Media migration test

Distribute 200 pL/well of medium, containing test agent or vehicle, into 6-10 replicates/condition of the migration plate. 

Jickells and co-workers (2004) also evaluated MPPO in terms of migration testing. They concluded that MPPO can be used as a test medium to assess transfer from secondary packaging materials. They proposed a test condition of 6 h at 60 °C but suggested that further studies should be carried out to determine whether the proposed test condition is appropriate for a wider range of food/packaging combinations than those that were tested in their study. 

Tests were carried out without preconditioning and with liquid preconditioning in medium mineralized water. Low mineralized synthetic water was used for migration (3 X 72 hours) in all laboratories. Characteristics of preconditioning and migration test waters are given in Table 4.16. 

Tumor Spheroid-Based Migration Assay 1. Appropriate culture medium for the specific tumor cell line(s) under test. 2. 96-well flat-bottomed tissue culture-treated plates. 

C.I. = Migrating cells to test reagent/migrating cells to medium... 

Cells to be tested are grown in a tissue culture dish (not a flask, which would be difficult to scrape) until confluent. Most of the growth medium is removed, and an artificial linear wound is made in the monolayer, by using, e.g. a sterile pipet tip, or a rubber policeman . Care has to be taken to clean all the wounded area from cells, because in case an uneven scraper is used, which leaves behind some attached cells, their presence at the end of the experiment may complicate the interpretation of the results. The plate is then rinsed several times with PBS to remove all the debris, and the test medium (containing dilutions of the supposed migration-... 

In addition to the field experiments, the Cd uptake by F. antipyretica was tested under laboratory conditions. Concentrations of 1.12 mg/100 ml were added to the culture medium (Knop medium, modified) and the accumulation monitored over 10 days. The results are presented in Table 14. The data confirm that F. antipyretica accumulates heavy metals like Cd to a large extent. The enrichment is a time-dependent process, starting with a fast equilibration followed by several days of slower Cd uptake. There is a slow increase of the intracellular Cd content, which is a result of migration from extracellular binding sites into the cell. 

The full procedure, as described above, was applied for OPC (nine preconditioning conditions and six test waters). After experiments with OPC, some experimental eonditions were deleted for tests with HAC and BFC as they did not appear to give additional information. There were dry preconditioning with 1 bar CO2 (D3 and D4) wet preconditioning with medium mineralized water with added CO2 (Wp3 and Wp4) and migration waters with 0.25 mmole/1 CO2 (Wm2 and Wm5). 

Effect of test water alkalinity. The effect of alkalinity appears obvious for all materials when comparing results for soft migration water (20 ppm CaCOs) and medium mineralized migration water (200 ppm CaCOs). pH increase and aluminium leaching were far more significant with soft water than with medium mineralized water. Caleium eoneentration alw s increased (calcium migration from the cement) in soft waters (initial Ca = 8 mg/1) but it decreased or remained unchanged in medium mineralized water (preeipitation of CaCOs or equilibrium). 

Figure 4.20 shows aluminium concentrations after the third migration period for the same material (HAC) tested in two laboratories in 1997 and September 1997 with the same test conditions liqiud preconditioning with medium mineralised water and low mineralized synthetic migration water at pH 8. 

The first step in determining the amount of migration that can be expected is to perform extraction studies. The FDA has formulated extraction test protocols, in which the plastic materials are exposed to food simulants under specified conditions. These protocols have been modified over the years as experience is gained. Extraction is done at elevated temperatures, with agitation, typically over a period of 10 days. Food simulants are used instead of actual foods because it is important to standardize the extraction agent, and also because detection and analysis of migrating compounds is much easier and more reliable if the medium is a simple two-component solution rather than a chemically complex food. 

Water has a typical surface tension of 72mN/m and, as can be seen fi om the above table, all the surfactants tested reduced the surface tension of the s em, and as a result the aqueous medium wets more efficiently. For the silicone surfactants the best results were achieved with product A, a low molecular weight material. Trisiloxane A gives a very low figure that is only improved upon by the fluorosurfactant. The Critical Micelle Concentration (CMC) is the required level of product to initiate the formation of micelles in the bulk of the liquid. Up to this point the surfactant added to die water migrates to the liquid/air interface to form a film which reduces the surface tension. The low CMC for A shows its high packing efficiency at the intoface, in the much lower level required in comparison to the other products. 

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