y*******5
发帖数: 7 | 1 不是化学专业的，遇到个LC的问题请教下各位：
实验室用的waters的uplc系统，每天run些vitamin c和b族。昨天一下子出现了负峰，
run的是vitamin c的standard，出现的很sharp的负峰，换了别的柱子，一样的情况，
试着run下别的标准品，有的出现正峰，有的负峰，不管峰是正的还是负的，峰型都很
好。问问各位高手可能是什么原因，怎么解决。
仪器的任何设置都没有变过，因此肯定没有那里接错了或是插反了。在这个问题出现前
run的好好的。
想到可能是mobile phase污染，把所有的溶剂都换成新的，问题还没解决。
正好实验室有个备用的lamp，就换了试试，问题还没解决，尽管想着也不是lamp的问题。
实验室平时run的东西很简单，用到的溶剂也就ACN,METHANOL，水，TFA啥的。
这种情况以前也没出过，大家说说可能是什么原因呢？怎么解决？
多谢！ |
x****o
发帖数: 60 | 2 Depends on where is the negative peak. Close to t0 is normal. Suspect some
air bubble trapped in the detector flow cell (UV or FL). Use pure organic
solvent (IPA) to flush the system. |
y*******5
发帖数: 7 | 3 THe negative peak shows at the same time as the normal run before. The only
difference is the peak is negative instead of positive.
I believe it's not air bubbles.
[ 在 xiaoao (吃了睡,睡了再吃) 的大作中提到: 】 |
A******y
发帖数: 2041 | 4 Someone changed your normalization wavelength. Turn it off and it should
change back to positive peak. The wavelength is 254? |
y*******5
发帖数: 7 | 5 I don't think anyone changed the wavelength. But how/where to change/check
the normalization wavelength? What the normalization wavelength should be? I
just want to double check.
Do you mean "turn off detector"? We already turned off and on many times,
and it didn't help.
The wavelength is 270. But the same situation happened at 254 also.
Thanks very much.
【在 A******y 的大作中提到】
: Someone changed your normalization wavelength. Turn it off and it should
: change back to positive peak. The wavelength is 254?
|
i***l
发帖数: 9994 | 6 turn off the whole system, including the computer, then restart. |
A******y
发帖数: 2041 | 7 Each instrument is different. It is usually called reference wavelength.
Just turn the particular reference wavelength for 270 to off (usually set at
360 nm).
I
【在 y*******5 的大作中提到】
: I don't think anyone changed the wavelength. But how/where to change/check
: the normalization wavelength? What the normalization wavelength should be? I
: just want to double check.
: Do you mean "turn off detector"? We already turned off and on many times,
: and it didn't help.
: The wavelength is 270. But the same situation happened at 254 also.
: Thanks very much.
|
