elution buffers described herein can be supplied by any calcium salt that is soluble in the elution buffer which is typically an aqueous solution and that is inert to the other components of the elution buffer the hydroxyapatite resin and the proteins retained on the resin and in many cases also the remaining components of the source solution from which the proteins are sought to be extracted calcium halide salts are convenient to use and calcium chloride is particularly convenient in certain embodiments of the concept herein best results will be achieved with a calcium ion concentration in the elution buffer of from about 25 ppm to about 260 ppm an alternate range is about 40 ppm to about 200 ppm and a further alternate range is about 50 ppm to about 150 ppm phosphate ion for inclusion in the elution buffers can likewise be supplied from any phosphate salt that is soluble in the elution buffer which is again typically aqueous and that is inert to the other components of the buffer the resin the proteins and the remaining components of the source solution alkali metal or alkaline earth metal phosphates are convenient with sodium phosphate as an example in certain embodiments of the concept herein best results will be achieved with a phosphate.