lengths are better suited to the determination of A(1%,1 cm) values,because changes in path length resulting from removal and replacement of probe tips cannot occur.If the stability of the pharmaceutical permits,quantification can be carried out with the aid of the absorption coefficient,which is less labour intensive than methods of quantification involving standard solutions.In the case of mirror probes it is possible to change tips,and thus quickly and cheaply change the optical path length to fit the particular requirements.However,probes of this type have a smaller linear range. Probe positioning in dissolution analysisOther factors such as the thickness of the immersion probe and particularly how it is positioned in the vessel must also be taken into account.In principle,there are four ways of doing this (Table 1).If the immersion probes remain in the dissolution vessel throughout the dissolution test,particular attention must be paid to the changed hydrodynamic conditions in the dissolution vessel.Thick immersion probes have a larger effect on the hydrodynamics in the vessel than thinner ones [2]. It is,therefore,sometimes a good idea to use special thin immersion probes to minimize the effects on the hydrodynamics.If the influence of immersion probes permanently located in the vessel has any effect at all on the rate of dissolution of the medic-1 Dissolution Technologies |

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Nucleosides and Nucleotides. Part 22. Synthesis of a Tridecanucleoside Dodecaphosphate Containing the Unnatural Base Z(1H)-PyrimidinoneThe tridecanucleosid dodecaphosphate d(TpTpMpCpCpTpCpApApApApTpC incorporating the modified nucleoside 1-(2'-deoxy-~-~-ribofuranosyl)-2( 1H)-pyrimidinone (Md, 2) was synthesized using the triester method. The intermediates were the suitably protected trimer d(TpTpM) and the pentamer d(TpTpMpCpG). The latter was condensed with the protected octamer d(TpCpApApApApTpC) to yield the desired tridecanucleotide.