BS-EN-15505-2008.pdf

british standard bs en 15505:2008 foodstuffs determination of trace elements determination of sodium and magnesium by flame atomic absorption spectrometry (aas) after microwave digestion ics 67.050 ? copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- bs en 15505:2008 this british standard was published under the authority of the standards policy and strategy committee on 31 march 2008 bsi 2008 isbn 978 0 580 56731 5 national foreword this british standard is the uk implementation of en 15505:2008. the uk participation in its preparation was entrusted to technical committee aw/-/3, food analysis horizontal methods. a list of organizations represented on this committee can be obtained on request to its secretary. this publication does not purport to include all the necessary provisions of a contract. users are responsible for its correct application. compliance with a british standard cannot confer immunity from legal obligations. amendments/corrigenda issued since publication datecomments copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- european standard norme europenne europische norm en 15505 march 2008 ics 67.050 english version foodstuffs - determination of trace elements - determination of sodium and magnesium by flame atomic absorption spectrometry (aas) after microwave digestion produits alimentaires - dosage des lments traces - dosage du sodium et du magnsium par spectromtrie dabsorption atomique de flamme aprs digestion par micro-ondes lebensmittel - bestimmung von elementspuren - bestimmung von natrium und magnesium mit flammen- atomabsorptionsspektrometrie (aas) nach mikrowellenaufschluss this european standard was approved by cen on 7 february 2008. cen members are bound to comply with the cen/cenelec internal regulations which stipulate the conditions for giving this european standard the status 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). 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 republic, 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 normalisation europisches komitee fr normung management centre: rue de stassart, 36 b-1050 brussels 2008 cenall rights of exploitation in any form and by any means reserved worldwide for cen national members. ref. no. en 15505:2008: e copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 2 contents page foreword3 1 scope 4 2 normative references4 3 principle4 4 reagents.4 5 apparatus and equipment 6 6 procedure .6 7 calculation7 8 precision.7 9 test report8 annex a (informative) results of the inter-laboratory tests.9 annex b (informative) additional information on calcium.12 bibliography15 bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 3 foreword this document (en 15505:2008) has been prepared by technical committee cen/tc 275 “food analysis - horizontal methods”, 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 identical text or by endorsement, at the latest by september 2008, and conflicting national standards shall be withdrawn at the latest by september 2008. 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 responsible for identifying any or all such patent rights. according to the cen/cenelec internal regulations, the national 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, poland, portugal, romania, slovakia, slovenia, spain, sweden, switzerland and the united kingdom. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 4 1 scope this document specifies methods for the determination of sodium and magnesium in foodstuffs by flame atomic absorption spectrometry (aas) after microwave digestion. collaborative studies have been carried out (annex a). the method is suitable for the determination of sodium not less than 1 500 mg/kg and magnesium not less than 250 mg/kg. data for calcium is included for information (annex b). the method is not applicable to wheat bran. 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 references, the latest edition of the referenced document (including any amendments) applies. en 13804, foodstuffs determination of trace elements performance criteria, general considerations and sample preparation en 13805, foodstuffs determination of trace elements pressure digestion 3 principle the samples are digested in closed vessels in a microwave oven in a mixture of nitric acid and hydrogen peroxide. the resulting solution is diluted with water, and the sodium and magnesium contents are determined by flame-aas using matrix modifiers. warning the use of this standard may involve hazardous materials, operations and equipment. this standard does not purport to address all the safety problems associated with its use. it is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 4 reagents 4.1 general use only reagents and water, which shall have an element level low enough not to affect results. the use of certified stock solutions is advisable. 