Factors influencing color formation

Studies have shown that this reaction is a result of transesterification between PBT and PC. Transesterification is influenced by many factors, including PBT end groups and catalyst residues. While a little copolymer formation is not a bad thing for the performance of the blend, uncontrolled reaction is unacceptable since the same material could never be made twice. Fortunately, methods to control this chemistry were developed. Generally, addition of certain phosphites is used to quench the transesterification and related reactions [45, 46], Since phosphites are also used as antioxidants and color stabilizers, the quencher was often... 

In 1996, the capillary zone electrophoresis (CZE) separation of a model mixture of six anthocyanins was reported using a 150-mM borate buffer at pH 8 (Bridle et al., 1996). It was proposed that the separation was influenced by three factors electro-osmotic flow (EOF), charge/mass ratio, and complex formation with borate. Bridle and Garcia-Viguera (1997) compared HPLC and CZE for the separation of strawberry and elderberry anthocyanins. They used fused-silica capillaries (57 cm X 75 fim i.d.), mn at 25°C with 150 mM sodium borate buffer (pH 8.0). A more concentrated sample (87 times) was needed for equivalent CZE response at pH 8 compared to HPLC at pH 1.8 because of the much smaller sample introduction volume, the shorter detector ceU path length, and the smaller proportion of colored anthocyanin species at pH 8.0. The separation of strawberry anthocyanins by CZE was satisfactory but the separation of elderberry anthocyanins by CZE was marred by the presence of a large baseline hump. The baseline rise may have been caused by interfering compounds in the extract (i.e., colored polymers) which did not affect the... 

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