IntroductionIntroduction

Yongsik LeeYongsik Lee

Classification of Analytical Classification of Analytical MethodsMethods

►Classical methodsClassical methods► Instrumental methodsInstrumental methods

Instrumental MethodsInstrumental Methods

►PhotonPhoton►ChargeCharge►HeatHeat►Radioactive Radioactive

InstrumentsInstruments

►Data domainData domain Non-electrical domainNon-electrical domain Electrical domainElectrical domain

►AnalogAnalog►TimeTime►digitaldigital

DetectorsDetectors

► DetectorsDetectors 물리량의 변화를 기록 또는 표시물리량의 변화를 기록 또는 표시 기계적기계적 , , 전기적전기적 , , 화학적 장치화학적 장치

► TransducersTransducers 비전기적 영역 정보와 전기적 영역 정보 사이 변환비전기적 영역 정보와 전기적 영역 정보 사이 변환 변환 함수 변환 함수 = = 둘 사이의 수학적 관계식둘 사이의 수학적 관계식

► SensorsSensors 특정 화학종을 연속적으로특정 화학종을 연속적으로 , , 가역적으로 검출하는 가역적으로 검출하는

분석장치분석장치

Other Components of Other Components of InstrumentInstrument

►Readout deviceReadout device►MicroprocessorMicroprocessor►ComputerComputer

Selecting a methodSelecting a method

► Defining the problemDefining the problem 요구되는 정확도요구되는 정확도 이용할 수 있는 시료의 양이용할 수 있는 시료의 양 분석물의 농도 범위분석물의 농도 범위 방해 성분방해 성분 시료 매트릭스의 물리적시료 매트릭스의 물리적 , , 화학적 성질화학적 성질 시료의 개수시료의 개수 신속성신속성 실험자의 숙련도실험자의 숙련도 기기 장치의 가격과 이용 가능성기기 장치의 가격과 이용 가능성 시료당 비용시료당 비용

Characteristics of InstrumentCharacteristics of Instrument

►PrecisionPrecision►BiasBias►SensitivitySensitivity►Detection limitDetection limit►Concentration rangeConcentration range►selectivityselectivity

PrecisionPrecision

►정밀도정밀도 Measure of random, or indeterminate errorMeasure of random, or indeterminate error 재현성 재현성 reproducibilityreproducibility 표준편차표준편차 , , 변동계수 등변동계수 등 표 표 1-5 1-5 성능 계수 성능 계수 (figure of merit)(figure of merit)

BiasBias

►고정 오차고정 오차 Measure of systematic or determinate Measure of systematic or determinate

errorerror

►DefinitionDefinition Bias = (population mean) – (true value)Bias = (population mean) – (true value)

SensitivitySensitivity

►DefinitionDefinition Measure of its ability to discriminate between sMeasure of its ability to discriminate between s

mall differences in analyte concentrationmall differences in analyte concentration Tow factorsTow factors

►Slope of calibration curve - steeper slopeSlope of calibration curve - steeper slope►Precision – better precisionPrecision – better precision

Classification of Analytical Methods

►Qualitative instrumental analysis measured property indicates presence of analyte

in matrix►Quantitative instrumental analysis

magnitude of measured property is proportional to concentration of analyte in matrix

► Classical Qualitative - identification by color, indicators, boiling points, odors Quantitative - mass or volume e.g. gravimetric, volumetric

► Instrumental Qualitative - chromatography, electrophoresis and identification by

measuring physical property e.g. spectroscopy, electrode potential

► Quantitative measuring property and determining relationship to concentration e.g. spectrophotometry, mass spectrometry Often, same instrumental method used for qualitative and quantitati

ve analysis

Types of Instrumental Methods:

► Radiation emission Emission spectroscopy - fluorescence, phosphorescence, l

uminescence► Radiation absorption

Absorption spectroscopy - spectrophotometry, photometry, nuclear magnetic resonance, electron spin resonance

► Radiation scattering Turbidity, Raman

► Radiation refraction Refractometry, interferometry

► Radiation diffraction X-ray, electron

►Radiation rotation Polarimetry, circular dichroism

► Electrical potential Potentiometry

► Electrical charge Coulometry

► Electrical current Voltammetry - amperometry, polarography

► Electrical resistance Conductometry

► Mass Gravimetry

► Mass-to-charge ratio Mass spectrometry

► Rate of reaction Stopped flow, flow injection analysis

► Thermal Thermal gravimetry, calorimetry

► Radioactivity Activation, isotope dilution (Often combined with chromatographic or electrophoretic

methods)

Example: Spectrophotometry

► Instrument: spectrophotometer► Stimulus: monochromatic light energy► Analytical response: light absorption► Transducer: photocell► Data: electrical current► Data processor: current meter► Readout: meter scale

Data Domains

► way of encoding analytical response in electrical or non-electrical signals

► 정보를 코드화하는 여러 방법들을 영역 ( 도메인 ) 이라고 한다

► Interdomain conversions transform information from one domain to another.

