BS 5766-19-2000 Methods for analysis of animal feeding stuffs Determination of starch content Polarimetric method《动物饲料的分析方法 淀粉含量的测定 旋光测定法》.pdf

1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 5766-19:2000 ISO 6493:

2、2000 ICS 65.120 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods for analysis of animal feeding stuffs Part 19: Determination of starch content Polarimetric methodThis British Standard, having been prepared under the direction of the Consumer Products and Services Secto

3、r Committee, was published under the authority of the Standards Committee and comes into effect on 15 April 2000 BSI 04-2000 ISBN 0 580 34737 0 BS 5766-19:2000 Amendments issued since publication Amd. No. Date Comments National foreword This British Standard reproduces verbatim ISO 6493:2000 and imp

4、lements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/10, Animal feeding stuffs, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the i

5、nterpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards

6、 which implement international publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purpo

7、rt to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front co

8、ver, the ISO title page, pages ii and iii, a blank page, pages 1 to 10, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.Referencenumber ISO6493:2000(E) INTERNATIONAL STANDARD ISO 6493 Firstedition 2000-02-01 Anima

9、lfeedingstuffsDeterminationof starchcontentPolarimetricmethod Aliments des animaux Dtermination de la teneur en amidon Mthode polarimtriqueISO6493:2000(E) ii ISO6493:2000(E)iii Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodie

10、s).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,in liaisonwithISO,alsotak

11、epartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedto

12、thememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. AttentionisdrawntothepossibilitythatsomeoftheelementsofthisInternationalStandardmaybethesubjectof patentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.

13、InternationalStandardISO6493waspreparedbyTechnicalCommitteeISO/TC34, Agricultural food products, SubcommitteeSC10, Animal feeding stuffs. AnnexesAandBofthisInternationalStandardareforinformationonly.INTERNATIONALSTANDARD ISO6493:2000(E)1 AnimalfeedingstuffsDeterminationofstarchcontent Polarimetricme

14、thod 1 Scope ThisInternationalStandardspecifiesamethodforthepolarimetricdeterminationofthestarchcontentofanimal feedingstuffsandrawmaterialsforanimalfeedingstuffs. Themethodisnotapplicabletoproductswhich,besidesstarch,containothersubstanceswhichareopticallyactive duringtheanalysisanddonotdissolvein4

15、0%ethanol.Examplesoftheseproductsarepotatopulp,beetchips, beetleaves,beettops,yeast,soyaproducts,lupineandproductsrichininulin(e.g.chicoryrootsandJerusalem artichokes).Inthesecasesanenzymaticdeterminationofthestarchcontentmaybeused. Thismethodisnotapplicableforthequantificationofstarchwithanamylosec

16、ontentexceeding40%(e.g.high amylosemaizestarchlikeHylonVII). CAUTIONDependingontheintensityoftheheat/moisturetreatmenttheproducthasbeensubjectedto, toolowastarchcontentmaybedetermined. 2 Normativereferences Thefollowingnormativedocumentscontainprovisionswhich,throughreferenceinthistext,constitutepro

17、visionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedto investigatethepossibilityofapplyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.For u

18、ndatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidInternationalStandards. ISO3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. ISO3696, Water for analytical laboratory use Specifi

19、cation and test methods. ISO6498, Animal feeding stuffs Preparation of test samples. 3 Termsanddefinitions ForthepurposesofthisInternationalStandard,thefollowingtermsanddefinitionsapply. 3.1 starch naturalvegetablepolymerconsistingoflongunbranchedchainsof -1,4-linkedglucose-units(amylose)and/or long

20、 -1,6-branchedchainsof -1,4-linkedglucose-units(amylopectine)ISO6493:2000(E) 2 3.2 starchcontent massfractionofstarchanditshighmolecularmassbreakdownproducts,insolublein40%ethanol,and determinedinaccordancewiththisInternationalStandard NOTE Thestarchcontentisexpressedingramsperkilogram. 4Principle A

