Separation of an APC mixture. A quantitative analysis experiment

Paul Haddad and Malcolm Rasmussen Australian National University P.O. Box 4. Canberra A.c.T.. 2600. Australia

Separation of an APC Mixture A quantitative analysis experiment

In the search for relevant and interesting experiments for chemistry students, drugs have frequently found use as the suhiect ~, of exoeriments desiened to instruct the student in various chemical techniques.' Since students can readily oerceive the relevanre otdrurs " .(used here in its widest sense) io modern society, their interest is more easily maintained throughout what might otherwise prove to he a dull exercise. In this paper the well known technique of pH controlled extractive separation of a mixture of an acidic, basic, and neutral organic substance has been applied to separation and analysis of a mixture of the drugs aspirin (acidic), caffeine

(basic), and phenacetin (neutral). This experiment, which occupied two 3%-hour laboratory sessions, was included in first vear (freshman) chemistry courses for both science and nonscience majors and was intended to instrurt students in the use oi the techniquesof liquid-liquid extraction, distillation, and melting point determination, as well as providing an introduction into the use of infrared and ultraviolet spectroscopy. Background information on each of these topics was 'Lieu, V. T., J. CHEM. EDUC.,48,478 (1971). Thasar, D. W., and Tath, G.B., J. CHEM. EDUC.,51,22 (1974). 3Lane, S. R., and Stewart, J. T., J. CHEM. EDUC., 51, 588 (1974).

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APC Mixture

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Dissolve in 50 m i CHCI, Extract with 25 m l 4 M HCl (twice)

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Asueous Phase ("Caffeine Extract")

Organic Phase

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Extract with 2 0 ml CHCI,

Aqueous Phase

Organic Phase

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Add 5M NaOH until alkaline

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Extract with 1 5 ml CHCI, (twice)

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Extract with 2 5 ml0.5M NaHCO,

Organio Phase LLPhenaeetin kxtraot*.)

Aqueous Phase ("Aspirin Extract")

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Add 5M HCl until acidic

Dry with snhyd. N+O,

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Distil off'CHC1,

Extract with 20 ml CHC1. d here since the slightly acihic paracetarnol is not extracted hv sodium bicarbonate and therefore behaves in the same manner as phenacetin. Additionally, replacement ot caffeine hv codeine dues not affect the ~ r o c e d u r ealthoueh . a different wavelength is required for thespectrophbtomet& determination.

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4Powdersare more easy to handle than pills since the latter contain a hinder and require grinding before analysis. The analysis procedure is, however, quite applicable to pills. Jones, M., and Thatcher, R. L.,Anal. Chem., 23,957 (1951).