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Chemistry 5

The Art and Science of

Chemical Analysis

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Introduction to Chemical

Analysis• Chemical analysis includes any aspect of

the chemical characterization of a sample

material.

• Analytical Chemistry?

 – “Science of Chemical Measurements

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Areas of Chemical Analysis and

!uestions They Ans"er • !uantitation#

 –  $o" much of su%stance & is in the sample?

• 'etection# –  'oes the sample contain su%stance &?

• Identification# –  (hat is the identity of the su%stance in the sample?

• Separation# –  $o" can the species of interest %e separated from the

sample matri) for %etter *uantitation and identification?

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(hat do Chemical Analyst 'o?

• Analyst#

• Applies +no"n measurement techni*ues to

"ell defined compositional or

characterization *uestions.

• ,esearch Analytical Chemist

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(hat do Chemical Analyst 'o?

• Senior Analyst#

• 'e-elops ne" measurement methods on

e)istin principles to sol-e ne" analysis

 pro%lems.

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(hat do Chemical Analyst 'o?

• ,esearch Analytical Chemist#

• Creates and /or in-estiates no-el

techni*ues or principles for chemicalmeasurements.

• or 

• Conducts fundamental studies ofchemical/physical phenomena underlyinchemical measurements.

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(hat is Analytical Science?

• Analytical Chemistry pro-ides the methods andtools needed for insiht into our material "orld0

for ans"erin four %asic *uestions a%out amaterial sample?

• (hat?

• (here?

• $o" much?• (hat arranement1 structure or form?

• 2resenius3 4. Anal. Chem. 6 7899:;#<8:=<8

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  ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)

Qualitative analysis is what.

Quantitative analysis is how much.

Qualitative analysis is what.

Quantitative analysis is how much.

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  Fig. 1.1. Steps in an analysis

An analysis involves several

steps and operations which

depend on

•the particular pro!lem

• your e"pertise

• the apparatus or

e#uipment availa!le.

$he analyst should !e

involved in every step.

An analysis involves several

steps and operations which

depend on

•the particular pro!lem

• your e"pertise

• the apparatus or

e#uipment availa!le.

$he analyst should !e

involved in every step.

 ©Gary Christian,Analytical Chemistry, 6th

Ed. (Wiley)

 

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%i&&erent methods provide a ran'e o& precision, sensitivity, selectivity,

and speed capa!ilities.

%i&&erent methods provide a ran'e o& precision, sensitivity, selectivity,

and speed capa!ilities.

 ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)

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$he sample sie dictates what measurement techni#ues can !e used.$he sample sie dictates what measurement techni#ues can !e used.

 ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)

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Trainin of Chemical Analysts

7Analytical Chemists;• Trainin focuses on principles and

techni*ues for sol-in measurement

 pro%lems 0 %ut0

• Chemical analysts interface multiple

disciplines to the solution of chemical

measurement pro%lems – >hysical=1 oranic=1 inoranic=1 %io=chem=1

 physics1 math1 %ioloy1 electronic1 computers

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Chemistry 5

Trainin 2ocuses on• nderlyin principles of chemical

measurements 7 interatin all chemistry

fields1 math1 physics1 %ioloy1 electronics1and computers;.

• 'e-elopin proficiency "ith *uantitati-eanalysis la%oratory procedures

• @)posure to role of chemical analysis in a %road rane of modern science.

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Chemical Analysis Affects Many

2ields• >hysical=1 ranic=1 01 Chemistry#

 – “Theory uides %ut @)periment decides

• Biotechnoloy# – 'istinuishin isomers "ith differin

 %ioacti-ities.

 – Biosenors• Materials Science#

 – $ih=temperature superconductors

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Chemical Analysis Affects Many

2ields• Manufacturin#

 – !uality control of pac+aed foods

specifications

• 2orensics#

 – Chemical features for criminal e-idence

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,ole of Analytical Chemistry in

Modern Science• Case Study 8.

•  uclear (aste

'isposal –  uclear >o"er >lants

 –  uclear ,eactors

 –  (eapons >rocessin

 –  (eapons 'isposal

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Nuclear Waste Disposal Case Study

One Disposal Plan:

seal waste in corrosion-resistant containers

bury 1000’s of feet underground roc!y

strata abo"e water table#

$ust re%ain contained for& '0(000 years

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Nuclear Waste Disposal Case Study

• Technical >ro%lems#

• Metal >ac+ae Corrosion#

 – M D "ater1 o)yen1 o)idizersM ions D

 products

To human

"atersupplynderround

"ater 

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Nuclear Waste Disposal Case Study

• ,epository a%o-e "ater ta%le1 %ut some "ater

 present

• Model e)ists for chemical reactions1 rates1 andtime=dependent dispersion of products and "aste

• >redicted containment time depends on -ery

accurate measurements of microscopic corrosion

 processes o-er short periods 7"ee+s1 months;

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Nuclear Waste Disposal Case Study

• Corrosion $odel:

• M D $:1 S6:=1 :  MD D $= 1 $:

• CE1 $D1 2=1 Cl=1 M&nD #

•  :=1

=1 SE1etc.MFmD1 MGH D >rod.

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Nuclear Waste Disposal Case Study

• (hat 'o (e eed To no"?

• Ja%oratory Simulation Studies

• (ater Composition at site %efore container placement.

• (ater Composition after e)posure to container 

 –  )i%e dependence rate of product growt* o"erwee!s+%ont*s#

 –  S%all c*anges %ust be %easured "ery precisely 

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues#• (hat species to %e measured?

• (hat precision is re*uired?

• (hat measurement techni*ue?

