Physico-chemical characterisation of a new polymorph of caffeine

Dichi, E.; Légendre, B.; Sghaier, Mehrez

doi:10.1007/s10973-013-3429-0

Cited by 28 publications

(14 citation statements)

References 41 publications

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“…It shows the enantiotropic behavior of caffeine and specifies the polymorphic phase transition at 137.7 °C confirming the literature data. [25][26] Also it indicates the eutectic composition at ~75 wt.% what is verified in the Tammann plot (Figure 6b). In addition, the latter indicates a partial solid solution behavior of CAF in AMG (indicated by the dashed line in Figure 6b).…”

Section: Amg-caf Systemsupporting

confidence: 61%

“…The supplementary peak observed at 137.7 °C corresponds to the enantiotropic phase transition of caffeine polymorphic form II to form I. [25][26] The eutectic composition is found to be close to 75 wt.% AMG composition. For the AMG-ZMD system, the melting endothermic peak at 101.8 °C refers to the eutectic melting (see Figure 3c), while the eutectic composition is found close to the AMG-ZMD composition of ~50 wt.…”

Section: Differential Scanning Calorimetry (Dsc) Analysismentioning

confidence: 84%

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Multicomponent Materials to Improve Solubility: Eutectics of Drug Aminoglutethimide

Saikia¹,

Seidel‐Morgenstern²,

Lorenz³

2021

Preprint

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Here, we report the synthesis and experimental characterization of three drug-drug eutectic mixtures of drug aminoglutethimide (AMG) with caffeine (CAF), nicotinamide (NIC) and ethenzamide (ZMD). The eutectic mixtures (AMG-CAF, AMG-NIC and AMG-ZMD) demonstrate significant melting point depressions ranging from 99.2 to 127.2 °C compared to the melting point of the drug AMG (151°C) and also show significantly higher aqueous solubilities than that of the AMG. The results presented include the determination of the binary melt phase diagrams and accompanying analytical characterization via X-ray powder diffraction, FT-IR spectroscopy and Scanning electron microscopy.

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Section: Amg-caf Systemsupporting

confidence: 61%

Section: Differential Scanning Calorimetry (Dsc) Analysismentioning

confidence: 84%

Multicomponent Materials to Improve Solubility: Eutectics of Drug Aminoglutethimide

Saikia¹,

Seidel‐Morgenstern²,

Lorenz³

2021

Preprint

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“…This compound exists in a variety of solid forms, for which the structures of two anhydrous polymorphs and one monohydrate are known, Fig. 1 [ 44 , 45 ]. Both anhydrous polymorphs contain highly disordered caffeine molecules.…”

Section: Introductionmentioning

confidence: 99%

The effect of ball mass on the mechanochemical transformation of a single-component organic system: anhydrous caffeine

2018

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ABSTARCTMechanochemical methodologies, particularly ball milling, have become commonplace in many laboratories. In the present work, we examine the effects of milling ball mass on the polymorphic conversion of anhydrous caffeine. By investigating a single-phase system, the rate-limiting step of particle-particle contact formation is eliminated. It is found that larger milling balls lead to considerably faster conversion rates. Modelling of the transformation rate suggests that a single, time-independent rate constant is insufficient to describe the transformation. Instead, a convolution of at least two rate-determining processes is required to correctly describe the transformation. This suggests that the early stages of the transformation are governed only by the number of particle-ball collisions. As the reaction proceeds, these collisions less frequently involve reactant, and the rate becomes limited by mass transport, or mixing, even in originally single-phase systems, which become multi-phase as the product is formed. Larger milling balls are less hindered by poorly mixed material. This likely results from a combination of higher impact energies and higher surface areas associated with the larger milling balls. Such insight is important for the selective and targeted design of mechanochemical processes.

