Chemistry Reference
In-Depth Information
Guava leaves
extract
Acetate buffer
MC
Pump
Spectrometer
Waste
Waste
Iron solution
Recorder
Pump
Precipitate washing
solution
Figure 3.11
Flow injection manifold used for iron determination. Reproduced from [33] with permission from
Elsevier, © 2005.
N
O
CH
3
O
O
H
3
C
Scheme 3.6
CH
3
Propoxur.
3.2.4.4
A clean spectrometric method for the determination of propoxur
One of the most important carbamates which is widely used in agriculture is propoxur [2-(1-methylethoxy)
phenol methylcarbamate] (Scheme 3.6), but in addition to the insecticidal properties exhibited by this
compound, other biological effects have been reported.
Hence analytical methods have been developed for the determination of propoxur and its metabolites in
different matrices of the environment. Spectrophotometric method has been developed for the determination
of propoxur based on alkaline hydrolysis to yield 2-isopropoxyphenol followed by coupling with different
chemical reagents such as p-aminophenol (PAP). But one of the problems of such spectrophotometric
methods is that not only the compound to be determined is toxic but also the reagents employed have also
toxic effects. So photo-assisted catalytic procedures using TiO
2
illuminated with UV radiation appeared to be
very promising, efficient and economically viable that can be used to detoxify organic molecules. Flow
injection is widely used in analytical determinations because it provides better flexibility for carrying out
enormous chemical processes including on-line hydrolysis, derivatization, photochemical reactions, and
detoxification of organic molecules [34].
Green laboratory proposal
[35]
l of alkaline solutions of propoxur standards in
0.33 M NaOH or samples previously made alkaline, were directly injected into a carrier solution of 0.33 M
NaOH, at the same time a flow of a solution of 545
In actual practice 100
μ
g ml
-1
PAP and a 0.004 M KIO
4
solution were continuously
fed in. By using the 5-channel manifold shown in Figure 3.12, propoxur was determined spectrophotometrically
at 600 nm. After the measurement step, the waste was diluted with water and irradiated at 254 nm in order to
μ
