Method for Detecting Plasticizer in Food

Plasticizers are industrial additives that are often used in the plastics industry as processing aids to increase the elongation and elongation at break of plastics to improve their softness, surface gloss and appearance. There are many kinds of plasticizers, and the application of phthalate esters is the most common, so the plasticizer mainly refers to the phthalate esters (phthalie acid esters, PAEs). Although there is still no evidence that plasticizer directly causes human health damage, it is called “environmental hormone”, which can cause endocrine disorders and affect reproductive development. It has been reported in the literature that it can significantly affect the sperm deformity rate in rats. The European Food Safety Authority stipulates that daily tolerance to di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) is 0.05 and 0.01 mg/kg body weight.

Plasticizers in foods are mainly derived from the plastic packaging materials or utensils that they come into contact with, and some are derived from the polluted external environment. Plasticizers are widely detected in surface water, soil, barley, ganoderma lucidum, bean sprouts, etc. Because plasticizers are easily soluble in organic solvents, edible vegetable oils packaged by plastics are generally considered to be the main source of plasticizers entering the human body, and alcohol that may come into contact with plastic utensils in the production process has also become the focus of attention. There are also potential plasticizer risks in expanded foods, milk powder, biscuits and pastries that need to use oil in raw materials.

Testing Methods for Plasticizer

At present, the detection methods of plasticizer mainly include gas chromatography, liquid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, immunoassay and so on.

• Gas Chromatography and Liquid Chromatography

Phthalate residus in liquor was quickly tested by gas chromatography. The liquor sample was treated by solid phase extraction (SPE), and the residual amount of phthalate in the sample was determined by gas chromatography. The content of phthalate and ethyl phthalate in liquor was determined quickly and accurately by this method. The linear range of phthalic acid methyl ester and ethyl ester was 0.2 - 4.0 mg/L, r = 0.9991 and 0.9992. This method provides the reference for food and drug control.

High performance liquid chromatography (HPLC) analysis method was used to determinate diocthy phthalate (DOP) in the soft drinking. Soft drinking sample with a simple pre-treatment directly inject into the injector. The calibration graph is linear with r = 0.9999 in the range of 0.1935 - 2.9031 mg/L diocthl phthalate standard solution. The limit of detection is 1.15 μg/L. Application of the method of determination of dioctyl phthalate in soft drinking is used. The recovery is between 97.43% and 103.85%; relative standard deviation (RSD%) lower than 0.28%. This method is satisfactory for detecting the plasticizer component dioctyl phthalate in beverage.

In another case, HPLC was used to determinate the two phthalic acid esters, diethyl phthalate (DEP) and dibutyl phthalate (DBP), in edible oil. The sample was extracted by methanol and the extract was purified with florisil column, then identified and quantified by HPLC. The results showed that linearity of response over 2 phthalic acid esters was good from 5.0 - 40 mg/L with correlation coefficients higher than 0.998. the average recoveries was from 82.2% - 90.4% for two compounds at three different spiked levels. The relative standard deviations were in the range of 0.14% - 2.52%. The detection limits of DEP and DBP were 0.1 mg/L and 0.05 mg/L, respectively. This methods is simple, accurate and suitable for the determination of phthalate acid esters in edible oil.

• GC-MS and LC-MS

Conventional gas chromatography and liquid chromatography can only rely on retention time to qualitatively determine the sample, which is easily disturbed by impurities. After the combination with mass spectrometry, the quantitative analysis of the target by the retention time and characteristic ion contrast ratio has obvious advantages. It has become the recommended test method for many targets including plasticizers.

• Enzyme - linked Immunosorbent Assay

An enzyme - linked immunosorbent assay (ELISA) method was used to detect the dibutyl phthalata (DBP) residues in white spirit. The indirect competitive ELISA revealed that the IC₅₀ was 86.5 μg/L, the standard curve range was from 0 - 1.620 μg/L. The detection limit of ELISA kit was 100 μg/L. The range of average recoveries in white spirit ranged from 91.9% - 95.4%, and the coefficients of variation ranged from 7.2% - 9.2%. The cross reactivity with diisobuthl pythalate was 45%, but had cross reactivity of less than 1% with others. This method is sensitive, accurate, convenient, and quick.

• Other Methods

In addition to the above methods, plasticizer testing also includes: ultraviolet spectrophotometry, capillary electrophoresis, raman spectroscopy, infrared spectroscopy, etc.

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