Chemical and Engineering News has a report about a new Chemical Research in Toxicology paper that outlines how 
Thin Layer Chromatography is used to differentiate between a potent carcinogen found in diesel exhaust (3-nitrobenzanthrone or 3-NBA) and 2-NBA, which is largely the product of a nitration reaction that happens spontaneously in the atmosphere.
Here’s an excerpt:
The team incubated each isomer with DNA and a variety of enzymes, and then used thin layer chromatography to determine the extent to which the DNA had been altered. Because 2-NBA did not form potentially harmful DNA adducts, the researchers determined that it is not a substrate for enzymes that activate 3-NBA toward DNA. In experiments with intact human liver cells, 3-NBA again generated DNA adducts, whereas 2-NBA did not.