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Joint International Conference on Long-term Experiments ...

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THIN LAYER CHROMATOGRAPHY OF STERIGMATOCYSTIN IN CHEESE<br />

Bara Lucian<br />

University of Oradea, Faculty of Envir<strong>on</strong>mental Protecti<strong>on</strong><br />

ABSTRACT<br />

A <strong>on</strong>e-dimensi<strong>on</strong>al thin layer chromatographic method has been developed for de<strong>term</strong>ining<br />

sterigmatocystin in cheese. Cheese is extracted with acet<strong>on</strong>itrile-4% KCl (85 + 15). A<br />

simplified liquid-liquid partiti<strong>on</strong> cleanup is used, and the sample extract is passed through a<br />

cupric carb<strong>on</strong>ate column for final purificati<strong>on</strong>. Sterigmatocystin is visualized by spraying<br />

the plate with aluminium chloride. The fluorescence of the spot is enhanced 10-fold by<br />

additi<strong>on</strong>al plate spraying with silic<strong>on</strong>e-either mixture, enabling sterigmatocystin detecti<strong>on</strong><br />

and quantitati<strong>on</strong> at 2 and 5 μ/kg, respectively. Average recoveries were 88.3 and 86.4% at<br />

the 10 and 25 μ/kg levels, respectively.<br />

Keywords: cromatography, cheese<br />

INTRODUCTION<br />

Sterigmatocystin is a mycotoxin that has potent toxic and carcinogenic effects. This<br />

metabolite is produced by several species of Aspergillus and at least <strong>on</strong>e species of<br />

Bipolaris. Sterigmatocystin occurs naturally in grains, green coffee, fruit juices and fruitbased<br />

infant foods, and cheese. Since sterigmatocystin-producing fungi are so ubiquitously<br />

distributed, this metabolite must be c<strong>on</strong>sidered as an important c<strong>on</strong>taminant in these<br />

commodities as well as in other foods and feeds. Thus, interest was aroused in analyzing<br />

cheese for sterigmatocystin to de<strong>term</strong>ine levels and incidences of c<strong>on</strong>taminati<strong>on</strong>.<br />

Methods have been published for the de<strong>term</strong>inati<strong>on</strong> of sterigmatocystin in grains and cereals<br />

and have been used for other commodities; however, these methods were found to be<br />

unsatisfactory for this project. The method of van Egm<strong>on</strong>d et al., which is essentially their<br />

earlier method with modificati<strong>on</strong>s, has been developed for the de<strong>term</strong>inati<strong>on</strong> of the<br />

sterigmatocystin in cheese, reportedly with a 5 μ/kg limit of detecti<strong>on</strong>. I tested this method<br />

and c<strong>on</strong>cluded that it was complex and time c<strong>on</strong>suming, and had a relatively high limit of<br />

detecti<strong>on</strong> al<strong>on</strong>g with poor spiked sample recoveries. Experimental data collected during the<br />

method evaluati<strong>on</strong> indicated the potential for the development of a more satisfactory<br />

procedure. The thin layer chromatographic (TLC) method described here resulted.<br />

MATERIALS AND METHODS<br />

Apparatus<br />

a) Chromatographic tube – Plain, 22 x 250 mm<br />

b) TLC plates – precoated, Sil G-25 HR No. 66-14-600-6. Do not activate plates.<br />

c) TLC apparatus – Developing tank with cover for use with 20 x 20 cm glass<br />

plates;spotting template; 10 μL syringe; l<strong>on</strong>gwave 15 watt UV lamp (use with<br />

absorbing eyeglasses) or Chromato-Vue cabinet equipped with <strong>on</strong>e or two 15 watt<br />

561

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