Study on the separation of plastic plasticizers by

2022-08-02
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Research on the separation of plastic plasticizers by thin layer chromatography introduction plasticizers are substances that can increase the plasticity of polymer systems when added to polymer systems, and have a great impact on the properties of plastics. Knowing the composition of plastic plasticizer can provide a strong basis for the analysis of plastic, understanding the formula and technology. The separation of plastic plasticizers by thin layer chromatography has been reported [1 ~ 3] The different proportioning systems of ethyl acetate: benzene, ethyl acetate: isooctane, and ethyl ether: hexane are introduced. If the sample is not damaged, it is found that there is tailing phenomenon, and the separation effect is not ideal. On the basis of repeated experiments, it is concluded that the system of V (ethyl acetate) ∶ V (ether) ∶ V (isooctane) =1 ∶ 4 ∶ 15 is the most suitable mobile phase. Phthalate and sebacate plasticizers are effectively separated. The spots are concentrated. The method is simple and easy to use. It can be used in general laboratories

1 experimental part

1.1 instrument and reagent instrument: chromatography cylinder (10 × eight × 15) , oven, capillary tube (self-made), iodine tank (place a small amount of iodine in a sealed glass tank to volatilize iodine to saturation), water bath pot. Reagents used in this experiment: dimethyl phthalate (DMP), dibutyl phthalate (DBP), diisobutyl phthalate (DiBP), dioctyl phthalate (DOP), dibutyl sebacate (DBS), di-n-octyl sebacate (DOS), isooctane, ethyl acetate, ether, tetrahydrofuran, methanol, carboxymethyl 8 The equipment adopts German Siemens S7 ⑵ 00 series PLC to design the control system, and the base cellulose sodium is analytical pure; Silica gel G (Qingdao Ocean Chemical Plant). Six plasticizers were prepared into 20g/l standard solution with ethyl acetate as solvent, and mixed standard solution was prepared

1.2 sample pretreatment cut about 2G of plastic products into small pieces, put them into a beaker, add about 25ml of newly evaporated tetrahydrofuran or other suitable solvent, and place them overnight to completely dissolve the plastic. Add methanol drop by drop with a separating funnel. Stir the solution continuously during the dropping process. When the fine granular sediment that is no longer dissolved begins to appear, speed up the addition of methanol, and add about 200ml of methanol in total. Filter the sediment. A small amount of methanol is continuously used for precipitation, and the obtained filtrate is evaporated and concentrated on the water bath for standby

1.3 the self-made thin-layer plate has a coating area of 15cm according to the proportion of 35ml sodium carboxymethyl cellulose aqueous solution with a mass concentration of 3g/l and 15g silica gel G × A 10cm thin-layer plate with a layer thickness of 0.25mm is placed horizontally at room temperature, dried in the shade, activated at 105 ~ 110 ℃ for 1h, and placed in a dryer for standby

1.4 pre development of thin-layer plate in order to eliminate the interference of impurities, the side development method is adopted, and the mobile phase V (ethyl acetate) ∶ V (ether) ∶ V (isooctane) = 1 ∶ 4 ∶ 15 is used for pre development, so that the impurities migrate to one side of the thin-layer plate and are taken out for drying

1.5 development and detection: spot the sample on the pre developed thin-layer plate, and use the developing agent V (ethyl acetate) ∶ V (ether) ∶ V (isooctane) = 1:4:15 to develop upward, with a span of 12cm Take out the thin-layer plate, carefully dry the solvent with a blower and place it in an iodine tank for about 3min, showing spots

2 results and discussion

2.1 optimization of separation conditions according to literature [1], three mobile phase systems, V (ethyl acetate) ∶ V (benzene) =1:19 (Ⅰ), V (ethyl acetate) ∶ V (isooctane) =1:9 (Ⅱ), V (ether) ∶ V (hexane) =4:1 (Ⅲ), were tested. It was found that the ratio of ethyl acetate to benzene in system Ⅰ could separate more plasticizers, and the separation effect of systems Ⅱ and Ⅲ was poor. Considering that phthalic acid esters and decanoates to be separated are weakly polar substances, the system V (ethyl acetate) ∶ V (benzene) ∶ V (isooctane) =1:2:7 (Ⅳ), V (ethyl acetate) ∶ V (ether) ∶ V (benzene) =1:1:18 (Ⅴ) was tested with ethyl acetate as the matrix, adding the third phase to change the ratio, and adjusting the polarity of the solvent system. See table 1 It can be seen that the polarity of IV system solvent is moderate, and the separation effect of phthalic acid esters is good; Ⅴ system uses ether dipolar reagent, which has better affinity for plasticizers, but its separation effect for sebacate is not as good as the previous ones. Considering the polarity, toxicity and price of Ⅳ and Ⅴ systems, the separation effect of V (ethyl acetate) ∶ V (ether) ∶ V (isooctane) =1 ∶ 4 ∶ 15 (Ⅵ) is the best

2.2 sample determination two samples of blue PVC soft plastic and colorless low-temperature resistant soft plastic were processed into concentrated solution, and 2-3 plasticizers were obtained by thin-layer separation with mobile phase VI, as shown in figure 1 Following the historical tradition, exploring the authenticity of materials, embracing the unknown technology and advocating the true spirit of ingenuity, the blue PVC soft plastic plasticizers are DBP and dop The colorless and low temperature resistant plasticizers are DBP, DOP, dos Conclusion under the condition of the best flow matching ratio, the six plasticizers of phthalate esters and sebacate esters can be clearly separated on the conventional silica gel plate by pre expanding the impurities to one side. The method is simple and can form a win-win cooperation mode with other enterprises. Thanks: heguangce and yeyunyun, graduates of industrial analysis Grade 99, have participated in some experimental work. I would like to express my heartfelt thanks

information source: China plastic additives

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