Interinstrumental method transfer of a capillary electrophoretic separation of angiotensin II and five derivatives: Evaluation and update of earlier developed guidelines.

The increased interest in the separation of peptides, proteins, immunoglobulins, and polynucleotides, led to an increased demand for appropriate analytical methodologies and instrumentation. CE, because of its unique separation mechanism and high efficiency, is frequently used in the analysis of those molecules. In this study, a CE method for the separation of six angiotensin analogues was developed in the first step. In the second step, the method was transferred to a CE instrument of another brand, taking into account guidelines defined earlier about the interinstrumental transfer of CE methods. Although previously successful, the application of these guidelines during this study was not able to maintain the baseline separation. Further research on the instrumental differences revealed that the electrical resistance on both instruments differed. At constant current, the electrical resistance, generated voltage, and separation efficiency on the Agilent instrument were lower than on the Beckman instrument. Increase of the electrical resistance, by reducing the capillary temperature, leads to an increased applied voltage and separation efficiency on the Agilent system. The guidelines developed earlier were, therefore, updated with an additional step equalizing the electrical resistances, which led to a successful interinstrumental analytical method transfer for the separation of six angiotensin derivatives.