A comparison of sampling techniques for VOCs in soil

Samples (5 g) of an organic soil spiked with a standard volatile organic co mpound mixture were collected by two methods. One group of samples was weig hed upon transfer with a spatula into vials, an aqueous sodium bisulfate so lution and a magnetic stirring bar were added and the vial was immediately capped. The other group of samples was obtained with a coring sampler that collected a volume of soil equivalent to 5 g. The sample was immediately tr ansferred into similarly prepared vials. The vials were then sealed with se ptum-sealed screw caps. Analytes were extracted from the soil matrix using a purge-and-trap technique, SW-846 EPA Method 5035, and then separated, ide ntified, and quantitated by gas chromatography/mass spectrometry SW-846 EPA Method 8260. Samples obtained by means of the coring sampler consistently gave lower recoveries than did those samples that were manually weighed and placed in a sample vial. (C) 2000 Elsevier Science Ltd. All rights reserve d.