21716
The UV absorption and electronic circular dichroism ( ECD ) spectra of ( R ) - and ( S ) - nicotine and ( S ) - nornicotine in aqueous solution were measured to a significantly lower wavelength range than previously reported , allowing the identification of four previously unobserved electronic transitions .
 ( R ) - and ( S ) - nicotine, ( S ) - nornicotine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ( R ) - and ( S ) - nicotine, ( S ) - nornicotine