ISO 15598-1999 Tea - Determination of crude fibre content《茶叶 粗纤维含量的测定》.pdf

1、A Referencenumbe r ISO15598:1999 (E) INTERNATIONAL STANDARD ISO 15598 Firstedition 19990601 TeaDeterminationofcrudefibrecontent ThDterminationdelindicedinsolubleditcellulosiqueISO15598:1999(E) ISO1999 Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyfor

2、morbyan ymeans,electronic ormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromthepublisher. InternationalOrganizationforStandardization Casepostale56 CH1211Genve20 Switzerland Internet isoiso.ch PrintedinSwitzerland ii Foreword ISO(theInternationalOrganizationforStandardizat

3、ion)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorga

4、nizations,governmentalandnongovernmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3. DraftIn

5、ternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. InternationalStandardISO15598waspreparedbyTechnicalCommitteeISO/TC34, Agriculturalfoodproducts, SubcommitteeSC8,

6、Tea. AnnexAofthisInternationalStandardisforinformationonly.INTERNATIONALSTANDARD ISO ISO15598:1999(E) 1 TeaDeterminationofcrudefibrecontent 1Scope ThisInternationalStandardspecifiesamethodforthedeterminationofcrudefibrecontentintea. 2Normative references Thefollowingnormativedocumentscontainprovisio

7、nswhich,throughreferenceinthistext,constituteprovisionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedto investigatethepossibilityofapplyingthemostrecentedi

8、tionsofthenormativedocumentsindicatedbelow.For undatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidInternationalStandards. ISO1573:1980, TeaDeterminationoflossinmassat103 C. ISO3696, WaterforanalyticallaboratoryuseSpecificatio

9、nandtestmethods . 3 Termanddefinition ForthepurposesofthisInternationalStandard,thefollowingtermanddefinitionapply. 3.1 crudefibrecontent thewholeofthesubstanceswhichareinsolubleandcombustibleundertheoperatingconditionsspecifiedinthis InternationalStandard NOTE Itisexpressedasamassfraction,inpercent

10、oftheproductonadrybasisformerlyexpressedas%( m/m). 4Principle Thesuitablygroundsampleissuccessivelytreatedwithboilingsulfuricacidsolutionandsodiumhydroxidesolution. Theresidueisseparatedbyfiltration,washed,dried,weighedandthenashed.Thelossinmassresultingfrom ashingiscalledthecrudefibrecontent. 5Rea

11、gents Useonlyreagentsofrecognizedanalyticalgrade. 5.1 Water,complyingwithgrade3ofISO3696. 5.2 Sulfuricacidstocksolution , c(H 2 SO 4 )=2,040 0,040mol/l(correspondingto100gofsulfuricacidper litreofsolution).ISO15598:1999(E) ISO 2 Add275mlofconcentratedsulfuricacid( r 20 =1,84g/ml)towater,coolanddilut

12、eto5l. CAUTIONWearglovesandfaceprotection. 5.3 Sulfuricacidworkingsolution , c(H 2 SO 4 )=0,255 0,005mol/l(correspondingto12,5gofsulfuricacidper litreofsolution). Dilute125mlofthesulfuricacidstocksolution(5.2)to1l. 5.4 Sodiumhydroxidestocksolution,c(NaOH)=2,504 0,040 mol/l(correspondingto100 gofsodi

13、um hydroxideperlitreofsolution). Dissolve500gofsodiumhydroxideinwater,coolanddiluteto5l. CAUTIONWearglovesandfaceprotection. 5.5 Sodiumhydroxideworkingsolution ,c(NaOH)=0,313 0,005mol/l(correspondingto12,5gofsodium hydroxideperlitreofsolution). Dilute125mlofthesodiumhydroxidestocksolution(5.4)to1l.

14、5.6 Octan1ol ,asantifoamingagent. 5.7 Hydrochloricacid ,1%solution(volumefraction). Dilute10mlofconcentratedhydrochloricacid( r 20 =1,19g/ml)to1l. CAUTIONWearglovesandfaceprotection. 5.8 Ethanol,ofminimumpurity95%(volumefraction). 5.9 Acetone. 6Apparatus Usuallaboratoryapparatusand,inparticular,thef

15、ollowing. 6.1 Laboratorymill ,ofhammerorcentrifugaltype,fittedwitha1mmscreen. 6.2 Conicalflasks ,of1lcapacity,withplainneck(orgroundglassneckifrefluxcondensersaretobeused). 6.3 Dispenser,capableofdispensing200mlofhotliquid. 6.4 Heatingunit ,equippedforheatingabankof1lconicalflasks. 6.5 Coldfingercon

