3. Results and discussion
3.1. Optimum condition of guava leaf extract-iron
complex formation
The aim of this study was to find a suitable acidic solution for guava leaf extract–iron complex formation. Buffers of acidic pHs that can be prepared with easily available chemicals that would not interfere with the iron determination are
rare. A suitable solution was sodium acetate buffer pH 4.8.
Ammonium acetate was avoided because ammonium may
form a complex with the metal ion of interest. To ensure the
necessity of buffer solution in this study, water pH 7.0 and
HCl diluted to pH 4.8 were also used as media for extraction
to compare the results.
Fig. 2(a) and (b) represents the absorption spectra of guava
leaf extract-iron complexes in water and buffer solution,
respectively. In water (Fig. 2 (a)), no significant iron complex absorption is shown in the region of 450–700 nm, and
except for high Fe (III) concentration, it is suppressed. This
is likely because water cannot extract active species from
the guava leaf. It could also be possible that there was no
formation of iron complex with the active species or the
Fig. 2. (a) The absorbance spectra of guava leaf extract–iron complex in
water, measured against water. (b) The absorbance spectra of guava leaf
extract–iron complex in acetate buffer solution, measured against acetate
buffer: ( ) guava leaf extract; ( ) guava leaf extract with Fe (III) 100 ppm;
( ) guava leaf extract with Fe (III) 10 ppm; () guava leaf extract with Fe
(II) 100 ppm and (× ) guava leaf extract with Fe (II) 10 ppm