1、BRITISH STANDARD BS ISO 11021:1999 Essential Oils Determination of water content Karl Fischer method ICS 71.100.60; 71.040.40 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS ISO 11021:1999 This British Standard, having been prepared under the direction of the Consumer Produc
2、ts and Services Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 September 2001 BSI 08-2001 ISBN 0 580 38325 3 National foreword This British Standard reproduces verbatim ISO 11021:1999 and implements it as the UK national standard. The UK pa
3、rticipation in its preparation was entrusted to Technical Committee AW/54, Essential Oils, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or Europ
4、ean 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 purport to include all the neces
5、sary 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. aid enquirers to understand the text; present to the responsible international/European committee any
6、 enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, page ii, pages 1 to
7、 6, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsA Referencenumbe r ISO11021:1999 (E) INTERNATIONAL STANDARD ISO 11021 Firstedition 19991001 Essentialoil
8、sDeterminationofwater contentKarlFischermethod HuilesessentiellesDterminationdelateneureneauMthode deKarlFischerISO11021:1999(E) OSI9991 noitazidradnatSrofnoitazinagrOlanoitanretnI 65elatsopesaC 02evneG1121HC dnalreztiwS tenretnI hc.osiosi dnalreztiwSnidetnirP ii Foreword ISO(theInternationalOrganiz
9、ationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommitt
10、ee.Internationalorganizations,governmentalandnongovernmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirec
11、tives,Part3. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. InternationalStandardISO11021waspreparedbyTechnicalCommitteeISO/TC54, Essentialoils .INTERNAT
12、IONALSTANDARD OSI ISO11021:1999(E) 1 EssentialoilsDeterminationofwatercontent KarlFischermethod 1Scope ThisInternationalStandardspecifiesamethodforthedeterminationofthewatercontentofessentialoilsbytheKarl Fischermethod. 2Normative reference Thefollowingnormativedocumentcontainsprovisionswhich,throug
13、hreferenceinthistext,constituteprovisionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,thispublicationdo notapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedtoinvestigatethe possibilityofapplyingthemostrecenteditionofthenormativedoc
14、umentindicatedbelow.Forundatedreferences, thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIECmaintainregistersof currentlyvalidInternationalStandards. ISO760, DeterminationofwatercontentKarlFischermethod(Generalmethod). 3 Termsanddefinitions ForthepurposesofthisInternationalSt
15、andard,thefollowingtermanddefinitionapply. 3.1 watercontent amountofwaterpresentintheessentialoilconsidered,determinedinaccordancewiththeprocedurespecifiedin thisInternationalStandard NOTE Watercontentisexpressedasamassfractioninpercentformerlydesignatedas%( m/m). 4Principle Thewaterpresentinatestpo
16、rtionisabsorbedwithdriedmethanol.ThewaterisallowedtoreactwiththeKarl Fischerreagentwithoutpyridine,previouslystandardizedbytitrationusingaKarlFischerapparatus.Theendpoint ofthereactionisobtainedbyanelectrometricmethod. 5Reactions DuringthedeterminationofwateraccordingtotheKarlFischermethod,thewaterp
17、resentinthesamplereacts,in thepresenceofanamineandanalcohol,withiodineandsulfurdioxide: H 2 O+I 2 +SO 2 +ROH+ 3R n NH 3n 2R n NH 3n HI+R n NH 3n HSO 4 R where Risanalkyloralkoxylgroup. Theendpointofthereactionisobtainedelectrometricallybyasurplusofiodine.ISO11021:1999(E) OSI 2 6 Reagentsandmaterials
