| CPC B01J 13/14 (2013.01) [A01N 25/28 (2013.01); A01N 43/56 (2013.01)] | 1 Claim |
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1. A method for preparing a pyraclostrobin microcapsule based on sodium alginate, comprising:
a) accurately weighing pyraclostrobin original drug into a beaker, adding ethyl acetate to the beaker, placing the beaker on a magnetic stirrer and stirring until the original drug is completely dissolved;
b) adding an emulsifier and ddH2O dropwise into the beaker, keeping the stirring speed of 400 r/min to obtain a drug-containing solution, and emulsifying evenly for 10-20 minutes; wherein a mass ratio of the emulsifier to ddH2O is 1:9-11;
c) weighing sodium alginate to a beaker, adding ddH2O, and placing the beaker in a water bath at 60° C.; keeping stirring at a constant temperature until the sodium alginate is completely dissolved and fixing volume with ddH2O to obtain a solution, ultrasonically degassing the solution with an ultrasonic cleaning machine, placing the beaker on a magnetic stirrer, and keeping the stirring speed of 400 r/min and stirring to obtain a sodium alginate solution; wherein the sodium alginate solution is 1% by mass concentration, wherein the emulsifier emulsifies the ethyl acetate and the sodium alginate to generate a homogeneous emulsion without precipitation;
d) slowly dropping the drug-containing solution fully emulsified in the step b into the sodium alginate solution with a burette, stirring at a constant speed on a magnetic stirrer until fully mixed, and performing ultrasonic degassing again to obtain a mixed solution;
e) taking the mixed solution in the step d in a beaker, adding dropwise 5% calcium carbonate-water mixed solution, and mixing and stirring to obtain another mixed solution; wherein the calcium carbonate-water mixed solution is added dropwise within 3 minutes;
f) taking liquid paraffin in a grinding cup, adding the emulsifier into the grinding cup, and keeping the stirring speed of 1000 r/min and pre-stirring for 5 minutes with a multi-purpose dispersing grinder;
g) emulsification stage: after the liquid paraffin and emulsifier are mixed evenly, keeping the stirring speed of 1000 r/min, adding the mixed solution in the step e evenly and slowly to the liquid paraffin with a burette, and continuing to stir evenly for 10 minutes to obtain further another mixed solution;
h) cross-linking reaction stage: keeping the stirring speed of 1000 r/min, taking paraffin oil containing 87.5 mmol/L glacial acetic acid and adding dropwise to the mixed solution in the step g, such that the mixed solution is fully cross-linked;
i) after the cross-linking reaction is completed, fully washing an oil phase with an acetate buffer solution pH 4.5, separating for obtaining a microcapsule slurry with a separatory funnel, and pack the microcapsule slurry in a centrifuge tube; and
j) centrifuging the microcapsule slurry at −4° C. and 10,000 r/min for 15 minutes, pouring off supernatant, placing the centrifuge tube at 4° C. for 1 hour and at −20° C. for 3 hours, placing the centrifuge tube in a vacuum freeze dryer for freeze drying at −50° C. for 42 hours to obtain microcapsule powder, and sealing and storing the microcapsule powder for backup;
wherein,
a mass ratio of the pyraclostrobin to the ethyl acetate is 1:1.5;
a mass ratio of the pyraclostrobin to the sodium alginate is 1:2;
a mass ratio of the sodium alginate to the calcium carbonate is 3.9:1;
a molar ratio of the glacial acetic acid and the calcium carbonate is 3.5:1;
in the step f, a mass ratio of the liquid paraffin to the emulsifier is 9:1; and
a volume ratio of the oil phase to an aqueous phase is 6:1.
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