4.2 nitric acid 4.2.1 nitric acid, not less than 65 % of approximately mass concentration (hno3) = 1,4 g/ml. in case of insufficient purity, it is necessary to purify the nitric acid in a distillation apparatus as described in en 13805. 4.2.2 diluted nitric acid solution 1, mass fraction w = 2,7 % dilute 42 ml nitric acid (4.2.1) to 1 000 ml with water. 4.2.3 diluted nitric acid solution 2, mass fraction w = 0,65 % mix nitric acid (4.2.1) and water in a proportion minimum of 1 + 99 parts by volume. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 5 4.3 hydrochloric acid, mass fraction w = 37 % 4.4 hydrogen peroxide, mass fraction w = 30 % 4.5 cesium chloride solution (cscl), for use in aas analysis dissolve 31,75 g of cesium chloride in water and dilute to 250 ml. the solution will be stable in a refrigerator for at least 6 months. 4.6 lanthanum(iii)oxide (la2o3) solution, for use in aas analysis, 5 % (weight/volume) weigh 14,66 g of lanthanum(iii)oxide into a 250 ml beaker, moisten with 10 ml of water and add 62,5 ml of hcl (4.3). transfer to a 250 ml volumetric flask and fill up with water. the solution will be stable in a refrigerator for one month. 4.7 sodium solution 4.7.1 sodium stock solution, mass concentration (na) = 1 000 mg/l 4.7.2 sodium standard solution, mass concentration (na) = 10 mg/l dilute 1 ml of sodium stock solution (4.7.1) to 100 ml in a volumetric flask with 2,7 % nitric acid (4.2.2). the solution will remain stable for one month at room temperature. 4.8 magnesium solution 4.8.1 magnesium stock solution, mass concentration (mg) = 1 000 mg/l 4.8.2 magnesium standard solution, mass concentration (mg) = 10 mg/l dilute 1 ml of magnesium stock solution (4.8.1) to 100 ml in a volumetric flask with 0,65 % nitric acid (4.2.3). the solution will remain stable for one month at room temperature. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 6 5 apparatus and equipment 5.1 general all glassware and plastic ware should be carefully cleaned and rinsed according to the procedure in en 13804. 5.2 laboratory microwave oven check the microwave oven for delivered power according to the procedure in en 13804. 5.3 atomic absorption spectrometer 5.4 element specific lamps for sodium and magnesium element specific lamps with wavelength of 589,0 nm and 285,2 nm respectively will apply. 5.5 acetylene use acetylene of appropriate quality. 5.6 air 6 procedure 6.1 pre-treatment homogenise the sample in accordance with the recommendations in en 13804. if necessary, dry the sample in a way that does not affect the element contents, e.g. by freeze drying. 6.2 sample preparation use the test solution obtained by microwave oven digestion method according to en 13805 for the determination of sodium and magnesium. 6.3 dilution pipette a suitable volume of the sample solution, add 5 % la-solution (4.6) and dilute this volume with 0,65 % nitric acid (4.2.3) so that the final concentration of mg is within the linear range of measurement of the elements. in this example, the following ranges are selected for the standard curves; for mg, 0,05 mg/l to 0,4 mg/l. the lowest point may be lower, if required by the concentrations of the sample solutions. add 5 % of la-solution (4.6) to a final mass fraction of la of 1 % (e.g. 2 ml 5 % is diluted to 10 ml). pipette a suitable volume of the sample solution, add 1 ml of cs-solution (4.5) and dilute this volume with 2,7 % nitric acid (4.2.2) so that the final concentration of na is within the range of measurement of the element. in this example, the following range is selected for the standard curve: 0,1 mg/l to 1,0 mg/l. the lowest point may be lower required by concentration of the sample solution. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 7 6.4 preparation of standard solution prepare working standard solutions for na of 0,1 mg/l, 0,25 mg/l, 0,5 mg/l, 0,75 mg/l and 1,0 mg/l from the na standard solution (4.7.2). add 0,5 ml, 1,25 ml, 2,5 ml, 3,75 ml and 5 ml to separate 50 ml volumetric flasks, add 1 ml of cs-solution (4.5) and dilute to the mark with diluted nitric acid solution 1 (4.2.2). prepare fresh solution daily. prepare working standard solutions for mg of 0,05 mg/l, 0,1 mg/l, 0,2 mg/l and 0,4 mg/l from the mg standard solution (4.8.2). add 0,25 ml, 0,5 ml, 1,0 ml and 2,0 ml to separate 50 ml volumetric flasks, add 10 ml of 5 % la-solution (4.6) and dilute to the mark with diluted nitric acid solution 2 (4.2.3). prepare fresh solutions daily. 