s********3
发帖数: 40 | 1 前几天面试遇到一个题，觉得自己答的不是很好，贴出答案，求板上高人指出问题。
题目是“Give you a small molecular compound and there is no label on it. How
could you analysis it by HPLC with UV detector? ”然后我问的能用LC-MS么，HM
答的是，it's depends on you,当时就无语了。
我简单的回忆了一下答的内容，欢迎大家指出问题，顺带说一下下次遇到这问题该怎么
答啊。。。
First, I will try my best to collect more information about this compound if
it is allowed, such as, where it is from, what it is used for, is it a
finished products or raw material etc. Typically talk to the end user of
this compound, or the upstream people.
Secondly, I will make clear of the basic physical properties of this
compound, such as solubility, UV absorption profile, and Pka. As for the
solubility, I try to use a series of polar to nonpolar solvents (water,
methanol, acetonitrile or hexane). After the compound dissolved in the
solvents, I will choose the UV wavelength (absorbance at 200-280nm).
Typically, I will first prefer to choose longer wavelength Vs shorter
wavelength to eliminate possible interference. Then decrease the wavelength
step by step to get the apex point of the Uv-profile. After get the peak, I
will use the standard to compare with it.
For most compounds, a C18 column will be initial starting point. And a
combination of water/methanol or water/acetonitrile will be tried as mobile
phase.
Third, if the instrument condition is allowed, I will use LC-MS to analysis
the fragment of the compound. Most of the experiment condition is as the
above situation. As for the LC-MS, negative mode 100-1000m/z ratio, will be
selected as the initial experiment condition. After I get the MS graph, I
will analysis it by referring the library and then use the standards to
valid it.
多谢多谢。 | s**********8
发帖数: 25265 | 2 他问得也是个 2b问题 , dont blame urself
How
HM
if
【在 s********3 的大作中提到】
: 前几天面试遇到一个题，觉得自己答的不是很好，贴出答案，求板上高人指出问题。
: 题目是“Give you a small molecular compound and there is no label on it. How
: could you analysis it by HPLC with UV detector? ”然后我问的能用LC-MS么，HM
: 答的是，it's depends on you,当时就无语了。
: 我简单的回忆了一下答的内容，欢迎大家指出问题，顺带说一下下次遇到这问题该怎么
: 答啊。。。
: First, I will try my best to collect more information about this compound if
: it is allowed, such as, where it is from, what it is used for, is it a
: finished products or raw material etc. Typically talk to the end user of
: this compound, or the upstream people.
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