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    Controlled release of aldicarb from carboxymethyl cellulose microspheres: in vitro and field applications
    (John Wiley & Sons Ltd, 1999) Kok, FN; Arica, MY; Gencer, O; Abak, K; Hasirci, V
    Aldicarb is a carbamate pesticide that is widely used throughout the world in the protection Of crops (eg cotton, nuts, potatoes, onion, tobacco, sugar beet and sugar cane). In Turkey, especially in the Cukurova region, it is used for the control of the cotton white fly (Bemisia tabaci) which attacks cotton plants cultivated in this region. Aldicarb contamination in surface and ground water is a serious problem in several countries, partly due to its high water solubility. It is also highly toxic to mammals. In order to overcome these problems, microspheres of aldicarb were prepared using carboxymethyl cellulose (CMC) as the biodegradable support material cross-linked with aluminium chloride. A strong hysteresis behaviour was observed upon drying and reswelling. Encapsulation efficiency was in the range 12-23% and aldicarb contents of 5.7-10.3 mg per 100mg of microspheres was achieved. In vitro release was distinctly Fickian, and Higuchi constants were very close to 0.5. Release in pots revealed that only one sample had a release capability for more than four weeks. In the cotton plot much longer durations of release (more than seven weeks) were observed while a commercial granular formulation released its content immediately. It was thus possible to construct a controlled pesticide release system that prolonged the bioavailability to about eight weeks. (C) 1999 Society of Chemical Industry.
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    Controlled release of Aldicarb from carboxymethylcellulose microcapsules
    (Scientific Technical Research Council Turkey, 1997) Arica, MY; Yigitoglu, M; Lale, M; Kok, FN; Hasirci, V
    Sodium carboxymethyl cellulose was converted into microspheres by crosslinking with aluminum chloride. Various microsheres with different amounts of crosslinker, biopolymer of various concentrations and molecular weights, and with different pesticide (Aldicarb) contents and pesticide to polymer ratios were prepared. The pesticide encapsulation efficiencies and aldicarb release kinetics of the resultant microcapsules were investigated. It was possible to modify the release behaviour by varying the above parameters and to have drug release with half-lives longer than 100 hours in aqueous media. The release kinetics were described by first order and zero order kinetics.
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    Controlled release of aldicarb from lignin loaded ionotropic hydrogel microspheres
    (Taylor & Francis Ltd, 1999) Kok, FN; Wilkins, RM; Cain, RB; Arica, MY; Alaeddinoglu, G; Hasirci, V
    Aldicarb loaded microspheres of carboxymethyl cellulose, CMC, of various compositions were prepared with the crosslinking action of AI(III). Into these microspheres, lignin was introduced as a filler to further regulate the rate of release. The encapsulation efficiency was low (4.15-13.00%) due to the high water solubility of aldicarb. Release into aqueous media was quite rapid and almost complete within 24h. Initial stages of the release (60% of AS released) was investigated to determine the release mechanism and it was found that release from the microspheres was governed by Fickian diffusion. Among the various parameters, the ratio of lignin to CMC and aldicarb to CMC were found to be influential on the rate of release from the crosslinked CMC-lignin microspheres. The soil behaviour confirmed the delayed release effect of the controlled release formulation compared to Temik (a commercial preparation of aldicarb), especially when lignin was incorporated.