快乐
第5楼2008/05/12
楼上的两位朋友,谢谢您们提出宝贵的建议。我是用ASE加速溶剂萃取仪做的,取了10g干玉米,3g硅藻土。用乙腈提取,未过滤就放入零下45度。
玉米的主要成份:每100克玉米含碳水化合物72.2克,蛋白质8.5克。脂肪4.3克,磷120毫克,钙22毫克,铁1.6毫克。还含有维生素E,B1、B2、B6及胡萝卜素、烟酸等。玉米油富含维生素E、维生素A、卵磷脂等,玉米油中的脂肪有棕榈酸、硬脂酸、油酸、亚油酸等,均为机体各组织所必需的营养物质。
请各位高人帮我分析最上层的是什么,最下层的是什么,谢谢大家了。
我在故我思
第9楼2008/05/12
此外,有一篇外文综述是有关前处理的,只是没有全文,已经在文献求助-应助区求助,如果有全文,可以参考一下是否有关冷冻净化方法的描述:
Review trace analysis of pesticide by gas ch romatography
Renévan der Hoff, P iet van Zoonen. 1 J Ch rom atog r A ,
1999, 843: 301-322.
Abstract
The analysis of pesticides is relevant to both food quality and the environment. Many laboratories are occupied with the analysis of pesticides in food, water or soil. Capillary gas chromatography is the technique most widely used in pesticide analysis. In present laboratory practice it serves as a screening method for over 300 pesticides. In this review we describe the role of gas chromatography as an analytical tool in combination with currently used or recently developed sample preparation techniques.
很遗憾,这篇文献中并没有相关的介绍!全文如下附件:
Trace analysis of pesticides by gas chromatography
感谢那位应助的朋友!
我在故我思
第10楼2008/05/13
下面有三篇相关冷冻净化方法的文献摘要:
Low-temperature clean-up method for the determination of pyrethroids in milk using gas chromatography with electron capture detection
Simone Machado Goularta, Maria Eliana L.R. de Queiroz, Antônio Augusto Nevesa and José Humberto de Queiroz
Abstract
This paper describes a new gas-chrormatography with electron capture detection (GC-ECD) method for determination of some pyrethroids in milk samples. The extraction of the pyrethroids was carried out by liquid–liquid extraction with clean-up by precipitation at low temperature, without additional stages for removal of fat interferences. The method was efficient with recoveries of 93.0 ± 0.1% for cipermethrin and 84.0 ± 0.3% for deltamethrin. The quantification limits were 0.75 μg L−1 for both pyrethroids. The method was simple, of easy execution, and used only small quantities of organic solvent. After optimization and validation, the method was used for the determination of residues of the pyrethroids cipermethrin and deltamethrin in milk and in lactea drink commercialized in Viçosa (MG, Brazil). Some samples presented contamination with deltamethrin at levels below the maximum contamination limits established by the FAO.
Talanta
Volume 75, Issue 5, 15 June 2008, Pages 1320-1323