High volume injections of biological samples for sensitive metabolite profiling and quantitation.

An online preconcentration approach was developed allowing the injection of very high volumes of biological samples, thereby greatly increasing sensitivity while maintaining LC resolution. The approach was applied to the analysis of radioactive samples from both in vitro and in vivo metabolism studies where typically the concentration of radioactivity given is often limited, while sample volume is usually not. The described online preconcentration approach reduces sample preparation and, therefore, also the risk for degradation and recovery issues often seen with offline preconcentration methods. In addition to facilitating the identification and profiling of low level metabolites within a sample, the described approach also provides robust quantitative analysis of samples derived from a range of biological matrices. The application of this approach is illustrated on real life samples from different matrices and containing drugs and metabolites with a wide variety in polarity, more specifically the analysis of extracts derived from an in vitro hepatocyte incubation, 36mL of blood/acetonitrile (1/1, v/v; 28dpm/mL) and 72mL of urine/methanol (9/1, v/v; 208dpm/mL).