The lambda-cyhalothrin microcapsule release kinetics study was
performed using the dialysis bag method. The purchased dialysis bags
(cutoff molecular weight: 8000–14,000) were cut into small
sections of about 5 cm for pretreatment. An accurately weighed sample
(6.5% lambda-cyhalothrin microcapsule suspension) of 1.0 g was placed
in the dialysis bag, which was immersed in a conical flask containing
50 mL of 50% acetonitrile aqueous solution (v/v) and placed in a 25
± 2 °C double-shaking incubator at 100 rpm for release tests.
An equal amount (1 mL) of media outside the dialysis bag was collected
at different time intervals and supplemented with 1 mL of 50% acetonitrile
aqueous solution, maintaining the volume of the release medium at
50 mL at all times. The sampled solution was passed through an organic
phase microporous filter membrane with a pore size of 0.22 μm.
The content of lambda-cyhalothrin in the filtrate was determined by
HPLC. The cumulative amount of lambda-cyhalothrin released was the
value for lambda-cyhalothrin from the measurement results.
The
cumulative release of lambda-cyhalothrin was calculated by the followingeq 4
Here, Ct represents
the concentration of lambda-cyhalothrin in the time t release medium, mt-act represents the cumulative release of lambda-cyhalothrin
at time t, v represents the volume
of the release medium taken out each time (1 mL in this experiment),
and V represents the total volume of the release
medium (50 mL in this experiment).
The cumulative release curves
of the microcapsules were fitted
with the following mathematical models:
(1) Zero order release
model39 (link) where Qt is the release amount of active ingredient at time t, Q0 is the
amount of active ingredient in the release medium, and k0 is the release constant.
(2) First-order release
model40 (link) where Qt is the release amount of active ingredient at time t, Q0 is the initial amount
of active ingredient in the microcapsule sample, and k is the release constant.
(3) Higuchi release model41 (link) where Qt is the release amount of active ingredient at time t, Q0 is the amount of active
ingredient in the release medium, and kH is the release constant.
(4) Ritger–Peppas model42 (link) where Mt is the release amount of active components per unit time t, M∞ is the total amount
of active components in the microcapsule, k is the
release constant, n is the diffusion index, and t is the release time.
performed using the dialysis bag method. The purchased dialysis bags
(cutoff molecular weight: 8000–14,000) were cut into small
sections of about 5 cm for pretreatment. An accurately weighed sample
(6.5% lambda-cyhalothrin microcapsule suspension) of 1.0 g was placed
in the dialysis bag, which was immersed in a conical flask containing
50 mL of 50% acetonitrile aqueous solution (v/v) and placed in a 25
± 2 °C double-shaking incubator at 100 rpm for release tests.
An equal amount (1 mL) of media outside the dialysis bag was collected
at different time intervals and supplemented with 1 mL of 50% acetonitrile
aqueous solution, maintaining the volume of the release medium at
50 mL at all times. The sampled solution was passed through an organic
phase microporous filter membrane with a pore size of 0.22 μm.
The content of lambda-cyhalothrin in the filtrate was determined by
HPLC. The cumulative amount of lambda-cyhalothrin released was the
value for lambda-cyhalothrin from the measurement results.
The
cumulative release of lambda-cyhalothrin was calculated by the following
Here, Ct represents
the concentration of lambda-cyhalothrin in the time t release medium, mt-act represents the cumulative release of lambda-cyhalothrin
at time t, v represents the volume
of the release medium taken out each time (1 mL in this experiment),
and V represents the total volume of the release
medium (50 mL in this experiment).
The cumulative release curves
of the microcapsules were fitted
with the following mathematical models:
(1) Zero order release
model39 (link) where Qt is the release amount of active ingredient at time t, Q0 is the
amount of active ingredient in the release medium, and k0 is the release constant.
(2) First-order release
model40 (link) where Qt is the release amount of active ingredient at time t, Q0 is the initial amount
of active ingredient in the microcapsule sample, and k is the release constant.
(3) Higuchi release model41 (link) where Qt is the release amount of active ingredient at time t, Q0 is the amount of active
ingredient in the release medium, and kH is the release constant.
(4) Ritger–Peppas model42 (link) where Mt is the release amount of active components per unit time t, M∞ is the total amount
of active components in the microcapsule, k is the
release constant, n is the diffusion index, and t is the release time.
