Development of a liquid chromatography–tandem mass spectrometry method to address the increased utilization of umbilical cord in the assessment of in utero drug exposure

Abstract

ObjectivesThe method described supports the detection of drugs and drug metabolites in the assessment of in utero drug exposure. The presented method employs liquid chromatography–tandem mass spectrometry (LC–MS/MS) as an alternative to a previously validated method using liquid chromatography-time-of-flight mass spectrometry (LC-TOF/MS). A reduction in required chromatographic time and consolidation from two injections to one injection per sample was desired to reduce turnaround time while maintaining the high specificity required. Design and methodsHomogenized and extracted umbilical cord samples were analyzed using LC-TOF/MS and LC–MS/MS. The LC–MS/MS chromatographic method used a 3.5min gradient with an injection-to-injection time of 5min. Dynamic multiple reaction monitoring was utilized. ResultsA 55% reduction in total analytical time was achieved by incorporating positive and negative mode acquisition in a single injection with the LC–MS/MS (5min cycle time) compared to the LC-TOF/MS method that required two total injections (one for positive mode, one for negative mode) and a combined ~11.5min cycle time. 514 patient samples were analyzed by both methods over 20 days. Of the 260 LC-TOF/MS negative samples, 259 were LC–MS/MS negative. Inter-assay imprecision conducted over 20days using the 50% and 150% QC samples yielded $_amp_$gt;97% qualitative acceptance and an average percent deviation from the target of 12% and 21%, respectively, using a single point calibration strategy. ConclusionsIn comparison to the existing LC-TOF/MS method, the LC–MS/MS method delivered the required specificity in a single injection with a 55% reduction in instrument time. Use of a single-point calibration standard and eight representative internal standards provided adequate accuracy for the quantitative assessment of quality control results with qualitative reporting of patient results.