Chemical Separations: Principles, Techniques and Experiments (Techniques in Analytical Chemistry)

767 Pages·1999·129.46 MB·English

by  Clifton E. Meloan

Chemical Separations
Principles, Techniques, and Experiments
Clifton E. Meloan
Kansas State University
Manhaltan. Kansas
AWiley-Interscience Publication
JOHN WILEY & SONS, INC.
NewYork I Chichester I Weinheim I Brisbane I Singapore I Toronto
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DedicatedTo
Mr. Paul Bacher
My High School ChemistryTeacher
Burlington Senior High School
Burlington, Iowa
11leone whostarteditall

ABOUT THE AUTHOR
Clifton E. Meloan is professorofanal)1ical chemistry at Kansas State Univcrsicy, Manhattan, KS 66506,
and was ScienceAdvisortotheFoodandDmgAdministrationfor28years,mostlyassociatedwithIheTotal
Diet Center in Lenexa, KS. He was also consullam for several industries. He received a B.S. degree in
chemical technology from Iowa Siale University in 1953 and a Ph.D. in analytical chemistry from Purdue
University in 1959.Hehasdirectedlheresearch0(50Ph.D.and26 M.S. students.Theareasofresearch in
cluded extraction mechanisms, reactive column gas-liquid chromatography, polymers to remove selected
ions from polluted \vater, solid reagents to selectively delecttoxic compounds. criminalistics, insect detec
tion ofchemicals. and making undergraduatechemistry laboratories real world. This research has resulted
inover 160papers inrefereedjournalsand I patenl Hehasprepared II videotapeson laboratorytechnique
fortheAmericanChemical Societyand26hoursofvideoonbasicchemistryfortheUSDA Food Safetyand
InspectionService. Heisthesoleauthoroffivebooksandtheco-authorofsevenbooks,thetwo mostfeCeni
beingFoodAnalysis:TheoryandPracticebyY. PomeranzandC. E. Meloan,Chapman-Hall (1994) and the
CentralAmerican Pesticides LaboratoryTraining Manual published by the A.G.A.C. International (1996).
Inadditionhe hascontributed22chapters to3otherbooks. Hewas selectedas Distinguished Research and
Teaching Professor in 1970sponsored by the Standard Gil Co. l-Ie has twice been selected as Outstanding
Educator in America and in 1995 was awarded the first Kansas Slate University Distinguished Teaching
Chair.
vii

