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1.1 Inductively coupled plasma (ICP)
Three Argon flow
1. Plasma gas (10-20 L/min)
2. Nebulizer gas (~1L/min)
3. Optional auxiliary gas (~0.5L/min)
Radio-frequency (RF) power source up to 2kW
Higher temp (~8000K)
Heated from outside-in
Torch up to 1 “ diameter
Plasma structure• Brilliant white core – Ar continuum
radiation• Flame-like tail up to 2cm• Transparent region (15-20 mm above
the core) – measurement made
• Analyte atoms have 2 ms residence time and experience temperature from 5000-800K. Atomized in “inert” atmosphere. Little ionization.
• Torch may be viewed radially or axially
Sample introduction
1. Nebulizer – convert solutions to fine spray or aerosol
- Ultrasonic nebulizer uses ultrasound waves to boil solutions flowing across disc
- Pneumatic nebulizer uses high pressure gas to entrain solution
2. Electrothermal vaporizer (ETV)
Electric current rapidly heats crucible containing sample
Sample carried to atomizer by Ar or He
Only for introduction, not atomization
3. Other methods
Direct insertion {powder placed inside flame, plasma, arc or spark atomizer}
Laser ablation {uses laser to vaporize sample}
1.2 Direct current plasmaDC current 10-15 A between C anode and cathode
Plasma core at 10,000 K, viewing region at 5,000 K
Simple, less Ar than ICP
1.3 Plasma source spectrophotometer
1.3.1 Sequential (scanning and slew-scanning)Slew-scan spectrometers – Rapidly scan (slewed) across blank regions
Slowly scann across lines
Computer control/preselected lines to scan
1.3.2 Multichannel spectrometer
1.4 Plasma AES vs. Flame AAS
AAS AESSimilar atomization technique to AES
Addition of radiation source
High temperature for atomization Very high temperature for excitation
(flame and electrothermal atomization) (plasma/arc/spark)
Low cost instrumentation moderate-high cost
Single element simultaneous multielement analysis
Quantitative qualitative and quantitative
Low sample throughput high sample throughput
Atomization interference spectral interference (large # of lines)
Detection limit 0.001-0.020 ppm 10ppb
Greater precision
complementary technique
Limited to qualitative/semi-quantative analysis (arc flicker)
Usually performed on solids
Largely displaced by plasma-AES
Sample pressed into electrode
Electric current flowing between two C electrodes
Cyanogen bands (CN) 350-420 nm occur with C electrode in air – He, Ar atmosphere
Fig. 10-17 (p.270)
Graphite electrode shapes
Arc/spark unstable – each line measure >20 s (needs multichannel detection)
Photographic film
- Cheap
- Long integration times
- Difficult to develop/analyze
- Non-linearity of line “darkness”
Multichannel PMT instrument- For rapid determinations (< 20 s) but not versatile- Routine analysis for solids – metals, alloys, ores, rocks, solids- Portable instruments
Spectrographs (record spectrum with a photographic plate at the focal plane)