Chemistry Reference
In-Depth Information
picryl chloride, p-quinone for cyclamate; vanillin for glycyrrhizin; Nile blue, azure A, B, or C,
Sevronblue5G,brilliantcresylblueforsaccharin;andanthroneforsteviosides)areusedforthe
directdeterminationofhigh-intensitysweeteners(Yebra-Biurrun2005).
9.18.5 titrimetric Methods
Titrimetric assays have been developed for acesulfame K (titrated with sodium methoxide in
benzene),aspartame,sodiumcyclamate,sodiumsaccharin(titratedwithperchloricacid),andsac-
charin(acidform),withpotassiumhydroxideactingasatitrant.Precipitation,chelatometric,and
redoxtitrationsareproposedforthedeterminationofcyclamate.Theoldestmethodsforsaccharin
involve its determination by means of a Kjeldahl procedure (Yebra-Biurrun, Cancela-Perez, and
Moreno-Cid-Barinaga2005;Yebra-Biurrun,Moreno-Cid,andCancela-Perez2005).
9.18.6 electrochemical Detection Systems: Biosensors
Electrochemical methods have also been used for the detection of artiicial sweeteners as
reportedintheliterature(Assumpcaoetal.2008;Medeirosetal.2008).
Anotherelectrochemicaldetectionsystembasedonacoated-carbon-rodion-selectiveelectrode
forthedeterminationofsaccharinindietaryproductshasalsobeendescribedrecentlybyFatibello-
FihloandAniceto(1997).
Lipidilmscanbeusedfortherapiddetectionorcontinuousmonitoringofawiderangeofcom-
poundsinfoodsandintheenvironment.Suchelectrochemicaldetectorsaresimpletofabricateand
canprovideafastresponseandhighsensitivity(NikolelisandPantoulias2000).
Nikolelis et al. (2001) explored the interactions of the sweeteners acesulfame K, saccharin,
andcyclamatewithbilayerlipidmembranes(BLMs).BLMscomposedofeggphosphatidylcholine
canbeusedforthedirectelectrochemicalsensingofthesesweeteners. Theinteractions ofthese
compoundswithlipidmembraneswerefoundtobeelectrochemicallytransducedintheformofa
transientcurrentsignalwithadurationofseconds,whichreproduciblyappearedwithin11safter
exposureofthemembranestothesweetener.Themechanismofsignalgenerationwasinvestigated
bydifferentialscanningcolorimetry(DSC)studiesandmonolayercompressiontechniques.DSC
showedthattheinteractionsofthesweetenerswithlipidvesiclesstabilizethegelphaseofthelipid
ilms.
These latter studies revealed the adsorption of sweeteners caused an increase of the average
molecularareaoccupiedbythelipidsandresultedinincreasedstructuralorderofthemembranes.
ThedetectionlimitofacesulfameKis1μm,andthereproducibilityisontheorderof±4to8%
ina95%conidencelevel.Therecoveryrangedbetween96%and106%andshowsnointerferences
fromthematrix(Nikolelisetal.2001).
Theweakpointsofthepresentsensorcomparedwithconventionalanalyticalmethodsarethat
there is no selectivity to discriminate between artiicial sweeteners, i.e., acesulfame K, saccha-
rin,andcyclamate,andthefragilityandtheverylimitedstabilityofthefreelysuspendedBLMs.
However,thepresenttechniquecanbeusedasaone-shotsensorfortherapiddetectionofthese
sweetenersbutkeepsprospectsforpotentialapplicationsfortheselectivedeterminationandanaly-
sisofmixturesofacesulfameK,saccharin,andcyclamateingranulatedsugar-substituteproducts
byusingiltersupportedBLMs(Nikolelisetal.1999,2001).
Commerciallyavailablebiosensorsforapplicationsinthefoodandbeverageindustryarebased
oneitheranoxygenelectrodeorahydrogen-peroxideelectrodeinconjunctionwithanimmobi-
lized oxidase. Targeted compounds include artiicial sweeteners such as aspartame, saccharin,
cyclamate, and acesulfame, which are used in soft drinks and desserts (Luong, Bouvrette, and
Male1997).
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