원자흡수분광분석법 (원리및 응용)

차 례 Optical Spectra의 역사 원자분광분석법의 기본원리 원자흡수분광기의 구조 원자흡수분광기의 기기적 특성 차 례 Optical Spectra의 역사 원자분광분석법의 기본원리 원자흡수분광기의 구조 원자흡수분광기의 기기적 특성 AAS의 측정 AAS의 오차 Flame vs Furnace AAS의 비교 다른 원자분광분석기와의 비교 AAS의 응용

Early History of Optical Spectra Sir Isaac Newton discovers the solar spectrum in the late 1600’s Sunlight Prism

Fraunhofer Lines 1802 Wollaston discovered dark lines in solar spectrum Fraunhofer investigated lines in detail Lines due to sundown atmosphere absorbing light

Kirchhoff & Bunsen’s Experiment (1) Light Source Burner Prism White Card Place Salt on Wire Loop and Hold in Flame Lens Dark Lines

Kirchhoff & Bunsen’s Experiment (2) Used to Discover the Elements Rb and Cs Place Salt on Wire Loop and Hold in Flame Lens White Card Burner Emission Lines Prism

Absorption vs Emission Fraunhofer Absorption Lines Cu Ba Na K Elemental Emission Lines 190 nm 900 nm Qualitative analysis of elements

Alan Walsh

Ground State Atom Orbitals Neutrons Protons Electrons

Absorption of Energy by Atom Valence (Outer) Electrons Excited State Atom h Energy Absorbed Ground State Atom

Energy Level Diagram Electron Energy Transitions E4 E3 E2 E1 Eo 5 6 Resonance lines originate from ground state (Eo)

Atomic Absorption Process Sunlight Sun Atmosphere Energy Transitions E3 E2 E1 Eo 3 2 1 4 1 2 3 4 Resonance lines must originate from ground state

Energy Level Diagram for Pb Electron Energy Transitions E4 E3 E2 E1 Eo 202.2 217.0 261.4 283.3 Wavelength in Nanometers

Absorption Energy Diagram (Few Lines/Element) Excitation E Ionization E3 } Excited States E2 c Energy E1 b a b c d a Eo Ground State

Emission Energy Diagram (Many Lines/Element) Ionization E3 } Excited States E2 c Energy E1 b a b c d a Eo Ground State

Atomic Absorption Spectrometry AAS intrinsically more sensitive than AES Similar atomization techniques to AES Addition of radiation source High temperature for atomization necessary : Flame and Electrothermal atomization Very high temperature for excitation not necessary Generally no plasma/arc/spark AAS

Atomic Absorption Io It Resonance Non-resonance Fill Gas Resonance

Flame AAS Simplest atomization of gas/solution/solid Laminar flow burner – stable “sheet” of flame Flame atomization best for reproducibility Precision (<1%) Relatively insensitive – incomplete volatilization, Short time in beam

Laminar Flow Burner Cheap Simple Flame stability Low temperature

Flame Temperatures

Temperature Profiles of Natural gas/Air Flame Primary combustion zone: Initial decomposition, molecular fragments, cool Interzonal region: Hottest, most atomic fragments, Used for emission/fluorescence Secondary combustion zone: Cooler, conversion of atoms to Stable molecules, oxides

Flame Absorbance Profile for Three Elements Most sensitive part of flame for AAS varies with analyte Consequences? Sensitivity varies with element Must maximize burner position Makes multielement detection difficult

Electrothermal Atomizer Entire sample atomized in short time (2000 – 3000 oC) Sample spends up to 1 s in analysis volume Superior sensitivity (10-10 – 10-13 g analyte) Less reproducible (5 – 10 %RSD)

Types of Graphite Furnace Graphite tube with L’vov platform Solid Sampling Accessory

Graphite Furnace Cross Section External Ar gas prevents tube destruction Internal Ar gas circulates gaseous analyte

Four Step Sample Preparation Dry – evaporation of solvents (10 - >100 s) Ash – removal of volatile hydroxides, sulfates, carbonates etc. (10 - 100 s) (3) Fire/Atomizer – atomization of remaining analyte (1 s) (4) Clean Out

Furnace Thermal Stages Dry Ash Atomize T E M P T I M E Clean Out Cool Down

Periodic Table H He Li Be B C N O F Ne Furnace Only Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Furnace Only Flame & Furnace Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Atomic Absorption Instrumentation AAS should be very selective – each element has different set of energy levels and lines very narrow BUT for linear calibration curve (Beer’s Law) need bandwidth of absorbing species to be broader than that of light source : difficult with ordinary monochromator Solved by using very narrow line radiation sources Minimize Doppler broadening Pressure broadening Lower P and T than atomizer

