Studies on the acid-base indicator properties of the pigments from pili (Canarium ovatum) exocarp

Fidel S. See

Date

10-1987

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Dario C. Sabularse

Abstract

SEE , FIDEL SEVA , University of the Philippines at Los Banos , October , 1997 . Studies on the Acid - Base Indicator Properties of the Pigrments from Pili (Canarium evatum ) Exocare.

Adviser Dr. Dario G. Sabularse .

The ethanol extract from the. exocarp of mature viii fruits was investigated for its acid - base indicator properties and its possible components were monitored by thin layer chromatography.

Prevarative thin layer chromatography of the alcohol extract using n-butanol-ethanol-water (80:20:40) as solvent system yielded five components which were colored yellow , pale yel1,7 , blue , yellow green , and brown with Pf values of 0.73 , 0.58 , 0.39 , 0.21 , and 0.12 respectively . Each pigment was partially characterized by solubility test ,absorbance measurements, and pH s,asitivity test . Results shaved that the blue , yellow green , and brown pigments were pH sensitive.

The pH transformation range and the transformation color of the indicator pigments , and the alcohol extract were determined in actual acid - base titrations . The alcohol extract had a pH transformation range of 6.77 - 8.00 . and a color change from red to light , alnost colorless green the blue pigment had

a range of 5.52 - 7.01 , a color change from pink to almost colorless. green . The yellow green and brown 7,ig-ments gave endpoint -pHs of 4.20 and 4.63 , respectively and color changer from light to yellow . The major pigment blue , was further isolated by using 35 5 methanolic - acetic acid as solvent . Its dissociation constant ,Ha , was determined by spectrophotometric methods . The average Ka calculated was 1.25 x 105 or pKa = 4.91 .

The blue pigment was partially characterized by spectral analyses . The infrared spectrum of the pig - cent showed signals for OH stretch in alcohols and phenels , C=C stretch for aromatic or alkene groups , and C -0 stretch in alcohols . The sisals however were very weak and net conclusive of the nature of the com-pound . The UV -Visible spectrum of the pigment in methanol showed a max at 215 no . In methanolic acetic acid its max was at 248 no .The UV-Visible spectra of the pigment were also not conclusive except for the probable presence of conjugated double bends .

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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