Improvement of the synthesis of lutetium bisphthalocyanine using the Taguchi method

Abstract

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 (L_C) 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.