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Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method.

Campbell ER, Warsko K, Davidson AM, Bill Campbell WH - MethodsX (2015)

Bottom Line: 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.Absorbance of the completed reaction is measured at 360 nm 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 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app.

View Article: PubMed Central - PubMed

Affiliation: NECi, Lake Linden, MI 49945, USA.

ABSTRACT
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 (0.5 mL) is transferred to a disposable cuvette, containing 0.5 mL of reaction mixture [200 mM HEPES, pH 7.6, 20 mM MgCl2, with 80 nmol 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 10 min at field temperature. Absorbance of the completed reaction is measured at 360 nm 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 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app.

No MeSH data available.


Related in: MedlinePlus

Typical phosphate standard curve for field soil phosphate test. The equation of the liner regression line fitted to the data set is:Y = 0.0489 X − 0.0005Correlation coefficient (r2) = 0.9993. The standard curve can be converted to measure phosphate–phosphorus by dividing the phosphate concentration by a factor of 3.1 to yield mg phosphate–phosphorus per liter (mg PO4–P/L). When this is done with the data shown in the figure, the slope (x) = 0.0151 mg PO4–P per L, while the intercept and correlation coefficient do not change.
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fig0010: Typical phosphate standard curve for field soil phosphate test. The equation of the liner regression line fitted to the data set is:Y = 0.0489 X − 0.0005Correlation coefficient (r2) = 0.9993. The standard curve can be converted to measure phosphate–phosphorus by dividing the phosphate concentration by a factor of 3.1 to yield mg phosphate–phosphorus per liter (mg PO4–P/L). When this is done with the data shown in the figure, the slope (x) = 0.0151 mg PO4–P per L, while the intercept and correlation coefficient do not change.

Mentions: A set of phosphate standards was prepared by diluting a certified 1000 ppm (1 mg/mL) potassium phosphate standard (KH2PO4; Lab Chem Inc., Catalog No. LC 18570-1), to encompass the range of interest (i.e., 1.00–5.00 mg phosphate/L). The phosphate standards were analyzed by the PNP catalyzed reaction with MESG and the absorbance at 360 nm plotted versus the nominal phosphate concentration of standards (see Fig. 2). After the background absorbance of the reagent blank is subtracted, the standard curve is linear with a correlation coefficient = 0.999. Using the equation of the fitted line, the amount of phosphate extracted from the soil sample is easily determined. The phosphate content (mg PO4/L) can be converted to phosphorus content by dividing by 3.1 (mg PO4–P/L). Furthermore, the phosphate–phosphorus content of the soil can be converted to the commonly used units of mg phosphorus per kg soil by multiplying by a factor of 5, since 1 g of soil is extracted and 0.5 mL of deionized water extract is analyzed.


Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method.

Campbell ER, Warsko K, Davidson AM, Bill Campbell WH - MethodsX (2015)

Typical phosphate standard curve for field soil phosphate test. The equation of the liner regression line fitted to the data set is:Y = 0.0489 X − 0.0005Correlation coefficient (r2) = 0.9993. The standard curve can be converted to measure phosphate–phosphorus by dividing the phosphate concentration by a factor of 3.1 to yield mg phosphate–phosphorus per liter (mg PO4–P/L). When this is done with the data shown in the figure, the slope (x) = 0.0151 mg PO4–P per L, while the intercept and correlation coefficient do not change.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487730&req=5

fig0010: Typical phosphate standard curve for field soil phosphate test. The equation of the liner regression line fitted to the data set is:Y = 0.0489 X − 0.0005Correlation coefficient (r2) = 0.9993. The standard curve can be converted to measure phosphate–phosphorus by dividing the phosphate concentration by a factor of 3.1 to yield mg phosphate–phosphorus per liter (mg PO4–P/L). When this is done with the data shown in the figure, the slope (x) = 0.0151 mg PO4–P per L, while the intercept and correlation coefficient do not change.
Mentions: A set of phosphate standards was prepared by diluting a certified 1000 ppm (1 mg/mL) potassium phosphate standard (KH2PO4; Lab Chem Inc., Catalog No. LC 18570-1), to encompass the range of interest (i.e., 1.00–5.00 mg phosphate/L). The phosphate standards were analyzed by the PNP catalyzed reaction with MESG and the absorbance at 360 nm plotted versus the nominal phosphate concentration of standards (see Fig. 2). After the background absorbance of the reagent blank is subtracted, the standard curve is linear with a correlation coefficient = 0.999. Using the equation of the fitted line, the amount of phosphate extracted from the soil sample is easily determined. The phosphate content (mg PO4/L) can be converted to phosphorus content by dividing by 3.1 (mg PO4–P/L). Furthermore, the phosphate–phosphorus content of the soil can be converted to the commonly used units of mg phosphorus per kg soil by multiplying by a factor of 5, since 1 g of soil is extracted and 0.5 mL of deionized water extract is analyzed.

Bottom Line: 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.Absorbance of the completed reaction is measured at 360 nm 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 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app.

View Article: PubMed Central - PubMed

Affiliation: NECi, Lake Linden, MI 49945, USA.

ABSTRACT
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 (0.5 mL) is transferred to a disposable cuvette, containing 0.5 mL of reaction mixture [200 mM HEPES, pH 7.6, 20 mM MgCl2, with 80 nmol 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 10 min at field temperature. Absorbance of the completed reaction is measured at 360 nm 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 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app.

No MeSH data available.


Related in: MedlinePlus