Wavelength range refers to the dispersion of the grating across the linear array; also expressed as the "size" of the spectra on the array.
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Resolution is the width of an analytical peak at half its height expressed in nanometers. It's a measure of the instruments ability to separate two overlapping peaks. At the point of resolution, two peaks of equal height are said to be resolved if you can see a dip between the tops of the two peaks.
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A direct-current plasma (DCP) is created by an electrical discharge between two electrodes. A plasma support gas is necessary, and Ar is common. Samples can be deposited on one of the electrodes, or if conducting, can make up one electrode. Insulating solid samples are placed near the discharge so that ionized gas atoms sputter the sample into the gas phase where the analyte atoms are excited. This sputtering process is often referred to as glow-discharge excitation.
A flame provides a high-temperature source for desolvating and vaporizing a sample to obtain free atoms for spectroscopic analysis. In atomic absorption spectroscopy, ground state atoms are desired. For atomic emission spectroscopy, the flame must also excite the atoms to higher energy levels.
Inductively coupled plasma (ICP) is a very high temperature (7000-8000K) excitation source that efficiently desolvates, vaporizes, excites, and ionizes atoms. Molecular interferences are greatly reduced with this excitation source, but are not eliminated completely. ICP sources are used to excite atoms for atomic-emission spectroscopy and to ionize atoms for mass spectrometry.
Laser-induced breakdowns occur when a high-energy laser pulse is focused into a gas or liquid, or onto a solid surface, it can cause dielectric breakdown and create a hot plasma. For solids, the laser pulse also ablates material into the gas phase. The energy of the laser-created plasma can atomize, excite, and ionize analyte species, which can then be detected and quantified by atomic-emission spectroscopy or mass spectrometry.
Laser-inducted plasma uses a high-power CO2 laser that is focused into a support gas, such as Ar, and can maintain a hot plasma. The energy of the plasma can atomize, excite, and ionize analyte species present in the support gas, which can then be detected and quantified by atomic-emission spectroscopy or mass spectrometry. It can also be used in a glow-discharge mode to sputter analyte atoms off of a solid surface for analysis in the plasma
A microwave-induced plasma consists of a quartz tube surrounded by a microwave wave guide or cavity. Microwaves produced from a magnetron (a microwave generator) fill the wave guide or cavity and cause the electrons in the plasma support gas to oscillate. The oscillating electrons collide with other atoms in the flowing gas to create and maintain a high-temperature plasma. As in inductively coupled plasmas, a spark is needed to create some initial electrons to create the plasma. Atomic emission is measured from excited analyte atoms as they exit the microwave wave guide or cavity.
Spark and arc excitation sources use a current pulse (spark) or a continuous electrical discharge (arc) between two electrodes to vaporize and excite analyte atoms. The electrodes are either metal or graphite. If the sample to be analyzed is a metal, it can be used as one electrode. Non-conducting samples are ground with graphite powder and placed into a cup-shaped lower electrode. Arc and spark sources can be used to excite atoms for atomic-emission spectroscopy or to ionize atoms for mass spectrometry. Arc and spark excitation sources have been replaced in many applications with plasma or laser sources, but are still widely used in the metals industry.
Glow discharge spectroscopy (GDS) provides a rapid, direct, bulk analysis and depth profiling analysis of solids: metals, powders, polymers, glasses and ceramics. Glow discharge optical emission spectrometry (GD-OES) comprises a glow discharge source and one or more optical spectrometers.
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A monochromator is a spectrometer optical system capable of measuring a single wavelength, which can be scanned through a wide wavelength range. A common form of monochromator is the Czerny-Turner design, consisting of fixed entrance and exit slits, fixed focusing mirrors and a rotatable diffraction grating. As the grating rotates, a different wavelength is focused onto the exit slit. The wavelength range of a monochromator varies with the choice of grating, but commonly they can scan from 160 nm to 500 nm or ever wider ranges. The spectral resolution depends on the widths of the slits, the choice of grating and focal length, but commonly can be less than 10 pm for high resolution OES.
A common spectrometer optical system consists of a polychromator, which scatters the spectrum and isolates the analytical lines of the elements to be analyzed. A Paschen Runge-type polychromator consists of an entrance slit, a concave grating, and exit slits. The slits and the center of the grating are located on a circle, known as the Rowland circle. The radius of the Rowland circle equals the focal length of the grating. The grating is curved at twice the radius of the Rowland circle so that the light from the entrance slit is focused onto the exit slits.
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Photomultiplier tubes are photo-detectors with adjustable voltage, which translates optical tube (PMT) signals into electrical current. Increasing the PMT voltage increases the output signal for a given amount of light.
Solid state detectors pass charges from one capacitor to another by changing applied voltage in a coordinated fashion. The photon strikes silicon and is converted to a charge that can be transported and measured by electronic structure built on monolithic Silicon chip. There are two types of optical solid state detectors: Charge Coupled Device (CCD) and Charge Injection Device (CID).
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The ICP can be coupled with a mass spectrometer. The fundamental difference between ICP-OES and ICP-MS is that the plasma is not used to generate photons of light, but to generate trace metal ions. The ions produced in the plasma are transported and separated by their atomic mass to charge ratio using a mass spectrometer. The generation of such large numbers of positively charged ions allows ICP-MS to achieve detection limits at the part-per-trillion level.
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The panel uses digital keypads or menus for programming.
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A port, or interface, that can be used for serial communication, in which only one bit is transferred at a time. Examples include RS232, RS422, RS485, USB, etc.
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No integral display. Output is read and displayed remotely.
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4-20mA or any other analog current output. Often called a transmitter. A current is imposed on the output circuit proportional to the measurement. Feedback is used to provide the appropriate current regardless of line noise, impedance, etc. Useful when sending signals long distances.
The ''output'' is a change in state of a switch or an alarm.
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Portable spectrometers are modular devices that are designed for ease of transport and assembly. Rugged enclosures, PC interfaces, and customizable software packages are common features for the portable device.
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This is the full required range of ambient operating temperature.
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