EN 15479-2009 en Fertilizers - Spectrophotometric determination of biuret in urea《肥料 尿素中缩二脲的分光光度测定》.pdf

1、BS EN 15479:2009ICS 65.080NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDFertilizers Spectrophotometricdetermination of biuretin ureaThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 28 February2009 BSI 2009IS

2、BN 978 0 580 62385 1Amendments/corrigenda issued since publicationDate CommentsBS EN 15479:2009National forewordThis British Standard is the UK implementation of EN 15479:2009. Itsupersedes DD CEN/TS 15479:2006 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalComm

3、ittee CII/37, Fertilisers and related chemicals.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a

4、 British Standard cannot confer immunityfrom legal obligations.BS EN 15479:2009EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 15479January 2009ICS 65.080 Supersedes CEN/TS 15479:2006 English VersionFertilizers - Spectrophotometric determination of biuret in ureaEngrais - Dtermination photomtrique

5、 du biuret danslureDngemittel - Spektrometrische Bestimmung von Biuret inHarnstoffThis 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 EuropeanStandard the status of a n

6、ational standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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). A version in

7、 any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Es

8、tonia, 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 STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPIS

9、CHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 15479:2009: EBS EN 15479:2009EN 15479:2009 (E) 2 Contents Page Foreword 3 1 Scope 4 2 Normative refere

10、nces 4 3 Terms and definitions .4 4 Principle 4 5 Reagents .4 6 Apparatus .5 7 Sampling and sample preparation .6 8 Procedure .6 9 Calculation and expression of the result 7 10 Precision .7 11 Test report 8 Annex A (informative) Results of the inter-laboratory tests .9 Bibliography . 10 BS EN 15479:

11、2009EN 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 publication of an identic

12、al 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 not be held responsi

13、ble 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 national standards or

14、ganizations 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, Poland, Portugal,

15、 Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 15479:2009EN 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 Normative references The foll

16、owing 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 materials Sampling and

17、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 3696:1995, Water for analyt

18、ical 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 tartrate, biuret and bival

19、ent 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 according to EN ISO 3696:1

20、995). 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 one-litre flask, dissol

21、ve 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 15479:2009EN 15479:2009 (E) 5 5.6 Solution of copper sulfate In a graduated one-litre flask dissolve 15 g of copp

22、er 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 biuret1in water. Make up to 250 ml. 1 ml of this solution contains 0,001 g of biuret. 5.8 Indicator solution In a graduated 100 ml flask

23、, 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 precision to permit measures o

24、f less than 0,5 % factor of transmission to be produced. The factor of transmission, T, is given by the following equation: JoJT = (1) The opacity, O, is given by the following equation: JJoO = (2) The absorbance, E, is given by the following equation: OE log= (3) The absorbance per unit of optical

25、run, k, is given by the following equation: sEk = (4) The coefficient of specific absorbance, K, is given by the following equation: sEK=(5) where Jo is the intensity of the beam of monochromatic rays (of a determinate wavelength) before it passes through a transparent body; J is the intensity of th

26、is beam after the passage; 1Biuret can be purified beforehand by washing with an ammoniacal solution (10 %), then with acetone and dried in a vacuum. BS EN 15479:2009EN 15479:2009 (E) 6 s is the thickness of the layer in centimetres; is the mass concentration in milligrams per litre; k is the specif

27、ic 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 ml. 6.5 Glass column for cation excha

28、nge 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 using the column, the resin has first

29、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 resin has to be great enough to be su

30、re 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 in EN 1482-1. Sample preparation sha

31、ll 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 volumes to about 50 ml with water, add

32、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 better still with pipettes. Make up t

33、o 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 using the absorbance rate as the ordinat

34、e and the corresponding quantities of biuret, in milligrams, as the abscissa. BS EN 15479:2009EN 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 250 ml graduated flask, and make up to t

35、he 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 fibre filter and wash the filter with ap

36、proximately 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. Collect the eluate in a 250 ml volumetr

37、ic 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, difficulties might arise during filterin

38、g. 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 the filters with water and make up to v

39、olume. 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 neutralize if necessary with sulfuric ac

40、id 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 the copper solution (5.6). Make up to v

41、olume, 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 percent of the sample according to the f

42、ollowing equation: Vm 5,2B= (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 participating laboratories and two different

43、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 those given in Annex A. BS EN 15479:2009EN 15479

44、: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 time, will in not more than 5 % of the cases ex

45、ceed 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, will in not more than 5 % of the cases exceed the

46、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 information necessary for the complete identification of

47、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 finished; f) whether the requirement of the repeatabil

48、ity 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 15479:2009EN 15479:2009 (E) 9 Annex A (informative) Re

49、sults 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 Urea Urea + S Number of participating laboratories 13 9 Number of laboratories after elimination of outliers (accepted test results) 11 6 Mean value x (%) 0,81 0,76 Repeatabil