16、densers ,tofitintothenecksof1lconicalflasks(orrefluxcondensersifapparatuswith groundglassjointsisbeingused). 6.6 Buchnerflasks,withrubberadaptorsandfittedwithHartleyfunnelsfor12,5cmdiameterfilterpaper,plus adaptorfunnelsfor70mlsinteredglasscrucibles. 6.7 Sinteredglasscrucibles ,ofporosityNo.1orP160(

17、poresize100mto160m),of40mmplatediameter and70mlcapacity. 6.8 Oven,fanassisted,capableofmaintainingatemperatureof103C 2C.ISO ISO15598:1999(E) 3 6.9 Mufflefurnace ,capableofmaintainingatemperatureof550C 10C. 6.10 Desiccator,containinganefficientdesiccant. 6.11 Filterpapers ,of12,5cmdiameter,hardened,a

18、shlessgrade,withaporosityof20mto25m. NOTE WhatmanNo.541 1) havebeenfoundtobesuitable. 7Sampling Itisimportantthatthelaboratoryreceiveasamplewhichistrulyrepresentativeandhasnotbeendamagedor changedduringtransportandstorage. SamplingisnotpartofthemethodspecifiedinthisInternationalStandard.Arecommended

19、samplingmethodis giveninISO1839. 8 Preparationoftestsample Usingthemill(6.1),grindthesampletopassthroughthe1mmscreen. 9Procedure NOTE Ifitisrequiredtocheckwhethertherepeatabilitylimit(11.2)ismet,carryouttwosingledeterminationsin accordancewith9.1to9.3underrepeatabilityconditions. 9.1 Determinationof

20、drymattercontent Calculatethedrymattercontent( w)fromthemoisturecontent(lossinmassat103C)determinedonaportionof thetestsample(clause8)inaccordancewithISO1573. 9.2Test portion Weigh,tothenearest0,001g,2gto3gofthetestsample(clause8)intoa1lconicalflask(6.2).Recordthemass (m 0 ). 9.3Determination 9.3.1

21、Usingthedispenser(6.3),addtothesample200mlofthesulfuricacidworkingsolution(5.3),measuredat roomtemperatureandbroughttoboiling. CAUTIONTakecaretoavoidsplashingtheboilingacid.Wearglovesandfaceprotection. 9.3.2 Addtwoorthreedropsoftheantifoamingagent(5.6),insertthecondenser(6.5)intotheneckoftheflask, a

22、ndheatusingtheheatingunit(6.4)toboilingwithin2min.Continueboilinggentlyfor30min,rotatingtheflask occasionallytomixthecontentsandtoremoveparticlesofthesampleadheringtothesides. Thetimesgivenarecritical. 9.3.3 PrepareaBuchnerflask(6.6)withaHartleyfunnelwithawetfilterpaper(6.11). 9.3.4 Attheendoftheboi

23、lingperiod,pourtheaciddigestintoashallowlayerofhotwatercontainedinthefunnel undergentlesuction. Filtrationshouldbecompletedwithin10min.Ifitisnot,repeatthedeterminationusingasmallermassofsample. 1)WhatmanNo.541isanexampleofasuitableproductavailablecommercially.Thisinformationisgivenfortheconvenience

24、ofusersofthisInternationalStandardanddoesnotconstituteanendorsementbyISOofthisproduct.ISO15598:1999(E) ISO 4 9.3.5 Rinseouttheflaskwithtwoportionsofapproximately50mlofboilingwater,andpourthroughthefilter funnel. 9.3.6 Usingthedispenser(6.3),washtheinsolublematterfromthefilterpaperintotheoriginal1lco

25、nicalflask using200mloftheworkingsodiumhydroxidesolution(5.5),measuredatroomtemperatureandbroughttoboiling. CAUTIONTakecaretoavoidsplashingtheboilingalkali.Wearglovesandfaceprotection. 9.3.7 Addtwoorthreedropsoftheantifoamingagent(5.6)andboilfor30minusingthesameprocedureaswith theacidtreatment(see9.

26、3.2). Thetimesgivenarecritical. 9.3.8 Usingboilingwater,transferalltheinsolublematterintothesinteredglasscrucible(6.7)fittedtotheBuchner flaskbymeansofanadaptor,applyinggentlesuction. 9.3.9 Washtheresiduesuccessivelywithapproximately50mlportionsofboilingwater,thehydrochloricacid solution(5.6)andboil

27、ingwateragain.Finally,washtheresiduetwicewiththeethanol(5.7)andthenthreetimes withtheacetone(5.8). 9.3.10 Heatthecrucibleandresidueintheoven(6.8)maintainedat103Cfor2h.Allowtocoolinthedesiccator (6.10)andweightothenearest0,001g.Returnthecrucibletotheovenandheatagainfor1h.Coolinthe desiccatorandweigh.

