BACKGROUND: Liquid chromatography tandem-mass spectrometer (LC-MS/MS) techniques are more and more common in the measurement of testosterone concentrations in biological samples. However, LC-MS/MS methods are more laborious than streamlined automated immunochemistry methods because of the need for tedious pre-purification of the sample before the mass spectrometric analysis. We therefore developed a robust and rapid sample clean-up method to improve the throughput of the whole LC-MS/MS analysis procedure by applying an automated on-line solid-phase extraction (SPE) technique instead of the still widely used conventional liquid-liquid extraction. METHODS: Testosterone was purified by the on-line SPE-column-switching technique after rapid precipitation of serum samples by zinc sulphate/internal standard solution before LC-MS/MS analysis. The results were compared with those of our previous routine LC-MS/MS method using liquid-liquid extraction with tert-butyl methyl ether for the pre-purification of the samples. RESULTS: The tested on-line SPE-LC-MS/MS method reached the specifications of the previous method with liquid-liquid extraction. The precision of the new method was notably better, especially in the lower concentration range, than with the former method; the total variation was below 10% in the whole quantitation range of 0.25-35 nmol/L. The new method liberates more than 50% of hands-on time of laboratory technicians as well as expensive instrument time for other applications compared with the older method. CONCLUSIONS: The on-line SPE-pre-purification technique tested in long-term use offers a rapid and reliable technique in the LC-MS/MS analysis of serum testosterone and is a valuable tool in the improvement of efficiency in the laborious steroid analytics.
BACKGROUND: Liquid chromatography tandem-mass spectrometer (LC-MS/MS) techniques are more and more common in the measurement of testosterone concentrations in biological samples. However, LC-MS/MS methods are more laborious than streamlined automated immunochemistry methods because of the need for tedious pre-purification of the sample before the mass spectrometric analysis. We therefore developed a robust and rapid sample clean-up method to improve the throughput of the whole LC-MS/MS analysis procedure by applying an automated on-line solid-phase extraction (SPE) technique instead of the still widely used conventional liquid-liquid extraction. METHODS:Testosterone was purified by the on-line SPE-column-switching technique after rapid precipitation of serum samples by zinc sulphate/internal standard solution before LC-MS/MS analysis. The results were compared with those of our previous routine LC-MS/MS method using liquid-liquid extraction with tert-butyl methyl ether for the pre-purification of the samples. RESULTS: The tested on-line SPE-LC-MS/MS method reached the specifications of the previous method with liquid-liquid extraction. The precision of the new method was notably better, especially in the lower concentration range, than with the former method; the total variation was below 10% in the whole quantitation range of 0.25-35 nmol/L. The new method liberates more than 50% of hands-on time of laboratory technicians as well as expensive instrument time for other applications compared with the older method. CONCLUSIONS: The on-line SPE-pre-purification technique tested in long-term use offers a rapid and reliable technique in the LC-MS/MS analysis of serum testosterone and is a valuable tool in the improvement of efficiency in the laborious steroid analytics.