Fig. 1. Recoveries and standard deviation for Soxhlet, ultrasonic and PLE extraction of pine needles spiked with 50 ng/g of each of the 16 EPA PAHs, using alumina cartridges for clean-up.

Fig. 2. Recoveries and standard deviation for ultrasonic extraction of pine needles spiked with 50 ng/g of each of the 16 EPA PAHs, using glass columns packed with 5 g of Florisil, silica or alumina for clean-up.

Fig. 3. Comparison of recoveries and standard deviation for ultrasonic extraction of 2 and 10 g of pine needle samples spiked with 50 ng/g of each of the 16 EPA PAHs, using alumina cartridges as sample clean-up.

Fig. 4. Comparison of recoveries and standard deviation for ultrasonic extraction of 2 g of pine needle samples spiked with 10 and 50 ng/g of each of the 16 EPA PAHs, using alumina cartridges for clean-up.

GC–MS retention time window, compounds eluting at each window, retention time and ions monitored in the SIM mode

Deuterated surrogate compounds in italics as well as anthracene-d₁₀, used as internal standard.

Intermediate precision (n = 6) and LODs of 16 EPA PAHs using a standard solution of 0.25 mg/L and samples spiked at 50 ng/g and analyzed by ultrasonic extraction and alumina cartridge clean-up (dw = dry weight)

Concentration of the 16 EPA PAHs in naturally contaminated pine needle samples collected from four different locations (ultrasonic extraction and clean-up with 5 g alumina cartridges prior to GC–MS), distribution according to the number of aromatic rings and the ratio ΣCOMB (4, 5 and 6-ring PAHs)/ΣPAHs

n.d. = not detected.