Helvetica Chimica Acta ± Vol. 88 (2005)
1027
in
(
1
5ml), were diluted with 100 ml of H
HCl, were used, respectively. Absorbance measurements were performed on a Hitachi U-2001
spectrophotometer in a 1-cm quartz cell at r.t.
2
O. For hydrolysis and diazotisations, 2% aq. NaOH, and 0.3% NaNO
2
m
Coupling Reagents. All reagents 2 are commercially available (Aldrich or Fluka). They can also be readily
prepared by bromination of the corresponding anilines. General procedure for the synthesis of 2,6-dibromo-4-
methylbenzenamine (2a): To a soln. of 4-methylbenzeneamine (2 g) in 1:1 HCl/H
2
O (25ml), a soln. of Br
2
(2 ml) in AcOH (5ml) was added dropwise while stirring, the temp. being kept below 38 8. After 3 h, the
2
precipitate was filtered, washed with H O, and dried at 408 to afford 2a (80%). M.p. 75± 77 8. Compounds 2b and
2
c were prepared analogously, and recrystallized from aq. MeOH.
Sample Preparation. a) The fortified H O samples containing 0.4 ± 2.4 mg/ml of propoxur (Table 3) were
extracted with CHCl , the combined org. extracts were washed with 0.1m K CO soln. to break any emulsion
formed during the extraction, and dried (Na SO ). Finally, the solvent was evaporated, and the dry residue was
2
3
2
3
2
4
dissolved in MeOH from which the amount of insecticide was determined spectrophotometrically. b) In the case
of vegetables, 50 g of fresh vegetable or fruit was uniformly mixed with MeOH (10 ml) containing propoxur
(
10 mg), and left standing for 24 h. This material was extracted according to a procedure described in [9]. The
extracts were evaporated on a steam bath, and the residue was dissolved in MeOH and analyzed
spectrophotometrically. c) Agricultural wastewater samples (10 ml) were extracted with CHCl
3
(2 Â 10 ml).
The org. extract was evaporated to dryness at 51 Æ 68 under reduced pressure, the residue was dissolved in 50%
aq. MeOH (25ml), and suitable aliquots were analysed spectrophotometrically. d) Different soil samples (10 g)
were treated and analysed as outlined earlier [13].
General Procedure for the Determination of Propoxur. Propoxur test soln. (20 ml) was hydrolyzed for 5min
with 2% NaOH soln. (5ml) at r.t. The diazonium salts of compounds 2 were prepared by mixing a 0.3% soln. of
NaNO
2
(2 ml) with a 0.2% soln of 2 (4 ml) and 1m aq. HCl (2 ml). Coupling between diazotised 2 and the
hydrolysate at 08 yielded the chromophores 3.
REFERENCES
1] A. Ambrus, E. Hargitan, G. Karoly, A. Fulop, J. Lantos, J. Assoc. Off. Anal. Chem. 1981, 64, 743.
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3] H. A. Moye, J. Agric. Food Chem. 1975, 23, 415.
4] I. Fogy, E. R. Schmid, J. F. K. Huber, Z. Lebensm. Unters. Forsch. 1980, 170, 194.
5] K. M. Appaiah, O. P. Kapur, K. V. Nagaraja, J. Assoc. Off. Anal. Chem. 1983, 66, 105.
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8] G. Mukherjee, A. J. Mukherjee, B. R. Roy, J. Food Sci. Tech. 1975, 12, 96.
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[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
10] W. F. Vangils, Analyst 1979, 104, 1185.
11] C. S. P. Sastry, D. Vijaya, D. S. Mangala, Analyst 1987, 112, 75 .
12] D. Venkaiah, P. R. Naidu, Talanta 1990, 37, 629.
13] P. Venkateswarlu, V. Chandra Kumar, K. Seshaiah, Ind. J. Chem., Sect. B 1995, 34, 67.
14] V. Harikrishna, N. V. S. Naidur, Asian J. Chem. 2001, 13, 687.
15] P. Venkateswarlu, K. Seshaiah, Talanta 1994, 42, 73.
Received December 21, 2004