Malachite Green Method for Determining Phosphorus Concentration in Diverse Matrices

Sequential phosphorus (P) fractionation is a procedure often used to assess P dynamics in riparian soils and stream sediments. The most commonly used method to quantify P in fractionation extracts is the molybdate blue-ascorbic acid (MB-AA) colorimetric method. Because sequential P fractionation gen...

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Bibliographic Details
Published in:Communications in Soil Science and Plant Analysis 2019-08, Vol.50 (14), p.1743-1752
Main Authors: Rahutomo, Suroso, Kovar, John L., Thompson, Michael L.
Format: Article
Language:English
Subjects:
Analytical methods
Ascorbic acid
Bicarbonates
Colorimetry
Fractionation
Hydrochloric acid
Hydroxides
Laboratory equipment
Malachite green
malachite green colorimetric method
Molybdate
molybdate blue-ascorbic acid colorimetric method
Phosphorus
Phosphorus fractionation
Sediment
Sediments
sequential extraction
Sodium
Sodium bicarbonate
Sodium hydroxide
Soil
Soil dynamics
Sulfuric acid
Sulphuric acid
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Summary:Sequential phosphorus (P) fractionation is a procedure often used to assess P dynamics in riparian soils and stream sediments. The most commonly used method to quantify P in fractionation extracts is the molybdate blue-ascorbic acid (MB-AA) colorimetric method. Because sequential P fractionation generates a large number of samples, it would be advantageous to use a single, rapid analytical technique to determine P concentrations. Thus, we investigated the malachite green (MG) colorimetric method for determining P concentrations in the diverse sequential fractionation matrices. For the MG method, a 96-well standard microplate was used, and absorbance was read on a universal microplate reader. We found that the MG and MB-AA methods agreed for determining P concentration in extracts of water, 1 M hydrochloric acid (HCl), and concentrated sulfuric acid (H 2 SO 4 ). Small differences between the two methods were found for extracts of 0.5 M sodium bicarbonate (NaHCO 3 ) and 0.1 M sodium hydroxide (NaOH), and concentrated HCl, most likely related to differing characteristics of the sediments that were analyzed. Despite this discrepancy for some extracts in the sequential extraction, the microplate system-MG method can be valuable because of its simplicity, sensitivity, and rapidity compared to the MB-AA method.
ISSN:0010-3624
1532-2416
1532-4133
DOI:10.1080/00103624.2019.1635140