Chemistry Reference
In-Depth Information
AMEKC-UVprocedureisabletodetermineASPandACS-Kwithsaccharin,dulcin,alitame,
caffeine,benzoicacid,andsorbicacidinlow-energysoftdrinks,cordials,tomatosauce,marma-
lades,jams,andtabletopsweeteners.Anuncoatedfused-silicacapillary(75cm×75μm)wasused
asthestationaryphaseandthemobilephaseconsistedofabuffercomprisingsodiumdeoxycho-
late,potassium-dihydrogenorthophosphate,andsodiumborate(pH8.6).Therecoveryis104%to
112%,andtheRSDis0.63%to2.6%forallanalytesdetermined(Thompsonetal.1995).Another
MEKC-UVprocedureisabletodetermineASPandACS-Kwithsaccharin,preservatives,andanti-
oxidantsincolabeveragesandlow-energyjams.Afused-silicacapillary(52cm×75μm)wasused
asthestationaryphaseandthemobilephaseconsistedofboratebufferwithNacholate,dodecyl
sulfate,andMeOH(pH9.3).Therecoveryis98.9%to100.86%,andtheRSDis0.9%to1.5%for
allanalytesdetermined(Boyce1999).Finally,aMEKC-UVprocedureisabletodetermineASP
andACS-Kwithsaccharin,preservatives,andcolorsinsoftdrinks.Anuncoatedfused-silicacapil-
lary(48.5cm×50μm)isusedasthestationaryphaseandthemobilephaseconsistedofcarbonate
buffer(pH9.5)withsodiumdodecylsulfate.TheLODis0.005mg/mLforallanalytesdetermined
(Frazieretal.2000).
Asimplemethodforthesimultaneousdeterminationofiveartiicialsweeteners,alitame,ACS-
K,saccharin,ASP,anddulcin,invariousfoodsbyHPLCanddetectingthespeciesat210nmwas
reported.Therecoveriesoftheivesweetenersfromvariouskindsoffoodsspikedat200mg/granged
from77%to102%.Thedetectionlimitsoftheivesweetenerswere10mg/g(Kobayashiet al.1999).
ThemostpopularreferencemethodusedinbibliographyistheHPLC-DADmethodproposed
byLawrenceandCharbonneau.A5-mmC
8
silicaina150mm×4.6mmcolumnwasusedasthe
stationaryphaseinthismethod,withamobilephasegradientrangingfrom3%acetonitrilein0.02
MKH
2
PO
4
(pH5)to20%acetonitrilein0.02MKH
2
PO
4
(pH3.5)ataconstantlowrateof1.0
mL/min.Thechromatogramswereobtainedatawavelengthof210nm.Inordertoobtainthecali-
brationfunction,sixdifferentconcentrationlevelsandthreereplicatesofeachoneofthestandard
solutionsareanalyzedusingpeakareaastheanalyticalparameter(Lawrenceetal.1988).
QuantitativedeterminationbyGCisimpossibleduetothelowvolatilityofACS-Kanddueto
thefactthatmethylationproducesdifferingratiosofmethylderivatives.Amethodofdetermining
ASPanditsdegradationproductswasreportedin1975byGC(Furdaetal.1975).
CE,asmentionedabove,isaninterestingalternativetoHPLC,andtheresolvingpowerofthis
technique is, in many cases, comparable with that of HPLC; frequently, their running costs are
lower.High-pressureCEappearstobeaviablemethodforthedeterminationofASPinrealcom-
mercialproducts.TheanalysistimeissigniicantlyfasterthanthatreportedforHPLCmethods,and
nointerferencesweredetectedinsoftdrinksamplestested.Caffeinehasadifferentmigrationtime
fromASP,anditslowsensitivityatthedetectionwavelengthprecludestheappearanceofapeakin
theelectropherogram.ThelinearcalibrationcurvedevelopediscompatiblewiththerangeofASP
concentrationsoramountsintheproductstested.ItappearsthatasmallamountofASPadsorption
occurs on the capillary walls, but this affects quantitative determinations well below the useful
rangefortypicalcommercialsamples.Alinearcalibrationcurvebetween25and150μg/mLforthe
analytesolutionisestablished,whichcanbeusedforquantitativedeterminationsofASPintypical
foodandbeverageproducts.Sixcommercialsamplesareanalyzed,andonedietcolawithaknown
ASPconcentrationgivesanRSDof2.6%fromthemanufacturer'svalue(Quetal.1999).
A method for isotachophoretic determination of sweeteners of different character in candies
and chewing gums is developed. A capillary made of luorinated ethylene-propylene copolymer
withaninternaldiameterof0.8mmandaneffectivelengthof90mmisilledwithanelectrolyte
systemconsistingofaleadingelectrolyte(10mMHClwith14mMTris,pH7.7)andaterminat-
ingelectrolyte(5mMl-histidinewith5mMTris,pH8.3).Theanalysisisperformedatadriving
currentof200μA,andfordetectioncurrent,themagnitudeisdecreasedto100μA.Boricacidis
addedtotheaqueoussamplesolutiontoformboratecomplexeswithsubstancesofpolyhydroxyl
natureandmakethemtomigrateisotachophoretically.Usingconductivitydetection,thecalibration
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