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International Journal of Environmentally Conscious Design & Manufacturing 

Volume 10, Number 1, 2001 - 2002

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Contents
Contents

Organic Phase Biosensor for Detection of Pesticides, by E.S. Wilkins, P. 1

    The goal of this project is to develop a rapid, simple, and sensitive acetylcholinesterase
(AChE) biosensor for direct measurement of organophosphorus compounds (OPCs) in
organic solvent. This will allow adapting the biosensor for detection of pesticides in actual
water samples, avoiding the procedures of evaporation and resolution. The effort focused on
two bioanalytical systems: a) Potentiometric OPCs biosensor based on bioelectrocatalytic
(mediatorless) transduction; and b) Amperometric OPCs biosensor based on thiocholinehexacyanoferrate
reaction. OPCs biosensor based on bioelectrocatalytic (mediatorless)
transduction employs a multi-enzyme system arranged in the form of a disposable miniature
electrode. The three enzymes: peroxidase, choline oxidase and choline esterase are coimmobilized
at the screen-printed carbon electrode. The prototype electrode is
manufactured by screen-printing technology allowing mass fabrication of the sensing
elements with good reproducibility. An amperometric acetylcholinesterase biosensor for the
analysis of OPCs in pure organic solvents is based on the thiocholine-hexacyanoferrate
reaction. The enzyme (AChE) was co-immobilized with an electron mediator, Prussian Blue,
on the surface of a graphite electrode. The effect of organic solvents on acetylcholinesterase
activity was estimated in the presence of polar (hydrophilic) and non-polar (hydrophobic)
organic solvents in the range of 0.01-100%. The ability of the AChE biosensors to assay
pesticides was demonstrated by quantitative determination of dichlorvos, fenthion,
trichlorfon and diazinon in ethanol. The assay allows determination of OPCs in submicromolar
concentration ranges with an overall assay time of 10 minutes. The sensing
elements of the potentiometric and amperometric AChE biosensors can be stored in dry
state for more than 2 months without any loss of the activity. The AChE biosensors possess
distinct advantages, including monitoring of hydrophobic substrates, elimination of
microbial contamination, enhanced thermostability, and relative ease of enzyme
immobilization. Potential application areas include: laboratory screening, food analysis,
environmental monitoring. The biosensors are also useful in military situations when the use
of chemical warfare agents is expected.

Optimal Parts Allocation for Minimizing Assembly and Disassembly Times of Threaded Fasteners, by Y. Kondo, Y-I Hayashi, M. Naitoh, and F. Obata, P. 15

    Optimal parts allocation allowing easy assembly and disassembly of threaded fasteners was
experimentally examined. Two types of fasteners are considered; bolt type and bolt-nut type.
The assembly and disassembly times are more affected by the gap L, the distance from the
lateral surface of test piece to the barrier, than the holding angle of test piece. The assembly
and disassembly times increased with decrease of gap L. The suitable holding angle for
minimizing the assembly and disassembly times is 0° in the bolt-type and 90° in the bolt-nut
type, respectively. The tall barrier height and the holding angle of 180° make work efficiency
worse. The “difficult-to-work” region, where the assembly and disassembly times increased
exponentially with decrease of gap L, are emerged independent of gap L, holding angle α
and the kind of joining method. There are three dominant factors in emergence of “difficult-
to-work” region; (1) poor visibility, (2)unusual work posture and (3) insufficient work apace.

Lignin as Adsorbent and Detoxicant, by P. Zuman and E. Rupp, P. 23

    All studied pesticides are adsorbed on lignin. The bioavailability of the pesticide depends on
the adsorption equilibrium and the rate of its establishment. Adsorption isotherms in
equilibrated solutions depend on the structure of the pesticide, the nature of lignin, the pH
and the ionic strength. To mimic conditions in nature a dynamic method has been developed
based on chromatography on a lignin column. This enabled an estimation of the rates of
adsorption and desorption, which are strongly dependent on the nature of the pesticide.
Lignin adsorbs cations like Cu2+, Zn2+, Pb2+ and U02+
2 and can be used for remediation.
Toxic materials, both inorganic and organic, can be accumulated on lignin, which is cheap,
further decomposed, or further concentrated by burning or alkaline cleavage of lignin.