Selective and sensitive determination of pamidronate in human plasma and urine by gas chromatography with flame photometric detection.

A rapid, selective and sensitive method for the determination of pamidronate in human plasma and urine samples by gas chromatography (GC) has been developed. After deproteinization of the sample with trichloroacetic acid, pamidronate was converted into its N-isobutoxycarbonyl methyl ester derivative and measured by GC with flame photometric detection (FPD), using a HP-1 capillary column. The derivative preparation and GC analysis were accomplished within 30 min. The derivative was sufficiently volatile and stable, giving a single and symmetrical peak, and provided an excellent FPD response. The detection limit of pamidronate, at a signal-to-noise ratio of 3, was ca. 100 pg injected, and the calibration curve for this compound in the range 20-1000 ng was linear and sufficiently reproducible for quantitative determination. This method could be successfully applied to plasma and urine samples without a preliminary clean-up except for deproteinization with trichloroacetic acid, and pamidronate could be measured without any influence from coexisting substances. Overall recoveries of pamidronate added to plasma and urine samples were 93-97%. The coefficients of variation for intra-assay and inter-assay of pamidronate in these samples were 1.0-7.9% (n = 3) and 4.1-8.3% (n = 6), respectively.