High turbulence liquid chromatography online extraction and tandem mass spectrometry for the simultaneous determination of suberoylanilide hydroxamic acid and its two metabolites in human serum

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Abstract
A reliable and sensitive method incorporating high turbulence liquid chromatography (HTLC) online extraction with tandem mass spectrometry (MS/MS), for simultaneous determination of suberoylanilide hydroxamic acid (SAHA) and its two metabolites, SAHA‐glucuronide (M1) and 4‐anilino‐4‐oxobutanoic acid (M2), in human serum, has been developed to support clinical studies. The HTLC technology significantly reduces the time required for sample clean‐up since sample extraction and analysis are performed online. Clinical samples, internal standards (IS) and buffer are transferred into 96‐well plates using a robotic liquid handling system. A 20 µL aliquot of prepared sample is directly injected into the HTLC/LC‐MS/MS system where the matrix is rapidly washed away to waste and the analytes are retained on the narrow‐bore extraction column (0.5 × 50 mm), using an aqueous mobile phase at 1.5 mL/min. Analytes are then eluted from the extraction column and transferred to the analytical column using a gradient mobile phase prior to detection by MS/MS. Interference with determination of SAHA from in‐source dissociation of M1 is eliminated by the chromatographic separation. The resolution of SAHA and M1 did not change for more than 1500 serum sample injections by applying an acid wash (15% acetic acid) on the extraction column. The linear calibration ranges for SAHA, M1, and M2 are 2–500, 5–2000, and 10–2000 ng/mL, respectively. Assay intraday validation was conducted using five calibration curves prepared in five lots of human control serum. The precision expressed as relative standard deviation (RSD) is less than 6.8% and accuracy is 94.6–102.9% of nominal values for all three analytes. Assay specificity, freeze/thaw stability, storage stability, and matrix effects were also assessed. Copyright © 2005 John Wiley & Sons, Ltd.