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Chromatographic scince series - Cazes J.

Cazes J. Chromatographic scince series - Marcel Dekker, 1996. - 1098 p.
ISBN 0-8247-9454-0
Download (direct link): сhromatography1996.pdf
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The adsorption of fluazifop-butyl and fluazifop was studied on two smectites by spectroscopic methods and TLC. The herbicides were extracted with acetone from Al-, Fe-, K-, and Cs-montmo-rillonites and saponites. Fractions were analyzed by TLC and compared with standards. In the extract, one phenolic breakdown product of fluazifop-butyl was also identified (Table 7) (85).
The main products of the metabolism of the postemergence herbicide diclofop-methyl were analyzed by means of TLC and mass spectrometry. Some ring hydroxylation occurred during the metabolism in wheat and wild oat samples (86).
New layers have been studied and introduced for the separation of 30 organic acids. For example, phenoxyacetic acid herbicide was separated from cinnamic, citric, gallic, maleic, oxalic acid, etc., on a calcium sulfate layer containing p-dimethyl-aminobenzaldehyde and developed with distilled water (87) (Table 7).
While chlorinated derivatives are potent herbicides, the structurally related alkyl-substituted phenoxyalkylcarboxylic acids have no pesticidal effect. These compounds are mentioned here because their chromatographic behavior is similar to that of these herbicides. Their separation was studied on reversed-phase TLC (RPTLC) plates having different lengths of carbon chains chemically bonded to silica layers using different mobile phases. This work could provide a possible means for chromatographic studies on their chlorinated derivatives (88) (Table 7).
R1: H, alkyl, metal
r2, r4; h, halogen
r3; halogen, 4-trifluoromethylpyridyloxy
(CH^COOR
XIX
Figure 6 Chlorophenoxyalkylcarboxylic acid herbicides, XIX.
Table 7 Chlorophenoxyalkylcarboxylic Acids
Compound Stationary phase Mobile phase Rf x 100
2,4-D (a) Silica gel G
(Analtech) impregnated with AgNO,
2.4-D methyl ester
2.4-D butyl ester (b) Alumina
2.4,5-T
MCPA
Silvex
Silvex methyl ester
Silvex i-octyl ester
2,4,5-T methyl ester
Fluazifop-butyl Silica gel 60
F254 (Merck)
(1-) (2-b) (3-a)
(1) Hexane-glacial acetic 54 3 52
acid-ether (72:30: 18)
67 39 78
(2) Cyclohexane-glacial 82 84
acetic acid (9:1)
(3) Benzene-glacial acetic 62 3 57
acid-acetone
(8:1:2)
61 58
68 63
53
66
Seven other systems EtOAc-n-hexane (1:1) 86
Limit of detection Detection (/xg)
AgN03, 0.5
densitometry
Sample
Natural and tap water
UV
Smectites (soil colloides)
Fluazifop
4-trifluoromethyl-2-pyridyloxyphenol
MCPA
p-chloro-o-cresol
5-chloro-3-methyl-catechol
Cinnamic acid
Citraconic acid Citric acid Gallic acid Maleic acid Nicotic acid Oxalic acid Phenoxyacetic acid
27 Alkylphenoxy propionic acids
Silica gel G CH2CI2
CaS04 impregnated with H20 dimethylaminobenz-aldehyde
Silufol (1) CHCl,-EtOAc (4:1)
RP-2 (2) 1-BuOH:ccNH4OH
(5:1)
RP-8 (3) Liquid paraffin
80% acetic acid
RP-18
10
64
9
10
90
90
100
100
65
GLC Grains, vegetables 16
Extraction by TLC
87
2,7-dichlorofluorescein 88
UV
Pesticides 783
784
Fodor-Csorba
4. Thiocarbamates
The utilization of thiocarbamate herbicides () has increased over the world. These nonpersistent herbicides control the annual grasses and the broad-leafed weeds.
Molinate is a selective herbicide that is applied in rice cultures against barnyard grass (Echinocloa spp.). The dissipation and degradation of l4C molinate in soil samples under nonflooded and flooded conditions was studied. Its dissipation seems much quicker from flooded soil than from moist soil, and only small amounts of breakdown products of molinate were observable under flooded conditions.
Molinate residues were extracted with dichloromethane or with methanol and/or acetone. The extract was investigated by TLC among other methods. Autoradiography, iodine vapor, and UV fluorescence quenching were the detection methods applied (89).
Triallate residues were analyzed in urine and body fluids after extraction with -hexane by chromatography on silica gel. Dragendorff s reagent or AgN03 detected the triallate residues with a sensitivity of 25 ng/50 ml urine. For quantitative determination, the extracts were treated with nicotinic acid and benzidine (90).
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