A dehydrochlorinase-based pH change assay for determination of DDT in sprayed surfaces.
A glutathione S-transferase (GST) from the mosquito Aedes aegypti (aagste2), selected in the field as a major metabolic resistance enzyme for this parasite vector, was employed to produce a highly specific assay for the determination of DDT [1,1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene]. Detection is based on the pH change occurring in an appropriate buffer system by the concomitant release of H(+) during the aagste2-catalyzed dehydrochlorination reaction and is monitored potentiometrically or colorimetrically in the presence of a pH marker. The theoretical limit of detection (LOD) of the assay is 3.8 microg/ml, and the linear range of quantification is 12 to 250 microg/ml. The method does not recognize biologically inactive DDT analogues or major DDT photodegradants and breakdown molecules, and it is highly specific for the insecticidal p.p'DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane]. The biosensor was validated with a number of insecticide swabs from DDT-sprayed surfaces and found to be reproducible and reliable as compared with high-performance liquid chromatography (HPLC) (correlation coefficient R(2)=0.98). Given the current expansion of DDT residual sprayings in many regions of Africa as a key strategic intervention for malaria vector control, this simple assay to monitor DDT levels for vector control spraying programs could have an important impact on malaria control.
Morou
Evangelia
E
Vector Research, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK.
Ismail
Hanafy M
HM
Dowd
Andrew J
AJ
Hemingway
Janet
J
Labrou
Nikos
N
Paine
Mark
M
Vontas
John
J
D003634:DDT / Q000032:analysis* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008190:Lyases / Q000378:metabolism*; D011199:Potentiometry; D012680:Sensitivity and Specificity; D013379:Substrate Specificity; D013499:Surface Properties
D003634:DDT; D008190:Lyases; C019990:DDT-dehydrochlorinase