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E E E E I F r Li 7 II I n H n H Method 102 Revision 1 operating conditions described in this method may interfere with the quantification. Proof of chemical identity for benzene requires confirmation by other means. 8.3.1 Benzene is positively identified by means of a gas chromatograph/mass spectrometer. 8.4 Advantages and disadvantages of Method 102 are listed below: 8.4.1 The air sampling equipment is easily set up and in- volves no liquids. The ambient concentrations of benzene are are stable for at least 24 hours in the Tedlar sampling bags if the sampling bags are kept away from direct sunlight and are not exposed to temperatures greater than 90 F. 8.4.2 A representative integrated sample is readily at- tainable because the equipment samples at a con- stant rate. 8.4.3 The sample is easily and repeatedly introduced into the GC by using a volumetric gas sampling valve or cryogenic trap. 8.4.4 The lower concentration limit of the analysis may be extended by concentrating the sample by freez- ing out a larger volume of the sample. 8.4.5 The polyvinyl fluoride (Tedlar) film sample bag is susceptible to leaks and permeation through the bag. 8.4.6 The sample is susceptible to contamination when it passes through the sampling system. 9 References 9.1 Bennett, C. A. and Franklin, N. L., "Statistical Analysis in Chemistry and the Chemical Industry", pp. 222-232, John Wiley & Sons, Inc., New York (1954). 9.2 Draper, N. R. and Smith, H., "Applied Regression Analysis", P.30, John Wiley & Sons, Inc., New York (1966). 9.3 Purnell, H.,"Gas Chromatography", pp. 301-302, John Wiley & Sons, Inc., New York (1962). 9.4 U. S. Environmental Protection Agency, "Quality Assurance Handbook for Air Pollution Measurement Systems, Volume I - Principles", Research Tri- angle Park, North Carolina 27711 (1976) Q