Analysis of bisphosphonates by capillary electrophoresis–electrospray ionization mass spectrometry

Capillary electrophoresis–electrospray ionization mass spectrometry (CE–ESI-MS) was applied to the direct identification and quantitation of clodronate and its four common impurities. The coaxial interface technique and negative ion mode were used in the detection. Ion source parameters and sheath liquid composition were optimized to produce maximum abundance of singly charged deprotonated molecules used in monitoring. In addition, the effects of electrolyte composition and instrumental parameters of CE on separation were studied. The developed method provides high separation power and specificity to bisphosphonate analysis. In quantitative analysis, the method showed good linearity (r=0.9946–0.9989), satisfactory repeatability (migration time variation: RSD=0.43–1.0%, peak area variation: RSD=2.2–9.4%) and sufficient sensitivity (detection limits: 0.08–0.22 mg ml−1) for identification of bisphosphonates from bulk material.