Limit of Detection of Raman Spectroscopy Using Polystyrene Particles from 25 to 1000 nm in Aqueous Suspensions

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Nanotechnology

Background:

• Raman spectroscopy is a powerful technique for identifying microorganisms and small particles.
• Polystyrene particles of 25-1000 nm size are comparable to viral particles and aggregates.
• Accurate detection limits are crucial for applying Raman spectroscopy in biological and manufacturing contexts.

Purpose of the Study:

• To determine the limit of detection (LOD) for polystyrene particles of varying sizes using confocal Raman microscopy.
• To characterize the Raman spectral signatures of polystyrene particles in aqueous suspensions.
• To assess the non-destructive nature of Raman spectroscopy for particle analysis.

Main Methods:

• Confocal Raman microscopy with a 785 nm laser and 5x objective lens.
• Kernel partial least-squares modeling to establish minimum and maximum LOD (LODmin and LODmax).
• Dynamic light scattering (DLS) to confirm non-destructive analysis.

Main Results:

• The prominent Raman peak at 1001 cm⁻¹ (ring breathing mode) was identified for polystyrene particles.
• LOD for 50 nm particles ranged from 1.80 × 10¹² to 8.31 × 10¹² particles/mL.
• LOD for 1000 nm particles ranged from 5.11 × 10⁸ to 2.53 × 10⁹ particles/mL.
• Raman spectroscopy was confirmed as non-destructive using DLS.

Conclusions:

• Polystyrene particle characterization provides foundational data for Raman spectroscopy applications.
• Raman spectroscopy demonstrates significant potential for detecting small particles in aqueous suspensions.
• This technique could be valuable for real-time monitoring in vaccine manufacturing.