18、 Useonlyreagentsofrecognizedanalyticalqualityanddistilledordemineralizedwaterorwaterofequivalentpurity. 6.1 Methanol, containingnotmorethan0,05%ofwaterbymass.Ifthereagentcontainsmorethanthisquantity ofwater,dryitbydistillationinaninertatmosphere(nitrogen,heliumetc.)withmagnesiumturningsactivatedwith
19、 iodine.Collectthedistillateinaflaskprotectedfromatmosphericmoisturebymeansofaguardtubewitha desiccant.Alternatively,use2methoxyethanol(6.2). 6.2 2Methoxyethanol (ethyleneglycolmonomethyletherormethylcellosolve),containingnotmorethan0,05% ofwaterbymass.Ifthereagentcontainsmorethanthisquantityofwater
20、dryitbydistillation,rejectingthefirstfew millilitresofthedistillatewhichcontainswater. 6.3 KarlFischerreagent , 1) freefrompyridine,havingatitrelowerthan4,0mg/ml;oneortwocomponentsystem. Thetitreshallbedetermineddaily. Ifcarbonylcompoundsarepresent,anadaptedKarlFischerreagentshallbeused. 6.4 Tartar
21、icacid,dipotassiumsalt ( C 4 H 4 O 6 K 2 H 2 O),or water. 7Apparatus SeeISO760. Alltheglasswareusedshallbepreviouslydriedfor30mininanovenmaintainedatapproximately130C,then storedinadesiccatorcontainingadesiccantthenallowedtocooltoroomtemperature. Theautomaticburettesshouldnotbeheatedinanoven.Theysho
22、uldbedriedwithabsoluteethanoloracetoneand adryairstream. Usuallaboratoryapparatusand,inparticular,thefollowing. 7.1 Titrationapparatus ThereiscommerciallyavailableapparatusfortheautomaticdeterminationofthewatercontentaccordingtotheKarl Fischermethod,whichconsistsoftheitemsgivenin7.1.1to7.1.5. 7.1.1
23、Endpointindicator ,fortitrationaccordingtotheelectrometricmethod. 7.1.2 Platinumdoubleelectrode. 7.1.3 Magneticstirrer,fittedwithastirringrodcoveredwithpolytetrafluoroethytlene,operatingatarotational frequencyof150r/minto300r/min. 7.1.4 Titrationvessel ,ofapproximately200mlcapacity,withatleastthreeg
24、roundglasssockets. Connectoneofthegroundglasssocketstotheautomaticburette.Placetheplatinumdoubleelectrodeinthe automaticburette,andtheplatinumdoubleelectrodeinthesecondone,andusethethirdonetoaddthereagents andthesample.Adischargetapatthebottomofthevesselisanadvantage.Connectittothevesselwitha capill
25、arytubehavingavolumeofnotmorethan0,5ml.Closeallventilationsocketsinthetitrationvesseleitherwith dryingtubeswhichhavebeenchargedwithaneffectivedryingagentormolecularsieves,orwithdryingreceivers filledwiththereagent(6.3)inordertoavoidtheinfluenceofmoisturefromtheair. 1) Suitableproductsarecommercially
26、available.OSI ISO11021:1999(E) 3 7.1.5 Automaticburette ,of25mlcapacity,graduatedinintervalsof0,05ml,andreagentbottleanddryingtubes. Theminimumintervaloftheburettedependsondatafromthemanufacturer(e.g.0,02ml). Protectthereagentbottle,theburetteandtheKarlFischerreagent(6.3)frommoistureandlight. 7.2 Ov
27、en,regulatedat130C 5C,todrytheglassware. 8Sampling ArecommendedsamplingmethodisgiveninISO212. NOTE AttentionisdrawntothefactthatthemethodgiveninISO356cannotbeusedtopreparethetestsamplesasit specifiesthatthesamplehastobedried. 9Procedure 9.1 Preparationofthetitrationapparatus Preparethetitrationappar
28、atus(7.1)inaccordancewiththemanufacturersinstructionsandlubricateeveryjoint. Theairtightnessofthetitrationvesselisofspecialimportance. Place25mlofthedriedmethanol(6.1)orofthe2methoxyethanol(6.2)inthetitrationvessel(7.1.4).Besurethat themetallicpartsoftheplatinumdoubleelectrode(7.1.2)arecompletelyimm
29、ersed.Starttheautomatictitration (7.1.3). AddKarlFischerreagent(6.3)toenableareactiontotakeplacewiththetracesofwaterinthemethanol.The titrationandtherecognitionoftheendpointiscontrolledautomaticallybytheapparatus. 9.2 StandardizationoftheKarlFischerreagent Preparethetitrationapparatusasindicatedin9.
