Automated Sample Cleanup of Olive Oil

Gel permeation chromatography (GPC) has been used as an effective cleanup procedure for removing high molecular weight interfering molecules such as lipids, pigments, proteins, and polymers before GC or HPLC analysis. The GPC cleanup method has been extensively documented (1–3) and is also recommended in US EPA SW-846 Method 3640A. To demonstrate the efficacy of this method to extract polar and nonpolar substances by using the KNAUER Smartline GPC Cleanup Unit 6500, olive oil samples were investigated by spiking these with different types of organic pollutants, including PAHs, phthalates, phenols, and triazine.

Figure 1

Experimental

To determine the elution profile of the GPC column, a calibration solution containing corn oil bis(2-ethylhexyl)phthalate, methoxychlor, perylene, and sulfur was injected on a glass column packed with Bio-Beads SX-3 and eluted with cyclohexane/ethyl acetate (1:1, v/v). Based on the UV trace, fraction collection was started just after the corn oil peak and stopped before sulfur elutes (Fig. 1). The sample loops on the Smartline GPC Cleanup Unit 6500 were then loaded with the diluted olive oil samples and the extracted fractions were automatically collected by the built-in fractionation valve (Fig. 2).

Figure 2

The KNAUER GPC Cleanup Unit 6500 is a completely modular system for sample cleanup and includes in its standard configuration:

• A fixed-wavelength UV detector (254 nm)

• An automated valve for sample loading which accommo- dates 15 sample loops and one wash loop to avoid cross contamination

• And a pulsation-free eluent pump

Up to 15 oil samples can be loaded in either 1 ml or 5 ml samples loops. The pesticide fraction is collected by a third switching valve.

Conclusion

GPC sample preparation is a useful tool for separating small amounts of pesticides from high molecular weight matrices such as olive oil. The KNAUER Smartline GPC Cleanup Unit 6500 is particularly well-suited for sample preparation in pesticide analysis but can also be easily adapted to other laboratory procedures to perform a large variety of GPC sample preparation tasks.

References

(1) S.J. Chamberlain, Analyst, 115:1161–1165 (1990)

(2) A. Di Muccio, A. Ausili, L. Versori, I. Camoni, T. Dommarco, L. Ganibetti, A. Santillo, and F. Versori, Analyst, 115: 1167–1169 (1990)

(3) M. Guardia-Rubio, M.L. Fernandez-De Cordova, M.J. Ayory-Canada, and A. Ruiz-Medina, J. Chromatogr. A, 1108, 231–239 (2006)

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