Abstract: 【Objective】The objective of this study is to discuss the advantages and disadvantages in application of two multi-factor experimental designs in SC (suspension concentrate) formula. Effectively providing reference for the application of orthogonal design and uniform design in pesticide formulation was also expected. 【Method】 Clothianidin 30% SC was prepared based on orthogonal design and uniform design after the wetting-suspending agents with favorable wettability were selected by applying flow point method. The effect of wetting-suspending agent and viscosity modifier on the water separation rate after hot storage (WSRHS), precipitation rate after centrifugation (PRC), viscosity, fluidity, dispersibility, the size distribution (including D₁₀, D₅₀ and D₉₀) and suspensibility of the samples before and after hot storage were investigated. The main effect plots were used to analyze the results of orthogonal design while stepwise regression and partial least squares (PLS) were used to analyze that of uniform design. Finally, validation tests were conducted to assess the properties of optimized formulas.【Result】The viscosity of all samples prepared based on orthogonal design and uniform design ranged from 144.50 to 317.84 mPa·s and all the samples exhibited favorable fluidity and dispersibility. Particle size became larger after hot storage due to ostwald ripening. The D₁₀, D₅₀ and D₉₀ were 0.56-1.00, 0.88-1.53 and 1.77-2.68 μm for samples before storage and 0.76-1.02, 1.12-1.56 and 2.07-3.25 μm for samples after hot storage, respectively. Little change was observed for the suspensibility even after hot storage, of which the suspensibility ranged from 91.88% to 96.39% before storage and 91.91% to 96.13% after hot storage. Given the favorable performance the authors had measured which could satisfy the general requirements of SC quality control, only WSRHS and PRC were mainly optimized in this study. The ANOVA (analysis of variance) results of orthogonal design indicated that the dosage of T2700, xanthan gum and veegum had significant negative effects on the WSRHS and PRC which meant that both the WSRHS and PRC decreased with the increasing dosage of the three adjuvants. However, the dosage of NR1601 showed no significant impact on the two dependent variables. The viscosity of optimized sample based on orthogonal design was 229.6 mPa·s, while its fluidity and dispersibility were favorable. The suspensibility of the optimized sample before and after hot storage were (94.76±0.70)% and (93.50±0.20)%, respectively. The WSRHS of the optimized formula was (4.23±0.19)%, while the PRC was less than 10%. As for uniform design, PLS square model have a good predictability in predicting WSRHS, for which the sample WSRHS of the optimized formula was (2.55±0.03)% and the PRC being (4.36±0.21)%. The viscosity of optimized sample was 324.16 mPa·s, while its fluidity and dispersibility were favorable. The suspensibility before and after hot storage were (93.19±0.09)% and (92.77±0.22)%, respectively. The particle size was small and the size distribution was narrow. PLS linear model exhibited favorable predictability in predicting PRC. The PRC and WSRHS of the optimized formula were (7.75±0.14)% and (5.24±0.19)%, respectively. The predictability of stepwise regression models was poor for both the two properties. What’s more, the optimized formula was not optimum formula, of which the WSRHS was (9.51±0.20)% and the PRC was (16.63±0.19)%. Both the double screening stepwise regression and PLS were capable of optimizing the WSRHS and PRC at the same time while validation test confirmed that the former model matched the final results better, but unfortunately, even optimized formula of the former model was not optimum. 【Conclusion】 Although orthogonal design required a large test number, the data analysis method was simple and easy to grasp. Combining the main effect plots and ANOVA results, the preparation of clothianidin 30% SC was effectively optimized. Although the robustness of uniform design was poorer than orthogonal design, it required fewer experiments, which could significantly decrease financial cost. Ideal formula could also be obtained provided that the complicated statistics and analysis methods were mastered.

Key words: orthogonal design, uniform design, partial least squares, stepwise regression, physical stability