Hollow Cathode Lamp 300 V applied between anode (+) and metal cathode (-) Ar ions bombard cathode and sputter cathode atoms Fraction of sputtered atoms excited, then fluoresce Cathode made of metal of interest (Na, Ca, K, Fe,…..) Different lamp for each element Restricts multielement detection Hollow cathode to Maximize probability of redeposition on cathode Restricts light direction

Multi-element HCL lamps

Pneumatic Nebulizers Concentric tube Cross-flow Fritted disk Babington

Single-beam Design AA Spectrometer Signal at one wavelength often contains luminescence from interferent in flame Chemical interference: reverses atomization equilibria reacts with analyte to form low volatile compound Releasing agent – cations that react preferentially with interferent Protecting agent – form stable but volatile compounds with analyte ionization

Double-beam Design AA Spectrometer Spectral interference - emission or absorption from interferent overlaps analyte Beam usually chopped or modulated at known frequency Signal then contains constant (background) and dynamic (time-varying) signals

Echelle Monochromator Echelle grating with a prism, Focal plane

Multielement Instruments Hitachi design Multiple HCLs with multiple detection systems

Thermo Jarrell Ash Design Perkin-Elmer Design Multiple HCLs with one monochromator and PMT with a mirror and grating controlled by a galvanometer Multiple HCLs with an echelle monochromator and a CCD detector

Leeman Lab. Design SIMAAC Design Multiple HCLs arranged on the focal plane of the grating Continuum source excitation with a monochromator and PMT

Photomultiplier Tube (PMT)

Solid State Detector

Beer-Lambert Absorbance Calculation It A = log ( ) = abc A c Where: A = Absorbance a = absorptivity Io = Incident Light Intensity b = path length It = Transmitted Light Intensity c = concentration

Beer-Lambert Law Theoretical A = abc A B S Actual abc A CONC

% Transmittance vs ABS Transmittance Absorbance 10 % 1 1 % 2 0.1 % 3 100 % 0 10 % 1 1 % 2 0.1 % 3

Flame vs Furnace Sensitivity 100 g/L Pb @ 217.0 nm 0.936 Furnace Signal for 10 L Absorbance Flame Signal 0.004

Flame vs Furnace AAS Criteria Flame Furnace Elements 67 48 Sensitivity ppm-% ppt-ppb Precision good fair Interferences few many Speed rapid slow Simplicity easy more complex Flame Hazards yes no Automation yes yes (unattended) Operating Cost low medium

Flame vs Furnace Detection Limit Comparison Element Flame (PPB) Furnace (PPB)* Ag 3 0.035 As 450 0.25 Bi 50 0.45 Cd 3 0.01 Cr 9 0.075 Pb 15 0.2 Zn 1.5 0.0075 *Results Based on 20 L Volume & D2 Peak Height ABS

Hydride Generation Techniques A method for introducing samples containing arsenic, antimony, tin, selenium, bismuth, and lead into an atomizer as a gas Enhances D.L. by a factor of 10 to 100. 3BH4- + 3H+ + 4H3AsO3 3H3BO3 + 4AsH3 + 3H2O

Continuum-source Correction Alternate pass through: Continuum source of D2 and HCL radiation And then subtract AHCL – AD2 = Ac

Zeeman Background Correction The  peak absorbs only the radiation that is plane polarized in a direction parallel to the external magnetic field The  peaks absorb only radiation polarized at 90 deg to the field A// – A = Ac

Smith-Hieftje Background Correction Based on self-reversal or self-absorption A low current – A high current = Ac

AA vs. ICP-AES vs. ICP-MS: 비 교 표

기기에대한 결정 인자 분석시 샘플형태 분석물질의 농도 샘플 전처리정도 예 산 운용 유지비 분석상황

분 석 시 샘 플 형 태 액 상 고 상 (슬러지) 고상형태 (직접주입) Flame AA Vapor Generation AA 분 석 시 샘 플 형 태 액 상 Flame AA Vapor Generation AA Graphite Furnace AA ICP-AES ICP-MS 고 상 (슬러지) 고상형태 (직접주입) 고가의 악세사리(스파크 또는 레이저 시스템)

용 융 고 체 분 석 시 용융 고상함유% Vapor Generation GFAA Flame AA ICP-AES ICP-MS 용 융 고 체 분 석 시 용융 고상함유% Vapor Generation GFAA Flame AA ICP-AES ICP-MS 0 5 10 15 20 25 % Solids

