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Air <br /> 1 TOWCS LTD. <br /> AN ENVIRONMENTAL ANALYTICAL LABORATORY <br /> LABORATORY NARRATIVE <br /> Modified TO-3 <br /> AECOM Environment <br /> Workorder#0901186 <br /> Two 1 Liter Tedlar Bag samples were received on January 13,2009. The laboratory performed analysis for <br /> volatile organic compounds in air via modified EPA Method TO-3 using gas chromatography with photo <br /> ionization and flame ionization detection. The method involves concentrating up to 200 mL of sample. The <br /> concentrated aliquot is then dry purged to remove water vapor prior to entering the chromatographic system. <br /> The TPH(Gasoline Range) results are calculated using the response factor of Gasoline. A molecular weight <br /> of 100 is used to convert the TPH(Gasoline Range)ppmv result to ug/L. <br /> Method modifications taken to nun these samples are summarized in the table below. Specific project <br /> trequirements may over-ride the ATL modifications. <br /> Requirement TO-3 ATL Modifications <br /> Daily Calibration Standard Prior to sample analysis Prior to sample analysis and after the analytical batch</= <br /> ' Frequency and every 4-6 hrs 20 samples <br /> Initial Calibration Calculation 4-point calibration 5-point calibration using average Response Factor <br /> using a linear <br /> ' regression model <br /> Initial Calibration Frequency Weekly When daily calibration standard recovery is outside 75- <br /> 125%,or upon significant changes to procedure or <br /> ' instrumentation <br /> Moisture Control Nafion system Sorbent system <br /> ' Minimum Detection Limit(MDL) Calculated using the 40 CFR Pt. 136 App. B <br /> equation DL=A+3.3S, <br /> where A is intercept of <br /> calibration line and S is <br /> ' the standard deviation <br /> of at least 3 reps of low <br /> level standard <br /> ' Preparation of Standards Levels achieved Levels achieved through loading various volumes of the <br /> through dilution of gas gas mixture <br /> mixture <br /> ' Receiving Notes <br /> There were no receiving discrepancies. <br /> ' Analytical Notes <br /> The reporting lint for Methyl tert-Butyl Ether has been raised to 0.002 ppmv. <br /> The recovery of surrogate Fluorobenzene in sample Influent was outside control limits due to high level <br /> hydrocarbon matrix interference.Data is reported as qualified. <br /> The reported LCS for each dailybatch has been derived from more than one analytical file. <br /> yh <br /> ' Page 2 of 8 <br />