Solid- and liquid-phase extraction for the gas chromatographic-tandem mass spectrometric quantification of 2,3-dinor-thromboxane B2 and 2,3-dinor-6-oxo-prostaglandin F1 alpha in human urine

Whole body synthesis of thromboxane A2 is best assessed by quantifying non-invasively its major urinary metabolite, i.e., 2,3-dinor-thromboxane B2 (2,3-dn-TxB2), by gas chromatography-mass spectrometry (GC-MS) or GC-tandem MS. Methods based on these techniques usually require a series of extraction and purification procedures including solid-phase extraction (SPE) and thin-layer chromatography (TLC) or liquid chromatographic separation of authentic or derivatized 2,3-dn-TxB2. Taking advantage of the inherent accuracy of GC-tandem MS and the high selectivity of the extraction of methoximated 2,3-dn-TxB2 on phenylboronic acid SPE cartridges we developed a method that involves only SPE steps prior to quantification by GC-tandem MS. The method was validated by performing in parallel an additional TLC step. Method mean accuracy and precision were of the order of 103% and 95%, respectively. The method allows furthermore co-processing of the same urine sample to quantify accurately and rapidly the major urinary metabolite of prostacyclin, i.e., 2,3-dn-6-oxo-prostaglandin (PG) F1 alpha, by GC-tandem MS. The limit of detection of the method was below each 5 pg of 2,3-dn-TxB2 and 2,3-dn-6-oxo-PGF1 alpha per 5 ml of urine. Our study suggests that dinor metabolites of isothromboxanes and isoprostacyclins are not abundantly present in human urine.