21、testportionisdecomposedwithdilutehydrochloricacid,thenthesolubilizedstarchisgelatinizedandpartially hydrolysed. Thetotalopticalrotationoftheclarifiedsolutionisdetermined. Correctionismadefortheopticalrotationcausedbyothersubstanceswhicharesolublein40%ethanoland opticallyactiveaftertreatmentwithdilut

22、ehydrochloricacid. Thestarchcontentiscalculatedbymultiplyingthecorrectedopticalrotationbyaknownfactor. 5 Reagents Useonlyreagentsofrecognizedanalyticalgrade. 5.1Water,complyingwithatleastgrade3inaccordancewithISO3696. 5.2Ethanol(C 2 H 5 OH),40%volumefraction. 5.3Methylred,solutioninethanol(96%volume

23、fraction), (methylred)=1g/l. 5.4Hydrochloricacid,c(HCl)=0,31mol/l. Checktheconcentrationbytitrationwitha0,100mol/lsodiumhydroxidesolutionusingmethylredasindicator.An aliquotportionof10mlofhydrochloricacidshallneutralize(31,0 0,1)mlofthesodiumhydroxidesolution. CAUTIONToohighortoolowahydrochloricacid

24、concentrationwillleadtoincorrectvaluesofthe determinedstarchcontent. 5.5Hydrochloricacid,c(HCl)=7,73mol/l. 5.6Clarifyingsolutions,accordingtoCarrez,asfollows. 5.6.1Potassiumhexacyanoiron(II)solution,cK 4 Fe(CN) 6 =0,25mol/l. Ina1lvolumetricflask,dissolve106gofpotassiumhexacyanoiron(II)trihydrateK 4

25、Fe(CN) 6 3H 2 Oinwater.Dilute tothemarkwithwater. 5.6.2Zincacetate,solutionin0,5mol/laceticacid,cZn(CH 3 CO 2 ) 2 =1mol/l. Ina1lvolumetricflaskdissolve219,5gofzincacetatedihydrateZn(CH 3 CO 2 ) 2 2H 2 Oand30gofglacialacetic acidinwater.Dilutetothemarkwithwater. 5.7Saccharosesolution, (C 12 H 22 O 11

26、 )=100,0g/l.ISO6493:2000(E)3 6 Apparatus Usuallaboratoryapparatusand,inparticular,thefollowing. 6.1Analyticalbalance,capableofweighingtothenearest1mg. 6.2pH-meter,capableofmeasuringtothenearest0,1pHunit. 6.3Boilingwaterbath,withsufficientcapacitytomaintainthewateratboilingpointwhileimmersingtheconic

27、al flasks. CAUTIONIfthewaterbathisnotboilingconstantly,toohighastarchcontentwillbedetermined. 6.4Polarimeter,accuratetoatleast0,01andsuitablefor200mmlongtubes. Measuretheopticalrotationatawavelengthof589,3nm(sodiumDline).Whenusingpolarimetertubesof deviatinglengths,measurewithacorrespondingaccuracy.

28、 Asaccharimetermaybeusedifithasanaccuracyofmeasurementatleastequaltotheaccuracyofthe polarimeter.Inthiscase,convertthereadingstodegrees. Thepolarimetermaybecalibratedwiththesaccharosesolution(5.7).Thissaccharosesolutionyieldsanoptical rotationof13,30whenmeasuredat(20 1) Cusinga200mmpolarimetertube.

29、6.5Burette. 6.6Refluxcondensers. 6.7Volumetricflasks,ofcapacity100ml. Ifthevolumetricflasksneedtobefittedtoarefluxcondenser(see9.3.3),theuseofwide-neckedKohlrausch conicalflasksisrecommended. NOTE Kohlrauschconicalflasksarecommerciallyavailablevolumetricflasksusedforsugardeterminations. 7 Sampling S

30、amplingisnotpartofthemethodspecifiedinthisInternationalStandard.Arecommendedsamplingmethodis giveninISO64971. Itisimportantthatthelaboratoryreceiveasamplewhichistrulyrepresentativeandhasnotbeendamagedor changedduringtransportorstorage. 8 Preparationoftestsample PreparethetestsampleinaccordancewithIS

