本論文主要是以毛細管電泳(capillary electrophoresis)和基質輔助雷射脫附游離飛行時間質譜儀(MALDI-TOF/MS)技術研究幾丁質和幾丁聚醣的三種衍生化反應，包括去乙醯化反應、乙醯化反應、和酵素降解反應。CE可偵測樣品的平均去乙醯化程度(degree of deacetylation, DDA)及其分佈情形，而 MALDI-TOF/MS則可分析幾丁聚醣產物(chitooligomers)的單體組成及平均DDA大小。利用去乙醯化反應和再乙醯化反應，可以將DDA分佈寬廣且不對稱的幾丁聚醣樣品改質成為DDA分佈窄且對稱的樣品。由幾丁質去乙醯化動態反應的實驗結果顯示，多階段去乙醯化反應不但能增加反應效率，且能備製具高DDA的幾丁聚醣樣品。此外，幾丁聚醣經胃蛋白酶(pepsin)降解後的主要產物為低分子量幾丁聚醣(LMwtC)和幾丁寡糖(chitooligomers)，在鹼性條件下加入適當的甲醇，可有效分離此兩種產物，並分別以CE和MALDI-TOF/MS進行分析。根據隨著反應時間增加所測得兩種產物的產率、平均DDA、和DDA分佈之變化情形顯示，pepsin降解幾丁聚醣的反應效率隨著原始樣品的平均DDA和分子量降低而增加，而且我們發現pepsin有趨向於降解幾丁聚醣長鏈上富含乙醯基區域的現象。 In this thesis capillary electrophoresis (CE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) were employed to study three derivation reactions for chitin and chitosan, including deacetylation, reacetylation, and enzymatic degradation reactions. CE was used to determine the average degree of deacetylation (DDA) and DDA distribution of chitosan sample, while MALDI-TOF/MS was utilized to analyze the monomer compositions and average DDA of chitooligomers. The broad and asymmetric DDA distribution of chitosan sample can be modified to become narrow and symmetric by performing deacetylation and reacetylation reactions. According to the results obtained from the time course deacetylation of chitin, multi-stage deacetylation reaction not only can increase the reaction efficiency but also can produce chitosan with high DDA. In addition, the major products of chitosan degradation by pepsin digest are low molecular weight chitosan (LMwtC) and chitooligomers, which can be separated under basic condition with appropriate methanol concentration and then are subject to CE and MS analysis. Based on the variations of product yields, average DDAs, and DDA distributions measured with increasing reaction time, we found that the efficiency of chitosan degradation by pepsin digest would increase with decreasing average DDA and molecular weight of the chitosan samples. Moreover, pepsin would prefer to cleave the polysaccharide chain on the acetyl group rich domains.