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be provided by the laboratory. The laboratory using the modification must validate the procedures before implementation. The validation data and 5. Puree Time report should be made available for review by all affected parties. If needed, the Department of Toxic Substances Control's(DTSC)Environmental EPA Method 8260B specifies a purge time of 11 minutes. Laboratories Chemistry Laboratory(ECL)should be consulted on modifications. should not deviate from this specification as the method has been optimized for the recovery of all target analytes. If modifications are needed,they B. EPA Method TO-15 should be documented and validated. Validation should be performed with vapor-phased standards. EPA Method TO-15(Determination of Volatile Organic Compounds(VOCs)in Air Collected in Specially-Prepared Canisters and Analyzed by Gas Chromatography/ • 6. Aulosamplers Mass Spectrometry(GGMS))is traditionally used to analyze for VOCs in ambient air samples(USEPA, 1999). Samples are collected into specially prepared stainless The utility of using an autosampler with modified EPA Method 826OB/C is steel canisters. VOCs in a known volume of sample are concentrated onto a solid questionable. This practice is not recommended since:there.will likely be sorbent trap,and refocused on a second trap before being thermally descrbed onto sample loss during the sample transfer as well as possible leakage from the the GC column for separation. vials during the sample run. In addition,the vials may sit in the autosampler for an extended period of time. There are two techniques for introducing whole air samples by TO-15 from the canister into the gas chromatograph:(1)mullisorbent pack method;and(2)a 7. Screenino concentrator where the VOCs are condensed on a reduced temperature surface (i.e,,cold trap). For the multisorbent pack method,there are different types of solid Laboratories should screen samples(e.g.,with GC/FID),where possible, sorbent trap available depending on the compounds of interest. Traps with different before analysis to avoid saturation of the mass spectrometer. This will also type of sorbent packing have different retentive properties which can be used to provide information on the proper dilution(s)needed for quantification. selectively concentrate analytes of interest. 8. Data Review Laboratories employing EPA Method TO-15 to analyze soil gas samples should -- - adhere to all the basic requirements of the method including calibration and QA/QC Soil gas data generated with EPA Method 82608 should be reviewed in detail protocols.Method TO-15 is best suited for soil gas analysis since it is designed for to ensure that all QA/QC parameters are within specified control limits before gas samples. However,there are other modifications referred to as TO-15,which they are to beusi.for risk assessments/management or other critical are described in Table 3. The advantages and disadvantages of these modifications decision making purposes. are summarized below. Note that some of the modifications are not in technical compliance with the method. 9. Applicability Table F-3: Advantages and Disadvantages of Modifications • Modified Method 8260B works well for soil gas samaples with high MMlfletabn Haeme obeaama con ommis concentrations of VOC(i.e., >0.1 pg/L or 100 pglm)and for most samplas eolmcmd m . L.cos, slgnr m beckgeuM loeyasl. N«recommencen. compounds. However,this method may not be ideal for more polar/water Tomas bags. • Easty oanapmed. • Msaprom of some campounas. • Tectemelynot-m is • Selmpu • Bagstlenotngi fteteT6hounitoed. Soluble compounds and soil gas samples with lower concentrations of VOC wmpeunaa nava Lmlua hoaktq Wne as-3s be,n l« (i.e.,<0.1 pg/L or 100 pg/m). Samples with constituent concentrations lower beenshae'am be mon campemWsl. «°ble m than 0.l pglL and/or with polar/water soluble compounds should be confirmed sample:mlomemm° coca/«highly umitw volume can be anslVea N.5-5 N«recommtmdee. by Method TO-15. mslmn m by ming cosated al. sample collacuen IanJecuon leap aadh samples. N«whoa r«loxwosommW, raNNVoedoesn«campry samples. aft TO 15's 10. Other Modifications usedpamablecertas Idealre.nea Mayor be auto to l«nme Has earlems • conslderedmtean system(e.g..Harass) wrsening. typesorsamptltgmeNa.samples have 'supernatant-gas m bs mnsremetl I«analyns Ia.g., daomatogaph under Any other modifications not mentioned in this guidance should be reviewed by cants/«.o a e«rem«'ba section 1.e of m«hod. all parties involved prior to being put to use for project. The standard Nedmem,zone P e 9 P P J r msc Emiaommemal cbemNry Lob«stay/Ecu shoos be aonaueea operating procedures(SOP)for the sample preparation and analysis should 12110/2009 -75- 12/10/2009 _76-