AS deals with e transfer transition of valence electron between electronic states

AAS I0I0 I CA )/log(TlogA    εbC   吸收值與濃度呈線性關係 A ： absorbance T ： transmittance C ： conc. ε ： absorpivity b ： path length hν Φ L = k′Φ 0 C Φ L  C  Φ 0 CA )/log(TlogA    εbC   螢光源與入射光頂角成 正比, 且與濃度成正比 Light source 於 P 0 ° 角看放出之螢 光 (P 0 ° 乃因有散射 ) 激發態原子不穩定會降到 ground state, 而以光的形式放出, 放出之光的強度與 處於激發態的原子數目有關 ( 波茲曼係數 ) Ej Ei N j /N i = P j *e -ΔE i /kT /P i AFS AES

Temperature effect on the atomic spectra Boltzmann equation AA 吸收希望 atoms 在 ground state, AES 溫度要高, 在 excited state ’ s atoms or ions ↑. N j /N 0 = g j /g 0 * exp(ΔE/RT) Spectral line intensity I em λ 原子在 excited 愈多, 強度愈高 ( 僅電流多點即可 ) 當 conc. 很低時,conc. ↑ 或原子在 excited 增加, 則 intensity 會增強, 最後不再增強而變寬 變寬效應 ∴ I em  C ( 但不會無限制增加 )

Sequential ICP-AES Instrumentation

Major Components of ICP- AES Sample Delivery System - pump, nebulizer, spray chamber Inductively Coupled Plasma - torch, RF generator Spectrometer - Monochrometer, photomultiplier tube

Sample Delivery System Concentric-tube pneumatic nebulizer Cross flow nebulizer Nebulizer: converts sample to aerosol by a jet of gas (compressed Ar) Common types: Pneumatic - concentric tube, cross flow Ultrasonic

Ultrasonic nebulizer with desolvation

Inductively Coupled Plasma What is a Plasma? Plasma source provides atomization Plasma: “a gas-like phase of matter that consists of charged particles” ICP-AES plasma source is from the carrier gas Typically argon is used

Drawback Solid and liquid samples must be prepared so that they can be easily evaporated and ionized by the instrument 1 ICP-AES is a destructive technique, but only a small bit of sample is necessary Sample introduction into the instrument: the thorn in the side of ICP-AES

Plasma Plasma source provides atomization Plasma: “a gas-like phase of matter that consists of charged particles” 2 ICP-AES plasma source is from the carrier gas

Inductively coupled plasma (ICP) … torch design …

Radiofrequency Generator

ICP torch

ICP temperatures

Detection Radial Viewing 2 Types of Detection Positions: 1.Radial Viewing 2.Axial Viewing

How to perform Simultaneous Analysis Simultaneous analysis was carried out until today by using: – polychromators, which are Paschen-Runge optics coupled to high sensitivity detectors known as Photomultiplers (PMT) –Echelle-Grating optics, coupled to Solid State Detectors, (CCD, SCD & CID types), also known as Charge Transfer Devices (CTD ’ s)

Detail of a Paschen-Runge optics with PMT detectors Diffraction Grating Optical Fibers Photo multipliers

Grating Rowland circle Photographic Film Photomultiplier Tubes Entrance slit Exit slits Advantages:  High light throughput  Wide spectral range  Few optical components  Low stray light level  Robust

X Y PMT SCANNING + PMT

Optics and Detectors

Typical Echellogram

ICP optical emission spectrometry ICP-OES Capable of true simultaneous multielement analysis Minimal chemical interferences Spectral interferences overcome with use of alternate lines or intensity corrections on either side of analytical line Axial and side-on viewing systems available

ICP-OES operation Variety of sample introduction approaches available (pneumatic nebulizer with ~ 1 mL/min uptake is most common) Sensitivities better than FAA and often comparable with GFAA when using axial viewing Varying degrees of automation available

Background Noise Sources Argon emission lines Carbon and silicon lines Oscillation by the plasma itself and oscillations caused during aerosol production and sample delivery Such intensities are practically constant and easily recognized

Poor Detection Limits on Certain Trace Elements Examples of interferences include: 40 Ar 16 O on the determination of 56 Fe 38 ArH on the determination of 39 K 40 Ar on the determination of 40 Ca 40 Ar 40 Ar on the determination of 80 Se Solution: the cold/cool plasma

Limits of Detection Decrease in limits of detection over the course of time using examples of Perkinelmer ICP emission Spectrometers ICP/5000 (1980), Optima 3000 (1993), Optima 3000 XL (1997) All detection limits were determined by the blank method using the statistical factor K = 3 [concentrations in ppb]

DCP

Inductively coupled plasma mass spectrometry ICPMS

ICPMS characteristics “ Simultaneous ” multielemental analysis 5-6 orders of magnitude in dynamic range(need fewer standards for calibration) ppt and even ppq LODs available Isotopic information available Spectral interferences occur and involve polyatomic ions or isotopes of other elements Interferences involving ion optics (e.g., “ space charge ” ) and ionization efficiency are unique to ICPMS