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1、? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? BS EN 15479:2009 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 15479 January 2009 ICS 65.080Supersedes CEN/TS 15479:2006 English Version Fertilizers - Spectrophotometric determination of biuret in urea Engrais - Dtermination photomtr
2、ique du biuret dans lure Dngemittel - Spektrometrische Bestimmung von Biuret in Harnstoff This European Standard was approved by CEN on 30 November 2008. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the sta
3、tus of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German).
4、A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republ
5、ic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE N
6、ORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2009 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15479:2009: E BS EN 15479:2009 EN 15479:2009 (E) 2 Contents Page Foreword 3 1Sco
7、pe 4 2Normative references 4 3Terms and definitions .4 4Principle 4 5Reagents .4 6Apparatus .5 7Sampling and sample preparation .6 8Procedure .6 9Calculation and expression of the result 7 10Precision .7 11Test report 8 Annex A (informative) Results of the inter-laboratory tests .9 Bibliography . 10
8、 ? BS EN 15479:2009 EN 15479:2009 (E) 3 Foreword This document (EN 15479:2009) has been prepared by Technical Committee CEN/TC 260 “ Fertilizers and liming materials” , the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publica
9、tion of an identical text or by endorsement, at the latest by July 2009, and conflicting national standards shall be withdrawn at the latest by July 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall no
10、t be held responsible for identifying any or all such patent rights. This document supersedes CEN/TS 15479:2006. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. According to the CEN/CENELEC Internal Regulations, the nat
11、ional standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
12、 Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. ? BS EN 15479:2009 EN 15479:2009 (E) 4 1 Scope This European Standard specifies a method for the determination of biuret in urea. The method is applicable to urea and urea-based fertilizers. 2 Normativ
13、e references The following referenced documents are indispensable for the application 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. EN 1482-2, Fertilizers and liming ma
14、terials Sampling and sample preparation Part 2: Sample preparation EN 12944-1:1999, Fertilizers and liming materials and soil improvers Vocabulary Part 1: General terms EN 12944-2:1999, Fertilizers and liming materials and soil improvers Vocabulary Part 2: Terms relating to fertilizers EN ISO 3696:1
15、995, Water for analytical laboratory use Specification and test methods (ISO 3696:1987) 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply. 4 Principle In an alkaline medium in the presence of potassium sodium tartr
16、ate, biuret and bivalent copper form a violet cupric compound. The absorbance of the solution is measured at a wavelength of about 546 nm. 5 Reagents 5.1 General Use only reagents of recognized analytical grade and distilled or demineralized water, free from carbon dioxide and ammonia (grade 3 accor
17、ding to EN ISO 3696:1995). The quality of the water is particularly important in this determination. 5.2 Methanol 5.3 Sulfuric acid solution, c = approximately 0,05 mol/l. 5.4 Sodium hydroxide solution, c = approximately 0,1 mol/l. 5.5 Alkaline solution of potassium sodium tartrate In a graduated on
18、e-litre flask, dissolve 40 g of sodium hydroxide in 500 ml of water and leave to cool. Add 50 g of potassium sodium tartrate (NaKC4H4O64H2O). Make up to the mark and leave standing for 24 h before use. ? BS EN 15479:2009 EN 15479:2009 (E) 5 5.6 Solution of copper sulfate In a graduated one-litre fla
19、sk dissolve 15 g of copper sulfate (CuSO45H2O) in 500 ml of water. Make up to the mark. 5.7 Freshly prepared biuret standard solution In a 250 ml graduated flask, dissolve 0,250 g of pure biuret1 in water. Make up to 250 ml. 1 ml of this solution contains 0,001 g of biuret. 5.8 Indicator solution In
20、 a graduated 100 ml flask, dissolve 0,1 g of methyl red in 50 ml of 95 % ethanol, make up to 100 ml with water. Filter if any insoluble remain. This indicator is red in acid solution and yellow in alkaline solution. 6 Apparatus 6.1 Spectrometer or photometer With filters with a sensitivity and preci
21、sion to permit measures of less than 0,5 % factor of transmission to be produced. The factor of transmission, T, is given by the following equation: Jo J T =(1) The opacity, O, is given by the following equation: J Jo O =(2) The absorbance, E, is given by the following equation: OElog=(3) The absorb
22、ance per unit of optical run, k, is given by the following equation: s E k =(4) The coefficient of specific absorbance, K, is given by the following equation: s E K = (5) where Jo is the intensity of the beam of monochromatic rays (of a determinate wavelength) before it passes through a transparent
23、body; J is the intensity of this beam after the passage; 1 Biuret can be purified beforehand by washing with an ammoniacal solution (10 %), then with acetone and dried in a vacuum. ? BS EN 15479:2009 EN 15479:2009 (E) 6 s is the thickness of the layer in centimetres; ? is the mass concentration in m
24、illigrams per litre; k is the specific factor for each substance in the Lambert-Beer law. 6.2 Graduated flasks, capacity of 100 ml, 250 ml and 1 000 ml. 6.3 Graduated pipettes, capacity of 2 ml, 5 ml, 10 ml, 20 ml, 25 ml and 50 ml, or a 25 ml burette, graduated to 0,05 ml. 6.4 Beaker, capacity 250 m
25、l. 6.5 Glass column for cation exchange resin Height 20 cm, diameter 25 mm, with a bottom plate of nylon gauze with a mesh width of 0,1 mm and ending in a narrow outlet with tap. The column is filled with cation exchange resin (strong cation: e. g. Duolite C20) to a height of about 120 mm. Before us
26、ing the column, the resin has first to be regenerated with 100 ml hydrochloric acid (hydrochloric acid, approximately 4 mol/l solution) and subsequently rinsed with water until the eluent is free from acid. After each determination the resin has to be regenerated. The usable capacity of the cation r
