Most pesticide determinations are performed on silica gel TLC or
HPTLC commercially precoated plates. The layers almost always contain
a gypsum binder (designated as G layers) [2] or an organic binder. Silica
gel H layers [9] are especially hard and rugged and permit the use of high
concentrations of water in mobile phases without loss of adherence. Layers
often contain a fluorescent indicator or phosphor to facilitate detection of
compounds that absorb 254 nm UV light as dark zones on a fluorescent
background. These are termed F layers or F254 layers by the manufacturers.
Cellulose, alumina [10], and kieselguhr layers are also used occasionally
for pesticide TLC