Improving the LC-MS bioanalysis of hydrophilic peptides utilizing vacuum-based sample preparation

Hydrophilic peptides present great challenges for LC-MS analysis. Although the LC-MS method provides specificity and sensitivity, sample preparation is critical for bioanalytical assay performance. A practical sample preparation approach for improving the LC-MS analysis of hydrophilic peptides was developed, using hydrophilic isoforms of the Amyloid-β peptides as an example. A typical sample preparation procedure for peptides from biological matrices employs immunoaffinity purification; however, the high content of organic solvent in the elution buffer may cause insufficient chromatographic retention of the analytes on a RPLC column. By utilizing lyophilization or speed-vacuum drying followed by reconstitution with an aqueous solvent, the subsequent LC-MS bioanalysis showed these polar peptides being retained on the RPLC column and also an improved MS response. This approach is applicable for analytical studies on hydrophilic peptides in biological matrices.