Determination of risedronate in human urine by column-switching ion-pair high-performance liquid chromatography with ultraviolet detection

• Published in: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences Analytical technologies in the biomedical and life sciences, 2003-08, Vol.794 (1), p.23-33
• Main Authors: Vallano, P.T, Shugarts, S.B, Kline, W.F, Woolf, E.J, Matuszewski, B.K
• Format: Article
• Language: English
• Subjects: Analysis; Biological and medical sciences; Chromatography, High Pressure Liquid - methods; Etidronic Acid - analogs & derivatives; Etidronic Acid - urine; General pharmacology; Humans; Ions; Medical sciences; Pharmacology. Drug treatments; Reference Standards; Reproducibility of Results; Risedronate; Risedronate Sodium; Sensitivity and Specificity; Spectrophotometry, Ultraviolet - methods
• ISSN: 1570-0232; 1873-376X
• DOI: 10.1016/S1570-0232(03)00394-5

An HPLC assay for the determination of risedronate in human urine was developed and validated. Risedronate and the internal standard were isolated from 5-ml urine samples in a two-part procedure. First, the analytes were precipitated from urine along with endogenous phosphates as calcium salts by the addition of CaCl 2 at alkaline pH. The precipitate was then dissolved in 0.05 M ethylene glycol-bis(β-aminoethyl ether)- N,N,N′,N′-tetraacetic acid and subjected to ion-pair solid-phase extraction using a Waters HLB cartridge (1 ml, 30 mg) with 1-octyltriethylammonium phosphate as the ion-pair reagent. Following extraction, the analytes were initially separated from the majority of co-extracted endogenous components on a Waters X-Terra RP18 (4.6×50 mm, 3.5 μm) column. The effluent from the X-Terra was “heart-cut” onto a Phenomenex Synergi Polar RP (4.6×150 mm, 4 μm) column for final separation. UV detection ( λ=262 nm) was used to quantitate risedronate in the concentration range of 7.5–250 ng/ml. Mean recovery was 83.3% for risedronate and 86.5% for the internal standard. The intra-day precision of the assay, as assessed by replicate ( n=5) standard curves, was better than 6% RSD for all points on the standard curve. Within-day accuracy for the standards ranged from 96.3 to 106.1% of nominal. Inter-day precision for quality controls assayed over a 3-week period was better than 5%, while inter-day accuracy was within 90% of nominal. The assay was employed to analyze samples collected during a clinical pharmacokinetics study.