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Rapid, Efficient HPLC Analysis for Polynuclear Aromatic Hydrocarbons
Abstract
Analysis times for many HPLC separations can be reduced by 60 to 75% or more by using short columns containing highly selective stationary phases. A modified C18 phase resolves polynuclear aromatic hydrocarbons through interactions based on molecular shape. Eighteen PAHs can be separated in less than 6 minutes on a 50 × 4.6 mm ID column containing this application-specific packing. Using a 150 × 3.2 mm column, the same target analytes can be resolved to baseline in less than 18 minutes.
click the image to enlarge
Figure 1. Eighteen PAHs separated in 6 minutes on a highly selective 50 mm HPLC column.
Column: Pinnacle II PAH, 50 × 4.6 mm, 5 μm particles, 110 Å pores; Sample: 5 to 10 ppm each analyte in 5 μL methylene chloride:acetonitrile, 1:9 (v/v); Mobile Phase: water (A)/acetonitrile (B), time/% B: 0 min./50, 1.5 min./60, 4.0 min./100, 5.5 min./100, 5.6 min./50; Flow: 3.0 mL/min.; Temperature: ambient; Detection: UV, 254 nm.
Peaks: 1) naphthalene, 2) acenaphthylene, 3) 1-methylnaphthalene, 4) 2-methylnaphthalene, 5) acenaphthene, 6) fluorene, 7) phenanthrene, 8) anthracene, IS) o-terphenyl (int. std.), 9) fluoranthene, 10) pyrene, IS) p-terphenyl (int. std.), 11) benzo(a)anthracene, 12) chrysene, 13) benzo(b)fluoranthene, 14) benzo(k)fluoranthene, 15) benzo(a)pyrene, 16) dibenzo(a,h)anthracene, 17) benzo(ghi)perylene, 18) indeno(1,2,3-cd)pyrene.
| Known mutagens and carcinogens, polynuclear aromatic hydrocarbons are monitored worldwide in water, soil, and waste. In the United States, the Environmental Protection Agency (EPA) developed a reversed phase HPLC approach, Method 8310, for monitoring target PAHs at ppb detection limits in groundwater and wastes. This analysis is consistent with older EPA methods 550.1 and 610.
click the image to enlarge
Figure 2. Eighteen PAHs resolved to baseline in 18 minutes on a 150 mm column.
Column: Pinnacle II PAH, 150 × 3.2 mm, 5 μm particles, 110 Å pores; Sample: 5 μg/mL each analyte in 5 μL acetonitrile; Mobile Phase: water (A)/acetonitrile (B), time/% B: 0 min./40, 7.0 min./60, 11.0 min./100, 17.9 min./100, 18.0 min./40; Flow: 1.2 mL/min.; Temperature: ambient; Detection: UV, 254 nm.
Peaks: see Figure 1. |
On a conventional C18 stationary phase in a 250 × 4.6 mm column, an analysis for 16 target PAHs in EPA methodology consumes 30 minutes or more. We have developed a modified C18 phase that interacts with PAHs on the basis of molecular shape, and better resolves these compounds. Because selectivity has been optimized, this stationary phase allows higher flow rates to be used without sacrificing critical separations. In gradient analyses, column re-equilibration can be accelerated and, because analytes spend less time in a short column, analyte bands are often sharper and narrower, thus increasing sensitivity.
Figure 1 shows a mixture of 18 PAHs and two internal standards separated in less than 6 minutes on a 50 × 4.6 mm ID column containing application-specific Pinnacle II™ PAH packing. 1-methylnaphthalene and 2-methylnaphthalene are not listed in the US EPA methods but must be resolved from the target PAHs, and are included in individual state methodologies. In a 150 × 3.2 mm column, the Pinnacle II PAH material resolves the target PAHs and the methylnaphthalenes to baseline in less than 18 minutes (Figure 2).
Reducing column length and increasing flow rate can be an effective approach for increasing sample throughput, particularly when the selectivity of the stationary phase is optimized for the analysis, as these applications show.
Restek Corp.
110 Benner Circle
Bellefonte, PA 16823
81H
Restek Corporation
110 Benner Circle
Bellefonte, PA, 16823
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