Quality Assurance Quality Control_Lecture3

8/9/2019 Quality Assurance Quality Control_Lecture3

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Quality AssuranceQuality Assurance

andand

Quality ControlQuality Control

HilarioHilario S.S. TabernaTaberna Jr.Jr.

Department of ChemistryDepartment of ChemistryCollege of Arts and SciencesCollege of Arts and Sciences

University of the PhilippinesUniversity of the Philippines VisayasVisayas

MiagMiag--aoao, Iloilo, Iloilo

First Semester, A.Y. 2009First Semester, A.Y. 2009 -- 20102010


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Steps of Analytical Process:Steps of Analytical Process:

PlanningPlanning--SamplingSampling--AnalysisAnalysis--ReportingReporting

The final result is a function of theThe final result is a function of theuncertainties of each step.uncertainties of each step.


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QA / QCQA / QC

The goal of quality assurance is to beThe goal of quality assurance is to be

able to identify, measure, and controlable to identify, measure, and control

the errors in each step.the errors in each step.

The goal of quality improvement is toThe goal of quality improvement is to

minimize or correct for individualminimize or correct for individual

errors and their cumulative effect.errors and their cumulative effect.


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SamplingSampling andand analyticalanalytical proceduresprocedures mustmusthavehave theirtheir ownown QAQA andand QCQC..

LaboratoryLaboratory orientedoriented QCQC measuresmeasures cancan accountaccountonlyonly forfor errorserrors thatthat occuroccur afterafter samplesample collectioncollection..

TheThe entireentire sequencesequence of of samplesample gathering,gathering,preservation,preservation, storage,storage, andand shipmentshipment mustmust bebeevaluatedevaluated toto measuremeasure andand minimizeminimize systematicsystematicsourcessources ofof error error andand ubiquitousubiquitous sourcessources ofofrandomrandom error error;; thesethese sourcessources cannotcannot bebe

measuredmeasured usingusing laboratorylaboratory orientedoriented QAQA andand QCQCprotocolsprotocols..


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Two Parameters Used to AssessTwo Parameters Used to Assess

Measurement Quality ObjectivesMeasurement Quality Objectives

BiasBias is defined as a systematic deviationis defined as a systematic deviation

(error) in data.(error) in data.

PrecisionPrecision is defined as random variation inis defined as random variation in

data.data.


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SamplingSampling qualityquality assuranceassurance programprogram shouldshouldprovideprovide thethe typetype andand numbernumber ofof qualityquality controlcontrolsamplessamples necessarynecessary toto controlcontrol andand minimizeminimize thetheeffectseffects ofof biasbias andand precisionprecision inin thethe samplingsamplingefforteffort..

TheThe designdesign ofof thethe studystudy shouldshould incorporateincorporateenoughenough samplessamples toto meetmeet thethe statisticalstatistical andandrepresentativenessrepresentativeness objectivesobjectives..

ExtraExtra samplessamples shouldshould bebe programmedprogrammed inin thethesamplingsampling designdesign toto allowallow forfor aa lossloss ofof samplesampledatadata duedue breakage,breakage, lablab mishaps,mishaps, andandanalytical,analytical, outout ofof controlcontrol situationssituations..


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Sampling ConsiderationsSampling Considerations

Sampling operations can contribute bothSampling operations can contribute bothsystematic and random error.systematic and random error.

These components are interactive, and they areThese components are interactive, and they are

evaluated using appropriate statistical methods.evaluated using appropriate statistical methods. Some aspects of sampling may cause largeSome aspects of sampling may cause large

variations and yet cannot be treated strictly byvariations and yet cannot be treated strictly by

statistics, i.e., by reducing or controllingstatistics, i.e., by reducing or controlling

systematic errors.systematic errors.


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ExamplesExamples::

ProperProper selectionselection ofof samplingsampling devicesdevices

ProperProper selectionselection ofof storagestorage containerscontainers

SorptionSorption oror reactionreaction biasbias fromfrom containercontainer materials,materials, samplingsampling equipment,equipment, orormaterialmaterial--transfertransfer lineslines cancan totallytotally invalidateinvalidate datadata generatedgenerated fromfrom samplessamples..

ProperProper selectionselection ofof preservationpreservation protocolsprotocols

DeteriorationDeterioration fromfrom biologicallybiologically mediatedmediated reactions,reactions, atmosphericatmospheric contact,contact,temperaturetemperature instability,instability, radiation,radiation, andand interactionsinteractions withwith otherother analytesanalytes cancan alsoalsocausecause seriousserious biasesbiases..

