SEM/EDX analyses were performed using a Camscan series 2 scanning electron microscope connected to a Link AN 100000 energy dispersive X-ray analyzer. For automatic detection an automatic residue detection system
(ARDS), developed at this laboratory, was employed the details of which are given in reference 187. For manual operation the following conditions apply:
29 mm working distance 1-1.25 x 100 ^A emission x 1,000 magnification 25 kV accelerating voltage
0° tilt and resolution and absorbed current set according to the microscope on which the examination is carried out (absorbed current 1.84 A) Brightness/contrast set on iron particle until just visible on the backscat-
tered image Resolution set at spot size 3
Swab and Deldrin samples for SEM/EDX examination were subjected to a concentration/cleanup procedure, the apparatus for which is given in reference 185. All samples were carbon-coated using a Biorad E6430 automatic vacuum controller before examination in the SEM.
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