气相色谱法测定羟丙基魔芋葡甘露聚糖的摩尔取代度

Determination of the molar substitution of hydroxypropyl konjac glucomannan by gas chromatography

中文关键词:  羟丙基魔芋葡甘露聚糖  气相色谱法  羟丙基  摩尔取代度

英文关键词:hydroxypropyl konjac glucomannan  gas chromatography  hydroxypropyl  molar substitution

中文摘要:

      目的 建立气相色谱法(gas chromatography, GC)测定羟丙基魔芋葡甘露聚糖(hydroxypropyl konjac glucomannan, HP-KGM)的摩尔取代度(molar substitution degree, MS)的方法。方法 首先制备不同MS的HP-KGM样品, 通过傅里叶变换红外光谱(Fourier transform infrared spectroscopy, FTIR)和1H核磁共振(1H nuclear magnetic resonance, 1H NMR)对其进行结构表征, 然后利用GC测定氢碘酸与HP-KGM在高温密封环境下反应所产生的2-碘丙烷, 以推算其羟丙基的MS, 并将所得结果与1H NMR法得到的MS进行比较。结果 FTIR和1H NMR的结果表明, 羟丙基化过程中HP-KGM的原料—KGM所固有的乙酰基已全部脱落, 因此对HP-KGM的MS测定无干扰, 由此所测得的MS与1H NMR法的结果呈线性关系, 单点法和标准曲线法校正系数分别为1.159 (R2=0.9965)和1.164 (R2=0.9965), 无显著性差异(P=0.862>0.05)。结论 本研究所测定的HP-KGM的羟丙氧基含量在7.6%~40.8% (MS 0.16~1.33)之间, 低于美国药典规定的测定羟丙基纤维素中羟丙氧基含量的范围53.4%~80.5% (MS 2.2~7.8), 由此拓宽了GC测定HP-KGM中羟丙基MS的范围, 这对于食品行业的低取代HP-KGM的质量控制具有重要意义。

英文摘要:

      Objective To develop a method for the determination of molar substitution (MS) of hydroxypropyl konjac glucomannan (HP-KGM) by gas chromatography (GC). Methods HP-KGM samples with different MS were firstly prepared, structurally characterized by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR), and then GC method was used to determine the 2-iodopropane produced by the reaction between hydroiodic acid and HP-KGM at high-temperature in sealed condition. The MS of its hydroxypropyl group was calculated, and the obtained results were compared with the MS obtained by 1H NMR method. Results The results of FTIR and 1H NMR indicated that the inherent acetyl group of KGM, the raw material of HP-KGM, had been completely removed during the hydroxypropylation process, thus there was no interference with the MS determination of HP-KGM. The MS results thus obtained showed a linear relationship with those of the 1H NMR method, with correction coefficients of 1.159 (R2=0.9965) and 1.164 (R2=0.9965) for the single point method and standard curve method, respectively, with no significant difference (P=0.862>0.05). Conclusion The hydroxypropoxy content of HP-KGM obtained here ranges from 7.6% to 40.8% (MS 0.16–1.33), which is lower than that ranges from 53.4% to 80.5% (MS 2.2–7.8) specified in the United States Pharmacopoeia for the hydroxypropoxy content in hydroxypropyl cellulose, which broadens the scope of GC method for determining MS in HP-KGM, which is of great significance for the quality control of low substitution HP-KGM applied in the food industry.