ICP, or Inductively Coupled Plasma, is an Atomic Emission Spectroscopy method where atomization occurs with the help of plasma generated by an inert gas . The ICP-OES instrument operates based on atomic emission. This technique allows for the measurement of elemental emissions from both a radial and axial view relative to the vertical plasma. It can measure a wide range of elements from the periodic table in various matrices, including soil, water, metal, and polymer samples, and across a broad range of concentrations, down to detection limits in the ppb range. The main advantage of this instrument is its ability to measure multiple elements simultaneously in a short amount of time. The ICP-OES unit features an RF (Radio Frequency) generator that creates a hot, ionized, inert argon gas environment. This state is technically called a plasma state. The solid-state RF system generates a strong, reliable, and maintenance-free plasma whose analytical stability is maintained over long periods. It's important to note that the sample is completely destroyed during this test.
Instrument Components and Operating Method
The Inductively Coupled Plasma consists of a torch with three concentric quartz tubes. Argon gas flows inside each tube (at different speeds) to cool and transfer the sample into the plasma. Above the tallest tube of the torch is an Induction Coil, powered by an RF (Radio Frequency) Frequency Generator.
The coils can be flat, helical, or solenoid-shaped. When a time-varying electrical current passes through the coil, it creates a time-varying magnetic field around it, which in turn generates an electric field in the argon gas and causes its ionization. The ions (electrically charged particles) and electrons resulting from the ionization interact with the induction coil's magnetic field, ultimately creating a flow of electrons and ions in figure-eight ($\infty$) shaped circular paths, forming the plasma based on the Hamilton-Jacobi equation. Non-ionized argon atoms within the plasma become ionized upon collision with the ions, thus keeping the plasma environment stable throughout the experiment.
The plasma temperature ranges from 6,000 to 10,000 Kelvin (close to the sun's surface), and the energy of the analyzed particles at this temperature varies between 6 and 100 electron volts.
At this point, the sample is guided by the argon gas to the top of the tubes, which contains the hot plasma. The sample can enter the torch as an Aerosol or a very fine powder. After vaporization in the intense heat, it's converted into its constituent atoms under the influence of the surrounding electrons and ions, and finally becomes excited in the ultra-hot plasma environment. The light rays emitted by the excited atoms pass through a Monochromator and then reach a Photomultiplier Tube for measurement. By plotting the intensity of the resulting spectral lines from the instrument against the concentration of the target element (the calibration curve), the elemental concentrations can be easily determined. This enables the detection and measurement of the target element's concentration.
Advantages
The features of the ICP-OES technique include:
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Simultaneous and sequential analysis of multiple elements using the ICP-OES (SVDV) system.
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Wide linear range in the analytical curves of ICP-OES Spectrophotometer systems.
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Low chemical or ionization interference, which enables the analysis of samples with high-matrix content by the ICP-OES spectrometer.
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High sensitivity of ICP-OES spectroscopy.
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Wide range of measurable elements.
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High stability of the ICP-OES spectrophotometer.
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Use of advanced and integrated systems (AVS) that boost analysis speed and significantly reduce argon consumption.
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Easy operation alongside low maintenance costs are also considered benefits of this instrument.
Various Applications of the ICP-AES Instrument
Due to its capability to identify trace amounts of metals (low detection limits), high sensitivity, and high selectivity, this method is widely used in diverse industries and various research areas, including:
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Heavy metal analysis with detection limits in the parts-per-billion ($\text{PPB}$) range.
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Analysis of various environmental samples including soil, water, and plant/animal residue.
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Elemental analysis in forensic and quality control laboratories.
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Biological sample analysis.
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Comprehensive analysis of rock, soil, and ash.
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Pharmaceutical industries.
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Polymer industries.
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