Chemical and Morphological Fingerprinting of Pharmaceutical Lactose Using FTIR and DIA

Lactose is one of the most widely used pharmaceutical excipients, serving as a filler, diluent, or binder in solid dosage forms such as tablets, capsules, and dry powder inhalers. Its popularity is based on excellent compressibility, compatibility with active ingredients, and favorable sensory properties. However, lactose performance depends not only on its chemical composition but also on particle size and shape, which strongly influence powder flow, compressibility, and dissolution behavior.
According to the European Pharmacopoeia monograph on lactose monohydrate, Ph. Eur. 0187 and the monograph for lactose monohydrate of the United States Pharmacopoeia, infrared absorption spectrophotometry is the primary method for identification. The analysis involves comparing the sample spectrum with the reference spectrum of lactose monohydrate. The resulting Hit Quality Index (HQI) quantifies their spectral similarity, indicating how closely the two spectra match.
Reliable characterization therefore requires assessment of both chemical identity and physical morphology. Fourier Transform Infrared (FTIR) spectroscopy provides molecular-level identification by detecting characteristic vibrational bands linked to functional groups and crystalline forms, allowing confirmation of authenticity and detection of polymorphic variants. This can be used for successful income control of excipients. Dynamic Image Analysis (DIA) complements this by delivering detailed information on particle size distribution and shape, revealing effects of processes such as milling, granulation, or spray drying.
By combining FTIR and DIA, a comprehensive analytical fingerprint of pharmaceutical lactose can be obtained—confirming its chemical identity while elucidating physical characteristics that affect functionality. This integrated approach enhances quality control and supports robust formulation development.