Hydroxypropyl-B-cyclodextrin effect on the fluorescence of auxin and skatole and on the simultaneous determination of binary mixtures of indole compounds in urine by first derivative spectrofluorimetry

R. E. GALIAN; A. G. BRACAMONTE ; A. V. VEGLIA

ANALYTICA CHIMICA ACTA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2005 vol. 540 p. 393 - 401

0003-2670

The effect of hydroxypropyl--cyclodextrin (HPCD, -cyclodextrin (CD) derivative) was determined on the fluorescence emissionspectra of skatole (3-methylindole, MI) and auxin (indole 3-acetic acid, IA). The experiments were conducted at excitation wavelength(λex) = 280 nm, in aqueous solutions at different pH values, with and without HPCD as receptor. The enhanced fluorescence in the presenceof the receptor showed a 1:1 host?guest interaction and the values of the association constants KA were between 100 and 200 mol−1 L. Theeffects of methanol and propanol with and without receptor were also studied. The limit of detection (LD) for the HPCD enhanced fluorimetricmethod at pH = 7.00 were 0.279 and 0.765 ngmL−1 for MI and IA, respectively. For the determination of indole compounds with closelyoverlapping spectral bands a zero-crossing first derivative spectrofluorimetric method with or without HPCD is described. Binary mixturesof MI or IA with melatonin (N-acetyl-5-methoxytryptamine, M) or 5-methoxytryptamine (5-methoxy-3-(2-aminoethyl)indole, 5M) wereanalysed in the presence of HPCD. In the absence of receptor, binary mixtures of MI with IA andMwith 5M were determined. The matrixeffect was evaluated in urine samples by the method of standard addition. Good apparent recoveries were found for each indolic compoundby the direct method (98?105% with R.S.D. 0.5?5%) and for mixtures of them by the first derivative method (90?105% with R.S.D. 1?5%)indicating the applicability of them with the advantage of their simplicity, low cost in materials, no time consuming and no requirement ofthe use of a sophisticate calibration program.