Shielded Hydrophobic Phase for Direct Sample Analysis: Preliminary Study for the Analysis of Phenobarbital for Potential Neonatal and Pediatric Drug Monitoring

Abstract

Shielded Hydrophobic Phase(SHP) for Direct Sample Analysis of phenobarbital in serum was investigated for Therapeutic Drug Monitoring by studying the column stability and utilization parameters, and by comparison to the established fluorescence polarization immunoassays. This novel packing consisted of 5 um spherical silica particles with 100 Å pores, bonded with polar and non-polar functionalities to the inside and outside of the particles. Proteins may be eluted, unretained with solvent front peaks while the drug/metabolites would undergo hydrophobic interaction, eluting later. For Direct Sample Analysis of phenobarbital in serum, 10 uL aliquots, after centrifuged at 9,500 × g for 20 minutes, were injected into the SHP guard column and column, and eluted with phosphate/ACN(9:1). Phenobarbital eluted with k′ of 3.4 at 3.8 minutes. Calibration was linear between 5 to 80 mg/L. Precision studies showed acceptable within-run and day-to-day coefficients of variation. Comparison with FPIA showed acceptable correlation. This preliminary study showed that SHP may be used for Direct Sample Analysis of phenobarbital. The simplicity of the procedure, and the small sample size may be advantageously applied for neonatal and pediatric drug monitoring. Further study will be needed to evaluate its long term stability, and applications to the monitoring of other drug groups.