► Light Intensity => Photocell Current => Current Meter Scale

► Detector (general): device that indicates change in environment

► Transducer (specific): device that converts non-electrical to electrical data

► Sensor (specific): device that converts chemical to electrical data

Non-Electrical Domains

►Physical (light intensity, color)►Chemical (pH) ►Scale Position (length)►Number (objects)

Electrical Domains

►Current►Voltage►Charge► Frequency►Pulse width►Phase►Count►Serial►Parallel

Time Domains

►정보는 신호의 크기로서 보다는 시간에 따른 신호의 요동으로 시간 영역에 저장된다 .

►Time vary with time frequency, phase, pulse width

►Analog continuously variable magnitude current, voltage, charge

►Digital discrete values count, serial, parallel, number

Digital Binary Data

►Advantages easy to store not susceptible to

noise

Figures of Merit

►Performance Characteristics:►How to choose an analytical method? ►How good is measurement?►How reproducible? - Precision►How close to true value? - Accuracy/Bias►How small a difference can be measured? -

Sensitivity►What range of amounts? - Dynamic Range►How much interference? - Selectivity

Precision

Indeterminate or random errors Absolute standard deviation

►절대표준편차 Variance 분산 : s2

Relative standard deviation: ►상대 표준편차►RSD = s/<x>

Standard deviation of mean:►평균의 표준편차► sm

Accuracy

Determinate errors (operator, method, instrumental)

Bias: ►bias = <x> - x(true)

►Sensitivity Calibration sensitivity: S larger slope of calibration c

urve means more sensitive measurement

Analytical SensitivityAnalytical Sensitivity

►Mandel and StiehlerMandel and Stiehler►분석감도 분석감도 = = 검정곡선기울기검정곡선기울기 // 측정표준편차측정표준편차

►기기의 증폭률을 증가시키면 검정곡선 기기의 증폭률을 증가시키면 검정곡선 기울기는 증가하지만기울기는 증가하지만 , , 일반적으로 측정 일반적으로 측정 표준편차도 같이 증가하므로 분석감도는 표준편차도 같이 증가하므로 분석감도는 일정하다일정하다 ..

Detection Limit

►Signal must be bigger than random noise of blank

►Minimum signal: Signal min = Average Signal of blank + ks(blank) From statistics k=3 or more

►(at 95% confidence level)►Suggested by Long and Winefordner

Dynamic Range

► At detection limit we can say confidently analyte is present but cannot perform reliable quantitation

► Level(Limit) of quantitation (LOQ): (k=10)s(blank) 정량적 측정을 할 수 있는 가장 낮은 농도 , 정량 한계

► Limit of linearity (LOL) when signal is no longer proportional to concentration,

선형 한계► Dynamic range 유용한 측정농도 범위

Selectivity:

►No analytical method is completely free from interference by concomitants. Best method is more sensitive to analyte than interfering species (interferent).

►Matrix with species A&B Signal = mAcA +mBcB + Signal blank

►Selectivity coefficient kB,A = mB/mA

► k's vary between 0 (no selectivity) and large number (very selective).

Calibration methods

►검정►Basis of quantitative analysis is magnitude o

f measured property is proportional to concentration of analyte

►Signal ∝ µ[x] Signal = m[x]+ Signal of blank

►[x] = {Signal -Signal of blank}/m

Standard Addition MethodStandard Addition Method

►spikingspiking 같은 크기의 시료 분취량에 같은 크기의 시료 분취량에 표준물 용액 일정량을 증가시키며 더하고 측정표준물 용액 일정량을 증가시키며 더하고 측정

►매트릭스는 표준물 첨가후에도 거의 매트릭스는 표준물 첨가후에도 거의 변화없다고 가정변화없다고 가정

►최소제곱분석법최소제곱분석법

Internal Standard MethodInternal Standard Method

►내부 표준내부 표준 모든 시료모든 시료 , , 바탕바탕 , , 그리고 분석 표준물에 그리고 분석 표준물에

일정량씩 더하는 물질일정량씩 더하는 물질►검정곡선 획득검정곡선 획득

신호비신호비 == 표준 분석물의 신호표준 분석물의 신호 // 내부 표준물의 내부 표준물의 신호신호

신호비를 표준물의 농도에 대해 그려 얻는다신호비를 표준물의 농도에 대해 그려 얻는다 ..►우연오차와 계통오차를 보정할 수 있다우연오차와 계통오차를 보정할 수 있다►적당한 내부표준물 확보가 어렵다적당한 내부표준물 확보가 어렵다

Calibration curves (working or analytical curves)

ExampleExample

Calculate PrecisionCalculate Precision

Calibration ExpressionCalibration Expression

Species of interest

►All constituents►including analyte.►Matrix-analyte►=concomitants►Often need pretreatment - chemical extractio

n, distillation, separation, precipitation