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Method 102 Revision 1 3.3 A gas chromatograph equipped with a gas sampling valve and either a sample loop or freeze -out inlet system and a photoionization detector is required. The detector operates at 10.2 eV. 5 Procedure 5.1 All bags and samplers are prepared for sampling as out- lined in Appendix A, "Procedures for Atmospheric Bag Sampling". 5.2 The air sample is analyzed for ben-_�-ene by using either the loop method or the freeze -out method. The freeze - out method is used for lower benzene concentrations of less than 25 ppb. • 5.2.1 The procedure for the loop method follows: 5.2.1.1 Transfer the air sample from the air sample bag and inject it into the sample loop of the gas chromatograph using a 100 ml, syringe fitted with a Luer-lok to quick -connect adapter. 5.2.1.2 The gas sampling valve has a fixed volume sample loop of about 1 mL. 3 3.4 A freeze -out system consisting of a U-shaped stainless steel trap filled with stainless steel clippings is used to concentrate the sample. 3.5 A stainless steel column (6 ft x 1/8 in) packed with 10% N,N-bis(2--cyanoethyl)formamide on 100/120 mesh Chromosorb PAW is used. 3.6 For a confirmation of the benzene analysis, an alter- nate column should be used such as a stainless steel GC column packed with 10% tricyanoethoxy propane (TCEP). 3.7 An analog recorder and an electronic integrator to quantify peak areas are required. 3.8 Ground glass syringes (100 mL capacity) or other suitable devices are needed to transfer air samples from the Tedlar bag to the GC sample inlet. 4 Re@gen Vs 4.1 The primary standard used in this anal:rsis should be the National Bureau of Standards (NBS) benzene standard reference material. 4.2 Helium with a minimum purity of 99.995% should be used. 4.3 Commercial liquid nitrogen (b.p.=-196®) is used to cool freeze -out trap. 5 Procedure 5.1 All bags and samplers are prepared for sampling as out- lined in Appendix A, "Procedures for Atmospheric Bag Sampling". 5.2 The air sample is analyzed for ben-_�-ene by using either the loop method or the freeze -out method. The freeze - out method is used for lower benzene concentrations of less than 25 ppb. • 5.2.1 The procedure for the loop method follows: 5.2.1.1 Transfer the air sample from the air sample bag and inject it into the sample loop of the gas chromatograph using a 100 ml, syringe fitted with a Luer-lok to quick -connect adapter. 5.2.1.2 The gas sampling valve has a fixed volume sample loop of about 1 mL. 3