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Spectroscopic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
For this reason, hollow cathode lamps, line sources, are used as the radiation source in atomic absorption spectroscopy. These contain a cathode filled with the element to be used in creating the line emission, and a wire anode. Figure 3.23 shows a diagram of a hollow cathode lamp. The body of the lamp is filled with a low pressure of an inert gas, usually neon or argon. When a voltage of 300–400 V is supplied to the electrodes, the fill gas atoms are ionized and fall into the cathode, sputtering off the element atoms. These atoms are in an excited state and, as they fall back to the ground state, they emit the characteristic wavelengths of the particular element's spectrum. The width of these lines depends on the amperage passing through the lamp. If the current is too high, a dense cloud of atoms is produced, raising the pressure in the lamp. This causes many intermolecular collisions, which spread out the energies of the atoms and thus increase the bandwidth of the line. In addition, the dense cloud will contain some ground state atoms, and these will absorb some of the emitted light before it exits through the window, lowering the output of radiation. Self-absorption produces a broadened band with lower intensity in the middle of the band and higher emission at the sides.
Quality assurance/quality control and laboratory analysis
Published in Neal Wilson, Soil Water and Ground Water Sampling, 2020
The FLAA method uses either a nitrous oxide/acetylene or air/acetylene flame as an energy source for dissociating (atomizing) the aspirated sample into the free atomic state, making analyte atoms available for absorption of light. A hollow cathode lamp or a discharge lamp without electrodes provides a beam of light that passes through the flame into a monochromator (which isolates the characteristic radiation from the lamp) and onto a detector that measures the amount of absorbed light. The wavelength of the light beam is chosen such that it is specific to the metal being analyzed, so the amount of light absorbed is a measure of the concentration of the metal in the sample.
Atomic Absorption Spectroscopy
Published in James P. Lodge, Methods of Air Sampling and Analysis, 2017
If light of the proper wavelength strikes a free, ground-state atom, the atom may absorb the light in a process known as atomic absorption. By measuring the amount of light absorbed, a quantitative measurement of the analyte concentration can be made. Ground state atoms are typically produced by dissociating the sample in a flame or graphite tube furnace. A hollow-cathode lamp, with a cathode containing the element of interest, typically provides the narrow emission lines of characteristic radiation.
Demineralization of cocoons of Antheraea assamensis Helfer (muga) for effective reeling
Published in The Journal of The Textile Institute, 2018
Manasee Choudhury, Dipali Devi
The extracted metals present in the demineralized water obtained by the above methods were determined by Atomic absorption spectrophotometer (Shimadzu AA 7000) equipped with a deuterium lamp for background correction. The hollow cathode lamps for Ca, Cu, Fe, Al, Mn, Mg, Zn, Ni, Cd were employed as the radiation source. The source of flames used were N2O and /acetylene. Nitrogen was used as the carrier gas.