Abstract
Nicotinic acid (1) and its derivatives, namely nicotinamide (8), 3‐pyridinecarbaldehyde (11), 3‐pyridinecarbonitrile (12), 3‐pyridylmethanol (13), and methyl 3‐pirydyl ketone (14) were investigated by NP‐TLC, and RP‐HPTLC. The RF values were obtained from the densitometric analysis. The separation factors ΔRF, RF α, and selectivity α were calculated from the RF values. The comparison and characteristic of chromatographic bands of the examined compounds were presented on the basis of calculated resolutions: RS(c), RS(b), RS(h), and RS(a). The resolutions of substances were determined by visual method (RS(c)) and densitometric method (RS(b), RS(h), and RS(a)). It was affirmed that the densitometric method is correct and the standard method to determine the above mentioned parameters. Furthermore, the R S parameter determined by the visual method for two adjacent substances is always larger than determined by the densitometric method. It was affirmed, that the best separation of the studied compounds was obtained by the RP‐HPTLC technique on RP18WF254 plates, and by use of dioxane‐water in a volume composition of 20∶80. However, 3‐pyridinecarbaldehyde (11) from 3‐pryridinecarbonitrile (12) cannot be separated by the RP‐HPTLC technique. It was also affirmed, that adsorption thin‐layer chromatography (NP‐TLC) in the system of a silica gel 60F254 and the acetone‐n‐hexane mobile phase in a volume composition of 80∶20 provided the optimum conditions for the complete separation of 3‐pyridinecarbaldehyde (11) from 3‐pryridinecarbonitrile (12).
Acknowledgment
This research was financed by the Ministry of Science and Higher Education by resources reserved for science in the years 2005–2008 as research project No. 3 T09A 155 29.