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Recent Advances in


Page 119


NC 21314




Fig. 8. Oxidised (left) and reduced (right) forms of the acaricide

1 ~» CH,

eH, CH,


CH, eH,

Fig. 9. Degradation of amitraz on silica gel TLC plates.

3. Reduction/oxidation reactions:-
Reduction or oxidation reactions may take place on the silica surface.
This can be caused by the addition of potential metabolites which may
cause reduction of compounds in the plant or soil extract. For
example the addition of the potential metabolite NC 22505 to extracts
containing the radiolabelIed acaricide NC 21314 resulted in the
formation of radiolabelIed NC 22505 on the plate (Figure 8).

4. Instability on silica surface:-
Some compounds can decompose on the silica surface and it was found
that the breakdown of the compound amitraz during a purity determi-
nation was prevented by using concentration zone plates. On normal
silica surface degradation of the compound occurred. The proposed
scheme for the decomposition of this compound on silica gel is shown
in Figure 9.

Proposed scheme for the characterization by radio-thin layer chromatography
of pesticide metabolites

The radio-labelled extracts should be divided into two equal portions,
one portion admixed with non-radiolabelled potential metabolites. Each
portion is applied to the TLC plate separately as a narrow 1 cm band using
a mechanical applicator if possible. It is important to ensure that a
layer of sampIe is not accumulated above the silica layer as this will
cause streaking. The potential metabolites should be spotted separatelyon
the plate so that any oxidation or interconversion can be observed. The
plate is then developed in a sealed tank. The recovery of radioactivity
from the plate needs to be checked by plate scraping and scintillation
counting. If the potential metabolite is genuine then an isotopic dilution
effect will be observed and the radioactive component will be seen to fill
the whole of the ultraviolet quenched area. If the radioactivity does not
fill the whole area then it is possible that co-chromatography is taking
place. Additionally 2-D TLC can be used to confirm identity. Normally


Page 120

.:acb extract ought to be examined using a minimum cf two types of TLC plate
in separate solvent systems, with several being used in the method
developmellt stage.

Tlüll-layer chromatography is a powerful teehnique in ruetabolism
ehemistry and when used properly ean produee valid and aceurate results.


I would like to thank my eolleagues at Schering Agrochemieals in
particular Mr. D. Arnold, MI'. 1. Morton and Miss. S. Newby for their help
in the preparatioll of this paper.


1. S. U. Kahn, in: "Pestieides in the Soil Environment," Elsevier,
Amsterdam-:--p .114 (1980).

2. E. Stahl, "Thin Layer Chromatography - A Laboratory Handbook,"
Springer Verlag, Berlin (1965).

3. J. C. Touehstone, "Advanees in Thin Layer Chromatography Clinieal and
Environmelltal Applieations," John Wiley and Son, Chicbester (1982).

4. H. Filthuth, in: "Analytical and Chromatographie Techniques in Radio-
pharmaceutieal Chemistry," D. M. Wieland, M. C. Tobes, "md T. J.
Mangner, (eds.), Springer Verlag, New York, p. 79 (1986).


Page 237

Reversed-phase thin layer
chromatography (continued)

solvent-systems compared, 143
Rfs, 'held back', 109
RITA detector, 117

development, 118-119
Rosanilin, in fuchsin, 208
Rotation planar chromatography,

advantages/disadvantages, 53-54
column (C-RPC), 46
development modes, 49
micro chamber, compared with

ultra-micro chamber, 45-54
multi front effect,

characteristics, 53
normal chamber (N-RPC), 46
ROTACHROM separations, 49
rotation speed, 47-48
sequential (S-RPC), 46

Rubber compounding, ingredients, 231

Salicylic acid, 164, 166
Salts, concentrations,

effect on antibiotics, 215-221
PC variables, 220

application, specifications, 13
detectability, 15-18

Saponins, 190
separation, 191, 192

Schiff procedure for DNA, 207

one-dimensional, 77
two-dimensional, 77-86

Scanning densitometry, 12-26
error, sourees, 12-13
disadvantages, 37-38
fluorescence enhancement, 20-22
future developments, 22-26
performance characteristics, 15-18
sampIe application, 13
sampIe calibration, 18-20
sensitivity, and slit height, 16
Shimadzu CS-910, data, 17

Serine, 157

calibration curves, 70
derivatisation to amide, 69
formula, 68
similar compounds, 69

