Heckel analysis

More recently, Heckel analysis was expanded in an attempt to analyze the various sections of the plot to more precisely differentiate the densification behavior of various materials [11] (see Fig. 4). 

Krumme, M., Schwabe, L., and Fromming, K. H. (2000), Development of computerised prodedures for the characterisation of the tableting properties with eccentric machines Extended Heckel analysis, Eur. J. Pharm. Biopharm., 49, 275-286. 

Malamataris, S., and Rees, J. E. (1993), Viscoelastic properties of some pharmaceutical powders compared using creep compliance, extended Heckel analysis and tablet strength measurements, Int. I. Pharm., 92,123-135. 

The results of a study conducted by Muller and Augsburger [16] suggest that the pressure-volume relationship determined during powder bed compression is affected by the instantaneous punch speed profile of the displacement-time waveform for all materials studied, even though they deform by different mechanisms. It appears that the instantaneous punch speed profile of the particular displacement-time waveform is a confounding factor of Heckel analysis. 

The effect of particle size on the compression properties of paracetamol oral dosage forms has been previously reported [62], Heckel analyses plots indicated that the predominant mechanism of compaction of paracetamol was fragmentation with larger particle fractions experiencing more fragmentation than the smaller particles. Furthermore, Heckel analysis also indicated that, for a given applied... 

Linear profiles are the simplest profiles to use for powder compressions. Typically, a sawtooth or v-shaped profile is used where the punch is extended at a constant velocity and retracts at a constant velocity. In theory, during a sawtooth profile, the punch reverses its motion instantaneously between the compression and a decompression strokes. At low speeds (e.g.. <1 mm/sec), the hydraulic response system can easily accommodate this discontinuity. However, at high speeds (>100mm/.sec), the control system may show a small lag in the position-time waveform (<10 milliseconds) as it attempts to rapidly reverse the direction of punch. The sawtooth waveform is commonly used for more fundamental compression studies (e.g.. Heckel analysis), where the desired powder volume reduction is proportional to time. It is also u.seful when evaluating instrument performance during factory acceptance testing. 

The most common variables affecting Heckel analysis are the rate and duration of compression, the degree of lubrication, and even the size and shape of the dies and punches (86) hence these variables should be taken into consideration during analysis. Although the use of the Heckel relationship to study the compression behavior of pharmaceutical powders/granules has been criticized (81), it still remains one of the most commonly used methods in the field of formulation research and development of pharmaceutical solids. 

Hassanpour A, Ghadiri M. Distinct element analysis and experimental evaluation of the Heckel analysis of bulk powder compression. Powder Technol 2004 141 251-261. 

Ollett et al. (1992) also observed that particle failure and subsequent rearrangement was involved during compaction of sucrose and sodium chloride. The effects of water content were greatest for potato starch and sucrose, of intermediate value for the maltodextrin and least for sodium chloride. Deformation stresses determined from the Heckel analysis of compaction data decreased with increasing water content. This was interpreted in terms of plasticization for the amorphous materials, whereas for crystalline materials, lubrication effects in the rearrangements following particle failure were invoked. 

R. W. Heckel, An analysis of powder compaction phenomena, Trans. Metallurg. Soc. AIME, 221, 1001 (1961). 

Guber, A.E., Dittrich, H., Heckele, M., Herrmann, D., Musliga, A., Pfleging, W., Schaller, T., Polymer micro needles with through-going capillaries. Micro Total Analysis Systems, Proceedings 5th pZAS Symposium, Monterey, CA, Oct. 21-25,... 

From tablet height, volume, porosity, and relative density at different stages of densification can be deduced. These variables are plotted as a function of pressure. For analysis, for example, the equations of Heckel [118-120], Kawakita, [121,122], Cooper and Eaton [123], Walker [124], Bal shin [125], and Spnnergaard [126,127] can be used. The equations are given in Table 7. A further overview of these and other equations used can be found in Celik [88],... 

Despite this critique of the Heckel equation, the analysis of Heckel plots has been intensively used for the description of powder compression [128, 133-136], Gabaude et al. [136] stated that the analysis is quite useful when defining preconditions exactly and apply correct displacement measurement. 

D Model Most recently another technique which uses force, displacement, and time has been developed. 3D modeling is a very useful method to characterize the tableting process [3,46,47,155-159], Force is expressed as pressure, time has to be normalized, and from displacement data the porosity according to Heckel [119] is calculated. It is the only possibility to combine these variables during analysis. 

Following Walker s analysis, several other compaction relationships have been proposed by different workers and currently more than a dozen different mathematical descriptions of the compaction process can be found in the literature, each having its own set of benefits and drawbacks. Among the most widely used for pharmaceutical systems include those of Heckel (68-70), Kawakita (70), and Adams (4,71). These different methods will be reviewed in this section. 

B.O. Agiular-Cisneros, M.G. Fopez, F. Richling, F. Heckel, P. Schreier (2002) Tequila authenticity assessment by headspace SPME-HRGC-IRMS analysis of C/ C and O/ O ratios of ethanol. J. Agric. Food Chem. 50, 7520-7523... 

C. Preston, E. Richling, K. Kahle, M. Kraus, W. Hummer, M. Appel, F. Heckel, P. Schreier (2005) Ester synthesis authenticity assessment by stable isotope analysis. In T. Hofmann, M. Rothe, P. Schieberle (eds.) State-of-the-Art in Flavour Chemistry and Biology. DFA, Garching, pp. 358-362... 

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