Sampling Information Normal procedures for volatile organic compound (VOC) collection should be followed. Analysis requires two (2) 40 ml VOC vials per compound per analysis for δ 2 H and δ 13 C or four (4) 40 mL VOC vials per compound for δ 37 Cl (i.e. if you want to analyze TCE, cis-DCE and trans-DCE in one sample for both δ 13 C and δ 37 Cl, then please collect 3x2+3x4=18 vials