Chemistry Reference
In-Depth Information
In literature, a number of sensitive methods have been proposed overcoming the drawbacks
ofinterferences.Arapid,sensitive,andselectivespectrophotometricmethodisdevelopedusinga
formationofsaccharinwithNileBlue(Cordobaetal.1985).Theformationofsaccharinwithdyes
isasmartwaytoenhancesensitivity.SpectrophotometrycoupledwithanFIAsystemoffersrepro-
ducibleandaccurateresults(Capitán-Vallveyetal.2004b).Recently,asensitivespectrophotometric
methodhasbeenproposed,takingadvantageofthedifferentkineticratesofsaccharinandother
sweetenersintheiroxidativereactionwithKMnO
4
.Thedataobtainedfromthekineticratesofeach
analytewereprocessedwiththehelpofchemometrics(Nietal.2009).
For routine analysis of complex food matrix samples, MEKC, HPLC, and IC are preferred
(Table4.2).Theseinstrumentalmethodsareimportantreferencemethodsforfoodsampleanalysis.
HPLCiscommonlyusedforfoodsampleanalysis.Liquidchromatographicdeterminationofsac-
charininfoodissimplebecausebeveragesoraqueousextractsfromfoodscanoftenbeinjected
intoacolumnimmediatelyafteriltration.Themostapplicablemethodforthedeterminationofsac-
charinisreverse-phaseHPLCcoupledwithUVlightdetector.Themostpopularreferencemethod
thateverybodycancomeacrossinbibliographyistheHPLC-diodearraydetector(HPLC-DAD)
methodproposedbyLawrenceandCharbonneau(1988).A5-μmC
8
bondedsilicaina150mm×
4.6mmcolumnwasusedasastationaryphaseinthismethod,withamobilephasegradientranging
from3%acetonitrilein0.02MKH
2
PO
4
(pH5)to20%acetonitrilein0.02MKH
2
PO
4
(pH3.5)at
aconstantlowrateof1.0mL/min.Thechromatogramswereobtainedatawavelengthof210nm
(Lawrenceetal.1988).
TheanalyticalconditionsforthedeterminationofsaccharinbymeansofHPLC-ESI-MShave
been studied recently. MS is a powerful qualitative and quantitative analytical technique that has
beenintroducedinmanyanalyticalandresearchlaboratoriesinthelast10years.Thecombinationof
HPLCwithtandemMSyieldsaparticularlypowerfultool,anditisthefuturemethodofchoicefor
thedeterminationofsweeteners.Asimpleandrapidmethodforthesimultaneousdeterminationof
ninesweeteners,includingsaccharin,invariousfoodsbyHPLC-ESI-MSisdeveloped.Massspectral
acquisitionisdoneinthenegativeionizationmodebyapplyingselectedionmonitoring.Thesweeten-
ersareextractedfromfoodswith0.08mol/lphosphatebuffer(pH7.0)-ethanol(1:1),andtheextract
iscleaneduponaSep-pakVacC
18
cartridgeaftertheadditionoftetrabutylammoniumbromideand
phosphate buffer (pH 3.0). The quantiication limit of saccharin is 1 mg/kg (Koyama et al. 2005).
AnothersimultaneousdeterminationmethodofsaccharinandotheradditivesinfoodsbyLC-ESI(-)-
MS/MSisproposed.Amixtureofacetonitrile-water(1:1)wasusedtoextracttheseadditivesfrom
solidfoodmatrices,andacetonitrilewasusedtoextractthemfromliquidfoodmatrices.Saccharin
wasidentiiedanddeterminedinthenegativeionizationmodeusingsinglereactionmonitoring(SRM)
oftheproduction(
m
/
z
=106)fromitsprecursorion(
m
/
z
=182;Ujiieetal.2007).
CEisaninterestingalternativetoHPLC.Theresolvingpowerofthistechniqueiscomparablewith
thatofHPLC.DifferenttypesofCEhavebeenused.MEKC(Boyce1999)andcapillaryisotachopho-
resis(Herrmannováetal.2006)arethetypesofCEmostusedforthedeterminationofsaccharin.
Inthepast,thepreferredtechniqueusedforscreeningsaccharinandothersweetenerswasTLC,
andforquantiication,itwasgaschromatography(GC).TLCmethodsweredevelopedforseparat-
ingsweetenersfromotherimpuritiesusinggenerallylayersofpolyamide.ATLCmethodthatwas
developedin1970detectedsaccharininaquantityof2μginvariousfoods(Takeshita1972).In
literature,thereareanumberofmethodsthatdeterminesaccharinandothersweetenersbyTLC-
UVandarecharacterizedbyasensitivitythatluctuatesinthemicrogramrange(Nagasawaetal.
1970).ArtiicialsweetenersincludingsaccharinhavebeendeterminedbyGCmethods,whichare
usually sensitive and selective. The only main drawback of GC methods is the time-consuming
derivatizationstep.Thisstepisnecessaryfortheconversionofsweetenersinvolatilecompounds,
sothatwecandeterminethemwithGC.Thederivatizationofsacchariniscommonlyachievedwith
trimethylsilylation(Dickes1979).
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