Three commercial gradient systems were compared to clarify the problems associated with gradient elution. The precision of the gradient elution was evaluated as the reproducibilities (RSD) of retention times of aromatic compounds and proteins separated on a reversed phase column. Actual gradient elution curves differ considerably from each other among the three systems tested, which affected the resultant chromatograms. Furthermore, RSD values for proteins were larger than those of aromatic

more »

... ounds for all three systems; the retention of proteins was sensitive to a slight change of the resultant gradient elution pattern. Based on these findings, a method is presented for the evaluation of gradient systems by using proteins as sensitive markers.