31、O6498. Ifsolid,grindthelaboratorysample(usually500g)sothatitpassescompletelythroughasievewith0,5mm aperturescomplyingwithISO3310-1.Mixthoroughly.ISO6493:2000(E) 4 9 Procedure 9.1Determinationofacidconsumption 9.1.1Weighapproximately2,5gofthepreparedtestsampletothenearest1mgandtransferitquantitativel

32、ytoa 50mlconicalflask.Add25mlofwaterandshakeuntilahomogeneoussuspensionisobtained. 9.1.2PlacetheelectrodesofthepH-meter(6.2)inthesuspensionand,usingaburette,addhydrochloricacid (5.4)untilthepHofthesuspensionis3,0 0,1.Checkwhetherthecompleteacidconsumptionofthetestportion hasbeencompensatedfor,byshak

33、ingthesuspensionvigorouslyandallowingittostandfor2min.Ifduringthis periodthepHhasincreaseduptoavalueexceeding3,1,addmorehydrochloricacid(5.4),usingtheburette,as manytimesasnecessaryuntilnomoreacidisconsumed. 9.1.3Calculatetheacidconsumptionofthetestportionfromthevolumeofhydrochloricacid(5.4)added. 9

34、.2Determinationoftotalopticalrotation 9.2.1Weighapproximately2,5gofthepreparedtestsample(m 1 )tothenearest1mgandtransferitquantitatively toadry100mlvolumetricflask(6.7).Add25mlofhydrochloricacid(5.4).Shakeuntilahomogeneoussuspension isobtained,thenaddafurther25mlofhydrochloricacid(5.4). 9.2.2Compens

35、atefortheacidconsumptionofthetestportion(see9.1)byaddinghydrochloricacidofasuitable concentrationsothatthevolumeofthecontentsoftheflaskischangedbynotmorethan1ml. EXAMPLESupposethat5,0mlof0,1mol/lhydrochloricacidisusedin9.1.2forcompensationofasamplerichinchalk,then theacidconsumptionofthetestportioni

36、s0,5mmol(9.1.3).Inthatcase,add0,5mlof1,0mol/lhydrochloricacidin9.2.2. CAUTIONIfthehydrochloricacidconcentrationinthesuspensiondeviatesfrom0,31mol/l,awrong starchcontentwillbedetermined.Toohighortoolowahydrochloricacidconcentrationwillresultintoo lowortoohighvalues,respectively,ofthedeterminedstarchc

37、ontent. 9.2.3Immersetheflaskintheboilingwaterbath(6.3).Duringthefirst3min,regularlyshaketheflaskvigorously topreventclottingandtoobtainequalheatdistributioninthesuspension.Whenshaking,keeptheflaskimmersed. Inthecaseofmultipleanalyses,immersetheflasksoversuitabletimeintervalssoastokeepthewaterbathat

38、boilingpoint. After15min 5s,removetheconicalflaskfromthebath.Immediatelyadd30mlofwater(5.1)atatemperature notexceeding10 Candswirl.Cooltoatemperatureofabout20Cinawaterbathwithrunningcoldwater. CAUTIONIftheflaskstaysintheboilingwaterbathtoolongorifthetemperaturedecreaseistooslow, toolowastarchcontent

39、willbedetermined. Add5mlofpotassiumhexacyanoiron(II)solution(5.6.1)andshakefor1min.Add5mlofzincacetatesolution (5.6.2)andshakeagainfor1min.Dilutetothemarkwithwater,mixandfilter.Discardthefirstfewmillilitresofthe filtrate. Determinetheopticalrotationofthefiltrate( 1 )withthepolarimeterorsaccharimeter

40、(6.4). 9.3Determinationofopticalrotationofethanol-solublesubstances 9.3.1Weighapproximately5gofthepreparedtestsample(m 2 )tothenearest1mgandtransferitquantitatively toadry100mlvolumetricflask(6.7).Add40mlofethanol(5.2).Shakeuntilahomogeneoussuspensionis obtainedthenaddafurther40mlofethanol(5.2).ISO6

