The focus of this master's thesis was to research the effect of surface tension of media on the release and swelling of the matrix tablets with hydroxypropyl methylcellulose (HPMC).Tablets containing diclofenac sodium were dissoluted in 0,001 M or 0,01 M hydrochloric acid with addition of sodium dodecyl sulfate (SDS) or polysorbat 20 (Tween® 20) in concentrations ranging from 0,05 to 2 % (m/V). Swelling studies were conducting in 0,001 M hydrochloric acid with addition of sodium dodecyl sulfate (SDS) or polysorbat 20 (Tween® 20) in concentrations ranging from 0,05 to 2 % (m/V). We determined the critical micellar concentration (CMC) of SDS and Tween® 20 in different media. On the basis of measuring conductivity of SDS in 0,001 M hydrochloric acid with the help of the conductometer we determined the CMC at room temperature (6,78 mM) and at 37 °C (7,14 mM). We compared these results with those gained from surface tension measurements which gave us CMC values 5,20 mM at room temperature and 4,16 mM at 37 °C. We noticed a big difference in the obtained CMC values between both methods. When measuring surface tension we noticed the occurrence of a minimum on the curve which depicts the dependence of surface tension on SDS concentration. A possible cause for the emergence of the minimum, as described in the literature, could be the presence of impurities in the SDS such as dodecyl alcohols. We also determined CMC with surface tension measurements in 0,01 M hydrochloric acid and 4 times diluted McIlvaine buffer at pH values 3 and 4. The curve was similar to those previously mentioned. When we measured the surface tension of Tween® 20 the shape of the curve was as expected, a steep fall followed by a constant value. CMC was determined in 0,001 M hydrochloric acid at room temperature (0,02 mM) and at 37 °C (0,02 mM). Large percentage of Na-DF was released in 0,001 M hydrochloric acid when compared with 0,01 M. 0,001 M hydrochloric acid has a higher pH value and thus a larger percentage of the substance is ionised. With addition of surfactants (SDS and Tween® 20) which concentration was higher than the CMC value the percentage of released substance increased. At concentrations lower than the CMC value less substance was released in comparison with media when no surfactants were added. More substance was released when we added SDS, compared to added Tween® 20. During the release test in 0,001 M hydrochloric acid we observed swelling of the tablets with a dissoGUARD® camera system. Conclusion on the effect of surfactant on the swelling of tablets was made on the basis of thickness measurements, which gave us more relevant values. The tablets were the most swollen in 0,001 M HCl without the addition of surfactants, then the swelling decreased with SDS and Tween® 20 concentration increase. The smallest swelling of the tablets was at the 2 % SDS concentration.
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