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� 4 <br /> i <br /> 2 . 2 METHOD SPECIFIC <br /> SAMPLING INSTRUCTIONS <br /> I <br /> Although the method suggests sampling volumes of 1 and 4 L,there is considerable <br /> mention of calculating a safe sampling volume. The sampling volume you select should <br /> include consideration of both the desired final reporting limit d the safe sampli'n'j'A <br /> volume of the sorbent being used (sce Section 2.1) The thought process is outlined <br /> pbelow. <br /> ,1 Determine the Final Reporting Limit for the T rget Compound: the concentration <br /> 1L\�� may be a risk-based action level or EPA preliminary remediation goal (PRG). <br /> 4o Determine the Method Reporting Limit: the mass value is provided by the laboratory <br /> and is based on the analytical method selected and the sensitivity of the <br /> instrumentation. The method reporting limit may vary for each target compound. <br /> r, Calculate the Sampling Volume: use the equation on page 6 of this guide to determine <br /> p( � the volume of air sample that must be drawn through the sorbent in order to achieve <br /> the final reporting limit. <br /> lr' Compare the Sampling Volume to the SS�Re r to table: of afe sampling volume <br /> (SSV) for the sorbent being used— (e.g.,Table and Appendix 1 in Method TO-17). <br /> O� If the SSV for the compound of interest is not available,use the SSV of a compound <br /> in the same class (e.g., toluene for xylene, chlor form for carbon tetrachloride, etc.) <br /> and ensure that the compound will not breakt ough when sampling the volume ; <br /> r> 1�AV calculated using the equation above. If breakthrough is a possibility, select a sorbent i <br /> with greater sorbent strength'(i.c-"surface area) <br /> ( To illustrate the thought process,an example is provide below: 2 <br /> � I <br /> 1. Assume Benzene is the target compound and must be reported at a final reporting limit of <br /> 0.0005 ug/L. n r 0 <br /> 2. The laboratory provides a method reporting limit o 10 ng (0.010 ug). <br /> 3. Using Equation 3,the sampling volume = 0.010/0.0005 = 20 L. <br /> 11 J✓'"U>` 4. TO-17 Appendix 1 shows that for Benzene,a SSV of up to 26 L can be collected using a <br /> Type 3 (CarboTrap 300) multi-sorbent tube. <br /> b In this example,Benzene can theoretically be reported ot a final reporting limit of 0.0005 ug/L <br /> 1! with a sampling volume of 20 L. <br /> sa <br /> 19 <br />