Centrifugation: a solution to the problems posed by ammonium and nitrate contamination of filters in soil extract analysis
1988
Scharf, P. | Alley, M.M.
The objective of this study was to develop a rapid and effective method of removing particulate matter from 2 M KCl soil extracts without contaminating the extracts with NH4+ and/or NO3-. Seven types of filters were first tested by eluting them with 2 M KCl solution and analyzing the eluents. All filters tested eluted unacceptable levels of NH4+, NO3-, or both, and are thus unsuitable for filtration of 2 M KCl soil extracts which are to be analyzed for both NH4+ and NO3-. Subsequently, soil extracts were centrifuged at varying speeds and for varying times in an attempt to remove particulate matter from the extracts without filtration. Particulate matter content of the resulting supernatants was measured with a Coulter counter. Centrifuging the soil extracts at 1800 rpm for 10 min reduced particulate contamination to levels comparable to those in filtered extracts.
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