Is it possible to elute plasmid DNA from the QIAprep Spin Miniprep columns with buffer containing Potassium Phosphate?
FAQ ID -854

Unfortunately, we do not have any compatibility data for using potassium phosphate-based buffers instead of TE or water for the elution of plasmid DNA from the spin columns of the QIAprep Spin Miniprep Kit.

However, below is a reference where cDNA was eluted from QIAquick PCR Purification Kit columns with potassium phosphate buffer (4 mM, pH 8.5), after replacing the wash buffer (PE) with 5 mM potassium phosphate (pH 8.5) containing 80% ethanol:

Wang HY, Malek RL, Kwitek AE, Greene AS, Luu TV, Behbahani B, Frank B, Quackenbush J, Lee NH. "Assessing unmodified 70-mer oligonucleotide probe performance on glass-slide microarrays." Genome Biol. 2003, 4(1): R5. Epub 2003 Jan 6.