AOAC 998.12-1998 C-4 Plant Sugars in Honey - Stable Carbon Isotope Ratio Method

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1、44.4.18Apumpbyvalves,andpumpoffO.CoolpurificationtrapwithsolidAOACOfficialMethod998.12CO2–acetone;coolanalytetubewithliquidnitrogen.LetcollectionC-4PlantSugarsinHoneytrapwarm,condensingimpuritiesinsolidCO2trapandCO2inInternalStandardanalytetube.StableCarbonIsot

2、opeRatioMethod(b)Soferprocedure.—Use9in.(22.9cm)PasteurpipettoplaceFirstAction19983–5mgtestportiononsidewallofpreparedcombustiontube,[MethodisusedtodemonstrateC-4(cornorcane)sugarsinhoneyspreadingasthinfilminstripalongaxisoftube.Avoidplacingataconcentration>7%.

3、]materialwithin3–4cmofopenend.Covertestportionwith3–5gResultsoftheinterlaboratorystudysupportingacceptanceoftheCuOandlettuberemainhorizontal³5min.Placetubeindryingovenmethod:at60°–65°Cfor³8h.Removetubesfromoven,holdvertically,andRange=–0.30‰(2.1%)to–1.9‰(13.6%)

4、;sr=1.25–2.69;sR=tapfirmlytodislodgeCuOparticlesfromwallareawheresealwillbe11.25–2.69;RSDr=9.22–90.0%;RSDR=14.5–92.0%made.Whiletubesarestillwarm,place1–6analytetubesonvacuumA.Principlemanifoldandevacuatebymechanicalpump3–4min,thensealtubesStablecarbonisotoperat

5、iovalueforproteinisolatedfromhoneywithtorch.PlacetubeshorizontallyinovenwithlooseCuOprovidesastandardtowhichstablecarbonisotoperatiovalueofthecoveringtestportionandbottomofeachtubeend-to-end.Combustwholehoneyiscompared.Thedifferencebetweenthesevalues(thetestpor

6、tionsat585°–590°Cfor1h.Lettubescoolinovenatleast1hISCIRAindex)isameasureoftheC-4sugarcontentofhoney.at<400°C.Attachtubestovacuumpurificationline,andbreaksealBothhoneyandproteinmustbeanalyzedonthesameinstrument.oropenwithatubecracker[seeAnal.Chem.48,1652(1976)].

7、PurifyandanalyzeCO2asdescribedinC(a).HoneyAlternativeI—BatchwiseMethodD.DeterminationFinalAction1979Operatemassspectrometeraccordingtomanufacturer’sB.Apparatusinstructions.Calibratewith³2standards,B(d).Correctvaluesobtainedforzeroenrichmentininletsystem,mixingb

8、etween(a)Combustionsystem.—Useoneofthefollowingoptions:samplingandstandardvalves,tailingofmajorontominorpeak(1)Craigprocedure.—Vacuum-tightglassmanifoldincluding17signal,and