6.2 Laboratory Processing
6.2.1 Volatile Organic Compounds
ISM for VOCs uses a methanol preservation technique when collecting increments.
ISM samples to be analyzed for any VOCs are collected using methanol field preservation.
Refer to Section 5.4.1 for additional details on the field collection of VOC samples and precautions (hazardous material handling and shipping) for methanol field preservation. Collection is based on the high-concentration method described in Sections 2.2 and 8.2.2 of USEPA SW-846 Method 5035A (USEPA 2002c), with a minor modification to the sample container (bottle) to accommodate the increased number of increments (soil mass) and methanol volume per ISM sample. Typically, a coring device (see Figure 5-12) and larger narrow-mouthed amber bottles (500–1000 mL) with Teflon-lined caps (see Figure 5-11) are required for ISM VOC sampling. Close coordination with the analytical laboratory regarding ISM VOC bottle/preservation requirements, sample kit preparation, sample receipt requirements, etc. is essential.
Additionally, a separate, unpreserved soil sample for percent moisture determination should be collected, if necessary, to report the ISM VOC results on a dry-weight basis. Typically, the unpreserved soil sample should be collected in the same manner as the ISM VOC samples, e.g., a second increment collected at each ISM increment location, placed in an unpreserved wide-mouth container (4 ounces or larger), and submitted to the laboratory.
The following equipment and information are necessary for laboratory processing and analysis of ISM VOC samples.
- The bottle tare weight (including sample label) and volume of methanol must be documented to back-calculate the soil mass in the submitted ISM VOC sample. The density of methanol (0.7918 g/cm3) should be used for the calculation.
- The laboratory must have an analytical balance capable of weighing the ISM VOC sample as received.
- A separate, unpreserved soil sample, collected in the same manner as the preserved ISM VOC sample, should be submitted for percent moisture determination.
- If required, total volume and moisture correction should be performed by the laboratory for final contaminant concentration reporting, per Section 11.10.5 of USEPA SW-846 Method 8000C.
Analysis of the methanol extract should proceed according to USEPA SW-846 Method 5035A and the applicable analytical method for VOCs (e.g., USEPA SW-846 Method 8021B, 8260C, etc.).