A THz spectroscopy method for quantifying the degree of crystallinity in freeze-dried gelatin/amino acid mixtures: An application for the development of rapidly disintegrating tablets

• J. Darkwah, 
• G. Smith, 
• I. Ermolina

• Leicester School of Pharmacy, De Montfort University, Leicester, UK

Abstract

Objective

In rapidly disintegrating tablets (RDTs) manufactured by freeze-drying processes, the % crystallinity of the freeze-dried matrix underpins the physical properties such as mechanical strength and dissolution profile. This study examines the feasibility of using terahertz pulsed spectroscopy (TPS) as an off-line tool (in the first instance) for assessing the degree of crystallinity in co-freeze dried amino-acid/gelatine mixtures.

Materials and method: Three amino acids (L- alanine, serine and proline) were studied by TPS (in the wave number range of 3 to 100 cm⁻¹) both in the pure crystalline form and in the form of a co-freeze-dried matrix with gelatin (in weight fractions of 10:90, 30:70, 50:50, and 70:30).

Results

In co-freeze dried proline/gelatin matrix no crystallinity was observed using TPS, whereas ∼62% ± 1% (n = 3) and 72% ± 0.5% (n = 3) crystallinity was observed in the co-freeze dried alanine/gelatin matrix (50%w/w and 70%w/w respectively). Similarly, ∼41% ± 0.5% (n = 3) and ∼80% ± 0.5% (n = 3) crystallinity was observed in the serine/gelatin matrix (30% w/w and 50% w/w respectively).

Conclusion

The potential for using TPS as a quantitative in-line tool for determining the degree of crystallinity in a range of complex systems such as RDTs, conventional tablets, sprayed dried micro particles, is suggested from these results

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... of the resultant 9 measurements (n = 3 samples x 3 points).95 2.3 Terahertz spectroscopy The
experimental setup and principles of terahertz pulsed spectroscopy ... A TPS spectra 3000 (TeraView Limited, UK) in transmission mode was used to obtain THz absorption spectra ...