Separating vitamin D metabolite stereoisomers

ultraFAIMS-MS for high throughput separation and quantification of Vitamin D metabolite stereoisomers

Vitamin D, along with calcium, promotes bone growth in children and aids in the prevention of osteoporosis in older adults. Simultaneous and accurate measurements of circulating vitamin D metabolites are critical to studies of the metabolic regulation of vitamin D and its impact on health and disease. Accurate quantification is also vital for routine diagnostic assessment of vitamin D related diseases.

However, occurrence of the biologically inactive 3-epi analog of 25-OH D_­3 (3-epi-25-OH D₃) has been reported; interference from this inactive 3-epi stereoisomer during measurement of vitamin D may lead to inaccurate information used for treatment and prevention of hypovitaminosis D.

Combining Ultra Field Asymmetric Ion Mobility Spectrometry (ultraFAIMS) with mass spectrometry (MS) and ionic modifiers enables quantification of Vitamin D metabolite 25-hydroxy D3 by removing isomeric interference from epimer 3-epi-25-hydroxy D3, avoiding a lengthy liquid chromatography separation step.

The ultraFAIMS microchip, which acts as a filter for specific ions, is composed of an array of parallel channels across which an asymmetric dispersion field (DF) is applied. Selected ions are transmitted through the chip by application of an appropriate compensation field (CF). In this case, separation was further optimised using an ionic modifier (rubidium acetate).

The miniaturised ultraFAIMS system provides separation of the vitamin D metabolite stereoisomers at timescales suitable for rapid sample introduction enabling high-throughput Vitamin D analysis in clinical settings.

This work is described in International Patent application publication number WO 2015/185487 A1; Kobold, U.; Thiele, R.; Weiss, N.; Brown, L.J.; Method and device for separating metabolites or stereoisomers by ion mobility spectrometry.

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