Accurate size determination of PS latex nanoparticles in aqueous solution using pulsed field gradient nuclear magnetic resonance spectroscopy

Study on release suppression of cinnamaldehyde from κ-carrageenan gel by HR-MASNMR and pulsed field gradient NMR (PFG-NMR)

Aiming toward the production and characterization of delicious and functional gel foods, this communication studies the flavor release from cinnamon-containing κ-carrageenan gel. Cinnamaldehyde, which provides the flavor of cinnamon, was released in a trace amount from the gel and detected by flame ionization detector gas chromatography. The retention of cinnamaldehyde in κ-carrageenan gel and the interaction between flavor and polysaccharide were investigated by high-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) and pulsed-field gradient NMR (PFG NMR). The intact cinnamaldehyde in the gel was also observed by HR-MAS NMR. The relative mobility difference of the flavor and polysaccharide molecules was observed from the diffusion-ordered NMR spectrum of PFG NMR.

Development of a standard method for nanoparticle sizing by using the angular dependence of dynamic light scattering

A standard method for nanoparticle sizing based on the angular dependence of dynamic light scattering was developed. The dependences of the diffusion coefficients for aqueous suspensions of polystyrene latex on the concentration and scattering angle were accurately measured by using a high-resolution dynamic light-scattering instrument. Precise measurements of the short-time correlation function at seven scattering angles and five concentrations were made for suspensions of polystyrene latex particles with diameters from 30 to 100 nm. The apparent diffusion coefficients obtained at various angles and concentrations showed properties characteristic of polystyrene latex particles with electrostatic interactions. A simulation was used to calculate a dynamic structure factor representing the long-range interactions between particles. Extrapolations to infinite dilution and to low angles gave accurate particle sizes by eliminating the effects of long-range interactions. The resulting particle sizes were consistent with those measured by using a differential mobility analyzer and those obtained by pulsed-field gradient nuclear magnetic resonance measurements.