A method for low-level determination of the 25-mono-hydroxy-metabolites of vitamin D2 and D3 in plasma has been developed by Spark Holland.
The assay is acetonitrile-free, avoiding problems associated with the current acetonitrile shortage.
Quantitation levels of around 1ng/mL are reported using the Symbiosis system for high-performance liquid chromatography (HPLC) with integrated solid phase extraction linked to an Applied Biosystems API 4000 mass spectrometer.
The assay involves almost no manual handling: plasma samples are diluted with a newly developed protein disrupting buffer, which also contains the internal standard.
Samples are then placed in the autosampler for direct injection into the SPE-LC-MS/MS system.
The method shows good linearity, precision and carryover and runs in only four minutes, including SPE.
Low levels of vitamin D have been associated with osteoporosis, diabetes, hypertension and cancer.
The acetonitrile-free vitamin D assay is therefore likely to be of benefit, in terms of speed, cost-effectiveness and convenience to clinical research laboratory environments.
The vitamin D assay is the latest example of the high assay quality and sensitivity achieved by dedicated on-line SPE-LC-MS/MS systems.
High-resolution SPE cartridges and precise SPE process control enable efficient sample preparation and concentration.
Combined with direct elution into LC-MS/MS systems, high assay performance is achieved as well as maximum assay automation.
