A modified extraction and clean-up procedure for the detection and determination of parathion-methyl and chlorpyrifos residues in tea.
Recent advances in methodology and instrumentation have made possible the detection and determination of pesticides at microgram kg-1 (ppb) levels. The sensitivity of a method of analysis depends greatly on the efficient extraction of the pesticide and the subsequent clean-up of the extract. The extract from green tea leaves is a mixture of aroma components, polyphenols and caffeine. The preparation of made tea from green tea leaves adds to this complexity by concentrating these coextractives. Conventional clean-up techniques provide poor recoveries for parathion-methyl and chlorpyrifos from both green tea leaves and made tea. This arises from interference by caffeine during gas chromatography, as it has a similar retention time to the two pesticides and peaks overlap. A modification to the protocol based on a solvent partitioning process using dichloromethane and subsequent washing of the extracts with warm water removed the caffeine, and pigments were removed by column chromatography. Recoveries ranging from 80 to 90% were then obtained for both pesticides.
Shanker
A
A
Hill Area Tea Science Division, Institute of Himalayan Bioresource Technology (CSIR), Palampur-176-061, Himachal Pradesh, India. directors@csihbt.ren.nic.in
Sood
C
C
Kumar
V
V
Ravindranath
S D
SD
D002110:Caffeine / Q000302:isolation & purification; D004390:Chlorpyrifos / Q000032:analysis*; D002849:Chromatography, Gas / Q000379:methods*; D007306:Insecticides / Q000032:analysis*; D008743:Methyl Parathion / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis*; D010860:Pigments, Biological / Q000302:isolation & purification; D018515:Plant Leaves / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D013662:Tea / Q000737:chemistry*
D007306:Insecticides; D010573:Pesticide Residues; D010860:Pigments, Biological; D013662:Tea; D002110:Caffeine; D008743:Methyl Parathion; D004390:Chlorpyrifos