Studies of red cabbage (Brassica oleracea) and henna (Lawsonia inermis) leaves extracts as greener indicators in acid-base titrimetry
Kaana Asemave, Ayar Moses Hennen
The work considered studies of BOI (Brassica oleracea extract indicator) and LII (Lawsonia Inermis leaves extract indicator) as green indicators versus some synthetic indicators in acid – base titration involving HCl-NaOH, CH3COOH-NaOH, CH3COOH -NH4OH, and HCl-NH4OH. About 10 mL of each base respectively, with three drops of the BOI, LII, MO (methyl orange), and PL (phenolphthalein) were used. Prior to the titrations, the extracts of Brassica oleracea and Lawsonia Inermis were tested for their colours in acidic and basic media. Also, the UV-visible absorptions of the extracts were determined. There were sharp colours of pink (for BOI) and yellow (for LII) in acid; and green (for BOI) and brown (for LII) in base media. Both LII and BOI absorbed substantially in the UV-Visible region. The titre values of 12.10 ±0.70 mL (SA-SB), 14.95±0.15 mL (WA-SB), 2.05±0.35 mL (WA-WB), 1.40±0.28 mL (SA-WB) and 12.50±0.42 mL (SA-SB), 34.90±0.57 mL (WA-SB), 35.90±0.28 mL (WA-WB), 2.75 mL (SA-WB) were obtained for BOI and LII, respectively. The results matched with the values 12.25±0.15 mL (SA-SB), 13.90±0.7 mL (WA-SB), 2.10±0.2 mL (WA-WB), and 3.00±0.6 mL (SA-WB) of PL and MO, respectively, except with LII (for WA-SB and WA-WB). Hence LII is unsuitable for use as in indicator for the titrations of WA-SB and WA-WB, unlike BOI and PL. It will be beneficial to us to replace the use of MO and PL as indicators with BOI and LII as much as practicable, because these green indicators are more benign and also effective. This will facilitate the eradication of toxicity accruing from synthetic indicators, MO and PL. In the future, we are looking out to determining the pKa and stability of these natural indicators.
Kaana Asemave, Ayar Moses Hennen. Studies of red cabbage (Brassica oleracea) and henna (Lawsonia inermis) leaves extracts as greener indicators in acid-base titrimetry. International Journal of Chemistry Studies, Volume 5, Issue 2, 2021, Pages 44-48