30、1. Weigh,tothenearest0,0001g,approximately0,300gofthepotassiumbitartrate(6.4).Introducequantitativelyand asfastaspossible,themass( m 1 )ofthebitartratetothetitrationvessel(7.1.4). Titratetheknownamountofwaterintroducedinthevesselbythedipotassiumsaltoftartaricacid,withtheKarl Fischerreagenttoperformt
31、hestandardization.Thetitrationandtheendpointarecontrolledautomaticallybythe apparatus. Recordthevolume( V 1 )ofthereagentusedwiththebitartrate. Standardizationofthereagentmayalsobecarriedoutwithaknownmassofpurewater( m 2 ),approximately 0,040g,measuredtothenearest0,0001g. Recordthevolume( V 2 )ofthe
32、reagentusedwiththewater. Carryoutseveraltitrationswithoutchangingthetitrationvessel.Usethearithmeticmeanoftheresultsforthe calculationofthewaterequivalentofthereagent(10.1). 9.3Determination Preparethetitrationapparatusasindicatedin9.1. Dependingontheexpectedwatercontentofthesample,takeaportion( V 0
33、 ml)ofthesample(10,0mlifthewater contentis,3%or25,0mlifthewatercontentis,1%)andplaceitveryquicklyinthetitrationvesselata temperaturebelow25C,asslurringanddissolutionmayoccur.ISO11021:1999(E) OSI 4 Starttheautomatictitrationwhilestirringwiththemagneticstirrer(7.1.3).Thetitrationandtherecognitionofthe
34、 endpointarecontrolledautomaticallybytheapparatus. Recordthevolume( V 3 )ofthereagentused. Carryoutthreetitrationsoneachsampleandusethearithmeticmeanoftheresultsforthecalculation(10.2). 10 Expressionofresults 10.1 WaterequivalentoftheKarlFischerreagent Thecalculationofthewaterequivalent, T,oftheKarl
35、Fischerreagent(6.3),expressedinmilligramsofwaterper millilitreofreagent,isgivenbyoneoftheformulae: T m V = 1 1 05 18 235 28 , , or T m V = 2 2 where m 1 isthemass,inmilligrams,ofthedipotassiumsaltoftartaricacid(6.4)introducedwhenthisreagent isusedforstandardization(9.2); V 1 isthevolume,inmillilitre
36、s,ofthereagent(6.3)usedforthestandardization; 0,5 isthenumberofwatermolespermoleofdipotassiumsaltoftartaricacid; 18 istherelativemolecularmassofwater; 235,28 istherelativemolecularmassofdipotassiumsaltoftartaricacid; m 2 isthemass,inmilligrams,oftheknownpurewater(6.4),ifwaterisusedforstandardization
37、 V 2 isthevolume,inmillilitres,oftheKarlFischerreagent(6.3)usedforthestandardization. 10.2 Watercontentoftheessentialoil Thewatercontentoftheessentialoil, W w ,expressedasamassfractioninpercent,isgivenbytheformula: W VT V w = 3 0 10 r where V 0 isthevolume,inmillilitres,ofthetestportion(9.3); r ist
38、hedensityofthesample,ingramspermillilitre,at20C; V 3 isthevolume,inmillilitres,oftheKarlFischerreagent(6.3)usedforthedetermination(9.3); T isthewaterequivalent,inmilligramsofwaterpermillilitreoftheKarlFischerreagent(6.3), calculatedinaccordancewith10.1. Tocalculatethedensityoftheessentialoil,multipl
39、ythevalueobtainedfortherelativedensitybythedensityof waterat20C,thatis0,99823g/ml.OSI ISO11021:1999(E) 5 11Test report Thetestreportshallspecify: themethodused, thetestresultobtained; anyoperatingdetailsnotspecifiedinthisInternationalStandard,orregardedasoptional,aswellasany circumstancesthatmayhave
40、influencedthetestresult. Thetestreportshallincludeallinformationrequiredforthecompleteidentificationofthesample.ISO11021:1999(E) OSI 6 Bibliography 1ISO212, EssentialoilsSampling. 2ISO356, EssentialoilsPreparationoftestsamples .BS ISO 11021:1999 BSI 389 Chiswick High Road London W4 4AL BSI British S
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