poorlittle
第4楼2011/03/23
Direct thermal desorption is only appropriate if {[the desired extraction takes place at a temperature below the decomposition point of other materials in the sample matrix] and [provided the relatively small sample size that (can be measured into a thermal desorption tube) , and (is representative of the sample as a whole)]}
Direct thermal desorption 只在下述情况下适用:
(1) the desired...... matrix; 及
(2) 样本小至能放入thermal desorption tube ……, 但又足以represents the sample as a whole.
or
当the desired...... matrix 及样本小至能放入thermal desorption tube ……但又足以represents the sample as a whole 時, Direct thermal desorption 才适用
.
rock_rock
第6楼2011/03/23
很容易,不要怕长
重新组织一下:
Direct thermal desorption is appropriate
Only if
thedesired extraction takes place at a temperature (what temperature?)
->below the decomposition point of
-> other materials in the sample matrix
and provided (= and if)
-> the relatively small sample size (what sample size?- > that can be measured into a thermal desorption tube) is representativeof the sample as a whole
直接热解析法只有在附合以下两项条件才适合使用:
一.当祈望的提取发生在低于样品混合液中其他物资的分解温度;
二.相对细小的样品体积, 可以量度和放进热脱附管内,同时又能对整个样本有足够代表性
sjbsjbsjb
第7楼2011/03/23
明白了,也就是说想要提取的物质的解析温度应低于基质里面其他物质的分解温度。如果高了,基质分解可能将解析管堵死或者进入下层的管道。体积要小到能放入解析管,能有整体代表性。
实际上还有几个要求的:
Ensure solid materials have a high surface area – powders, granules (particle size <1 mm3), fibers or films.Bulk solids should be ground with a coolant such as solid carbon dioxide before the material is weighed into sample tubes.
• The gas flow path must not be blocked with sample. Thermal desorption is a dynamic process and gas must be allowed to pass through the sample tube unrestricted.
• Ensure that the sample is placed inside the sample tube such that it is well within the heated zone of the thermal desorber used.