Evaluation of matrix effects using a spike recovery approach in a dilute-and-inject liquid chromatography–tandem mass spectrometry opioid monitoring assay

• Isotope-labeled internal standards (IS) are not available for all LC-MS/MS analytes
• We compare stable isotope-labeled IS with analog IS in > 2000 clinical urine samples
• The recovery of a standard addition was used as a gold standard
• Using analog internal standards results in a false negative rate of up to 1.5 %
• Spike-recovery has no value for analytes with conventional internal standards

BackgroundLiquid chromatography–tandem mass spectrometry has become the gold standard for quantitative analysis of compounds in human matrices. Introduction of these assays into clinical practice, where false positive and false negative results have substantial implications, requires careful attention to matrix effects. We describe an evaluation of matrix effects in human urine from a dilute-and-inject liquid chromatography–tandem mass spectrometric assay for the quantitative analysis of opioids and metabolites.MethodsA spike-recovery approach was employed for each analyte in each sample. We examined the impact of spike-recovery for the 6 glucuronides measured in this assay and compared the analytes for which conventional stable isotope-labeled internal standards were used with the analytes for which analog internal standards were used.ResultsFor analytes that had analog internal standards, up to 1.5% of negative samples failed our requirement of recovering at least 80% of the expected spiked concentration while passing all other quality control parameters.ConclusionsUsing spike-recovery as a quality control parameter decreases the rate of false negatives for compounds using analog internal standards, but does not have benefit for compounds with conventional stable isotope-labeled internal standards.