Acid-Base Indicator

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flower, for example, that is red, blue, or ... The use of natural dyes as ... as indicator in acid-base titration as compared ... titrations were performed using 10 ml of .... 4: Technological characterization of acid-base titration using standard indicator. Titration (Titrant v/s. Titrate) ... We can also conclude that, it is .... 10.0 ± 0.13.
RESEARCH ARTICLE

Preliminary Pharmaceutical Characterization Flowers as Natural Indicator: Acid-Base Indicator

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Sudarshan Singh 1*, Bothara Sunil B 2, Sangeeta Singh 3, Roshan Patel 4, Reena Ughreja 5 Abstracts: Today synthetic indicators are the choice of acid-base titrations. But due to environmental pollution, availability and cost, the search for natural compounds as an acidbase indicator was started. The present vocation highlights the exploit of the acidified ethanolic extract of the flowers of few medicinal plants as an acid-base indicator in acid-base titrations. This natural indicator is easy to extract as well as easily available. Promising results were obtained when it was tested against standard synthetic indicators. Titration shows sharp color change at the equivalence point. The equivalence points obtained by the flowers extract coincide with the equivalence points obtained by standard indicators. In case of weak acid and weak base titration, the results obtained by the flowers extract matched with the results obtained by mixed indicator. This natural indicator is found to be a very useful, economical, simple and accurate for the said titrations. Key Words: Acid-base indicator, Natural indicator, Anthocyanins, Titration.

INTRODUCTION The method of wet chemistry such as titrimetric analysis and gravimetry still has an important role in modern analytical chemistry. There are many areas in which titrimetric procedures are invaluable. The term titrimetric analysis refer to quantitative chemical analysis carried out by determining the volume of solution of accurately known concentration which is required to react quantitatively with a measured volume of a solution of the substance to be determined1. Indicators are dyes or pigments that can be isolated from a variety of sources, including plants, fungi, and algae. Almost any flower, for example, that is red, blue, or purple in color contains a class of organic pigments called anthocyanins that change color with pH. The use of natural dyes as acid-base indicators was first reported in 1664 by Sir Robert Boyle in his collection of essays Experimental History of Colors. Indeed, Boyle made an important contribution to the early theory of acids and bases by using indicators for the experimental classification of these substances2. Presence of color pigments was investigated as per IP and the tests are given in Table 1. Anthocyanins are characterized by Band275-280 nm (UV region). Actual color of 1Depatrment

of Pharmaceutics, Shree H.N.S.IP.E.R, Rajkot, 60002, Gujarat, India. E-mail:[email protected] *Corresponding author 2Department

of Pharmacology, Shri GM BILAKHIA College of Pharmacy ROFEL, Vapi, 396406, Gujarat, India.

3Department

of Pharmaceutical Chemistry, Innovative Groups of college, Delhi, 110001, India.

4Department

of Pharmacognosy, Shree L.P.T.P.Mahila College, Amreli, 364522, Gujarat, India.

5Depatrment

of Pharmaceutics, Smt. C. R. Gardi School of Pharmacy, 360002, Gujarat, India.

Inventi Rapid: Pharm Ana & Qual Assur Vol. 2011, Issue 2 [ISSN 0976-3813]

extract is depending on number and position of hydroxyl and methoxy group. When these are fixed, the color then depends upon the pH and solvent3. Bauhiniaa variegota Linn. Commonly known as kachnar belonging to Caesalpiniaceae, a medium-sized deciduous tree, found throughout India ascending to an altitude of 1300 m in the Himalayas, bark used in cough, bleeding piles, menorrhagia, skin diseases, diarrhea, flower with sugar is a gentle laxative[4,5]. The plant is also used in malaria and antidote in snake poison. Ipomoea Linn. Commonaly known as dudhiakalmi Belonging to family convolvulaceae, A large ornamental climber, introduce from tropical America in to India, and know cultivated throughout the warmer parts. The young leaves and fleshy calyas are used as vegetable. The plant yields a resinlike substance which coagulates castilla latex. The seed contain alkalodis, ipomine, lsoipomine, methoxyipomine, dimethoxyipomine, ipalkidinium, ipalbidin and ipalbine[4-6]. Cassia auriculata Linn. Commonly known as senna belonging to family Caesalpiniaceae, A tall much branched shrub used as laxative, purgative and in diabetes mellitus asthma ulcer, leprosy[4-6]. Solanum rostratum is a species of nightshade (genus Solanum) that is native to the United States and northern and central Mexico belonging to family solanaceae [7]. It seems that no work has been done on the suitability of Bauhiniaa variegota Linn., Ipomoea Linn., Cassia auriculata Linn. and Solanum rostratum as indicator in acid-base titration as compared to the relatively common Methyl Red and Phenolphthalein using acid-base titration. Hence the present vocation was attempted to appraise the flowers as a natural indicator. MATERIAL AND METHOD Material Fresh flowers were collected from the local market of Rajkot region, Gujarat, and they were authenticated from NISCAIR, New Delhi, Ref No: NISCAIR/RHMD/ Consult/ 2010-11/1468/69. All other ingredients were of analytical grade and purchased from Loba Chemie Pvt Ltd, Mumbai.

