Fluorene

All chemicals used were of analytical grade. Graphite flakes, acetic acid (99.7%), sulphuric acid (97.0%), sodium hydroxide (98%), acetone (99.5%), KMnO₄ (99.0%), NaNO₃ (99.0%), H₂O₂ (30%), and methanol (99.9%) were purchased from Sigma Aldrich USA. Itaconic acid (99%), azobisisobutyronitrile (98%), standard of coenzyme Q10 (98%), fluorene (98%), acetonitrile (99.8%), n-hexane (97.0%), 2-propanol (%), ethanol (96%), NaCl (99.5%), ascorbic acid (99.0%), tetrahydrofuran (THF) (99.9%), and phosphoric acid (85%) were bought from MERCK Germany. All of the experimental solutions were made with deionized (DI) water.

A PAH standard mixture containing the following 16 PAHs was purchased from Supelco (Bellefonte, PA, USA): naphthalene (Nap); acenaphthylene (Acy); acenaphthene (Ace); fluorene (Flu); phenanthrene (Phe); anthracene (Ant); fluoranthene (Flut); pyrene (Pyr); benzo[a]anthracene (BaA); chrysene (Chr); benzo[b]fluoranthene (BbF); benzo[k]fluoranthene (BkF); benzo[a]pyrene (BaP); benzo[g,h,i]perylene (BP); dibenzo[a,h]anthracene (DA); and indeno[1,2,3-cd]pyrene (IP). The following five deuterium isotopes of PAHs were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan): D₈-Nap; D₁₀-Ace; D₁₀-Phe; D₁₀-Pyr; and D₁₂-BaP. All organic solvents were of pesticide residue and polychlorinated biphenyl test grade. Other chemicals and ultrapure water were of analytical grade.

Thirteen polycyclic aromatic hydrocarbons were analysed in this study. Certified reference material EPA 525 PAH Mix B (SupelCo, Bellefonte, PA, USA) was acquired as an internal standard, containing: acenaphthylene (ACNY), anthracene (ANTH), benz[a]anthracene (B[a]A), benzo[b]fluoranthene (B[b]F), benzo[k]fluoranthene (B[k]F), benzo[ghi]perylene (B[ghi]P), benzo[a]pyrene (B[a]P), chrysene (CHRY), dibenz[a,h]anthracene (D[ah]A), fluorene (FL), indeno[1,2,3-cd]pyrene (I[123-cd]P), phenanthrene (PHEN), and pyrene (PYR).
Sodium chloride (NaCl), magnesium sulfate (MgSO₄), and hexane (C₆H₁₄) (HPLC grade) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Hypergrade acetonitrile (ACN) was purchased from Merck (Kenilworth, NJ, USA). Sample clean-up was performed using Supel QuE Z-Sep tubes (SupelCo). Preparation of samples was performed using polypropylene tubes. Glass tubes were used during extraction to minimise interference of the samples.

Acetonitrile, dichloromethane, n-hexane, and toluene, all of HPLC grade, were purchased from Merck (Darmstadt, Germany). Deionized water was obtained by using a Milli-Q system (Millipore, Bedford, MA, USA). Silica cartridges for SPE (5 g, 20 mL and 2 g, 12 mL, Mega Bond Elut) and amino cartridges (5 g, 20 mL) were from Varian (Palo Alto, CA, USA). The standard PAHs mixture, 610 M, in 1 mL of methanol/dichloromethane (Supelco, Bellefonte, PA, USA) consisted of: acenaphthene (1000 μg/mL, 99.0%), fluoranthene (200 μg/mL, 99.0%), naphthalene (1000 μg/mL, 96.9%), BaA (100 μg/mL, 99.0%), BbF (200 μg/mL, 99.1%), BaP (100 μg/mL, 99.5%), BkF (100 μg/mL, 99.6%), Ch (100 μg/mL, 99.0%), acenaphthylene (2000 μg/mL, 99.0%), anthracene (100 μg/mL, 99.0%), BghiP (200 μg/mL, 99.0%), fluorene (200 μg/mL), phenanthrene (100 μg/mL, 97.2%), DBahA (200 μg/mL, 96.7%), IP (100 μg/mL, 99.7%), and pyrene (100 μg/mL, 97.4%).

Standards PAH mix, including 16 mentioned PAHs (benzo(a)pyrene [BaP], acenaphthylene [Ace], naphthalene [NA], fluorene [F], acenaphthene [Ac], phenanthrene [Pa], fluoranthene [Fl], anthracene [A], benzo(a)anthracene [BaA], pyrene [P], benzo(b)fluoranthene [BbF], chrysene [Ch], benzo(k)fluoranthene [BkF], dibenzo[a,h]anthracene [DhA], indeno[1,2,3‐cd]pyrene [IP] and benzo[g,h,i]perylene [BgP]) was purchased from Supelco (Bellefonte, PA, U. S.). The standard solutions were prepared in dichloromethane, with all mentioned PAHs concentration of 0.1 mg/ml. Stock standard solutions were mixed with methanol‐dichloromethane (50:50, v/v) every week for the preparation of a working mixed solution (1 µg/ml for each mentioned PAHs) which was used to measure the extraction performance under various conditions. The working and stock solutions were preserved at 4°C and biphenyl was used as an internal standard at a concentration of 0.05 µg/ml in methanol. Multi‐walled carbon nanotubes were purchased from Hanwha Nanotech (MWCNT CM‐95, Korea) and the adsorbent of MWCNT‐MNP was prepared as described previously (Rastkari & Ahmadkhaniha, 2013). All other chemicals and solvents were of analytical grade.