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SPECTROGRAPHIC ANALYSIS OF PLANTS AND SOILS
Author(s) -
MITCHELL R. L.
Publication year - 1947
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1947.tb00556.x
Subject(s) - soil water , graphite , arc (geometry) , chemistry , atomic emission spectroscopy , spark (programming language) , analytical chemistry (journal) , process engineering , environmental science , environmental chemistry , materials science , inductively coupled plasma , metallurgy , computer science , mechanical engineering , soil science , plasma , engineering , physics , quantum mechanics , programming language
Summary Spectrographic methods which are applicable to the analysis of plants and soils include those employing flame, arc and spark excitation. Some seventy elements can be determined spectrographically, the most important exceptions being gaseous and non‐metallic elements. The most widely used flame emission method is that devised by Lundegårdh, in which the solution under examination is sprayed into an air‐acetylene flame. This method is particularly suited to the determination of the alkali and alkaline earth metals in soil and plant extracts. The Ramage method, in which the material is introduced on a paper spill, has also been used to some extent. Arc methods are widely employed for the determination of both trace and major constituents, generally with solid material in carbon or graphite electrodes of a shape chosen to suit the object of the investigation. The most sensitive source for most elements is probably the cathode‐layer arc, although the high‐voltage a.c. arc is useful for certain elements in solution. Interrupted arc and spark sources have been less widely used but have advantages for certain purposes, such as the determination of boron. Some direct photometric methods, omitting the use of a photographic plate, are described. Spectrographic methods are applicable to qualitative, semi‐quantitative or quantitative determinations. Semi‐quantitative methods generally employ a visual or subjective assessment of the content of an element, and are useful in giving a general indication of the levels of most of the trace constituents present in any sample, with an accuracy of some 30%. When objective photometric measurements are used, figures reproducible to ± 3–10% may be expected, depending on the method employed and the element being determined. Applications of spectrographic methods to analyses of soils and plants have been along both lines, either the semi‐quantitative survey of as many elements as possible, or the quantitative determination of specific elements. Attention is drawn to the relationship of the soil content to the geological origin of its parent material and to soil effects which may influence plant uptake.