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Introduction. Yongsik Lee. Classification of Analytical Methods. Classical methods Instrumental methods. Instrumental Methods. Photon Charge Heat Radioactive. Instruments. Data domain Non-electrical domain Electrical domain Analog Time digital. Detectors. Detectors

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introduction

Introduction

Yongsik Lee

classification of analytical methods
Classification of Analytical Methods
  • Classical methods
  • Instrumental methods
instrumental methods
Instrumental Methods
  • Photon
  • Charge
  • Heat
  • Radioactive
instruments
Instruments
  • Data domain
    • Non-electrical domain
    • Electrical domain
      • Analog
      • Time
      • digital
detectors
Detectors
  • Detectors
    • 물리량의 변화를 기록 또는 표시
    • 기계적, 전기적, 화학적 장치
  • Transducers
    • 비전기적 영역 정보와 전기적 영역 정보 사이 변환
    • 변환 함수 = 둘 사이의 수학적 관계식
  • Sensors
    • 특정 화학종을 연속적으로, 가역적으로 검출하는 분석장치
other components of instrument
Other Components of Instrument
  • Readout device
  • Microprocessor
  • Computer
selecting a method
Selecting a method
  • Defining the problem
    • 요구되는 정확도
    • 이용할 수 있는 시료의 양
    • 분석물의 농도 범위
    • 방해 성분
    • 시료 매트릭스의 물리적, 화학적 성질
    • 시료의 개수
    • 신속성
    • 실험자의 숙련도
    • 기기 장치의 가격과 이용 가능성
    • 시료당 비용
characteristics of instrument
Characteristics of Instrument
  • Precision
  • Bias
  • Sensitivity
  • Detection limit
  • Concentration range
  • selectivity
precision
Precision
  • 정밀도
    • Measure of random, or indeterminate error
    • 재현성 reproducibility
    • 표준편차, 변동계수 등
    • 표 1-5 성능 계수 (figure of merit)
slide10
Bias
  • 고정 오차
    • Measure of systematic or determinate error
  • Definition
    • Bias = (population mean) – (true value)
sensitivity
Sensitivity
  • Definition
    • Measure of its ability to discriminate between small differences in analyte concentration
    • Tow factors
      • Slope of calibration curve - steeper slope
      • Precision – better precision
classification of analytical methods1
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
slide14
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 quantitative analysis
types of instrumental methods
Types of Instrumental Methods:
  • Radiation emission
    • Emission spectroscopy - fluorescence, phosphorescence, luminescence
  • 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
slide16
Radiation rotation
    • Polarimetry, circular dichroism
  • Electrical potential
    • Potentiometry
  • Electrical charge
    • Coulometry
  • Electrical current
    • Voltammetry - amperometry, polarography
  • Electrical resistance
    • Conductometry
slide17
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
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
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
Non-Electrical Domains
  • Physical (light intensity, color)
  • Chemical (pH)
  • Scale Position (length)
  • Number (objects)
electrical domains
Electrical Domains
  • Current
  • Voltage
  • Charge
  • Frequency
  • Pulse width
  • Phase
  • Count
  • Serial
  • Parallel
time domains
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
Digital Binary Data
  • Advantages
    • easy to store
    • not susceptible to noise
figures of merit
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
precision1
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
Accuracy
    • Determinate errors (operator, method, instrumental)
    • Bias:
      • bias = <x> - x(true)
  • Sensitivity
    • Calibration sensitivity: S
    • larger slope of calibration curve means more sensitive measurement
analytical sensitivity
Analytical Sensitivity
  • Mandel and Stiehler
  • 분석감도 = 검정곡선기울기/측정표준편차
  • 기기의 증폭률을 증가시키면 검정곡선 기울기는 증가하지만, 일반적으로 측정 표준편차도 같이 증가하므로 분석감도는 일정하다.
detection limit
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
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
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
Calibration methods
  • 검정
  • Basis of quantitative analysis is magnitude of 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 method
Standard Addition Method
  • spiking
    • 같은 크기의 시료 분취량에
    • 표준물 용액 일정량을 증가시키며 더하고 측정
  • 매트릭스는 표준물 첨가후에도 거의 변화없다고 가정
  • 최소제곱분석법
internal standard method
Internal Standard Method
  • 내부 표준
    • 모든 시료, 바탕, 그리고 분석 표준물에 일정량씩 더하는 물질
  • 검정곡선 획득
    • 신호비=표준 분석물의 신호/내부 표준물의 신호
    • 신호비를 표준물의 농도에 대해 그려 얻는다.
  • 우연오차와 계통오차를 보정할 수 있다
  • 적당한 내부표준물 확보가 어렵다
species of interest
Species of interest
  • All constituents
  • including analyte.
  • Matrix-analyte
  • =concomitants
  • Often need pretreatment - chemical extraction, distillation, separation, precipitation