Biosensors for pesticides - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 43

Polymer fibers

Lock in

Laser beam

Photo diodes

PC

Transducer

Flow cell
FIA system

Flow direction

Dye

Antibody
Antigen

Transducer with
immobilized
analyte derivative

Laser beam

FIGURE 2.10 Schematic diagram of the RIANA (adapted from [86]).

target molecules [85]. Barzen et al. [86] reported a prototype optical immunosen-
sor called RIver ANAlyser (RIANA). RIANA is based on a solid-phase fl uoroim-
munoassay that takes place at an optical transducer chip. The transducer surface was
chemically modifi ed with three analyte derivatives placed in different discrete loca-
tions. The transducer was mounted in a fl ow cell and passed a mixture of analyte and
fl uorescent dye (Cy5.5 dye) conjugated antibody after preincubation. The excitation
of bound fl uorescently labeled antibodies was accomplished using a collimated He-
Ne laser that was directly launched into the transducer. The collected light was subse-
quently fi ltered to avoid any collected pump radiation, and detected with photodiodes
(Fig. 2.10). The RIANA could be used for simultaneous detection of various pesti-
cides in one sample. Two sets of three different analytes (atrazine, alachlor, pentachlo-
rophenol and 2, 4-D, simazine, isoproturon) were detected successfully and the limit
of detection was comparable with single analyte immunoassay [86]. In another study
RIANA has also been employed for the simultaneous determination of three different
contaminants, atrazine, isoproturon, and estrone, present in real samples [87]. The lim-
its of detection for atrazine, isoproturon and estrone were 0.155, 0.046 and 0.084 ng
mL 1 , respectively. Propanil, a herbicide present in water, has also been quantifi ed
up to the subnanogram level (0.6 ng l 1 ) using RIANA, without any preconcentration
[88]. Mastichiadis et al. [89] reported a four band disposable optical capillary immu-
nosensor, which was capable of detecting pesticides such as mesotrione, paraquat,
diquat and hexaconazole with detection limits of 0.04, 0.06, 0.09 and 0.10 ng mL 1
and dynamic ranges up to 9, 6, 12 and 15 ng mL 1 , respectively.