A rapid NMR method for quantifying low-levels silicone oil in prefilled syringe elastomeric components

Prefilled syringes (PFS) increasingly serve as standalone injection systems and as critical components in autoinjectors, where device performance and patient safety depend on tightly controlled component attributes. Silicone oil (SO) is widely used as a lubricant on syringe barrels, plungers, needles, and elastomeric needle shields to reduce frictional forces; however, accurately quantifying the microgram‑level SO present on individual elastomeric components remains analytically challenging. Here, we present a rapid and sensitive proton nuclear magnetic resonance (¹H NMR) method for direct measurement of SO amount on single elastomeric needle shields. A calibration curve constructed from SO standard demonstrated excellent linearity (R² = 0.999), and the method achieved a limit of detection of approximately 0.2 µg SO per component. Applied to two elastomeric needle shield batches with vendor‑controlled siliconization, the method successfully distinguished between low‑ and high‑SO conditions. In a separate PFS batch with known variability in pull‑off force (POF), an inverse relationship was observed between SO mass and POF: syringes with lower POF exhibited higher SO levels, whereas those with higher POF contained less SO. Overall, this ¹H NMR approach enables fast (<10 min per sample), specific, and quantification of SO on single elastomeric needle shields, providing a practical tool for routine quality control and for correlating siliconization levels with critical device performance attributes.