Development and validation of a rapid analytical method to quantify naled residue

A rapid gas chromatographic method for detecting residues of the thio-organophosphate naled was developed and subsequently validated in laboratory and field studies. More than 90% of naled was recovered by a gas chromatograph when equipped with a DB-5 capillary column and a thermionic specific detector. The limit of detection was 0.01 microg/ml with direct injection. Stabilization of naled under a variety of storage conditions also was examined. Analysis of field data showed that naled broke down rapidly in the environment but was stable when stored in hexane solvent at 4 degrees C and 23 degrees C for at least 7 days. Range of percentage matrix spike recovery was 31-49% for filter paper samples exposed under field conditions for 14 h. A field study was also initiated that collected naled droplets trapped on 6.7-m acrylic mohair-look yarn strands in addition to residue on filter paper after aerial ultra-low-volume mosquito adulticide application. Spike recovery was 79% for filter paper samples and 93% for yarn samples. Average naled residue concentrations with these methods were 373 microg/m2 and 11.28-73.77 microg/yarn, respectively.