Method The flowers were cleaned by distilled water and cut into small pieces and macerated for two hours in 25ml of 90% ethanol. The extract was preserved in tight closed container and stored away from direct sun light [8]. The experiment was carried by using the same set of glassware’s for all types of titrations. As the same aliquots were used for both titrations i.e. titrations by using standard indicators and flowers extract, the reagents were not calibrated. The equimolar titrations were performed using 10 ml of titrant with three drops of indicator. All the parameters for experiment are given in Table 1. A set of five experiments each for all the types of acid base titrations were carried out. The mean and standard deviation for each type of acid base titrations were calculated from results obtained. The extract was also analyses for its λmax in Ultra Voilet range on Systronics single beam spectrophotometer (Shimadzu UV 1800).

RESULT The extract was found to contain compound anthocyanins as it gives blue color to aqueous sodium hydroxide solution, yellow orange color to concentrated sulphuric acid while red color which fed out on standing with magnesium-hydrochloric acid solution (Table 2). The flowers extract of B. variegota Linn., Ipomoea Linn., C. auriculata Linn. and S. rostratum showed λmax in Ultra Violet region (Table 3). The λmax suggested the presence of anthocyanins in the extract. The flowers extract was screened for its use as an acid base indicator in various acid base titrations, and the results of this screening were compared with the results obtained by standard indicators methyl red, phenolphthalein and mixed indicator [methyl orange: bromocresol green (0.1:0.2) results are presented in Table 4[9]. The titrations of strong acid with strong base (HCl & NaOH), strong acid with weak base (HCl & NH4OH), weak acid with strong base (CH3COOH & NaOH), and weak acid with weak base (CH3COOH and NH4OH) were carried out using standard indicators and flowers extract. The results of these titrations are given in Table 5,6,7,. It could be due to these flavonoids, the sharp end point appeared in the above mentioned titrimetric analyses. The Flowers extract of B. variegota Linn., Ipomoea Linn., C. auriculata Linn. and S. rostratum was found to have Poly-Phenolic, flavonoids, anthocyanins and is pH sensitive. The end point determination of acid base titrations by the traditional indicators, compared with flowers extract indicator, it was observed that traditional indicators gave incorrect results due to addition of excess of titrant (base) after the neutralization reaction was completed, but flowers extract indicator has given sharp end point because solutions give sharp color change at the equivalence points. 2011paqa142, CCC: $10 © Inventi Journals (P) Ltd Published on Web 27/05/2011, www.inventi.in

RESEARCH ARTICLE

Table 1: Standard chart for phytochemical identification Phytochemicals Color with aq. NaOH Anthocynins Blue violet Flavones Yellow Yellow to orange (cold) Flavonones Red to purple (hot) Isoflavones Yellow Leucoanthocyanins Yellow

Color with Conc. H2SO4 Yellow to orange Yellow to orange

Color with Mg-HCl Red (fades to pink) Yellow to red

Crimson Orange

Red, magenta, violet, blue

Yellow Crimson

Table 2: Technological characterization for analysis of chemical test. Poly-Phenolic compound Flavonoid Sample Color with Color with Color with aq. NaOH Shinoda test FeCl3 Lead acetate (Blue violet) II + + + + SRI + + + + CAI + + + + BVI + + + + +; Presence of compound

Yellow Pink

Anthocyanins Color with Conc. H2SO4 (Yellow orange) + + + +

Table 3: Determination of UV absorption Sample code II SRI CAI BVI

Table 4: Technological characterization of acid-base titration using standard indicator Titration (Titrant v/s Strength in moles Indicator Mean ±S.D.* Titrate) 0.1 MR 12.3±0.12 HCl v/s NaOH 0.5 MR 11.2±0.16 1.0 MR 11.2±0.15 0.1 PT 05.9±0.01 HCl v/s NH4OH 0.5 PT 06.6±0.08 1.0 PT 06.5±0.16 0.1 MR 12.0±0.11 CH3COOH v/s NaOH 0.5 MR 11.9±0.14 1.0 MR 12.0±0.09 0.1 MI 05.0±0.05 CH3COOH v/s NH4OH 0.5 MI 05.6±0.19 1.0 MI 06.1±0.17

Color with MgHCl (Red) + + + +

UV λmax 324 320 304 305 Color

pH

Yellow to pink Yellow to pink Yellow to pink Pink to colorless Pink to colorless Pink to colorless Pink to colorless Pink to colorless Pink to colorless Orange to green Orange to green Orange to green

12.32-5.77 12.55-4.87 12.63-3.30 10.50-6.74 10.61-8.28 10.98-8.29 12.33-6.01 12.56-5.96 12.67-5.99 03.25-4.52 02.81-4.68 02.86-4.73

*All values are mean ± S.D. for n=3, HCl: Hydrochloric acid, CH3COOH: Acetic Acid, NaOH: Sodium Hydroxide, NH4OH: Ammonium Hydroxide, MR; Methyl Red, MI: Mixed Indicator, PT: Phenolphthalein.

