Methodological hints on the gas chromatographic determination of kelevan and kepone in potatoes, potato foliage and soil]

The gas chromatographic determination of Kelevan, an ethyllaevulinic acid derivative of Kepone, requires its conversion to Kepone. Thermal decomposition in the injection block of the gas chromatograph at 45 degrees C. has proved to be well suited for routine work. The sample is extracted with acetonitrile; the extract is purified and concentrated under reduced pressure. The separation of Kelevan from Kepone already metabolically produced is possible by column chromatography (silica gel; elution with benzene and 5% acetone in benzene). The determination of pre-existent Kepone and of Kelevan (after thermal conversion to Kepone) was achieved by means of a Pye-Unicam gas chromatograph. The limits of detection are 0.002 p.p.m. for Kepone, and 0.003 p.p.m. for Kelevan. The recovery of Kelevan and Kepone added to control samples (for every 10 determinations with different amounts added to potatoes, potato foliage and soil samples) ranges from 63 to 88%; the standard derivation, from +/- 1.7 to 7.3%.