Signal suppression/enhancement in HPLC‐ESI‐MS/MS from concomitant medications

Abstract

This paper presents a study of the signal suppression and enhancement effects in assays based on HPLC-ESI-MS/MS detection. The major focus was to investigate the effect of signal suppression/enhancement of typical co-administered (concomitant) medications, i.e. naproxen and ibuprofen. The results demonstrate that the analyte and internal standard can experience signal enhancement up to a factor of ca 2.9 if the test analyte or internal standard co-elute with concomitant. Experimental results also demonstrate that the analyte and internal standard signal increased by a factor of ca 2.0 in the negative ion mode at physiological relevant levels of naproxen (100 microg/mL) and by a factor of ca 1.6 in the negative ion mode at physiological relevant level of ibuprofen (10 microg/mL) in both neat and plasma samples. Signal enhancement significantly increased when concomitant medications ionized in the same ion mode as the analyte and internal standard. To overcome signal enhancement or potential suppression from concomitant medications, a comprehensive HPLC method needs to be developed with sufficient separation of concomitant medication from the analyte and internal standard. Other means to reduce signal enhancement or potential suppression include switching ionization polarity and performing comprehensive sample clean-up to remove concomitant medications before analysis.

A Validated Enantioselective Assay for the Determination of Ibuprofen in Human Plasma Using Ultra Performance Liquid Chromatography with Tandem Mass Spectrometry (UPLC-MS/MS)

“…The indirect methods have improved sensitivity and are better suited for the analysis of ibuprofen enantiomers in a variety of complex biological matrices. The indirect techniques include HPLC using UV [26,27], fluorescence [28,29], and mass spectrometric detection [30][31][32][33]. Gas chromatography-mass spectrometry (GC/ MS) methods have been reported as well [2,6,[34][35][36].…”

“…GC/MS methods can be stereoselective, but they use a larger sample size for analysis (i.e., 0.8 mL plasma or 1 mL of serum) [34,6], and their sensitivity is insufficient (i.e., 0.25 µg/mL or LOQ 5 µg/mL) [34,35], or they are not stereoselective [35,36]. Several indirect HPLC/ MS/MS methods were reported for various in vitro [30][31][32] and in vivo [33] analyses of ibuprofen, but these methods are not stereoselective and do not represent significant improvement in comparison to the methodologies reported above.…”

Methodology of internal standard selection. Comment on the work of Wang and co‐workers: simultaneous determination of dipyridamole and salicylic acid in human plasma by high‐performance liquid chromatograph‐mass spectrometry

“…These data would provide an easy access for analysts to probe and select suitable internal standards if they have the situation of two compounds that need positive and negative ionization modes for detection akin to simultaneous quantification of dipyrimadole and salicylic acid. Such data availability would attain high importance, in light of the well-documented signal suppression/enhancement occurring in electrospray ionization tandem mass spectrometry (Leverence et al, 2007) from concomitant medications. Overall, the internal standard selection may pose significant challenges in polypharmacy situations and therefore reporting of such information by Wang et al (2008) may benefit the scientific community as a whole.…”

Dodging matrix effects in liquid chromatography tandem mass spectrometric assays—compilation of key learnings and perspectives

“…Leverence et al (2007) have succinctly described the influence of over the counter drugs such as ibuprofen and naproxen that may be present in clinical samples when other analytes of importance are being assayed. While establishing and documenting the definite matrix effect issues at therapeutically relevant concentrations of both ibuprofen and naproxen, the authors have proposed a step-wise strategy to overcome the matrix effects (Leverence et al, 2007). Firstly, the setting of gradients in chromatographic separation scheme would help in the physical separation of peaks and therefore would provide a cleaner ion channel for the compound of interest from co-medications.…”

“…Secondly, switching of polarity of the ionization interface is appropriate if the compound of interest can ionize regardless of the polarity, while the interfering co-medication can only ionize in a single mode. Thirdly, formulating a cleaner extraction strategy such as solid-phase extraction and diligently choosing the solvent(s) to get rid of the interfering species as completely as possible are necessary prior to mass spectrometric assays (Leverence et al, 2007).…”