Biomedical Engineering Reference
In-Depth Information
53.
Biosens Bioelectron
. 2005 Sep 15;
21(3):445-54. Epub 2004 Dec 21.
Semi disposable reactor
biosensors for detecting
carbamate pesticides in water.
Suwansa-ard S, Kanatharana P,
Asawatreratanakul P, Limsakul
C, Wongkittisuksa B,
Thavarungkul P. Biophysics
Research Unit: Biosensors and
Biocurrents, Prince of Songkla
University, Hat Yai, Songkhla
90112, Thailand.
Two flow-injection biosensor systems using a
semidisposable enzyme reactor have been developed
to determine carbamate pesticides in water samples.
Acetylcholinesterase was immobilized on silica gel
by covalent binding. pH and conductivity electrodes
were used to detect the ionic change of the sample
solution due to hydrolysis of acetylcholine.
Carbamate pesticides inhibited acetylcholinesterase,
and the decrease in the enzyme activity was used to
determine these pesticides. Parameters influencing
the performance of the systems were optimized to be
used in the inhibition procedure. Carbofuran and
carbaryl were used to test these systems. Detection
limits for the potentiometric and conductimetric
systems were both at 10% inhibition corresponding
to 0.02 and 0.3 ppm of carbofuran and carbaryl,
respectively. Both systems also provided the same
linear ranges, 0.02-8.0 ppm for carbofuran, and
0.3-10 ppm for carbaryl. The analysis of pesticides
was done a few times before the reactor was
disposed. Percentages of inhibition obtained from
different reactors were reproducible; therefore, no
recalibration was necessary when changing the
reactor. The biosensors were used to analyze carbaryl
in water samples from six wells in a vegetable-
growing area. Both systems could detect the presence
of carbaryl in the samples and provided good
recoveries of the added carbaryl, that is, 80%-106%
for the potentiometric system and 75%-105% for the
conductimetric system. The presence of carbaryl in
water samples analyzed by the biosensors was
confirmed by the gas chromatography-mass
spectrometric system. These biosensors do not
require any sample preconcentration and are suitable
for detecting pesticides in real water samples.
