ß-Ciclodextrin complexation with phenolphthalein

ß-Ciclodextrin complexation with phenolphthalein: Spectrophotometric determination
of deoxycholic acid (DCA)
Cadena, P.G.1,2,3*, Oliveira, E.C.2 , Silva, R.A.1, Araújo, A.N.4,
Montenegro, M.C.B.S.M.4 , Pimentel, M.C.B.2, Lima Filho, J.L.1,2 , Lins, V.L.1,3
1
Mestrado em Bioquímica e Fisiologia – UFPE; 2Laboratório de Imunopatologia Keizo
Asami-LIKA/UFPE; 3Laboratório de Engenharia e da Qualidade AmbientalLEAQ/UFPE; 4Departamento de Química Analítica/UP
*[email protected]
Cyclodextrins (CDs) are cyclic oligosaccharides composed of six or more glucose
units linked by a-(1,4) bonds. In aqueous solution, they form inclusion complexes with
a wide range of solid, liquid and gaseous compounds, dyes and bile acids as the
deoxycholic acid (DCA) which is contained in pharmaceutical formulations . The
objective of this work was the study of the inclusion complex ß-cyclodextrinphenolphthalein (ß-CD-PHP) with capacity to spectrophotometric determination of the
DCA. UV-visible spectrum was used to determinate the best inclusion complex
between phenolphthalein (3.1x10 -4mol/L) and different concentrations of ßcyclodextrins (5.17x10-5–1.86x10-3mol/L). ß-CD-PHP complex was used to measure
different concentrations of DCA (1.56x10 -5–6.25x10-3mol/L). The 23 factorial design
was performed to evaluate the effect of factors: inclusion comple x concentration (ßCD: 6.2x10-4–1.86x10-3; FE:1.55x10-4–4.65x10 -4mol/L), pH (9.2–9.8) and temperature
(20–30°C). The optimal pH (9.2–10.7) of the measurement was determined. The best
concentration of ß-cyclodextrin to form inclusion complexes with phenolphthalein was
1.24x10-3mol/L, the absorbance decreased 97% at 553nm. DCA was determined
initially in the range 6.25x10-3–3.13x10 -4mol/L. Statistical analysis of the results
showed that only pH had a significant effect on the DCA determination by inclusion
complex ß-CD-PHP. In spite of other variables and second order interactions between
them were not significant (p=0.05). The optimal pH was 10.5 and the detection limit
was 5.88x10-5mol/L. The inclusion complex ß-CD-PHP was efficient and fast to
measure the D CA concentration, what suggests its application in optical biosensors.
Supported by: UFPE, CNPq, FACEPE, CAPES/GRICES