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歐亞書局
Chapter 10
Atomic Emission Spectrometry
10A EMISSION SPECTROSCOPYBASED ON PLASMA SOURCES
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Inductively coupled plasma (ICP)
Direct current plasma (DCP)
Microwave induced plasma (MIP)
10A-1 The Inductivity Coupled Plasma Source
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FIGURE 10-1
A typical
ICP source. Position A
shows radial viewing of
the torch, and position B
shows axial viewing.
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Sample introduction
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FIGURE 10-2 The Meinhard nebulizer. The nebulizing gas flows
through an opening that surrounds the capillary concentrically. This causes a reduced pressure at the tip and aspiration of the sample. The high-velocity gas at the tip breaks up the solution into a mist.
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Plasma Appearance and Spectra
Analyte Atomization and Ionization
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FIGURE 10-3 Device for electrothermal vaporization.
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FIGURE 10-4 Temperatures in a typical ICP course.
10A-2 The Direct Current Plasma Source
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FIGURE 10-5 A three-electrode DC
plasma jet.
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10A-3 Plasma Source
Spectrometers
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Instruments for emission spectroscopy are of three
basic types: sequential, simultaneous multichannel, and
Fourier transform.
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TABLE 10-1 Desirable Properties of an Emission Spectrometer
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Sequential Instruments
Slew-Scan Spectrometers
Scanning Echelle Spectrometers
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FIGURE 10-6 Optical diagram of a sequential ICP optical emission spectrometer. All
moving parts are under computer control, and their modes of motion are indicated bythe three-dimensional arrow. Moving parts include the grating, a mirror for transducer selection, a refractor plate for optimizing signal throughput, and a viewing mirror to optimize the plasma viewing position. The spectrometer contains a mercury lamp for automatic wavelength calibration. Notice the axial viewing geometry.
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FIGURE 10-7 Schematic of an echelle spectrograph system.
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Multichannel Spectrometers
Polychromators.
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FIGURE 10-8 Direct-reading ICP emission spectrometer. The polychromator is of the Paschen-Runge design. It features a concave grating and produces a spectrum around a Rowland circle. Separate exit slits isolate each spectral line,and a separate photomulitiplier tube converts the optical information from each channel into an electrical signal. Notice the radial viewing geometry. PMT= photomultiplier tube.
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ICP-AES
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A Charge-Injection Device Instrument
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FIGURE 10-9 Optical diagram of an echelle spectrometerwith a charge-injection detector.
歐亞書局FIGURE 10-10
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FIGURE 10-10(a) Schematic representing the surface of a CID. The short horizontal lines represent the read windows. A magnified image of one of the read windows is also shown. The nine central elements form the examination window, where a line is positioned.
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FIGURE 10-10(b)
Intensity profile for an iron
line. All of the radiation
from the line falls on the
3 × 3 examination window.
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A Charge-Coupled Device Instrument
A Combination Instrument
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FIGURE 10-11 An echelle spectrometer with segmentedarray of CCDs.
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FIGURE 10-12 Schematic of an array segment showing
phototransducers, storage and output registers, and readout
circuitry.
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Fourier Transform Spectrometers
Fourier, Joseph
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10A-4 Applications of
Plasma Sources
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Sample Preparation
Elements Determined
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Line Selection
Calibration Curves
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FIGURE 10-13 Periodic table characterizing the detection power and number of useful emission lines of ICP by using a pneumatic nebulizer. The color and degree of shading indicate the range of detection limits for the useful lines. The area of shading indicates the number of useful lines.
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FIGURE 10-14 Typical calibration curves in ICP emission spectrometry.
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FIGURE 10-15 Internal
standard calibration
curves with an ICP
source. Here, an yttrium
line at 242.2 nm served
as an internal standard.
Notice the lack of
interelement
interference.
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Interferences
Detection Limits
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10B EMISSION SPECTROSCOPY BASEDON ARC AND SPARK SOURCES
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These spectra permitted the qualitative and quantitative determination of metallic elements in
a variety of sample types, including metals and alloys,
soils, minerals, and rocks,
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TABLE 10-2 Effect of Standardization Frequency on Precision of ICP Data
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10B-1 Sample Types and Sample Handling
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Metals
Nonmetallic Solids
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TABLE 10-3 Comparison of Detection Limits for Several Atomic spectral Methods
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FIGURE 10-16 Some typical graphite electrode shapes.
Narrow necks are to reduce thermal conductivity.
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10B-2 Instruments for Arc and
Spark Source Spectroscopy
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Spectrographs
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FIGRUE 10-17 The Eagle mounting for a grating spectrograph.
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Multichannel Photoelectric Spectrometers
Multichannel Photomultiplier Instruments.
Array-Based Multichannel Instruments.
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10B-3 Arc Source Emission Spectroscopy
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Characteristics of Arc Sources
Cyanogen Spectral Bands.
Rates or Emission.
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Applications of Arc Sources
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10B-4 Spark Sources and Spark Spectra
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Applications of Spark Source Spectroscopy
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10C MISCELLANEOUS SOURCESFOR OPTICAL EMISSION SPECTROSCOPY
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10C-1 Flame Emission Sources
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10C-2 Glow-Discharge Sources
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10C-3 Laser Microprobe Sources
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