Nowadays, toys are closely related to children's life, but harmful substances such as heavy metals, plasticizers, organic compounds, flame retardants and polycyclic aromatic hydrocarbons in toys have a great impact on children's health. Among them, plasticizers are added to the PVC (polyvinyl chloride, or vinyl) toys to increase its elasticity and toughness, whose main ingredients are phthalate esters (PAEs) such as Dibutyl phthalate (DEHP), butyl phthalate (DBP), butyl benzyl phthalate (BBP), diisonyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl phthalate (DNOP) and so on.

Fig.1 shows the distribution of phthalates and other compounds in the toys, which is studied by Ruth Stringer¹. However, these phthalates in soft PVC products are not tightly bound to the plastic, but are present as mobile components of the plastic matrix, which can be released from soft PVC by surface contact, especially where mechanical pressure is applied (e.g. during chewing of a PVC teether). Therefore, exposure to phthalates is dangerous, which can lead to different degrees of damage to the liver, reproductive system and endocrine system, especially for the children at an early and sensitive stage of their development^2-3. In the light of these concerns, it seems very urgent to quickly screen the plasticizer in the toys. At present, there are many methods to detect PAEs plasticizers in toys, each of which has its advantages and disadvantages, including gas chromatography⁴, gas-mass spectrometry⁵, liquid chromatography6, and liquid chromatography-mass spectrometry^7-8.

Fig. 1 Frequency distribution for phthalates and other organic compounds in PVC toys. (% indicates proportion of all PVC toys in which each compound was found¹.)

Gas chromatography or gas-mass spectrometry

In general, chromatography consists of mobile and stationary phases. The molecules have different interactions with the stationary phases. Therefore, different types of molecules can be separated from each other as they move over the stationary phases. There are many gas chromatographic methods available to determine the plasticizers in toys. Before the detection of PAEs plasticizers by GC, we first need to use some chemical solvents such as dichloromethane, trichloromethane, or n-hexane to extract the plasticizers from the toys, with which the typical representative methods are accelerated solvent extraction (ASE), soxhlet extraction (SE), ultrasound-assisted extraction (UAE). Once the extracted sample completes the process of purification and volume determination, it can be qualitatively or quantitatively determined by GC or GC-MC. For example, Huang Y H⁹ used the technology of gas chromatography-mass spectrometry to simultaneously determine 22 phthalate ester plasticizers in plastics toys. The results show that the correlation coefficients are over 0.999, the detection limits are 1.28~128.91 mg/kg, the average recovery rates are 70.83%~107.95%, and the relative standard deviations are 3.61%~9.79%.

Liquid chromatography or liquid chromatography - mass spectrometry

The detector of gas chromatographic is easy to be polluted by other organic matters, and the sensitivity varies with great fluctuation. In addition, the boiling point of phthalate is too high that higher gasification temperature and column temperature are needed. In contrast, liquid chromatography has its special advantages. The accuracy degree is higher and the detection limit is lower, which can meet most of the testing requirements of PAEs in plastics toys. For example, Xu jing¹⁰ established an ultra-high performance liquid chromatography method that can simultaneously determine 8 phthalates in plastic toys. He used ethanol as the solvent, and the samples were dehydrated with anhydrous sodium sulfate in the pretreatment process to reduce impurities. Eight kinds of phthalic acid esters in plastic toys were extracted by ultrasonic extraction. The recovery rate of this method is 93.6%~98.8%, RSD is 0.5%~2.3%, and the detection limit is 0.16~0.76 mg. Meng X S¹¹ established an analytical method for the rapid screening and quantitative detection of fifteen phthalates(PAEs) plasticizers in plastic toys by ultra-performance liquid chromatography-hybrid quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS)．The experimental results demonstrated that a favorable mass accuracy less than 3 ppm was obtained for fifteen PAEs，and good linearities (R² is greater than 0.996) were observed in the respective concentration ranges. All in all, the technology of LC or LC-MS is more sensitive, rapid and accurate to detect the PAEs plasticizers in toys.

References

• Ruth S, Iryna L, David S. (2000) ‘Concentrations of phthalate esters and identification of other additives in PVC children’s toys’. Environmental Science and Pollution Research, 7(1): 27~36.

• Akira T, Akiyo M. (1987) Tsutomu Y. ‘Biochemical studies on phthalic esters III. Metabolism of dibutyl phthalate（DBP）in animals’. Toxicology, 9(1-2): 109~123.

• Akira T, Akiyo M, Tsutomu Y. (1975) ‘Biochemical studies on phthalic esters I. Elimination distribution and metabolism of di – (2-ethylhexyl）phthalate in rats’. Toxicology, 4(2):253~264.

• Wu L L, Shen B, Ying X H, Kong F D. (2012) ‘Determination of tricresyl phosphate plasticizer in polyvinylchloride plastic by precipitation separation-gas chromatographic method’, Chin. J. Anal. Chem, 40(4): 617~621.

• Liu F J, Xian Y P, Guo X D, Weng Y B, Peng Y, Chen J W, Lu Y J．(2014) ‘Determination of twenty phthalic acid esters in waterborne wall coatings by gas chromatography-mass spectrometry’, J. Instrum. Anal, 33(4): 437~441．

• Ma Y L, Chen L X, Ding Y J, Ming Y F, Li J H. (2013) ‘Simultaneous determination of four phthalate esters in water samples using ultrasound-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography’ Chin. J. Chromatogr, 31(2): 155~161.

• Yan J, Bao F W, Niu L N, Liu H, Su G S． (2015) ‘Determination of phthalate acid esters in water-borne adhesives for cigarette by UPLC-MS/MS’, J. Instrum. Anal, 34(2): 134~140．

• Zhang H J, Hu X J, Lin S B. (2014) ‘Determination of phthalate acid esters in waters by ultra pressure liquid chromatography - triple quadrupole mass spectrometer’, Chin. J. Anal. Chem, 42(9): 1281~1287．

• Huang Y H, (2011) ‘Simultaneous Determination of 22 Phthalate Ester Plasticizers in Plastics Toys by Gas Chromatography-Mass Spectrometry’ Plastics Science and Technology, 39(1): 94~97.

• Xu J, Wang H Y, Zhu J B. (2010) ‘simultaneous determination of phthalic acid esters in plastic toys by UPLC’ 19(2): 24~25.

• Meng X S, Lian X H. (2018) ‘Screening of phthalates plasticizers in plastic toys by ultra-performance liquid chromatography - hybrid quadrupole time-of-flight mass spectrometry’, Journal of Instrumental Analysis, 37(2): 165~173.