Analysis of Polycyclic Aromatic Hydrocarbons in Soil with AgilentSampliQ QuEChERS AOAC Kit and HPLC-FLD

An HPLC-Florescence Detection (FLD) method was developed and validated for the determination of sixteen polycyclic aromatic hydrocarbons (PAHs) in soil. The analysed PAHs include naphthalene (Nap), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Flu), phenanthrene (Phe), anthracene (Ant), fluoranthene (Fln), pyrene (Pyr),1,2- benza[a]anthracene (BaA), chrysene (Chr), benzo[e]pyrene (BeP), benzo[e]acenaphthylene (BeA), benzo[k]fluoranthene (BkF), dibenzo[a,h]anthracene (DahA), benzo[g,h,i]perylene (Bghi)P and indeno[1,2,3- cd]pyrene (InP). The method employs aquick, easy, cheap, effective, rugged and safe (QuEChERS) multiresidue sample preparationprocedure adopted from the Association of Analytical Communities (AOAC) Official method 2007.01 for extraction and cleanup. The analytes were separated onan
Agilent ZORBAX Eclipse PAH column (4.6 mm × 50 mm, 1.8 μm) by gradient elutionwith a binary system of acetonitrile - water with subsequent fluorescence detectionset at appropriate excitation and emission wavelengths. The analyte recoveries ranged from 86.0% to 99.2% with relative standard deviations ranging from 0.6% to 1.9% at three different fortification levels. The limits of detection and quantification ranged from 0.005 to 0.78 and 0.02 to 1.6 ng/g, respectively.

Polyaromatic hydrocarbons, or polynuclear aromatic hydrocarbons (PAHs), are fused ring aromatic compounds classified by the number of carbon rings as well as their carcinogenicity.

The two and three ring PAHs are noncarcinogenic, while several of the four, five and six ring PAHs are carcinogenic. The four ring PAHs, chrysene and benzo- [a]anthracene, the five ring PAHs, benzo[a]pyrene, benzo[b]fluoranthene, benzo [k] fluoranthene and dibenzo [a,h]
anthracene, and the six ring PAH, indeno [1,2,3-cd] pyrene, are carcinogenic PAHs. Benzo [a] pyrene is the most potent carcinogen among the PAHs [1].

The US-EPA and EU lists sixteen of these PAHs as hazardous compounds [2]. Generally PAHs are lipophilic compounds that showa high affinity for organicmatter and their determination in soil always requires powerful extraction techniques to release the strongly sorbed contaminants from the soil material [3]. Several extractionmethods (soxhlet, liquid-liquid or solid phase extraction) for sample preparation of soil have been investigated
and most of these involved an evaporation stepwhich leads to the loss or low recoveries of the volatile PAHs such as naphthalene [4].

The AOAC QuEChERS method has been widely applied in the analysis of pesticides in food since it was introduced by United States Department of Agriculture (USDA) scientists [5].

More recently, the technique has branched out into new application areas outside of food safety. In general, there are two major steps: extraction and dispersive SPE cleanup. The method uses a single step buffered acetonitrile extraction while simultaneously salting out water from the aqueous sample using anhydrousmagnesiumsulfate (MgSO4) to induce liquid-liquid partitioning. After removing an aliquot from an organic
layer, for further cleanup, a dispersive solid phase extraction (dSPE) is conducted using a combination of primary secondary amine (PSA) sorbent to remove fatty acids from other components and anhydrous MgSO4 to
reduce the remaining water in the extract. Other sorbents, such as graphitized carbon black (GCB), may be added to remove pigments and sterol, or C18 to remove lipids and waxes.

This application note presents amethod for the analysis of PAHs at trace levels in soilwith HPLC-Fluorescence detection (FLD). The HPLCmethods are useful for PAH analysis since UV and fluorescence detection offer enhanced selectivity over other techniques such asGCwith flame ionization detection [6]. Themethod includes sample preparation with SampliQAOAC Buffered Extraction kit (p/n 5982-5755) and SampliQAOAC Fatty Dispersive SPE 15ml kit (p/n 5982-5156).Chemical structures of the PAHs in this study are shown in Figure 1.