TheThe samplingsampling protocolprotocol mustmust specifyspecify preservationpreservation conditionsconditions thatthat willwill preventprevent oror

minimizeminimize theirtheir deteriorationdeterioration.. SelectionSelection ofof thethe analyticalanalytical methodmethod (sometimes)(sometimes)

FieldField manipulationsmanipulations areare necessary,necessary, butbut theythey shouldshould bebe plannedplanned andand recordedrecordedcarefullycarefully andand keptkept toto aa minimumminimum becausebecause theythey areare proneprone toto introducingintroducing biasbias..

MaterialMaterial transfers,transfers, filtrations,filtrations, physicalphysical measurements,measurements, aliquotaliquot preparation,preparation, andandspikingspiking areare allall potentialpotential sourcessources ofof biasbias fromfrom contaminationcontamination..

SelectionSelection ofof thethe samplingsampling sitessites (sometimes)(sometimes) FieldField QCQC samples,samples, ee..gg..,, blanks,blanks, spikes,spikes, andand replicates,replicates, shouldshould bebe handledhandled

exactlyexactly thethe samesame wayway asas thethe environmentalenvironmental samplessamples..

UsingUsing identicalidentical samplingsampling devices,devices, samplingsampling protocol,protocol, storagestorage containers,containers, shippingshippingprocedures,procedures, andand preservationpreservation techniquestechniques..

FieldField QCQC samplessamples cancan onlyonly provideprovide thethe basisbasis fromfrom whichwhich samplingsampling biasbias(usually(usually contamination)contamination) cancan bebe estimatedestimated oror samplingsampling precisionprecision cancan bebecalculatedcalculated..


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Defining Blank Sample RequirementsDefining Blank Sample Requirements

BlanksBlanks areare matricesmatrices thatthat havehave negligiblenegligible oror unmeasureableunmeasureableamountsamounts ofof thethe substancesubstance ofof interestinterest..

TheThe needneed forfor blanksblanks andand controlscontrols areare influencedinfluenced byby thethe DQOsDQOs..

WheneverWhenever aa possibilitypossibility existsexists forfor introducingintroducing extraneousextraneous materialmaterialintointo aa collection,collection, treatment,treatment, oror analyticalanalytical procedure,procedure, aa blankblank shouldshouldbebe deviseddevised toto detectdetect andand measuremeasure thethe extraneousextraneous materialmaterial..

BlanksBlanks commonlycommonly usedused forfor environmentalenvironmental samplingsampling includeinclude field,field, triptrip

matrix,matrix, equipment,equipment, andand materialmaterial blanksblanks.. TheseThese blanksblanks areare usuallyusually supplementedsupplemented atat thethe laboratorylaboratory withwith thethe

preparationpreparation solvent,solvent, reagent,reagent, instrument,instrument, andand methodmethod blanksblanks totomeasuremeasure analyticalanalytical biasbias..


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Field blanksField blanksaresamples ofanalytearesamples ofanalyte--freemediafreemedia

similar to thesamplematrix.similar to thesamplematrix.

TheyThey areare transferredtransferred fromfrom oneone vesselvessel toto anotheranother ororexposedexposed toto thethe samplingsampling environmentenvironment atat thethe samplingsamplingsitesite..

FieldField blankblank waterwater samplessamples consistconsist ofof tripletriple distilleddistilled waterwaterthatthat isis carriedcarried toto thethe samplingsampling sitesite andand exposedexposed toto thetheairair therethere soso thatthat anyany contaminationcontamination fromfrom thethe airair cancan bebemeasuredmeasured andand accountedaccounted forfor..

TheyThey measuremeasure incidentalincidental oror accidentalaccidental samplesample

contaminationcontamination duringduring thethe wholewhole processprocess (sampling,(sampling,transport,transport, samplesample preparation,preparation, andand analysis)analysis)..

EachEach samplingsampling teamteam shouldshould collectcollect oneone fieldfield blankblank aa daydayperper collectioncollection apparatusapparatus;; thethe fieldfield blankblank matrixmatrix shouldshould bebecomparablecomparable toto thethe samplesample ofof interestinterest..


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TripTrip blanksblanks (or(or transporttransport blanksblanks)) areare testtest

samplessamples of of analyteanalyte--freefree mediamedia takentaken fromfrom thethe

laboratorylaboratory toto thethe samplingsampling sitesite andand returnedreturned totothethe laboratorylaboratory unopenedunopened..

TheyThey areare usedused toto measuremeasure crosscross--contaminationcontamination fromfrom

thethe containercontainer andand preservativepreservative duringduring transport,transport, fieldfieldhandling,handling, andand storagestorage..

AtAt leastleast oneone triptrip blankblank shouldshould bebe collectedcollected perper dayday perper

typetype ofof samplesample..

EPAEPA hashas shownshown thatthat crosscross--contaminationcontamination onlyonly occursoccurs

withwith volatilevolatile organicsorganics (VOAs)(VOAs)..


