Effect of Particle Size Reduction on the Surface Energy of Sucrose

Investigating how processing-induced particle size reduction affects the surface energy of sucrose, characterised using iGC-SEA, PXRD, SEM, and BET nitrogen adsorption.

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At a glance

  • Outcome: Processing route influences surface energy more significantly than particle size alone, no direct trend observed between BET specific surface area and surface energy
  • Tools: iGC-SEA, PXRD, SEM, BET nitrogen adsorption
  • Skills: surface energy heterogeneity profiling, Dorris-Gray methodology, acid-base characterisation, solid-state characterisation
  • Result highlight: the industrially milled Fine sample exhibited higher surface energies and greater heterogeneity than the granulated samples, despite similar particle size fractions being achievable by both routes

Overview

Does particle size reduction change the surface energy of sucrose and is that change driven by particle size or by how the size reduction was achieved? Three sucrose fractions were produced via two distinct processing routes and characterised by iGC-SEA alongside complementary solid-state techniques. The work forms an independent case study undertaken during an industrial placement at Resolian Analytical Sciences, and has been submitted as a poster abstract to ARS 2026.

Status: Poster complete - abstract submitted to ARS 2026, awaiting outcome.

Objectives

  • Produce sucrose fractions via two processing routes spanning a range of particle sizes
  • Characterise dispersive and specific surface energy heterogeneity profiles using iGC-SEA
  • Assess acid-base character (Ka, Kb) as a function of surface coverage
  • Complement iGC-SEA with SEM, PXRD, and BET to provide a full solid-state picture
  • Determine whether surface energy differences are attributable to particle size or processing route

Scope

Particle size fractions:

Fraction Route Size range
Coarse Pestle and mortar grinding + sieving 500–180 µm
Medium Pestle and mortar grinding + sieving 150–45 µm
Fine Industrial milling + sieving 45–30 µm

Techniques:

iGC-SEA PXRD SEM BET nitrogen adsorption

Approach

  • Surface energy heterogeneity profiles determined using Dorris-Gray methodology and peak centre-of-mass parameters across fractional surface coverages (0.005–0.12 n/nm⁻¹)
  • Acid-base character quantified via Ka and Kb across the same surface coverage range
  • BET used to determine specific surface area
  • SEM used to assess particle morphology and surface texture
  • PXRD used to assess crystallinity across fractions

Results

1) BET surface area

BET specific surface area did not increase monotonically with particle size reduction, attributed to differences in surface texture and adhered fine particle content as observed by SEM.

Takeaway: surface area alone is not a reliable predictor of surface energy behaviour in these samples.

2) PXRD

PXRD confirmed consistent crystallinity across all fractions. Baseline characteristics in the Fine sample suggested a possible amorphous contribution from industrial milling.

3) iGC-SEA — dispersive surface energy

The industrially milled Fine sample exhibited higher surface energies and greater heterogeneity relative to the granulated Coarse and Medium samples — despite overlapping particle size ranges being achievable by both routes.

Takeaway: processing route, not particle size alone, is the dominant driver of surface energy differences.

4) Acid-base character (Ka/Kb)

Across all fractions, the Ka/Kb ratio decreased at higher surface coverages, indicating electron-donating (basic) character concentrated at lower-energy surface sites.

Interpretation

Key finding

Processing route influences surface energy more significantly than particle size alone. The industrially milled Fine fraction shows distinct surface energy characteristics that cannot be explained by particle size or surface area differences alone, pointing to mechanically activated surface modification during milling.

Implications

Processing-induced surface energy changes could affect downstream powder behaviour — including interparticle adhesion, flow, and caking tendency with direct relevance to pharmaceutical powder manufacturing and formulation.

What I learned

  • Hands-on experience with iGC-SEA instrumentation and data interpretation in a GMP-regulated CRO environment
  • Applying Dorris-Gray methodology and acid-base analysis to a pharmaceutical excipient
  • Interpreting complementary solid-state data (SEM, PXRD, BET) in the context of iGC-SEA findings
  • Scientific communication for an external conference — abstract writing and poster design
  • Conducting and presenting an independent case study within an industrial placement