1. Introduction
Yongsik Lee

2. Classification of Analytical Methods
Classical methods
Instrumental methods

3. Instrumental Methods
Photon
Charge
Heat
Radioactive

4. Instruments Data domain Non-electrical domain Electrical domain Analog
Time
digital

5. Detectors Detectors Transducers Sensors 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

6. Other Components of Instrument
Readout device
Microprocessor
Computer

7. 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

8. Characteristics of Instrument
Precision
Bias
Sensitivity
Detection limit
Concentration range
selectivity

9. Precision 정밀도 Measure of random, or indeterminate error
재현성 reproducibility
표준편차, 변동계수 등
표 1-5 성능 계수 (figure of merit)

10. Bias 고정 오차 Definition Measure of systematic or determinate error
Bias = (population mean) – (true value)

11. 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

13. 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

14. 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

15. 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

16. Radiation rotation
Polarimetry, circular dichroism
Electrical potential
Potentiometry
Electrical charge
Coulometry
Electrical current
Voltammetry - amperometry, polarography
Electrical resistance
Conductometry

17. 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)

18. Example: Spectrophotometry
Instrument: spectrophotometer
Stimulus: monochromatic light energy
Analytical response: light absorption
Transducer: photocell
Data: electrical current
Data processor: current meter
Readout: meter scale

19. 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

20. Non-Electrical Domains
Physical (light intensity, color)
Chemical (pH)
Scale Position (length)
Number (objects)

21. Electrical Domains Current Voltage Charge Frequency Pulse width Phase
Count
Serial
Parallel

22. Time Domains 정보는 신호의 크기로서 보다는 시간에 따른 신호의 요동으로 시간 영역에 저장된다. Time Analog
vary with time
frequency, phase, pulse width
Analog
continuously variable magnitude
current, voltage, charge
Digital
discrete values
count, serial, parallel, number

23. Digital Binary Data
Advantages
easy to store
not susceptible to noise

24. 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

25. 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

26. Accuracy
Determinate errors (operator, method, instrumental)
Bias:
bias = <x> - x(true)
Sensitivity
Calibration sensitivity: S
larger slope of calibration curve means more sensitive measurement

27. Analytical Sensitivity
Mandel and Stiehler
분석감도 = 검정곡선기울기/측정표준편차
기기의 증폭률을 증가시키면 검정곡선 기울기는 증가하지만, 일반적으로 측정 표준편차도 같이 증가하므로 분석감도는 일정하다.

28. 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

29. 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

30. 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).

31. 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

32. Standard Addition Method
spiking
같은 크기의 시료 분취량에
표준물 용액 일정량을 증가시키며 더하고 측정
매트릭스는 표준물 첨가후에도 거의 변화없다고 가정
최소제곱분석법

33. 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

34. Calibration curves (working or analytical curves)

35. Example

36. Calculate Precision

37. Calibration Expression

39. Species of interest All constituents including analyte. Matrix-analyte
=concomitants
Often need pretreatment - chemical extraction, distillation, separation, precipitation