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BackgroundBackground SamplesSamples (or(or matrixmatrix blanksblanks oror controlcontrol

samplessamples)) areare samplessamples ofof thethe mediamedia similarsimilar toto thethetesttest samplesample matrixmatrix andand areare takentaken nearneartoto thethe timetime andand

placeplace wherewhere thethe analytesanalytes ofof interestinterest maymay existexist atat

backgroundbackground levelslevels..

TheyThey measuremeasure thethe backgroundbackground presencepresence ofof analytesanalytes ofofinterestinterest inin thethe samesame matrixmatrix fromfrom whichwhich thethe samplessamples areareobtainedobtained (for(for example,example, water,water, sludge,sludge, activatedactivated carbon,carbon,sandysandy loamloam soil,soil, tissues,tissues, etcetc..))

TheThe frequencyfrequency ofof theirtheir analysisanalysis shouldshould bebe equivalentequivalent toto

thatthat ofof thethe reagentreagent blanksblanks..

TheThe moremore complexcomplex aa matrixmatrix is,is, thethe moremore importantimportant matrixmatrixblanksblanks becomebecome..


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Equipment blanksEquipment blanks (or(or rinsateblanksrinsateblanks))are samplesare samplesofanalyteofanalyte--freemediathat havebeenused to rinsefreemediathat havebeenused to rinse

thesampling equipment.thesampling equipment.

They document adequate decontamination of the samplingThey document adequate decontamination of the samplingequipment after its use.equipment after its use.

These blanks are collected after equipmentThese blanks are collected after equipment

decontamination and prior to resampling.decontamination and prior to resampling.


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MaterialMaterial blanksblanks areare samplessamples ofof constructionconstruction

materialsmaterials suchsuch asas thosethose usedused inin groundwatergroundwater

wells,wells, pumppump andand flowflow testing,testing, etcetc..

They document the decontamination (or measureThey document the decontamination (or measure

artefacts) from use of these materials.artefacts) from use of these materials.


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WhentousetheBlanks?WhentousetheBlanks?

IfIf thethe fieldfield blanksblanks indicateindicate nono problems,problems, thethe otherother blanksblanksmaymay bebe discardeddiscarded oror storedstored asas necessarynecessary..

IfIf aa problemproblem isis discovered,discovered, thethe individualindividual blanksblanks cancan bebeanalyzedanalyzed toto determinedetermine itsits sourcesource..

NoteNote thethe prescribedprescribed holdingholding timestimes ofof thethe otherother blanksblanks.. BeBesuresure thatthat theythey areare stillstill validvalid (not(not exceedingexceeding thetheprescribedprescribed holdingholding times)times)..

WhenWhen anan extractionextraction devicedevice (such(such asas anan airair filter,filter,charcoal,charcoal, anan ionion exchanger,exchanger, oror Tenax)Tenax) isis usedused insteadinstead ofof

directdirect samplesample collection,collection, thethe field,field, storage,storage, andand transporttransportblanksblanks mustmust includeinclude thethe correspondingcorresponding extractionextraction devicedevice..

ControlControl chartscharts (plots(plots ofof thethe datadata fromfrom blanksblanks vsvs time)time)provideprovide thethe mostmost effectiveeffective mechanismmechanism forfor interpretinginterpretingblankblank analysisanalysis resultsresults..


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Background (Control) Sample SelectionBackground (Control) Sample Selection

2 Types of Controls2 Types of Controls

1. those used to determine whether or not an1. those used to determine whether or not ananalytical procedure is in statistical controlanalytical procedure is in statistical control

2. those used to determine whether or not an analyte

2. those used to determine whether or not an analyteof interest is present in a studied population but not inof interest is present in a studied population but not in

a similar control populationa similar control population

Sampling control standardsSampling control standards are used to determine whether anare used to determine whether ananalyte of interest is really present in the test samples under study.analyte of interest is really present in the test samples under study.

Background (control site) sampleBackground (control site) sample

Local control sitesLocal control sites

Area control sitesArea control sites

Field spike sampleField spike sample


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Background SamplesBackground Samples

(or control site or matrix samples)(or control site or matrix samples)

SamplesSamples takentaken nearnear thethe timetime andand placeplace ofof thethe samplesample ofofinterestinterest

DemonstrateDemonstrate whetherwhether thethe sitesite isis contaminatedcontaminated oror trulytrulydifferentdifferent fromfrom thethe normnorm..

NecessaryNecessary forfor aa validvalid scientificscientific comparisoncomparison ofof samplessamplessuspectedsuspected ofof containingcontaining environmentalenvironmental contaminantscontaminants

withwith samplessamples containingcontaining nono (below(below detectabledetectable orormeasurablemeasurable levels)levels) oror acceptablyacceptably lowlow levelslevels ofofcontaminantscontaminants..


