Ferrofluid-based liquid-phase microextraction

A new mode of liquid-phase microextraction based on a ferrofluid has been developed. The ferrofluid was composed of silica-coated magnetic particles and 1-octanol as the extractant solvent. The 1-octanol was firmly confined within the silica-coated particles, preventing it from being lost during extraction. Sixteen polycyclic aromatic hydrocarbons (PAHs) were used as model compounds in the development and evaluation of the extraction procedure in combination with gas chromatography–mass spectrometry. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 20 mL sample volume, 10 mg of the silica-coated magnetic particles (28 mg of ferrofluid), agitation at 20 Hz, 20 min extraction time, and 2 min by sonication with 100 μL acetonitrile as the final extraction solvent. Under optimal extraction conditions, enrichment factors ranging from 102- to 173-fold were obtained for the analytes. The limits of detection and the limits of quantification were in the range of 16.8 and 56.7 pg mL−1 and 0.06 and 0.19 ng mL−1, respectively. The linearities were between 0.5–100 and 1–100 ng mL−1 for different PAHs. As the ferrofluid can respond to and be attracted by a magnet, the extraction can be easily achieved by reciprocating movement of an external magnet that served to agitate the sample. No other devices were needed in this new approach of extraction. This new technique is affordable, efficient and convenient for microextraction, and offers portability for potential onsite extraction.