Cyclodextrin enhanced fluorimetric method for the determination of tryptamine.
The effect of native cyclodextrins (alpha-, beta- or gamma- with six, seven or eight glucose units, respectively), hydroxypropyl-beta-cyclodextrin, beta-cyclodextrin solubilized in urea, soluble starch and glucose in water solution on the fluorescence behaviour of tryptamine [3-(2-aminoethyl)indole] (T) was determined. In addition, the effect of methanol and propanol with and without beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin was ascertained. From the fluorescence changes with pH and with beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin, the values of the pKa of the ground and excited states and the association constants of T and TH [3-(2-ammoniumethyl)indole] with the two hosts were determined. The values are pKa = 9.5 +/- 0.2 and pKa* = 8.4 +/- 0.2; KAssocTH = (1.6 +/- 0.3) x 10(2) mol-1 dm3 and KAssocT = (2.8 +/- 0.3) x 10(2) mol-1 dm3 with beta-cyclodextrin, KAssocTH = (1.8 +/- 0.5) x 10(2) mol-1 dm3 and KAssocT = (4.9 +/- 0.9) x 10(2) mol-1 dm3 with hydroxypropyl-beta-cyclodextrin. The ratio of the fluorescence quantum yields for the bound and free substrate (phi b/phi f) were in the range 1.25-1.33. The detection limit for the better conditions where the host-guest interactions produce fluorescence enhancement was 0.454 +/- 0.002 ng ml-1 for the complex T-hydroxypropyl-beta-cyclodextrin in water. The method is simpler than others reported previously.
Galian
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RE
Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
Veglia
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AV
de Rossi
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RH
D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014363:Tryptamines / Q000032:analysis*
D014363:Tryptamines; C030820:tryptamine