6.5 settings for the atomic absorption spectrometer before every determination, adjust the instrument as specified in the manufacturers operating manual. example of instrument parameters for sodium and magnesium may be 589,0 nm and 285,2 nm (wavelength) and 0,2 nm and 0,7 nm (slit), respectively. 7 calculation calculate the element content, w, as mass fraction of sodium and magnesium in milligram per kilogram of the sample, using the following equation: m fva w = (1) where a is the content of the element in the test solution, in milligram per litre; v is the volume of the digestion solution after being made up, in millilitres; f is the dilution factor of the test solution; m is the initial sample mass, in grams. if necessary, subtract the concentration in the blank solution from the concentration of the sample solution, before the calculation is made. 8 precision 8.1 general details of an inter-laboratory trial on the precision of the method are summarized in annex a. the values derived from this inter-laboratory test may not be applicable to concentration ranges and matrices other than those given. 8.2 repeatability and reproducibility repeatability is the absolute difference between two independent single test results (blind duplicate), 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. this will in not more than 5 % of the cases exceed the values of r given in table 1 to table 2. reproducibility is 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. this will in not more than 5 % of the cases exceed the values of r given in table 1 to table 2. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 8 table 1 mean values, repeatability limits and reproducibility limits for sodium sample x mg/kg r mg/kg r mg/kg broccoli 2 290 210 320 carrot 3 540 330 420 white bread 8 260 570 1 040 saithe fillet 2 030 210 350 pork 1 480 77 280 cheese 5 380 980 1 040 table 2 mean values, repeatability limits and reproducibility limits for magnesium sample x mg/kg r mg/kg r mg/kg simulated diet (d) 665 70 129 simulated diet (f) 618 76 120 milk powder, freeze dried 859 51 111 minced fish, freeze dried 749 50 144 apple, dried 251 15 32 chocolate cake, dried 284 16 32 9 test report the test report shall specify: a) all information necessary for the complete identification of the sample; b) test method used, with reference to this document; c) test results obtained and the units in which they are specified; d) date when the analysis was finished; e) whether the requirement of the repeatability limit has been fulfilled; f) all operating details not specified in this document or regarded as optional, together with details of any incidents occurred when performing the method which may have influenced the test results. bs en 15505:2008 copyright british standards institution provided by ihs under license with bsi - uncontrolled copy licensee=boeing co/5910770001 not for resale, 08/14/2008 20:59:48 mdtno reproduction or networking permitted without license from ihs -,-,- en 15505:2008 (e) 9 annex a (informative) results of the inter-laboratory tests the precision of the method was established by the nordic committee on food analysis (nmkl) in inter- laboratory tests evaluated in accordance with 1. the test for sodium was carried out in 2003 and the test for magnesium was carried out in 1995. the results are given in table a.1 to table a.3. nine laboratories participated in an inter-laboratory method-performance (collaborative) study of a method for the determination of sodium in foodstuffs by flame atomic absorption spectrometry (aas) after wet digestion using a microwave oven technique 2. the method was tested on a total of six materials (broccoli, carrot, bread, saithe fillet, pork and cheese) ranging in sodium content from 1 480 mg/kg to 8 260 mg/kg. the materials were presented to the participants in the study as blind duplicates and the participants carried out single determinations on each sample. the highest rsdr value was found for sample of cheese, the only wet sample in the study. table a.1 statistical results for sodium in the freeze dried test samples sample parameter broccolicarrot white bread saithe fillet pork cheese* number of laboratories 9 9 9 9 9 9 number of laboratories after elimination of outliers 9 9 9 9 8 7 number of outliers 0 0 0 0 1 2 mean value x (mg/kg) 2 290 3 540 8 260 2 030 1 4805 380 repeatability standard deviation sr (mg/kg) 70 120 200 80 30 350 relative standard deviation of repeatability rsdr (%) 3,3 3,3 2,5 3,8 1,9 6,5 repeatability limit r (mg/kg) 2