Migration Leveling

As stated earlier, mass transport limiting species can be metal ions in some cases. An example is copper in 1-dydroxyethylidene diphosphonic (HEDP) acid solution [10,17,19]. In this case, a salt film (Cu-HEDP) forms on Cu anode surface [20]. Cu ions are the mass transport limiting species, which diffuse and migrate from Cu anode surface through the salt film into the bulk electrolyte solution. 

Migration leveling and diffusion leveling effects expressed in Equations 10.18 and 10.19 are plotted in Fig. 10.10, which shows that both migration 

FIGURE 10.10 Migration leveling and diffusion leveling effects and peak-valley normal electric field difference versus wavelength for a given amplitude of the anode surface profile. 

FIGURE 10.11 Surface profiles (a) mechanically polished Cu surface (short wavelength), very good ECP effect (b) electroplated Cu film (longer wavelength), less ECP effect (c) electroplated Cu film (flat step, infinite wavelength), zero ECP effect. 

The formation of an anodic film (ion-concentrated diffusion layer or salt film) depends on electrolyte and processing conditions. The characteristics of the film are critical to the planarization efficiency of ECP and ECMP. Hence, the analysis, especially in situ analysis of anodic films, is highly valuable. A few techniques can be used for the purpose. 

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Various polymers and latexes ai e used in manufacturing different articles for medical use. Safety measures in using such articles require strict control measures which provide for detecting toxic substances on hygienic standard levels or on the permissible migration level (PML) (mg/dm ). Chromatographic reaction methods ai e used to reveal formaldehyde, phenol, and epichlorhydrin. 

Dopico-Garcia, M.S., Lopez-Vilarino, J.M. and Gonzales-Rodriguez, M.V. (2003). Determination of antioxidant migration levels from low-density polyethylene films into food simulants, J. Chromatogr. A, 1018, 53-62. 

FDA also concluded that establishing a 0.5 pg/kg dietary concentration as the threshold of regulation is appropriate because it corresponds to a migration level that is above the measurement limit for many of the analytical methods used to quantify migrants from food-contact materials. Thus, decisions are usually made based on dietary concentrations that result from measurable migration into food or food-simulating solvents rather than on worst-case estimates of dietary concentration based on the detection limits of the methods used in the analysis. 

Water-based adhesives are used in the production of paper and cardboard food packaging. Migration of adhesive components from such packaging has been assessed. Migration levels into a food simulant (Tenax) were lower than the specific migration limits for plastics which were used to provide a convenient, informal way of assessing the results. Migration to foodstuffs would be expected to be even lower than into the Tenax simulant used, because food will not be in direct contact with the adhesive surfaces. 

LAWSON, G. et al. (1996) Chemical composition and migration level of packaging adhesives. Summary report Polyurethane adhesives (solvent based). MAFF Project No. IC074. 

Relatively high levels for the worst-case migration potential for styrene were also calculated (the SML for styrene is currently under review) and the concentration of styrene in the appropriate foodstuffs was determined. Low levels of styrene were measured but in all cases were less than 5 ppb. Thus despite the high contact temperatures between the foodstuff and the packaging, the relatively high packaging area mass of food ratio and the presence of fat on the food surface, the migration levels observed were low. 

BURCOCRYL JW Is a migrating, leveling agent for basic dyes or baslc/neutral acid blends. Its unique property Is Its ability to move throughout the dyesltes, thereby forcing migration. 

Typically available as a 5 to 20% solution in plasticisers or PVC pellets, it is also a strong skin sensitiser in liquid form. For some applications where the DCOIT is not readily available on the surface (interior, slightly damp applications) this biostabiliser can fail to perform adequately and fails some test protocols because of its very low migration levels. However, in field tests it... 

With low detection limit techniques, the identity, migration levels and accumulation of antioxidants and their degradation products in food, in hquids and in pharmaceutical solutions can be controlled. HPLC or GC-MS offers functional methods together with, e.g., hquid-liquid extraction (LLE). Recently, solid phase extraction (SPE) has been used successfully with lower detection hmits and smaller errors than LLE. SPE is a technique that uses a small amount of solvent and that efficiently concentrates solutions of analytes depending on, e.g., polarity. 

Traces of styrene can affect the quality of food products above certain migration levels. It has been shown that usually over half of the residual styrene in the food contact packaging material migrates within 24 hours, which is the normal shelf life of many food products. The metabolites of styrene are mandelic acid, a known mutagen, and styrene oxide, a known carcinogen. 

Brede C, Fjeldal P, Skjevrak I, Herikstad H. Increased migration levels of bisphenol A from polycarbonate baby bottles after dishwashing, boiling, and brushing. Food Addit Contam 2003 20 684-689. 

Leo LW, Wong KO, Seah HL. Occurrence of residual bisphenol A and its migration levels in polycarbonate baby milk bottles. Singap J Prim Ind 2006 32 106-108. 

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