Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method
2015
Campbell, Ellen R. | Warsko, Kayla | Davidson, Anna-Marie | (Bill) Campbell, Wilbur H.
Measurement of ortho-phosphate in soil extracts usually involves sending dried samples of soil to a laboratory for analysis and waiting several weeks for the results. Phosphate determination methods often involve use of strong acids, heavy metals, and organic dyes. To overcome limitations of this approach, we have developed a phosphate determination method which can be carried out in the field to obtain results on the spot.This new method uses:•Small volumes.•An enzymatic reaction.•Green chemistry.First, the soil sample is extracted with deionized water and filtered. Next, an aliquot of the soil extract (0.5mL) is transferred to a disposable cuvette, containing 0.5mL of reaction mixture [200mM HEPES, pH 7.6, 20mM MgCl2, with 80nmol 2-amino-6-mercapto-7-methylpurine ribonucleoside (MESG) and 1 unit of recombinant purine nucleoside phosphorylase (PNP; EC 2.4.2.1)], mixed, and incubated for 10min at field temperature. Absorbance of the completed reaction is measured at 360nm in open-source, portable photometer linked by bluetooth to a smartphone. The phosphate and phosphorus content of the soil is determined by comparison of its absorbance at 360nm to a previously prepared standard phosphate curve, which is stored in the smartphone app.
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