Internal-surface reversed-phase silica support for direct-injection determination of drugs in biological fluids by liquid chromatography

Abstract

A new internal-surface reversed-phase (ISRP) silica support has been designed for direct injection analysis of drugs in biological fluids by liquid chromatography. The support, prepared by using a new enzyme, polymyxin acylase, has N-octanoylaminopropyl phases, bound only to the internal surfaces of the porous silica, and N-(2,3-dihydroxypropyl)-aminopropyl phases on the external surfaces in order to be nonadsorptive to proteins. The average pore diameter of the prepared ISRP silica support was 50 A, which is small enough to exclude macromolecules such as serum proteins from the pores. The new ISRP support can be used for the direct injection analysis of hydrophilic and hydrophobic drugs in serum or plasma without destructive accumulation of proteins over the eluent pH range of 3 to 7. The recovery of drugs from serum was almost 100%, regardless of the difference in their protein bindings.

Bulk derivatization and cation exchange restricted access media-based trap-and-elute liquid chromatography–mass spectrometry method for determination of trace estrogens in serum

“…In this study, a WCX RAM trap column and on-line dilution channel were used as an automated on-line trap-and-elute pre-treatment process. The dilution channel (1:8 dilution) was positioned right after sample injection and served to weaken ionic interaction or hydrophobic bonding between proteins and estrogens, thereby improving trapping efficiency and target compound recovery in the trap prior to switching of the flow to the separation column [36][37][38][39]. It was demonstrated in our study that WCX RAM trap column along with dilution channel could effectively trap target estrogen derivatives and remove proteins and other biological matrices, and enable detection of parts-per-trillion level of trace estrogens on LC-MS/MS in only 100 mL of serum sample.…”

Methylcellulose-immobilized Reversed-phase Precolumn for Direct Analysis of Drugs in Plasma by HPLC

“…The internal surface reversed phase (ISRP) invented by Pinkerton and Hagestam 1-3 set a benchmark for performance of RAM columns, and an improved ISRP column bed was later developed by Haginaka. 4 Other types of ISRP columns, several alkyl/diol silica (ADS), [5][6][7][8] dual zone 9 and mixed functional phase (MFP) types 10,11 had been developed. As a protein-immobilized stationary phase capable of plasma direct injection, octadecylsilane (ODS) treated with human plasma was developed and plasma direct injection capability was shown by Yoshida et al 12,13 α1-Acidglycoprotein (α1-AGP)-, ovomucoid-and avidin-coated columns had been developed, [14][15][16] and are capable of plasma direct injection.…”

Mobile phase versus stationary phase approaches to the direct injection of biological fluids in liquid chromatography

“…Low to zero elution of serum proteins from the PinkertonTM column ha5 been reported for mobile phases having pH's ranging from 2.6 to 4.2. (Haginaka et al, 1989). These workers suggest that this is due to electrostatic attractions between proteins having a net positive charge and the glycine residues on the external surface of the support which will have a negative charge at acidic pH's.…”

“…The internal surface of the Pinkerton' ISRP support is bound with a hydrophobic tripeptide, while the external surface is bound with a hydrophilic glycerylpropyl phase. The shielded hydrophobic phase (HisepTM) developed by Supelco, Inc. (Hunter et al, 1988;Gisch ez aL, 1988) and the recently reported Noctanoylaminopropyl ISRP silica support (Haginaka et al, 1989) are other stationary phases which have been specifically designed for the direct injection of biological fluids.…”

“…The separation of drugs from urine and cerebrospinal fluid have been reported employing the PinkertonTM support (Pinkerton, 1988). The Hisep' column (Wong et al, 1988) and t h e Haginaka ISRP column (Haginaka et al, 1989) have been utilized f o r t h e analysis of drugs in serum.…”