Enzymeimmunoassayforthein-vitrodiagnosticquantitativedeterminationofhomovanillicacid(HVA)inhumanurine.Historically,colorimetricanalysisofHVAutilizedthereactionof1-nitroso-2-naphtholwithbiogenicamines,thenthemethodwasimprovedbysubstituting1-nitroso-2-naphthol-4-sulfonicacid.However,thecolorimetricmethodsarenotspecificforHVAduetoknowninterferencebymanycompounds.
Thinlayerchromatography(TLC)onsilicagelwasanotherapproachtodetermineHVA.Thismethodisslowandrequiresspecialequipment.Usingaflame-ionizationdetectorandelectron-capturedetection,agaschromatographic(GC)methodwasalsodeveloped,buthasnotbeenwidelyadaptedduetotherelativelypoorsensitivity.FurThermore,gaschromatography-massspectrometrywasalsousedforquantitatingofHVAinbothserumandurine.
Finallyhigh-performanceliquidchromatography(HPLC)methodsinvolvinginitialseparationofthebiogenicaminesbyanion-exchangechromatographyandfinalseparationbyreverse-phase(C18)chromatographyhavebecomemostcommon,andpreferredmethods.Thesemethodsarereasonablyrapid(althoughrequiressamplepretreatment),haveexcellentsensitivityandlittleinterferencefromotherendogenouscompoundsorexogenousdrugsandfoods.

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