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BackgroundBackground samplessamples shouldshould bebe collectedcollected andand analyzedanalyzed underunder thethe

samesame conditionsconditions asas thethe samplesample ofof interestinterest.. ThisThis isis toto knowknow oror estimateestimate withwith anyany acceptableacceptable degreedegree ofof uncertaintyuncertainty

thethe presencepresence and/orand/or concentrationconcentration levelslevels ofof thethe analytesanalytes ofof interestinterestandand thethe effectseffects ofof thethe matrixmatrix onon theirtheir analysisanalysis..

BackgroundBackground samplessamples ofof eacheach significantlysignificantly differentdifferent matrixmatrix mustmustalwaysalways bebe collectedcollected whenwhen typestypes ofof matricesmatrices areare involvedinvolved..

ExEx.. VariousVarious typestypes ofof water,water, sediments,sediments, andand soilssoils inin oror nearnear aa samplingsamplingsitesite areaarea..

BackgroundBackground airair samplessamples wouldwould includeinclude upwindupwind airair samplessamples andandperhapsperhaps differentdifferent heightheight samplessamples..

LogicalLogical exceptionexception toto collectingcollecting backgroundbackground samplessamples isis whenwhen drumsdrums ororcontainerscontainers ofof materialsmaterials areare involved,involved, asas inin landfilllandfill;; however,however, ifif thethechemicalschemicals areare suspectedsuspected ofof pollutingpolluting thethe landland ,, water,water, oror airair aroundaroundthem,them, appropriateappropriate backgroundbackground samplessamples ofof thosethose matricesmatrices mustmust bebetakentaken forfor analysisanalysis..


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Local control sitesLocal control sites

UsuallyUsually adjacentadjacent oror veryvery nearnear thethe testtest samplesample sitessites

InIn selectingselecting andand workingworking withwith locallocal controlcontrol sitessites thethefollowingfollowing principlesprinciples applyapply::

LocalLocal controlcontrol sitessites generallygenerally shouldshould bebe upwindupwind ororupstreamupstream ofof thethe samplingsampling sitesite..

WhenWhen possible,possible, locallocal controlcontrol sitesite samplessamples shouldshould bebetakentaken first,first, toto avoidavoid contaminationcontamination fromfrom thethe samplesample sitesite..

TravelTravel betweenbetween locallocal controlcontrol sitessites andand samplingsampling areasareasshouldshould bebe minimizedminimized becausebecause ofof potentialpotential contaminationcontaminationcausedcaused byby people,people, equipment,equipment, and/orand/or vehiclesvehicles..


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Area control siteArea control site

TheThe samesame area,area, ee..gg..,, aa citycity oror country,country, asas thethesamplingsampling sitesite butbut notnot adjacentadjacent toto itit..

FactorsFactors toto bebe consideredconsidered inin selectionselection areare similarsimilar totothosethose forfor locallocal controlcontrol sitessites..

LocalLocal sitessites areare preferablepreferable toto areaarea controlcontrol sitessitesbecausebecause theythey areare physicallyphysically closercloser toto thethe samplingsamplingsitesite..

WhenWhen aa suitablesuitable locallocal controlcontrol sitesite cannotcannot bebe found,found, thenthen ananareaarea controlcontrol sitesite willwill allowallow importantimportant backgroundbackground samplessamples totobebe collectedcollected..


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Field Spike SamplesField Spike Samples

areare selectedselected fieldfield samplessamples toto whichwhich knownknown amountsamounts ofofthethe analytesanalytes ofof interestinterest areare addedadded duringduring theirtheir collectioncollectioninin thethe fieldfield..

UsedUsed toto identifyidentify field,field, transportation,transportation, andand matrixmatrix effectseffects..

ForFor complexcomplex matricesmatrices liableliable toto causecause interferencesinterferences inin thetheanalysis,analysis, aa fieldfield spikespike samplesample maymay bebe usedused toto measuremeasurethethe magnitudemagnitude ofof thosethose interferencesinterferences..

FieldField spikespike samplessamples mustmust bebe preparedprepared byby experiencedexperiencedpersonnelpersonnel soso thatthat interpretationinterpretation ofof analyticalanalytical resultsresults areare

notnot complicatedcomplicated byby errorserrors.. InIn thethe eventevent thatthat backgroundbackground samplessamples cancan provideprovide aa

reasonablereasonable substitutesubstitute thatthat willwill helphelp toto estimateestimate matrixmatrixeffectseffects;; however,however, fieldfield spikedspiked samplessamples mymy havehave higherhigherextractionextraction efficienciesefficiencies thanthan unspikedunspiked testtest samplessamples..

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Quality Assurance Quality Control_Lecture3