Benefits of a binary modifier with balanced polarity for an efficient supercritical fluid extraction of PAHs from solid samples, followed by HPLC

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed environmenta l contaminants. Their presence in soils indicates a possible contamination of ground water used for human purposes. Only with a rapid and efficient me thod could they be analysed in a routine setting. Although there are a great number of publications on this subject, there ar e many differences between their ideal SFE conditions and related extractio n recoveries. With improvements on the extraction capacity of the supercritical fluid suc h as higher pressure, higher temperature and a stronger modifier effect, th e developed method intends to be more robust and applicable to a larger ran ge of matrices. The optimal conditions consist on a 15 minutes extraction at 45 MPa pressur e and 95 degreesC. The supercritical fluid is a ternary mixture of CO2 modi fied with methanol/dichloromethane 5:1. The separation and quantitation was performed by HPLC coupled with a diode array detector in series with a flu orescence detector, which combines high sensitivity with the possibility to confirm the components' identity in a complex chromatogram. Three of the s ix studied PAHs show recoveries above 90% and the others, those of higher m olecular weight, around 70-90%. This modified SFE procedure was applied to three environmental samples and fulfils the requirements of rapidity, high extraction efficiency, and simpl e performance.