1.Niclosamide ethanolamine salt
Niclosamide ethanolamine salt is a acaricide recommended by the World Health Organization for on-site use in China. It is usually made into 83.1% niclosamide ethanolamine salt WP, 50% niclosamide ethanolamine salt WP, niclosamide ethanolamine salt SC, etc. These preparations need to be dispersed in water when used. They are special snailicides for eliminating snails and controlling schistosomiasis. It has high snail-killing efficiency and long-lasting effect, and also kills snail eggs and tail snails.
2.Problems faced in the preparation of niclosamide ethanolamine salt
There are three major problems when the 83.1% niclosamide ethanolamine salt WP preparation is put into water. The precipitation increases, the particles sink and cause uneven concentration, the surface properties and electrolytes act to cause agglomeration, and block the spraying tools; the chemical stability decreases, the acid-base change of the water accelerates hydrolysis, the dissolved oxygen causes oxidation discoloration, and the active ingredients degrade; the biological activity decreases, the light promotes hydrolysis, reduces the concentration of the drug solution, and weakens the snail-killing effect.
Flocculation and discoloration Flocculation Discoloration
Dispersant SP-NID Compare product 1 Compare product 2
Through a large of experiments, we screened out a dispersant SP-NID, which has the functions of increasing the suspension rate of niclosamide ethanolamine salt and reducing the amount of precipitation; anti-oxidation, preventing the discoloration of niclosamide ethanolamine salt; and eliminating flocculation, improving the stability of the preparation.
3.Observation under a microscope
By observing under a microscope, it can be clearly seen that the niclosamide ethanolamine salt is yellow crystals. In the preparation made from dispersant SP-NID (upper right), no short rod-shaped crystals were observed, indicating that the adjuvant effectively dispersed the niclosamide ethanolamine salt. However, in the samples of compare product 1 (lower left) and compare product 2 (lower right), it can be clearly seen that there are short rod-shaped crystals that are not fully crushed. In particular, in the sample of compare product 2 (lower right), agglomeration phenomenon also occurred.
|
Items |
Dispersant SP-NID |
Compare product 1 |
Compare product 2 |
|
Chemical suspension rate(%) |
94.52 |
86.14 |
75.76 |
|
Water content(%) |
1.72 |
2.13 |
1.96 |
|
pH value |
8.89 |
8.73 |
9.63 |
|
30minsedimentation volume(ml) |
0.08 |
0.13 |
0.16 |
|
Wet sieving(%) |
99.9 |
99.1 |
98.2 |
|
Particle size(D98,μm) |
8.343 |
10.14 |
20.54 |
|
Flocculation and discoloration |
NO |
NO |
NO |
It wa observed that the preparations made of dispersant SP-NID showed better performance. Moreover, the preparations of dispersant SP-NID had less physical precipitation and smaller particle size (D98).
Compare product 2, the adjuvant encapsulation is not good. Under the microscope, the agglomeration phenomenon can be clearly observed; in the wet sieve experiment, yellow particles remained on the wet sieve, which fully demonstrated that the product has obvious deficiencies in dispersibility and stability.