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Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Elemental Spectroscopy ICP-OES
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Page 1: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

Elemental Spectroscopy ICP-OES

Page 2: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Content: ICP-OES

• Fundamentals of ICP-OES

• Instrument Components

Page 3: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

Theory of Inductively Coupled PlasmaOptical Emission Spectroscopy

Page 4: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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ICP is shorthand for ICP-AES or ICP-OES.

What is ICP-AES? It is:Inductively Coupled Plasma Atomic Emission Spectrometer.

ICP Basics

What is ICP-OES? It is:Inductively Coupled Plasma Optical Emission Spectrometer.

Page 5: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Atomic Emission Theory

• Atomic emission spectroscopy (AES or OES) uses quantitative measurement of the optical emission from excited atoms to determine analyte concentration

• Analyte atoms in solution are aspirated into the excitation region where they are desolvated, vaporized, and atomised by a plasma

Page 6: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Atomic Emission Theory

Plasma Polychromator Detector

Inductively Coupled Plasma Atomic Emission Spectrometer

Page 7: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Excitation

E x c i t e d S t a t eG r o u n d S t a t e

ER e l a x a t i o n

E x c i t a t i o n

Electrons can be in their ground state (unexcited) or enter one of the upper level orbitals when energy is applied to them. This is the excited state

Page 8: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Atomic Emission

PhotonExcited State Ground State

+ hv

A photon of light is emitted when an electron falls from its excited state to its ground state

Page 9: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Element Wavelengths

• Each element has a unique set of wavelengths that it

can emit

180nm 800nm400nm <-- visible --><-- uv -->

1 2 3 4 5

Page 10: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Atomic Emission explained

• Atomic Emission – the wavelength regions

Spectral Region

Vacuum UV Ultra-Violet Visible Near IR

Wavelength = nm 160 190 360 760 900

Lower wavelengths are shorter and have more energy, higher wavelengths e.g. in the Visible region, are longer and have less energy

Page 11: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Effect of Temperature on Emission

Wavelength increasing ->

2000 k

3000 k

5000 k

Ca Na Li

K

Ca

Na Li

K

KLiNa

Ca Ba

Ba

CuMg

Mg CuAs Pb Mn

200 300 400 600 800

Page 12: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Emission sources

• Flames

• Arcs / Sparks

• Direct Current Plasmas (DCP)

• Inductively Coupled Plasmas (ICP)

Page 13: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Inductively Coupled Plasma (ICP) – source, plasma formation, plasma zones

• Quartz torch surrounded by induction coil

• Magnetic coupling to ionized gas

• High temperature – equivalent to 10,000k

Page 14: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Plasma Advantages

• High Temperature – allows for full dissociation of sample components

• Argon is Inert – non reactive with sample• Linearity – analysis of samples from ppb to ppm range in the same

method• Matrix tolerance – robust and flexible design with Duo and Radial

options

Page 15: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Plasma Torch

Page 16: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Plasma Zones

Plasma Zones

sample

6000 k

6500 k

7000 k

8000 k

10000 k

0

15

20

25

observationregion (mm) TEMPERATURE ~ 2X

NITROUS OXIDE ACETYLENE FLAME

RESIDENCE TIME ~ 2MS

Page 17: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

There are six basic components to an ICP

1. Sample Introduction

2. Energy Source

3. Spectrometer

4. Detector

5. Electronics

6. Computer and Software

Page 18: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

6. Computer and Software

1. Sample Introduction

2. Energy Source

3. Spectrometer

4. Detector5. Electronics

Page 19: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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1. Sample Introduction The sample solution

cannot be put into the energy source directly. The solution must first be converted to an aerosol.

The function of the sample introduction system is to produce a steady aerosol of very fine droplets.

Instrument Components

Page 20: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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1. Sample Introduction

There are three basic parts to the sample introduction system.

i. the Peristaltic pumpdraws up sample solution and delivers it to

ii.the Nebulizerwhich converts the solution to an aerosol that is sent to

iii. the Spray chamberwhich filters out the large, uneven droplets from the aerosol.

Instrument Components

Page 21: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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1. Sample Introduction

i. the Peristaltic pump

ii. the Nebulizer

iii. the Spray chamber

Instrument Components

Page 22: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Concentric Nebuliser

Page 23: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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2. Energy Source The sample aerosol

is directed into the center of the plasma. The energy of the plasma is transferred to the aerosol.

The main function of the energy source is to get atoms sufficiently energized such that they emit light.

