Comparison of extraction procedures used in determination of phosphorous species by 31P-NMR in Chilean volcanic soils
2006
Briceno, M. | Escudey, M. | Galindo, G. | Borchardt, D. | Chang, A.C.
Four procedures were employed to extract phosphorus (P) from volcanic soils for 31P-NMR experiments. The procedures involve 0.5 M NaOH extraction, 0.5 M NaOH and Chelex 100 cation exchange resin extraction, NaOH-EDTA extraction, and HCl-NaOH two step sequential extraction with Chelex 100 clean up. Results showed that inorganic-P, monoester-P, diester-P and pyrophosphate were present. Their detection was dependent on the extraction procedure used. The NaOH procedure gives only a broad and vaguely defined signal with poor signal to noise ratio. The incorporation of Chelex 100 in the extraction enhanced the signal to noise ratio and allowed the distinction of inorganic-P, monoester-P, diester-P and pyrophosphate. The two step sequential extraction involving HCl, NaOH, and Chelex 100 significantly improve the signal to noise ratio. The NaOH-EDTA extraction procedure is efficient only in samples with low OC contents. When soils have low OC content, any of the four extraction procedures can be successfully used. If the OC and the Fe concentration in the extracted solutions are high, the Chelex 100 became essential in clean up the metallic ions. Both the NaOH and Chelex 100 and the HCl-NaOH-Chelex produced satisfactory results and the later procedure by far the best resolved spectra.
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