BACKGROUND: Therapeutic drug monitoring (TDM) of antidepressants is important to ensure compliance and to rule out pharmacokinetic abnormalities. Therefore, reliable methods for quantification are important for clinical laboratories. Most of the currently used mass spectrometry methods use triple quadrupoles as mass analyzers. We aimed to develop a method using high-resolution mass spectrometry (HRMS) and wanted to test the suitability of this analyzer for quantitative TDM assays. This would be beneficial since HRMS instruments can also be used for metabolomics and protein analysis and, thus, many different analyses could be run on one instrument. METHODS: After manual protein precipitation of serum samples, further sample clean-up was achieved using a Turbo Flow column preconnected to the analytical LC column. Stable isotope-labelled counterparts of the target analytes were used as internal standards. For detection, we used a Q Exactive Focus Orbitrap mass spectrometer operating in full-scan mode. Ionization was performed in positive ESI. RESULTS: Accuracy, recovery, and matrix effect were acceptable for all analytes. The method demonstrated outstanding precision (within-run imprecision <4.5%, between-run imprecision <7.5%). The selectivity of the method was ensured by chromatographic separation of all isobaric compounds. Close agreement between Orbitrap and triple stage based quantification was observed in a comparison measurement of leftover patient samples. CONCLUSIONS: We have established a selective method for the quantification of antidepressants with outstanding precision using a high-resolution Orbitrap mass spectrometer. The applicability of HRMS instruments to TDM was demonstrated.
BACKGROUND: Therapeutic drug monitoring (TDM) of antidepressants is important to ensure compliance and to rule out pharmacokinetic abnormalities. Therefore, reliable methods for quantification are important for clinical laboratories. Most of the currently used mass spectrometry methods use triple quadrupoles as mass analyzers. We aimed to develop a method using high-resolution mass spectrometry (HRMS) and wanted to test the suitability of this analyzer for quantitative TDM assays. This would be beneficial since HRMS instruments can also be used for metabolomics and protein analysis and, thus, many different analyses could be run on one instrument. METHODS: After manual protein precipitation of serum samples, further sample clean-up was achieved using a Turbo Flow column preconnected to the analytical LC column. Stable isotope-labelled counterparts of the target analytes were used as internal standards. For detection, we used a Q Exactive Focus Orbitrap mass spectrometer operating in full-scan mode. Ionization was performed in positive ESI. RESULTS: Accuracy, recovery, and matrix effect were acceptable for all analytes. The method demonstrated outstanding precision (within-run imprecision <4.5%, between-run imprecision <7.5%). The selectivity of the method was ensured by chromatographic separation of all isobaric compounds. Close agreement between Orbitrap and triple stage based quantification was observed in a comparison measurement of leftover patient samples. CONCLUSIONS: We have established a selective method for the quantification of antidepressants with outstanding precision using a high-resolution Orbitrap mass spectrometer. The applicability of HRMS instruments to TDM was demonstrated.
Keywords:
Antidepressants; CV, coefficient of variation; EMA, European Medicines Agency; ESI, electrospray ionization; HRMS, high-resolution mass spectrometry; High-resolution mass spectrometry; ISTD, internal standard; LC-MS/MS, liquid chromatography tandem mass spectrometry; LLOD, lower limit of detection; LLOQ, lower limit of quantification; MS, mass spectrometry; QC, quality control sample; TDM, therapeutic drug monitoring; Therapeutic drug monitoring (TDM); TurboFlow technology; UHPLC, ultra high-performance liquid chromatography
Authors: Qizhi Hu; Robert J Noll; Hongyan Li; Alexander Makarov; Mark Hardman; R Graham Cooks Journal: J Mass Spectrom Date: 2005-04 Impact factor: 1.982
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