Chemistry Reference
In-Depth Information
aportionisdilutedandcentrifuged,andthenthesameprocedureisfollowedasforthebeverages
(Jiménezetal.2009).
Fouriertransforminfrared(FTIR)spectroscopyisreportedasaquickmethodforthedetermi-
nationofACS-Kincommercialdietfoodsampleswithouttheuseofevenanextractionprocedure
prior to analysis. Samples that are characterized as dificult food matrices like chocolate syrup,
coffeedrink,coffeecreamer,cranberryjuice,icecream,andinstantchocolatemilkcanbeeasily
analyzed.Theicecreamsampleisconvertedtomixtureat60°Cinawaterbathwithcontinuous
agitation.Allothersamplesareusedwithoutanypretreatments.Aportionofeachfoodsampleis
mixed thoroughly with ultrapure water. The biggest advantages of direct measurement through
FTIRspectroscopyarespeedandlackoftime-consumingsamplepretreatment.Thesamplesare
then maintained at 40°C in an incubator followed by ultrasonication. Carrez I (3.6 g potassium
hexacyanoferrate trihydrate dissolved and made up to 100 mL with distilled water) and Carrez
IIreagent(7.2gzincsulfateheptahydratedissolvedto100mLwithdistilledwater)solutionsare
added to the samples, followed by centrifugation at 4°C. The supernatant is carefully separated
usingasyringetoavoidthefatlayerforeachsampleandiltered.Thewater-solubleextractobtained
isdirectlypouredontothesurfaceofattenuatedtotalrelectance(ATR-FTIR;Shimetal.2008).
The simultaneous determination of other additives including ACS-K and ASP in some food
samplesisverycommonnowadays.Forexample,asimultaneousdeterminationinafoodsample
of soy sauce has been reported. For the pretreatment of this sample, it is placed in a volumetric
laskandthendilutedwithwater.Aftermixingthoroughly,aportionofthesolutionisaddedtoa
Sep-PakC
18
cartridge.Someadditivesthatarenotadsorbedbythepackingmaterialcomethrough
thecartridgeandarecollectedaseluateA.Thenwaterispassedthroughthecartridgetoremove
interferingsubstances.Theotheradditivesthatareabsorbedontothepackingmaterialwerethen
elutedwithacetonitrile-water(2:3,v/v)andcollectedaseluateB.EluatesAandBarecombined
andpouredintoavolumetriclaskanddilutedtovolumewithacetonitrile-H
2
O(2:3,v/v).Thesame
procedurecanbefollowedforfoodsampleofdriedroastbeefandsugaredfruit.Theonlydifference
isthattheyarepreviouslygroundintoineswithagrinder(ChenandFu1995).
Appropriate extraction and cleanup procedures maximize recovery of saccharin. For its efi-
cient extraction, the analyst should optimize the solvent volume and its pH prior to extraction.
Optimalsamplepreparationcanreduceanalysistime,enhancesensitivity,andoptimizeconirma-
tion and quantiication of saccharin. The most common sample preparation procedures that are
foundnowadaysinpublishedproceduresusetheSPEtechnique.Itissimple,reproducible,quick,
andinexpensive.TheSPEtechniquefractionsthecompoundsofourchoicebasedontheafinityof
thecompoundoragroupofcompoundstothestationaryphase.TheprotocolofanSPEprocedure
consists mainly of four steps. First, the conditioning of the cartridge precedes, followed by the
loadingofthefoodextract;washingofthecartridgefollows,andinally,elutionoftheanalytesis
performedbyadequatesolvent(s).ThetypeofSPEpackingmaterial,solvents,pH,andlowrates
needtobeproperlyselectedinordertoretainanalyteseffectivelywithinthecartridge.Theinterfer-
ingsubstancesshouldberetainedverystronglyornotretainedatall.Asaresult,weaklyretained
substancesareremovedfromthecartridgeduringsampleloadand/orcartridgewash.Analytesare
elutedduringtheelutionstep,andinterferingsubstanceshavingastrongafinitytothesorbentstay
adsorbedwithinthecartridge.SPEproceduresareuniversalandcompatiblewiththemostpopular
techniquesusedinfoodanalysis(Tunick2005).Inpublishedproceduresforthedeterminationof
saccharin,onecanwitnessavarietyoffoodmatricesbeingsuitablytreatedpriortoanalysis.Cola
drinksareusuallydegassedinanultrasonicbath(Demiralayetal.2006).Thesameappliestoevery
carbonateddrink.Degassingisperformedbysonication,byspargingwithnitrogen,orundervac-
uum.Chewinggumsamplesarepreparedbyplacingtheminalaskandextractingwithamixture
ofglacialaceticacid,water,andchloroform.Hardorsoftcandysamplesareshakenwithwateruntil
dissolved(Biemer1989).Milkanddairyproductsarehomogenizedpriortoanalysis,andanaliquot
ofahomogeneoussampleistransferredtoalaskfollowedbytheadditionofdistilledwater.The
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