Novel Manganese Colorimetric Chemosensing Investigations of Indigofera macrophylla Schum (Thonn.) Stem and Leaf dye Extracts
Purpose: To determine the chemosensor ability of dye extracts obtained from the stem and leaves of Indigofera
macrophylla Schum (Thonn.), a scandent or climbing shrub belonging to the family Fabaceae.
Method: The dye extracts were obtained from the stem and leaves of the plant after optimizing the method of
extraction, the concentration of base for precipitation as well as the contact time between base and aqueous plant
extracts. The dyes were investigated for their colorimetric chemosensor properties using procedures such as
screening of metals and non-metals, selection of analytical wavelengths, optimization of solvents, reaction
temperature and time. Validation was carried out for the determination of manganese from aqueous solution by
preparation of calibration curve, accuracy and reproducibility. Interference liabilities of the new method for
manganese were studied in the presence of common cation and anions.
Results: The dyes were obtained in good yield and gave pink colours. Spot tests revealed the selective detection of
manganese from the two dye extracts. These two dyes; the stems (DS and leaves (DL) dyes of Indigofera
macrophylla) proved to be excellent colorimetric chemosensors for manganese in an aqueous solution. Linearity in
Beer’s law plot were obtained within the concentration range of 10-50 μg/mL (r2 = 0.996 and 0.999 for DS and DL
respectively). Accuracy gave relative errors generally less than 2.0% while for the precision, the relative standard
deviations were less than 0.8%. There was no interference with common cations such as Cr3+, Cu2+, Zn2+ and anions
such as CN- and NO2-
Conclusion: The natural dyes obtained from Indigofera macrophylla could be excellent sources of chemical
principles for the detection and determination of manganese in aqueous solutions.
Keywords: Indigofera macrophylla, Natural dyes, Manganese, Colorimetric chemosensor, Interference studies
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