除草劑施得圃微膠囊劑型之研究

Abstract

農藥使用的安全問題逐漸受到重視，為降低農藥使用對環境及人體造成的風險，新的安全劑型持續被開發。微膠囊 (Microcapsule) 製劑能減少有機溶劑的使用，降低環境對農藥有效成分之影響，延長農藥的持效期以減少藥劑的重複施用，減少對使用者的危害與對環境的衝擊，因此被視為安全性較高的劑型之一。本研究以旱田常用選擇性除草劑施得圃 (Pendimethalin) 進行微膠囊劑型的開發，利用界面聚合法使分別溶解於油、水相之聚合單體 (Monomer) 於兩相界面處進行聚合反應，形成微膠囊殼包覆施得圃，油相所使用之有機溶劑為毒性較低且閃火點較高之油漆溶劑-150，減少製劑成品中溶劑對於環境的影響。經測試後最佳製備條件為添加4% 木質磺酸鈉、均質機轉速8000 rpm，使用此一條件能穩定製備出完整球形且表面平滑之微膠囊，所製備出三個批次之微膠囊平均粒徑2.5-2.7 μm，並且粒徑分布相當；平均載藥量26.54-27.71%；包封率90.10-94.81%，顯示施得圃能被微膠囊良好包覆，結果呈現依此條件能穩定製備出三個特性相同之批次。於控制釋放的試驗中，製劑成品之累積釋放曲線與Ritger-Peppas方程式擬合後，計算出n = 0.39，表示微膠囊中施得圃釋出機制為菲克擴散 (Fickian diffusion)。微膠囊劑於萌芽抑制率測試中，因為試驗觀察時間較短，微膠囊劑型藥效略低於直接施用乳劑。對於非目標生物慢毒性評估試驗中，測得施得圃微膠囊劑對小球藻 (Chlorella vulgaris) 之EC50 (96-h) 為1.054 mg L-1，與文獻中乳劑之毒性相比較低。本研究探討微膠囊製備的方法，並以商業生產可行性考量進行條件之建立，並針對所製備劑型進行分析與評估，結果顯示將施得圃製成微膠囊劑型後在維持藥效的狀況下也能降低對於環境生態的風險。

People have gradually paid more attention to the issue of pesticide safety nowadays. To decrease the risk of pesticide to the environment and human body, novel formulations have been developed. Microcapsule can decrease the use of organic solvent and the effect of environment to the pesticide. Furthermore, it can also extend the pesticide duration, so that fewer times of applying pesticide is needed, and users’ security concerns and environmental pollution would decrease. Pendimethalin, a common herbicide in upland field, was selected in this study. The monomer units were dissolved into water and oil phase separately. Then the polymerization occurs at the interface between two phases. Microcapsules were formed and pendimethalin was captured inside of it. The solvent of oil phase is high-flash aromatic naphtha 150, which has lower toxicity and higher flash point, making the microcapsule more eco-friendly. By adding 4% sodium lignosulfonate and homogenizing at 8000 rpm, round microcapsule with smooth surface can be stably produced. In three batches of microcapsules, the average diameter is 2.5-2.7 μm and the average loading content is 26.54-27.71%. The encapsulation efficiency is 90.10-94.81%, showing that pendimethalin is encapsulated well. These results indicated that under this condition, microcapsule can be stably produced with similar characteristics. In the controlled release experiment, Ritger-Peppas equation was fitted to the release profiles of pendimethalin. The parameter n is 0.39, showing that the mechanism follows the Fickian diffusion. Microcapsule has worse performance in the germination test because of short experiment time, compared to emulsifiable concentrate. In the assessment of toxicity to non-target aquatic organisms, the EC50 value of microcapsule was 1.054 mg L-1 on Chlorella vulgaris. In this research, the process of microcapsulation was investigated based on commercial production feasibility. The result showed that by using microcapsule, the environmental risk of pendimethalin decreased while maintaining the efficacy.