1、October 2007DEUTSCHE NORM English price group 8No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 59.140.30!$J it is not
2、compound specific or specific to its oxidation state. This method describes the determination of chromium by inductively coupled plasma optical emission spectrometry and is applicable to leathers which are expected to have chromic oxide contents in excess of 1 mg/kg. Two techniques for the preparati
3、on of the solution to be analysed are included. In the case of dispute, the wet oxidation technique is to be used. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated refer
4、ences, the latest edition of the referenced document (including any amendments) applies. ISO 2418, Leather Chemical, physical and mechanical and fastness tests Sampling location ISO 3696:1987, Water for analytical laboratory use Specification and test methods ISO 4044, Leather Chemical tests Prepara
5、tion of chemical test samples EN 14602, Footwear Test methods for the assessment of ecological criteria ISO 4684, Leather Chemical tests Determination of volatile matter ISO 11885, Water quality Determination of selected elements by inductively coupled plasma optical emission spectroscopy (ICP-OES)
6、3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 chromic oxide content amount of chromium in leather, determined by this method and reported as chromic oxide NOTE The chromic oxide content is expressed in milligrams per kilogram (mg/kg), based
7、 on dry matter. 5EN ISO 5398-4:2007 (E)4 Principle The chromium present in the leather is solubilized in the hexavalent state followed by analysis of the solution by inductively coupled plasma optical emission spectrometer. 5 Sampling and sample preparation If possible, sample in accordance with ISO
8、 2418 and grind leather in accordance with ISO 4044. If sampling in accordance with ISO 2418 is not possible (an in the case of leathers from finished products like shoes, garments), details about sampling shall be given together with the test report. Weigh 2 g of the ground leather to the nearest 0
9、,001 g. From every leather, a minimum of two determinations shall be made. 6 Reagents Unless otherwise stated, only analytical grade chemicals are to be used. The water shall be grade 3 in accordance with ISO 3696:1987. All solutions are aqueous solutions. 6.1 Wet oxidation method 6.1.1 Nitric acid,
10、 70 %. 6.1.2 Sulfuric acid, concentrated (98 %), and perchloric acid (60 % to 70 %), mixed together in the ratio of 1:3 by volume. 6.2 ICPOES 6.2.1 Potassium dichromate (K2Cr2O7), dried for 16 h 2 h at 102 C 2 C. 6.2.2 Standard dichromate solution: dissolve 2,829 g potassium dichromate (6.2.1) in wa
11、ter in a volumetric flask and make up to 1 000 ml with water. 1 ml of this solution contains 1 mg of chromium. 7 Apparatus Usual laboratory apparatus is required and, in particular, the following. 7.1 Conical flask, 500 ml, with ground glass stopper. 7.2 Inductively coupled plasma optical emission s
12、pectrometer, as described in ISO 11885. 7.3 Filtration device, using glass fibre (GFC) or membrane type filters. 7.4 Antibumping granules (or similar) (wet oxidation method). 6EN ISO 5398-4:2007 (E)8 Methods 8.1 Preparation of analytical solution 8.1.1 Wet oxidation method WARNING It is imperative t
13、hat nitric acid is added first because of the possible explosive reaction of perchloric acid with leather. Accurately weigh a mass of leather (see Clause 5) into the conical flask (7.1). Add 10 ml of nitric acid (6.1.1) and allow to stand for 2 min. Add 15 ml of mixed sulfuric/perchloric acids (6.1.
14、2) and a few antibumping granules (7.4). Place a funnel or splash bulb in the neck of the flask and heat to boiling on a wire gauze over a moderate flame. As soon as the reaction mixture begins to turn orange, lower the flame. After a complete change of colour, heat gently for at least 2 min. Allow
15、to cool in air for 5 min and dilute to approximately 200 ml. Boil for 10 min to eliminate any chlorine. The use of a sulfuric/perchloric acid mixture is preferred to the use of the individual acids as it prevents the accidental use of perchloric acid alone. In the case of incomplete oxidation (i.e.