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“…The anhydrous α‐form, also known as form I, forms when β‐caffeine is heated above 155 °C (Table 1) (Edwards et al., 1997); however, α‐caffeine is not stable below the transition temperature and will convert back to the β‐form within several days (Kishi & Matsuoka, 2010) to months (Epple, Cammenga, Sarge, Diedrich, & Balek, 1995). A third anhydrous caffeine form (form III) has also been proposed to form upon caffeine sublimation at low pressures (approximately < 150 °C and approximately < 0.5 bar) (Dichi, Legendre, & Sghaier, 2014), although this form does not seem to be widely available. The hydrate form of caffeine is a nonstoichiometric channel hydrate crystal that is usually a 4/5 hydrate (four water molecules to five caffeine molecules with a 6.91% wet basis moisture content [MC wb ] and a 7.42% dry basis moisture content [MC db ]), but will exist as a 5/6 crystal hydrate (7.18% MC wb and 7.74% MC db ) in water or at approximately 100% RH (Bothe & Cammenga, 1980; Griesser & Burger, 1995).…”

Section: Introductionmentioning

confidence: 99%

Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

Allan

Owens

Mauer

2020

Journal of Food Science

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Caffeine is a hydrate‐forming polymorphic crystalline compound that can exist in α, β, and hydrate forms. Phase transitions between hydrate and anhydrous forms of a crystalline ingredient, and related water migration, can create product quality challenges. The objective of this study was to determine the relative humidity (RH)–temperature phase boundary between anhydrous β‐caffeine and caffeine hydrate. The β‐caffeine→caffeine hydrate and caffeine hydrate→β‐caffeine RH–temperature transition boundaries were determined from 20 to 45 °C using a combination of water activity (aw) controlled solution and vapor‐mediated equilibration, moisture sorption, powder X‐ray diffraction, and Fourier‐transform infrared spectroscopy techniques. Two transition boundaries were measured: the β‐caffeine→caffeine hydrate transition boundary (0.835 ± 0.027 aw at 25 °C) was higher than the caffeine hydrate→β‐caffeine transition boundary (0.625 ± 0.003 aw at 25 °C). Moisture sorption rates for β‐caffeine, even at high RHs (>84% RH), were slow. However, caffeine hydrate rapidly dehydrated at low RHs (<30% RH) into a metastable transitional anhydrous state with a similar X‐ray diffraction pattern to metastable α‐caffeine. Exposing this dehydrated hydrate to higher RHs (>65% RH) at lower temperatures (20 to 30 °C) resulted in full restoration to a 4/5 caffeine hydrate. This transitional anhydrous state was unstable and converted to a less hygroscopic state after annealing at 50 °C and 0% RH for 1 day. It was postulated that the caffeine hydrate→β‐caffeine was the true β‐caffeine↔caffeine hydrate phase boundary and that β‐caffeine could be metastable above the caffeine hydrate→β‐caffeine transition boundary. These caffeine RH–temperature transition boundaries could be used for selecting formulation and storage conditions to maintain the desired caffeine crystalline form. Practical Application Caffeine can exist as either an anhydrous (without water) or hydrate (internalized water) crystalline state. The stability of each caffeine crystalline form is dictated by humidity (or water activity) and temperature, and these environmental stability boundaries for the caffeine crystalline forms are reported in this manuscript. Conversions between the two crystalline states can lead to deleterious effects; for example, the presence of caffeine hydrate crystals in a low water activity food (e.g., powder) could lead to the relocation of the water in caffeine to other ingredients in the food system, leading to unwanted water–solid interactions that could cause clumping and/or degradation.

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Physico-chemical characterisation of a new polymorph of caffeine

Cited by 28 publications

References 41 publications

Multicomponent Materials to Improve Solubility: Eutectics of Drug Aminoglutethimide

Multicomponent Materials to Improve Solubility: Eutectics of Drug Aminoglutethimide

The effect of ball mass on the mechanochemical transformation of a single-component organic system: anhydrous caffeine

Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

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