Characterization of an Amphetamine Interference from Gabapentin in an LC-HRMS Method.

An amphetamine interference was observed during the development of an liquid chromatography-high-resolution mass spectrometry (LC-HRMS) multi-class confirmation method for the determination of 47 drugs and metabolites in urine. The interference passed all qualitative criteria for amphetamine leading to potential false-positive results. Upon investigation, it was found that the amphetamine interference was correlated with the presence of high levels of gabapentin.

Identification of Novel Opioid Interferences using High-Resolution Mass Spectrometry.

Novel opioid interferences were observed during the development of a high-resolution liquid chromatography-mass spectrometry urine drug testing method for 47 analytes from multiple drug classes. The interferences affected both analytes and internal standards and were only observed when the method was challenged with patient samples. Some interferences were attributable to isomeric opioid metabolites not previously reported while others were due to interference from in-source dissociations or 13C isotopic contributions from known opioid metabolites not typically monitored as analytes.