1、BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06Leather - Chemical determination of chromic oxide contentPart 3: Quantification by atomic absorption spectrometryBS EN ISO 53983:2018National forewordThis British Standard is the UK implementation of EN ISO 53983:2018.
2、It is identical to ISO 53983:2018. It supersedes BS EN ISO 53983:2007, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee TCI/69, Footwear Clause 5 refers to ISO 4044 for preparing the sample rather than grinding the leather; the description of suitable A
3、AS equipment, previously in 8.2.1, has been moved to a new informative Annex B.A list of all parts in the ISO 5398 series can be found on the ISO website.iv ISO 2018 All rights reservedBS EN ISO 53983:2018ISO 5398-3:2018IntroductionThe ISO 5398 series comprises four parts, each describing methods su
4、itable for the determination of the chromic oxide content in leather. The different techniques have been described to reflect the variations in industrial practice compared with the more sensitive analytical equipment available for test laboratories. Variations also exist in the range of chromic oxi
5、de that the methods are deemed suitable to quantify.This document describes a technique that is suitable for determining chromium more precisely than those described in ISO 53981 and ISO 53982. It requires the use of sophisticated analytical equipment, such as atomic absorption spectroscopy. ISO 201
6、8 All rights reserved vBS EN ISO 53983:2018This page deliberately left blankLeather - Chemical determination of chromic oxide content Part 3: Quantification by atomic absorption spectrometry1 ScopeThis document describes a method for the determination of chromium in aqueous solution obtained from le
7、ather. This is an analysis for total chromium in leather; it is not compound specific or specific to its oxidation state.This method describes the determination of chromium by atomic absorption spectrometry and is applicable to leathers which are expected to have chromic oxide contents in excess of
8、5 mg/kg. Two techniques for the preparation of the solution to be analysed are included. In the case of disputes, the wet oxidation technique is to be used.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requiremen
9、ts of this document. 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 locationISO 3696, Water for analytical l
10、aboratory use Specification and test methodsISO 4044, Leather Chemical tests Preparation of chemical test samplesISO 4684, Leather Chemical tests Determination of volatile matterEN 14602, Footwear Test methods for the assessment of ecological criteria3 Terms and definitionsFor the purposes of this d
11、ocument, the following terms and definitions apply.ISO and IEC maintain terminological databases for use in standardization at the following addresses: ISO Online browsing platform: available at https:/www.iso.org/obp IEC Electropedia: available at http:/www.electropedia.org/3.1chromic oxide content
12、amount of chromium in leather, determined by this method and reported as chromic oxideNote 1 to entry: The chromic oxide content is expressed in milligrams per kilogram (mg/kg), based on dry matter.4 PrincipleThe chromium present in the leather is solubilized in the hexavalent state followed by anal
13、ysis of the solution by atomic absorption spectrometry.INTERNATIONAL STANDARDISO 5398-3:2018(E) ISO 2018 All rights reserved 1BS EN ISO 53983:2018ISO 5398-3:20185 Sampling and sample preparationSample in accordance with ISO 2418 and prepare the leather in accordance with ISO 4044. If sampling in acc
14、ordance with ISO 2418 is not possible (as in the case of leathers from finished products such as shoes or garments), details about sampling shall be given together with the test report.Weigh 2 g of the prepared leather to the nearest 0,001 g. From every leather sample, a minimum of two determination
15、s shall be made.6 ReagentsUnless otherwise stated, only analytical grade chemicals are to be used. The water shall be grade 3 in accordance with ISO 3696. All solutions are aqueous solutions.6.1 Reagents for wet oxidation method6.1.1 Nitric acid, 70 %.6.1.2 Sulfuric acid, concentrated (98 %), and pe
16、rchloric acid (60 % to 70 %), mixed together in the ratio of 1:3 by volume.6.2 Reagents for atomic absorption spectrometry6.2.1 Potassium dichromate (K2Cr2O7), dried for 16 h 2 h at 102 C 2 C.For safety reasons, it is advisable to use already prepared certified commercial solution. (For the concentr
17、ation see 6.2.3.)6.2.2 Potassium chloride (KCl).6.2.3 Standard dichromate solution: dissolve 2,829 g of potassium dichromate (6.2.1) in water in a volumetric flask and make up to 1 000 ml with water. 1 ml of this solution contains 1 mg of chromium.NOTE This solution is available commercially.6.2.4 P
18、otassium chloride solution: dissolve 2 g of potassium chloride (6.2.2) in 1 l of distilled water. Add 1 ml of nitric acid (6.1.1) to each litre prepared.7 ApparatusThe usual laboratory apparatus is required and, in particular, the following.7.1 Conical flask, 500 ml, with ground glass stopper.7.2 At
19、omic absorption spectrophotometer, with suitable hollow cathode lamp and nitrous oxide burner head or high solids nitrous oxide burner head.7.3 Filtration device, using glass fibre (GFC) or membrane type filters.7.4 Antibumping granules or similar, (wet oxidation method).2 ISO 2018 All rights reserv
20、edBS EN ISO 53983:2018ISO 5398-3:20188 Methods8.1 Preparation of analytical solution8.1.1 Wet oxidation methodWARNING It is imperative that 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
21、 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 (6.1.2) 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
22、 the reaction mixture begins to turn orange, lower the flame. After a complete change of colour, heat gently for at least 2 min. Allow 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
23、the use of the individual acids as it prevents the accidental use of perchloric acid alone.In the case of incomplete oxidation (i.e. 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 methodThe sa
24、mple for analysis can also be prepared through the application of microwaveassisted digestion (MAD). The procedure described in EN 14602 shall be followed.8.2 Measurement of the aqueous solution8.2.1 GeneralPrepare the atomic absorption spectrophotometer (7.2) by following the manufacturers instruct
25、ions for adjusting all instrument parameters. See Annex B for an example of suitable equipment.8.2.2 Preparation of calibration graphPrepare standard solutions by pipetting 10 ml of the standard dichromate solution (6.2.3) into a 100 ml volumetric flask and making up to volume with distilled water.
