Introduction to Soil Chemistry
Introduction to Soil Chemistry
Introduction to Soil Chemistry
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CHAPTER<br />
7<br />
EXTRACTION<br />
<strong>Soil</strong> analyses involving instrumentation generally have extraction procedures<br />
associated with them.Thus, in addition <strong>to</strong> the references cited below and listed<br />
at the end of this chapter, additional understanding of extraction procedures,<br />
how they are designed and used, can be found along with the descriptions of<br />
spectroscopic and chroma<strong>to</strong>graphic methods and the corresponding references<br />
cited and listed in Chapters 8 and 9.<br />
As has been pointed out in previous chapters, soil is a complex mixture of<br />
inorganic and organic solids, aqueous and gaseous solution, and suspension of<br />
inorganic and organic ions, molecules, and gases, which can be sorbed, dissolved,<br />
or free. In most cases analysis for a particular component first involves<br />
isolation of that component from all the other myriad soil components, specifically,<br />
the soil matrix. Isolation may involve physical separation such as precipitation<br />
or distillation or, more often, as a first step, after sieving is extraction<br />
of soil using an appropriate extracting solvent or solution. Once isolated,<br />
the component can be directly or indirectly measured. Direct methods<br />
usually involve spectroscopy, while indirect methods involve production of<br />
a colored product by reaction with an applicable reagent and carrying out a<br />
colorimetric measurement.<br />
Both direct and indirect measurement involves the preparation of a standard<br />
or calibration curve. With an accurate calibration curve, the concentration<br />
of the component can be determined taking in<strong>to</strong> account interferences,<br />
dilution, and extraction efficiencies.<br />
7.1. ISOLATION<br />
Physical methods of separation and isolation of components from soil are commonly<br />
used in soil analysis, for instance they are particularly useful in nitrogen<br />
compound determination, as described in Chapter 6, and by head space<br />
analysis, as described below.<br />
<strong>Introduction</strong> <strong>to</strong> <strong>Soil</strong> <strong>Chemistry</strong>: Analysis and Instrumentation, By Alfred R. Conklin, Jr.<br />
Copyright © 2005 by John Wiley & Sons, Inc.<br />
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