Two‐Stage Fractionation of a Mixture of 10 Pesticides by TLC and HPLC

Abstract

Relationships between R F values and mobile‐phase composition have been determined for 10 pesticides in normal‐phase (NP) systems, which have enabled choosing optimum systems for preliminary fractionation of the multicomponent mixture of pesticides by zonal micropreparative thin‐layer chromatography (TLC). The 10‐component mixture was applied from the edge of the silica layer and developed with ethyl acetate–diisopropyl ether (10∶90, v/v). The zones were detected in UV light at λ = 254 nm. The separated eight simpler fractions were applied to an octadecyl silica layer wettable with water (TLC, RP‐18W) and rechromatographed. The separated eight simpler fractions were also applied to a cyanopropyl‐bonded silica layer and developed with (NP) and reverse‐phase (RP) systems. The plates were scanned and videoscanned, furnishing real pictures of the plates showing complete separation of the fractions on the RP‐18W plate with the RP and NP systems on cyanopropyl silica layer. The simpler fractions were also separated on a cyanopropyl and octadecyl silica high performance liquid chromatography (HPLC) columns. Preparative separation of the complex mixture by TLC on silica (non‐aqueous eluent, NP system), combined with TLC or/and HPLC (aqueous eluent, RP system) or HPLC (NP system), gives a good perspective of full separation of the simpler fractions in the second stage, by using the two methods with the possibility of full quantitative TLC and HPLC analysis.