The linear benzyl chlorine-free poly(4-acetoxystyrene) (PSTO) with low polydispersity ( M w / M n = 1.3) is obtained through anisole quenching of the living polymerization of 4-acetoxystyrene initiated with the St–Cl/SnCl 4 /n-Bu 4 NBr system in CH 2 Cl 2 . The alkylation reaction rate increases with increasing anisole concentration and temperature. With a 4-fold excess of anisole over the initiator, end-chlorine groups are completely capped by anisole in 30 minutes at −15°C through adding extra SnCl 4 prior to the alkylation reaction. In addition, by using 2-methylanisole and 2,6-dimethylanisole as capping agents, it is verified that both para- and ortho-positions substitution of living PSTO cations to the anisole occur during alkylation reactions.
Short-chain fatty acids (SCFAs) were identified as critical markers in the diagnosis of chronic and metabolic diseases, but a sensitive and stable method to determine SCFAs in feces is a challenge for analysts due to the high volatility. Herein, a sensitive and accurate method to determine SCFAs adopting precolumn derivatization coupled with gas chromatography-mass spectrometry (GC-MS) has been developed. Benzyl chloroformate (BCF) was chosen as the reaction reagent and emulsified derivatization was applied to homogenize the reaction system. Higher sensitivity, wider application and satisfactory derivatization efficiency were obtained using the developed method. An excellent method validation showed a good linearity ranging from 0.9947 to 0.9998. At the same time, the intra-day and inter-day precision were achieved in the range of 0.56% to 13.07%. The lower limits of detection of all target analytes varied from 0.1 to 5 pg. The recovery ranged from 80.87% to 119.03%, and storage stability under three different conditions was also determined. This method was also successfully applied to the analysis of SCFAs in mice fecal samples to illustrate the significant differences between normal and type 2 diabetes mellitus mice.
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