## 3 Sample Treatment and Analysis Methods
### Analytical Methods  
Currently, there is a priority list of 16 PAHs, which are commonly monitored in the environment due to their adverse health effects [44]. However, there is no such list for NPAHs, which is likely because of a general paucity of environmental data, but also because the known concentrations are much lower than their parent PAHs. NPAHs with two-rings, such as 1-, and 2-nitronaphthalenes (1-, and 2-NNap) to five-rings, such as 6-NBaP are often analyzed [11; 41]. Table 2 shows typical analytical methods recently developed for NPAHs in air, water, soil, and sediments and these are performed primarily using GC-MS and HPLC- FL/CL. These are detection methods which can analyze picogram (pg) levels of NPAHs. In the analysis of NPAHs using GC-MS, negative ion chemical ionization (NICI) mode was two orders of magnitude more sensitive to NPAHs than electron ionization (EI) mode, because highly electronegative compounds are readily ionized by resonance capture of thermal electrons [45]. This has played the most important role in the recent development of sensitive GC-MS analysis of NPAHs. Laser ionization MS has been also used in the analysis of NPAHs. Small amounts of solid sample are directly injected into the GC-MS using thermal desorption [46]. By introducing an on-line chemical reducer of NPAHs to their aminated analogues (APAHs) using hydrazine monohydrate into GC coupled with multiphoton ionization TOF-MS, the sensitivity of NPAHs was two to eight times improved [47]. When the -NO\({}_{2}\) groups of NPAHs are chemically or electrically reduced, the resulting APAHs are fluorescent. In addition, these APAHs are extremely sensitive to CL reactions. Therefore, chemical reducing methods using sodium hydrosulfide or zinc metal have been  
\begin{table} \begin{tabular}{l l l l l} \hline \hline \multicolumn{1}{c}{**Compounds**} & \multicolumn{1}{c}{**Sample and Treatment**} & \multicolumn{1}{c}{**Analysis Method**} & \multicolumn{1}{c}{**Recovery and LOD**} & \multicolumn{1}{c}{**Ref.**} \\ \hline \hline
6 NPAHs (2-NF, 9-NAnt, 3-NF, 1-NF, 6-NC), 16 PAHs. & River water, groundwater, seawater, rainwater. DLIME with acetonitrile (dispersive solvent), chloroform & & Recoveries: 83-119-, 9-NAnt and 1-NF were detected in environmental water & [33] \\
16 NPAHs (1-, 2-NNaps, 2-, 3-NPs, 5-Nace, 2-NFs, 1-NF, 7-NBaA, 6-NC). & Drinking water, snow, sausage, meat. & & Recoveries: 71.3–112.5\%, 1.00\%-2.9\%-3.8\%-0.2\%-1\%-5.6 & [34] \\
9-NPs, 2-, 3-NPs, 1-NFs, 1-NF, 7-NBaA, 6-CNBaP & & & & \\ \hline Lake water, wastewater, sewage. & & & & \\
10 NPAHs (2-NNap, 2-Nbp, 5-Nace, 2-NF, 9-NAnt, 9-NN, 1-NP, 2-NPR, 6-NC). & SDME (mico extractor) with polymethylsiloxane/divinylbenzene (1 cm \(\times\) 65 mm), 7-100 \(\mu\) PDMS, 85-nm polyacrylate \(\rightarrow\) GC-MS & GC-Quadrupole MS. & Recoveries: 69.1–110.1\% (PDAMS/(DVS), LOD\(\times\) 0.007–0.063 \(\mu\)g L\({}^{-1}\).) & [35] \\
2-7-DNE, 6-NC). & & & & \\ \hline
4 NPAHs (9-NAnt, 2-NF, 3-NF, 1-NP), PAHs, OPAHs & Coffee brow. Coffee brow + & & & \\
1-NF, 2-NFs, 1-NF, 2-NFs, OPAHs & Acetonitrile \(\rightarrow\) DI-SPER (direct immerses) with 85 \(\mu\)m PDMS/DVB & GC-MS, EI. & Recoveries: 82–96\% LODs: \\  & & & & \\ \hline
11 NPAHs (2-NNap, 2-Nbp, 5-Nace, 2-NF, 9-NAnt, 1-NP, 2-, 3-NFs, 1-NF, 2-Y-DNE, 6-NC), PAHs & Tap water, river water, lake water, wastewater. MOF (DI-SPME) with & & \\
2-NF, 3-NF, 6-NPAH, 6-NPAH, 6-NPAH, 6-NPAH, 6-NBaP & Zoolite imidazolate framework-8 & GC-Quadrupole MS. & Recoveries: 66.3–104.6\%, 1.00\%-1.0\%-19.8 \(\mu\)g L\({}^{-1}\). & [37] \\ \hline
6 NPAHs (3-Nbp, 9-NAnt, 9-NP, 3-NF, 1-NF, 6-NC). & & & \\ \hline
6 NPAHs (3-Nbp, 9-NAnt, 9-NP, 3-NFs, 1-NF, 6-NC). & & & & \\ \hline
6 NPAHs (2-NNap, 2-3-NPs, 2-, 3-NPs, 2-, 9-NAnt, 3-NFs, 1-NF, 2-NFs, 6-NC, 2-NF, 9-NAnt, 3-NFs, 1-NFs, 1-NFs, 6-NC, 2-NF, 9-NAnt, 9-NNs, 2-, 3-NFs, 6-NC, 6-NBaP). & & & \\ \hline  & Foods (Rice, radish, lettuce). & & & \\ \hline
2 NPAHs (2-NF, 1-NP), BaP. & QuEChenFS. LE with acetonitrile \(\rightarrow\) & & & \\ \hline  & & & \\ \end{tabular}