Table 5: Technological characterization of acid-base titration using B. variegota Linn. as indicator Titration (Titrant v/s Strength in Indicator Mean ±S.D.* Color Titrate) moles 0.1 BVI 08.5±0.17 Yellow to green NaOH v/s HCl 0.5 BVI 07.0±0.15 Yellow to green 1.0 BVI 06.0±0.16 Yellow to green 0.1 BVI 20.0±0.25 Yellow to green HCl v/s NH4OH 0.5 BVI 14.0±0.14 Yellow to green 1.0 BVI 18.5±0.41 Yellow to green 0.1 BVI 08.5±0.14 Yellow to green CH3COOH v/s NaOH 0.5 BVI 06.0±0.14 Yellow to green 1.0 BVI 06.5±0.14 Yellow to green 0.1 BVI 18.0±0.41 Yellow to green CH3COOH v/s NH4OH 0.5 BVI 16.5±0.31 Yellow to green 1.0 BVI 20.5±0.12 Yellow to green

pH 12.33-10.95 12.53-11.46 12.60-12.41 10.34-9.15 10.79-1.97 11.10-8.76 12.52-12.33 12.76-12.58 12.76-12.45 10.42-9.36 10.92-9.62 11.21-10.31

*All values are mean ± S.D. for n=3, HCl: Hydrochloric acid, CH3COOH: Acetic Acid, NaOH: Sodium Hydroxide, NH4OH: Ammonium Hydroxide, BVI: B. variegota Linn. Indicator.

Thus natural indicator employed in the acid base titrations was found economic, safe and an efficient alternative for traditional indicators. In comparison to this, chemical indicators were found more Inventi Rapid: Pharm Ana & Qual Assur Vol. 2011, Issue 2 [ISSN 0976-3813]

expensive and hazardous, which proves that Flowers extract of B. variegota Linn., Ipomoea Linn., C. auriculata Linn. and S. rostratum as a natural indicator is more worthy.

CONCLUSION The results obtained in all the types of acidbase titrations lead us to conclude that, it was due to the presence of flavonoids sharp color changes occurred at end point of the 2011paqa142, CCC: $10 © Inventi Journals (P) Ltd Published on Web 27/05/2011, www.inventi.in

RESEARCH ARTICLE

Table 6: Technological characterization of acid-base titration using I. Linn. as indicator Titration (Titrant v/s Strength in Indicator Mean ±S.D.* Titrate) moles 0.1 II 5.2 ± 0.18 NaOH v/s HCl 0.5 II 6.2 ± 0.13 1.0 II 4.6 ± 0.15 0.1 II 6.2 ± 0.16 HCl v/s NH4OH 0.5 II 3.2 ± 0.14 1.0 II 7.0 ± 0.15 0.1 II 5.4 ± 0.16 CH3COOH v/s NaOH 0.5 II 10.1 ± 0.13 1.0 II 7.7 ± 0.15 0.1 II 2.5 ± 0.16 CH3COOH v/s NH4OH 0.5 II 2.1 ± 0.14 1.0 II 7.4 ± 0.13

Color

pH

Yellow to colorless Yellow to colorless Yellow to colorless Yellow to colorless Yellow to colorless Yellow to colorless Pink to colorless Pink to colorless Pink to colorless Pink to colorless Pink to colorless Pink to colorless

12.82-13.35 13.03-12.83 12.92-11.80 11.06-1.22 10.22-1.18 11.68-6.64 6.62-6.62 12.75-11.86 12.73-7.41 10.62-8.7 10.7-8.02 11.2-5.02

*All values are mean ± S.D. for n=3, HCl: Hydrochloric acid, CH3COOH: Acetic Acid, NaOH: Sodium Hydroxide, NH4OH: Ammonium Hydroxide, II: I. Linn. Indicator.

