Sequential plasma emission spectrometers

Inductively coupled argon plasma emission spectrometers of the sequential or simultaneous type were used very little as detectors for gas chromatographs [28]. The detection limits for metals in these systems approached the low nanogram levels. However, the detection limits for... 

There are two basic types of instrument used in plasma emission analysis, namely the simultaneous and the sequential multi-element spectrometer. 

The glow discharge (GD) is a reduced-pressure gas discharge generated between two electrodes in a tube filled with an inert gas such as argon. The sputtered atom cloud in a GD source consists of excited atoms, neutral atoms, and ions. The emission spectrum can be used for emission spectrometry in the technique of GD-OES, but the GD source can also be used for AAS, AFS, and MS. The source can be used with any of the types of spectrometers discussed for plasma emission sequential monochromator, Rowland circle polychromator, echelle spectrometer, or combination sequential-simultaneous designs. The detectors used are the same as described for plasma emission spectrometry PMTs, CCDs, or CIDs. 

A sequential induetively coupled plasma (ICP) emission spectrometer Atomscan-25 (Thermo Jarrel Ash) was used to measure the metal content in the polymers. Test solutions were prepared by mineralization of test portions (0,5 - 1 g) of the polymers under interest. A mixture of nitric acid and perchloric acid was used for mineralization. Test solutions were aspirated into the argon plasma and analyzed. Calibration for the metals to be determined was performed using certified standard solutions. 

Inductively-Coupled Plasma Atomic Emission Spec-trowe/er—Either a sequential or simultaneous spectrometer is suitable, if equipped with a quartz ICP torch and r-f generator to form and sustain the plasma. 

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. 

The plasma is maintained at a temperature of 10 000° C by an external radio frequency current, as described in Section 3.3. At this temperature, many molecular species are broken down, and approximately 50% of the atoms are ionized. So far this is identical to ICP-OES, but for ICP-MS we are not interested in the emission of electromagnetic radiation, but rather in the creation of positive ions. To transfer a representative sample of this plasma ion population to the mass spectrometer, there is a special interface between the plasma and the mass spectrometer. This consists of two sequential cones... 

The tail of the plasma formed at the tip of the torch is the spectroscopic source, where the analyte atoms and their ions are thermally ionized and produce emission spectra. The spectra of various elements are detected either sequentially or simultaneously. The optical system of a sequential instrument consists of a single grating spectrometer with a scanning monochromator that provides the sequential detection of the emission spectra lines. Simultaneous optical systems use multichannel detectors and diode arrays that allow the monitoring of multiple emission lines. Sequential instruments have a greater wavelength selection, while simultaneous ones have a better sample throughput. The intensities of each element s characteristic spectral lines, which are proportional to the number of element s atoms, are recorded, and the concentrations are calculated with reference to a calibration standard. 

For a long time qualitative analysis was mainly carried out with DCP systems, while the sequential or direct reading ICP systems were too time- and sample-consuming for a general survey analysis. With the improved simultaneous observation of multiple emission Unes via echeUe spectrometer, a general qualitative analysis of unknown samples becomes easily possible under robust plasma conditions. 

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