Ion suppression and cannulation locking solutions

Ion suppression is a common concern when utilizing liquid chromatography-tandem mass spectrometry for quantitation of analytes in biological samples. Ion suppression can cause the analytical signal for the analyte and/or the internal standard to be reduced compared with prepared analytical standards, leading to erroneous quantitation values for the desired analyte of interest. While it has become commonplace to note ion suppression due to the dosing vehicle in in vivo experiments, we have observed a similar phenomenon of ion suppression due to the components of the locking solution used to keep the cannula patent in certain rodent experiments. During one such typical bioanalysis of a drug candidate dosed to a cannulated rodent, significant ion suppression (∼60%) was observed for the structural analogue internal standard, which led to this investigation that revealed the cannula locking solution as the source of the ion suppression.