Assay of 1-hydroxy-3-aminopropylidene-1,1-bisphosphonate and related bisphosphonates in human urine and plasma by high-performance ion chromatography.

A method is described for the analysis of 1-hydroxy-3-aminopropylidene-1, 1-bisphosphonate and related bisphosphonates in human urine and plasma. Samples are spiked with 1-hydroxy-5-aminopentylidene-1,1-bisphosphonate as an internal standard and calcium chloride is added to precipitate the bisphosphonates. Following centrifugation the precipitate is redissolved in acetic acid, and the bisphosphonates are separated by high-performance ion chromatography on a Dionex AS7 column using nitric acid as mobile phase. The bisphosphonates are oxidised to orthophosphate using post-column addition of ammonium persulphate and this is followed by post-column reaction with molybdenum-ascorbate to yield the phosphomolybdate chromophore which is detected at 820 nm. A detection limit of 10 ng/ml is possible.