SERS, see Raman spectroscopy
SH-groups, reduction, 159
Silver nitrate multiphase TLC,

SIMS (surface ionization mass

spectrometry), 26
Size-exclusion chromatography, 21
Slit-scanning, see Scanning,
Sodium borohydride, 190
Sodium stannite, 190
Soil cores, extraction methods, 111


Solid phase extraction, 101-105
transfer deviees, 13

demixing, 62
list, and spot diameter, 183

Sorbents and modifiers,
bifunctional reagents, 163-170
hydrophilie modified preeoated,

influenee of stationary phase,

new sorbents, 139-150
normal/reversed phase ion-pairing,

optieal purity, control, 151
reversed phase pre-coated layers,

139, 140-144
Spark ehambers,

early, 77
problems, 120
see also: BERTA

Spectrophotometry, see Seanlling

diameters, various solvents, 183
positioning, minimizing error, 14
size, 13

relation between eoneentration
and response faetors, 73

2-D seanning, 85
Statie buildup,

effeet of drying time, 132
methods for elimination, 133

Stationary phases, range, 171
ion-pair reagents, 163-176

Stearie acid, 202
Storage of chromatographie

information, 33-34
Surface ionization teehniques, 26

see also: Raman speetroseopy
Surfactants, fluoreseenee quenehing,

Swine, residual tranquillizers,

Sylibum sp, 192
Sylimarin, 193

Tea, eompared with xanthine, 64
Tertatolol, radiolabelling studies,

Tetracene, FLN speetrum, 30, 31, 34,

Thalidomide, enantiomer, 152
Thebaine determination, 188
Thermal degradation, TLC., 114
Thin layer chromatography,

anticireular, 67-74
basic requirements, 1
bonded phases, 2-3
CIS bonded RP plates, 165
with Chiralplate, 151-160

Page 238

Thin layer chromatography

compared with GC, 159
densitometry, 187-199
detection and quantification, 5
development techniques, 4-5
enantiomeric separations, 154
flame ionisation, 201, 202
fluorescent indicator, 180
general principles, 1-7
high-performance, introduction,

mass spectrometry, 6
multiphase , 203
new sorbents, 139, 148
normal-phase, 2
normal and reversed-phase, ion-

pair, 163-170
normal vs reversed-phase, 112
optical-Purity control, 151-163
overpressure method, 5, 46, 52-53,

57-65, 215-221
plates, 2

buffer-memory for LC., 29
polar/non-polar surface

modifications, 148
problems and artefacts,

instability on silica surface,

reduction/oxidation reactions,

silica surface, instability, 115
thermal degradation, 114
volatilization, 114

reversed phase
bonded silicas, 2-3
ion-pairs, 163-170

silica gel plates, 167-169
paraffin coating, 165-167

silver nitrate multiphase, 201-205
surface-modified precoated

supports, 139
see also: Sorbents and modifiers

terminology, 11
see also: other names of specific

Thiurams, rubber curing, 231-235
Thyroxine, 157

enantiomer, 152
Titanous chloride assay, 207
Tobramycin, 215-221

structure, 218
TRACY detector, 117

development, 119-120
Tranquillizers, residues in swine,

Tridecanoic acid, 145
Triethanolamine, fluorescence

enhancement, 22
Triethylammonium proptne, 163-169
Trimethylammonium propane, 163-169

Tripropylammonium propane, 163-169
Triglycerides, 201-205

identification, 204
see also: fats, oils

Trition X-100, fluorescence
enhancement, 22

Tryptophan derivatives, 157
Two-dimensional chromatography,

evaluation, digital
autoradiography, 126

three-dimensional display, 129
Tyrosine, 157, 159

Urine, metabolie profiles, 87, 94
application, 90, 95, 97
overspotting, 90, 94

U-RPC (ultra-micro rotation
planar chromatography), 46-54

UV scanning, 69
UV-VIS spectrometry, 188

in situ, 196

Valine, 157
Valine diamide, 154
Van Urk's reagent, 197
Vanillin-hydrochlorhydric reagent,

Vanillin-methanolic solution, 191
Vidicon cameras, resolution, 24
Vitexine, 193
Volatilization, TLC, 114

Whole body frozen sections, 85

X-ray film, dynamic range, 113

offline, OPLC, 63
online, 64
radiolabelling studies, 102-105

Zinc DTC, 231, 235


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