16、the solution does not change to an orange colour), it is permissible to add further mixed sulfuric/perchloric acid to the sample. 8.1.2 Microwave digestion The sample for analysis can also be prepared through application of microwave-assisted digestion (MAD). If this is to be used, then the procedur
17、e described in EN 14602 shall be followed. 8.2 Measurement of the aqueous solution 8.2.1 General Prepare the inductively coupled plasma optical emission spectrometer (7.2) by following the manufacturers instructions for adjusting all the instruments parameters. Below are some recommended settings; h
18、owever, ICP manufacturers have their own recommended settings for chromium which should be used when available. For further information, refer to ISO 11885. Plasma argon flow: 15 l/min Auxiliary argon flow: 0,5 l/min Nebulizer argon flow: 0,8 l/min Power: 1 300 W Gas: Argon 4.6 Sample flow rate: 1,3
19、 ml/min Sample flash rate: 4,0 ml/min Replicates: 3 Peak algorithms: Peak area, 3 points with 2 points background correction Wavelength: 357 nm, 869 nm 7EN ISO 5398-4:2007 (E)Before carrying out the spectrometric measurements, set up the spectrometer according to the manufacturers instructions by as
20、pirating a 1,0 mg/l Mn2+(axial view torch) calibration solution. Optimize the aspiration and plasma condition (aspiration rate, position of the torch module). Aspirate distilled water and adjust controls to give a steady zero (base line) reading. 8.2.2 Preparation of calibration graph Prepare standa
21、rd solutions by pipetting 10 ml of the standard dichromate solution (6.2.2) into a 100 ml volumetric flask and making up to volume with distilled water. Pipette 1,0 ml, 2,0 ml, 4,0 ml and 6,0 ml aliquots of this solution into 100 ml volumetric flasks and make up to volume with distilled water. These
22、 solutions contain 1,0 g/ml, 2,0 g/ml, 4,0 g/ml and 6,0 g/ml of chromium, respectively. Aspirate the standard solutions and prepare a standard calibration curve. This calibration may be retained in the spectrophotometers memory if preferred. 8.2.3 Analysis of the test solution Transfer the analytica
23、l solution obtained from 8.1 into a 250 ml volumetric flask and make up the volume with distilled water, mixing well. This solution can be analysed directly following filtration (7.3), provided it does not contain more than 5,0 g/ml of chromium. Otherwise, the solution should be diluted accordingly.
24、 Aspirate the test solution and determine the absorbance obtained. Calculate the concentration of chromium in the solution by use of the standard calibration curve. NOTE If the calibration is retained in the spectrophotometers memory, then the reading can be given directly in terms of concentration.
25、 If the absorbance is outside the range of the calibration standards, the analysis should be repeated either using a smaller sample size or with an appropriate dilution of the solution obtained from 8.1.1 or 8.1.2. 9 Calculation and expression of results Calculate the chromic oxide content in the le
26、ather, wCr, expressed in milligrams per kilogram (mg/kg), using the following equation: Cr01,462 VFwm= where is the concentration of chromium determined in 8.2.3, in micrograms per millilitre (g/ml); V is the total volume, in millilitres (ml), (if no additional dilution is required, V = 250 ml); m0i
27、s the original mass of leather, in grams (g); 1,462 is the correction factor to convert Cr to Cr2O3;F is the factor to correct to 0 % volatile matter; it is calculated as follows: W100100Fw=where wWis the volatile matter content, based on ISO 4684, in percentage by mass. It is permissible, if requir
28、ed, to quote the results based on the dry, degreased mass of the sample. 8EN ISO 5398-4:2007 (E)10 Test report The test report shall include the following: a) a reference to this part of ISO 5398 (ISO 5398-4:2007); b) a description of the leather; c) a reference to the method used for sample prepara
29、tion, type of digestion and measurement; d) the volatile matter content of the leather, in percentage; e) the results obtained, in milligrams per kilogram (mg/kg); f) details of any deviations from the described procedures. 9EN ISO 5398-4:2007 (E)Annex A (informative) Determination of water and othe
30、r volatile matter The volatile matter content of leathers is determined according to ISO 4684. The volatile matter content of the leather is determined from a sample of ground leather prepared for the chromium determination. Wet leathers are dried before the determination of the volatile matter content according to ISO 4684. The loss in mass during initial drying is added to the loss in mass after drying according to ISO 4684. 10EN ISO 5398-4:2007 (E)
