Evaluation of oxidative stability of canola oils by headspace analysis

Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore an important criterion by which oils are judged for usefulness in various food applications. In this study a method based on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS. Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R ²=0.73) with those measured by conventional methods. Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT.     

固相微萃取/气相色谱-质谱法分析小茴香挥发性成分

考察了萃取样品温度、萃取纤维吸附时间及解吸时间对于固相微萃取的影响,确定了固相微萃取小茴香挥发性成分较佳的实验条件为:萃取样品温度60℃,萃取纤维吸附时间40min,脱附温度250℃,脱附时间5min。用计算机谱库检索结合气相色谱保留指数二维定性方法,从小茴香的固相微萃取/气相色谱-质谱联用分析谱图中,鉴定出反式-茴香脑、顺式-茴香脑、爱草脑、葑酮、p-茴香醛、1,8-桉树脑、樟脑等35种小茴香挥发性成分,总质量分数98·70%。     

多次顶空固相微萃取方法的原理及应用

详细讨论了多次顶空固相微萃取(MHS-SPME)技术的原理和影响因素,并与常用的固相微萃取(SPME)定量校正方法相比较,分析了该方法的优势和缺点。综述了多次顶空固相微萃取在食品、农业领域的应用情况,并对该方法存在的问题和发展前景进行了论述。     

Accurate determination of hexanal in beef bouillons by headspace solid‐phase microextraction gas‐chromatography mass‐spectrometry

Lipid oxidation has great impact on the quality of food products through flavor and taste deterioration, reduction in nutritive value, and potential toxicity of the oxidized food components. Flavor and taste deterioration can be easily perceived and it represents one of the major causes of consumer complaints in the food industry. The deterioration of sensory properties is due to the decomposition products of hydroperoxides that easily isomerize and degrade into volatile compounds. Volatile products are responsible for flavor and taste deterioration. In this study, we present the development of the solid‐phase microextraction gas chromatography‐mass spectrometry (SPME‐GC‐MS) technique to quantify low amounts (μg/g range) of secondary oxidation products, i.e. hexanal. The optimization of SPME parameters is a difficult task because of the possibility of further formation of volatile products during analysis. Different parameters such as type of fiber, exposure time of the fiber to the sample headspace and the optimal temperature of absorption have also been investigated. The complete validation of the method was achieved by the determination of linearity, limits of detection and quantification and repeatability. We demonstrated that the SPME method is a valuable tool for the quantification of low amounts of secondary oxidation products such as hexanal. Therefore, this technique can be used to detect early formation of volatiles.     

改性聚氨酯固相微萃取吸附材料的合成及光谱分析

以羟基硅油、甲苯-2,4-二异氰酸酯（TDI）、聚己二酸乙二醇酯和1,6-己二醇为原料,以辛酸亚锡为催化剂,环己酮为溶剂,合成了有机硅-聚氨酯聚合物固相微萃取吸附材料。采用红外光谱法对聚合产物进行了结构表征。建立了分光光度法测定有机硅-聚氨酯共聚物中游离异氰酸酯基（NCO）含量的定量分析方法,吸光度与异氰酸基含量呈线性关系,相关系数为R2=0.9996。该方法相对标准偏差小于5%,回收率为99.4%～105%。考察了显色剂用量、体系的酸度、显色时间等因素对NCO测定结果的影响。     

馒头挥发物质的固相微萃取条件优化

以总峰面积和峰数为评价指标,研究了以聚二甲基硅氧烷(DVB/CAR/PDMS)为萃取头的固相微萃取(SPME)对馒头挥发物质萃取效果的影响.结果显示:当样品用量为2 g(15 mL样品瓶),萃取温度为60℃,吸附时间为60 m in,解析温度和时间分别为250℃和4 m in时,提取到的挥发物质数量较多,主要挥发物质的萃取效果较好.馒头的挥发物质主要有醇类64.88%、羰基化合物4.29%、苯类3.81%、酯类2.75%、酰基化合物18.11%、杂环类6.14%.     

微萃取原子吸收法检测水中微量铬

采用分散液液微萃取分离技术结合火焰原子吸收法,提出了一种新的环境水样中痕量铬的检测方法。用吡咯烷二硫代氨基甲酸铵做螯合剂,四氯化碳做萃取剂,乙醇做分散剂。选定并优化了萃取的影响参数。这些参数包括萃取剂和分散剂的类型以及它们的体积、萃取时间、酸碱度和螯合剂的用量等等。通过条件优化,Cr（Ⅵ）和总铬富集率分别达到270和259。校准曲线在1～50μg·L^-1的浓度范围内呈线性,Cr（Ⅵ）和总铬的检出限分别为0.12和0.15μg·L^-1,相对标准偏差分别为2.1%和2.7%。（N=5）该法简便快速,用于自来水、井水和河水中铬的形态分析,结果较满意。     

顶空固相微萃取-气相色谱法测定苯胺类化合物

应用自制羟基-二苯并冠醚(OH-DB14C4/OH-TSO)为涂层的固相微萃取探头,采用气相色谱法测定苯胺(A)、间甲苯胺(MT)、N,N-二乙基苯胺(NNDEA)、N-乙基间甲苯胺(NEMT)和3,4-二甲基苯胺(3,4-DMA).并对固相微萃取的最佳条件进行了优化.顶空固相微萃取-气相色谱法的检测限(LOD)为0.17～0.98 ng·ml-1,相对标准偏差(RSD)为3.23%～6.20%,线性范围(LR)为0.11～29 μg·ml-1.对药厂废水的3,4-DMA进行了分析,其回收率为86%～90%.     

气流式微注射器萃取与气相色谱-质谱联用直接分析烟叶中菊酯类农药

将气流式微注射器萃取技术(GP-MSE)与气相色谱-质谱(GC-MS)联用,建立了一种快速、简单的检测烟叶中菊酯类农药的方法,并通过优化萃取条件和加标回收率实验评价了方法的准确性.结果表明,6种菊酯类农药的加标回收率在83.56%~95.87%之间,相对标准偏差在1.3%~7.6%之间,具有很好的回收率与重复性,说明本文方法可用于检测烟叶样品中的菊酯类农药.     

顶空固相微萃取-气相色谱质谱联用分析汉麻叶挥发性成分

采用顶空固相微萃取法结合气相色谱-质谱联用对汉麻叶的挥发性成分进行分析,考察3种不同萃取纤维（DVB/CAR/PDMS,CAR/PDMS,PDMS/DVB）对分析结果的影响,结果表明较佳萃取纤维为CAR/PDMS.从汉麻叶中检出59种挥发性成分,占挥发油总组分的93.18%,其中醛类3种（0.71%）、醇类1种（0.06%）、烃类37种（57.23%）、杂环化合物类3种（0.19%）、萜烯类12种（34.49%）、其他3种（0.50%）.在鉴定出的成分中含量较多的是[1R-（1R＊,4Z,9S＊）]-4,11,11-三甲基-8-亚甲基-二环[7.2.0]4-十一烯（18.81%）、（1α,3α,5α）-1,5-二甲基-3-甲基-2-亚甲基环己烷（18.18%）、α-石竹烯（11.52%）、异柠檬烯（6.78%）等.