A Microfluidic Approach for Profiling Total Nitrogen Content in Age-Specific Nutritional Formulas Using Microchip Gel Electrophoresis

Accurate assessment of protein content in Foods for Special Medical Purposes (FSMPs) is critical for patients with chronic kidney disease, who require tightly regulated protein intake. This study aimed to develop and apply a rapid, low-volume, and reproducible microchip-based gel electrophoresis method for analyzing total nitrogen (TN) content and electrophoretic profiles in FSMPs. Products of different consistencies (powder, liquid, yoghurt-like) were tested to evaluate the influence of common additives (e.g., milk proteins, stabilizers, sweeteners) on TN levels and protein patterns. The results revealed considerable variation in fractions among brands, largely attributable to additive composition. Notably, TN levels often exceeded the declared protein content, potentially leading to unintended nitrogen overconsumption in clinical settings. Statistical analysis identified significant TN differences between infant and adult FSMPs in liquid formulations, while powdered forms showed no such distinction. These findings highlight the clinical importance of precise analytical monitoring, as discrepancies between measured TN and labeled protein content could compromise dietary management in vulnerable populations. The proposed method provides a reliable tool for FSMP quality control and supports safer nutritional planning in therapeutic diets.