PREFACE
Pickandchoose.
Coverwhatyoucan in lecture.
dotheexperimentsyouhavethetimeandapparatus for,
and Icavethe reS[ forreference.
The purposes ofthis book are to present the principles ofoperation ofthe mostcommonly used chemical
separations, to describe the apparatus that is used, and toprovidean expcrilTlCfll to illustrate the techniques
requiredtoperformeach separationcorrecdy. Thesamples usedarecommercial products and naturallyoc·
curringmaterials.'Themcthodsare, farthemostpart.official methods from theA.HOCia/iona/OfficialAna~
lyticalChemists. International(AOAC. Inti.);the UnitedStatesPharmacopeia(USP); theAmericanSociety
forTe.ffingandMaterials(ASfM); and from universityand induslriallaboratories.
Most students do not know "what is available" to solve a separation problem and usually do not
knowhowtodoil.Thislexlisintendedtobe"streetsmart"byincorporatingairthemanipulativetechniques
practicingchemists usetomaketheseparation work well. farmore separationsaredescribed here thancan
be covered inaone-semestercourse,butthisbook is intendedtoserveasa reference fortheremainingsep
arations.The mathematical treatment is kept toa minimum, presenting on1)' what is necessary to illustrate
theprinciplesand toshowhowquantitationand recoveriesaredetermined. Individual instructorswill surely
supplementthetheor)'basedontheirinterests.
Students rna)' select 14 experiments from about 30 available, or about one per week. The expcri·
ments areset up 5--6at a time for 2-2.5 weeks. II is the responsibility ofthe student todo theexperiments
within thattime.Thedirectionsaretaperecordedsostudentscanworkatanytime. Laboratoryassistantsare
available at certain times, and although the studentsare encouraged to take advantage ofthose times, it is
not mandatory. Safcty in anopen laboratory isalwa),saconcern. Mostoflheseexperimentshave beendone
for several years and the lab is believed to be very safe. Theopen laboratory is necessary with real·world
samplesbecause it isnotalwayspossible10finish a labin3 hours.Theauthorbelievesthatlearning howto
solveaproblem is moreimportantthan beingrestrictedtoJ hours.
In 1966, the author became a science advisor for the fDA. II took about 20 minutes in one ofthe
field laboratories to convince him that allhough he probably knew more thcory than anyone there, he had
been inadequately trained in the practical aspects ofhandling real-world samples. Subsequent visits to in
dustrial laboratories as a consultant reinforced this belief. furthcnnore, the author realized that he was
teaching his students the way he had been taught As a result, a course in separations was developed in
which commercial products, natural samples,and official methodsofanalysisprocedures "",ould be usedas
much as possible. All ofthe laboratory techniques thaI the authorhas learned are being passed on to stu·
dentsby incorporatingthem intothedirectionsoftheexperimems.
Students should know the basic principles and have actual practice with the operational techniques
ofa wide varietyofseparation methods. Inaddition,rheyshould be familiar with agreat man)'othermeth
ods ofseparation Ihat may be useful in the future. This book includes far more experiments than anyone
studentcanbeexpected10do inaone·semesterclass.Thepurposesofthisare
" Preface
I. Studentscanselect a wide varietyofexpcriments todobased on theirpast experienceand inter
ests.
2. SlUdentscan readily learnsomethingabout aseparation they arc unfamiliarwilh and haveanex
periment totry iftheydesire.
3. Because studentscan learn many ways toseparatea mixture.theyareless likelyto force an inef
ficient methodofseparation asa solutiontoaproblemjustbecause it istheonlyonethey know.
T\WO pointsofcaution:
I. The student is using real samples, strange equipment. and many new techniques all at the same
time. Itis unrealistic toexpect that the anal}1ical resultson first trywillbe perfect,buttheyusu
allywill beacceptable.
2. Separation is notnot spelled sep£.ration.
Anexperimentwithdetaileddirectionsaccompanieseachseparation scheme. Instructorsmust know
whatapparatus isneeded,how it is set up. whatsolutionsare required, strength ofsolutions,and howmuch
toprepare for each student. particularly ifteachingassistantsareinvolved.
The fonnat for each experiment is to provide first a briefsummary ofthe principles involved. A
problem is presented that requires a separation 10 be made. A list ofall ofthe equipment needed for one
completesetup isprovided.Alistofall chemicalsandsamplesneeded isprovidedwiththeamount foreach
student (5) listed attheend suchas 15mUS. Inthe author's laboratory, eachexperiment is availableon au
diotapesostudentscan proceedat theirown pace. It isimperativethattheapparatusbeSet up to follow the
directions. That is one ofthe purposes ofthe apparatus diagram. The second reason is sothat students can
recognize theexperimentsetupwithoutbeingembarrassedbecausetheydidn', knowwhat it looked like.
A one paragraph summary ofwhatis tobedonegivesthe studL'Tl1 a broadviewofwhat isexpected.
Italsoprovides the instructorwith a quick review ofthe separation so ifa question is asked, the instructor
can quicklyprovideananswerora~uggestion.
Thedirectionsarcdetailed. It iscookbook.and intentionallyso.ThisisnotChem Iwithbeakersand
testtubeswhere"discovery"isparamountand theapparatus isincxpcnsive.1hescseparations involvealim·
ited amount ofexpensive equipment. and good techniques arc to be learned. In addition. when rcal-",:odd
samples are used, the experiments can take considerable time, sodirections are necessary. Unless students
areshownwhat good techniqueis, they will seldom learn iton theirown. and unlesstheyarcshown howto
takecareofan instrument, itwill bea"machine"andtreatedasroughly.
Ifan instrument suchasan infraredis used,general directionsaregiven10showwhatisneeded. It is
expectedthat the local instructorswill make modifications for theirparticularinstruments.Anexamplecal·
culalion is provided I'll lhe end.Thesamples often smell. won'tdissolve.are messy. and havemany imerfer
ingsubslanccs present. However. lhat is realityaftergraduation.soit isbesttogetusedto it flOW.
This text has been used wilh both undergraduate and graduate classes. Undergraduate students
shoulddo thoseportions assigned by theirinstructorandasmany others astheirinterest dictates. Graduate
studentsshouldbegin with newmaterialandcontinueon.
ACKNOWLEDGMENTS
Eileen Schofield, Senior Edilor, Kansas State Agricultural Experiment Station, for editing the manuscript.
Justin Vardeman. Manhattan. Kansas, Vocational Technical Institute, for the following drawings: Figures
2.3,2-11.2·\4.2-25,3·8,7·1.7.19.8·14.11.1.12·7,13-4, 20-5 and 20-8. Kelly Johnson. Kansas State
University. Architectural Engineering, for the following drawings: Figures 1-4,5-1.7-6,7-9,7-10.7.14.
9-3.9-7,10·10.11-3.12-2.21-4,23-11,26-15,27-8. 29-1. 29·3. 29-8. 29-12. 29·14, 29-19, 29-21. 30-2,
34-1,36-20.43-1.53-3,56-3,and56-15.
Clifton E. Melean
Kan.~asStnte University
CONTENTS
Introduction
SEPARATIONS INVOLVING PHASECHANGES
I Volatilization 5
2 ZoneMelting 13
3 Distillation: Generallnfonnation 21
4 Azcotropicand Extractive Distillations 43
5 Steamand ImmiscibleSolvents Distillation 49
6 Vacuum Distillation 57
7 MolecularDistillationandSublimation 71
8 Lyophilization(Freeze Drying) 85
SEPARATIONS INVOLVING EXTRACfION
9 Extraction: GeneralConcepts 93
10 Continuous Extraction 107
11 Countercurrent(Extraction)Chromatography:The1toCoil-PlanetCentrifugal Extractor 117
12 Solid Phase Extraction 129
13 Supcrcritical FluidExtraction 137
SEPARATIONS INVOLVINGCHROMATOGRAPHY
14 Chromatography:GeneralTheory 149
15 Displacement and MuhiplcColumn Partition Chromatography 155
16 AffinityChromatography 165
17 Size Exclusion Chromatography (Gel Filtration;Gel Permeation) 171
18 FlashChromatography 179
19 t-ligh Perfonnance LiquidChromalography(HPLC) 183
20 Gas-Liquid Chromalography (GLC) 211
21 PapcrChromatography 249
22 Thin LayerChromalography 255
SEPARATIONS INVOLVING ION EXCHANGE RESINS
23 Ion Exchange 269
24 Ion Chromalography 277
2S Ion Retardation, Ion Exclusion, and Ligand Exchange 289