Aluminum toxicity can occur in acidic soils (pH &lt; 5.5) and affects an estimated 35% of arable land in North America and up to 50% of arable land worldwide.  These soils are largely unusable for a variety of crops, limiting food access and stability.  There are two primary mechanisms plants can use to grow in Al toxic soils.  One mechanism is Al tolerance, where Al is internalized but sequestered in a manner that limits the damaging effects of Al to the plant. A second mechanism is Al exclusion, where Al is excluded from the roots by release of chelators.  Al exclusion is seemingly the preferred mechanism since prevention of uptake would eliminate the likelihood of any damage related to internalization.  Organic acids, such as those containing di- and tri- carboxylic acids, are examples of chelators that can be released into the soil to prevent the uptake of Al by the roots.  However, measuring these organic acids are in soil are not trivial; in addition to Al, there are also other common metals present that can be chelated and act as interferants.   This work explores the use of weak-anion exchange solid-phase extraction to isolate and Nuclear Magnetic Resonance and Gas-Chromatography coupled with Mass Spectrometry to quantify the production of organic acids exuded from the roots for an Al-protective mechanism.  A variety of methods are being evaluated, including the recovery of organic acids in the presence of calcium as a potential interferent and the use of EDTA to limit the interference of calcium or other metals may have on the recovery of organic acids by WAX-SPE.  Preliminary work suggests that chelation of calcium by the organic acids can have a significant effect on the recovery of organic acids by SPE and use of a buffer and EDTA can limit the interferents and increase recovery for some organic acids, but not all.  We are continuing to evaluate other modifications for SPE to broadly improve the recovery and reproducibility of organic acids exuded by plant roots using WAX-SPE.

Improving the extraction and recovery of organic acids from root exudates by WAX-SPE

ACS Spring 2022

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