer anal Iquot of the filtered extract Into a vial ().
7.3 Chromatographic conditions
Determination of chromium(Vl) is performed using the ion chromatographic technique. As the Instrumental equipment of the laboratories may vary, no specific applicable instructions can be provided for analysis. Hower, the operating parameters and examples of the ion chromatographic analysis for chromium( VI) listed In Annexes B andL have been successfully tested and used. Annex B determines chromium(Vl) by direct detection or chromate peak at 372 nm. Annex C determines chromium(Vl) after a post.coiumn reaction with l.5diphenyicarbazide by measuring the absorption peakat 540 nm.
The method used should be verified using the recovery rate determination (Z.) and the resuits observed should be In the range as listed In Annex A.
Record the injection volume as VM and record the area of the chromate peak ask
7.4 Calibration
The content of chromium( VI) in leather is determined with an external standard calibration.
Prepare calibration solutions from the standard solution (ii). The chromium(VI) concentration in
these solutions should cover the expected range of measurement.
Plot a suitable calibration curve by using at least five standards, within the range 1 ml to 25 ml of standard solution (). Pipette the given volumes of standard solution (ii) into 25 ml volumetric flasks. Make up to volume with the extraction soLution (1). mix well and transfer a suitable aliquot volume intoa vial
Prepare calibration levels asspecified in Table 1.
8.3 Expression of results
The chromlum( VI) content Is given In milligrams per kilogram (mg/kg) rounded to the nearest 0,1 mg. The content is based on dry matter. The solatile mattel determined according to ISO 4684, is given in percent (%) rounded to the nearest 0.1 %.
The extraction matrix for teat her is complex and results below 3 mg/kg show larw variations and have limited reliability; therefore the quantification limit shall be 3 mg/kg.
9 Test report
The test reportshall include the following information:
a) the chromium(Vl) content(s) obtained from Hi. to the nearest 0,1 mg/kg;
b) a reference to this document, Le. ISO 17075-2:2017;
c) a description of the sample tested and details about sampling (Li). if necessary;
d) a brief description of the chromatographic technique (Le. direct detection technique or whether a post-column reaction was used);
e) the volatile matter of the leather in percent (%) to the nearest 0,1%;
f) the recovery rate in percent (%);
g) details of any deviations from the procedure.3