Rao P, Pattabiraman T N
Department of Biochemistry, Kasturba Medical College, Manipal, India.
Anal Biochem. 1989 Aug 15;181(1):18-22. doi: 10.1016/0003-2697(89)90387-4.
Evidence is provided to show that in the conventional phenol-sulfuric acid reaction procedure, phenol underwent sulfonation in situ and the phenolsulfonic acid formed decreased the color intensity for hydroxymethyl furfural (HMF), furfural, and many hexoses and pentoses tested. A modified method is described to overcome this problem in which phenol was added after the dehydration of carbohydrates by sulfuric acid and after cooling the system. The color intensity around 475-485 nm for different compounds was fairly proportional to the amount of furfural derivatives (absorption at 310-320 nm) formed from the sugars in the modified method unlike in the conventional procedure. The studies also show that for condensation of HMF derivatives with phenol, heat is not necessary. The color intensity in the modified method also increased compared to that in the conventional method. The increase in the modified method compared to that in the conventional method was 6.0-fold for furfural, 9.1-fold for hydroxymethyl furfural, 3.7-fold for fructose, 2.3-fold for xylose, and 2.0-fold for glucose and arabinose. The possible reasons for this differential increase are discussed.
有证据表明，在传统的苯酚-硫酸反应程序中，苯酚会原位发生磺化反应，生成的苯酚磺酸会降低所测试的羟甲基糠醛（HMF）、糠醛以及许多己糖和戊糖的显色强度。本文描述了一种改进方法来克服这一问题，即在通过硫酸使碳水化合物脱水并冷却系统后再加入苯酚。与传统方法不同，在改进方法中，不同化合物在475 - 485 nm处的显色强度与由糖生成的糠醛衍生物（在310 - 320 nm处的吸光度）的量相当成比例。研究还表明，对于HMF衍生物与苯酚的缩合反应，无需加热。与传统方法相比，改进方法中的显色强度也有所增加。与传统方法相比，改进方法中糠醛的显色强度增加了6.0倍，羟甲基糠醛增加了9.1倍，果糖增加了3.7倍，木糖增加了2.3倍，葡萄糖和阿拉伯糖增加了2.0倍。文中讨论了这种差异增加的可能原因。
