Semi-automatic liquid chromatographic analysis of pamidronate in urine after derivatization with 1-naphthylisothiocyanate

An existing sensitive chromatographic assay for pamidronate in urine has considerably been automated. Using the same sample processor, the solid-phase extraction (SPE) was automated separately from the derivatization with 1-naphthylisothiocyanate, the two-fold ion-pair liquid-liquid-extraction and the treatment with hydrogen peroxide for the 2-20 ng/ml concentration range. The automatic procedure was preceded by a triple calcium precipitation and interrupted by evaporation of the SPE eluate under nitrogen. For the 0.5-5 microg/ml concentration range one automatic sequence was used by avoiding evaporation during the sample treatment. In addition to the labour-saving of the semi-automatic procedure, the daily sample-throughput was improved compared to the existing manual assay. Further, the validation showed marginal improvements in the precision, accuracy and lower limit of quantification.