Figure 1: Motivation for localized sampling and the analytical framework for the Dynamic Sampling Platform (DSP). While cell cultures mature, secreted biomolecules (linked to cell status and growth trajectory) are in highest abundance near the cells’ surface. Traditional analysis techniques analyze bulk media, which include temporally averaged biomolecular content and higher relative concentrations of molecules contained in stock media (e.g., fetal bovine serum (FBS), salts) that can mask the signature of quality indicating analytes. Rapid, small volume, localized sampling is an advantageous approach because it enables spatial and temporal probing of the cell culture, detecting the molecules when and where they are secreted. After sampling, DSP rapidly treats the sample for inline CQA characterization. As a platform technology, DSP is easily integrated with a broad spectrum of analytical tools, but for this study DSP was coupled with inline electrospray ionization mass spectrometry (ESI-MS).