Instrument Components

= plasma

Page 24: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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2. Energy Source

There are three basic parts to the energy source.

i. the Radio frequency generatorwhich generates an oscillating electo-magnetic field at a frequency of 27.12 million cycles per second. This radiation is directed to

ii.the Load coilwhich delivers the radiation to

iii. the Torchwhich has argon flowing through it which will form a plasma in the RF field.

Instrument Components

Page 25: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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2. Energy Source

i. the Radio Frequency generator

ii. the Load coil

iii. the Torch

Instrument Components

Page 26: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Plasma Configuration

• Axial

• Radial

• Axial and Radial

Page 27: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Radial or Axial Configuration

• Radial design – Robust, fewer interferences • Petrochemical• Metallurgy

• Axial design – best sensitivity,

lowest detection limits • Environmental• Chemical

Page 28: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Axial Advantage

• Much more light available. This gives you the opportunity to achieve Lower Detection Limits than Radial Plasma

• BUT- unfortunately, you also get...

• More Matrix Interferences

• Slightly Reduced Dynamic Range

Page 29: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Duo viewing

• Axial view plasma looks down the central channel of the plasma, this provides the best sensitivity and detection limits

• DUO – this is an axially configured plasma that also allows for radial view through a hole in the side of the axial torch

Page 30: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Dual View Optics

Axial view

Radial view

Page 31: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

3. SpectrometerOnce the atoms in a sample have been energized by the plasma, they will emit light at specific wavelengths. No two elements will emit light at the same wavelengths.

The function of the spectrometer is to diffract the white light from the plasma into wavelengths.

Page 32: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Simultaneous Optics – Echelle Spectrometer

ICP-Source

Detector

PrismGrating

Page 33: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

3. Spectrometer

There are several types of spectrometers used for ICP. Regardless of type, all of them use a diffraction grating.

For the iCAP, an echelle spectrometer is used. The components in this spectrometer are shown at left.

CID Detector

FocusingMirror

Prism

CollimatingMirror

Shutter

Slit(dual)

Echellegrating

Page 34: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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iCAP Optics - Polychromator

• High resolution• 7pm @ 200nm

• High image quality & low stray light• aberration compensation over whole CID

• High energy throughput• double pass prism

• All lines on chip• anamorphic magnification

• Stable• thermal insulation & heater control to 0.10C

Page 35: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

4. DetectorNow that there are individual wavelengths, their intensities can be measured using a detector. The intensity of a given wavelength is proportional to the concentration of the element.

The function of the detector is to measure the intensity of the wavelengths.

Page 36: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Charge Injection Device Array Detector

• >291,600 addressable silicon-based

photo detectors

• Full Spectrum Imaging

• Random Access Integration (RAI)

• Inherently Anti-blooming

– Non Destructive Readout (NDRO), allows the S/N ratio to be improved by repeatedly reading each pixel

Page 37: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

4. Detector The detector is a silicon chip that is composed of many individual photo-active sections called “picture elements”. These picture elements, or pixels, will build up charge as photons impinge on them. Individual pixels are of a size such that they can be used to measure individual wavelengths.

Page 38: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Emission lines appear as points of light

177 nm

800 nm 740 nm

178 nm

Page 39: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Readout Subarray - CID

Intensity

Wavelength

28 by 28 mdetector element

Page 40: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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What you get

Full, continuous wavelength coverage; never miss an analyte

Page 41: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Power and flexibility

• Rapid qualitative analysis• Ability to analyze for elements in the

future without rerunning samples• Fingerprinting• Matrix or spectral subtraction

Page 42: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

5. ElectronicsThe output from the detector is processed by a set of electronics. The electronics control the detector as well as collect the readings from the pixels

The function of the electronics is to measure and process the output of the detector.

Page 43: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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Instrument Components

6. Computer and Software The software, via a computer, controls and runs the instrument. Not only are measurements made but the other five components of the instrument are controlled and monitored by the computer and software,

The function of the computer and software is to operate, monitor, and collect data from the instrument.

Page 44: Elemental Spectroscopy ICP-OES. 2 Content: ICP-OES Fundamentals of ICP-OES Instrument Components.

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ICP Basics

ICP Performance

• Typical analysis time for ICP is ~2-3 minutes. This includes flush time, multiple repeats, printing, etc. (Analysis time is independent of the number of elements being determined)

• Typical precision, amongst repeats within an analysis, is ~0.5%

• Typical drift is ≤ 2% per hour

• Typical detection limits are ~ 1-10 parts per billion


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