샘 플 효 율

원 자 화 / 이 온 화 효 율

최 소 샘 플 주 입 량

# 분 석 가 용 원 소 Vapor Generation GFAA Flame AA ICP-AES ICP-MS # 분 석 가 용 원 소 Vapor Generation GFAA Flame AA ICP-AES ICP-MS 0 10 20 30 40 50 60 70 80 90 100 # Elements

분 석 감 도 Vapor Generation AA GFAA Flame AA ICP-AES ICP-MS 분 석 감 도 Vapor Generation AA GFAA Flame AA ICP-AES ICP-MS 1 10 100 1 10 100 1 10 100 1000 ppt ppb ppm ng/L mg/L mg/L

직 선 동 적 범 위 Vapor Generation GFAA Flame AA (SIPS) ICP-AES 직 선 동 적 범 위 Vapor Generation GFAA Flame AA (SIPS) ICP-AES ICP-MS (Extended Range) 100 101 102 103 104 105 106 107 108 Linear Dynamic Range

재 현 성 %RSD 5 GFAA Vapor Gen. ICP %RSD Flame AA ICP-MS -5

샘 플 주 입 량

분석 가용원소수 vs 농도 high Flame AA ICP-AES conc GFAA ICP-MS low low high Vapor Generation low low high

요구되는 분석자의 능력 분 석 개 발 정 도 High Difficult ICP-MS Skill Level ICP-AES Moderate GFAA Vapor Gen Flame AA Easy Low

간 섭 :분광학적(Spectral) High ICP-AES Degree of Interference Flame AA Vapor Gen GFAA ICP-MS Low

간 섭 :주변물질(화학적l/물리적) High GFAA Degree of Interference Vapor Gen Flame ICP-MS ICP- AES Low

간 섭 : 이 온 화 (Ionization) High Degree of Interference Flame AA ICP- AES Vapor Gen GFAA ICP-MS Low

예 산 Vapor Generation Hg Analyzer GFAA Flame AA ICP-AES (Sequential) 예 산 Vapor Generation Hg Analyzer GFAA Flame AA ICP-AES (Sequential) (Simultaneous) ICP-MS 0 20 40 60 80 100 120 140 160 180 200 $$ x 1,000

운 용 유 지 비 High ICP- AES ICP-MS GFAA Expense Vapor Gen Flame AA Low

분 석 비 용 25 개 원소 분석시 High GFAA Cost/Analysis Can do 25 elements 분 석 비 용 25 개 원소 분석시 High GFAA Cost/Analysis Can do 25 elements by vapor generation ICP- AES ICP- MS Flame AA Low

장 점 비 교(1) 원자흡수분광법(Flame & Furnace) 유도쌍 플라즈마법 (ICP-AES) 낮은분광학적간섭 장 점 비 교(1) 원자흡수분광법(Flame & Furnace) 낮은분광학적간섭 좋은 정밀도 사용이 용이 낮은 운용 유지비 적은예산에적합 유도쌍 플라즈마법 (ICP-AES) 효율적인원자여기상태 적은주변물질의 간섭 운용시 쉽게 접근 신속한 다원소분석 넓은 동적범위

장 점 비 교 (2) 유도쌍플라즈마 질량분석기 (ICP-MS) 증기 원자화장치 (Vapor Generation) 신속한 다원소분석 낮은 검출한계 월등한 동적범위 낮은 분광학적 간섭 동위원소 분석 증기 원자화장치 (Vapor Generation) 호한성: AA, GFAA, ICP or ICP-MS 적은 간섭

단 점 비 교 (1) 원자흡광분광광도계 (Flame and Furnace) 유도쌍 플라즈마법 (ICP-AES) 단일 원소 분석법 화학적 간섭 한정된 동적범위 가연성 가스 사용(flame) 유도쌍 플라즈마법 (ICP-AES) 분광학적 간섭 공간-의존 간섭(Spacial-dependent interferences) 고가의 운용비용(Ar소모) 고가의 장비

단 점 비 교(2) 유도쌍 플라즈마 질량분석기 (ICP-MS) 증기 원자화 장치 (Vapor Generation) 주변물질의 간섭 동중체(같은질양)간섭 떨림 크린룸이 필요 고가 장비 증기 원자화 장치 (Vapor Generation) 7가지원소에 한정 화학적 추출 전처리

The analysis of cement

Cold vapor determination of Hg

Cr in Saline water by GFAAS

Cr in urine sample Magnesium nitrate was used as a matrix modifier Zeeman background correction was used.

ETV-FAAS Pb in blood sample

Impaction GFAAS