Pesticide immobilization

Pesticides Immobilized choline oxidase/peroxidase, luminol-H202 CL 4 pg/L aldicarb 0.75 pg/L paraoxon 55... 

Substances other than enzymes can be immobilized. Examples include the fixing of heparin on polytetrafluoroethylene with the aid of PEI (424), the controUed release of pesticides which are bound to PEI (425), and the inhibition of herbicide suspensions by addition of PEI (426). The uptake of anionic dyes by fabric or paper is improved if the paper is first catonized with PEI (427). In addition, PEI is able to absorb odorizing substances such as fatty acids and aldehydes. Because of its high molecular weight, PEI can be used in cosmetics and body care products, as weU as in industrial elimination of odors, such as the improvement of ambient air quaHty in sewage treatment plants (428). 

Durand P, Nicaud JM, Mallevialle J. 1984. Detection of organophosphorus pesticides with an immobilized cholinesterase electrode. J Anal Toxicol 8 112-117. 

The relative immobility of the chlorodioxins is expected, based on the very low solubility of these compounds in water (0.6 / g/liter). In contrast, the herbicide, 2,4,5-T, is relatively mobile in sandy soils, but movement decreases as soil organic matter increases. What does this information tell us, and how does it compare with other organic compounds A mobility scale has been devised for a large number of pesticides (3). Higher mobility numbers reflect increased compound mobility in soils. The dioxins would be in Class 1—i.e., they are immobile in soils and would compare with several chlorinated hydrocarbon insecticides. 

The design and implementation of a portable fiber-optic cholinesterase biosensor for the detection and determination of pesticides carbaryl and dichlorvos was presented by Andreou81. The sensing bioactive material was a three-layer sandwich. The enzyme cholinesterase was immobilized on the outer layer, consisting of hydrophilic modified polyvinylidenefluoride membrane. The membrane was in contact with an intermediate sol-gel layer that incorporated bromocresol purple, deposited on an inner disk. The sensor operated in a static mode at room temperature and the rate of the inhibited reaction served as an analytical signal. This method was successfully applied to the direct analysis of natural water samples (detection and determination of these pesticides), without sample pretreatment, and since the biosensor setup is fully portable (in a small case), it is suitable for in-field use. 

Andreou V., Clonis Y., A portable fiber-optic pesticide biosensor based on immobilized cholinesterase and sol-gel entrapped bromocresol purple for in-field use, Biosens. Bioelectr. 2002 17 61-69. 

Immobilization methods used in pesticide biosensors design... 

In view of the conductive and electrocatalytic features of carbon nanotubes (CNTs), AChE and choline oxidases (COx) have been covalently coimmobilized on multiwall carbon nanotubes (MWNTs) for the preparation of an organophosphorus pesticide (OP) biosensor [40, 41], Another OP biosensor has also been constructed by adsorption of AChE on MWNTs modified thick film [8], More recently AChE has been covalently linked with MWNTs doped glutaraldehyde cross-linked chitosan composite film [11], in which biopolymer chitosan provides biocompatible nature to the enzyme and MWNTs improve the conductive nature of chitosan. Even though these enzyme immobilization techniques have been reported in the last three decades, no method can be commonly used for all the enzymes by retaining their complete activity. 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

S. Andreescu, V. Magearu, A. Lougarre, D. Fournier, and J.L. Marty, Immobilization of enzymes on screen-printed sensors via a histidine tail. Application to the detection of pesticides using modified cholinesterase. Anal. Lett. 34, 529-540 (2001). 

M.N. Hendji, N. Jaffrezic-Renault, C. Martelet, P. Clechet, A.A. Shulga, V.I. Strikha, L.I. Netchipruk, A.P. Soldatkin, and W.B. Wlodarski, Sensitive detection of pesticides using a differential ISFET-based system with immobilized cholinesterases. Anal. Chim. Acta 281, 3—11 (1993). 

R. Kindervater, W. Kiinnecke, and R.D. Schimid, Exchangeable immobilized enzyme reactor for enzyme inhibition tests in flow-injection analysis using a magnetic device. Determination of pesticides in drinking water. Anal. Chim. Acta 234, 113-117 (1990). 

K.C. Gulla, M.D. Gouda, M.S. Thakur, and N.G. Karanth, Reactivation of immobilized acetyl cholinesterase in an amperometric biosensor for organophosphorus pesticide. Biochim. Biophys. Acta... 

A. Vakurov, C.E. Simpson, C.L. Daly, T.D. Gibson, and P.A. Millner, Acetylcholinesterase-based biosensor electrodes for organophosphate pesticide detection I. Modification of carbon surface for immobilization of acetylcholinesterase. Biosens. Bioelectron. 20, 1118-1125 (2004). 

A.A. Ciucu, C. Negulescu, and R.P. Baldwin, Detection of pesticides using an amperometric biosensor based on ferophthalocyanine chemically modified carbon paste electrode and immobilized bienzymatic system. Biosens. Bioelectron. 18, 303-310 (2003). 

Other enzymes have also been immobilized on CNTs for the construction of electrochemical biosensors. Deo et al. [115] have described an amperometric biosensor for organophosphorus (OP) pesticides based on a CNT-modified transducer and OP hydrolase, which is used to measure as low as 0.15 pM paraoxon and 0.8 pM parathion with... 

Figure 3 Example of a typical luminescent flow sensing device [manifold for pesticide chemiluminescent flow assay with one (A) or two (B) columns using immobilized enzymes]. A = immobilized dehydrogenase (Phe-DH) 1.0 m coil B = immobilized biolumi-...

The above-mentioned system has also been used for the indirect CL determination of some carbamate and organophosphorous pesticides that inhibit acetylcholinesterase. Acetylcholinesterase in solution or immobilized on methacrylate beads is coupled to immobilized choline oxidase and peroxidase [46],... 

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