Table 7: Technological characterization of acid-base titration using C. auriculata Linn. as indicator Titration (Titrant v/s Strength in Indicator Mean ±S.D.* Color Titrate) moles 0.1 CAI 09.0±0.11 Pink to colorless NaOH v/s HCl 0.5 CAI 07.5±0.19 Pink to colorless 1.0 CAI 07.5±0.19 Pink to colorless 0.1 CAI 14.0±0.16 Pink to colorless HCl v/s NH4OH 0.5 CAI 13.0±0.19 Pink to colorless 1.0 CAI 14.0±0.17 Pink to colorless 0.1 CAI 09.0±0.11 Pink to colorless CH3COOH v/s NaOH 0.5 CAI 06.5±0.37 Pink to colorless 1.0 CAI 06.0±0.12 Pink to colorless 0.1 CAI 17.0±0.17 Pink to colorless CH3COOH v/s NH4OH 0.5 CAI 12.0±0.16 Pink to colorless 1.0 CAI 13.0±0.31 Pink to colorless

pH 12.38-6.33 12.53-5.77 12.66-2.61 10.26-2.78 10.82-1.58 11.11-1.94 12.46-7.82 12.74-8.64 12.81-7.08 10.49-5.68 11.02-7.02 11.36-6.44

*All values are mean ± S.D. for n=3, HCl: Hydrochloric acid, CH3COOH: Acetic Acid, NaOH: Sodium Hydroxide, NH4OH: Ammonium Hydroxide, CAI: C. auriculata Linn. Indicator.

Table 8: Technological characterization of acid-base titration using S. rostratum as indicator Titration (Titrant v/s Strength in Indicator Mean ±S.D.* Color Titrate) moles 0.1 SRI 03.0 ± 0.21 Colorless to yellow NaOH v/s HCl 0.5 SRI 04.5 ± 0.18 Colorless to yellow 1.0 SRI 04.0 ± 0.16 Colorless to yellow 0.1 SRI 10.0 ± 0.13 Colorless to yellow HCl v/s NH4OH 0.5 SRI 17.0 ± 0.17 Colorless to yellow 1.0 SRI 14.0 ± 0.11 Colorless to yellow 0.1 SRI 03.0 ± 0.16 Colorless to yellow CH3COOH v/s NaOH 0.5 SRI 04.0 ± 0.12 Colorless to yellow 1.0 SRI 01.5 ± 0.14 Colorless to yellow 0.1 SRI 08.0 ± 0.17 Colorless to yellow CH3COOH v/s NH4OH 0.5 SRI 12.0 ± 0.12 Colorless to yellow 1.0 SRI 12.0 ± 0.14 Colorless to yellow

pH 12.61-9.31 12.65-11.68 12.80-12.44 10.56-8.77 11.06-9.90 11.38-8.95 12.65-9.60 12.65-9.86 12.85-12.08 10.52-9.2 11.4-9.56 11.23-10.37

*All values are mean ± S.D. for n=3, HCl: Hydrochloric acid, CH3COOH: Acetic Acid, NaOH: Sodium Hydroxide, NH4OH: Ammonium Hydroxide, SRI: S. rostratum Indicator

titrations. We can also conclude that, it is always beneficial to use B. variegota Linn., Ipomoea Linn., C. auriculata Linn. and S. rostratum flowers extract as an indicator in all types of acid base titrations because of its economy, simplicity and wild availability. REFERENCES AND NOTES

1. Mendham J, Denney RC, Barness JD, Thomas M. Vogels. A Text Book of Quantitative Chemical Analysis. 6th ed. New Delhi (INDIA); 2004. 2. Anonymous. Indian Pharmacopoeia. Vol-II. New Delhi (INDIA): Drug Controller of India; 1996.

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3. Agarwal OP. Chemistry of Organic Natural Products. Vol-II. Meerut (INDIA): Goel Publishing House, Krishna Prakashan Media (P) Ltd; 2004. 4. Anonymous. The wealth of India. Publication and information Directorate (CSIR). New Delhi; Vol-II (B), Vol-III (D-I), Vol-I (A-CI), 1992. p.57, 337-348,222. 5. Nadkarni KM. Indian medicinal plants and drugs with their medicinal properties and uses, Vol-I, Popular Prakashan, Mumbai, 2009. p. 183-184, 284-285, 684-694. 6. Kritikar KR and Basu BD. Indian Medicinal Plants. Vol.-III, 2nd edtion, International Book

Distribution, Dehradun, India, 2006;. p.354, 659-667. 7. Wikipedia free encyclopedia [homepage on the http:// en. Internet]. Available from: wikipedia.org/wiki/Solanum_rostratum [CITED ON 2011/MAY] 8. Patil Sandeep B, Kondawar MS, Ghodke DS, Naikwade NS, Magdum CS: Use of Flower Extracts as an Indicator in Acid-Base Titrations, Research J. Pharm. and Tech., 2009. 2(2): 421-22. 9. Wikipedia free encyclopedia [homepage on the Available from: http://en. Internet]. wikipedia.org/wiki/PH_indicator/.htm [CITED ON 2011/MAY]

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