41、493:2000(E)5 9.3.2Compensatefortheacidconsumptionofthetestportion(see9.1)byaddinghydrochloricacidofasuitable concentrationsothatthevolumeofthecontentsoftheflaskischangedbynotmorethan1ml.Inprinciple,the amountofhydrochloricacidtobeaddedistwiceasmuchasthataddedin9.2.2. 9.3.3Shakevigorouslyandleavetost

42、andfor1hatroomtemperature.Duringthistime,shakevigorouslyatleast every10min. Ifthelactosecontentofthesampleexceeds50g/kg(asforwheypowderandseparatedmilkpowder),dissolvethe samplebyheatingtheflask,fittedwitharefluxcondenser,inawaterbathat(50 2)Cfor30min. Dilutetothemarkwithethanol(5.2),mixandfilter.Di

43、scardthefirstfewmillilitresofthefiltrate. Pipette50mlofthefiltrateintoa100mlvolumetricflask(6.7).Add2,0mlofhydrochloricacid(5.5)andswirl vigorously.Fitarefluxcondensertotheflaskandimmersetheflaskintheboilingwaterbath(6.3). After15min 5s,removetheconicalflaskfromthebath.Immediatelyadd30mlofwater(5.1)

44、atatemperature notexceeding10 Candswirl.Cooltoatemperatureofabout20Cinawaterbathwithrunningcoldwater. Add5mlofpotassiumhexacyanoiron(II)solution(5.6.1)andshakefor1min.Add5mlofzincacetatesolution (5.6.2)andshakeagainfor1min.Dilutetothemarkwithwater,homogenizeandfilter.Discardthefirstfew millilitresof

45、thefiltrate. Determinetheopticalrotationoftheclearfiltrate( 2 )withthepolarimeterorsaccharimeter(6.4). 10Calculationandexpressionofresults Calculatethestarchcontentofthetestsamplebytheequation: w mm L N M O Q P 20000 25 5 20 1 1 2 2 D , where w isthenumericalvalueofthestarchcontentofthetestsample,in

46、gramsperkilogram; 1 isthenumericalvalueofthetotalopticalrotation,indegrees,measuredin9.2; 2 isthenumericalvalueoftheopticalrotation,indegrees,oftheethanol-solublesubstancesmeasuredin 9.3; m 1 isthenumericalvalueofthemass,ingrams,ofthetestportionforthedeterminationofthetotaloptical rotation(9.2); m 2

47、 isthenumericalvalueofthemass,ingrams,ofthetestportionforthedeterminationoftheopticalrotation oftheethanol-solublesubstances(9.3); D 20 isthenumericalvalueofthespecificopticalrotation,indegrees,ofpurestarchmeasuredatawavelength of589,3nm(NaDline): D 20 =185,9 forricestarch; D 20 =185,7 forpotatostar

48、ch(seeannexA); D 20 =184,6 formaizestarch;ISO6493:2000(E) 6 D 20 =184,0 forryestarch; D 20 =183,6 fortapiocastarch(seeannexA); D 20 =182,7 forwheatstarch; D 20 =181,5 forbarleystarch; D 20 =181,3 foroatstarch; D 20 =184,0 forothertypesofstarchandstarchmixturesinanimalfeedingstuffs. Roundtheresulttot

49、henearest1g/kg. 11Precision 11.1Interlaboratorytest DetailsofaninterlaboratorytestontheprecisionofthemethodaregiveninannexB.Thevaluesderivedfromthis testmaynotbeapplicabletoconcentrationrangesandmatricesotherthanthosegiven. 11.2Repeatability Theabsolutedifferencebetweentwoindependentsingletestresults,obtainedusingthesamemethodonidentical testmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinashortintervaloftime, willinnotmorethan5%ofcasesexceedtherepeatabilitylimitrgiven