COMPOUND-INDEPENDENT ELEMENTAL QUANTITAT

2.1 A measured volume or weight of sample (liquid, solid, or other) is extracted using the appropriate matrix-specific sample extraction technique. 2.2 Liquid samples may be extracted at neutral pH with methylene chloride using either Method 3510 (separatory funnel), Method 3520 (continuous liquid-liquid extractor), or other appropriate technique. Acid herbicides should be extracted and processed by Method 8151 or other appropriate technique. 2.3 Solid samples to be analyzed for neutral compounds may be extracted with hexaneacetone (1:1) or methylene chloride-acetone (1:1) using Method 3540 (Soxhlet), Method 3541 (automated Soxhlet), Method 3545 (pressurized fluid extraction), Method 3546 (microwave extraction), Method 3550 (ultrasonic extraction), or other appropriate technique. Acid herbicides should be extracted and processed by Method 8151 or other appropriate technique. 2.4 If the sample is to be screened for both neutral pesticides and herbicide acids, the extracts may be combined following methyl ester/ether derivatization and solvent exchange of the herbicide fraction. NOTE: Combining the acid herbicide and neutral pesticide fractions is not generally recommended. 2.5 The extract is analyzed by injecting a measured aliquot (usually 1 to 5-µL) into a gas chromatograph equipped with a fused-silica capillary column and an atomic emission detector (GC/AED). The AED uses a microwave-induced helium plasma to generate temperatures in the