Adventitious presence

ISF (International Seed Federation) (2001). Motion on Adventitious Presence ofGM Material in non-GM Seeds. ISF position paper, www.worldseed.org. Accessed June 3, 2005. 

The hydroxide ion is usually not sufficiently nucleophilic to reinitiate polymerization and the kinetic chain is broken. Water has an especially negative effect on polymerization, since it is an active chain-transfer agent. For example, C s is approximately 10 in the polymerization of styrene at 25°C with sodium naphthalene [Szwarc, 1960], and the presence of even small concentrations of water can greatly limit the polymer molecular weight and polymerization rate. The adventitious presence of other proton donors may not be as much of a problem. Ethanol has a transfer constant of about 10-3. Its presence in small amounts would not prevent the formation of high polymer because transfer would be slow, although the polymer would not be living. 

Trituration of the crude cw-azide with hexane at ambient temperature caused detonation to occur. Isolation of low molecular weight carbonyl azides should be avoided, or extreme precautions taken. A similar incident with the analogous cyclobutane diazide was reported [1], During use as an intermediate in preparation of the 1,2-diamine, the explosive diazide was never isolated or handled free of solvent [2]. The trans isomer (0.25 mole) was prepared by the latter technique, but as a 45 w/v% solution in toluene, rather than as the recommended 10% solution. When a magnetic spin-bar was introduced, the solution detonated. Initiation may have involved friction from adventitious presence of iron filings adhering to the magnetic bar [3],... 

Although respondents see themselves as less likely to eat food with PMP components than see the potential for adventitious presence, those seeing it as either very or somewhat likely make up a substantial proportion of respondents, with a combined 45% (Figure 12.3-5). At the same time, 38% perceive themselves as able to avoid such foods, responding to the question that they are either somewhat or very unlikely to eat food coming from PMP plants. 

These values are comparable to the values of AH and AS for CO exchange in [(t -Cp)Co(CO)2]. Very similar values are obtained for the H4C5—-CMe2CMe2—C5H4 complex, but in this case the kinetics are complicated by oxidative catalysis involving a 17-electron species [possibly due to the adventitious presence of Cr(III)]. Addition of CO to this species is believed to proceed via slippage rather than formation of a three-electron two-center Cr—CO bond. In the case of [(i -Cp)2Cr(CO)] the 17-electron oxidized species loses CO rapidly and this path does not contribute to the addition kinetics. 

Limitations. A serious limitation of both of the preceding titration techniques is that the adventitious presence of other ionic agents, e.g., poly ions or especially surfactants (as would be the ease in complete formulations), could seriously affect the utility and precision of these methods. 

Jhala, A.J., Raatz, L., Dexter, J.E., Hall, L.M., 2010. Adventitious presence volunteer flax (Unum usitatissimum L.) in herbicide resistant canola (Brassica napus L.). Weed Technol. 24,244-252. 

---