Study On Migration Of Plasticizers From Paper Packaging Inks

Packaging inks contain toxic and hazardous substances migrating into food thereby endangeringhuman health. Plasticizers are indispensible additives in inks. Phthalate plasticizers recently arousedmore and more attention among people due to its food safety issues.In this paper, the migration of plasticizers from paper packaging inks was studiedsystematically. The model of migration from real inks on paper packaging was developed.The kinetic migration of plasticizers in inks to food and food simulants was studied byexperiments. This paper mainly contains the following content.Migration modelingThe mathematical migration model of contaminants from paper packaging inks wasdeveloped based on Fickian diffusion combined with penetration of inks into paper. In thismodel, the printed paper was treated as a two-layer system containing the ink layer and thepaper layer. The initial concentration of the contaminants in paper layer followed the gradientdistribution. Mass transfer coefficient hmand partition coefficient KF,Pat the interface of paperand food were introduced. The analytical solution of the model was obtained by separation ofvariables method. The migration influencing parameter such as the ink penetration depth L1, theinitial concentration of pollutants CP0, diffusion coefficient of pollutants within the paper DP,the mass transfer coefficient, the partition coefficient and paper thickness L2(L3) werediscussed.Migration test of plasticizers from paper packaging inksThe plasticizers investigated in real inks included commonly used dibutyl phthalate (DBP),bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP) and new typeenvironmentally-friendly plasticizer acetyl tributyl citrate (ATBC). Gas chromatographcoupled with flame ionization detector (GC-FID) was used for the determination of ethanolextract of these plasticizers from printed paper, milk powder and Tenax (modifiedpolyphenylene oxide, MPPO) as food simulant. A novel method was developed for the studyof migration of plasticizers to milk powder and Tenax from the printed paper at100,70,50and25℃, respectively and for different contact time ranging from5min at100℃and40daysat25℃. The inks were offset printed which simulated the real situation and has never beenused in migration research. The paper weight, ink initial amount, the temperature and theproperties of the compounds are the factors affecting the actual mass transfer process.The results showed that the recovery rate of the sample pretreatment method rangedbetween71.2and113.4%. This method was environmental friendly and low-cost. GC-FIDdetection for each sample cost13minutes with the separation degree of about1minute. Initialconcentrations of the plasticizers in printed paper samples were detected and the relativestandard deviation of plasticizer concentration was±1~3%, indicating that this printingmethod could be well used to prepare the paper samples. The paper did not provide anappropriate barrier against the migration of the plasticizers from printing inks. The maximummigration of DBP and ATBC reached almost67.8%while that of DEHP and DOP was about6.7%. The contact time, the temperature and the properties of the compounds are the factorsaffecting the real mass transfer. Migration of four plasticizers into Tenax and milk powder were tested under microwavepower of100,250,440,600and900W. Discussed the migration factors and compared withthe results under normal conditions. The results showed that the microwave power and themigration time, the closeness of pollutants and paper, food characteristics and other factorsaffect the migration behavior. Pollutants under microwave heating conditions easier migrationoccurs than conventional heating migration occurs more easily in a short time.Applicability of mathematical modelThe applicability of our migration model was validated. The kinetic migration predicted bysingle layer model simplified from the above model was the same as that predicted by theclassic Crank’s diffusion model considering hm. The generality of our model was furtherdiscussed.Using the experimental data of DBP at50℃,70℃and100℃, hmand DPwere fitted by themodel. The relationship between the logarithm of hm/DPand Kelvin temperature are nealylinear. The migration of DBP with different initial concentration was predicted and wascompared with the experimental data. The prediction efficiency was further investigated forpaper with different weight and different initial inks content. The result showed that predicteddata and experimental data matched well.Because DPcalculated from Piringer model could not reflect the influence of moleculepolarity on migration, suitable hmcould be selected to improve the prediction accuracy of themigration of DEHP, DOP and ATBC.