Quantitative determination of ethane-1-hydroxy-1,1-diphosphonate in urine and plasma

A technique has been developed to measure the diphosphonate ethane-1-hydroxy-1, 1-diphosphonate (EHDP) quantitatively in 5 ml of urine or 2 ml of plasma. The procedure is based on a coprecipitation of EHDP with calcium phosphate, elimination of inorganic phosphate as an insoluble triethylamine-phosphomolybdate complex, decomposition of the P-C-P bond with ultraviolet light and spectrophotometric determination of the inorganic phosphate released. A trace amount of [14C] EHDP is used to correct for losses. The method appears specific for the diphosphonate, exhibits quantitative recoveries, and has a mean coefficient of variation of 3.7% for urine and 7.3% for plasma. The limit of detection is in the order of 2.5 mumol/1 in 5 ml urine and 0.5 mumol/1 in 2 ml of plasma.