| Suspension concentrate(SC) has been one of most important pesticide formulations owing to its high suspensibility, favorable environmental compatibility and other advantages. However, suspension concentrate belongs to thermodynamic instable system. As a result, undesirable phenomenon which influences the commercial property of the formulation are often observed in the accelerated storage procedure, such as aqueous separation, flocculation and agglomeration. The researchers introduced multicomponent research method to decrease the blindness of formula screening, and then improve its efficiency and predictability. The application performance of orthogonal design, uniform design and response surface method in SC formula were investigated in the current thesis, and the results were listed as follows:Clothianidin 30% SC was prepared using orthogonal design and uniform design(U6*(64)), respectively in the current study. The effect of wetting-suspending agent and viscosity modifier on the aqueous separation ratio, centrifugal sedimentation ratio, viscosity, fluidity, dispersibility, the size distribution and suspensibility of the samples before and after hot storage were investigated integratedly. 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 wereconducted to assess the properties of optimized formulas. The viscosity of all samples prepared based on orthogonal design and uniform design ranged from 144.5 to 317.8 m Pa·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. The ANOVA(analysis of variance) results of orthogonal design indicated that the dosage of TERSPERSE2700, xanthan gum and veegum had significant negative effects on the aqueous separation ratio and centrifugal sedimentation ratio which meant that both the two indexes 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 m Pa·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 aqueous separation ratio of the optimized formula was 4.23±0.19%, while the centrifugal sedimentation ratio was less than 10%. As for uniform design, PLS square model have a good predictability in predicting WSRHS, for which the sample aqueous separation ratio 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 m Pa·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 centrifugal sedimentation ratio. The centrifugal sedimentation ratio and aqueous separation ratio 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 aqueous separation ratio was 9.51±0.20% and the centrifugal sedimentation ratio was 16.63±0.19%. Both the double screening stepwise regression and PLS were capable of optimizing the aqueous separation ratio and centrifugal sedimentation ratio 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. 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 suspension concentrate could be 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.A model thiacloprid 25% suspension concentrate was prepared using Tersperse2700(X1), NR1601(X2), xanthan gum(X3) and veegum(X4). A response surface methodology(RSM) was used to evaluate the influences of four experimental factors on the aqueous separation ratio(R1), centrifugal sedimentation ratio(R2) and viscosity(R3). The results show that the main factors influencing the three responses were X3, X4 and X2 followed by X1; moreover, several interactions were also significant. Multiple-response optimization was performed based on a desirability function, considering the minimum R1, R2, and R3 as well as the financial cost. The integrated optimum conditions were X3 = 0.24 %, X4 = 1.33 %, X2 = 0.50 %, and X1 = 2.90 %(mass fraction). A verification experiment demonstrated that the optimized formula R1, R2, and R3 were 1.69 %, 2.63 % and 257.74 m Pa s with the average relative predicted value errors 7.69 %, 4.18 % and-1.41 %, respectively. The response surface methodology is an effective approach for optimizing the suspension concentrate formula with comprehensive advantages. Clothianidin 30% Suspension Concentrate(U9(94)) was optimized by combining uniform design and response surface method. PLS quadratic polynomial and stepwise regression quadratic polynomial model were used to analyze the results. The effect of wetting-suspending agent and viscosity modifier on the thermal stability and suspensibility. It was indicated that both the two models were capable of predicting the aqueous separation ratio with the R2 being 0.9411 and 0.9999, respectively. However, both the two models were incapable of efficiently predicting the suspensibility before and after hot storage because of the relatively low R2(approximately 0.7). The two formulas proposed by predicting models for aqueous separation ratio were both favorable formulas, of which the aqueous separation ratio were lower than 5% and the suspensibility before and after hot storage were higher than 92%. Besides, stepwise regression quadratic polynomial model was the better one, along with the average relative errors of predicted values being –4.85%. The optimal conditions were as follows: TERSPERSE2700 of 3%, NR1601 of 0.4%, xanthan gum of 0.22% and veegum of 2%. Aqueous separation ratio was the minimum(2.27% ± 0.08%) and the suspensibility before and after hot storage were 92.51%±0.25% and 92.02%±0.46% while favorable dispersibility and flowability were observed under this condition. Fortunately, no flocculation, agglomerate nor knot at the bottom was observed for the preparation even after hot storage. The aqueous separation ratio of samples remained lower than 5% and other performance was also qualified even when the dosage of TERSPERSE2700 was appropriately reduced according to the response surface results. The combination of uniform design and response surface method showed favorable adaptability in the optimization of SC formula. |
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