J. zyxwvuts Agric. Food Chem. zyxwvut 1882, 40, 1833-1835 Determination of Bis(2-ethylhexyl) Adipate in Food Products C. Nerin, P. Gancedo,' and J. Cacho Department of Analytical Chemistry, Centro Politecnico Superior de la Universidad de Zaragoza, 50015 Zaragoza, Spain A new method of extraction of DEHA, bis(2-ethylhexyl) adipate, plasticizer from a matrix containing a high amount of fat matter, such as cheese, has been developed. By using an ultrasonic bath and hexane as the extracting solvent, the cleanup step to separate the fat matter before the analysis of DEHA is unnecessary. The method is successfully applied in the study of migration of DEHA to several cheeses. INTRODUCTION The use of poly(viny1 chloride) (PVC) cling film to wrap food has greatly increased due to many advantages, such zyxwvu as flexibility, transparency, and hygienic factors, which enable the consumer to observe the external aspect and the quality of the product, and at the same time it is convenient. These films contain additives such as plasticizers, which are organic compounds (esters of high molecular weight). The plasticizers are used to give flexibility to the film, and when the film is directly in contact with the food, the plasticizer can migrate from the film into the food. The European Community is interested in this field as was shown by the publication of a list containing the substances and monomers which may be used in the manufacture of plastic material (EEC, 1990). There have been migration studies of cling films containing plasticizers such as citrates, sebacates, and phthalates (Castle et al., 1988a,band 1989), with epoxided soya bean oil (Gilbert et al., 1988; Castle et al., 1988a,b) and bis(2-ethylhexyl) adipate (DEHA) (Startin et al., 1987a,b; Castle et al., 1987) being the most commonlyused and also the most frequently studied. There are many different types of cling films on the Spanish market now, but none of them specifies the recommended or not recommended use for wrapping fatty food. Consequently, everybody can buy the cling film and use it to wrap cheese, ham, or other food. Similarly supermarkets use cling films to wrap small pieces of food sold on retail. The DEHA content in these common cling films was analyzed, and a high content of DEHA (22% w/w) was found. The major problem in the analysis of DEHA in foods is the fat which is extracted together with DEHA. In order to avoid this problem the fat has to be separated before injecting the sample into the gas chro- matography. There are several methods which have been reported for the determination of the plasticizers, such as the use described by Shepherd et al. (1981) for the determination of DEHA, which involve acetone/hexane extraction and fat separation by size-exclusion chroma- tography (SEC) and analyzing the plasticizer by gas chromatography (GC). The most recent described by Startin et al. (1987a,b)involvesgas chromatography-mass spectrometry detection. Most of the time the separation procedure used is size-exclusion chromatography. This paper describes a new method, which has been used to analyze cheese samples. The fat interference has been minimized because the sample has not been com- pletely dissolved but only extracted using hexane as extraction agent solvent. The extraction process is carried out using an ultrasonic bath in which the plasticizer is quantitatively extracted without dissolving the sample. EXPERIMENTAL PROCEDURES Materials. The most common films were selected and bought in national supermarkets. Some Spanish cheeses with a fat content between 40 zyxwv % and 50 % were chosen for the study,taking care that they had not previously been in contact with cling film or other plastics. The DEHA standard used for calibrationand tetracosane used as internal standard were from Fluka. A capillarygas chromato- graph (HP 5890) was used with an integrator. An ultrasonic bath was used to extract and prepare the samples. Sample Preparation. To prepare the spike samples, some cheese slices (5 g) of 4-cm X 4-cm size were cut into small pieces of about 1-cm X 1-cm size, and they were placed in a round- bottom flask (A), and an organic solution (1-5 pL) of DEHA (1 mg/mL) in hexane was injected into the cheese sample. The flask was shaken for some minutes until the solvent evaporated. This spiked cheese sample was transferred to another round- bottom flask, and then the recommendedprocedurewas followed. The first round-bottom flask (A) was rinsed with hexane, and the solution obtained was analyzed to determine the content of DEHA which could be deposited on the glass walls. The difference between the amount of DEHA added to the cheese and the amount of DEHA found on the round flask (less than 10% of the amount was found in the first flask in all cases) was the DEHA contained in the cheese samples. Analysis of Cheese. The cheese sample was cut in several pieces of about 6 g with maximum thickness from 0.6 cm to 1.0 cm. All the pieces were transferred to a round flask of 100 mL, and hexane was added until they were covered. The flask was placed in an ultrasonic bath at 30 OC for 15 min. After this period of time the organicextract was decanted and the extraction was repeated again twice under the same conditions. The pieces of cheese were washed with 25 mL of hexane. After extraction this hexane was added to the combined extracte, and the mixture was filtered through 50 g of anhydrous NazSOI, and 1 mL of a tetracosane solution (0.1 mg/mL) used as internal standard was added. The mixture was concentrated in a rotary evaporator to 5 or 25 mL depending on the content of DEHA expected in the cheese. A blank and a spike from another piece of cheese were prepared simultaneously with the sample. The final extract was analyzed by capillary gas chromatography. Analysis of Films. A portion of film (1 dm2) was placed in a round flask, and 20 mL of hexane-containing tetracosane (0.1 mg/mL) used as internal standard was added. The flask was placed in an ultrasonic bath at 30 "C for 1 h. A second extraction was carried out using 10 mL of hexane and keeping the solution in the ultrasonic bath at 30 OC for 15 min. Both extracts were combined, concentrated to 10 mL, and analyzed by GC. This film extraction method was validated with another extraction procedure using CHC13 as extracting agent (Castle et al., 1987). Chromatographic Conditions. A nonpolar capillary column (SPB-1) of 30-m length and 0.25-mm i.d. was used under the 0021-8561/92/1440-1833$03.~0~0 0 1992 Amerlcan Chemlcal Society