热重-剑桥滤片捕集-气相色谱/质谱法研究β-胡萝卜素的热解行为

Investigation of Thermal Decomposition Behavior of β-Carotene in Air Atmosphere Using Thermogravimetry-Cambridge Filter Trapping Device-GC/MS

为了研究β-胡萝卜素的热解行为,采用热重/差热分析(TG/DTA),结合自行设计的剑桥滤片捕集装置,研究了空气氛围下β-胡萝卜素44种热解逸出产物相对含量随着温度段的动态变化情况,并推测了β-胡萝卜素的热解机理。在10℃/min的升温速率、400mL/min空气流量下,通过对β-胡萝卜素进行TG/DTA分析,得到其主要热失重区间为200～450℃。按50℃为一次取样间隔,将整个热失重区间划分为5个小的温度段,各个温度段的逸出产物经捕集处理后,依次进气相色谱-质谱(GC/MS)分析。根据各温度段下总离子流色谱图的总峰面积以及实际质量损失占总质量的百分比来验证了剑桥滤片装置的捕集效果。结果表明,该剑桥滤片装置捕集效果明显;β-胡萝卜素的热解产物主要集中在250～300℃、300～350℃两个温度段逸出;热解产物中生成了β-环柠檬醛、二氢猕猴桃内酯、β-紫罗兰酮、β-环氧-紫罗兰酮等一些非常重要的香味物质;44种热解产物的相对含量随着温度段的变化较为显著。

A self-designed Cambridge filter trapping device coupled with thermogravimetry/ differential thermal analysis （TG/DTA） was introduced and applied to study the pyrolysis mechanism of β-carotene and the dynamic change of relative content of 44 evolved products in each temperature range in air. According to the TG/DTA curve drawed at 10 ℃/rain heating rate and 400 mL/min of air flow, main weight loss temperature （MWLT） of β-carotene was gained,which was 200-450 ℃. Then the MWLT was divided into five continuous ranges at the interval of 50 ℃ to study the pyrolysis products of β-carotene after trapping and analysising by gas chromatography-mass spectrometry （GC/MS）. Trapping effect of Cambridge filter device was decided by the total peak area of the total ion chromatograms and the percentage of the actual quality loss to total quality in each temperature range. Results showed that trapping effect of the device was much better. Pyrolysis products of fl carotene were mainly produced in the 250-300 ℃ and 300 350 ℃. Some very important scent subtances such as β-Cyclocitral, 5,6,7,7a tetrahydro 4,4,7a-trimethyl-2 （4 H ）-Benzofuranone, Irisone, 4-（2,2,6-trimethyl-7-oxabicyclo [4. 1.0] hept-1-yl）-3-Buten 2-one and so on was founded. The relative content of the 44 evolved products was significantly changed with temperature range.