Direct Couple Optical Emission Spectroscopy

In Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), a gaseous, solid (as fine particles), or liquid (as an aerosol) sample is directed into the center of a gaseous plasma. The sample is vaporized, atomized, and partially ionized in the plasma. Atoms and ions are excited and emit light at characteristic wavelengths in the ultraviolet or visible region of the spectrum. The emission line intensities are proportional to the concentration of each element in the sample. A grating spectrometer is used for either simultaneous or sequential multielement analysis. The concentration of each element is determined from measured intensities via calibration with standards. 

Neutron activation and petrographic analysis of late medieval Spanish pottery from the major Spanish production centers of Seville, Granada, Patema-Manises, Barcelona, and Talavera-Puente allowed progress to be made in uniquely characterizing these production centers (5-7). Efforts to identify different Mexican majolica productions petrographically have been unsuccessful, and an attempt at chemical characterization by directly coupled plasma-optical emission spectroscopy was later determined to have been flawed by problems encountered with the dissolution of the ceramic samples... 

Broekaert J. A. C. and Leis F. (1985) An application of electrothermal evaporation using direct solids sampling coupled with microwave induced plasma optical emission spectroscopy to elemental determinations in biological matrices, Mikrochim Acta II 261-272. 

Aluminum is best detected qualitatively by optical emission spectroscopy. Solids can be vaporized directly in a d-c arc and solutions can be dried on a carbon electrode. Alternatively, aluminum can be detected by plasma emission spectroscopy using an inductively coupled aigon plasma or a d-c plasma. Atomic absorption using an aluminum hoUow cathode lamp is also an unambiguous and sensitive qualitative method for determining aluminum. 

The sensitivity, accuracy, and precision of solid sample analysis were greatly improved by coupling of LA with ICP-OES/MS. The ablated species are transported with a carrier gas (usually argon) into the plasma torch. Additional atomization. excitation and ionization of the ablated species in a stationary hot plasma provide a dramatic increase in the sensitivity of emission detection (LA-ICP-OES) or detection of ions (LA-ICP-MS). The efficiency of the transport of ablated species into an ICP strongly depends on the size of the particles. The optimal conditions for ablation in the ca.se of LA-ICP differ significantly from the optimal conditions for LIBS because the efficient transport of the ablated matter to an ICP requires a fine aerosol (with solid particle diameters less than a few micrometers), whereas direct optical emission spectroscopy of the laser plume needs excited atoms and ions. 

GFAAS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES - also referred to as inductively coupled plasma-optical emission spectroscopy, or ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) are all routinely utilized in pharmaceutical applications. While there are other techniques of note available, such as micro-wave induced plasma (MIP) or direct coupled plasma (DCP), they have not been routinely used in the pharmaceutical industry, and will, therefore, not be discussed here. The theories involved in the use of FAAS, GFAAS, ICP and ICP-MS may be found in other articles of this Encyclopedia. 

Rabb, S. A. (2000). The investigation of concomitant species and acid matrix effects in inductively coupled plasma optical emission spectroscopy and mass spectrometry and preliminary studies of direct solids analysis. Unpublished Ph.D.Thesis, Ohio State University, Columbus. 

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