Analysis of drugs in the presence of serum albumin by liquid chromatography with eluents containing surfactants

Abstract

Surfactant-containing eluents are evaluated for possible application to direct serum injection using conventional reverse-phase columns. Serum albumin was quantitatively eluted at the column void volume by using surfactant concentrations below or above the critical micelle concentration, and organic solvents could be used in proportions as high as 40% (w/w). Surfactant choice, pH, and salt effects were also evaluated.

Automated HPLC analyses of drugs of abuse via direct injection of biological fluids followed by simultaneous solid‐phase extraction and derivatization with fluorescence detection

“…This was, in part, based on the successes of others (Grohs et al, 1991). However, even with electrophoresis grade SDS at a concentration of 1 mM, fluorescent peaks were seen at trace levels.…”

“…To prevent the protein precipitation during sample handling, the serum was diluted 1:l with 1 2 0 x 1~ SDS containing 1 0 0 m~ NaOH. Compared to analyses in urine, the inorganic base was changed to NaOH because KOH caused the precipitation of SDS, a phenomenon others have seen (Grohs et al, 1991). This amount of SDS and NaOH allowed the sample to be stored at room temperature for morc than three weeks without the precipitation of serum proteins.…”

“…Micellar solubilization (Grohs et al, 1991; and restricted access media (RAM) (Unger, 1991) have allowed the analyst to inject the diluted biological fluid directly into the HPLC. The analyst has the choice of mobile phase or stationary phase approaches to analysis of drugs in biological fluids .…”

Influence of mobile phase conditions on the clean-up effect of restricted-access media precolumns for plasma samples injected in a column-switching system

“…The major advantages of such systems over other direct injection techniques, e.g. single column LC mode, such as the use of RAM columns or applying micellar [12] or surfactant [13,14] eluents for conventional reversed-phase columns, is its reconcentration ability, low detection limit and flexibility in combining different separation mechanisms. Furthermore, RAM precolumns have revealed much longer lifetime than that of conventional precolumns [7,9,10,15,16], since the majority of proteins and endogenous compounds are eluted within the void volume of RAM columns.…”