27、esin has to be great enough to be sure all the ammonia is caught. The total volume of the resin is about 60 cm3; the usable capacity is about 60 milli-equivalents. 7 Sampling and sample preparation Sampling is not part of the method specified in this document. A recommended sampling method is given
28、in EN 1482-1. Sample preparation shall be carried out in accordance with EN 1482-2. 8 Procedure 8.1 Preparation of the calibration curve Transfer 0 ml, 2 ml, 5 ml, 10 ml, 20 ml, 25 ml and 50 ml aliquots of biuret standard solution (5.7) into a series of seven graduated 100 ml flasks. Make up the vol
29、umes to about 50 ml with water, add one drop of indicator (5.8) and neutralize, if necessary, with sulfuric acid 0,05 mol/l (5.3). Stir in 20 ml of the alkaline tartrate solution (5.5) then 20 ml of the copper sulfate solution (5.6). These solutions shall be measured with two precision burettes or b
30、etter still with pipettes. Make up to 100 ml with water, mix and leave standing for 15 min at (30 2) C. With the “ 0” biuret standard solution as a reference, measure the absorbance of each solution at a wavelength of about 546 nm using cells of a suitable path length. Plot the calibration curve usi
31、ng the absorbance rate as the ordinate and the corresponding quantities of biuret, in milligrams, as the abscissa. ? BS EN 15479:2009 EN 15479:2009 (E) 7 8.2 Preparation of the solution to be analysed Weigh, to the nearest 0,001 g, 10 g of the prepared sample; dissolve in about 150 ml of water in a
32、250 ml graduated flask, and make up to the mark. Filter if necessary. Weigh to the nearest 0,001 g about 25 g of the ammoniumsulfate containing sample. Transfer into a beaker glass of 250 ml with about 100 ml of water at about 70 C and dissolve. Filter the solution over a Bchner funnel with a glass
33、fibre filter and wash the filter with approximately 50 ml of water. Transfer the filtrate in a volumetric flask of 250 ml. Bring the temperature to 20 C, dilute to the mark with water and mix. Pipette 100 ml of the solution and pass it through the cation resin with a speed of approximately 150 ml/h.
34、 Collect the eluate in a 250 ml volumetric flask. Wash the resin with water until a total volume of approximately 220 ml is obtained in the volumetric flask. Dilute to the mark with water and mix. Then proceed as indicated in 8.3. Elimination of the opalescence: if any colloid substance is present,
35、difficulties might arise during filtering. The solution intended for analysis is in that case prepared as follows: dissolve the sample for analysis in 150 ml of water, add 2 ml of 1 mol/l hydrochloric acid and filter the solution through two flat very fine filters into a graduated 250 ml flask. Wash
36、 the filters with water and make up to volume. Continue the process according to the method as described in 8.3. 8.3 Determination According to the presumed biuret content, transfer 25 ml or 50 ml from the solution mentioned in 8.2 with a pipette, place this quantity in a 100 ml graduated flask and
37、neutralize if necessary with sulfuric acid solution or sodium hydroxide solution (5.3 or 5.4) as required, using methyl red as an indicator and add, with the same accuracy as that used when drawing up a calibration curve, 20 ml of the alkaline solution of potassium sodium tartrate (5.5) and 20 ml of
38、 the copper solution (5.6). Make up to volume, mix thoroughly and leave standing for 15 min at (30 2) C. Then carry out the photometric measurements and calculate the quantity of biuret present in the urea. 9 Calculation and expression of the result Calculate the mass concentration, ?B, of biuret in
39、 percent of the sample according to the following equation: V m5 , 2 B =(6) where m is the mass, in milligrams, of biuret, read from the calibration graph; V is the volume of the aliquot in millilitre. 10 Precision 10.1 Inter-laboratory test An inter-laboratory test was carried out in 2004 with 13 p
40、articipating laboratories and two different samples. This test yielded the data given in Annex A. Repeatability and reproducibility were calculated according to ISO 5725-1. The values derived from this inter-laboratory test might not be applicable to concentration ranges and matrices other than thos
41、e given in Annex A. ? BS EN 15479:2009 EN 15479:2009 (E) 8 10.2 Repeatability The absolute difference between two independent single test results, obtained with the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval of
42、time, will in not more than 5 % of the cases exceed the values of r given in Table 1. 10.3 Reproducibility The absolute difference between two single test results, obtained with the same method on identical test material in different laboratories by different operators using different equipment, wil
43、l in not more than 5 % of the cases exceed the values of R given in Table 1. Table 1 Mean values, repeatability and reproducibility limits Sample x % r % R % Urea 0,81 0,04 0,20 Urea + S 0,76 0,05 0,38 11 Test report The test report shall contain at least the following information: a) all informatio
44、n necessary for the complete identification of the sample; b) test method used with reference to this document; c) test results obtained expressed as the percentage mass fraction of biuret in the fertilizer; d) date of sampling and sampling procedure (if known); e) date when the analysis was finishe
45、d; f) whether the requirement of the repeatability limit has been fulfilled; g) all operating details not specified in this document, or regarded as optional, together with details of any incidents that occurred when performing the method which might have influenced the test result(s). ? BS EN 15479
46、:2009 EN 15479:2009 (E) 9 Annex A (informative) Results of the inter-laboratory tests The precision of the method was established in 2004 by Working Group 7 “ Chemical analysis” of CEN/TC 260 “ Fertilizers and liming materials” in an inter-laboratory test evaluated in accordance with ISO 5725-1. The statistical results are given in Table A.1. Table A.1 Statistical results of the inter-laboratory test Parameter Sample Ure