Thermal analysis methods are well-established techniques in research laboratories of pharmaceutical industry. The robustness
and sensitivity of instrumentation, the introduction of automation and of reliable software according to the industrial needs
widened considerably the areas of applications in the last decade. Calibration of instruments and validation of results follow
the state of the art of cGMP as for other analytical techniques. Thermal analysis techniques are especially useful for the
study of the behavior of the poly-phasic systems drug substances and excipients and find a unique place for new delivery systems.
Since change of temperature and moisture occur by processing and storage, changes of the solid state may have a considerable
effect on activity, toxicity and stability of compounds. Current requirements of the International Conference of Harmonisation
for the characterization and the quantitation of polymorphism in new entities re-enforce the position of thermal analysis
techniques. This challenging task needs the use of complementary methods. Combined techniques and microcalorimetry demonstrate
their advantages. This article reviews the current use of thermal analysis and combined techniques in research and development
and in production. The advantage of commercially coupled techniques to thermogravimetry is emphasized with some examples.
An HPTLC method has been established for rapid and reliable identification of
raw material in a cGMP environment. Based on authenticated botanical reference material the method enables discrimination of
from the closely related species
and from the common adulterant prickly pear cactus (
). HPTLC was performed on silica gel with chloroform-methanol-water 70:30:3 (
) as mobile phase. The method was validated for specificity, reproducibility, and robustness.
Thin-layer chromatography (TLC) is generally regarded as a common analytical technique. Everybody ‘knows’ it and it is used to some extent in almost every laboratory in the world. Unfortunately for most analysts TLC remains what it has been for many years — a rapid, simple, inexpensive, and not very precise tool. When one considers the latest technical and methodological developments, however, modern high-performance thin-layer chromatography (HPTLC), also known as planar chromatography, is a reliable and powerful analytical technique, which can be in full compliance with current good-manufacturing practice (cGMP). TLC is the method of choice when many samples must be compared, when flexibility is important, and when rapid quantitative and semi-quantitative data are needed at low cost per sample.
The effects of an intraperitoneal (i.p.) injection of different doses of sildenafil, a cyclic guanosin monophosphate (cGMP) specific phosphodiesterase type 5 (PDE 5) inhibitor, on memory retention of young (2-month-old) and middle aged (12-month-old) male Wistar rats were investigated. Passive avoidance behaviour was studied in a one trial learning, step - through type, passive avoidance task utilizing the natural preference of rats for a dark environment. In each category (young or middle-aged) different groups of rats received vehicle or sildenafil (1, 3, 10, 20 mg*kg-1, i.p.) immediately after training and one group remained uninjected serwing as control. Retention latencies were measured 48 h later. To asses a possible non-specific proactive effect of sildenafil, the response latencies in a group of rats not receiving foot shock were also tested. The results showed that the post-training i.p. administration of sildenafil did not facilitate retention performance of a passive avoidance response in both young and middle aged rats compared to control or vehicle groups. Also, sildenafil did not affect response latencies in rats not having received the footshock on the training trial, indicating that sildenafil does not show a non-specific proactive affect on retention performance. The comparison of retention time between young and middle aged rats showed that the memory of the latter had been significantly reduced. In conclusion, this study suggests that sildenafil has no effects on memory retention in Wistar rats.