28、Repeattheseoperationsuntilthedifferencebetweensuccessiveweighingsdoesnotexceed 0,001g. NOTE Itisanacceptablealternative,anditmaybemoreconvenient,toheatthecrucibleandresidueovernight. Recordthemass( m 1 ). 9.3.11 Placethecrucibleandresidueinthemufflefurnace(6.9)maintainedat550Cforatleast1h.Allowtocoo

29、l inthedesiccator(6.10)andweightothenearest0,001g.Recordthemass( m 2 ). 10Calculation Thecrudefibrecontent, w,expressedasmassfraction,inpercent,ofthesampleonadrybasis,isgivenbythe formula: w mm mw = - 12 0 100 100 D where m 0 isthemass,ingrams,ofthetestportion; m 1 isthemass,ingrams,ofthecrucibleand

30、residueafterdrying(9.3.10); m 2 isthemass,ingrams,ofthecrucibleandresidueafterheatinginthefurnace(9.3.11); w D isthedrymattercontent,expressedasamassfraction,inpercent,ofthetestsample(9.1). 11Precision 11.1Interlaboratory test Detailsoftheinterlaboratorytesttodeterminetheprecisionofthemethodaresumma

31、rizedinannexA.Thevalues derivedfromthisinterlaboratorytestmaynotbeapplicabletoconcentrationrangesandmatricesotherthanthose given.ISO ISO15598:1999(E) 5 11.2Repeatability Theabsolutedifferencebetweentwoindependentsingletestresults,obtainedusingthesamemethodonidentical testmaterialinthesamelaboratoryb

32、ythesameoperatorusingthesameequipmentwithinashortintervaloftime, willinnotmorethan5%ofcasesbegreaterthantherepeatability( r)valuesgiveninTableA.1. 11.3Reproducibility Theabsolutedifferencebetweentwosingletestresults,obtainedusingthesamemethodonidenticaltestmaterial indifferentlaboratorieswithdiffere

33、ntoperatorsusingdifferentequipment,willinnotmorethan5%ofcasesbe greaterthanthereproducibility( R)valuesgiveninTableA.1. 12Test report Thetestreportshallspecify: allinformationnecessaryforthecompleteidentificationofthesample; thesamplingmethodused,ifknown; thetestmethodused,withreferencetothisInterna

34、tionalStandard; alloperatingdetailsnotspecifiedinthisInternationalStandard,orregardedasoptional,togetherwithdetailsof anyincidentswhichmayhaveinfluencedthetestresult(s); thetestresult(s)obtained,or,iftherepeatabilityhasbeenchecked,thefinalquotedresultobtained.ISO15598:1999(E) ISO 6 AnnexA (informati

35、ve) Resultsofinterlaboratorytest Aninterlaboratorytest,carriedoutin1994undertheauspicesoftheInternationalOrganizationforStandardization, gavethestatisticalresults(evaluatedinaccordancewithISO5725 2) )showninTableA.1. TableA.1Repeatabilityandreproducibilityvalues Blacktea Sampleidentification 12345 N

36、umberofparticipatinglaboratories 11 11 11 11 11 Numberofacceptedtestresults 11 11 11 11 11 Meancrudefibrecontent,%,drymatter 28,63 9,67 18,95 22,85 9,35 Repeatabilitystandarddeviation, s r 0,4338 0,2341 0,2728 0,2143 0,1537 Repeatabilitycoefficientofvariation,% 1,50 2,42 1,44 0,94 1,64 Repeatability

37、limit, r (2,8 s r ) 1,2146 0,6555 0,7638 0,5999 0,4305 Reproducibilitystandarddeviation, s R 1,1032 0,6746 1,2354 1,1855 0,5401 Reproducibilitycoefficientofvariation,% 3,85 6,98 6,52 5,19 5,77 Reproducibilitylimit, R(2,8 s R ) 3,0890 1,8888 3,4591 3,3195 1,5123 2) ISO5725:1986(nowwithdrawn)wasusedtoobtaintheprecisiondata.ISO ISO15598:1999(E) 7 Bibliography 1ISO 1839:1980, TeaSampling . 2ISO 5725:1986, PrecisionoftestmethodsDeterminationofrepeatabilityandreproducibilityforastandard testmethodbyinterlaboratorytests.ISO15598:1999(E) ISO ICS67.140.10 Pricebasedon7pages