26、Pipette 2,0 ml, 4,0 ml, 6,0 ml and 8,0 ml aliquots of this solution into 100 ml volumetric flasks and make up to volume with potassium chloride solution (6.2.4). These solutions contain 2,0 g/ml, 4,0 g/ml, 6,0 g/ml and 8,0 g/ml of chromium, respectively.Aspirate the standard solutions and prepare a
27、standard calibration curve. This calibration may be retained in the spectrophotometers memory if preferred.8.2.3 Analysis of the test solutionTransfer the contents from the analytical solution obtained from 8.1 into a 250 ml volumetric flask and make up to volume with the potassium chloride solution
28、 (6.2.4), mixing well.This solution can be analysed directly following filtration (7.3), provided it does not contain more than 7,5 g/ml of chromium. Otherwise, the solution should be diluted accordingly.Aspirate the test solution and determine the absorbance obtained. Calculate the concentration of
29、 chromium in the solution using the standard calibration curve. Note that if the calibration is retained in the spectrophotometers memory, then the reading may be given directly in terms of concentration. ISO 2018 All rights reserved 3BS EN ISO 53983:2018ISO 5398-3:2018If the absorbance is outside t
30、he 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 resultsCalculate the chromic oxide content in the leather, wCr, expressed in milligra
31、ms per kilogram (mg/kg), using the following equation:wVFmCr01,462=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);m0is the original mass of leather, in gram
32、s (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:Fw=100100Wwhere wWis the volatile matter content, according to ISO 4684 (see Annex A), in per cent by mass.It is permissible, if required, to quote the results b
33、ased on the dry, degreased mass of the sample.10 Test reportThe test report shall include the following:a) a reference to this document (i.e. ISO 53983);b) a description of the leather;c) a reference to the method used for sample preparation, type of digestion and measurement;d) the volatile matter
34、content of the leather, in per cent;e) the results obtained, in milligrams per kilogram (mg/kg);f) details of any deviations from the described procedures.4 ISO 2018 All rights reservedBS EN ISO 53983:2018ISO 5398-3:2018Annex A (informative) Determination of water and other volatile matterThe volati
35、le 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. T
36、he loss in mass during initial drying is added to the loss in mass after drying according to ISO 4684. ISO 2018 All rights reserved 5BS EN ISO 53983:2018ISO 5398-3:2018Annex B (informative) Suitable atomic absorption spectrometry (AAS) equipmentAn example of suitable AAS equipment is given below. Pr
37、epare the atomic absorption spectrophotometer (7.2) by following the manufacturers instructions for adjusting all instrument parameters.Where it is noted that the setting is as recommended by the manufacturer, then the settings used should be those described by the manufacturer for chromium.Lamp cur
38、rent as recommended by manufacturerSlit width/band pass 0,5 nmWavelength 357,9 nmBurner head single slot nitrous oxide or high solids nitrous oxide to give red cone 10 mm to 20 mm highFuel flow as recommended by manufacturerOxidant flow as recommended by manufacturerPhotomultiplier voltage as requir
39、ed to give optimum signal/noise ratioBefore carrying out the spectrometric measurements, set up the spectrophotometer according to the manufacturers instructions by aspirating a 4,0 g/ml calibration solution. Optimize the aspiration and flame conditions (aspiration rate, nature of the flame, positio
40、ns of the optical beam in the flame).Aspirate distilled water and adjust controls to give a steady zero (baseline) reading.6 ISO 2018 All rights reservedBS EN ISO 53983:2018This page deliberately left blankThis page deliberately left blankBSI is the national body responsible for preparing British St
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