• (hat are the sources of error?

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues#• @)ample# C

E  Analysis

• Species? CE1 $C

=1 $:C ?

• >recision?D/= 7 K.8L1 K.K8L1 8KL;• Techni*ue?

 –  D/= 8=:L Ion Chromatoraphy

 –  D/= K.8L Acid=Base Titration

• @rror Sources? –  Acid=Base 7ther Bases Interfer;

 –  Ion Chromatoraphy 7p$ – 'ependent ,esults;

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues#• (hat Car%onate Species?

• CE  D $: $C

= D $=

• $C=  D $: $:C D $=

• $:C C:7; D $:

• Temperature1 >ressure 'ependence

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues#• If eed C

EN only

 – Specify p$1 Temperature1 >ressure

 – se Techni*ue Selecti-e for CE 

• 7Ion Chromatoraphy;

• If eed Σ [CEND $C

=N D $:CN

 – ,emo-e Interferences

 – Acid=Base Titration

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues# (hat car%onate species is present as a

function of p$?

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues# 7Cont.;• ther Chemical Measurements#

• Chromium# Cr :D1Cr D1 Cr :OE1 Cr6

E1 etc.

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues# 7Cont.;• (hat does the Analytical Chemist need to

+no" to sol-e these pro%lems?

• Measurement Techni*ues A-aila%le – Titrations1 ptical Spectroscopy1

ChromatoraphyP etc.

• Strenths/(ea+nesses of Techni*ues – Accuracy1 >recision1 Interferences1 ,ane1

'etection Jimits1 etc.

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 uclear (aste 'isposal Case Study

Analytical Chemistry Issues# 7Cont.;• nderlyin Chemistry/>hysics of the

Sample Material

 – Solution Chemistry 7Acid/Base;

 – Solids $omoeneity1 Structure

• @rror Analysis

 – Sources

 – Solutions

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'eer ill

• Case Study Q :# 'eer ill

• >ro%lem# 'ead "hitetail deer near pond in

the Jand Bet"een the Ja+es State >ar+ insouth central entuc+y.

• Chemist state -eterinary dianostic

la%oratory helped find the cause

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Site In-estiation

• Careful -isual o%ser-ation of a t"o acre

area around the site#

• %ser-ation# rass around near%y po"er= poles "as "ilted and discolored.

• Speculation# $er%icide used on rass.

• Inredient# Arsenic in a -ariety of forms

 – C$As7$;: -ery solu%le in "ater.

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Select Method

• Association of fficial Analytical Chemists

7AAC;

• 'istillation of arsenic as arsine "hich isthen determined %y colorimetric

measurements.

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,epresentati-e Sample

• 'issect %oth deer. ,emo-ed +idneys for

analysis.

• Ja%oratory Sample. >reparation

• Cut +idney into pieces and %lend in a hih

speed %lender to homoenize the sample.

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'efinin ,eplicate Samples

• Three 8K= samples of the homoenized

tissue "ere placed in porcelain curci%les

and dry ashed. 'ry ashin ser-es to freethe analyte from oranic material and

con-ert the arsenic present to As:5.

Samples of the discolored rass "eretreated in a similar manner.

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'issol-in the Samples

• The dry solid in each of the sample

cruci%les "as dissol-ed in dilute $Cl1

"hich con-erted the As:5 to solu%le$As6.

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@liminatin Interferences

• ,eactions to @liminate Interferences#• $5As6 D SnCl: D :$Cl ==R $5As5 D SnCl: D $:

• $5As5 D Gn D $Cl ==R As$57.; D GnCl: D $:• Bu%%le as into collectors "ith sil-er

diethyldithiocar%amate to form a colored comple)

compound sho"n %elo".

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Measurin the Amount of

Analyte• Spectrophotometer# $ihly colored

comple) of arsenic "as found to a%sor%

liht at a "a-elenth of 55 nm.

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A!sor!ance vs Concentration

y = 0.0282x + 0.005

R2 = 0.9961

0

0.2

0.4

0.6

0.8

0 5 10 15 20 25 30

Conc., ppm

    A    !   s   o   r    !   a

   n   c   e

Conc. Absorbanc

ppm

0 0

5 0.16

10 0.28

15 0.41

20 0.595

25 0.7

deer 1 0.61

deer 2 0.43

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Calculatin the Concentration

•  ppm E 7A%sor%ance =.KK5;/K.K:<:

• 'eer 8# 7K.8 = K.KK5;/K.K:<: E :: ppm

• 'eer :# 7K.6 =K.KK5;/K.K:<: E 85 ppm

• Arsenic in the +idney tissue of animals is

to)ic at le-els a%o-e a%out 8K ppm.

• rass Samples sho"ed a%out KK ppm

arsenic.

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,elia%ility of the 'ata

• The data from these e)periments could %e

analyzed usin the statistical methods "e

"ill descri%e in Section .

W* D W , i

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W*ere Do We ,egin• ,e-ie" of Basic Tools and perations of Analytical

Chemistry

 –  The Ja%oratory ote%oo+  –  Analytical Balances1 Uolumetric lass"are

 –  Ja%oratory Safety

• @rror Analysis

 –  Concepts

 –  Terminoloy

 –  @-aluation of 'ata

 –  @)perimental 'esin

• ,e-ie" of Solution Chemistry –  nits

 –  Concentration Calculations

 –  Stoichiometry

 –  Balanced Chemical ,eactions

a!oratory sa&ety is a must*

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a!oratory sa&ety is a must*

earn the rules.

+ee Appendi" %.

a!oratory sa&ety is a must*

earn the rules.

+ee Appendi" %.