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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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TMP [dimethyl-4,4'-o-phenylenebis(3-thioallophanate)], benomyl, and MBC (methyl benzimid-azolecarbamate) residues were determined in citrus fruits (Table 8). A good cleanup method has been developed (100).
Citrus fruits were also the test materials in biphenyl residue analysis. The official AOAC method for determination of fungicide biphenyls in citrus fruits is based on steam distillation, TLC separation, and determination by UV spectrophotometry. Using a simpler method, biphenyls can be determined after extraction by UV absorbance on HPTLC plates. The reproducibility and specificity are comparable with that of the former method. The HPTLC silica gel plates gave better results when they were prewashed with methanol-chloroform (1:1) solution. Less diffuse and darker zones were observed when biphenyl was analyzed on conventional silica gel or on Cjg chemically bonded reversed-phase layers (101) (Table 8). The average percentage of recovery results ranged between 92% and 98%.
Rubigan residues were determined in cucumber and tomato samples (102), and sulfathiazoles were studied in honey using fluorescamine detection and densitometric evaluation (103) (Table 8).
Carbendazim, thiobendazole, imazalil, captafol, folpet, and chlorothalonil were extracted from tobacco and investigated by TLC. For visualization, fungi spores were applied (104) (Table 8). The best separation was performed when the first three compounds were developed with ethyl acetate-benzene and the others by a chloroform-hexane system (104) (Table 8).
Glyceollin isomers were separated on formamide-impregnated silica layers. The detection was carried out on the TLC plates under UV light at 285 nm (105).
Afugan (Pyrazophos), an organophosphorus-type fungicide, was determined in food samples of plant origin. The residues of afugan were detected by TLC under UV light after column cleanup using
Table 8 Fungicides
Compound Stationary phase Mobile phase
Captan Silica gel H CH2Cl2-hexane (9:1)
Folpet 0.1 M A1CI, (homemade)
Captafol Silica gel GF (Analtech)
Benomyl Silica gel F EtOAc
(Tokyo Kasei)
TPM
MBC
Biphenyl
Rubigan
(Phenarimol)
Sulfathiazole
Carbendazim
Thiabendazole
Imazalil
Captafol
Chlorothalonil
HP-KDF
HPTLC (Whatman) C,8RP Silica gel Silufol (Kavalier)
Silica gel
Silica gel
n-heptane [predevelopment] in MeOH-CHCl, (1:1)
Me0H-H20 (85: 15)
n-hexane-acetone (7:3) Benzene-EtOAc (7:3) Pentanol-CHCl, (9:1)
EtOAc-benzene (1:1)
CHCI,-hexane (1:1)
Rf x 100
36
57
42
50
26
Detection
NaCIO,
AgNO,, UV
UV
Densitometry
Fluorescamine Densitometry 32 Fungal species
Limit of detection (Mg)
50 (visual)
100
(densitometry)
Citrus fruits
0.25-2.5
(mg/kg)
Sample Ref.
Water 99
Lettuce
Apples
Citrus 100
fruits
Mandarins
Grapefruits
Oranges
Lemons
101
101
Cucumbers 102
Tomatoes
Honey 103
Tobacco 104
Glyceollin
isomers
Afugan
(Pyrazophos)
Formamide-impregnated silica gel Silica gel G (Merck)
Dinocap isomers Dinitro-octyl-phenol
Triforine
Kieselgel HF modified:
(1) Chloromethyl-methyl-
diethoxysilane
(2) Chloropropyl-methyl-
diethoxysilane
(3) Chloropropyl-methyl-
dichlorosilane Silufol (Kavalier)
Chavicol
Preparative TLC
Chavibetol
Allylpyrocatechol Silica gel 60 PF254
(Merck)
Chavibetol
acetate
Allyl-pyrocatechol
diacetate
l-phenyl-2-nitro-3- Silica gel impreganted
acetoxy-prop-l-ene with 5% paraffin oil
Ether-n-hexane (3:1) Hexane-acetone (8:1)
HzO-MeOH (1:3)
- (2:1) -Hexane-acetone (10:7) Acetone-CHCl, (5:95)
H20-Me0H (1:1)
Brestan
Brestanol
Du-Ter
CHCI,-acetone (85: 15)
UV 105
285 nm
50 UV 0.2 Apple 106
[mg/kg] Cucumber 106
Strawberry
(3)
43 Densitometry 107
83
AgNO,- 100 Water 19
NH4OH in acetone Soil
Phyihium 108
uliimum
Cladosprium
cucumerinum
UV 109
Ninhydrin
Densitometry at 510 nm
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