Accurate Pain Management Analysis in Under 5 Min on Raptor Biphenyl Superficially Porous Particle LC Columns

Jun 01, 2014

Pain management LC analyses can be difficult to optimize due to the limited selectivity of C18 and phenyl-hexyl phases. In contrast, the selectivity of Raptor Biphenyl superficially porous particle (SPP) LC columns provides complete resolution of isobaric pain medications with a total cycle time of 5 min.

Accurate, reliable analysis of pain medications is a key component in monitoring appropriate medical use and preventing drug diversion and abuse. As the demand for fast, multicomponent methods grows, LC–MS-MS methods are increasingly desired for pain management and therapeutic drug monitoring due to the low detection limits that can be achieved with this highly sensitive and selective technique. However, despite the selectivity offered by mass spectrometry, hydrophilic matrix components can still interfere with early-eluting drug compounds resulting in ion suppression. In addition, isobaric pairs must be chromatographically separated for positive identification. The need for highly selective and accurate methods makes LC column selection critical.

Table I: Mobile phase gradient
While C18 and phenyl-hexyl phases are frequently used for bioanalytical LC–MS-MS applications, Restek's Biphenyl phase offers better aromatic retention and selectivity for pharmaceutical and drug-like compounds, giving it a significant advantage over other phases for the analysis of pain management medications or other drugs of abuse. The Biphenyl phase, originally developed a decade ago by Restek, has recently been combined with Raptor™ SPP ("core-shell") silica particles to allow for faster separations without the need for expensive UHPLC instrumentation. Here, we demonstrate the fast, selective separation of commonly tested pain drugs that can be achieved using the new Raptor™ SPP Biphenyl LC column.

Experimental Conditions

A standard containing multiple pain management drugs was prepared in blank human urine and diluted with mobile phase as follows, urine:mobile phase A:mobile phase B (17:76:7). The final concentration for all analytes was 10 ng/mL except for lorazepam, which was 100 ng/mL. Samples were then analyzed by LC–MS-MS using an AB SCIEX API 4000™ MS-MS in ESI+ mode. Chromatographic conditions, retention times, and mass transitions are presented here and in Tables I and II:

Column: Raptor™ Biphenyl, 50 mm × 3.0 mm i.d. × 2.7 µm
Sample: Fortified urine
Inj. vol.: 10 µL
Inj. temp.: 30 °C
Mobile phase A: Water + 0.1% formic acid
Mobile phase B: Methanol + 0.1% formic acid