Improvement of the synthesis of lutetium bisphthalocyanine using the Taguchi method
In this work, a Taguchi experimental design has been used to identify important factors that influence the procedure of synthesis and purification of the lutetium bisphthalocyanine (LuPc2). The working conditions have been improved using an L8 (27) experimental design. A statistical analysis of the experimental data revealed that the most influential factor in the yield is the amount of the starting material (AR), with a 34.4% contribution, followed by the way of performing two chromatographies (C), sequentially or in parallel (26.8%), the temperature of the reaction T (17.8%), the type of chromatography TC, standard or flash (9.1%), and lastly, the volume of the sample injected in the column (5.4%). The time of the reaction (t) and the length of the column (LC) had little effect on the yield. Noise (N) was found to have a negligible influence on the throughput. Maximum yield (20.0%) was obtained when the synthesis was carried out at 280 °C (T) during 1 h 30 min (t) using 0.5 g of lutetium acetate (AR) and performing a standard chromatography (TC) on neutral alumina, injecting 30 ml (V) of the reaction mixture in two columns performed in parallel (C). This yield represents an increase of 186% in relation to the 7% obtained before the application of the Taguchi method. Under these conditions the yield is not significantly influenced by variability of external factors, which validates the proposed procedure.