Determination of Fipronil and Fipronil Sulfone in Food Using Purospher^® STAR RP-18 Endcapped Column and UV Detection

Introduction

Fipronil is normally used as a broad spectrum insecticide to treat dogs and cats for fleas and to combat red lice in poultry. Fipronil sulfone is a degradation product of fipronil, and is more toxic to organisms than the parent compound. Fipronil is a phenylpyrazole pesticide and its use with food producing animals is not permitted in the European Union (EU). Fipronil is classified by the World Health Organization (WHO) as moderately hazardous.

This application focusses on HPLC testing of Fipronil and Fipronil sulfone in Food, in the sum of residues. The maximum residue limit designated by the EU for fipronil in eggs and chicken meat is 5 ng/g (0.005 mg/Kg), reported as a sum of the parent compound and the sulfone degradant.

The limit of detection (LOD) is better than 5 ng/g for Fipronil and better than 3 ng/g for Fipronil sulfone, the limit of quantitation (LOQ) is better than 11 ng/g for Fipronil and better than 7 ng/g for Fipronil sulfone, using HPLC-UV detection.

Sample Preparation

The sample was prepared by a Matrix Solid Phase Dispersion (MSPD) technique. Therefore, accurately weigh 5 g of homogenized egg into a mortar. Add 10 g of dry sodium sulphate and 10 g of sea sand and laevigate with a pestle until a dry powder occurs. Transfer the powder into a glass extraction tube, which contains 2 g of sodium sulphate. Extract with 50 mL of cyclohexane/ethyl acetate 1/1 (v/v) (20-30 drops/30 s). Evaporate to dryness with a TurboVap system at bath temperature of 20 °C.

Sample Preparation

Accurately weigh 10 g of noodles into a mortar and laevigate with a pistil. Transfer the homogenized crushed noodles into a beaker, add 50 mL of cyclohexane/ethyl acetate 1/1 (v/v) and stir for 1 h. Filter the suspension through a prepared filter, and evaporate to dryness with a TurboVap system at bath temperature of 20 °C.

Sample Preparation

Mayonnaise must be homogenized with an UltraTurax with 5000 rpm. Accurately weigh 10 g of mayonnaise into a 50 mL extraction tube. Add 10 mL of acetonitrile and shake for 10 minutes at 2250 rpm. Add the content of a Supel QuE non-buffered extraction tube and shake for 1 minute at 2250 rpm. Centrifuge at 5000 rpm for 5 minutes. The supernatant will be used for the clean-up.

Sample Preparation

Chicken meat was partially freezed and chopped. Accurately weigh 10 g of the prepared chicken meat into a 50 mL extraction tube. Add 10 mL of acetonitrile and shake for 10 minutes at 2250 rpm. Add the content of a Supel QuE non-buffered extraction tube and shake for 1 minute at 2250 rpm. Centrifuge at 5000 rpm for 5 minutes. The supernatant will be used for the clean-up.