Instrument-Specific Matrix Effects of Calibration Materials in the LC-MS/MS Analysis of Tacrolimus
2008; American Association for Clinical Chemistry; Volume: 54; Issue: 8 Linguagem: Inglês
10.1373/clinchem.2008.105643
ISSN1530-8561
Autores Tópico(s)Antibiotics Pharmacokinetics and Efficacy
ResumoLC-MS/MS can enable analyses on a reference method level in a routine laboratory, if stable isotope dilution internal standardization is applicable for an analyte. For many analytes, however, stable isotope-labeled internal standards are not available, and homologous compounds with a similar molecular structure must be used as an internal standard. The use of such homologs introduces a source of inaccuracy, because ion suppression (1)(2) and ion enhancement effects can have different impacts on the target analyte and the internal standard compound, respectively. This important pitfall of non-isotope dilution LC-MS/MS methods is illustrated by an observation we made in the context of monitoring the drug tacrolimus. We have used 2 LC-MS/MS instruments for the quantification of tacrolimus, a Waters Quattro Ultima (instrument 1, installed 2003) and a Waters Micro (instrument 2, installed 2006). Similar methods were used on both systems, employing protein precipitation followed by on-line solid-phase extraction for sample preparation, as described …
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