Determination of 16 Polycyclic Aromatic Hydrocarbons (PAHs) in Automotive Materials by HPLC

• Analyte: 16 PAHs
• System: EClassical 3200 HPLC System with UV Detector
• Column: Supersil ODS2 (5 μm, 4.6 × 250 mm)
• Highlight: Comprehensive HPLC method for simultaneous determination of 16 PAHs in automotive materials with excellent linearity, sensitivity, and compliance with draft industry standards.

Polycyclic aromatic hydrocarbons (PAHs) are a large class of organic compounds containing two or more fused benzene rings. They are potent carcinogens and are widely present in the environment due to incomplete combustion. In automobiles, PAHs can be released from interior materials such as seat cushions, door panels, paints, adhesives, and even fragrances. The draft standard "Determination of Polycyclic Aromatic Hydrocarbons in Automotive Materials" (under preparation) specifies limits for 18 PAHs. This solution presents an HPLC method for the determination of 16 priority PAHs , following the draft standard and HJ 784-2016, suitable for quality control of automotive components.

16 PAHs mixed standard

Commercially available (Naphthalene, Acenaphthylene, Fluorene, Acenaphthene, Phenanthrene, Anthracene, Fluoranthene, Pyrene, Chrysene, Benzo[a]anthracene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Benzo[a]pyrene, Dibenzo[a,h]anthracene, Benzo[ghi]perylene, Indeno[1,2,3-cd]pyrene)

Decafluorobiphenyl (optional internal standard)

Reagents

Acetonitrile (HPLC grade), n-Hexane (HPLC grade), Acetone (HPLC grade), Dichloromethane (HPLC grade)

Nitrogen gas (99.99%), Deionized water (18.2 MΩ·cm)

Other materials

Volumetric flasks, microwave extraction vessels, solid-phase extraction cartridges (silica), nitrogen evaporator, etc.

Standard Solution Preparation

Mixed stock solution (20 μg/mL each): Accurately pipette 1 mL of the commercial 16 PAHs standard (e.g., 200 μg/mL) into a 10 mL volumetric flask and dilute to volume with acetonitrile.

Working standard solutions: Dilute the stock solution with acetonitrile to obtain concentrations of 0.1, 0.5, 1.0, 5.0, and 10.0 μg/mL.

Internal standard solution (optional): Prepare a solution containing 5.0 μg/mL of 16 PAHs and 2.0 μg/mL of decafluorobiphenyl in acetonitrile.

Sample preparation

Cut the sample into 1 cm × 1 cm pieces, freeze with liquid nitrogen, and grind to particles ≤1 mm.

Extraction

Accurately weigh about 1 g of the ground sample (to 0.0001 g) into a microwave extraction vessel. Add 15 mL of n-hexane/acetone (1:1, v/v). Extract in a microwave digester at 100°C for 15 min. Cool to room temperature.

Transfer and concentration

Transfer the extract completely to a stoppered tube, rinsing the vessel twice with 5 mL of n-hexane/acetone (1:1). Concentrate the combined extract to near dryness under nitrogen. Add 2 mL of n-hexane and vortex to dissolve.

Cleanup (for plastic or rubber samples):

For plastic samples: Add 5 mL of n-hexane to the extract. If precipitation occurs, let stand and transfer the supernatant. Wash the precipitate twice with 5 mL of n-hexane. Combine the supernatants, concentrate to near dryness, and reconstitute in 2 mL of n-hexane. Pass through a pre-activated silica SPE cartridge (activated with n-hexane) at 0.5 drops/s. Wash with 5 mL of n-hexane and discard the wash. Elute with 5 mL of n-hexane/dichloromethane (3:2, v/v). Evaporate the eluate to dryness under nitrogen and reconstitute in 10 mL of acetonitrile.

For rubber samples: Pass the extract directly through a pre-activated silica SPE cartridge, wash with 5 mL of n-hexane, elute with 5 mL of n-hexane/dichloromethane (3:2), evaporate to dryness, and reconstitute in 10 mL of acetonitrile.

HPLC System

EClassical 3200 configured with two high-pressure pumps, UV detector, column oven, autosampler optional, gradient mixer, Chromatography data station

Pretreatment equipment

Microwave extraction system, SPE manifold, nitrogen evaporator, analytical balance, etc.

Column: Supersil ODS2 (5 μm, 4.6 × 250 mm)

Mobile phase: A: Acetonitrile; B: Water, in gradient (Table 1)

Table 1. Gradient program

Flow rate: 1.0 mL/min

Detection wavelength: 220 nm or 254 nm

Injection volume: 10 μL

Column temperature: 30°C (optimized after temperature study)

Temperature Optimization

The effect of column temperature on separation was studied at 25, 30, 35, and 40°C (Figure 1). As temperature increased, resolution for critical pairs (e.g. peaks 10 and 11, 16 and 17) decreased. A temperature of 30°C was selected as optimal for baseline separation of all 16 PAHs.

Figure 1. Chromatograms of 16 PAHs at different temperatures

Typical Chromatogram

A standard solution containing 5.0 μg/mL of 16 PAHs and 2.0 μg/mL of decafluorobiphenyl was analyzed at 30°C. The chromatogram (Figure 2) shows excellent separation of all compounds. Chromatographic parameters are summarized in Table 2.

Figure 2. Chromatograms of 16 PAHs standard

Table 2. Chromatographic parameters of 16 PAHs

Linearity

Working standard solutions at 0.1, 0.5, 1.0, 5.0, and 10.0 μg/mL were injected. Calibration curves were constructed by plotting peak area against concentration. Linear equations and correlation coefficients are given in Table 3. All compounds show excellent linearity (R ≥ 0.999) over the range of 0.1–10 μg/mL.

Table 3. Linear equations for 16 PAHs

Detection Limits

Instrument detection limits (S/N = 3) were determined and converted to method detection limits (Table 4). The method achieves sub-ng/mL sensitivity, well below the proposed regulatory limits.

Table 4. Method detection limits for 16 PAHs

The HPLC method using a Supersil ODS2 column provides reliable separation, excellent linearity, and high sensitivity for 16 priority PAHs in automotive materials. It meets the requirements of the draft standard and is suitable for routine quality control in the automotive industry.