Patented in 1985, introduced commercially in 1986, internal-surface reversed phase (ISRP) supports have attracted wide attention. ISRP supports allow the analysis of serum and plasma samples by high pressure liquid chromatography (HPLC) without requiring the prior removal of protein. Proteins cannot enter the pores of ISRP supports and are not adsorbed by ISRP outer surfaces; proteins pass right through ISRP HPLC columns. Therefore, the number of serum injections that given ISRP-guarded ISRP columns can receive runs into the thousands; ISRP columns nicely lend themselves to automation. ISRP indifference to proteins is complemented by the remarkable selectivity toward drugs of its stationary phase, glycine-phenylalanine-phenylalanine (GFF), a selectivity that recently has been shown to extend to peptides. More recently still, it has been shown that ISRP columns can be used to analyze both the free and the bound forms of drugs, even distinguishing among different bound forms. A potential new intrinsically monomeric GFF shows improved retention and surprisingly high chromatographic efficiency.
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