Gelatin rate-determining step

Flory and Weaver (1960) have advanced a mechanism for the reversion kinetics, in which they postulate the formation of an intermediate (involving the intramolecular rearrangement of a single gelatin molecule) as the rate-determining step. The intermediate, which may be a helix of the poly-L-proline H-type, is converted rapidly to a three-chain compound helix at a rate sufficiently rapid to have no effect on the over-all rate. The scheme may be represented as follows ... 

The rate-determining step may be either the association of the NOa+ into the inner sphere of the Re or (more likely) the electron-transfer process. The second reaction with NOa is considered to involve an associative equilibrium step with NO+. The monomeric product [ReClsNO] " is an octahedral complex, and exchange studies show that one of the chloride ions is exchanged at a rate 10 times faster than the other four. The technetate ion (TCO4 -) has been shown to disproportionate rapidly in aqueous alkaline media. In the electrochemical reduction of Tc -> Tc " , if gelatine is present in the solution, the reaction ... 

Very few works dealing with the determination of these synthetic colorants in foods have been published. In 2012, Medeiros et al. developed a single-line flow injection system for the simultaneous determination of two pairs of synthetic colorants Tartrazine-Sunset Yellow and Brilliant Blue-Sunset Yellow in several food products (juice drinks, gelatines, and nutrient-enhanced sports drinks), without a previous separation step, by coupling FIA with multiple pulse amperometry (MPA) with a boron-doped electrode [42]. The influence of flow conditions on the MPA response was evaluated by varying the flow rate from 0.45 to 3.5 mL/min, obtaining a maximum electrical current at... 

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