Minor levels, instrumental analytical methods

Early in the 20th century chemists began to research and exploit physical properties of the analyte properties, such as conductivity, electrode potential, light absorption or emission, mass-to-charge ratio and fluorescence for solving analytical problems. Classical principles remain useful in modem analytical instruments and methods. In comparison to classical methods the output of instrumental methods is a signal from which the result of the analyses is calculated. Instrumental analysis is most useful for elemental determinations at minor and trace levels (about 1% all the way down to 1 atom)—in this range classical analysis does not perform well. 

A wet chemical analysis would likely be chosen when a more precise result is needed or when the analyte is a major, rather than a minor, constituent. An instrumental analysis procedure would likely be chosen when a minor constituent present at a low level is to be determined and when a faster method with a greater scope or practicality is needed. 

Qualitative analysis is the process of the determination of the presence (or absence) of a particular element or group of elements in a sample. The ability to perform a comprehensive qualitative analysis is directly related to the sensitivity of the analysis method and hence the detection capability. Ideally, it is desirable to determine major, minor, trace, and ultratrace concentration level elements simultaneously on the same sample aliquot, which requires an instrument and technique that exhibits a wide dynamic range of measurement of the ion currents for the various element isotopes. However, in practice, it is often difficult to determine the high intensity of major elements on the same sample dilution as that required for ultratrace concentration element determination (usually measured on undiluted sample). This problem is often accommodated by the use of very low abundance isotopes of the major concentration analyte, reducing the analysis sensitivity. Where no low abundance isotope is available, instrumentation with dual detectors (electron multiplier for low concentration analytes and Faraday analog detectors for high concentration elements) can be used effectively. 

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