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In th e search for relevant and interest ing exper iments for (basic), and phenacetin (neutral) . This exper iment, whichchemistry s tudents , drugs have f requently found use as th e occupied two 3% -hour labo ratory sessions, was included insuhiect of exoer iments desiened to instruct the s tud ent in first vear (freshman) chem istry courses for bot h science an d

Paul Haddadand Malco lm RasmussenAustralian National UniversityP.O. Box 4. CanberraA.c.T.. 2600. Australia

~,various chemical techniques.' " Since s tude nts can readily nonscience m ajors and was intended to instrur t s tud ents inoerceive the relevanre ot dr ur s (used here in its widest sense) the use oi the techniquesof l iquid- l iquid extract ion, dist i l la-

Separation of an APC MixtureA quantitative analysis experiment

" .io modern society, their interest is more easi ly maintained tion, and melt ing point de termination, as well as providingthroughout w hat m ight otherwise prove to he a dull exer- an introduction into th e use of infrared and ul traviolet spec-cise. troscopy. Background information on e ach of these topics wasIn this pap er the well known techniqu e of pH controlled 'Lieu, V. T.,J. CHEM. EDUC.,48,478 (1971).extractive separation of a mixture of an acidic, basic, and Thasar , D. W., and Tath ,G. ., J. CHEM. EDUC.,51,22 (1974).neutral organic substance has been applied to separation and 3Lane, S. R., and Stewart, J. T., J. CHEM. EDUC., 51 , 588analysis of a mixtu re of the drug s aspirin (acidic), caffeine . (1974).APC Mixture

IDissolve i n 50 mi CHCI,I

Extract with 25 ml 4M HCl (twice)

1Asue ous Phase ("Caffeine Extract ")

IOrganic Phase

I IExtract with 20 ml CHCI, Extract with 25 ml 0.5M NaHCO,

Aqueou s Phase Organic Phase Organio Phase LLPhena eetin Aqueou s PhaseI kxtraot*.) ("Aspirin Extract ")I II Dry with snhyd. N+O, IAdd 5M HCl untilI acidicAdd 5M NaOH until alkaline 1I Distil off'CHC1,Extrac t with 1 5 ml CHCI, (twice) II Weigh Residu e

Extract with 20 mlCHC1.

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provided prior to th e comm encement of the labora tory seea ion. and discard th e aqueoua phase.Dry the combined organic extract withThi s experiment form ed par t of a sho rt series of ass ignments a little anhydro us NaaSOd and filter it into a 100-mlvolumetric flask,designed to familiarize th e stud ent w ith basic organic thoroughly washing the filter pap er with abo ut 50 ml of chloroform.is t ry techniques . Dilute to the mark w ith chloroform.Record the uv absorption sp ectrum of this solution and compareExperimental Procedure the height of the caffeine peak at 275 nm with a previously prep iredcalibration curve (this was supplied to the s tude nts), thereby dete r-Com mercial analgesic po wders4 containing 500mg mining the am ount of caffeine present. T he presence of myphenac-250 mg phe na c e t in , a nd 150 mg c a ffe ine c i t r a t e we re i s s ue d ,tin remaining in the sample can be detected by the app earance oft o s t u d e n t s . T h e u s e o f b r a n d s w h ic h e m p l o y a d y e i n t h e a peak or shoulder in the curve a t 250m (th e wavelength of m axi-powde r to f a c i l it a t e h ra nd ide n t i fi c a t ion s hou ld be a vo ide d mum absorption of phenacetin). The uvspectra of aspirin, phenacetin,where poss ible because of th e necess i ty to extra c t th e dye in and caffe ine are inc luded in a paper by Jones and Th a t ~ he r . ~~ ~orde r t o p re ve n t e r ro r i n the qua n t i t a t ive a na lys i s o f t he andldenrificationof Phenacetinpowder.T he s tude nts were g iven the fo llowing ins t ruct ions together Dry the "Phenacetin Extract" (which contains the hack-extractedwi th t he a c c ompa ny ing f low s he e t. phenace tin from the "Caffeine Extract") with a little anhydrousNalS01. Filter the solution into a preweighed round bottom flask

Select a powder from those available and note the hrand. Accuratelyweigh the powder and transfer i t to the separating funnel providedusing 50 ml of chloroform to ensure complete transfer. Extract thissolution w ith 25 ml of 4 M HCl, separate the aqueous (upper) ayer,and return the chloroform layer to the separting funnel. Repeat theextraction using a further 25 ml of 4MHCI and combine the aqueousextracts. re torn in^ th e c h l ~ m f o m~ V P I o the srnarntine funnel. The

containin ga few boilingehips, washing the filter paper with 10m lofchloroform. Distil to dryness on a water bath, dry the flask, andreweigh to determ ine the weight of recovered phenacetin. Ob tain theinfrared spectrum of the phenacetin and the melting point andcommare these with oublished data.Calcula te rhe perrentaye recoveryofeach o fthe rhre e components,osplrm, phenacetln, and ~ a l l r l n erom the analgealc powderset aside. T he e xpe r im e n t r e qu i res a f a i r de g ree o f c a re a n d ma n i -Extract the chloroform solution twice using 25-ml portions of 0.5 pulative skill fo r successful results, bu t in the hands of anM NaHCO aand combine theaqueous extracts, labeling them "AspirinExtract." Store the chloroform solution in anothe r flask and label it experienced recoveries for each component can"Phenacetin Extract." he cons is tent ly achieved; accordingly a leve l of 85% ecovery

wa s c ons ide re d a s good fo r s tude n t s .Isolation and Identification of Aspirin T h e m a i n e r ro r s d is o la v ed h v 3 00 s t u d e n t s w h o ~ e r f o r m e d. .Transfer the solution labeled "Aspirin Extract" to a separating th e e xpe r ime n t i nc lude d in s u f f i ci e n t s ha k ing t im e fo r e x -funnel using a little distilled water to en sure a quantitative transfer. t r a c t ions (a bou t 1 mi n i s r e ou i red ) . i na c c u ra t e d i lu t ionsAcidify this solution with the minimum amount of 5 M HC1, gentlyshaking the funnel after each addition of acid to remove any COzproduced. E xtract the solution using 20 ml of chloroform and repeatwith a further 15 ml of chloroform. Combine the two organic extractsand discard the aqueous phase.Dry the organic extracts with a little anhyd rous NazSOd and filterthe solution through glass wool into a pre-weighed round bottom flaskcontaining a few bailing chips (these chips should be weighed withthe flask), washing the glass wool thoroughly with 10 ml chloroform.Distil the solution to dryness using a water bath , dry th e outside ofthe flask carefullv. and reweigh to determ ine the weiaht of asoirinrecovered from the sample. obtain the melting poind here s ince the s l ight ly ac ihic parace tarnolis not extrac ted hv sodium bicarbonate an d therefore behavesin the sam e mann er as phenacet in . Addi t ional ly , replacementot caffeine hv c ode ine due s no t a f fec t t he ~r oc e d ur e . l t houe ha different wavelength is required for thespectr ophb tom et&de te rmina t ion .4Powders are more easy to handle th an pills since the latter containa hinder and require grinding before analysis. The analysis procedureis, however, quite applicable t o pills.Jones, M., and Thatcher, R. L.,Anal. Chem.,23,957 (1951).

732 / Journal of Chemical Education