Organic extract was dried with anhydrous Na2SO4. 1 mL of extract was placed in 2 mL vial and then it was automatically injected to GC-FID. Low concentration extracts ( less than 1 mg/L ) were concentrated 10 times using a Laborota 4000 Heidolph rotary evaporator. For GC-FID calibration, NB solution within 1 and 100 mg/L were prepared in n-hexane and analyzed in the same way as the samples.